Increased efforts have recently been devoted to developing high-energy-density flexible supercapacitors for their practical applications in portable and wearable electronics. Although high operating voltages have been achieved in fiber-shaped asymmetric supercapacitors (FASCs), low specific capacitance still restricts the further enhancement of their energy density. This article specifies a facile and cost-effective method to directly grow three-dimensionally well-aligned zinc–nickel-cobalt oxide (ZNCO)@Ni(OH)2 nanowire arrays (NWAs) on a carbon nanotube fiber (CNTF) with an ultrahigh specific capacitance of 2847.5 F/cm3 (10.678 F/cm2) at a current density of 1 mA/cm2, These levels are approximately five times higher than those of ZNCO NWAs/CNTF electrodes (2.10 F/cm2) and four times higher than Ni(OH)2/CNTF electrodes (2.55 F/cm2). Benefiting from their unique features, we successfully fabricated a prototype coaxial FASC (CFASC) with a maximum operating voltage of 1.6 V, which was assembled by adopting ZNCO@Ni(OH)2 NWAs/CNTF as the core electrode and a thin layer of carbon coated vanadium nitride (VN@C) NWAs on a carbon nanotube strip (CNTS) as the outer electrode with KOH poly(vinyl alcohol) (PVA) as the gel electrolyte. A high specific capacitance of 94.67 F/cm3 (573.75 mF/cm2) and an exceptional energy density of 33.66 mWh/cm3 (204.02 μWh/cm2) were achieved for our CFASC device, which represent the highest levels of fiber-shaped supercapacitors to date. More importantly, the fiber-shaped ZnO-based photodetector is powered by the integrated CFASC, and it demonstrates excellent sensitivity in detecting UV light. Thus, this work paves the way to the construction of ultrahigh-capacity electrode materials for next-generation wearable energy-storage devices.Keywords: coaxial asymmetric supercapacitor; core−shell nanostructure; wearable electronics; Zinc−nickel-cobalt oxide;

Electrically conductive adhesives (ECAs) can be regarded as one of the most promising materials to replace tin/lead solder. However, relatively low conductivity seriously restricts their applications. In the present study, we develop an effective method to decrease the bulk electrical resistivity of ECAs. KI or KBr is added to replace the lubricant and silver oxide layers on silver flakes and to form photosensitive silver halide. After exposure to sunlight, silver halide can photodecompose into silver nanoparticles that will sinter and form metallic bonding between/among flakes during the curing process of ECAs, which would remarkably reduce the resistivity. The modified micro silver flakes play a crucial role in decreasing the electrical resistivity of the corresponding ECAs, exhibiting the lowest resistivity of 7.6 × 10–5 Ω·cm for 70 wt % loaded ECAs. The obtained ECAs can have wide applications in the electronics industry, where high conductance is required.Keywords: electrically conductive adhesives; low electrical resistivity; silver flakes; sintering phenomenon; surface photosensitization;

The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm2 in a three-electrode system. Benefiting from their intriguing structural features, we successfully fabricated a prototype asymmetric coaxial FSS (ACFSS) with a maximum operating voltage of 1.8 V. From core to shell, this ACFSS consists of a CNT fiber core coated with VN@C NWAs as the negative electrode, Na2SO4 poly(vinyl alcohol) (PVA) as the solid electrolyte, and MnO2/conducting polymer/CNT sheets as the positive electrode. The novel coaxial architecture not only fully enables utilization of the effective surface area and decreases the contact resistance between the two electrodes but also, more importantly, provides a short pathway for the ultrafast transport of axial electrons and ions. The electrochemical results show that the optimized ACFSS exhibits a remarkable specific capacitance of 213.5 mF/cm2 and an exceptional energy density of 96.07 μWh/cm2, the highest areal capacitance and areal energy density yet reported in FSSs. Furthermore, the device possesses excellent flexibility in that its capacitance retention reaches 96.8% after bending 5000 times, which further allows it to be woven into flexible electronic clothes with conventional weaving techniques. Therefore, the asymmetric coaxial architectural design allows new opportunities to fabricate high-performance flexible FSSs for future portable and wearable electronic devices.Keywords: asymmetric supercapacitors; Carbon nanotubes; coaxial; fibers; vanadium nitride;

