Co-reporter:Noelia Rubio, Heather Au, Hannah S. Leese, Sheng Hu, Adam J. Clancy, and Milo S. P. Shaffer
Macromolecules September 26, 2017 Volume 50(Issue 18) pp:7070-7070
Publication Date(Web):September 14, 2017
DOI:10.1021/acs.macromol.7b01047
Graphene nanoplatelets (GNP) were exfoliated using a nondestructive chemical reduction method and subsequently decorated with polymers using two different approaches: grafting from and grafting to. Poly(methyl methacrylate) (PMMA) with varying molecular weights was covalently attached to the GNP layers using both methods. The grafting ratios were higher (44.6% to 126.5%) for the grafting from approach compared to the grafting to approach (12.6% to 20.3%). The products were characterized using thermogravimetric analysis–mass spectrometry (TGA-MS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The grafting from products showed an increase in the grafting ratio and dispersibility in acetone with increasing monomer supply; on the other hand, due to steric effects, the grafting to products showed lower absolute grafting ratios and a decreasing trend with increasing polymer molecular weight. The excellent dispersibility of the grafting from functionalized graphene, 900 μg/mL in acetone, indicates an increased compatibility with the solvent and the potential to increase graphene reinforcement performance in nanocomposite applications.
Co-reporter:Sebastian D. Pike, Edward R. White, Anna Regoutz, Nicholas Sammy, David J. Payne, Charlotte K. Williams, and Milo S. P. Shaffer
ACS Nano March 28, 2017 Volume 11(Issue 3) pp:2714-2714
Publication Date(Web):March 13, 2017
DOI:10.1021/acsnano.6b07694
Exceptionally small and well-defined copper (Cu) and cuprite (Cu2O) nanoparticles (NPs) are synthesized by the reaction of mesitylcopper(I) with either H2 or air, respectively. In the presence of substoichiometric quantities of ligands, namely, stearic or di(octyl)phosphinic acid (0.1–0.2 equiv vs Cu), ultrasmall nanoparticles are prepared with diameters as low as ∼2 nm, soluble in a range of solvents. The solutions of Cu NPs undergo quantitative oxidation, on exposure to air, to form Cu2O NPs. The Cu2O NPs can be reduced back to Cu(0) NPs using accessible temperatures and low pressures of hydrogen (135 °C, 3 bar H2). This striking reversible redox cycling of the discrete, solubilized Cu/Cu(I) colloids was successfully repeated over 10 cycles, representing 19 separate reactions. The ligands influence the evolution of both composition and size of the nanoparticles, during synthesis and redox cycling, as explored in detail using vacuum-transfer aberration-corrected transmission electron microscopy, X-ray photoelectron spectroscopy, and visible spectroscopy.Keywords: copper nanoparticles; copper(I) oxide nanoparticles; organo-copper(I); redox switching; transmission electron microscopy; ultrasmall nanoparticles;
Co-reporter:Andrés García-Trenco, Edward R. White, Anna Regoutz, David J. Payne, Milo S. P. Shaffer, and Charlotte K. Williams
ACS Catalysis February 3, 2017 Volume 7(Issue 2) pp:1186-1186
Publication Date(Web):January 10, 2017
DOI:10.1021/acscatal.6b02928
Colloidal Pd2Ga-based catalysts are shown to catalyze efficiently the hydrogenation of CO2 to methanol. The catalysts are produced by the simple thermal decomposition of Pd(II) acetate in the presence of Ga(III) stearate, which leads to Pd0 nanoparticles (ca. 3 nm), and the subsequent Pd-mediated reduction of Ga(III) species at temperatures ranging from 210 to 290 °C. The resulting colloidal Pd2Ga-based catalysts are applied in the liquid-phase hydrogenation of carbon dioxide to methanol at high pressure (50 bar). The intrinsic activity is around 2-fold higher than that obtained for the commercial Cu-ZnO-Al2O3 (60.3 and 37.2 × 10–9 molMeOH m–2 s–1), respectively, and 4-fold higher on a Cu or Pd molar basis (3330 and 910 μmol mmolPd or Cu–1 h–1). Detailed characterization data (HR-TEM, STEM/EDX, XPS, and XRD) indicate that the catalyst contains Pd2Ga nanoparticles, of average diameters 5–6 nm, associated with a network of amorphous Ga2O3 species. The proportion of this Ga2O3 phase can be easily tuned by adjusting the molar ratio of the Pd:Ga precursors. A good correlation was found between the intrinsic activity and the content of Ga2O3 surrounding the Pd2Ga nanoparticles (XPS), suggesting that methanol is formed by a bifunctional mechanism involving both phases. The increase in the reaction temperature (190–240 °C) leads to a gradual decrease in methanol selectivity from 60 to 40%, while an optimum methanol production rate was found at 210 °C. Interestingly, unlike the conventional Cu-ZnO-Al2O3, which experienced approximately 50% activity loss over 25 h time on stream, the Pd2Ga-based catalysts maintain activity over this time frame. Indeed, characterization of the Pd/Ga mixture postcatalysis revealed no ripening of the nanoparticles or changes in the phases initially present.Keywords: bimetallic PdGa; CO2 hydrogenation; colloidal nanoparticles; methanol synthesis; nanocatalysts; Pd2Ga alloy;
Co-reporter:Sebastian D. Pike;Andrés García-Trenco;Edward R. White;Alice H. M. Leung;Jonathan Weiner;Charlotte K. Williams
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 18) pp:4233-4233
Publication Date(Web):2017/09/18
DOI:10.1039/C7CY90083J
Correction for ‘Colloidal Cu/ZnO catalysts for the hydrogenation of carbon dioxide to methanol: investigating catalyst preparation and ligand effects’ by Sebastian D. Pike et al., Catal. Sci. Technol., 2017, DOI: 10.1039/c7cy01191a.
Co-reporter:Sebastian D. Pike;Andrés García-Trenco;Edward R. White;Alice H. M. Leung;Jonathan Weiner;Charlotte K. Williams
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 17) pp:3842-3850
Publication Date(Web):2017/08/29
DOI:10.1039/C7CY01191A
The production of methanol from CO2 hydrogenation is a promising potential route to a renewable liquid fuel and renewable energy vector. Herein, three distinct routes to make colloidal catalysts based on mixtures of Cu(0) and ZnO nanoparticles (NPs) and using low-temperature organometallic procedures are reported. The colloids are surface coordinated by a phosphinate ligand: dioctylphosphinate ([DOPA]−), which delivers a high solubility in organic solvents. Further, the synthetic routes allow fine control of the ZnO:Cu and ligand loadings. The catalysts are prepared by mixing small NPs (2 nm) of either Cu(0) or air-stable Cu2O NPs with ZnO NPs (3 nm), or by the synthesis of Cu(0) in presence of ZnO NPs (ZnO: 2 nm, Cu: 6 nm). The resulting colloidal catalysts are applied in the liquid phase hydrogenation of CO2 to methanol (210 °C, 50 bar, 3 : 1 molar ratio of CO2 : H2). The catalysts typically exhibit 3 times higher rates when compared to a heterogeneous Cu–ZnO–Al2O3 commercial catalyst (21 vs. 7 mmolMeOH gCuZnO−1 h−1). The characterisation of the post-catalysis colloids show clear Cu/ZnO interfaces (HR-TEM), which are formed under reducing conditions, as well as differences in the Cu(0) NP size (from 3 to 7 nm) and nanoscale restructuring of the catalysts. The combination of characterisation and catalytic results indicate that the activity is mostly dictated by the Cu(0) particle size and ligand loading. Smaller Cu(0) NPs exhibited lower turnover frequency (TOF) values, whereas higher ligand loadings ([DOPA]−:(Cu + Zn) of 0.2–1.1) lead to smaller Cu(0) NPs and reduce the formation of Cu/ZnO interfaces. UV-vis spectroscopy reveals that the Cu(0) NPs are more stable to oxidation under air after catalysis than beforehand, potentially due to migration of ZnO onto the Cu surface whilst under catalytic conditions.
Co-reporter:A. J. Clancy;D. B. Anthony;S. J. Fisher;H. S. Leese;C. S. Roberts;M. S. P. Shaffer
Nanoscale (2009-Present) 2017 vol. 9(Issue 25) pp:8764-8773
Publication Date(Web):2017/06/29
DOI:10.1039/C7NR00734E
Long single-walled carbon nanotubes, with lengths >10 μm, can be spontaneously dissolved by stirring in a sodium naphthalide N,N-dimethylacetamide solution, yielding solutions of individualised nanotubide ions at concentrations up to 0.74 mg mL−1. This process was directly compared to ultrasonication and found to be less damaging while maintaining greater intrinsic length, with increased individualisation, yield, and concentration. Nanotubide solutions were spun into fibres using a new reactive coagulation process, which covalently grafts a poly(vinyl chloride) matrix to the nanotubes directly at the point of fibre formation. The grafting process insulated the nanotubes electrically, significantly enhancing the dielectric constant to 340% of the bulk polymer. For comparison, samples were prepared using both Supergrowth nanotubes and conventional shorter commercial single-walled carbon nanotubes. The resulting nanocomposites showed similar, high loadings (ca. 20 wt%), but the fibres formed with Supergrowth nanotubes showed significantly greater failure strain (up to ∼25%), and hence more than double the toughness (30.8 MJ m−3), compared to composites containing typical ∼1 μm SWCNTs.
Co-reporter:Adam J. Clancy, James M. Serginson, Jake L. Greenfield, Milo S.P. Shaffer
Polymer 2017 Volume 133(Volume 133) pp:
Publication Date(Web):20 December 2017
DOI:10.1016/j.polymer.2017.10.047
•Amine mono-terminated poly(vinyl acetate) with controllable PDI synthesised.•Polymers grafted onto single-walled carbon nanotubes using 3 different reactions.•Bromide functionalisation provides highest polymer content.•Intermediate polymer weights (∼5 kDa) required to maximise nanotube dipsersibility.The covalent grafting of polymers to single-walled carbon nanotubes (SWCNTs) is widely used to improve solvent compatibility, as well as composite and functional performance. Here, three different graft-to strategies are directly compared, using azide, diazonium, and bromide terminated polymers, over four different molecular weights (oligomeric to 10 kDa) using specifically synthesized low polydispersity, end-group controlled poly(vinyl acetate) (PVAc) prepared by polymerisation using a bespoke protected-amine RAFT agent. Coupling of the bromo-polymer to reduced SWCNTs led to higher degrees of functionalisation (grafting ratios up to 68.9%) than the azide and diazonium grafting reactions, attributed to better initial dispersion of the pre-grafted SWCNTs. The use of higher molecular weight polymers led to a decrease in the total weight of polymer grafted, as the increase in per-polymer weight is more than offset by steric occlusion on the SWCNT surface. For these graft-to reactions, the dispersibility of grafted SWCNTs was found to depend most strongly on the polymer molecular weight, not total weight of grafted polymer or grafting chemistry, with an intermediate Mn∼5757 PVAc giving the best dispersibilities, at up to 118 mg L−1.Download high-res image (261KB)Download full-size image
Co-reporter:Sheng Hu;Zachary P. L. Laker;Hannah S. Leese;Noelia Rubio;Martina De Marco;Heather Au;Mark S. Skilbeck;Neil R. Wilson
Chemical Science (2010-Present) 2017 vol. 8(Issue 9) pp:6149-6154
Publication Date(Web):2017/08/21
DOI:10.1039/C6SC05603B
Graphene and graphene nanoplatelets can be functionalised via a gas-phase thermochemical method; the approach is versatile, readily scalable, and avoids the introduction of additional defects by exploiting existing sites. Direct TEM imaging confirmed covalent modification of single layer graphene, without damaging the connectivity of the lattice, as supported by Raman spectrometry and AFM nano-indentation measurements of mechanical stiffness. The grafting methodology can also be applied to commercially-available bulk graphene nanoplatelets, as illustrated by the preparation of anionic, cationic, and non-ionic derivatives. Successful bulk functionalisation is evidenced by TGA, Raman, and XPS, as well as in dramatic changes in aqueous dispersability. Thermochemical functionalisation thus provides a facile approach to modify both graphene monolayers, and a wide range of graphene-related nanocarbons, using variants of simple CVD equipment.
