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NH3 gas sensors with good sensing performance including wide detection range at room temperature are highly desirable for a large variety of applications. In this work, multi-walled carbon nanotubes grafted with sodium polystyrenesulfonate (PSSNa-MWCNTs) are prepared via a controlled radical polymerization and show good dispersibility in water. The composite of polypyrrole with PSSNa-MWCNTs (PPy/PSSNa-MWCNT) is prepared by in situ vapor phase polymerization of pyrrole to fabricate NH3 gas sensors. Effects of the content of PSSNa-MWCNTs, the concentration of the oxidant, polymerization time and temperature on the gas sensing properties of the composite are investigated at room temperature. It is revealed that the composite shows much higher response magnitude than the single components. Under optimal conditions, PPy/PSSNa-MWCNT exhibits very wide detection range from 5 to 2000 ppm, and good sensing linearity over 5–20 ppm and 20–100 ppm, respectively. Moreover, the electrical responses of the composite towards NH3 gas are fast (response and recovery time to 1000 ppm NH3 gas are 16.7 s and 143.6 s, respectively), reproducible and highly selective. The interactions between PPy and MWCNTs promote the charge transfer in the composite, leading to good sensing performance and exhibiting a synergetic effect.

Harmless and breathable flexible humidity sensor has important applications in continuous and real-time detection of human physiological activities. In this work, with hydrophobic poly (vinylidene fluoride) (PVDF) membrane as both the template and substrate and cetyltrimethylammonium bromide as a structure regulator, polyaniline (PANI) was unilaterally deposited on a PVDF microporous membrane to facilely fabricate a single-sided integrated flexible humidity sensor (IFHS). Such IFHS is featured with unique micro/nano structure and good air permeability. Moreover, it exhibits good humidity sensing properties at room temperature including fast response, small hysteresis and stable response even under bending deformation. The flexible sensor could realize non-contact monitoring of human respiration and speaking activities. Unilateral deposition of PANI and good breathability of IFHS avoids direct contact between PANI and human skin, thus averting harms to human and minimizing the deterioration of humidity sensing properties of PANI layer. The simple method is universal to the preparation of single-sided, integrated, breathable, nontoxic and fast response wearable humidity sensors based on PANI and hydrophobic microporous polymer membranes, offering useful references for the construction of advanced flexible sensors.

Formation of heterostructure and nanostructure is promising approach to improving the photocatalytic activity of TiO2 based photocatalysts. In this work, MoS2@TiO2@poly(methyl methacrylate) (PMMA) was prepared by freeze drying of hydrothermally treated electrospun PMMA nanofibers containing titanium n-butoxide and MoS2 nanosheets. As-prepared nanocomposite revealed a 3D nanofiber network structure with high specific surface (83.6 m2/g), in which MoS2 nanosheets loaded with TiO2 nanoparticles were distributed on the surface of PMMA fibers. MoS2@TiO2@PMMA showed better photocatalytic performance than MoS2@PMMA, TiO2@PMMA, MoS2@TiO2 and MoS2@P25@PMMA towards the photodegradation of methyl orange (MO) under UV illumination. Typically, MoS2@TiO2@PMMA (100 mg) could degrade MO (10 mg/L, 100 mL) completely in 40 min under UV irradiation, revealing good photocatalytic activity. Moreover, the nanocomposite could be facilely recovered by filtration, and maintain almost the same photocatalytic activity after cycling tests for ten times, indicating excellent stability and recyclability. The enhanced photocatalytic performance of the nanocomposite might relate to the heterostructure between MoS2 and TiO2 to suppress the recombination of photo-induced charge, and the 3D hierarchical nanoweb structure to afford large specific surface area and high density of active sites.

Organic semiconductors show great potentials for applications in photocatalysis to provide solutions for environmental remediation and energy harvesting. Herein, we report the preparation and photocatalytic characteristics of a small-molecule organic semiconductor of pyromellitic diimide (PD). The one-pot heat-induced imidization reaction of pyromellitic dianhydride and 2,4,6-triaminopyrimidine obtained PDs with different phase and crystal structures. The crystalline grains of PD (c-PD), which is composed of layered constituents with π-π stacking structure, effectively photodegraded a series of dyes including methyl blue, methyl orange, orange Ⅱ sodium salt and sulforhodamine B under UV illumination. Moreover, c-PD is featured with dual selective photodegradation behaviors in favor of both azo dyes and cationic dyes in their respective mixtures with non-azo dyes and anionic dyes, which has not been reported before. The preferential photodegradation of the azo dyes might relate to their enhanced π-π interactions with c-PD. In comparison, the selective photodegradation of the cationic dyes is ascribed to preferential adsorption of the dyes due to electrostatic attractions between opposite charges. The work provides new approaches for developing advanced photocatalysts with selective photocatalytic behaviors for controlled treatment of waste water by photocatalysis.

Crosslinked and quaternized poly(4-vinylpyridine) (QC-P4VP) nanofibers have been fabricated via electrospinning followed by reaction with 1-4-dibromobutane. Subsequent decoration of the nanofibers with Ag nanoparticles by in-situ reduction obtained a nanostructured composite humidity sensing material. The nanofibers and the composites were characterized by FT-IR and scanning electron microscopy. It was found that the morphology and humidity sensing properties of the nanofibers could be greatly modified by adding poly(vinyl butyral) into the electrospinning solution. Moreover, the decoration with Ag nanoparticles effectively reduced the impedance of the composite under dry atmosphere, and facilitated the measurement of low humidity. Under optimized conditions, the composite presented high response magnitude to humidity, fast response (t90% of 16 s an 26 s for response and recovery, respectively), small hysteresis (∼2.8%RH), good sensing repeatability and the capability of detecting very low humidity (∼3.6%RH), representing much improvement over QC-P4VP nanofibers alone. The complex impedance spectra of the composites under different humidity levels were measured, and the sensing mechanism was explored. It is proposed that the highly desirable humidity sensing properties of the composite result from its balanced hydrophilicity and the distinct nanostructure.

