Co-reporter:Yi-Jia Zhao, Kesong Miao, Zhengtao Zhu, and Li-Juan Fan
ACS Sensors June 23, 2017 Volume 2(Issue 6) pp:842-842
Publication Date(Web):May 29, 2017
DOI:10.1021/acssensors.7b00245
Fluorescence sensing of amine in aqueous solution is challenging. The various basicity and chemical structures of amines may lead to poor selectivity in aqueous solution, and selective fluorescence detection of primary aromatic amine is rarely reported. This paper presents design and synthesis of a fluorescent conjugated polymer for rapid and selective sensing of aromatic amines in aqueous solution. The fluorescent conjugated polymer, poly[fluorenyl-alt-p-phenyleneethynylene] with pendant carboxylic acid groups and long alky chains, is synthesized via palladium-catalyzed Sonogashira coupling reaction. The fluorescence of the polymer is selectively quenched by the aromatic amines in aqueous solution, whereas the aliphatic amines enhance the fluorescence of the polymer. The high selectivity to the aromatic amines, particularly to the environmentally important p-phenylenediamine, likely originates from the amplified π–π fluorescence quenching synergized by amine and carboxylic acid interaction. Our results demonstrate an effective material design strategy that may be extended to fluorescence sensing of other aromatic compounds.Keywords: amine sensor; aqueous solution; conjugated polymer; fluorescence quenching; primary aromatic amines;
Co-reporter:Hong Chen, Rong-liang Ma, Yun Chen, and Li-Juan Fan
ACS Applied Materials & Interfaces February 8, 2017 Volume 9(Issue 5) pp:
Publication Date(Web):January 12, 2017
DOI:10.1021/acsami.6b15951
Poly(p-phenylenevinylene) (PPV) nanoparticles in aqueous colloidal solution have been prepared via a modified Wessling method, with the addition of surfactant. The fluorescent colloidal solution was used as the developing solution to develop the fingerprints on different substrates. The developing process was accomplished simply by immersing the substrates into developing solution and then taking out, followed by rinsing with deionized water. The initial study about the fingerprints on the adhesive tapes showed that the developing solution is very effective in fluorescence development on both fresh and aged visible fingerprints; and such an effect was negligibly affected by treating the fingerprints with water or other organic solvents, whether before developing or after. Further study on latent fingerprints (LFPs) demonstrated that PPV nanoparticles in colloidal solution have high sensitivity in developing fingerprints to give very clearly fluorescent patterns. At least 6 months of storage of the colloidal solution did not reduce the developing effect; and each developing solution (3.6 mg/mL, 5.0 mL) can be used to develop at least 30 fingerprints without sacrificing the legibility of the pattern. The preliminary mechanism investigation suggested that selectivity achieved toward the ridge of the fingerprint is very likely due to the affinity between PPV molecules and oily secretions of the fingerprints. Digital magnification of the developed fingerprints provided more details about the fingerprint.Keywords: adhesive tapes; aqueous colloidal solution; fluorescence development; latent fingerprint; poly(p-phenylenevinylene) nanoparticles;
Co-reporter:Ya Shao;Hong Chen;Wei Zhang;Yi-jia Zhao
Journal of Materials Science 2017 Volume 52( Issue 7) pp:3906-3916
Publication Date(Web):07 December 2016
DOI:10.1007/s10853-016-0651-8
This study advanced a strategy for preparing fluorescent spectrally encoded microspheres through introducing rare earth element europium (Eu) and organic dye rhodamine 6G (R6G) onto the porous substrate polymer spheres. The size and monodispersity of the microspheres were controlled by selecting the appropriate substrate spheres. Various combinations of three different types of fluorophores, the substrate spheres as a polymer fluorophore, together with Eu and R6G as inorganic and organic fluorophores afford large encoding capacity based on emission spectra. After optimization of the preparative process, three series of fluorescent spheres with ten combinations of intensities at different wavelengths from two binary encoding systems and fifteen combinations from one ternary encoding system were prepared. Such combinations (or codes) were obtained by exciting the spheres at the same wavelength. The preparative process was found to have no significant influence on the size and surface morphology, as shown in the microscopic study. The color variation in the macroscopic and microscopic images under excitation was consistent with emission spectra. In addition, these spheres were found to have good stability against water washing and thermal treatment.