Co-reporter:Martina De Marco, Robert Menzel, Salem M. Bawaked, Mohamed Mokhtar, Abdullah Y. Obaid, Sulaiman N. Basahel, Milo S.P. Shaffer
Carbon 2017 Volume 123(Volume 123) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.carbon.2017.07.094
Graphene oxide (GO) and multi-walled carbon nanotubes (MWCNT) have been previously used independently as active supports for layered double hydroxides (LDH), and found to enhance the intrinsic CO2 sorption capacity. However, the long-term stability of the materials subjected to temperature-swing adsorption (TSA) cycles still requires improvement. In this contribution, GO and MWCNT are hybridized to produce mixed substrates with improved surface area, and compatibility for the subsequent deposition of LDH platelets, compared to either phase alone. The incorporation of a robust and thoroughly hybridized carbon network considerably enhances the thermal stability of activated, promoted LDH over twenty cycles of gas adsorption-desorption (96% of retention of the initial sorption capacity at the 20th cycle), dramatically reducing the sintering previously observed when either GO or MWCNT were added separately. Detailed characterization of the morphology of the supported LDH, at several stages of the multicycle adsorption process, shows that the initial morphology of the adsorbents is more strongly retained when supported on the robust hybrid GO/MWCNT network; the CO2 adsorption performance correlates closely with the specific surface area of the adsorbents, with both maximized at small loadings of a 1:1 ratio GO:MWCNT substrate.Download high-res image (428KB)Download full-size image
Co-reporter:Stephen A. Hodge;David J. Buckley;Hin Chun Yau;Neal T. Skipper;Christopher A. Howard
Nanoscale (2009-Present) 2017 vol. 9(Issue 9) pp:3150-3158
Publication Date(Web):2017/03/02
DOI:10.1039/C6NR10004J
Chemical and electrochemical reduction methods allow the dispersion, processing, and/or functionalization of discrete sp2-hybridised nanocarbons, including fullerenes, nanotubes and graphenes. Electron transfer to the nanocarbon raises the Fermi energy, creating nanocarbon anions and thereby activating an array of possible covalent reactions. The Fermi level may then be partially or fully lowered by intended functionalization reactions, but in general, techniques are required to remove excess charge without inadvertent covalent reactions that potentially degrade the nanocarbon properties of interest. Here, simple and effective chemical discharging routes are demonstrated for graphenide polyelectrolytes and are expected to apply to other systems, particularly nanotubides. The discharging process is inherently linked to the reduction potentials of such chemical discharging agents and the unusual fundamental chemistry of charged nanocarbons.
Co-reporter:Mani Diba, Derrick W.H. Fam, Aldo R. Boccaccini, Milo S.P. Shaffer
Progress in Materials Science 2016 Volume 82() pp:83-117
Publication Date(Web):September 2016
DOI:10.1016/j.pmatsci.2016.03.002
The Electrophoretic Deposition (EPD) of graphene-related materials (GRMs) is an attractive strategy for a wide range of applications. This review paper provides an overview of the fundamentals and specific technical aspects of this approach, highlighting its advantages and limitations, in particular considering the issues that arise specifically from the behaviour and dimensionality of GRMs. Since obtaining a stable dispersion of charged particles is a pre-requisite for successful EPD, the strategies for suspending GRMs in different media are discussed, along with the resulting influence on the deposited film. Most importantly, the kinetics involved in the EPD of GRMs and the factors that cause deviation from linearity in Hamaker’s Law are reviewed. Side reactions often influence both the efficiency of deposition and the nature of the deposited material; examples include the reduction of graphene oxide (GO) and related materials, as well as the decomposition of the suspension medium at high potentials. The microstructural characteristics of GRM deposits, including their degree of reduction and orientation, strongly influence their performance in their intended function. These factors will also determine, to a large extent, the commercial potential of this technique for applications involving GRMs, and are therefore discussed here.
Co-reporter:Hannah S. Leese, Lata Govada, Emmanuel Saridakis, Sahir Khurshid, Robert Menzel, Takuya Morishita, Adam J. Clancy, Edward. R. White, Naomi E. Chayen and Milo S. P. Shaffer
Chemical Science 2016 vol. 7(Issue 4) pp:2916-2923
Publication Date(Web):29 Jan 2016
DOI:10.1039/C5SC03595C
A range of carbon nanomaterials, with varying dimensionality, were dispersed by a non-damaging and versatile chemical reduction route, and subsequently grafted by reaction with methoxy polyethylene glycol (mPEG) monobromides. The use of carbon nanomaterials with different geometries provides both a systematic comparison of surface modification chemistry and the opportunity to study factors affecting specific applications. Multi-walled carbon nanotubes, single-walled carbon nanotubes, graphite nanoplatelets, exfoliated few layer graphite and carbon black were functionalized with mPEG-Br, yielding grafting ratios relative to the nanocarbon framework between ca. 7 and 135 wt%; the products were characterised by Raman spectroscopy, TGA-MS, and electron microscopy. The functionalized materials were tested as nucleants by subjecting them to rigorous protein crystallization studies. Sparsely functionalized flat sheet geometries proved exceptionally effective at inducing crystallization of six proteins. This new class of nucleant, based on PEG grafted graphene-related materials, can be widely applied to promote the growth of 3D crystals suitable for X-ray crystallography. The association of the protein ferritin with functionalized exfoliated few layer graphite was directly visualized by transmission electron microscopy, illustrating the formation of ordered clusters of protein molecules critical to successful nucleation.
Co-reporter:Martina De Marco, Foivos Markoulidis, Robert Menzel, Salem M. Bawaked, Mohamed Mokhtar, Shaeel A. Al-Thabaiti, Sulaiman N. Basahel and Milo S. P. Shaffer
Journal of Materials Chemistry A 2016 vol. 4(Issue 15) pp:5385-5389
Publication Date(Web):03 Mar 2016
DOI:10.1039/C5TA10311H
Single-walled carbon nanotube (SWCNT) anions can be cross-linked by a dielectrophile to form covalent, carbon-bonded organogels. Freeze-drying produces cryogels with low density (2.3 mg cm−3), high surface area (766 m2 g−1), and high conductivity (9.4 S m−1), showing promise as supercapacitor electrodes. Counterion concentration controls debundling, grafting ratio, as well as all the resulting properties.
Co-reporter:Won Jun Lee, Adam J. Clancy, Eero Kontturi, Alexander Bismarck, and Milo S. P. Shaffer
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 46) pp:31500
Publication Date(Web):November 4, 2016
DOI:10.1021/acsami.6b11578
The mechanical properties of rodlike cellulose nanocrystals (CNCs) suggest great potential as bioderived reinforcement in (nano)composites. Poly(vinyl alcohol) (PVOH) is a useful industrial material and very compatible with CNC chemistry. High performance CNC/PVOH composite fibers were produced coaxial coagulation spinning, followed by hot-drawing. We showed that CNCs increase the alignment and crystallinity of PVOH, as well as providing direct reinforcement, leading to enhanced fiber strength and stiffness. At 40 wt % CNC loading, the strength and stiffness reached 880 MPa and 29.9 GPa, exceeding the properties of most other nanocellulose based composite fibers previously reported.Keywords: cellulose nanocrystal; composite; fiber; nanocellulose; poly vinyl alcohol
Co-reporter:Mustafa K. Bayazit, Stephen A. Hodge, Adam J. Clancy, Robert Menzel, Shu Chen and Milo S. P. Shaffer
Chemical Communications 2016 vol. 52(Issue 9) pp:1934-1937
Publication Date(Web):10 Dec 2015
DOI:10.1039/C5CC08726K
Gold nanoparticles (AuNPs) can be evenly deposited on single-walled carbon nanotubes (SWCNTs) via the reduction of the highly stable complex, chloro(triphenylphosphine) gold(I), with SWCNT anions (‘nanotubides’). This methodology highlights the unusual chemistry of nanotubides and provides a blueprint for the generation of many other hybrid nanomaterials.
Co-reporter:Adam J. Clancy, Edward R. White, Hui Huang Tay, Hin Chun Yau, Milo S.P. Shaffer
Carbon 2016 Volume 108() pp:423-432
Publication Date(Web):November 2016
DOI:10.1016/j.carbon.2016.07.034
As-synthesised single-walled carbon nanotubes (SWCNTs) are often contaminated with amorphous carbon and residual catalyst particles. These contaminants have a detrimental effect on the effective mechanical and electronic properties, limiting their performance in many applications. A comparative series of SWCNT purifications including acid treatments, gas phase purifications and recently-developed reductive purifications have been conducted using a single commercial SWCNT type (Tuball™). Each of the purification procedures was selected for its potential scalability to bulk quantities and evaluated for the extent of impurity removal, SWCNT damage, and overall yield. Raman spectra confirmed that reductive purification using sodium naphthalide gave the lowest D/G ratio, suggesting that the sp2 carbon framework was most effectively preserved, whilst removing a large proportion (∼74%) of the metal impurities. Conversely, nitric acid treatment was most effective at removing virtually all the metal impurities, but the sp2 carbon framework was most heavily damaged in the process. The development of scalable, one pot, reductive separations provides a useful new approach to SWCNT purification.
Co-reporter:A. García-Trenco, E. R. White, M. S. P. Shaffer and C. K. Williams
Catalysis Science & Technology 2016 vol. 6(Issue 12) pp:4389-4397
Publication Date(Web):28 Jan 2016
DOI:10.1039/C5CY01994J
A simple one-pot synthetic method allows the preparation of hybrid catalysts, based on colloidal Cu/ZnO nanoparticles (NPs), used for the liquid phase synthesis of DME from syngas. The method obviates the high temperature calcinations and pre-reduction treatments typically associated with such catalysts. The hybrid catalysts are applied under typical industrially relevant conditions. The nature of the hybrid catalysts, the influence of the acid component, mass ratio between components, and Cu/Zn composition are assessed. The best catalysts comprise a colloidal mixture of Cu/ZnO NPs, as the methanol synthesis component, and γ-Al2O3, as the methanol dehydration component. These catalysts show high DME selectivity (65–70% C). Interestingly, the activity (relative to Cu content) is up to three times higher than that for the reference hybrid catalyst based on the commercial Cu/ZnO/Al2O3 methanol synthesis catalyst. The hybrid catalysts are stable for at least 20 h time-on-stream, not showing any significant sintering of the Cu0 phase. Post-catalysis, HR-TEM and STEM/EDX show that the hybrid catalysts consist of Cu0 and ZnO NPs with an average size of 5–7 nm with γ-Al2O3 particles in close proximity.
Co-reporter:Tomi M. Herceg, Sung-Ho Yoon, M. Shukur Zainol Abidin, Emile S. Greenhalgh, Alexander Bismarck, Milo S.P. Shaffer
Composites Science and Technology 2016 Volume 127() pp:62-70
Publication Date(Web):28 April 2016
DOI:10.1016/j.compscitech.2016.01.017
A powder based processing route was developed to allow manufacturing of thermosetting nanocomposites with high (20 wt%) carbon nanotube (CNT) loading fractions. Adaptation of high shear mixing methods, as used in thermoplastic processing, ensured that the CNTs were well distributed and dispersed even at the highest loadings. By minimising flow distances, compression moulding of powders ensured that the CNTs did not agglomerate during consolidation, and yielded a percolated CNT network in a nanocomposite with excellent electrical and thermal conductivities of 67 S m−1 and 0.77 W m−1 K−1, respectively. Unusually, the CNTs provided effective mechanical reinforcement at even the highest loadings; embrittlement is minimised by avoiding large scale inhomogeneities and the maximum measured Young's modulus (5.4 GPa) and yield strength (90 MPa) could make the nanocomposite an attractive matrix for continuous fibre composites. The macromechanical measurements were interpolated using micromechanical models that were previously successfully applied at the nanoscale.
Co-reporter:Robert Menzel;Suelen Barg;Miriam Mira;David B. Anthony;Salem M. Bawaked;Mohamed Mokhtar;Shaeel A. Al-Thabaiti;Sulaiman N. Basahel;Eduardo Saiz
Advanced Functional Materials 2015 Volume 25( Issue 1) pp:28-35
Publication Date(Web):
DOI:10.1002/adfm.201401807
The Joule heating properties of an ultralight nanocarbon aerogel are investigated with a view to potential applications as energy-efficient, local gas heater, and other systems. Thermally reduced graphene oxide (rGO) aerogels (10 mg cm−3) with defined shape are produced via emulsion-templating. Relevant material properties, including thermal conductivity, electrical conductivity and porosity, are assessed. Repeatable Joule heating up to 200 °C at comparatively low voltages (≈1 V) and electrical power inputs (≈2.5 W cm−3) is demonstrated. The steady-state core and surface temperatures are measured, analyzed and compared to analogous two-dimensional nanocarbon film heaters. The assessment of temperature uniformity suggests that heat losses are dominated by conductive and convective heat dissipation at the temperature range studied. The radial temperature gradient of an uninsulated, Joule-heated sample is analyzed to estimate the aerogel's thermal conductivity (around 0.4 W m−1 K−1). Fast initial Joule heating kinetics and cooling rates (up to 10 K s−1) are exploited for rapid and repeatable temperature cycling, important for potential applications as local gas heaters, in catalysis, and for regenerable of solid adsorbents. These principles may be relevant to wide range of nanocarbon networks and applications.