Nanocrystalline graphene/graphite hybrids all carbon transparent electrodes were fabricated from photoresist with a photolithography method by the carbonization and graphitization of the aromatic molecules in the photoresist. The sheet resistance and transmittance of the hybrids transparent electrodes can be easily optimized by modulating the photoresist grid size and gridline width. The optimized hybrids were fabricated on quartz for graphene glass that exhibits excellent properties for heating device. They were also engaged on Si with a thin oxide layer by a catalyst-free and direct growth method for high-performance Schottky junction photodetectors that exhibit remarkable properties on photodetection with the photovoltage responsivity exceeding up to 105 V/W under the incident light power of 0.05 μW, which make it suitable as weak-light-signal detectors. This study should be helpful on the various applications of catalyst-free, cost-effective, transparent, electrically and thermally conductive graphene.

•We used a cost-effective method to fabricate stretchable FASCs with a maximum operating voltage of 1.8 V using MnO2@PEDOT:PSS@OCNTF as positive electrode and MoS2@CNTF as negative electrode.•Due to the synergy of the MnO2@PEDOT:PSS@OCNTF and MoS2@CNTF, the optimized stretchable FASC device exhibits a remarkable specific capacitance of 278.6 mF/cm2 and a superior energy density of 125.37 μWh/cm2.•The device possesses outstanding stretchability in that it retained 92% of its capacitance after stretching at a strain of 100% for 3,000 cycles.Fiber-shaped asymmetric supercapacitors (FASCs) have attracted considerable attention due to their potential application in portable and wearable electronics. Although high stretchability have been achieved in fiber-shaped supercapacitors, low energy density severely restricts their practical applications. This study develops a simple and cost-effective method to synthesize highly capacitive hierarchically-structured MnO2@PEDOT:PSS@oxidized carbon nanotube fibers (MnO2@PEDOT:PSS@OCNTF) positive electrode and flower-like MoS2 nanosheets@CNTF (MoS2@CNTF) negative electrode. Their intriguing structural features allowed us to successfully fabricate a prototype stretchable FASC with a maximum operating voltage of 1.8 V. Due to the synergy of the MnO2@PEDOT:PSS@OCNTF and MoS2@CNTF, the optimized stretchable FASC device exhibits a remarkable specific capacitance of 278.6 mF/cm2 and a superior energy density of 125.37 μWh/cm2, which are higher than those of any reported state-of-the-art fiber-shaped supercapacitors. In addition, the device possesses outstanding stretchability, as it maintains a capacitance retention of 92% after stretching at a strain of 100% for 3000 cycles. These stretchable FASCs have great potential as power sources for next-generation portable and wearable electronics.Download high-res image (352KB)Download full-size image

A series of high-performance all-solid-state, lightweight, and flexible asymmetric supercapacitors (ASC) were prepared using cabbage-like ZnCo2O4 as the positive electrode material, porous VN nanowires as the negative electrode material, and flexible carbon nanotube film (CNTF) as the collector. Excellent electrochemical performance was achieved with an areal capacitance of 789.11 mF cm−2 for the positive electrode and 400 mF cm−2 for the negative electrode. The assembled all-solid-state flexible ASC device possessed a specific capacitance of 196.43 mF cm−2, large voltage window of 1.6 V, and a volume energy density of 64.76 mW h cm−3. Moreover, the assembled device exhibited good cycling stability with 87.9% initial capacitance retention after 4000 cycles with the coulombic efficiency remaining close to 100%. In addition, the capacitance retention reached 95.7% after 2000 bending cycles, indicating its good flexible and mechanical stability.

Polymer infiltrating filler-network has been actively researched recently to obtain composite materials with enhanced thermal conductivities. However, the long infiltration time blocks its wide application. In this study, we prepared hexagonal boron nitride (h-BN)/poly(vinyl alcohol) (PVA) composite by combining polymer infiltration with filler diffusion through the polymer to reduce infiltration time and form heat conduction paths. Base on this process, the maximum thermal conductivities of the obtained h-BN/PVA composites were 1.63 W/m·K and 8.44 W/m·K along the through-plane and in-plane directions, respectively. In addition, the composites displayed excellent heat dissipation performance when attached on top of a light emitting diode (LED) light strip. The research results indicate our approach is facile and capable of fabricating high performance thermal interface materials.