Co-reporter:Hong Chen, Yun Chen, Li-Juan Fan
Journal of Controlled Release 2017 Volume 259(Volume 259) pp:
Publication Date(Web):10 August 2017
DOI:10.1016/j.jconrel.2017.03.110
Co-reporter:Kesong Miao;Heng Zhang;Lijuan Sun;Zhengtao Zhu
Journal of Materials Chemistry C 2017 vol. 5(Issue 20) pp:5010-5017
Publication Date(Web):2017/05/25
DOI:10.1039/C7TC01195D
With the aim of detecting glutaraldehyde (GA) in wastewater released from hospitals and other sites, fluorescent poly(phenyleneethynylene) with pendant protonated primary amino groups (PPE-NH3+) was synthesized and characterized. The fluorescence of the conjugated polyelectrolyte PPE-NH3+ in aqueous solution changed upon addition of aldehydes. Among many commonly encountered aldehydes including formaldehyde (FA) and glutaraldehyde (GA), GA displayed the strongest quenching of the fluorescence of PPE-NH3+. The quenching efficiency reached above 85% with 1 mM of GA and the limit of detection (LOD) was 0.49 μM. The fluorescence quenching mechanism was discussed. GA, as a dialdehyde, could react with amino groups on different polymer chains simultaneously, and thus might result in more efficient chain aggregation and quenching. Finally, this sensory system was demonstrated to be very effective in detecting GA in real water samples from a water tap in our lab, a pond on the campus, Dushu lake and a river nearby a hospital.
Co-reporter:Tian Qiu, Yun Chen, Jing Song, and Li-Juan Fan
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 15) pp:8260
Publication Date(Web):April 3, 2015
DOI:10.1021/acsami.5b01434
This study is to develop a method for preparing fluorescent microspheres with steady and strong fluorescence as well as the surface functionality for bioconjugation. Layer-by-layer technique was employed to introduce poly(phenylenevinylene) (PPV) precursor, diazoresin (DAR), and polyanion, including poly(acrylic acid) (PAA) and poly(sodium-p-styrenesulfonate) (PSS), onto the substrate polystyrene-divinylbenzene microspheres with sulfonic groups on the surface (SPSDVB). The conversion of PPV precursor into fluorescent PPV as well as the cross-linking reaction between DAR and polyanion, were accomplished simultaneously in the following thermal treatment. After optimizing the DAR concentration, the selection of polyelectrolytes and the coating sequence, the cross-linked multilayer coated PPV microspheres, SPSDVB-(PPV/PSS/DAR/PAA) spheres, were prepared. These spheres were found to have uniform size with a clear core–shell structure and display even and strong fluorescence, based on the characterization by flow cytometry, microscopy, and photophysics. They were found to be stable and highly resistant to common solvents and even “dissociation agent”, as well as possess good thermal stability and photostability. The feasibility of conjugating biomolecules on the surface of spheres was also demonstrated.Keywords: bioconjugation; cross-linking; flow cytometry; fluorescent microsphere; layer-by-layer;
Co-reporter:Xiaoqian Xu, Kesong Miao, Yun Chen, and Li-Juan Fan
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 14) pp:7759
Publication Date(Web):March 25, 2015
DOI:10.1021/acsami.5b00991
Fluorescent poly(phenylenevinylene) (PPV)/poly(vinyl alcohol) (PVA) fibrous membrane was prepared via electrospinning of PPV precursor and PVA aqueous solution followed by thermal elimination. Further cross-linking produced the cross-linked membrane PPV/CPVA. Both PPV/PVA and PPV/CPVA membranes were found to have similar morphology and photophysics. These membranes showed a great fluorescence quenching response to aromatic solvents and a much smaller response to other organic solvents. Water also effectively quenched the fluorescence of PPV/PVA but not that of PPV/CPVA. This was attributed to un-cross-linked PVA being able to dissolve in water and the cross-linking improving the resistance of the membrane toward water. The sensing behavior was found to have good reversibility. The contact angle study showed that addition of only about 1% of PPV into the matrix reduced the hydrophilicity of the membrane significantly, suggesting that the PPV chains would be located at the surface of the fibers. X-ray photoelectron spectroscopy (XPS) investigation further confirmed such surface enrichment of PPV in the binary polymer blends. The PPV chain on the surface facilitated the π–π interaction between the polymer backbones and the aromatic molecules, thus leading to good selectivity and fast response of the two fibrous membranes toward aromatic solvents.Keywords: aromatic solvent; electrospinning; fluorescence sensing; poly(phenylenevinylene); polymer blend;
Co-reporter:Yun Chen, Hong Chen, Heng Zhang, and Li-Juan Fan
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 48) pp:26709