Co-reporter:Neil J. Brown, Andrés García-Trenco, Jonathan Weiner, Edward R. White, Matthew Allinson, Yuxin Chen, Peter P. Wells, Emma K. Gibson, Klaus Hellgardt, Milo S. P. Shaffer, and Charlotte K. Williams
ACS Catalysis 2015 Volume 5(Issue 5) pp:2895
Publication Date(Web):April 3, 2015
DOI:10.1021/cs502038y
A series of zinc oxide and copper(0) colloidal nanocatalysts, produced by a one-pot synthesis, are shown to catalyze the hydrogenation of carbon dioxide to methanol. The catalysts are produced by the reaction between diethyl zinc and bis(carboxylato/phosphinato)copper(II) precursors. The reaction leads to the formation of a precatalyst solution, characterized using various spectroscopic (NMR, UV–vis spectroscopy) and X-ray diffraction/absorption (powder XRD, EXAFS, XANES) techniques. The combined characterization methods indicate that the precatalyst solution contains copper(0) nanoparticles and a mixture of diethyl zinc and an ethyl zinc stearate cluster compound [Et4Zn5(stearate)6]. The catalysts are applied, at 523 K with a 50 bar total pressure of a 3:1 mixture of H2/CO2, in the solution phase, quasi-homogeneous, hydrogenation of carbon dioxide, and they show high activities (>55 mmol/gZnOCu/h of methanol). The postreaction catalyst solution is characterized using a range of spectroscopies, X-ray diffraction techniques, and transmission electron microscopy (TEM). These analyses show the formation of a mixture of zinc oxide nanoparticles, of size 2–7 nm and small copper nanoparticles. The catalyst composition can be easily adjusted, and the influence of the relative loadings of ZnO/Cu, the precursor complexes and the total catalyst concentration on the catalytic activity are all investigated. The optimum system, comprising a 55:45 loading of ZnO/Cu, shows equivalent activity to a commercial, activated methanol synthesis catalyst. These findings indicate that using diethyl zinc to reduce copper precursors in situ leads to catalysts with excellent activities for the production of methanol from carbon dioxide.Keywords: catalysts from organometallic; CO2 reduction; colloidal catalysts; Cu-ZnO catalysts; hydrogenation of CO2; methanol synthesis; nanocatalysts; nanoparticles
Co-reporter:A. J. Clancy, J. Melbourne and M. S. P. Shaffer
Journal of Materials Chemistry A 2015 vol. 3(Issue 32) pp:16708-16715
Publication Date(Web):10 Jul 2015
DOI:10.1039/C5TA03561A
Reductive dissolution is a promising processing route for single walled carbon nanotubes (SWCNTs) that avoids the damage caused by ultrasonication and aggressive oxidation whilst simultaneously allowing access to a wealth of SWCNT functionalisation reactions. Here, reductive dissolution has been simplified to a single one-pot reaction through the use of sodium naphthalide in dimethylacetamide allowing direct synthesis of SWCNT Na+ solutions. Gram quantities of SWCNTs can be dissolved at concentrations over 2 mg mL−1. These reduced SWCNT solutions can easily be functionalised through the addition of alkyl halides; reducing steric bulk of the grafting moiety and increasing polarisability of the leaving group increases the extent of functionalisation. An optimised absolute sodium concentration of 25 mM is shown to be more important than carbon to metal ratio in determining the maximum degree of functionalisation. This novel dissolution system can be modified for use as a non-destructive purification route for raw SWCNT powder by adjusting the degree of charging to dissolve carbonaceous impurities, catalyst particles and defective material, before processing the remaining SWCNTs.
Co-reporter:Francois De Luca, Robert Menzel, Jonny J. Blaker, John Birkbeck, Alexander Bismarck, and Milo S. P. Shaffer
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 48) pp:26783
Publication Date(Web):November 12, 2015
DOI:10.1021/acsami.5b08838
The bricks and mortar in the classic structure of nacre have characteristic geometry, aspect ratios and relative proportions; these key parameters can be retained while scaling down the absolute length scale by more than 1 order of magnitude. The results shed light on fundamental scaling behavior and provide new opportunities for high performance, yet ductile, lightweight nanocomposites. Reproducing the toughening mechanisms of nacre at smaller length scales allows a greater volume of interface per unit volume while simultaneously increasing the intrinsic properties of the inorganic constituents. Layer-by-layer (LbL) assembly of poly(sodium 4-styrenesulfonate) (PSS) polyelectrolyte and well-defined [Mg2Al(OH)6]CO3.nH2O layered double hydroxide (LDH) platelets produces a dense, oriented, high inorganic content (∼90 wt %) nanostructure resembling natural nacre, but at a shorter length scale. The smaller building blocks enable the (self-) assembly of a higher quality nanostructure than conventional mimics, leading to improved mechanical properties, matching those of natural nacre, while allowing for substantial plastic deformation. Both strain hardening and crack deflection mechanisms were observed in situ by scanning electron microscopy (SEM) during nanoindentation. The best properties emerge from an ordered nanostructure, generated using regular platelets, with narrow size dispersion.Keywords: deformation mechanisms; in situ characterization; layer-by-layer assembly; mechanical properties; nacre-nanomimetic; plastic deformation; “brick-and-mortar” arrangement
Co-reporter:Hin Chun Yau, Mustafa K. Bayazit, Joachim H. G. Steinke and Milo S. P. Shaffer
Chemical Communications 2015 vol. 51(Issue 93) pp:16621-16624
Publication Date(Web):15 Sep 2015
DOI:10.1039/C5CC06526G
Sonicating pure N-methyl pyrrolidone (NMP) rapidly produces contaminating organic nanoparticles, at increasing concentration with time, as investigated by AFM, as well as UV-vis, IR and NMR spectroscopies. The contamination issue affects carbon nanotube, and likely other nanomaterial, dispersions processed by sonication in organic solvents.
Co-reporter:Hin Chun Yau, Mustafa K. Bayazit, Piers R. J. Gaffney, Andrew G. Livingston, Joachim H. G. Steinke and Milo S. P. Shaffer
Polymer Chemistry 2015 vol. 6(Issue 7) pp:1056-1065
Publication Date(Web):07 Nov 2014
DOI:10.1039/C4PY01167H
Poly(ethylene glycol) [1, PEG∼4(OH)2, Mn ∼ 200], glycerol ethoxylate [2, PEG∼21(OH)3, Mn ∼ 1000] and pentaerythritol ethoxylate [3, PEG∼15(OH)4, Mn ∼ 797] react directly with phenyl-C61-butyric acid methyl ester (PCBM), in the presence of dibutyltinoxide (DBTO) catalyst at 140 °C, to give a mixture of fullerene [C60] end-capped PEGs via transesterification. Among these PEG linkers, only PEG∼4(OPCB)2 (4a) (OPCB: ester oxygen linked phenyl-C61-butyryl group) was successfully isolated from the crude product mixture in the fully end-capped form. Fully acylated PEG∼21(OPCB)3 (5) and PEG∼15(OPCB)4 (6) could not be separated chromatographically from incompletely reacted species due to the polydispersity in branch lengths. This purification challenge was overcome by using a monodisperse branched core, 1,3,5-tris(octagoloxymethyl)benzene [7, PEG24(OH)3] to give a monodisperse tris-fullerene homostar, PEG24(OPCB)3 (8). The structures of the bis- and tris-fullerene products were confirmed by MALDI-TOF mass spectrometry and 1H NMR spectroscopy with supporting FTIR and UV-vis spectroscopic analysis.
Co-reporter:Almudena Celaya-Sanfiz, Nicolás Morales-Vega, Martina De Marco, Diana Iruretagoyena, Mohamed Mokhtar, Salem M. Bawaked, Sulaiman N. Basahel, Shaeel A. Al-Thabaiti, Abdulrahman O. Alyoubi, Milo S.P. Shaffer
Journal of Molecular Catalysis A: Chemical 2015 Volume 398() pp:50-57
Publication Date(Web):March 2015
DOI:10.1016/j.molcata.2014.11.002
•Mg–Al-layered double hydroxide catalysts supported on multi-walled carbon nanotubes.•MWNTs improve dispersion and catalytic performance for the self-condensation of acetone.•MWNT oxidation debris also partially inhibits the reaction.•Intermediate MWNT loading optimizes LDH enhancement and activity/total mass of supported catalyst.Mg–Al (2:1) layered double hydroxides (LDH) were supported onto multi-walled carbon nanotubes (MWNTs), in order to optimize the catalytic performance of these solid base catalysts. The resulting LDH/MWNT hybrids after activation (heat-treatment/hydration) were compared to the pure activated LDH catalyst for the self-condensation of acetone. Smaller LDH crystallite sizes and a good dispersion of the LDH particles on the MWNTs increase the number of active centers accessible to acetone, and hence enhance activity. However, debris created during MWNT oxidation inhibits the reaction, leading to an optimum intermediate hybrid composition.
Co-reporter:Takuya Morishita, Adam J. Clancy and Milo S. P. Shaffer
Journal of Materials Chemistry A 2014 vol. 2(Issue 36) pp:15022-15028
Publication Date(Web):22 Jul 2014
DOI:10.1039/C4TA02349H
In bulk applications, it is essential that graphene sheets disperse individually in solvents or matrices, and therefore, suitable functionalisation regimes are crucially important. Here, isolated, highly soluble, alkyl-grafted graphenes were synthesised by reacting exfoliated Na-reduced graphite intercalation compounds (GIC) with alkyl halides. In this reaction, efficient exfoliation of the Na-reduced GICs into individually-dispersed negatively-charged graphenes provides accessible surface area for grafting. Increasing the alkyl chain length leads to large decrease of the grafting ratio (GR), demonstrating that steric factors also play an important role. However, optimising the Na concentration (C/Na ratio) in the reaction was very effective for improved exfoliation and increased GR. The X-ray diffraction measurements suggest that particular C/Na ratios (C/Na = ∼12) led to full exfoliation, by balancing total charge and charge condensation effects and that the GR can be significantly increased even in the case of long alkyl chains (eicosyl chains), corresponding to a high solubility of 37 μg ml−1 and high yield in o-dichlorobenzene. Moreover, the absolute Na concentration is the critical parameter, with the same optimum (∼0.01 M) for exfoliation and grafting of GIC at all graphite concentrations; it was possible to graft even at high graphite concentration (0.3 M (3.6 mg ml−1)) successfully.
Co-reporter:Mani Diba, Ainara García-Gallastegui, Robin N. Klupp Taylor, Fatemeh Pishbin, Mary P. Ryan, Milo S.P. Shaffer, Aldo R. Boccaccini
Carbon 2014 Volume 67() pp:656-661
Publication Date(Web):February 2014
DOI:10.1016/j.carbon.2013.10.041
The electrophoretic deposition (EPD) technique is an attractive approach for development of graphene and graphene oxide (GO) films for a variety of applications. However, in order to establish the influence of the EPD parameters on the properties of the deposited films, a deeper investigation of the fundamental GO-EPD kinetics is required. Previous studies have reported a simultaneous anodic reduction of GO flakes during EPD, complicating the kinetics and process control. Therefore, in this study, low voltages were used to prevent significant GO reduction during EPD, as confirmed by XPS and FTIR. Accordingly, the GO-EPD kinetics was established as a function of deposition time and voltage, accompanied by microscopic characterization of the deposited films. The experimental results show that the deposition follows a linear growth law, in good agreement with the predictions of Hamaker’s law. Comparisons of optical absorbance and profilometry provide estimates of (reduced) GO deposition rate, extinction coefficient, and density.
Co-reporter:Hin Chun Yau, Mustafa K. Bayazit, Joachim H. G. Steinke, and Milo S. P. Shaffer
Macromolecules 2014 Volume 47(Issue 15) pp:4870-4875
Publication Date(Web):July 21, 2014
DOI:10.1021/ma501200e
Fullerene [60] (C60) and poly(ethylene glycol) (PEG) adducts were prepared via 1,3-dipolar cycloaddition of bis-azido-terminated linear PEG (N3-PEG-N3) and C60. While long chain length PEGs (Mn = 1000 and 3350 Da) yielded the cyclic diamond ring structures ( and ), short-chained PEG (Mn = 200 Da) yielded a telechelic dumbbell structure (C60-PEG200-C60). Both dumbbell and diamond ring structures were characterized by MALDI-TOF-MS, 1H NMR, FTIR, UV–vis, and elemental analysis (EA). The results highlight the structural dependence of the PEG-C60 adducts on the chain length of the azido-terminated polymer, a factor previously neglected.