A facile strategy was reported to fabricate vertically oriented and densely packed hexagonal boron nitride (h-BN)/epoxy (EP) composites via vacuum filtration followed by slicing up. This route is simple and high-efficient without special treatment and/or chemical modification. A high through-plane thermal conductivity of 9 W/m K was obtained at a h-BN loading of 44 vol% in the composites. Laser flash thermal analyzer (LFA) and thermogravimetric analysis (TGA) results indicated that the through-plane thermal conductivity of the composites increased with the fraction of the fillers. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests indicated that h-BN microplatelets were mainly vertically oriented in the composites. In addition, as-made composites showed good mechanical strength. Therefore, it has great potential as thermal interface materials, which is very important in the thermal management of electronics, especially in electronic packages where electrical insulation is required.

In this work, we develop an easy, convenient and effective high-temperature short-time annealing method to treat silver fillers through decomposing the silver oxide on the surface into silver nanoparticles and also in-situ paralyzing part of the surface lubricants to reduce the length of the tunneling distance between neighboring silver flakes. The modified micro silver flakes play a significant role in improving the electrical conductivity of the corresponding electrically conductive adhesives (ECAs), exhibiting the lowest resistivity of 1.28 × 10−4 Ω·cm at 70 wt% filler loading. This work suggests that the high-temperature short-time annealing strategy can greatly enhance the electrical conductivity of as-treated silver flakes based ECAs, which will allow them to be widely used in electronic packaging.

Light-weight materials with superior thermal and electrical transport properties have received much attention for effective thermal management. In this study, we develop a three-dimensional (3D) hybrid hierarchical structure with carbon nanotube (CNT) intercalated graphene sheets by thermal annealing of carbon nanotube/graphene oxide (CNT/GO) films. In this full-carbon architecture, CNTs are employed to bridge adjacent graphene sheets to facilitate the phonon propagation and prevent the corrugation of graphene layers during thermal treatment. The as-obtained carbon nanotube/graphene (CNT/G) film with 15 wt% CNTs content exhibits ultrahigh in-plane thermal conductivity of 1388.7 W/mK and favorable electric conductivity of 1.7 × 105 S/m. The mechanisms of the enhanced thermal conductivities of the hybrid films are then analyzed by theoretical simulation. These films could be useful in thermal management for next generation commercial portable electronics.

•BNNTs can be synthesized by nitridation of the mixture of B2O3 and boron.•The B2O3/B precursor can avoid the introduction of metal impurities.•The concentration of B2O3 has a significant influence on the formation of BNNTs.Boron nitride nanotubes (BNNTs) can be grown on stainless steel by annealing a mixture of diboron trioxide (B2O3) and boron (B) at 1200–1300 °C under ammonia (NH3). In previously reported boron oxide chemical vapor deposition methods for the synthesis of BNNTs, diboron dioxide (B2O2) is generated in situ by the reaction of boron and metal oxides. In this study, we directly used a mixture of B2O3 and boron as boron sources, thereby, avoiding the use of metal containing species in the starting material. The concentration of B2O3 significantly influenced the formation, quality and quantity of BNNTs.BNNTs are synthesized by the nitridation of the mixture of B2O3 and boron with stainless steel as a catalyst.Download high-res image (115KB)Download full-size image

A high-performance, all-solid-state hybrid supercapacitor (HSC) device was assembled successfully. The ZnCo2O4 nanowire array (NA)/carbon nanotube film (CNTF) positive electrode materials and the assembled device possess areal specific capacitances of 1.019 F cm−2 and 158.08 mF cm−2, respectively. A supernal volume energy density of 49.5 mWh cm−3 was obtained when the voltage window increased to 1.5 V. Moreover, the assembled HSC device exhibited good cycling stability with 90.7% initial capacitance retention after 6000 cycles, and the coulombic efficiency remained near 100%.The assembled all-solid-state asymmetric supercapacitor device possess excellent cycle stability and supernal volume energy density.Download high-res image (260KB)Download full-size image

Boron nitride nanotubes (BNNTs) have outstanding properties and potential applications. However, the fundamental issue regarding the growth mechanism remains an open question. Herein, we design a bimetallic catalyst that dissolves B and N simultaneously, which has been proved to be key for BNNT growth.