ZnO nanoparticles, nanorods and nanosheets were in-situ deposited on the interdigitated gold electrodes by hydrothermal treatment of electrospun nanofibers containing zinc salt precursors and seed-induced solution growth of ZnO. The nanostructured ZnO was further covered with polyaniline (PANI) via vapor phase polymerization of aniline or dip-coating with water-dispersible PANI to prepare ZnO/PANI nanocomposites. The morphology and structure of the nanocomposites were investigated by scanning electron microscopy, X-ray diffraction patterns and Fourier transform infrared spectroscopy. The electrical responses of the nanocomposites toward NH3 have been examined at room temperature, and the nanocomposite revealed much better gas sensing properties than ZnO or PANI alone. The morphology of the nanocomposites had a great effect on their sensing properties. Specifically, the composite of ZnO nanosheets covered with vapor phase polymerized aniline demonstrated optimal sensing performance, featuring high response magnitude (relevant resistance change of ∼2150% towards NH3 as low as 10 ppm), ultralow limit of detection (∼5 ppb), good repeatability and excellent selectivity. It is proposed that the morphology and the interactions between p-type PANI and n-type ZnO are responsible for the highly desirable sensing properties of the nanocomposites.

In this paper, a photocatalyst composed of TiO2 nanoparticles supported on the nanofibers of poly(methyl methacrylate) (PMMA) was successfully prepared by hydrothermally treating the electrospun PMMA nanofibers containing titanium n-butoxide precursor at 135°C for 8h. As-prepared composite was characterized by field-emission scanning electron microscopy, X-ray diffraction pattern, thermal gravimetric analysis and Brunauer-Emmett-Teller (BET) surface area measurements. It is revealed that high content (42%) of tetragonal anatase TiO2 nanoparticles are uniformly loaded on the PMMA nanofibers to constitute the composite (TiO2@PMMA) photocatalyst with BET surface area of 21.4m2g-1. The photocatalytic activity of TiO2@PMMA towards the degradation of methyl orange (MO), a model pollutant, has been investigated. It is observed that 0.1g of the composite could degrade 100mL of MO (10mg/L) completely within 50min under UV illumination, exhibiting a high catalytic activity. Moreover, the composite could be easily separated from the reaction system by filtration, and maintain high photocatalytic activity in five consecutive cycles of the degradation of MO, suggesting its potentials in recycling use. The work provides a new approach for the development of novel supported photocatalysts with high catalytic activity and good reusability.

Fe 2 O 3 nanosheets were in-situ deposited on the interdigitated gold electrodes by hydrothermal treatment of the electrospun nanofibers containing FeCl 3 and poly(vinyl butyral). As-prepared electrode was further dip-coated with water-dispersible polyaniline (PANI) to fabricate a resistance gas sensor based on Fe 2 O 3 /PANI nanocomposite. The structure and morphology of the nanocomposite were investigated by X-ray diffraction pattern, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. It was found that the nanocomposite sensor exhibited much higher response magnitude towards low concentration of NH 3 (0.5–10.7 ppm) than the sensors based on either PANI or Fe 2 O 3 at room temperature (∼20 °C), indicating an obvious synergetic effect. The nanocomposite sensor was featured with ultra high response magnitude (relative resistance change of ∼3070% towards 10.7 ppm of NH 3 ) and excellent selectivity towards NH 3 . A sensing mechanism has been put forward, which takes into account of the conducting network comprising of bulk PANI and composites of PANI and Fe 2 O 3 nanosheets. It was proposed that the p/n heterojunction established between Fe 2 O 3 nanosheets and PANI coating played a major role in the highly desirable sensing performance of the composite.

ZnO nanoparticles or nanosheets have been in-situ grown on the substrate via a facile green approach featured with the hydrothermal treatment of electrospun nanofibers comprising polyvinyl alcohol and zinc acetate. The nanohybrids of ZnO with polypyrrole (PPy) were fabricated by the vapor phase polymerization of pyrrole on the surface of as-prepared nanostructured ZnO. The resulting nanohybrids were characterized by Fourier transform infrared spectroscopy, X-ray diffraction pattern, field emission scanning electron microscopy and high-resolution transmission electron microscopy and Brunauer–Emmett–Teller surface area measurements. Moreover, the electrical responses of the nanohybrids to NH 3 have been examined at room temperature. It was found that the nanohybrids revealed much higher response magnitude than either of the constituent component. Additionally, the morphology of ZnO affected the response magnitude of PPy/ZnO nanohybrids. The hybrids of ZnO nanosheets with PPy showed wide sensing range (0.5–200 ppm), very high response magnitude (relative resistance change of ∼20% towards 0.5 ppm of NH 3 ), good repeatability and selectivity. Attempts have been made to explore the gas sensing mechanism of the PPy/ZnO nanohybrids.

Formation of heterostructure and nanostructure is promising approach to improving the photocatalytic activity of TiO

Nanocomposites of SnO 2 nanosheets and polypyrrole (PPy) were facilely prepared and their gas sensing properties towards low concentration of NH 3 have been investigated at room temperature. Vertically aligned SnO 2 nanosheets were in situ grown on the substrates via hydrothermal treatment of electrospun nanofibers containing SnCl 2 precursors at a low temperature (135 °C), and coated with PPy by vapor phase polymerization of pyrrole. The SnO 2 nanosheets and the nanocomposites were characterized by X-ray diffraction patterns, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and high resolution transmission microscopy. The nanocomposite sensors exhibited much higher response magnitude towards NH 3 than the sensors based on PPy alone. The effect of the type of doping acids and polymerization time of pyrrole on the sensing properties of the nanocomposites was examined. The nanocomposite sensors revealed sensitive (sensitivity of ∼6.2%/ppm in the range of 1–10.7 ppm of NH 3 , detection limit of ∼257 ppb), selective and repeatable response to NH 3 , and the sensing mechanism has been explored. This work could provide references for the facile preparation of advanced gas sensors based on in situ grown nanostructured metal-oxide semiconductors and their composites.