Co-reporter:Shu Chen, Sheng Hu, Elizabeth F. Smith, Pakatip Ruenraroengsak, Andrew J. Thorley, Robert Menzel, Angela E. Goode, Mary P. Ryan, Teresa D. Tetley, Alexandra E. Porter, Milo S.P. Shaffer
Biomaterials 2014 35(17) pp: 4729-4738
Publication Date(Web):
DOI:10.1016/j.biomaterials.2014.02.002
Co-reporter:Robert Menzel, Andre Duerrbeck, Emanuela Liberti, Hin Chun Yau, David McComb, and Milo S. P. Shaffer
Chemistry of Materials 2013 Volume 25(Issue 10) pp:2137
Publication Date(Web):April 17, 2013
DOI:10.1021/cm400785z
Two-dimensional TiO2 anatase nanoplatelets can be synthesized via solvothermal reaction of titanium(IV) isopropoxide in the presence of structure-directing hydrogen fluoride. High resolution electron transmission microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray powder diffraction (XRD) show that the resulting nanoplatelets are heavily–truncated, octahedral TiO2 anatase nanocrystals with a large fraction of high-energy (001) crystal facets. Systematic studies provide insight into the underlying reaction pathways and the competing, morphology-determining roles of hydrogen fluoride and water during nanocrystal formation. TiF4 can be used as an additional or alternative fluoride source in hydrolytic systems, allowing the study of markedly higher fluoride concentrations than previously reported, and/or avoiding the use of HF as a starting material. The findings can be plotted on a HF:H2O:Ti ternary diagram to provide guidelines for the control of average dimensions, aspect ratio, degree of truncation and, thereby, fraction of (001) crystal facets. Depending on the composition of the reaction system, oriented attachment of the anatase nanoplatelets along either (001) or (101) facets can be observed. The photocatalytic activity of nananocrystals with different aspect ratios, determined in dye degradation experiments, demonstrates higher activity of the (001) than (101) anatase facets.Keywords: crystal facets; nanocrystal morphology; nanoplatelets; TiO2,anatase;
Co-reporter:Natasha Shirshova, Alexander Bismarck, Shuaijin Carreyette, Quentin P. V. Fontana, Emile S. Greenhalgh, Per Jacobsson, Patrik Johansson, Maciej J. Marczewski, Gerhard Kalinka, Anthony R. J. Kucernak, Johan Scheers, Milo S. P. Shaffer, Joachim H. G. Steinke and Malte Wienrich
Journal of Materials Chemistry A 2013 vol. 1(Issue 48) pp:15300-15309
Publication Date(Web):11 Nov 2013
DOI:10.1039/C3TA13163G
‘Structural electrolytes’ retain the desirable mechanical characteristics of structural (epoxy) resins whilst introducing sufficient ionic conductivity to operate as electrolytes in electrochemical devices. Here, a series of ionic liquid–epoxy resin composites were prepared to identify the optimum system microstructure required to achieve a high level of multifunctionality. The ionic conductivity, mechanical properties, thermal stability and morphology of the cured epoxy based structural electrolytes were studied as a function of phase composition for three fully formulated high performance structural epoxy systems. At only 30 wt% of structural resin and 70 wt% of ionic liquid based electrolyte, stiff monolithic plaques with thicknesses of 2–3 mm were obtained with a room temperature ionic conductivity of 0.8 mS cm−1 and a Young's modulus of 0.2 GPa. This promising performance can be attributed to a long characteristic length scale spinodal microstructure, suggesting routes to further optimisation in the future.
Co-reporter:Hui Qian, Anthony R. Kucernak, Emile S. Greenhalgh, Alexander Bismarck, and Milo S. P. Shaffer
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 13) pp:6113
Publication Date(Web):May 13, 2013
DOI:10.1021/am400947j
A novel multifunctional material has been designed to provide excellent mechanical properties while possessing a high electrochemical surface area suitable for electrochemical energy storage: structural carbon fiber fabrics are embedded in a continuous network of carbon aerogel (CAG) to form a coherent but porous monolith. The CAG-modification process was found to be scalable and to be compatible with a range of carbon fiber fabrics with different surface properties. The incorporation of CAG significantly increased the surface area of carbon fiber fabrics, and hence the electrochemical performance, by around 100-fold, resulting in a CAG-normalized specific electrode capacitance of around 62 F g–1, determined by cyclic voltammetry in an aqueous electrolyte. Using an ionic liquid (IL) electrolyte, the estimated energy density increased from 0.003 to 1 Wh kg–1, after introducing the CAG into the carbon fiber fabric. ‘Proof-of-concept’ multifunctional structural supercapacitor devices were fabricated using an IL-modified solid-state polymer electrolyte as a multifunctional matrix to provide both ionic transport and physical support for the primary fibers. Two CAG-impregnated carbon fabrics were sandwiched around an insulating separator to form a functioning structural electrochemical double layer capacitor composite. The CAG-modification not only improved the electrochemical surface area, but also reinforced the polymer matrix surrounding the primary fibers, leading to dramatic improvements in the matrix-dominated composite properties. Increases in in-plane shear strength and modulus, of up to 4.5-fold, were observed, demonstrating that CAG-modified structural carbon fiber fabrics have promise in both pure structural and multifunctional energy storage applications.Keywords: carbon aerogel; carbon fiber; composites; multifunctional; supercapacitors;
Co-reporter:N. J. Brown, J. Weiner, K. Hellgardt, M. S. P. Shaffer and C. K. Williams
Chemical Communications 2013 vol. 49(Issue 94) pp:11074-11076
Publication Date(Web):21 Oct 2013
DOI:10.1039/C3CC46203J
Colloidal solutions of ZnO–Cu nanoparticles can be used as catalysts for the reduction of carbon dioxide with hydrogen. The use of phosphinate ligands for the synthesis of the nanoparticles from organometallic precursors improves the reductive stability and catalytic activity of the system.
Co-reporter:Hui Qian, Hele Diao, Natasha Shirshova, Emile S. Greenhalgh, Joachim G.H. Steinke, Milo S.P. Shaffer, Alexander Bismarck
Journal of Colloid and Interface Science 2013 Volume 395() pp:241-248
Publication Date(Web):1 April 2013
DOI:10.1016/j.jcis.2012.12.015
The feasibility of modifying conventional structural carbon fibres via activation has been studied to create fibres, which can be used simultaneously as electrode and reinforcement in structural composite supercapacitors. Both physical and chemical activation, including using steam, carbon dioxide, acid and potassium hydroxide, were conducted and the resulting fibre properties compared. It was proven that the chemical activation using potassium hydroxide is an effective method to prepare activated structural carbon fibres that possess both good electrochemical and mechanical properties. The optimal activation conditions, such as the loading of activating agent and the burn-off of carbon fibres, was identified and delivered a 100-fold increase in specific surface area and 50-fold improvement in specific electrochemical capacitance without any degradation of the fibre mechanical properties. The activation process was successfully scaled-up, showing good uniformity and reproducibility. These activated structural carbon fibres are promising candidates as reinforcement/electrodes for multifunctional structural energy storage devices.Graphical abstractHighlights► Identified an optimal activation method on structural carbon fibres. ► Revealed relationships between burn-off and the surface morphology and properties. ► Explored the multifunctional potential of activated structural carbon fibres. ► Proved improvements in electrical properties without degrading mechanical properties. ► Developed an efficient strategy to fabricate multifunctional reinforcement materials.
Co-reporter:Stephen A. Hodge, Siân Fogden, Christopher A. Howard, Neal T. Skipper, and Milo S. P. Shaffer
ACS Nano 2013 Volume 7(Issue 2) pp:1769
Publication Date(Web):January 21, 2013
DOI:10.1021/nn305919p
The dissolution of single-walled carbon nanotubes (SWCNTs) remains a fundamental challenge, reliant on aggressive chemistry or ultrasonication and lengthy ultracentrifugation. In contrast, simple nonaqueous electrochemical reduction leads to spontaneous dissolution of individualized SWCNTs from raw, unprocessed powders. The intrinsic electrochemical stability and conductivity of these nanomaterials allow their electrochemical dissolution from a pure SWCNT cathode to form solutions of individually separate and distinct (i.e., discrete) nanotube anions with varying charge density. The integrity of the SWCNT sp2 framework during the charge/discharge process is demonstrated by optical spectroscopy data. Other than a reversible change in redox/solvation state, there is no obvious chemical functionalization of the structure, suggesting an analogy to conventional atomic electrochemical dissolution. The heterogeneity of as-synthesized SWCNT samples leads to the sequential dissolution of distinct fractions over time, with fine control over the electrochemical potential. Initial preferential dissolution of defective nanotubes and carbonaceous debris provides a simple, nondestructive means to purify raw materials without recourse to the usual, damaging, competitive oxidation reactions. Neutral SWCNTs can be recovered either by electroplating at an anode or by reaction with a suitable electrophile.Keywords: carbon nanotube; deposition; dispersion; electrochemistry; functionalization; purification
Co-reporter:Stephen A. Hodge, Mustafa K. Bayazit, Karl S. Coleman and Milo S. P. Shaffer
Chemical Society Reviews 2012 vol. 41(Issue 12) pp:4409-4429
Publication Date(Web):19 Apr 2012
DOI:10.1039/C2CS15334C
Single-walled carbon nanotubes (SWNTs) are a fundamental family of distinct molecules, each bearing the possibility of different reactivities due to their intrinsically distinct chemical properties. SWNT syntheses generate a heterogeneous mixture of species with varying electronic character, lengths, diameters and helicities, (n,m), as well as other amorphous, graphitic and metal catalyst impurities. In recent years, selective syntheses and post-synthetic separation strategies have advanced, driven by the requirement for pure SWNTs displaying particular features. Covalent surface modifications are widely-used to adapt SWNTs for specific applications with modified solubility, compatibility and specific functionalities. In many cases, such reactions have been found to be selective, illuminating the fundamentally distinct chemistry of each (n,m) species. This differential reactivity has found immediate utility in facilitating the sorting of nanotubes according to specific diameter, electronic properties and, most importantly, helicity. In this tutorial review, we discuss a wide range of selective reactions, the mechanisms that are thought to govern selectivity, and the challenges of separating, characterising and regenerating the modified SWNTs.
Co-reporter:Katherine L. Orchard, Milo S. P. Shaffer, and Charlotte K. Williams
Chemistry of Materials 2012 Volume 24(Issue 13) pp:2443
Publication Date(Web):June 20, 2012
DOI:10.1021/cm300058d
Well-defined ZnO nanoparticles with bound carboxylate surface-functionalization and narrow size distribution were prepared via an efficient organometallic hydrolysis route, occurring at ambient temperature and without postsynthesis refinement. Depending on the reaction conditions, the nanoparticles’ degree of surface coverage or diameter was controlled independently. The method was used for the in situ preparation of well-dispersed ZnO/epoxy resin nanocomposites.Keywords: hydrolysis organo-zinc; organic−inorganic hybrid composites; polymers; ZnO nanoparticles;
Co-reporter:Ainara Garcia-Gallastegui, Diana Iruretagoyena, Veronica Gouvea, Mohamed Mokhtar, Abdullah M. Asiri, Sulaiman N. Basahel, Shaeel A. Al-Thabaiti, Abdulrahman O. Alyoubi, David Chadwick, and Milo S. P. Shaffer
Chemistry of Materials 2012 Volume 24(Issue 23) pp:4531
Publication Date(Web):October 29, 2012
DOI:10.1021/cm3018264
Layered double hydroxides (LDHs) show great potential as CO2 adsorbent materials, but require improvements in stability and CO2 adsorption capacity for commercial applications. In the current study, graphene oxide provides a light-weight, charge-complementary, two-dimensional (2D) material that interacts effectively with the 2D LDHs, in turn enhancing the CO2 uptake capacity and multicycle stability of the assembly. As a result, the absolute capacity of the LDH was increased by 62% using only 7 wt % graphene oxide (GO) as a support. The experimental procedure for the synthesis of the materials is based on a direct precipitation of the LDH nanoparticles onto GO followed by a structural and physical characterization by electron microscopy, X-ray diffraction, thermogravimetric analysis, and Brunauer–Emmett–Teller (BET) surface area measurements. Detailed titration confirmed the compatibility of the surface chemistry. After thermal decomposition, mixed metal oxides (MMOs) are obtained with the basic sites required for the CO2 adsorption. A range of samples with different proportions of GO/MMO were prepared, fully characterized, and correlated with the CO2 sorption capacity, established via TGA.Keywords: CO2 capture and storage (CCS); CO2 sorption; graphene; graphene oxide (GO); hydrotalcite(s); layered double hydroxide(s) (LDHs);
Co-reporter:Ainara Garcia-Gallastegui, Diana Iruretagoyena, Mohamed Mokhtar, Abdullah M. Asiri, Sulaiman N. Basahel, Shaeel A. Al-Thabaiti, Abdulrahman O. Alyoubi, David Chadwick and Milo S. P. Shaffer
Journal of Materials Chemistry A 2012 vol. 22(Issue 28) pp:13932-13940
Publication Date(Web):14 Jun 2012
DOI:10.1039/C2JM00059H
Layered double hydroxides (LDHs) are promising materials for CO2 sorption, although improvements in performance are required for practical applications. In the current study, the CO2 sorption capacity and multi-cycle stability were both increased by introducing an open supporting framework of multi-walled carbon nanotubes (MWNTs). This nanostructured inert network provides a high surface area, maximizing the gas accessibility and minimizing coarsening effects. Specifically, LDH nanoparticles were precipitated directly onto MWNTs, initially oxidised to ensure a favourable electrostatic interaction and hence a good dispersion. The dependence of the structural and physical properties of the Mg–Al LDH grown on MWNT supports has been studied, using electron microscopy, X-ray diffraction, thermogravimetric analysis (TGA), and BET surface area, and correlated with the CO2 sorption capacity, established via TGA and temperature programmed desorption measurements. The use of a MWNT support was found to improve the absolute capacity and cycle stability of the hybrid adsorbent under dry conditions.