Publication Date(Web):November 10, 2015
DOI:10.1021/acsami.5b08695
A series of poly(p-phenylenevinylene) (PPV)-coated microspheres with varied fluorescent emission colors have been prepared by controlling the average length of the conjugated segments on the polymer backbone. A modified Wessling method was used for preparing PPV with different conjugation segments. The labile sulfonium groups of the initial polymer precursor of PPV (pre-PPV) were partly substituted by relatively stable methoxyl groups. A series of precursors with different degrees of substitution were prepared by controlling the time of reaction; these precursors were adsorbed onto the negatively charged substrate spheres. Subsequently, heterogeneous thermal treatment eliminated the sulfonium groups selectively to form the conjugated segments on the PPV backbone with varied average conjugation lengths. Under UV exposure, the as-prepared PPV-coated microspheres displayed emission colors ranging from blue to green; a 65 nm shift in the emission maximum was observed in the fluorescence spectra. The gradual color change in emission of spheres was also confirmed in a confocal microscopy study. Further characterizations indicated that these microspheres possessed clear core–shell structure, good monodispersity in size, smooth surfaces, uniform emission, and superior thermal and photo stability. Flow cytometry measurements indicated that these spheres have very different patterns of intensity combination from four-signal receiving channels. The simple method reported herein, which can effectively and efficiently tune the emission color of the fluorescent microspheres, is a promising approach for preparation of microspheres used as encoded signal carrier in flow cytometry and other high-throughput techniques.Keywords: color tuning; conjugation length; flow cytometry; fluorescent microspheres; poly(p-phenylenevinylene)
Co-reporter:Yun Chen, Tian Qiu, Wei Zhao and Li-Juan Fan
Polymer Chemistry 2015 vol. 6(Issue 9) pp:1576-1583
Publication Date(Web):09 Dec 2014
DOI:10.1039/C4PY01615G
Poly(p-phenylenevinylene) (PPV) fluorescent microspheres were prepared in two steps. First, the positive sulfonium-salt PPV precursor (pre-PPV) was coated onto the surface of negatively charged polymer substrate spheres; second, the pre-PPV was converted into fluorescent PPV via a heterogeneous catalytic thermal elimination process. A series of fluorescent microspheres were obtained with different apparent colors and different fluorescence emissions simply by varying the elimination temperature. A spectroscopy study showed that, compared to the direct solid elimination, the spheres obtained via catalyzed elimination gave a very large variation in the emission, such as a larger shift in the wavelength, and more delicate spectra profiles with peaks and shoulders. Overlapping of the signals from blue channels and green channels in the confocal microscopy study gave a direct view of the gradual change from the blue emission to the green emission for the spheres obtained at elimination temperatures from 40 °C to 120 °C. Flow cytometry measurements showed that spheres obtained at different temperatures exhibit different combinations of the intensities from four different receiving channels. These PPV spheres were also demonstrated to have a smooth surface, monodispersity, a clear core–shell structure, thermal stability and photostability.
Co-reporter:Jing Song, Tian Qiu, Yun Chen, Wei Zhang, Li-Juan Fan
Journal of Colloid and Interface Science 2015 Volume 452() pp:190-198
Publication Date(Web):15 August 2015
DOI:10.1016/j.jcis.2015.04.024
The layer-by-layer (LBL) technique was employed for preparing fluorescent microspheres with a core–shell structure by the alternating adsorption of positively charged poly(p-phenylenevinylene) precursor (pre-PPV) and the polyanions onto polymer substrate spheres, followed by the thermal elimination to convert pre-PPV into fluorescent poly(p-phenylenevinylene) (PPV). Weak polyelectrolytes poly(acrylic acid) (PAA) (usually in a partly ionized form) and strong polyelectrolytes poly(sodium-p-styrenesulfonate) (PSS) were used as the anions to space the PPV layers and reduce the fluorescence self-quenching. Flow cytometry, combined with spectroscopy and microscopy, were used to study the structure and photophysical properties of the resulting microspheres. Optimization of the processing factors was carried out. PAA and PSS as weak and strong polyelectrolytes, respectively, displayed very different influence on the final emission of the spheres. Such difference was attributed to different inherent characteristics of PAA and PSS after detailed investigation in many aspects. In addition, the fluorescent spheres were found to have excellent photostability and thermal stability.