We report a facile method for the in situ growth of vertically aligned SnO2 nanosheets on a substrate, which involved the hydrothermal treatment of the substrate covered with electrospun nanofibers of poly(vinyl butyral) containing SnCl2 at low temperatures and free of additives. The formation mechanism of nanostructured SnO2 has been explored. Gas sensors based on the composites of SnO2 nanosheets and polyaniline were prepared by vapor phase polymerization of aniline or the dip coating with water-processable polyaniline, and revealed good contact between the sensing films and underlying electrode. The nanocomposite sensors demonstrate very high response magnitude toward NH3 (relative resistance change of ∼3700% towards 10.7 ppm of NH3), ultra-low detection limit (∼46 ppb), good sensing repeatability and excellent selectivity at room temperature. Investigations on the gas sensing mechanism of the nanocomposite suggest that the establishment of the p/n heterojunction at the interface of p-type PANI and n-type SnO2 play an important role in enhancing the response magnitude of the nanocomposite. The method could provide new solutions for the direct fabrication of optoelectronic and electrochemical devices based on nanostructured metal oxides and their composites.

An impedance-type humidity sensor was prepared by sequentially depositing the thin films of crosslinked and quaternized poly(4-vinylpyridine) (QC-P4VP) and reduced graphene oxide (RGO) onto interdigitated gold electrodes. The QC-P4VP/RGO bilayer sensor reveals much lower impedance than QC-P4VP based sensor in the environments with low relative humidity (RH) levels, and could detect ultra-low humidity (0.18%RH) with very high response magnitude (impedance increase of 500% between 2.1%RH and 0.18%RH) at room temperature. Moreover, the bilayer sensor shows small hysteresis (∼4.5%RH) and fast response (t90% of 21 s and 78 s for adsorption and desorption processes, respectively). The effect of the concentration of RGO precursor, the deposition order and thickness of the sensing films, temperature, and the structure of the electrodes on the humidity sensing behaviors of the bilayer-structured sensors has been thoroughly examined, and the humidity sensing mechanism was explored.

Carbon nanotubes (CNTs) are widely used in the preparation of composite functional materials with improved performance due to their unique electrical, mechanical properties and one-dimensional nanostructure. In this paper, the composite of TiO2 nanoparticles and acid-treated carbon nanotubes distributed on poly(methyl methacrylate) (PMMA) nanofibers was fabricated by sequential treatments of electrospinning, hydrothermal synthesis and freeze-drying. The resulting ternary composite of TiO2/CNTs/PMMA, which is featured with a specific surface area of 83.2 m2/g, effectively photodegraded a series of dyes, such as methyl blue, Rhodamine B, Sulforhodamine B and methyl orange (MO). In particular, complete degradation of MO (10 mg/L, 100 mL) was accomplished with TiO2/CNTs/PMMA (20 mg) in 40 min under UV irradiation. Moreover, the high photocatalytic activity of the ternary composite, which is superior to that of TiO2/PMMA, did not deteriorate during consecutive photodegradation tests up to ten runs. The photocatalytic mechanism of TiO2/CNTs/PMMA has been explored. The desirable high photocatalytic activity, excellent stability and easy recyclability of the ternary composite is attributed to the introduction of CNTs and the electrospun PMMA nanofiber support.

Three kinds of copolymer based polyelectrolytes, including hydrolyzed and sulfonated poly(styrene-alt-maleic anhydride) (HSPSMA), hydrolyzed poly(sodium p-styrenesulfonate-co-maleic anhydride) (HPSSMA), and poly(sodium p-styrenesulfonate-co-itaconic acid) (PSSIA), have been synthesized by the radical copolymerization and functionalized via sulfonation and hydrolyzation. The polyelectrolytes were characterized by FT-IR, 1H-NMR and 13C-NMR, scanning electron microscopy and static water contact angle measurements, and their humidity sensing properties have been investigated at room temperature. The chemical structure and content of the comonomers have great effect on the humidity sensing behaviors of corresponding polyelectrolytes, such as response time, hysteresis and response magnitude, which is ascribed to the distinct interactions of the sensing materials with water molecules. Under optimal conditions, the composite of crosslinked PSSIA (molar feed ratio of SS/IA = 1/4) with polyaniline displayed good response magnitude (impedance variation of two orders of magnitude between 10%RH and 90%RH), small hysteresis (˜4.5%RH) and fast response (t90% of 9 s and 17 s for adsorption and desorption process). The work provides a new approach for the construction of high performance polyelectrolyte based humidity sensors.

Nanocomposites of quaternized and crosslinked poly(4-vinylpyridine) (QC-P4VP) and silver nanoparticles were prepared by a two-step procedure, and characterized by Fourier-transform infrared spectroscopy, Ultraviolet–visible spectroscopy and scanning electron microscopy. Bilayer-structured humidity sensors based on the nanocomposites were fabricated, and the effects of the concentration of silver salt precursor and poly(4-vinylpyridine), the method for the reduction of silver salt, the deposition order of the sensitive layers and environmental temperature on the humidity sensing characteristics of the composite sensor have been examined at room temperature. The composite sensor exhibited low impedance under dry atmosphere due to the introduction of Ag nanoparticles, and could detect very low relative humidity (RH) (down to 1% RH) with good sensitivity (impedance change of 2000% from 1% to 30% RH). In addition, the composite sensor demonstrated very wide measuring range (1–98% RH), and revealed faster response and smaller hysteresis than the sensor based on QC-P4VP alone. The complex impedance spectra of the composite sensor in the environments with different RH levels were investigated to explore its humidity sensing mechanism.