Co-reporter:Robert Menzel, Ben F. Cottam, Sabina (Chyła) Ziemian and Milo S. P. Shaffer
Journal of Materials Chemistry A 2012 vol. 22(Issue 24) pp:12172-12178
Publication Date(Web):15 May 2012
DOI:10.1039/C2JM30922J
TiO2 anatase nanorods were grown via the non-hydrolytic elimination reaction between TiCl4 and Ti(OiPr)4 in the presence of oleic acid. The reaction was carried out in two stages in order to separate TiOx seed nucleation at lower temperatures from nanorod growth at higher temperatures. This separation made it possible to study the crystal growth mechanism in more detail, indicating that nanorod formation occurred through a combination of atom-by-atom addition and oriented attachment of the initial seeds. The two-stage reaction approach also enabled considerably improved control of titania nanorod formation in terms of product morphology, crystallinity and uniformity. The effects of a range of reaction parameters, including reaction duration, temperature, dilution and stoichiometry, were investigated.
Co-reporter:Johann Cho, Aldo R. Boccaccini, Milo S.P. Shaffer
Carbon 2012 Volume 50(Issue 11) pp:3967-3976
Publication Date(Web):September 2012
DOI:10.1016/j.carbon.2012.03.049
Injection chemical vapour deposition (ICVD) was used for the preparation of multi-walled carbon nanotubes (MWCNTs) with varying lengths and diameters. The concentration of iron injected with the feedstock is related to the resulting average MWCNT dimensions, mass yield, packing density, crystallinity, and iron content. An optimum set of conditions is identified that maintains a constant diameter during growth; higher iron injection concentrations lead to an increasing MWCNT diameter as growth proceeds. Carbon nanotubes are frequently oxidised in mixtures of concentrated nitric and sulphuric acids in order to purify, functionalise, and shorten as-synthesised materials. Here, the carbon:acid stoichiometry is systematically varied, and shown to control the yield and dimensions of the resulting oxidised MWCNTs in a predictable manner, for the various ICVD starting materials. With increasing acid content, the yield of nanotubes decreases, the fraction of oxidised debris increases, and the initial, defect-driven, cutting reaction saturates, whilst thinning reactions continue. The results provide insight into both ICVD synthesis and acid oxidation of MWCNTs, as well as a means to prepare well-dispersed samples with controlled dimensions.
Co-reporter:Robert Menzel, Alexander Bismarck, Milo S.P. Shaffer
Carbon 2012 50(10) pp: 3416-3421
Publication Date(Web):
DOI:10.1016/j.carbon.2012.02.094
Co-reporter:Siân Fogden, Christopher A. Howard, Richard K. Heenan, Neal T. Skipper, and Milo S. P. Shaffer
ACS Nano 2012 Volume 6(Issue 1) pp:54
Publication Date(Web):December 29, 2011
DOI:10.1021/nn2041494
As synthesized, bulk single-walled carbon nanotube (SWNT) samples are typically highly agglomerated and heterogeneous. However, their most promising applications require the isolation of individualized, purified nanotubes, often with specific optoelectronic characteristics. A wide range of dispersion and separation techniques have been developed, but the use of sonication or ultracentrifugation imposes severe limits on scalability and may introduce damage. Here, we demonstrate a new, intrinsically scalable method for SWNT dispersion and separation, using reductive treatment in sodium metal-ammonia solutions, optionally followed by selective dissolution in a polar aprotic organic solvent. In situ small-angle neutron scattering demonstrates the presence of dissolved, unbundled SWNTs in solution, at concentrations reaching at least 2 mg/mL; the ability to isolate individual nanotubes is confirmed by atomic force microscopy. Spectroscopy data suggest that the soluble fraction contains predominately large metallic nanotubes; a potential new mechanism for nanotube separation is proposed. In addition, the G/D ratios observed during the dissolution sequence, as a function of metal:carbon ratio, demonstrate a new purification method for removing carbonaceous impurities from pristine SWNTs, which avoids traditional, damaging, competitive oxidation reactions.Keywords: nanotubide; purification; reductive dissolution; separation; single-walled carbon nanotubes
Co-reporter:Hui Qian, Gerhard Kalinka, K. L. Andrew Chan, Sergei G. Kazarian, Emile S. Greenhalgh, Alexander Bismarck and Milo S. P. Shaffer
Nanoscale 2011 vol. 3(Issue 11) pp:4759-4767
Publication Date(Web):06 Oct 2011
DOI:10.1039/C1NR10497G
The introduction of carbon nanotubes (CNTs) modifies bulk polymer properties, depending on intrinsic quality, dispersion, alignment, interfacial chemistry and mechanical properties of the nanofiller. These effects can be exploited to enhance the matrices of conventional microscale fibre-reinforced polymer composites, by using primary reinforcing fibres grafted with CNTs. This paper presents a methodology that combines atomic force microscopy, polarised Raman spectroscopy, and nanoindentation techniques, to study the distribution, alignment and orientation of CNTs in the vicinity of epoxy-embedded micrometre-scale silica fibres, as well as, the resulting local mechanical properties of the matrix. Raman maps of key features in the CNT spectra clearly show the CNT distribution and orientation, including a ‘parted’ morphology associated with long grafted CNTs. The hardness and indentation modulus of the epoxy matrix were improved locally by 28% and 24%, respectively, due to the reinforcing effects of CNTs. Moreover, a slower stress relaxation was observed in the epoxy region containing CNTs, which may be due to restricted molecular mobility of the matrix. The proposed methodology is likely to be relevant to further studies of nanocomposites and hierarchical composites.
Co-reporter:Katherine L. Orchard, Jonathan E. Harris, Andrew J. P. White, Milo S. P. Shaffer, and Charlotte K. Williams
Organometallics 2011 Volume 30(Issue 8) pp:2223-2229
Publication Date(Web):March 23, 2011
DOI:10.1021/om200004a
NMR and single-crystal X-ray diffraction experiments indicate that the ligand stoichiometry of the complexes formed from the reaction between zinc bis(acetate) and diethylzinc depends on the nature of the solvent (coordinating vs noncoordinating) and that the strength of the donor interaction of a coordinating solvent (THF vs pyridine) affects the nuclearity of the complex’s repeat unit in the solid state. The complexes are active catalysts for the copolymerization of cyclohexene oxide and CO2, under mild conditions.
Co-reporter:Johann Cho;Fawad Inam;Mike J. Reece;Zdeněk Chlup
Journal of Materials Science 2011 Volume 46( Issue 14) pp:4770-4779
Publication Date(Web):2011 July
DOI:10.1007/s10853-011-5387-x
The development of a model CNT-brittle matrix composite system, based on SiO2 glass containing well-dispersed CNTs at up to 15 wt%, allows a direct assessment of the effect of the nanoscale filler on fracture toughness (KIC). Samples were prepared by colloidal heterocoagulation followed by spark plasma sintering. Detailed KIC measurements, using both indentation and notched beam techniques, show a linear improvement with CNT content, with up to a twofold increase of fracture toughness at maximum loading. The results from the two methods used in this study show equivalent trends but differing absolute values; the relative merits of these two approaches to measuring nanocomposite toughness are compared. Possible toughening mechanisms associated with CNT pull-out, crack bridging, and crack deflection are identified, and discussed quantitatively, drawing on conventional short-fibre composite theory and the potential effects of scaling fibre diameter.
Co-reporter:Robert Menzel, Michael Q. Tran, Angelika Menner, Christopher W. M. Kay, Alexander Bismarck and Milo S. P. Shaffer
Chemical Science 2010 vol. 1(Issue 5) pp:603-608
Publication Date(Web):11 Aug 2010
DOI:10.1039/C0SC00287A
High temperature activation of carbon nanotubes (CNTs) provides a new and highly versatile functionalisation strategy. The reaction allows the attachment of a wide variety of functional species onto the nanotube surface at grafting ratios between 1–8 wt%, whilst maintaining the intrinsic properties of the untreated materials. The underlying, radical-based, reaction mechanism has been established by quenching experiments and EPR studies. The distribution of the functionalised sites has been investigated at the microscopic scale using tagging reactions. The grafted products have been characterized by electron microscopy, thermal analysis (TGA), Raman spectroscopy, and inverse gas chromatography (IGC). The change in the CNT surface properties after grafting has been quantified in terms of dispersive and specific surface energies, and altered dispersibilities in a broad range of solvents. It is possible to carry out the reaction using gas phase reagents, providing a clean, efficient, and scalable methodology, relevant to a diverse range of applications.
Co-reporter:Hui Qian, Emile S. Greenhalgh, Milo S. P. Shaffer and Alexander Bismarck
Journal of Materials Chemistry A 2010 vol. 20(Issue 23) pp:4751-4762
Publication Date(Web):04 May 2010
DOI:10.1039/C000041H
The introduction of carbon nanotubes (CNTs) into conventional fibre-reinforced polymer composites creates a hierarchical reinforcement structure and can significantly improve composite performance. This paper reviews the progress to date towards the creation of fibre reinforced (hierarchical) nanocomposites and assesses the potential for a new generation of advanced multifunctional materials. Two alternative strategies for forming CNT-based hierarchical composites are contrasted, the dispersion of CNTs into the composite matrix and their direct attachment onto the primary fibre surface. The implications of each approach for composite processing and performance are discussed, along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting hierarchical composites.
Co-reporter:Hui Qian, Alexander Bismarck, Emile S. Greenhalgh, Milo S.P. Shaffer
Carbon 2010 Volume 48(Issue 1) pp:277-286
Publication Date(Web):January 2010
DOI:10.1016/j.carbon.2009.09.029
Carbon nanotube grafted primary reinforcing fibres are under development for a new generation of hierarchical composites. Pure and nitrogen-doped multi-walled carbon nanotubes (MWCNTs) were grown on silica fibres using the injection chemical vapour deposition method. The morphology and size of the nanotubes were controlled by varying the growth time. The surface structure of the silica fibres after the grafting process was studied by electron microscopy following focused ion beam sectioning; the images confirmed a base growth mechanism and a shallow iron-rich layer. Thermogravimetric analysis indicated a shorter induction period and a faster growth rate for pure rather than nitrogen-doped MWCNTs. Raman characterisation of the grafted MWCNTs showed a decreasing intensity ratio of the D to G modes, moving from the tip to base in both cases; a detailed comparison of different characteristic Raman ratios is provided, using both the peak intensity and the area for the D, G, and G′ signals.
Co-reporter:Hui Qian, Alexander Bismarck, Emile S. Greenhalgh, Milo S.P. Shaffer
Composites Science and Technology 2010 Volume 70(Issue 2) pp:393-399
Publication Date(Web):February 2010
DOI:10.1016/j.compscitech.2009.11.014
Model polymer composites containing carbon nanotube (CNT) grafted fibres provide a means to investigate the influence of nanostructures on interfacial properties. Well-aligned nanotubes, with controllable length, were grown on silica fibres by using the injection chemical vapour deposition method, leading to a significant increase of the fibre surface area. In single fibre tensile tests, this CNT growth reaction reduced the fibre strength, apparently due to catalyst etching; however, the fibre modulus increased significantly. Contact angle measurements, using the drop-on-fibre method, indicated an excellent wettability of the CNT-grafted fibres by poly(methyl methacrylate) (PMMA). PMMA model composites were fabricated and studied using the single fibre fragmentation tests. A dramatic improvement (up to 150%) of the apparent interfacial shear strength (IFSS) was obtained for the composites containing CNT-grafted fibres. The improvement of IFSS was also influenced by the length and morphology of the grafted CNTs.
Co-reporter:Hui Qian, Alexander Bismarck, Emile S. Greenhalgh, Milo S.P. Shaffer
Composites Part A: Applied Science and Manufacturing 2010 Volume 41(Issue 9) pp:1107-1114
Publication Date(Web):September 2010
DOI:10.1016/j.compositesa.2010.04.004
Carbon nanotubes (CNTs) were grafted on IM7 carbon fibres using a chemical vapour deposition method. The overall grafting process resulted in a threefold increase of the BET surface area compared to the original primary carbon fibres (0.57 m2/g). At the same time, there was a degradation of fibre tensile strength by around 15% (depending on gauge length), due to the dissolution of iron catalyst into the carbon; the modulus was not significantly affected. The wetting behaviour between fibres and poly(methyl methacrylate) (PMMA) was directly quantified using contact angle measurements for drop-on-fibre systems and indicated good wettability. Single fibre fragmentation tests were conducted on hierarchical fibre/PMMA model composites, demonstrating a significant (26%) improvement of the apparent interfacial shear strength (IFSS) over the baseline composites. The result is associated with improved stress transfer between the carbon fibres and surrounding matrix, through the grafted CNT layer. The improved IFSS was found to correlate directly with a reduced contact angle between fibre and matrix.