Co-reporter:Wei Zhang, Yun Chen, Ya Shao and Li-Juan Fan
Journal of Materials Chemistry A 2014 vol. 2(Issue 32) pp:5249-5255
Publication Date(Web):16 Jun 2014
DOI:10.1039/C4TB00561A
Fluorescent microspheres are prepared by attaching self-assembled polydiacetylene (PDA) vesicles with carboxyl side groups onto the substrate amino-modified poly(glycidylmethacrylate) (APGMA) microspheres. The characterization by SEM, confocal microscopy and flow cytometry demonstrated that the final resulting microspheres are highly uniform both in size (with a diameter of 5 μm) and in fluorescence emission (coefficient of variance < 3%). The Brunauer–Emmett–Teller (BET) surface area of these spheres is 114 m2 g−1. In addition, there are evenly distributed pores with an average size of 20.6 nm on the spheres. These spheres are found to have good thermal stability and photostability, and do not suffer from fluorophore leaching. Fluorescein isothiocyanate (FITC) labelled bovine serum albumin (BSA) as a representative biomolecule can be easily attached onto the fluorescent microspheres. All these characteristics possessed by the APGMA–PDA spheres allow them to be directly used as carriers of biomolecules in lab-on-a-chip immunoassay systems.
Co-reporter:Haibo Xu, Wei Wu, Yun Chen, Tian Qiu, and Li-Juan Fan
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 7) pp:5041
Publication Date(Web):March 10, 2014
DOI:10.1021/am5001272
Pattern-based strategy is an emerging field of interest for effective sensing applications. Seven different conjugated polymers from combinatorial synthesis were combined into a sensor array, and seven metal cations were selected as representative analytes. The response patterns for each cation were constructed by collecting the individual fluorescence responses from seven polymers in the array. Each ion owns a characteristic pattern. Some of them have similar modes of response with subtle differences, while some patterns are distinctively different. The family/period the metal cations belong to and the charges/electronic configurations they possess may account for such similarity/difference in the pattern.Keywords: combinatorial synthesis; conjugated polymer; fluorescence; response pattern; sensor array;
Co-reporter:Lisha Wang, Fengcai Li, Minde Yao, Tian Qiu, Weihua Jiang, Li-Juan Fan
Reactive and Functional Polymers 2014 Volume 82() pp:66-71
Publication Date(Web):September 2014
DOI:10.1016/j.reactfunctpolym.2014.06.002
The introduction of reactive groups on the surface of monodispersed highly crosslinked poly(styrene–divinylbenzene) (PSDVB) microspheres was accomplished in two steps. The first step requires immobilizing the initiating groups by a Friedel–Craft acylation between 2-chloropropionyl chlorides and the phenyl groups on the spheres. The second step requires the atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) to obtain spheres (PSDVB-g-PGMA) with epoxy groups on the surface. To demonstrate the feasibility of introducing functionality, the epoxy groups were ring-opened by ethylenediamines, resulting in spheres with amino functionality (PSDVB-g-PGMAEDA). The final spheres were found to have an adsorption capacity of 0.66 mmol/g in the Cu2+ adsorption experiments, as a preliminary application study.Graphical abstract
Co-reporter:Minhua Cao, Lin Zhou, Xiaoqian Xu, Si Cheng, Jian-Lin Yao and Li-Juan Fan
Journal of Materials Chemistry A 2013 vol. 1(Issue 31) pp:8942-8949
Publication Date(Web):16 May 2013
DOI:10.1039/C3TA11435J
SERS has been applied to monitor different types of catalytic reactions on the surface of metal NPs in recent years, which requires bifunctional metal structures with plasmonic properties as well as catalytic activity. Monitoring catalytic reactions with SERS technology in previous reports was usually performed in metal solution, using metal electrodes or on a glass/silica substrate with an immobilized metal. Here, we report a general approach for preparing novel SERS-active substrates which are used to monitor catalytic reactions. The polyacrylonitrile (PAN)/Ag–M (M = Au or Pd) bimetallic nanofibrous mats are prepared through galvanic replacement reactions of Ag with Au or Pd on the surface of electrospun PAN/Ag nanofibers. The composition of Ag and Au or Pd could be tuned by changing the concentration of the metal solution used for replacement. The PAN/Ag0.60Au0.40 and PAN/Ag0.90Pd0.10 bimetallic nanofibrous mats exhibit both excellent SERS and catalytic activities. The reduction of 4-nitrothiophenol (4-NTP) to the corresponding to 4-aminothiophenol (4-ATP) on PAN/Ag0.60Au0.40 and PAN/Ag0.90Pd0.10 bimetallic nanofibrous mats are monitored by SERS technology. The SERS signals of the reaction intermediate, 4,4′-dimercapto-azobenzene(4,4′-DMAB), are observed as the reaction proceeds with time.