Gas sensors based on a composite of TiO2 nanosheets and polyaniline (PANI) were fabricated by the deposition of water-dispersible PANI on interdigitated gold electrodes decorated with TiO2 nanosheets via dip coating. Specifically, the TiO2 nanosheets were in situ grown on the electrodes by a simple hydrothermal treatment of the electrospun nanofibers of poly(methyl methacrylate) containing a tetrabutyl titanium precursor at a temperature as low as 135 °C in the presence of only water. The method circumvents high temperature calcination and is environmentally friendly. The structure and morphology of the TiO2 nanosheets and their nanocomposites with PANI were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, and high resolution transmission electron microscopy. The nanocomposite exhibited highly sensitive (detection limit as low as ∼45 ppb), selective and repeatable electrical responses towards NH3 at room temperature, which is better than those of the separate components and demonstrates an obvious synergetic effect. The enhanced sensing properties of the nanocomposite are proposed to relate to the high specific surface area and the p/n heterojunction between TiO2 nanosheets and PANI.

A bilayer-structured composite humidity sensor based on quaternized and crosslinked poly(4-vinylpyridine) (QC-P4VP) and polyaniline (PANI) was fabricated by depositing thin films of QC-P4VP and PANI onto interdigitated gold electrode in sequence. The composite was characterized by Fourier transform infrared spectroscopy, Ultraviolet–visible spectroscopy, scanning electron microscopy, and atomic force microscopy. The composite sensor could sensitively detect very low humidity (down to ∼1%RH) (impedance increase of ∼860% from 15% to 1%RH). Furthermore, the sensor exhibited relatively fast response ( t 90% of 24 s and 35 s for adsorption and desorption processes, respectively), small hysteresis (∼3%RH) and good repeatability. In addition, the composite sensor revealed impedance change close to 10 3 from 1% to 98%RH, suggesting its capability of detecting full-range humidity with high sensitivity. The effect of the concentration of poly(4-vinylpyridine) and PANI, deposition sequence of the sensitive layers on the humidity sensing characteristics of the composite has been examined. The humidity sensing mechanism of the composite sensor was proposed by considering the electrical properties of QC-P4VP and PANI at different humidity levels and the special bilayer structure.

Aim Endothelial recovery, or re-endothelialization, plays an important role in intimal hyperplasia and atherosclerosis after endothelial injury. Studying the mechanisms of re-endothelialization and strategies to promote efficient endothelial recovery are still needed. Interferon-induced protein 35 (IFI35) is an IFN-γ-induced protein that plays important roles in the antivirus-related immune-inflammatory response. In this study, we tested whether overexpression IFI35 affects the proliferation and migration of endothelial cells (ECs) and re-endothelialization. Methods Wire injury of the carotid artery was induced in C57BL/6 mice, which was followed by IFI35 or null adenovirus transduction. Evans blue staining and HE staining were performed to evaluate the re-endothelialization rate and neointima formation. In vitro studies, primary human umbilical vein endothelial cells (HUVECs) were transfected with Ad-IFI35 or siRNA-IFI35 to evaluate its potential roles in cell proliferation and migration. Furthermore, the potential mechanism relating inhibition of NF-κB/p65 pathway was elaborated by luciferase assay and IFI35 domain deletion assay. Results In IFI35 adenovirus-transduced mice, the re-endothelialization rates at days 3, 7 were significantly reduced compared to those in null adenovirus-transduced mice (5% and 35%, vs 20% and 50%, respectively). Meanwhile, subsequent neointimal hyperplasia was obviously increased in IFI35 adenovirus-transduced mice. In vitro studies further indicated that IFI35 inhibits both EC proliferation and migration by inhibiting the NF-κB/p65 pathway. Subsequent studies demonstrated that IFI35 functionally interacted with Nmi through its NID1 domain and that knock-down of Nmi significantly mitigated the inhibitory effect of IFI35 on EC proliferation and migration. Conclusion Our study revealed a novel mechanism through which IFI35 affects the proliferation and migration of ECs as well as neointima formation, specifically through inhibition of the NF-κB/p65 pathway. Thus, IFI35 is a promising target for the prevention and treatment of post-injury vascular intimal hyperplasia.

In this paper, a photocatalyst composed of TiO

Multi-walled carbon nanotubes (MWNTs) were dispersed in the matrix of quaternized and crosslinked poly(4-vinylpyridine) (QC-P4VP) to prepare a composite via solution blending and heat treatment. The composite was characterized by FT-IR spectroscopy and scanning electron microscopy. Thin film humidity sensors based on the composite were fabricated and their electrical responses to relative humidity (RH) were investigated at room temperature. The composite sensor showed much higher response magnitude than the sensor based on MWNTs (impedance increase of ∼4700% from 7 to 90%RH). Meanwhile, its impedance at low humidity was significantly decreased with respect to that of QC-P4VP based sensor. Furthermore, it could detect very low humidity with good sensitivity (impedance change of 16%/%RH over 1–30%RH), and demonstrate its capability of realizing full-range measurement of humidity. The effect of content of MWNTs, poly(4-vinylpyridine) (P4VP) and the additive, molecular weight of P4VP, temperature and testing frequency on the humidity sensing properties of the composite sensors has been examined. A sensing mechanism was proposed by considering the MWNT conductive network in the polyelectrolyte matrix.