Co-reporter:Arántzazu González-Campo, Katherine L. Orchard, Norio Sato, Milo S. P. Shaffer and Charlotte K. Williams
Chemical Communications 2009 (Issue 27) pp:4034-4036
Publication Date(Web):09 Jun 2009
DOI:10.1039/B905353K
This communication presents a clean and efficient in situ method for the preparation of thermoset composites containing ZnO nanoparticles and/or ZnO-coated carbon nanotubes.
Co-reporter:Johann Cho, Katarzyna Konopka, Krzysztof Rożniatowski, Eva García-Lecina, Milo S.P. Shaffer, Aldo R. Boccaccini
Carbon 2009 Volume 47(Issue 1) pp:58-67
Publication Date(Web):January 2009
DOI:10.1016/j.carbon.2008.08.028
Electrophoretic deposition (EPD) was shown to be a convenient method to fabricate uniform coatings of carbon nanotubes (CNTs) with desired thickness and excellent macroscopic homogeneity. The CNT deposition kinetics are controlled by the applied electric field and deposition time which, in turn, prove to be linearly correlated with the deposition yield and thickness. The CNT films were characterised by using a range of techniques including high resolution scanning electron microscopy, nanoindentation and atomic force microscopy. Nanoindentation results revealed differences in the local microstructure of CNT deposits leading to variations of Young’s modulus and hardness, which were ascribed to differences in the packing density of CNTs, as observed also by AFM. A mathematical model for the kinetic of EPD of CNTs based on Hamaker’s law was proposed and the predictions of the model were shown to be in good agreement with experimental results.
Co-reporter:R. Verdejo, R. Stämpfli, M. Alvarez-Lainez, S. Mourad, M.A. Rodriguez-Perez, P.A. Brühwiler, M. Shaffer
Composites Science and Technology 2009 Volume 69(Issue 10) pp:1564-1569
Publication Date(Web):August 2009
DOI:10.1016/j.compscitech.2008.07.003
Flexible polyurethane (PU) foams, with loading fractions of up to 0.2 wt% carbon nanotubes (CNTs), were made by free-rising foaming using water as blowing agent. Electron microscopy revealed an open cellular structure and a homogeneous dispersion of CNTs, although the incorporation of nanofiller affected the foaming process and thus the final foam density and cellular structure. The compressive response of the foams did not show an unambiguous improvement with CNT content due to the variable foam structure. However, dense films generated by hot pressing the foams indicated a significant intrinsic reinforcement of the polymer, even at low loadings of CNTs. Most significantly, CNTs were found to increase the acoustic activity monotonically at concentrations up to 0.1 wt%.
Co-reporter:Raquel Verdejo;Gavin Jell;Laleh Safinia;Alexer Bismarck;Molly M. Stevens;Milo S.P. Shaffer
Journal of Biomedical Materials Research Part A 2009 Volume 88A( Issue 1) pp:65-73
Publication Date(Web):
DOI:10.1002/jbm.a.31698
Abstract
The remarkable intrinsic properties of carbon nanotubes, including their high mechanical strength, electrical conductivity, and nanoscale 3D architecture, create promising opportunities for the use of nanotube composites in a number of fields, particularly for composites in which conventional fillers cannot be accommodated. In the current study, 3D polyurethane (PU) nanocomposite foams were developed, and their potential biomedical applications were investigated. Multiwalled carbon nanotubes (CNTs) were synthesized by chemical vapor deposition and, following suitable chemical modification, uniformly distributed within the walls of PU foams produced by direct reaction. Although the loading fraction was too low to observe significant mechanical effects, CNT incorporation improved the wettability of the nanocomposite surfaces in a concentration-dependent manner, supporting the claim that the nanotubes are active at the pore surface. Studies of bone cell interactions with the nanocomposite foams revealed that increasing CNT loading fraction did not cause osteoblast cytotoxicity nor have any detrimental effects on osteoblast differentiation or mineralization. The application of “fixed” or embedded CNTs in nondegradable scaffolds is likely advantageous over “loose” or unattached CNTs from a toxicological point of view. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Co-reporter:D.S. Bangarusampath, Holger Ruckdäschel, Volker Altstädt, Jan K.W. Sandler, Didier Garray, Milo S.P. Shaffer
Chemical Physics Letters 2009 Volume 482(1–3) pp:105-109
Publication Date(Web):6 November 2009
DOI:10.1016/j.cplett.2009.09.064
Abstract
Multi-wall carbon nanotubes were dispersed homogeneously throughout a poly(ether ether ketone) matrix by melt processing. The influence of nanotube content on both rheological and electrical properties was analysed. The dynamic storage modulus, G′, shows a characteristic solid-like behavior above 1 wt% nanotubes. A sharp transition from an electrically insulating to a conductive composite was observed between 1 and 1.5 wt%. By applying a power-law relation, the rheological and electrical percolation thresholds were found to be 0.9 wt%, and 1.3 wt%, respectively. Considering this data, Guth’s filler reinforcement theory provides a valuable estimation of the aspect ratio of the nanotubes after processing and indicates substantial length degradation during the dispersion process.
Co-reporter:Katherine L. Orchard, Andrew J. P. White, Milo S. P. Shaffer and Charlotte K. Williams
Organometallics 2009 Volume 28(Issue 19) pp:5828-5832
Publication Date(Web):September 18, 2009
DOI:10.1021/om900683z
In contrast to previously reported alkylzinc carboxylates based on aryl carboxylates, the reaction between diethylzinc and a series of zinc bis(alkyl carboxylate)s yields complexes with a ligand stoichiometry of carboxylate to ethyl of 3:2. The analytical data, including single-crystal X-ray diffraction, indicate that, for “ethylzinc acetate”, the product is an unusual pentameric complex of the form [Zn5(OAc)6(Et)4].
Co-reporter:Robert Menzel, Adam Lee, Alexander Bismarck and Milo S. P. Shaffer
Langmuir 2009 Volume 25(Issue 14) pp:8340-8348
Publication Date(Web):June 3, 2009
DOI:10.1021/la900607s
The surface properties of chemical vapor deposition (CVD)-grown, multiwalled carbon nanotubes (CNTs) have been studied using inverse gas chromatography (IGC). By adapting known IGC methodologies to these challenging materials, the surface character of a broad range of CNT materials can be reliably compared and quantified in terms of dispersive and specific surface energies, electron acceptor and donor numbers, and adsorption capacities. The effect of CNT surface modification by high temperature annealing, thermal oxidation, and grafting of methyl methacrylate was explored. The IGC surface characterization of these materials was consistent with results from other surface-sensitive analytical techniques, including X-ray photoelectron spectroscopy (XPS), titration, and electron microscopy, confirming the validity and sensitivity of our approaches. The same IGC methodologies were successfully applied to characterize three as-received CNT materials which differed significantly in their specific surface areas and functional surface group concentrations.
Co-reporter:RichardA.L. Winchester;Max Whitby;MiloS.P. Shaffer Dr.
Angewandte Chemie 2009 Volume 121( Issue 20) pp:3670-3675
Publication Date(Web):
DOI:10.1002/ange.200805222
Co-reporter:RichardA.L. Winchester;Max Whitby;MiloS.P. Shaffer Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 20) pp:3616-3621
Publication Date(Web):
DOI:10.1002/anie.200805222
Co-reporter:Raquel Verdejo;Philipp Werner;Jan Sandler
Journal of Materials Science 2009 Volume 44( Issue 6) pp:1427-1434
Publication Date(Web):2009 March
DOI:10.1007/s10853-008-3168-y
Poly(ether ether ketone) (PEEK) is a high performance polymer that cannot usually be foamed reliably using conventional injection-moulding processes. Here, vapour-grown carbon nanofibres (CNFs) are introduced to stabilise the foaming process, and the resulting morphology of injection-moulded integral foams is investigated in detail. Different image analysis techniques revealed the positive effect of the nanofiller on the cellular structure. Electron microscopy confirmed a homogeneous dispersion of the nanofibres in the cellular PEEK cores. The mechanical properties of the foam injection-moulded samples, in bending, showed an increase in yield strength and elastic modulus with nanofibre loading fractions up to 15 wt%. Although the compressive properties of the foams were reduced as compared to the solid-polymer, the CNFs clearly offset this reduction in properties. Detailed differential scanning calorimetry (DSC) and dynamic mechanical analysis provide further evidence of an interaction between the matrix and the nanoscale filler.
Co-reporter:Johann Cho;Aldo R. Boccaccini
Journal of Materials Science 2009 Volume 44( Issue 8) pp:1934-1951
Publication Date(Web):2009 April
DOI:10.1007/s10853-009-3262-9
Due to the remarkable physical and mechanical properties of individual, perfect carbon nanotubes (CNTs), they are considered to be one of the most promising new reinforcements for structural composites. Their impressive electrical and thermal properties also suggest opportunities for multifunctional applications. In the context of inorganic matrix composites, researchers have particularly focussed on CNTs as toughening elements to overcome the intrinsic brittleness of the ceramic or glass material. Although there are now a number of studies published in the literature, these inorganic systems have received much less attention than CNT/polymer matrix composites. This paper reviews the current status of the research and development of CNT-loaded ceramic matrix composite (CMC) materials. It includes a summary of the key issues related to the optimisation of CNT-based composites, with particular reference to brittle matrices and provides an overview of the processing techniques developed to optimise dispersion quality, interfaces, and density. The properties of the various composite systems are discussed, with an emphasis on toughness; a comprehensive comparative summary is provided, together with a discussion of the possible toughening mechanism that may operate. Last, a range of potential applications are discussed, concluding with a discussion of the scope for future developments in the field.
Co-reporter:Boris J.C. Thomas, Milo S.P. Shaffer, Aldo R. Boccaccini
Composites Part A: Applied Science and Manufacturing 2009 Volume 40(6–7) pp:837-845
Publication Date(Web):July 2009
DOI:10.1016/j.compositesa.2009.04.006
Dense borosilicate glass matrix composites containing up to 3 wt% of multiwalled carbon nanotubes were produced by a sol–gel process. The three different silicate precursors employed (tetramethylsilane (TMOS), methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS)) yielded transparent xerogels which were subsequently crushed and densified by hot pressing at 800 °C. The dispersion of the carbon nanotubes was aided by using an organic–inorganic binder (3-aminopropyl triethoxysilane) which limited flocculation of the CNTs in the silica sol. After densification, the borosilicate glass composites containing up to 2 wt% CNTs showed significant improvements in hardness and compression strength, as well as thermal conductivity, whilst percolation effects lead to a dramatic increase in electrical conductivity above 1 wt%. This simple approach to disperse CNTs into a technical silicate glass matrix via the sol–gel process focusses specifically on the borosilicate system, but the procedure can be applied to produce other inorganic matrix composites containing CNTs.
Co-reporter:Hui Qian, Alexander Bismarck, Emile S. Greenhalgh, Gerhard Kalinka and Milo S. P. Shaffer
Chemistry of Materials 2008 Volume 20(Issue 5) pp:1862
Publication Date(Web):February 9, 2008
DOI:10.1021/cm702782j
The feasibility of reinforcing conventional carbon fiber composites by grafting carbon nanotubes (CNTs) onto the fiber surface has been investigated. Carbon nanotubes were grown on carbon fibers using the chemical vapor deposition (CVD) method. Iron was selected as the catalyst and predeposited using the incipient wetness technique before the growth reaction. The morphology of the products was characterized using scanning electron microscopy (SEM), which showed evidence of a uniform coating of CNTs on the fiber surface. Contact angle measurements on individual fibers, before and after the CNT growth, demonstrated a change in wettability that can be linked to a change of the polarity of the modified surface. Model composites based on CNT-grafted carbon fibers/epoxy were fabricated in order to examine apparent interfacial shear strength (IFSS). A dramatic improvement in IFSS over carbon fiber/epoxy composites was observed in the single fiber pull-out tests, but no significant change was shown in the push-out tests. The different IFSS results were provisionally attributed to a change of failure mechanism between the two types of tests, supported by fractographic analysis.