Emerging fiber-shaped supercapacitors have been considered as promising new-state energy storage devices for next-generation wearable electronics. However, the limited energy densities arising from the small specific capacitance and low operating voltage severely restrict their practical application. Here, we develop a facile and effective method to directly grow dandelion-like molybdenum–nickel–cobalt ternary oxide (MNCO) nanowire arrays (NWAs) on carbon nanotube fiber (CNTF) with a high specific capacitance of 490.7 F cm−3 (1840 mF cm−2) at a current density of 1 mA cm−2. Benefiting from the three-dimensional nanostructure, high conductivity and excellent pseudocapacitance properties, we successfully fabricate a fiber-shaped asymmetric supercapacitor (FASC) with a maximum operating voltage of 1.6 V, which is assembled by twisting a MNCO/CNTF positive electrode and thin carbon-coated VN NWAs on CNTF negative electrode together with KOH/poly(vinyl alcohol) (PVA) as the gel electrolyte. The optimized FASC delivers a remarkable specific capacitance of 62.3 F cm−3 (233.7 mF cm−2) and an exceeding energy density of 22.2 mW h cm−3 (83.1 μW h cm−2). Additionally, it exhibits outstanding flexibility with capacitance retention maintained at 90.2% after bending 3500 times. Thus, the high performance MNCO/CNTF electrode opens a new avenue to fabricate high-performance FASCs for next-generation wearable energy storage devices.

Correction for ‘CoPt/CeO2 catalysts for the growth of narrow diameter semiconducting single-walled carbon nanotubes’ by Lei Tang et al., Nanoscale, 2015, DOI: 10.1039/c5nr05616k.

Flexible conductive adhesive could be used in flexible device electronic packaging. In this study, carbon nanotubes (CNTs) were used as one-dimensional conductive scaffolds to construct effective electrical networks among the silver flakes in electrically conductive adhesives (ECAs) for saving noble metal fillers and reducing the cost because CNTs used as conductivity fillers could bridge the neighboring silver flakes to accelerate the electron transport. The electrical, mechanical, and thermal properties have been enhanced after adding CNTs. The electrical conductivity increased 85.6% after 4.5 wt% CNT added into the 50 wt% Ag TPU adhesives. In addition, after the Ag flakes modified by succinic acid (SA), the electrical conductivity has also been improved. The development of highly conductive, flexible, and low cost ECAs will allow them to be widely used in flexible electronic devices packaging in the future.

Edge-oriented MoS2 nanopetals complexed with basal-oriented MoS2 thin films have been mildly grown through a simple atmospheric pressure chemical vapor deposition (APCVD) process with the reaction of MoO3 and S. Dense nanopetals with hexagonal structures exposed numerous chemically reactive edge sites. The roles of growth temperature, time and S/MoO3 mass ratio have been carefully investigated to tune the morphology and density of the as-grown products. Importantly, the carbon nanotube (CNT) films were used as substrates for growing MoS2 nanopetals. The MoS2/CNT composites, used directly as working electrodes, showed remarkable and stable electrocatalytic activity in the hydrogen evolution reaction (HER), as manifested with a low onset overpotential of ∼100 mV and a small Tafel slope of 49.5 mV per decade. The development of the MoS2/CNT electrode provides a promising way to fabricate other multifunctional electrodes.

•As-grown boron nitride nanotubes (BNNTs) BNNTs have an absorption band edge of 6.12 eV.•Low-pressure chemical vapor deposition was capable of high quality BNNTs synthesis.•Mg–Fe–O species may act as the catalysts.Direct deposition of high purity and quality boron nitride nanotubes (BNNTs) on Si substrate were obtained using low pressure chemical vapor deposition (LPCVD). We find Fe–Mg–O species may act as catalysts for growing BNNTs. This synthesis process conforms to vapor–liquid–solid (VLS) growth mechanism. As-grown BNNTs also show a large optical energy band gap of 6.12 eV, approaching to hexagonal phase BN single crystals. Meanwhile, as-grown BNNTs exhibit an intense UV-emission band located at 345 nm and a weak deep band at 237 nm. Their optoelectronic properties make them have promising for future nanoscale deep-UV light emitting devices.Graphical abstract