Co-reporter:Wei Zhang, Haibo Xu, Yun Chen, Si Cheng, and Li-Juan Fan
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 11) pp:4603
Publication Date(Web):May 20, 2013
DOI:10.1021/am401099s
Aiming to develop pH-paper-like current sensing materials, we prepared irreversible electrochromic PDA-PMMA/graphene composites. The composites exhibited an excellent linear relationship between critical responsive currents and the amount of graphene in the system. In these composites, PDA acted as the electrochromic material and graphene as the conductive matrix. The presence of PMMA not only ensured mechanical performance but also made the color change more obvious to be observed by the naked eye.Keywords: electrochromic material; graphene; polydiacetylene; semiquantative; sensing;
Co-reporter:Jing Song, Wei Zhang, Kesong Miao, Hongling Zeng, Si Cheng, and Li-Juan Fan
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 10) pp:4011
Publication Date(Web):May 6, 2013
DOI:10.1021/am4005336
Poly(phenylenevinylene)/polyimide (PPV/PI) and poly(phenylenevinylene)/ polymethylmethacrylate (PPV/PMMA) fibrous membranes without any deliberately introduced receptors were prepared as fluorescence sensing materials through electrospinning, followed by thermal treatment. Both of these membranes displayed higher sensitivity toward most cations compared to the corresponding spin-coated films. PPV/PMMA membranes were more sensitive than PPV/PI membranes toward Cu2+ and Fe3+. About 4.5 fold of intensity enhancement upon 20 nM of Cu2+, 80% of quenching upon 20 nM of Fe3+ with fast response and simple regeneration were realized for PPV/PMMA membrane. The preliminary investigation into the mechanism revealed that the properties of the polymer matrix and thermal treatment of the membrane played important roles in the sensing performance.Keywords: electrospinning; fluorescence; poly(phenylenevinylene); receptor-free; sensing;
Co-reporter:Shangli Wang;Wei Zhao;Jing Song;Si Cheng
Macromolecular Rapid Communications 2013 Volume 34( Issue 1) pp:102-108
Publication Date(Web):
DOI:10.1002/marc.201200560
Abstract
A strategy to prepare stable monodispersed fluorescent microspheres is developed by modifying the Wessling method to synthesize poly(p-phenylenevinylene) (PPV) on the surface of a highly crosslinked polymer core. The positively charged PPV polymer precursors (pre-PPV) are adsorbed onto the core with negative charges on the surface and then the insoluble fluorescent PPVs form after thermal elimination. Each individual sphere is found to possess a very smooth surface with an even distribution of fluorescence by microscopic techniques. Very small coefficient of variance (CV) values of emission intensity (<4.0%) and size (<2.3%) are realized for microspheres prepared in the same batch. The spheres are demonstrated to have good thermal stability and photostability.