Co-reporter:Uroš Vukičević, Sabina (Chyła) Ziemian, Alexander Bismarck and Milo S. P. Shaffer
Journal of Materials Chemistry A 2008 vol. 18(Issue 29) pp:3448-3453
Publication Date(Web):11 Jun 2008
DOI:10.1039/B804468F
Anatase nanorods were synthesised via the non-hydrolytic condensation of TiCl4 and Ti(OPr)4 in the presence of trioctylphosphine oxide and dodecylamine as structure directing agents, to produce rod-like particles approximately 5 nm in diameter and 15 nm in length. The crystal structure was confirmed as pure anatase by Raman spectroscopy and X-ray diffraction. The as-prepared nanorods can be dispersed in organic solvents as a result of hydrophobic surface functionalities imparted during the synthesis. Subjecting nanorod suspensions in CHCl3–water mixtures to UV irradiation leads to complete photocatalytic removal of surfactants from the TiO2 surface, enabling, in turn, transfer of the nanorods into the aqueous phase. Quaternary ammonium hydroxides were used to stabilise optically clear aqueous suspensions, through a combination of electrostatic and steric repulsion between particles; dispersions of individual nanorods are a prerequisite for many technological applications. Once ‘stripped’ of their organic ligands, the nanorods can be further functionalised using, for example, aminopropyltriethoxysilane to modify the isoelectric point, dispersibility, or photocatalytic activity; these effects are demonstrated by electrophoretic and dye degradation experiments.
Co-reporter:Ben F. Cottam and Milo S. P. Shaffer
Chemical Communications 2007 (Issue 42) pp:4378-4380
Publication Date(Web):15 Aug 2007
DOI:10.1039/B709353E
Oriented arrays of both rutile and anatase nanorods have been synthesised in a two-stage process, employing multi-walled carbon nanotubes as the initial structural template.
Co-reporter:Raquel Verdejo, Steven Lamoriniere, Ben Cottam, Alexander Bismarck and Milo Shaffer
Chemical Communications 2007 (Issue 5) pp:513-515
Publication Date(Web):02 Nov 2006
DOI:10.1039/B611930A
Conventional liquid phase oxidation of multiwall carbon nanotubes (MWCNTs) using concentrated acids generates contaminating debris that should be removed using aqueous base before further reaction.
Co-reporter:Ben F. Cottam, Siva Krishnadasan, Andrew J. deMello, John C. deMello and Milo S. P. Shaffer
Lab on a Chip 2007 vol. 7(Issue 2) pp:167-169
Publication Date(Web):22 Dec 2006
DOI:10.1039/B616068A
The synthesis of one-dimensional titanium oxide nanostructures has been accelerated by performing the reaction in a microfluidic environment as opposed to a classical batch process.
Co-reporter:Michael Q. Tran, Charnwit Tridech, Alexander Alfrey, Alexander Bismarck, Milo S.P. Shaffer
Carbon 2007 Volume 45(Issue 12) pp:2341-2350
Publication Date(Web):October 2007
DOI:10.1016/j.carbon.2007.07.012
Commercially available, multi-walled carbon nanotubes grown by CVD are usually inherently entangled, but can be separated by cutting. However, most cutting methods both cause damage to the nanotubes and involve a lengthy work-up procedure. The use of abrupt, repeated exposure to oxidising conditions in air proved to be an efficient (68% yield) means of producing material with open ends, moderate functionalisation, and enhanced solvent dispersibility; the average lengths were reduced from over 5 μm to approximately 650 nm. Additionally, the character of the surface oxides can be tuned to have either an acidic or basic character by using a simple thermal treatment. These approaches could be deliberately integrated into conventional CVD processes, but also have implications for the products of standard nanotube syntheses. Raman spectroscopy and electron microscopy were used to study the impact of cutting on the intrinsic graphitic structure and the length distribution. X-ray photoelectron spectroscopy was used to determine the extent of functionalisation. The cut carbon nanotubes were dispersed in dimethylformamide (DMF), a Lewis basic solvent, and chloroform, a Lewis acidic solvent, using mild sonication. Through the use of an experimentally determined extinction coefficient (ε = 35.10 ml mg−1 cm−1), the relative dispersibility of the cut and functionalised carbon nanotubes in DMF and chloroform was determined.
Co-reporter:Aldo R. Boccaccini, Johann Cho, Judith A. Roether, Boris J.C. Thomas, E. Jane Minay, Milo S.P. Shaffer
Carbon 2006 Volume 44(Issue 15) pp:3149-3160
Publication Date(Web):December 2006
DOI:10.1016/j.carbon.2006.06.021
Electrophoretic deposition (EPD) has been gaining increasing interest as an economical and versatile processing technique for the production of novel coatings or films of carbon nanotubes (CNTs) on conductive substrates. The purpose of the paper is to present an up-to-date comprehensive overview of current research progress in the field of EPD of CNTs. The paper specifically reviews the preparation and characterisation of stable CNT suspensions, and the mechanism of the EPD process; it includes discussion of pure CNT coatings and CNT/nanoparticle composite films. A complete discussion of the EPD parameters is presented, including electrode materials, deposition time, electrode separation, deposition voltage and resultant electric field. The paper highlights potential applications of the resulting CNT and CNT/composite structures, in areas such as field emission devices, fuel cells, and supercapacitors.
Co-reporter:P. Werner;R. Verdejo;F. Wöllecke;V. Altstädt;J. K. W. Sler and;M. S. P. Shaffer
Advanced Materials 2005 Volume 17(Issue 23) pp:
Publication Date(Web):19 OCT 2005
DOI:10.1002/adma.200500709
High-performance composite foams of carbon nanofiber-reinforced poly(ether ether ketone) have been produced for the first time (see Figure). The nanofibers perform two roles: optimization of the rheological properties of the polymer melt to allow foaming and improvement of the mechanical properties of the polymer. This unique performance combination is likely to be relevant to a variety of matrices, particularly semicrystalline thermoplastics.
Co-reporter:C.A. Martin, J.K.W. Sandler, M.S.P. Shaffer, M.-K. Schwarz, W. Bauhofer, K. Schulte, A.H. Windle
Composites Science and Technology 2004 Volume 64(Issue 15) pp:2309-2316
Publication Date(Web):November 2004
DOI:10.1016/j.compscitech.2004.01.025
This paper explores the use of aligned chemical vapour deposition (CVD)-grown multi-wall carbon nanotubes as a conductive filler in an epoxy system based on a bisphenol-A resin and an amine hardener. During the production of composite samples containing 0.01 wt% nanotubes, stirring rates, resin temperatures, and curing temperatures were varied. Optical microscopy of bulk samples was used to classify the degree of nanotube agglomeration. In addition, the specific bulk conductivity of the materials was analysed by AC impedance spectroscopy. The resulting electrical properties of the composites ranged from purely dielectric behaviour to bulk conductivities of 10−3 Sm−1 and were found to depend strongly on three separate stages during processing. All samples contained individually dispersed carbon nanotubes after initial shear-intensive stirring. Negative surface charges on the nanotubes led to charge-stabilised dispersions. After the addition of the hardener, the nanotubes reaggregated upon application of elevated temperatures and/or modest shear forces. The formation of the final network depended on the curing temperature of the matrix. The experimental results are compared to previous studies on nanotube and carbon black epoxy composites and are discussed with respect to aspects of colloid theory.
Co-reporter:Martina De Marco, Foivos Markoulidis, Robert Menzel, Salem M. Bawaked, Mohamed Mokhtar, Shaeel A. Al-Thabaiti, Sulaiman N. Basahel and Milo S. P. Shaffer
Journal of Materials Chemistry A 2016 - vol. 4(Issue 15) pp:NaN5389-5389
Publication Date(Web):2016/03/03
DOI:10.1039/C5TA10311H
Single-walled carbon nanotube (SWCNT) anions can be cross-linked by a dielectrophile to form covalent, carbon-bonded organogels. Freeze-drying produces cryogels with low density (2.3 mg cm−3), high surface area (766 m2 g−1), and high conductivity (9.4 S m−1), showing promise as supercapacitor electrodes. Counterion concentration controls debundling, grafting ratio, as well as all the resulting properties.
Co-reporter:Hui Qian, Emile S. Greenhalgh, Milo S. P. Shaffer and Alexander Bismarck
Journal of Materials Chemistry A 2010 - vol. 20(Issue 23) pp:NaN4762-4762
Publication Date(Web):2010/05/04
DOI:10.1039/C000041H
The introduction of carbon nanotubes (CNTs) into conventional fibre-reinforced polymer composites creates a hierarchical reinforcement structure and can significantly improve composite performance. This paper reviews the progress to date towards the creation of fibre reinforced (hierarchical) nanocomposites and assesses the potential for a new generation of advanced multifunctional materials. Two alternative strategies for forming CNT-based hierarchical composites are contrasted, the dispersion of CNTs into the composite matrix and their direct attachment onto the primary fibre surface. The implications of each approach for composite processing and performance are discussed, along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting hierarchical composites.
Co-reporter:Arántzazu González-Campo;Katherine L. Orchard;Norio Sato;Charlotte K. Williams
Chemical Communications 2009(Issue 27) pp:NaN4036-4036
Publication Date(Web):2009/06/30
DOI:10.1039/B905353K
This communication presents a clean and efficient in situ method for the preparation of thermoset composites containing ZnO nanoparticles and/or ZnO-coated carbon nanotubes.
Co-reporter:N. J. Brown, J. Weiner, K. Hellgardt, M. S. P. Shaffer and C. K. Williams
Chemical Communications 2013 - vol. 49(Issue 94) pp:NaN11076-11076
Publication Date(Web):2013/10/21
DOI:10.1039/C3CC46203J
Colloidal solutions of ZnO–Cu nanoparticles can be used as catalysts for the reduction of carbon dioxide with hydrogen. The use of phosphinate ligands for the synthesis of the nanoparticles from organometallic precursors improves the reductive stability and catalytic activity of the system.
Co-reporter:Robert Menzel, Michael Q. Tran, Angelika Menner, Christopher W. M. Kay, Alexander Bismarck and Milo S. P. Shaffer
Chemical Science (2010-Present) 2010 - vol. 1(Issue 5) pp:NaN608-608
Publication Date(Web):2010/08/11
DOI:10.1039/C0SC00287A
High temperature activation of carbon nanotubes (CNTs) provides a new and highly versatile functionalisation strategy. The reaction allows the attachment of a wide variety of functional species onto the nanotube surface at grafting ratios between 1–8 wt%, whilst maintaining the intrinsic properties of the untreated materials. The underlying, radical-based, reaction mechanism has been established by quenching experiments and EPR studies. The distribution of the functionalised sites has been investigated at the microscopic scale using tagging reactions. The grafted products have been characterized by electron microscopy, thermal analysis (TGA), Raman spectroscopy, and inverse gas chromatography (IGC). The change in the CNT surface properties after grafting has been quantified in terms of dispersive and specific surface energies, and altered dispersibilities in a broad range of solvents. It is possible to carry out the reaction using gas phase reagents, providing a clean, efficient, and scalable methodology, relevant to a diverse range of applications.
Co-reporter:Ben F. Cottam and Milo S. P. Shaffer
Chemical Communications 2007(Issue 42) pp:NaN4380-4380
Publication Date(Web):2007/08/15
DOI:10.1039/B709353E
Oriented arrays of both rutile and anatase nanorods have been synthesised in a two-stage process, employing multi-walled carbon nanotubes as the initial structural template.
Co-reporter:A. J. Clancy, J. Melbourne and M. S. P. Shaffer
Journal of Materials Chemistry A 2015 - vol. 3(Issue 32) pp:NaN16715-16715
Publication Date(Web):2015/07/10
DOI:10.1039/C5TA03561A
Reductive dissolution is a promising processing route for single walled carbon nanotubes (SWCNTs) that avoids the damage caused by ultrasonication and aggressive oxidation whilst simultaneously allowing access to a wealth of SWCNT functionalisation reactions. Here, reductive dissolution has been simplified to a single one-pot reaction through the use of sodium naphthalide in dimethylacetamide allowing direct synthesis of SWCNT Na+ solutions. Gram quantities of SWCNTs can be dissolved at concentrations over 2 mg mL−1. These reduced SWCNT solutions can easily be functionalised through the addition of alkyl halides; reducing steric bulk of the grafting moiety and increasing polarisability of the leaving group increases the extent of functionalisation. An optimised absolute sodium concentration of 25 mM is shown to be more important than carbon to metal ratio in determining the maximum degree of functionalisation. This novel dissolution system can be modified for use as a non-destructive purification route for raw SWCNT powder by adjusting the degree of charging to dissolve carbonaceous impurities, catalyst particles and defective material, before processing the remaining SWCNTs.
Co-reporter:A. García-Trenco, E. R. White, M. S. P. Shaffer and C. K. Williams
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 12) pp:NaN4397-4397
Publication Date(Web):2016/01/28
DOI:10.1039/C5CY01994J
A simple one-pot synthetic method allows the preparation of hybrid catalysts, based on colloidal Cu/ZnO nanoparticles (NPs), used for the liquid phase synthesis of DME from syngas. The method obviates the high temperature calcinations and pre-reduction treatments typically associated with such catalysts. The hybrid catalysts are applied under typical industrially relevant conditions. The nature of the hybrid catalysts, the influence of the acid component, mass ratio between components, and Cu/Zn composition are assessed. The best catalysts comprise a colloidal mixture of Cu/ZnO NPs, as the methanol synthesis component, and γ-Al2O3, as the methanol dehydration component. These catalysts show high DME selectivity (65–70% C). Interestingly, the activity (relative to Cu content) is up to three times higher than that for the reference hybrid catalyst based on the commercial Cu/ZnO/Al2O3 methanol synthesis catalyst. The hybrid catalysts are stable for at least 20 h time-on-stream, not showing any significant sintering of the Cu0 phase. Post-catalysis, HR-TEM and STEM/EDX show that the hybrid catalysts consist of Cu0 and ZnO NPs with an average size of 5–7 nm with γ-Al2O3 particles in close proximity.