One of the largest obstacles for Ag based electrically conductive adhesives (ECAs), as an alternative for Pb-containing solders in electronic packaging, is that the conductivity of ECAs is lower than that of solders due to the limited physical contact area between/among conductive fillers and the insulated organic lubricant and metal oxide layers on the surface of the conductive fillers. What’s more, the high cost of Ag fillers is also restricting the wide use of Ag based ECAs. In this study, Ag-coated-Cu flakes were chosen as a substitute for Ag flakes to reduce the cost. At the same time, the coating of Cu with an Ag layer could protect the Cu-based fillers from oxidation and corrosion. A mixture of weak reducing agents and substituting agents was selected to treat the Ag-coated-Cu flakes to increase the conductivity of the Ag-coated-Cu based ECAs. During the treatment process, the weak reducing agents can reduce the metal oxides on the filler surfaces, enabling more metallic contacts. Meanwhile, the substituting agents can partially remove or replace the long chain fatty acid lubricants on the metal flakes, improving the electron tunneling between/among neighboring flakes. As such, the multiple effects of the reducing agents and substituting agents can improve the conductivity of the ECAs. By using an appropriate amount of terephthalaldehyde and iodine treated Ag-coated-Cu flakes, the resistivity was reduced to as low as 1.28 × 10−4 Ω cm for the ECA with 75 wt% content of treated fillers, which is comparable to that of commercially available Ag-filled ECAs (×10−4 Ω cm). This work suggests that a surface chemical method can enhance the electrical conductivity of metal filler based ECAs.

Efficient nanoprobes for fluorescent and magnetic resonance multimodal imaging (MRI/FI) are in high demand in bioimaging. Herein, a nanoprobe with fluorescent gold nanoclusters (NCs) and magnetic iron oxide composite materials (Fe3O4@AuNCs) was prepared for dual bioimaging. The AuNCs were synthesized using the glutathione (GSH) template. The hydrophobic Fe3O4 magnetic nanoparticles (MNPs) were capped with cetyltrimethyl ammonium bromide (CTAB) to obtain hydrophilic Fe3O4 MNPs. Subsequently, the Fe3O4@AuNCs were prepared by the adsorption of Fe3O4–CTAB on the GSH–AuNCs through electrostatic attraction. The resultant Fe3O4@AuNCs, having an average size of 13.5 nm, can be readily dispersed in water, which displayed a strong red fluorescence (λEm = 650 nm) with a quantum yield of 4.3%. Confocal laser scanning microscopy studies proved that the Fe3O4@AuNCs have good photostability and low cytotoxicity to 293T cells. The magnetic properties of Fe3O4@AuNCs showed that this material was a T2-based contrast agent for MRI with a transverse relaxivity r2 of 20.4 mM−1 S−1. Furthermore, the signal intensity of the T2-weighted MRI decreased with an increase in the concentration. The dual optical and magnetic properties of the synthesized Fe3O4@AuNCs were applicable to dual fluorescence and MR-based imaging.

For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 ± 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition, electronic transport measurements also confirm that the Ion/Ioff ratio is mainly in the order of ∼103. This work provides an effective strategy for the facile fabrication of narrow diameter distributed s-SWNTs, which will be beneficial to fundamental research and the broad application of SWNTs for future nanoelectronics.

Millimeter-to-centimeter scale vertically aligned carbon nanotube (VACNT) arrays are widely studied because of their immense potential in a range of applications. Catalyst control during chemical vapor deposition (CVD) is key to maintain the sustained growth of VACNT arrays. Herein, we achieved ultrafast growth of VACNT arrays using Fe/Al2O3 catalysts by ethanol-assisted two-zone CVD. One zone was set at temperatures above 850 °C to pyrolyze the carbon source and the other zone was set at 760 °C for VACNT deposition. By tuning synthesis parameters, up to 7 mm long VACNT arrays could be grown within 45 min, with a maximal growth rate of ∼280 μm/min. Our study indicates that the introduction of alcohol vapor and separation of growth zones from the carbon decomposition zone help reduce catalyst particle deactivation and accelerate the carbon source pyrolysis, leading to the promotion of VACNT array growth. We also observed that the catalyst film thickness did not significantly affect the CNT growth rate and microstructures under the conditions of our study. Additionally, the ultralong CNTs showed better processability with less structural deformation when exposed to solvent and polymer solutions. Our results demonstrate significant progress towards commercial production and application of VACNT arrays.

Carbon membranes have been extensively applied in gas separation field, and the cost and performance of membranes strongly rely on the properties of the substrate material. In this study, effective nanoporous carbon membranes were prepared by pencil coating of the macroporous ceramics, followed by carbonization treatment of polyfurfuryl alcohol (PFA) coated on the pencil-modified ceramics substrates. The decoration of the macroporous ceramics substrates with pencil effectively repairs surface defects and decreases surface roughness, and greatly prevents PFA from penetrating into the ceramics substrates during pyrolysis. The as-prepared carbon membranes showed high gas permeability and permselectivity properties. This work provides an efficient method to fabricate nanoporous carbon membranes with enhanced gas separation performance.