Co-reporter:Wei Wu;Haibo Xu;Dezhi Shen;Tian Qiu
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 7) pp:1636-1644
Publication Date(Web):
DOI:10.1002/pola.26535
Abstract
A new coil-rod-coil copolymer is synthesized via Sonogashira coupling using one-step methodology. The copolymer PEG-OEPETPT-PEG constitutes of poly(ethylene glycol) (PEG) as the coil block, and oligo[p-(ethynylenephenyleneethynylene)-alt-(thienylenepyridazinylenethienylene)] (OEPETPT) as the rod segment. The conjugated polymer PEPETPT with the same conjugated building blocks is also synthesized for comparison. The structures of both polymers are confirmed by NMR, combined with other characterizations. PEG-OEPETPT-PEG has a 12 nm blue-shift in the emission maximum compared with that of PEPETPT, and a higher quantum yield of fluorescence in THF. PEG-OEPETPTE-PEG tolerates up to 20% water content in H2O/THF mixed solvent without significantly changing the emission wavelength and intensity, while the fluorescence of PEPETPT is dramatically quenched by a very small quantity of water. Further photophysical studies about these two polymers indicate that the introduction of PEG coils onto the conjugated block retards the water-induced-aggregation and therefore improves the fluorescence stability of PEG-OEPETPT-PEG. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Co-reporter:Wei Zhao;Jing Song;Ya Shao;Wei Zhang;Aaron Au
Macromolecular Chemistry and Physics 2012 Volume 213( Issue 18) pp:1913-1921
Publication Date(Web):
DOI:10.1002/macp.201200235
Abstract
A series of PPV films with different fluorescent emission colors are prepared using a facile approach. Modified from the conventional Wessling route, the labile sulfonium groups in the polymer precursor (pre-PPV) are partly substituted to various degrees by relatively stable methoxy groups, followed by a regular thermal elimination step to obtain PPV. Different chemical structures among these films are confirmed by IR and photophysical studies. Two film-preparative processes are compared and the films are studied by SEM and confocal fluorescent microscopy. From the same polymer precursor, different preparative processes result in PPV films with different morphologies but the same photophysical properties.
Co-reporter:Minhua Cao;Si Cheng;Xiaozhao Zhou;Zhengxu Tao
Journal of Polymer Research 2012 Volume 19( Issue 1) pp:
Publication Date(Web):2012 January
DOI:10.1007/s10965-011-9810-4
A facile approach to prepare electrospun poly(vinly alcohol) (PVA) nanofibers with high concentration of gold nanoparticles (Au NPs) on the fibers, had been developed. These PVA/Au nanofibers could be used as flexible surface-enhanced Raman scattering (SERS) substrates. Relatively high concentration of PVA aqueous solution (10 wt %) was used as the stabilizing agent for gold salt precursor, as well as the starting solution for electrospinning. This method was demonstrated to be effective to prepare high-concentration-gold nanoparticles without aggregation and precipitation by reducing high concentration of gold salt in the presence of PVA aqueous solution. SEM and TEM images showed that both the amount and the size of Au NPs which embedded in PVA nanofibers, increased with increasing the gold salt content, while the gap between the adjacent NPs decreased. Raman spectra showed an apparent enhancement in the signal of 4-mercaptobenzoic acid (4-MBA) molecules pre-absorbed from its ethanol solution onto the PVA/Au nanofibers. The high SERS activity to 4-MBA in solution with a relatively low concentration (10−6 M), could be mainly attributed to the reduced gap of Au NPs.
Co-reporter:Shangli Wang;Wei Zhao;Xiaoqian Xu;Si Cheng ;Lijuan Fan
Chinese Journal of Chemistry 2011 Volume 29( Issue 10) pp:2175-2181
Publication Date(Web):
DOI:10.1002/cjoc.201180377
Abstract
A series of poly(p-phenylenevinylene)s (PPVs) with good solubility were synthesized from thermal elimination of precursor poly(2,5-didodecyloxy-p-phenylenevinylene) at different temperature via Wessling method. The polymer photophysics were influenced by the thermal elimination condition, which was consistent with NMR and IR characterizations. The additional absorption peak at longer wavelength and the red-shifted emission maximum both in solution and in film, for PPVs obtained at high elimination temperature, indicated the existence of longer conjugated blocks in these systems. The emission maximum for drop-cast film (436 nm) for PPV obtained under 200°C (PPV200) was 16 nm blue shifted to the spin-coated films (452 nm) or 29 nm to the solution (465 nm). The SEM study showed drop-cast film had the morphology of isolated conjugated particles in the matrix while blurry linear structure was found for spin-coated film, which was consistent with the photophysics. The discussion about this difference was carried out based on the consideration of the flexibility of the polymer chains and different conjugated length of PPV in different states.