Two polyelectrolytes, i.e., cationic poly(diallydimethylammonium chloride) (PDDA) and anionic sodium poly(4-styrenesulfonate) (PSSNa), were separately mixed with graphene oxide (GO) and hydrazine in solution, and heat-treated to result in composites of PDDA/graphene (GN) and PSSNa/GN, respectively. The composites were characterized by scanning electron microscopy, transmittance electron microscopy and Raman spectroscopy. Impedance-type humidity sensors were constructed by depositing the composite films onto interdigitated gold electrodes via dip-coating. The electrical response of the composite humidity sensors toward relative humidity (RH) was investigated at room temperature. It was found that the composites with higher content of GN exhibited lower impedance at low humidity levels. Both composite sensors could detect very low humidity (down to 0.2%RH), and showed good response magnitude in the low humidity range (relative impedance change of 300% and 1000% from 0.2 to 30%RH for PSSNa/GN and PDDA/GN, respectively). Moreover, the composites exhibited slight hysteresis similar to that of the polyelectrolytes alone, while their response time for desorption was even reduced. The sensing mechanism of the composites was explored by complex impedance spectra analysis, and the good sensing behavior at low humidity was proposed to the special electrical property and unique two-dimensional nanosheet structure of GN.

Electrostatic layer-by-layer (LbL) self-assembly (SA) was realized with processable polyaniline prepared with polystyrene sulfonic acid as a template (PANI-PSSA) and titanium dioxide sol as the starting materials, resulting in an ultrathin film of PANI-PSSA/TiO2. The SA process was confirmed by UV–vis spectra and quartz crystal microbalance measurements. The composite ultrathin film was characterized by X-ray photoelectron spectroscopy, X-ray diffraction patterns, field-emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. It was revealed that the content of TiO2 in the composite film was much higher than that of PANI-PSSA, and the doping level of PANI-PSSA was as high as 19.1%. Gas sensors were fabricated by depositing self-assembled ultrathin film of PANI-PSSA/TiO2 on interdigital gold electrodes, then covering another layer of PANI-PSSA via dip-coating. Electrical response to NH3 of the sensor was investigated at room temperature. Gas sensitivity of the sensor was found to closely relate to the number of self-assembled bilayers. Under optimal conditions, the sensor displayed high sensitivity (26.5% and 81.2% towards NH3 of 10 and 100 ppm, respectively), fast response (response time ∼ 1 min; recovery time ∼ 2 min), good reversibility and repeatability.

SnO2/graphene (GN) composite was fabricated via a simple one-pot hydrothermal method with graphene oxide (GO) and SnCl2 as the precursors. The composite was characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction patterns, scanning electron microscopy and high resolution transmittance electron microscopy. It exhibited 3D nanostructure in which flower-like microspheres consisting of SnO2 nanoflakes distributed among GN layers decorated with tiny SnO2 nanoparticles, and was featured with high surface area (94.9 m2/g). GO is supposed to act as a template in the hydrothermal process, promoting the preferential growth of SnO2 nanocrystals and preventing the agglomeration of SnO2 nanoparticles. NH3 sensing characteristics of the composite at room temperature were investigated, and found to closely relate to its composition and structure. Under optimal conditions, the composite displayed high response magnitude (15.9% for 50 ppm NH3), fast response (response and recovery time

Humidity sensing mechanism of sensors based on electrospun polyaniline (PANI) nanofibers was investigated. Dynamic adsorption and desorption behavior of the PANI nanofibers under different humidity levels were monitored by quartz crystal microbalance measurements and compared with their impedance response. It was found that the nanofiber sensor exhibited fast, reversible and highly sensitive impedance change as a function of water molecules adsorbed. Nyquist plots and Bode plots of the nanofiber humidity sensor under different humidity levels were obtained by electrochemical impedance spectra measurements at room temperature. An electrical equivalent circuit was established to model the impedance response to humidity variation of the nanofiber sensor. Calculated results using the model fitted quite well with the measured spectra. Exploration of the sensing mechanism was attempted by correlating the variation with humidity of three components of the equivalent circuit to the morphology of the electrospun nanofiber sensors.

Multiwalled carbon nanotubes (MWCNTs) were functionalized with α,ω-diamino poly(propylene oxide) (Jeffamine) of different molecular weights and crosslinked with poly(acrylonitrile-co-glycidyl methacrylate) [P(AN-GMA)] to prepare a novel nanocomposite for applications in gel polymer electrolytes (GPEs). The synthesized copolymer was characterized by 1H-NMR, Fourier transform infrared, and thermal analysis. Scanning electron microscope observation revealed that the Jeffamine-functionalized MWCNTs distributed uniformly in the nanocomposite membrane. The mechanical behaviors of the nanocomposite membranes were investigated. It was found that the crosslinked nanocomposite membranes of P(AN-GMA) and Jeffamine-functionalized MWCNTs exhibited much higher mechanical strength than the counterpart nanocomposite obtained by physical blending. Moreover, the weight content and molecular weights of Jeffamine had an effect on the mechanical properties of the nanocomposites. Differential scanning calorimeter measurements showed that the crosslinked nanocomposite membranes were amorphous. GPEs based on the nanocomposite were prepared and characterized by complex impedance measurements. The GPE based on the nanocomposite of P(AN-GMA) crosslinked with 6 wt % of MWCNTs functionalized by Jeffamine D400 showed an ionic conductivity of about 3.39 × 10−4 S cm−1 at 25°C, which is much higher than the counterpart nanocomposite of physically blended P(AN-GMA) and MWCNTs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

This paper presents a novel humidity sensor composed of a 433 MHz surface acoustic wave (SAW) resonator and an interdigitated gold electrode connected in series. The gold electrode was covered with a sensitive film of a composite of processable conductive polyaniline and polyvinyl alcohol. The frequency response of the novel SAW-impedance humidity sensor toward relative humidity (RH) was investigated at room temperature. The sensitivity of the SAW-impedance humidity sensors increased with the increase in the conductivity of the sensitive film. The sensor showed a sensitivity of ∼7.4 kHz/%RH at 30%RH, which was increased to 60 kHz/%RH at 47%RH. Moreover, such sensors exhibited short response and recovery times and good repeatability. It is worth noting that the sensor showed a linear frequency response to humidity over the range of 0.4–20%RH with a good sensitivity of ∼2 kHz/%RH, which reveals its potentials for detecting low humidity.