The layer numbers of graphene for graphene based transparent conductive films are crucial. An appropriate number of graphene layers would provide excellent electrical conductivity along with high transparency. Herein, we demonstrated a facile and scalable technique to grow graphene with controllable layers on copper foil substrates using the etching effect of H2 in atmospheric pressure chemical vapor deposition (APCVD), and studied the influence of H2 etching on the properties of graphene transparent conductive films. The etching of formed multi-layer graphene (MLG, 12–14 layers) for Cu substrates assists the formation of few-layer graphene (FLG, 2–3 layers). These as-obtained graphene can be used as high performance transparent conductors, which show improved tradeoff between conductivity and transparency: the transmittance of 96.4% at 550 nm with sheet resistance of ∼360 Ω sq−1, and the transmittance of 86.7% at 550 nm with sheet resistance of ∼142 Ω sq−1. They could be used as high performance transparent conductors in the future.

Temperature measurement in biology and medical diagnostics, along with sensitive temperature probing in living cells, is of great importance; however, it still faces significant challenges. Metal nanoclusters (NCs) with attractive luminescent properties may be promising candidates to overcome such challenges. Here, a novel one-step synthetic method is presented to prepare highly fluorescent copper NCs (CuNCs) in ambient conditions by using glutathione (GSH) as both the reducing agent and the protective layer preventing the aggregation of the as-formed NCs. The resultant CuNCs, with an average diameter of 2.3 nm, contain 1–3 atoms and exhibit red fluorescence (λem = 610 nm) with high quantum yields (QYs, up to 5.0%). Interestingly, the fluorescence signal of the CuNCs is reversibly responsive to the environmental temperature in the range of 15–80 °C. Furthermore, as the CuNCs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable measurements over the physiological temperature range of 15–45 °C with the use of the confocal fluorescence imaging method. In view of the facile synthesis method and attractive fluorescence properties, the as-prepared CuNCs may be used as photoluminescence thermometers and biosensors.

The first critical step in making vertically aligned carbon nanotube (VACNT)-based thermal interface materials is to transfer the VACNTs on a large scale. Although VACNTs have been transferred by several methods, they were only transferred inadvertently in most cases. Here we report well-controlled weak-oxidation-assisted transfer of VACNTs. Specifically, after a short time of weak oxidation, we found that VACNTs could be easily detached from the native growth substrates, and thus, a freestanding VACNT film was obtained. Then the VACNTs could be assembled onto specific substrates for its real applications. More importantly, the repeated growth–transfer synthesis of VACNT arrays can be realized in one batch by introducing an additional process of weak oxidation in chemical vapor deposition, which makes the strategy more effective. Surprisingly, no degradation in the quality was observed before and after the weak oxidation according to thermogravimetric analysis and Raman spectra of VACNTs. Enhanced thermal and mechanical properties were achieved after reactive ion etching (RIE) and subsequent metallization of the surfaces of the VACNTs, and this might be due to the removal of impurities such as amorphous carbon and entangled CNTs by RIE. These findings provide an efficient approach for transferring VACNTs, which is important for the application of VACNTs in thermal management.

Carbon nanotube (CNT) arrays show great promise in developing anisotropic thermal conductive composites for efficiently dissipating heat from high-power devices along thickness direction. However, CNT arrays are always grown on some substrates and liable to be deformed and broken into pieces during transfer and solution treatment. In the present study, we intentionally synthesized well-crystallized and large-diameter (∼80 nm) multiwalled CNT (MWCNT) arrays by floating catalyst chemical vapor deposition (FCCVD) method. Such arrays provided high packing density and robust structure from collapse and crack formation during post solution treatment and therefore favored to maintain original thermal and electrical conductive paths. Under optimized condition, the CNT arrays can be transferred into flexible composite films. Furthermore, the composite film also exhibited excellent thermal conductivity at 8.2 W/(m·K) along thickness direction. Such robust, flexible, and highly thermal conductive composite film may enable some prospective applications in advanced thermal management.Keywords: carbon nanotube array; crack-free; flexible; highly thermal conductive; scalable transfer;

In this work, we developed a deposition-growth-densification process to produce high density vertically aligned carbon nanotube (VACNT) array. The key to increase the density of VACNT array was the liquid-induced densification process, which not only gave the VACNT array densely packed structure, but also exposed as much substrate as possible for later VACNT growth. During the process, the cycling of catalyst deposition, CVD growth and densification process made new VACNT array continuously grown on the substrate exposed in the liquid-induced process. The density of VACNT array was increased gradually and controllably by altering the cyclic times. For now, a CNT filling factor of 30.84% was achieved. The engineering of the density and the compatibility with other techniques made it promising for the applications of carbon nanotube.