Co-reporter:Dezhi Shen, Lisha Wang, Zhenxing Pan, Si Cheng, Xiulin Zhu, and Li-Juan Fan
Macromolecules 2011 Volume 44(Issue 4) pp:1009-1015
Publication Date(Web):January 28, 2011
DOI:10.1021/ma102311n
A conjugated polyelectrolyte with symmetrically assembled hydrophilic and hydrophobic side groups along the backbone has been successfully synthesized and demonstrated significant photophysical tunability with 65 nm of wavelength shift and 10-fold of intensity enhancement for the emission maximum, through solvent composition adjustment. The highest fluorescence quenching effect (I/I0 = 148) toward 10 μM of Fe3+ was achieved in the solution having a THF/H2O ratio of 30/70, which could be attributed to a delicate balance among the influencing factors for the fluorescence quenching systems, the initial fluorescence, the rate of energy migration, and the accessibility of the receptors. The amplified symmetrical aggregation−nonaggregation inversion and the asymmetrical cation sensitivity across the whole range of H2O/THF composition were consistent with the molecular design.
Co-reporter:Dezhi Shen;Zhenxing Pan;Haibo Xu;Si Cheng;Xiulin Zhu ;Lijuan Fan
Chinese Journal of Chemistry 2010 Volume 28( Issue 7) pp:1279-1283
Publication Date(Web):
DOI:10.1002/cjoc.201090221
Abstract
A conjugate polymer poly[p-(phenyleneethylene)-alt-(phenyleneazophenyleneethylene)] (PPEPAPE) containing azobenzene building block in the polymer backbone was synthesized via Sonogashira cross-coupling of 4,4′-diiodoazobenzene and 1,4-diethynyl-2,5-didodecyloxybenzene. All the monomers and the resulting polymer were well characterized. The polymer had a relatively high molecular weight and showed very good solubility (≧10 mg/mL) in common organic solvents. The photophysics of this polymer in solution and in film was investigated. The surface morphology of the films was studied by scanning electron microscope (SEM) and the relationship between the morphology and absorbance was discussed. This polymer has good film-forming property, broad absorbance and no emission, which might make it a good candidate for the photovoltaic material in the solar cell.
Co-reporter:Si Cheng, Dezhi Shen, Xinsheng Zhu, Xingguang Tian, Dongying Zhou, Li-Juan Fan
European Polymer Journal 2009 Volume 45(Issue 10) pp:2767-2778
Publication Date(Web):October 2009
DOI:10.1016/j.eurpolymj.2009.06.021
A controlled in situ sol–gel synthesis combined with the electrospinning technique and postspun imidization was applied in the fabrication of polyimide/silica hybrid nonwoven nanofiberous fabrics with excellent thermal and mechanical performance. The nanofiberous fabrics were prepared by electrospinning of the solution of tetraethoxysilane (TEOS) and polyamic acid (PAA). The different silica contents in the fabrics were achieved by varying the amount of TEOS while fitting the solid content of PAA. The final polyimide/silica fabrics was obtained after imidization of PAA and gelation of silica phase simultaneously accomplished through a step-wise heating process. Some specific IR techniques and other characterizations indicated the successful incorporation of the silicon dioxide (SiO2) into the PI matrix and the relatively even distribution of the SiO2 in the fabrics. An increase of 133 °C in the decomposition temperature and 4-fold enhancement of the ultimate tensile strength were achieved for the hybrids with a 6.58 wt.% of SiO2 content, compared to the pure PI fabric. The excellent performance could be attributed to the good compatibility between the polyimide and silica, and good adhesion among the fibers, which resulted from the controlled TEOS hydrolysis and the simultaneous imidization and gelation process.