Processable polypyrrole (PPy) was prepared by solution polymerization of pyrrole in the presence of poly(ionic liquid) (PIL) and subsequent anion exchange reaction. The obtained hydrophobic PIL–PPy showed good dispersion in organic solvents, and formed a composite with quaternized and crosslinked poly(4-vinylpyridine) (QC-P4VP) by simple solution mixing and heat treatment. The structure and morphology of the composite of QC-P4VP/PIL–PPy have been characterized by FT-IR and scanning electron microscopy. It was found that PIL–PPy particles were dispersed within the matrix of QC-P4VP. Thin film humidity sensors based on the composite were facilely prepared by dip-coating and heat-induced crosslinking and quaternization. Humidity sensing properties of the sensors were investigated at room temperature. It was revealed that the sensor based on the composite exhibited higher sensitivity (impedance change from 10 7 to 10 3 Ω over the range of 11–95% RH), better sensing linearity and much smaller hysteresis (∼1% RH) as compared to sensors based on QC-P4VP alone. Moreover, it was featured with fast response and good reproducibility. Attempts were made to explain the improved sensing properties of the composite.

Polyaniline (PANi) nanofiber humidity sensors were prepared by electrospinning (ES) from the N,N-dimethylformamide solution of PANi, poly(vinyl butyral) (PVB) and poly(ethylene oxide) (PEO). Morphologies of the electrospun nanofibers prepared under different ES conditions were observed by scanning electron microscopy. Formation of beads in the nanofibers was found to greatly affect their adhesion to the substrates and the nanostructures. By modulating the composition of ES solution, PANi nanofibers with beads not only showed good adhesion to the electrode and thus good electrical contact, but also maintained relatively high specific surface area. Furthermore, hydrophilicity of the nanofibers was modified by adjusting the ratio of PVB to PEO in the ES solution, which had an effect on their sensing properties. Humidity response of the nanofiber sensors was investigated by measuring their impedance at different humidity levels at room temperature. The nanofiber sensors revealed much higher sensitivity than their film counterparts (impedance changing for three orders of magnitude from 20% to 90%RH). In addition, they were featured with good sensing linearity, fast response (t90% of ∼8 s and 6 s for adsorption and desorption, respectively), small hysteresis (∼1%RH) and good repeatability.

Two new hyperbranched fluorescent conjugated polymers containing pyridine units were synthesized via Heck coupling reaction and Sonogashira coupling reaction, respectively, and characterized by 1H NMR, 13C NMR, FTIR, and GPC. The copolymers are readily soluble in common organic solvents such as chloroform, THF, and DMF. Thermal analysis revealed that the copolymers had good thermal stability. The fluorescence quenching behaviors of the hyperbranched copolymers by metal ions were studied. It was found that the fluorescence of the copolymers can be effectively quenched by Pd2+. Moreover, the two hyperbranched copolymers exhibited different quenching efficiency, which may be related to difference in the hindrance for the chelation of pyridine unit with metal ions of the two polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

In this study, glycidyl methacrylate was copolymerized with poly(ethylene glycol) methyl ether methacrylate to obtain a copolymer {poly[glycidyl methacrylate–poly(ethylene glycol) methyl ether methacrylate] [P(GMA–PEGMA)]}, which was crosslinked with α,ω-diamino poly(propylene oxide) (Jeffamine) at various weight ratios and molecular weights to form novel gel polymer electrolytes (GPEs). The crosslinked copolymers were characterized by Fourier transform infrared spectroscopy and thermal analysis. The crosslinked polymers were amorphous in the pristine state and became crystallized after they were doped with lithium electrolyte. Furthermore, the crosslinking degree of the crosslinked polymers increased with increasing weight ratio of Jeffamine, and both the swelling properties and mechanical behaviors of the crosslinked polymers were heavily affected by the weight ratio and molecular weight of Jeffamine. The ionic conductivity (σ) of the GPEs from the crosslinked copolymers was determined by alternating-current impedance spectroscopy. A higher molecular weight and increased weight ratio of Jeffamine resulted in a higher σ. The GPE based on P(GMA–PEGMA) crosslinked with an equal weight of Jeffamine D2000 exhibited the highest σ of 8.29 × 10−4 S/cm at 25°C and had a moderate mechanical strength. These crosslinked copolymers could be potential candidates for the construction of rechargeable lithium batteries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Novel gel polymer electrolytes (GPEs) based on poly(acrylonitrile–glycidyl methacrylate) (P(AN–GMA)) crosslinked with α,ω-diamino poly(propylene oxide) (Jeffamine) of various weight ratios and molecular weights have been prepared, and the crosslinked polymers were characterized by FT-IR and thermal analysis. It is revealed that the crosslinked polymers were amorphous in pristine state and became crystallized when doped with lithium electrolyte. Their swelling properties and mechanical behaviors were investigated and found to be heavily affected by the weight ratio and molecular weight of Jeffamine. The effect of weight ratios and molecular weights of Jeffamine on the ionic conductivity of the GPEs based on the crosslinked polymers were determined by AC impedance spectroscopy. GPEs consisting of Jeffamine of higher molecular weights and increased weight ratios showed higher ionic conductivity. The GPE based on P(AN–GMA) crosslinked with Jeffamine D2000 at a weight ratio of 1.5 exhibited the highest ionic conductivity of 8.23 × 10−4 S cm−1 at 25 °C, and preserved a moderate mechanical strength. The crosslinked polymers can be potential candidates for the construction of rechargeable lithium batteries.