A series of high-performance all-solid-state, lightweight, and flexible asymmetric supercapacitors (ASC) were prepared using cabbage-like ZnCo2O4 as the positive electrode material, porous VN nanowires as the negative electrode material, and flexible carbon nanotube film (CNTF) as the collector. Excellent electrochemical performance was achieved with an areal capacitance of 789.11 mF cm−2 for the positive electrode and 400 mF cm−2 for the negative electrode. The assembled all-solid-state flexible ASC device possessed a specific capacitance of 196.43 mF cm−2, large voltage window of 1.6 V, and a volume energy density of 64.76 mW h cm−3. Moreover, the assembled device exhibited good cycling stability with 87.9% initial capacitance retention after 4000 cycles with the coulombic efficiency remaining close to 100%. In addition, the capacitance retention reached 95.7% after 2000 bending cycles, indicating its good flexible and mechanical stability.

Efficient nanoprobes for fluorescent and magnetic resonance multimodal imaging (MRI/FI) are in high demand in bioimaging. Herein, a nanoprobe with fluorescent gold nanoclusters (NCs) and magnetic iron oxide composite materials (Fe3O4@AuNCs) was prepared for dual bioimaging. The AuNCs were synthesized using the glutathione (GSH) template. The hydrophobic Fe3O4 magnetic nanoparticles (MNPs) were capped with cetyltrimethyl ammonium bromide (CTAB) to obtain hydrophilic Fe3O4 MNPs. Subsequently, the Fe3O4@AuNCs were prepared by the adsorption of Fe3O4–CTAB on the GSH–AuNCs through electrostatic attraction. The resultant Fe3O4@AuNCs, having an average size of 13.5 nm, can be readily dispersed in water, which displayed a strong red fluorescence (λEm = 650 nm) with a quantum yield of 4.3%. Confocal laser scanning microscopy studies proved that the Fe3O4@AuNCs have good photostability and low cytotoxicity to 293T cells. The magnetic properties of Fe3O4@AuNCs showed that this material was a T2-based contrast agent for MRI with a transverse relaxivity r2 of 20.4 mM−1 S−1. Furthermore, the signal intensity of the T2-weighted MRI decreased with an increase in the concentration. The dual optical and magnetic properties of the synthesized Fe3O4@AuNCs were applicable to dual fluorescence and MR-based imaging.

One of the largest obstacles for Ag based electrically conductive adhesives (ECAs), as an alternative for Pb-containing solders in electronic packaging, is that the conductivity of ECAs is lower than that of solders due to the limited physical contact area between/among conductive fillers and the insulated organic lubricant and metal oxide layers on the surface of the conductive fillers. What’s more, the high cost of Ag fillers is also restricting the wide use of Ag based ECAs. In this study, Ag-coated-Cu flakes were chosen as a substitute for Ag flakes to reduce the cost. At the same time, the coating of Cu with an Ag layer could protect the Cu-based fillers from oxidation and corrosion. A mixture of weak reducing agents and substituting agents was selected to treat the Ag-coated-Cu flakes to increase the conductivity of the Ag-coated-Cu based ECAs. During the treatment process, the weak reducing agents can reduce the metal oxides on the filler surfaces, enabling more metallic contacts. Meanwhile, the substituting agents can partially remove or replace the long chain fatty acid lubricants on the metal flakes, improving the electron tunneling between/among neighboring flakes. As such, the multiple effects of the reducing agents and substituting agents can improve the conductivity of the ECAs. By using an appropriate amount of terephthalaldehyde and iodine treated Ag-coated-Cu flakes, the resistivity was reduced to as low as 1.28 × 10−4 Ω cm for the ECA with 75 wt% content of treated fillers, which is comparable to that of commercially available Ag-filled ECAs (×10−4 Ω cm). This work suggests that a surface chemical method can enhance the electrical conductivity of metal filler based ECAs.