Co-reporter:Hannah S. Leese, Lata Govada, Emmanuel Saridakis, Sahir Khurshid, Robert Menzel, Takuya Morishita, Adam J. Clancy, Edward. R. White, Naomi E. Chayen and Milo S. P. Shaffer
Chemical Science (2010-Present) 2016 - vol. 7(Issue 4) pp:NaN2923-2923
Publication Date(Web):2016/01/29
DOI:10.1039/C5SC03595C
A range of carbon nanomaterials, with varying dimensionality, were dispersed by a non-damaging and versatile chemical reduction route, and subsequently grafted by reaction with methoxy polyethylene glycol (mPEG) monobromides. The use of carbon nanomaterials with different geometries provides both a systematic comparison of surface modification chemistry and the opportunity to study factors affecting specific applications. Multi-walled carbon nanotubes, single-walled carbon nanotubes, graphite nanoplatelets, exfoliated few layer graphite and carbon black were functionalized with mPEG-Br, yielding grafting ratios relative to the nanocarbon framework between ca. 7 and 135 wt%; the products were characterised by Raman spectroscopy, TGA-MS, and electron microscopy. The functionalized materials were tested as nucleants by subjecting them to rigorous protein crystallization studies. Sparsely functionalized flat sheet geometries proved exceptionally effective at inducing crystallization of six proteins. This new class of nucleant, based on PEG grafted graphene-related materials, can be widely applied to promote the growth of 3D crystals suitable for X-ray crystallography. The association of the protein ferritin with functionalized exfoliated few layer graphite was directly visualized by transmission electron microscopy, illustrating the formation of ordered clusters of protein molecules critical to successful nucleation.
Co-reporter:Ainara Garcia-Gallastegui, Diana Iruretagoyena, Mohamed Mokhtar, Abdullah M. Asiri, Sulaiman N. Basahel, Shaeel A. Al-Thabaiti, Abdulrahman O. Alyoubi, David Chadwick and Milo S. P. Shaffer
Journal of Materials Chemistry A 2012 - vol. 22(Issue 28) pp:NaN13940-13940
Publication Date(Web):2012/06/14
DOI:10.1039/C2JM00059H
Layered double hydroxides (LDHs) are promising materials for CO2 sorption, although improvements in performance are required for practical applications. In the current study, the CO2 sorption capacity and multi-cycle stability were both increased by introducing an open supporting framework of multi-walled carbon nanotubes (MWNTs). This nanostructured inert network provides a high surface area, maximizing the gas accessibility and minimizing coarsening effects. Specifically, LDH nanoparticles were precipitated directly onto MWNTs, initially oxidised to ensure a favourable electrostatic interaction and hence a good dispersion. The dependence of the structural and physical properties of the Mg–Al LDH grown on MWNT supports has been studied, using electron microscopy, X-ray diffraction, thermogravimetric analysis (TGA), and BET surface area, and correlated with the CO2 sorption capacity, established via TGA and temperature programmed desorption measurements. The use of a MWNT support was found to improve the absolute capacity and cycle stability of the hybrid adsorbent under dry conditions.
Co-reporter:Hin Chun Yau, Mustafa K. Bayazit, Joachim H. G. Steinke and Milo S. P. Shaffer
Chemical Communications 2015 - vol. 51(Issue 93) pp:NaN16624-16624
Publication Date(Web):2015/09/15
DOI:10.1039/C5CC06526G
Sonicating pure N-methyl pyrrolidone (NMP) rapidly produces contaminating organic nanoparticles, at increasing concentration with time, as investigated by AFM, as well as UV-vis, IR and NMR spectroscopies. The contamination issue affects carbon nanotube, and likely other nanomaterial, dispersions processed by sonication in organic solvents.
Co-reporter:Uroš Vukičević, Sabina (Chyła) Ziemian, Alexander Bismarck and Milo S. P. Shaffer
Journal of Materials Chemistry A 2008 - vol. 18(Issue 29) pp:NaN3453-3453
Publication Date(Web):2008/06/11
DOI:10.1039/B804468F
Anatase nanorods were synthesised via the non-hydrolytic condensation of TiCl4 and Ti(OPr)4 in the presence of trioctylphosphine oxide and dodecylamine as structure directing agents, to produce rod-like particles approximately 5 nm in diameter and 15 nm in length. The crystal structure was confirmed as pure anatase by Raman spectroscopy and X-ray diffraction. The as-prepared nanorods can be dispersed in organic solvents as a result of hydrophobic surface functionalities imparted during the synthesis. Subjecting nanorod suspensions in CHCl3–water mixtures to UV irradiation leads to complete photocatalytic removal of surfactants from the TiO2 surface, enabling, in turn, transfer of the nanorods into the aqueous phase. Quaternary ammonium hydroxides were used to stabilise optically clear aqueous suspensions, through a combination of electrostatic and steric repulsion between particles; dispersions of individual nanorods are a prerequisite for many technological applications. Once ‘stripped’ of their organic ligands, the nanorods can be further functionalised using, for example, aminopropyltriethoxysilane to modify the isoelectric point, dispersibility, or photocatalytic activity; these effects are demonstrated by electrophoretic and dye degradation experiments.
Co-reporter:Raquel Verdejo, Steven Lamoriniere, Ben Cottam, Alexander Bismarck and Milo Shaffer
Chemical Communications 2007(Issue 5) pp:NaN515-515
Publication Date(Web):2006/11/02
DOI:10.1039/B611930A
Conventional liquid phase oxidation of multiwall carbon nanotubes (MWCNTs) using concentrated acids generates contaminating debris that should be removed using aqueous base before further reaction.
Co-reporter:Robert Menzel;Ben F. Cottam;Sabina (Chyła) Ziemian
Journal of Materials Chemistry A 2012 - vol. 22(Issue 24) pp:
Publication Date(Web):2012/05/29
DOI:10.1039/C2JM30922J
TiO2 anatase nanorods were grown via the non-hydrolytic elimination reaction between TiCl4 and Ti(OiPr)4 in the presence of oleic acid. The reaction was carried out in two stages in order to separate TiOx seed nucleation at lower temperatures from nanorod growth at higher temperatures. This separation made it possible to study the crystal growth mechanism in more detail, indicating that nanorod formation occurred through a combination of atom-by-atom addition and oriented attachment of the initial seeds. The two-stage reaction approach also enabled considerably improved control of titania nanorod formation in terms of product morphology, crystallinity and uniformity. The effects of a range of reaction parameters, including reaction duration, temperature, dilution and stoichiometry, were investigated.
Co-reporter:Natasha Shirshova, Alexander Bismarck, Shuaijin Carreyette, Quentin P. V. Fontana, Emile S. Greenhalgh, Per Jacobsson, Patrik Johansson, Maciej J. Marczewski, Gerhard Kalinka, Anthony R. J. Kucernak, Johan Scheers, Milo S. P. Shaffer, Joachim H. G. Steinke and Malte Wienrich
Journal of Materials Chemistry A 2013 - vol. 1(Issue 48) pp:NaN15309-15309
Publication Date(Web):2013/11/11
DOI:10.1039/C3TA13163G
‘Structural electrolytes’ retain the desirable mechanical characteristics of structural (epoxy) resins whilst introducing sufficient ionic conductivity to operate as electrolytes in electrochemical devices. Here, a series of ionic liquid–epoxy resin composites were prepared to identify the optimum system microstructure required to achieve a high level of multifunctionality. The ionic conductivity, mechanical properties, thermal stability and morphology of the cured epoxy based structural electrolytes were studied as a function of phase composition for three fully formulated high performance structural epoxy systems. At only 30 wt% of structural resin and 70 wt% of ionic liquid based electrolyte, stiff monolithic plaques with thicknesses of 2–3 mm were obtained with a room temperature ionic conductivity of 0.8 mS cm−1 and a Young's modulus of 0.2 GPa. This promising performance can be attributed to a long characteristic length scale spinodal microstructure, suggesting routes to further optimisation in the future.
Co-reporter:Takuya Morishita, Adam J. Clancy and Milo S. P. Shaffer
Journal of Materials Chemistry A 2014 - vol. 2(Issue 36) pp:NaN15028-15028
Publication Date(Web):2014/07/22
DOI:10.1039/C4TA02349H
In bulk applications, it is essential that graphene sheets disperse individually in solvents or matrices, and therefore, suitable functionalisation regimes are crucially important. Here, isolated, highly soluble, alkyl-grafted graphenes were synthesised by reacting exfoliated Na-reduced graphite intercalation compounds (GIC) with alkyl halides. In this reaction, efficient exfoliation of the Na-reduced GICs into individually-dispersed negatively-charged graphenes provides accessible surface area for grafting. Increasing the alkyl chain length leads to large decrease of the grafting ratio (GR), demonstrating that steric factors also play an important role. However, optimising the Na concentration (C/Na ratio) in the reaction was very effective for improved exfoliation and increased GR. The X-ray diffraction measurements suggest that particular C/Na ratios (C/Na = ∼12) led to full exfoliation, by balancing total charge and charge condensation effects and that the GR can be significantly increased even in the case of long alkyl chains (eicosyl chains), corresponding to a high solubility of 37 μg ml−1 and high yield in o-dichlorobenzene. Moreover, the absolute Na concentration is the critical parameter, with the same optimum (∼0.01 M) for exfoliation and grafting of GIC at all graphite concentrations; it was possible to graft even at high graphite concentration (0.3 M (3.6 mg ml−1)) successfully.
Co-reporter:Mustafa K. Bayazit, Stephen A. Hodge, Adam J. Clancy, Robert Menzel, Shu Chen and Milo S. P. Shaffer
Chemical Communications 2016 - vol. 52(Issue 9) pp:NaN1937-1937
Publication Date(Web):2015/12/10
DOI:10.1039/C5CC08726K
Gold nanoparticles (AuNPs) can be evenly deposited on single-walled carbon nanotubes (SWCNTs) via the reduction of the highly stable complex, chloro(triphenylphosphine) gold(I), with SWCNT anions (‘nanotubides’). This methodology highlights the unusual chemistry of nanotubides and provides a blueprint for the generation of many other hybrid nanomaterials.
Co-reporter:Stephen A. Hodge, Mustafa K. Bayazit, Karl S. Coleman and Milo S. P. Shaffer
Chemical Society Reviews 2012 - vol. 41(Issue 12) pp:NaN4429-4429
Publication Date(Web):2012/04/19
DOI:10.1039/C2CS15334C
Single-walled carbon nanotubes (SWNTs) are a fundamental family of distinct molecules, each bearing the possibility of different reactivities due to their intrinsically distinct chemical properties. SWNT syntheses generate a heterogeneous mixture of species with varying electronic character, lengths, diameters and helicities, (n,m), as well as other amorphous, graphitic and metal catalyst impurities. In recent years, selective syntheses and post-synthetic separation strategies have advanced, driven by the requirement for pure SWNTs displaying particular features. Covalent surface modifications are widely-used to adapt SWNTs for specific applications with modified solubility, compatibility and specific functionalities. In many cases, such reactions have been found to be selective, illuminating the fundamentally distinct chemistry of each (n,m) species. This differential reactivity has found immediate utility in facilitating the sorting of nanotubes according to specific diameter, electronic properties and, most importantly, helicity. In this tutorial review, we discuss a wide range of selective reactions, the mechanisms that are thought to govern selectivity, and the challenges of separating, characterising and regenerating the modified SWNTs.
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2_b.png)
![3,5,9-Trioxa-4-phosphapentacosan-1-aminium,4-hydroxy-N,N,N-trimethyl-10-oxo-7-[(1-oxohexadecyl)oxy]-, inner salt, 4-oxide](http://img.cochemist.com/ccimg/2700/2644-64-6.png)
![3,5,9-Trioxa-4-phosphapentacosan-1-aminium,4-hydroxy-N,N,N-trimethyl-10-oxo-7-[(1-oxohexadecyl)oxy]-, inner salt, 4-oxide](http://img.cochemist.com/ccimg/2700/2644-64-6_b.png)
![Phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2-(chloromethyl)oxirane and 4,4'-methylenebis[benzenamine]](/data/chemimg/58700/40364-42-9.png)
![Phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2-(chloromethyl)oxirane and 4,4'-methylenebis[benzenamine]](/data/chemimg/58700/40364-42-9_b.png)