Hyperbranched polycarboxylates (HBPC) with different alkali metal cations (Li+, Na+, and K+) were prepared and characterized by 1H-NMR and thermal gravimetric analysis. Thin film humidity sensors based on HBPC and its composite with ZnO nanorods were fabricated. The morphologies of films of HBPC and the nanocomposite were investigated by atomic force microscopy, which revealed uniform distribution of ZnO nanorods in HBPC. The humidity-sensitive characteristics of HBPC and the nanocomposite were investigated at room temperature. It was found that the type of cations significantly affected the humidity-sensing behaviors of HBPC. In addition, the nanocomposite exhibited better humidity-sensitive properties than HBPC alone. Its impedance decreased for about three orders of magnitude over the range 19–97% RH, showing high sensitivity. Moreover, the nanocomposite exhibited fast response (∼ 9 and 10 s for response and recovery time between 97% RH and 33% RH, respectively) and small hysteresis (∼ 1.4% RH). The improved humidity-sensing behaviors of the nanocomposite over HPBC alone is explained by taking into account the hyperbranched structure of the polymer and the special interactions of the polymer and ZnO with water molecules. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Three new diketopyrrolopyrrole (DPP)-containing poly(phenylene vinylene)s varying at N-alkyl or 3,6-aryl substituents in DPP units, abbreviated as C6DPPDHPV, C6DTDPPDHPV, and C62DTDPPDHPV, were designed to comparatively study the structural effects on their photophysical, electrochemical properties, molecular organization and photovoltaic properties. The polymers exhibited remarkably broad UV–vis absorption spectra covering a major part of the wavelength range of visible light in the solar spectrum, and small bandgaps between 1.4 and 1.9 eV. X-ray diffraction and cyclic voltammetry measurements revealed that N-alkyl and 3,6-aryl in DPP unit played a key role in tuning their molecular organization as well as electrochemical behavior. The bulk heterojunction photovoltaic devices employing the three polymers as electron donors, together with PC 61 BM as electron acceptor, were examined. C6DPPDHPV based device showed the highest energy conversion efficiency of 0.72%. Lower hole mobilities and relatively higher HOMO energy levels may be responsible for inferior performance of C6DTDPPDHPV and C62DTDPPDHPV-based devices. Moreover, the C6DPPDHPV was preliminarily evaluated as active material in organic thin film transistor.

A nanocomposite of polypyrrole (Ppy) and palladium was fabricated by a facile method involving thermal dynamic refluxing of palladium salt and encapsulation of Pd nanoclusters with Ppy by vapor phase polymerization. The composite film was characterized using transmission electron microscopy and atomic force microscopy. It was found that the morphologies of the composite film were heavily affected by concentration and ratio of the reactants, polymerization time and polymer additives. The nanocomposite showed a response magnitude of 13.9–58.9% towards NH3 gas of 50–2000 ppm at room temperature, which is higher than that of Ppy alone by a factor of two. Moreover, the electrical response was reversible, reproducible and fast, with response and recovery times of 14 s and 148 s for 1000 ppm NH3, respectively. Gas sensory properties of the nanocomposite greatly depended on the size of Pd nanoparticles and the morphology of the composite film.

A silicon-containing polyelectrolyte with crosslinking structure was deposited on a surface acoustic wave (SAW) resonator operating at 433 MHz to construct a humidity sensor by the method of electrospray and heat treatment. Morphology observation by scanning electron microscopy and atomic force microscopy revealed that the polymer film so obtained was uniform and smooth. The frequency response to humidity of the SAW sensor over the range of 11–97%RH was investigated at room temperature. The effect of the electrospray parameters on humidity response of the sensor was examined including electrospray time, concentration of the electrospray solution. It was found that the sensor exhibited good sensitivity over a wide humidity range (∼−0.4 kHz/%RH), fast (∼10 s for adsorption and desorption) and reversible response. Moreover, it showed high stability under humid environment. The relationship between the polymer structure and its frequency sensing properties was also explored.

Conjugated polymer-grafted silica nanoparticles were prepared by Sonogashira coupling reaction involving a two-step procedure. The resulting conjugated polymer-grafted silica nanoparticles were characterized by infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and absorption and fluorescence spectroscopy. The conjugated polymer-grafted silica nanoparticles are highly fluorescent, and the fluorescent response of the nanoparticles of different size towards electron-deficient trinitrotoluene (TNT) was studied by examining how the steady state fluorescence intensity changes with the concentration of TNT. The conjugated polymer-grafted silica nanoparticles show high sensitivity toward TNT, with a detection limit down to 1 μM.

The application of Friedel-Crafts (FC) alkylation reaction to the in situ compatibilization between polystyrene-grafted nano-sized TiO2 (PS-grafted TiO2) and polypropylene (PP) was assessed. The PS-grafted TiO2 was first prepared via dispersion polymerization of styrene (St) using 3-(trimethoxysilyl) propyl methacrylate treated nano-sized TiO2 (MPS-treated TiO2) as cores, and then dispersed within PP by melt blending with different contents of FC catalyst, AlCl3/St, to give PP/PS-grafted TiO2 nanocomposites. The dispersion of PS-grafted TiO2 in PP and interfacial adhesion of PP/PS-grafted TiO2 nanocomposites were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The results indicated that the dispersion of PS-grafted TiO2 in PP could be improved, with an enhancement of interfacial adhesion between TiO2 and PP, by introducing FC catalyst with adequate concentration, which led to a better thermal stability and resistance to ultraviolet (UV) aging of PP/PS-grafted TiO2 nanocomposites. The effect of FC catalyst on the compatibilization between the PS-grafted TiO2 and PP was discussed based on FC alkylation reaction mechanism. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The photovoltaic behaviors of diketopyrrolopyrrole (DPP) embedded poly(phenylenevinylene) (C8-DPP-PPV) and poly(phenyleneethynylene) (C10-DPP-PPE) were investigated. The two polymers exhibited good solubility in common organic solvents, high thermal stability and broad UV/visible absorption ranging from 300 to 600 nm in films. Their optical band gaps were found to be 1.94 eV for C8-DPP-PPV and 2.05 eV for C10-DPP-PPE. Moreover, their HOMO energy levels were relatively low at around −5.6 to −5.8 eV as estimated by electrochemical measurements. The polymer/PCBM bulk heterojunction solar cells exhibited a power conversion efficiency of 0.16% for C10-DPP-PPE. In addition, all-polymer solar cells consisting of C10-DPP-PPE/P3HT were also fabricated in view of the potential of C10-DPP-PPE as a polymeric acceptor, revealing an efficiency of 0.01%.