Co-reporter:Lisha Wang, Fengcai Li, Minde Yao, Tian Qiu, Weihua Jiang, Li-Juan Fan
Reactive and Functional Polymers (September 2014) Volume 82() pp:66-71
Publication Date(Web):1 September 2014
DOI:10.1016/j.reactfunctpolym.2014.06.002
The introduction of reactive groups on the surface of monodispersed highly crosslinked poly(styrene–divinylbenzene) (PSDVB) microspheres was accomplished in two steps. The first step requires immobilizing the initiating groups by a Friedel–Craft acylation between 2-chloropropionyl chlorides and the phenyl groups on the spheres. The second step requires the atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) to obtain spheres (PSDVB-g-PGMA) with epoxy groups on the surface. To demonstrate the feasibility of introducing functionality, the epoxy groups were ring-opened by ethylenediamines, resulting in spheres with amino functionality (PSDVB-g-PGMAEDA). The final spheres were found to have an adsorption capacity of 0.66 mmol/g in the Cu2+ adsorption experiments, as a preliminary application study.Graphical abstractDownload full-size image
Co-reporter:Wei Zhang, Yun Chen, Ya Shao and Li-Juan Fan
Journal of Materials Chemistry A 2014 - vol. 2(Issue 32) pp:NaN5255-5255
Publication Date(Web):2014/06/16
DOI:10.1039/C4TB00561A
Fluorescent microspheres are prepared by attaching self-assembled polydiacetylene (PDA) vesicles with carboxyl side groups onto the substrate amino-modified poly(glycidylmethacrylate) (APGMA) microspheres. The characterization by SEM, confocal microscopy and flow cytometry demonstrated that the final resulting microspheres are highly uniform both in size (with a diameter of 5 μm) and in fluorescence emission (coefficient of variance < 3%). The Brunauer–Emmett–Teller (BET) surface area of these spheres is 114 m2 g−1. In addition, there are evenly distributed pores with an average size of 20.6 nm on the spheres. These spheres are found to have good thermal stability and photostability, and do not suffer from fluorophore leaching. Fluorescein isothiocyanate (FITC) labelled bovine serum albumin (BSA) as a representative biomolecule can be easily attached onto the fluorescent microspheres. All these characteristics possessed by the APGMA–PDA spheres allow them to be directly used as carriers of biomolecules in lab-on-a-chip immunoassay systems.
Co-reporter:Minhua Cao, Lin Zhou, Xiaoqian Xu, Si Cheng, Jian-Lin Yao and Li-Juan Fan
Journal of Materials Chemistry A 2013 - vol. 1(Issue 31) pp:NaN8949-8949
Publication Date(Web):2013/05/16
DOI:10.1039/C3TA11435J
SERS has been applied to monitor different types of catalytic reactions on the surface of metal NPs in recent years, which requires bifunctional metal structures with plasmonic properties as well as catalytic activity. Monitoring catalytic reactions with SERS technology in previous reports was usually performed in metal solution, using metal electrodes or on a glass/silica substrate with an immobilized metal. Here, we report a general approach for preparing novel SERS-active substrates which are used to monitor catalytic reactions. The polyacrylonitrile (PAN)/Ag–M (M = Au or Pd) bimetallic nanofibrous mats are prepared through galvanic replacement reactions of Ag with Au or Pd on the surface of electrospun PAN/Ag nanofibers. The composition of Ag and Au or Pd could be tuned by changing the concentration of the metal solution used for replacement. The PAN/Ag0.60Au0.40 and PAN/Ag0.90Pd0.10 bimetallic nanofibrous mats exhibit both excellent SERS and catalytic activities. The reduction of 4-nitrothiophenol (4-NTP) to the corresponding to 4-aminothiophenol (4-ATP) on PAN/Ag0.60Au0.40 and PAN/Ag0.90Pd0.10 bimetallic nanofibrous mats are monitored by SERS technology. The SERS signals of the reaction intermediate, 4,4′-dimercapto-azobenzene(4,4′-DMAB), are observed as the reaction proceeds with time.
Co-reporter:Kesong Miao, Heng Zhang, Lijuan Sun, Zhengtao Zhu and Li-Juan Fan
Journal of Materials Chemistry A 2017 - vol. 5(Issue 20) pp:NaN5017-5017
Publication Date(Web):2017/04/25
DOI:10.1039/C7TC01195D
With the aim of detecting glutaraldehyde (GA) in wastewater released from hospitals and other sites, fluorescent poly(phenyleneethynylene) with pendant protonated primary amino groups (PPE-NH3+) was synthesized and characterized. The fluorescence of the conjugated polyelectrolyte PPE-NH3+ in aqueous solution changed upon addition of aldehydes. Among many commonly encountered aldehydes including formaldehyde (FA) and glutaraldehyde (GA), GA displayed the strongest quenching of the fluorescence of PPE-NH3+. The quenching efficiency reached above 85% with 1 mM of GA and the limit of detection (LOD) was 0.49 μM. The fluorescence quenching mechanism was discussed. GA, as a dialdehyde, could react with amino groups on different polymer chains simultaneously, and thus might result in more efficient chain aggregation and quenching. Finally, this sensory system was demonstrated to be very effective in detecting GA in real water samples from a water tap in our lab, a pond on the campus, Dushu lake and a river nearby a hospital.