Nanofibers of a composite of a silicon-containing polyelectrolyte, polyethylene oxide and polyaniline (PANI) were obtained by electrospinning and heat treatment. The morphologies of the composite nanofibers were characterized by scanning electron microscopy, which showed that the nanofibers with a diameter of 250–500 nm formed a non-woven mat with highly porous structure. It was found that the polymer composite nanofibers showed impedance change from 6.3 × 10 6 to 2.5 × 10 4 Ω with the increment of relative humidity (RH) from 22 to 97% at room temperature, exhibiting high sensitivity and good linearity on a semi-logarithmic scale. In addition, they exhibited fast and highly reversible response characterized by very small hysteresis of ∼2% RH and short response time (t 90% : 7 s and 19 s for adsorption and desorption between 33 and 97%RH, respectively). The modification of the electrode with poly(diallyldimethylammonium chloride) prior to the deposition of nanofibers improved their humidity response, which may be related to the enhanced contact between the nanofibers and underlying substrate. The effect of PANI on the humidity response of the composite nanofibers was also investigated, and it was found that PANI effectively decreased the impedance of the nanofibers. The electrospun polymer composite nanofibers may find applications in the preparation of high performance humidity sensors.

A novel calixarene-containing hyperbranched aliphatic polyester incorporated with pendant europium complexes (H20-Cal-Eu) was synthesized and characterized by FTIR, UV, and element analysis. The polymer H20-Cal-Eu shows a glass-transition temperature (Tg) of 127°C, and a deposition temperature in the range of 280–600°C, as revealed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The investigation on its photoluminescence (PL) properties revealed that the polymer emitted a remarkably strong red luminescence. Furthermore, its half spectral bandwidth of the polymer film is only about 10 nm as determined from luminescence spectra, suggesting that the light is nearly monochromatic. It is proposed that the hyperbranched polymer (HBP) containing rare earth element exhibits great potential as a red light emitting material. Copyright © 2009 John Wiley & Sons, Ltd.

Quaternized and salt-doped copolymer of 2-(dimethylamino) ethyl methacrylate (DMAEMA) with poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) was used to prepare resistive thin film humidity sensors. Their humidity sensitive properties have been characterized. The effects of the proportion of the comonomer and the amount of doped salt on the humidity sensitive properties of quaternized and salt-doped copolymer have been investigated. The humidity sensitive mechanisms of two different monomer structural units in the copolymer were discussed. The sensors based on the copolymers with different proportions of the comonomers exhibit a variety of conductivity and sensitivity for different humidities. Especially, the sensors exhibit high conductivity even at very low humidity. It is proposed that the good humidity sensitive properties are related to the introduction of salt-doped PEGMEMA in the copolymer. Copyright © 2009 John Wiley & Sons, Ltd.

BACKGROUND: Polymer-based light emitting diodes (PLEDs) have received considerable attention as they combine the good mechanical and processing properties of polymers with semiconducting behavior, and can be easily fabricated as flexible devices. To obtain high-performance PLED materials by balancing the carrier injection of poly(phenylene ethynylene)s (PPEs), polymers containing two aryl-heterocyclic rings, namely diketopyrrolopyrrole (DPP) or triphenylpyrazoline (TPP), have been synthesized and investigated. RESULTS: PPE-type polymers containing DPP or TPP units were synthesized using Heck–Sonogashira coupling methodology and characterized by 1H NMR, Fourier transform infrared and UV-visible spectroscopies, elemental analysis, gel permeation chromatography, photoluminescence (PL), X-ray diffraction, thermogravimetic analysis and cyclic voltammetry. The polymers obtained are easily soluble in common solvents and form smooth and uniform films. They are yellow or red emitters as revealed by PL. In addition, they show large Stokes shifts, which is in agreement with their twisted molecular structures determined via quantum chemical calculations. CONCLUSION: PPE-type polymers containing DPP or TPP units were successfully synthesized by coupling polymerization. They exhibit band gaps of 1.73 and 2.37 eV, respectively, and show potential as PLED materials. In addition, DPP-containing polymers with a very low band gap could be applied as potential photovoltaic materials. Copyright © 2009 Society of Chemical Industry

Pyrrole (Py)-based polyelectrolytes (Py-PE): P(Py-COOLi), P(Py-COONa), and P(Py-COOK) was synthesized, characterized, and used to prepare thin film resistive humidity sensors. Their humidity sensitive properties have been investigated, and sensing mechanism was presented. The Py-PE contains PPy as backbone and the side chain bearing carboxylic salt group, which made its sensor exhibited a very wide humidity sensing range of 0–97% relative humidity (RH), high conductivity even at very low humidity, and both ionic and electronic conduction contributed to its conductivity. Among all the Py-PE, P(Py-COOK) showed high sensitivity, with the impedance changing of about three orders of magnitude (103–106 Ω) from 97 to 0% RH, whereas P(Py-COONa) showed quick response for both absorption (12.5 s) and desorption (15.2 s). Py-PE prepared is promising for preparation of thin film resistive humidity sensors capable of detecting low humidity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009