Synthesis and characterization of Ag/polypyrrole nanocomposites based on silver nanoparticles colloid

Ag/polypyrrole nanocomposites were successfully synthesized via in situ chemical oxidation polymerization of pyrrole based on mercaptocarboxylic acid capped Ag nanoparticles colloid. Scanning electron microscopy (SEM) measurement showed that the obtained Ag/polypyrrole nanocomposites were spherical. Transmission electron microscopy (TEM) measurement showed that the Ag nanoparticles were inside the polypyrrole particles and had a little aggregation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra were used to characterize the structure of the obtained Ag/polypyrrole nanocomposites. A possible formation mechanism of the Ag/polyrrole nanocomposites was also proposed.     

Electrochemically polymer-coated carbon fibres: Characterization and potential for composite applications

Electrochemical polymerization is used to achieve carbon-fibre coatings with heteroaromatic conducting compounds, such as polypyrrole or polyindole. The coated-fibres surfaces are characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The resulting chemical and mechanical properties are studied and this new material is tested as a reinforcement agent in an epoxy resin matrix.     

Preparation of polypyrrole-coated silver nanoparticles by one-step UV-induced polymerization

The silver/polypyrrole core/shell nanoparticles with diameter less than 60 nm were successfully synthesized in the presence of polyvinylpyrrolidone by one-step UV-induced polymerization. The nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Possible mechanism was proposed for the formation of the silver/polypyrrole core/shell nanostructure during the photopolymerization.     

Synthesis and characterization of polypyrrole nanotubes/multi-walled carbon nanotubes composites with superior electrochemical performance

Novel polypyrrole nanotubes/multi-walled carbon nanotubes (PPyNTs/MWCNTs) composites have been successfully synthesized via in situ chemical oxidation polymerization with methyl orange as soft template. Scanning electron microscopy and transmission electron microscopy images revealed that MWCNTs intertwined with the PPyNTs and PPyNTs/MWCNTs composites formed in water–ethanol solution. The obtained composites exhibited perfect electrochemical characteristic compared with PPyNTs and MWCNTs owing to the synergetic effect and the specific capacitance of the composites was strongly influenced by the mass ratio of pyrrole to MWCNTs. According to the galvanostatic charge/discharge analysis, the specific capacitance of PPyNTs/MWCNTs composites is up to 352 F g^?1 at a current density of 0.2 A g^?1 in 1 M KCl solution, much higher than that of the PPyNTs (178 F g^?1) and MWCNT (46 F g^?1), suggesting its potential application in supercapacitors.     

Synthesis and characterization of stable aqueous dispersions of graphene

A stable aqueous dispersion (5 mg ml^?1) of graphene was synthesized by a simple protocol based on three-step reduction of graphene oxide (GO) dispersion synthesized using the modified version of Hummers and Offeman method. Reduction of GO was carried out using sodium borohydride, hydrazine hydrate and dimethyl hydrazine as reducing agents. The chemically synthesized graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy, thermogravimetric analysis (TGA), optical microscopy. The stability of aqueous dispersions of graphene was confirmed through zeta potential measurements and the negative zeta potentials of 55–60 mV were obtained indicating the high stability of aqueous graphene dispersions.     

电子封装材料表面化学制备高导电率聚吡咯薄膜的研究

研究了在环氧树脂塑料封装材料表面制备导电聚吡咯(PPy)薄膜的化学聚合方法,分析了影响聚吡咯薄膜微观形貌、附着力及电导率的因素.用四探针法测聚吡咯薄膜的电导率,并用扫描电子显微镜(SEM)、红外光谱(IR)、X射线光电子能谱(XPS)进行了表征.通过对电子封装材料的表面预处理与改性,制得了附着性好、均匀连续的聚吡咯薄膜,经掺杂电导率达到了45.10S/cm.     

Synthesis of wurtzite ZnS nanocrystals at low temperature

Nanocrystallites of wurtzite hexagonal ZnS have been successfully synthesized without using any capping agent by simple chemical precipitation method at a low calcination temperature of 150 °C. It has been found that the size of the synthesized ZnS nanocrystallites decreases as Zn²⁺:S^2? ratio is decreased. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis absorption spectroscopy and M–H characteristics. The XRD patterns have confirmed that the prepared ZnS nanoparticles are of wurtzite hexagonal phase. XRD, SEM and TEM studies have shown the decrease in the particle size with the increase in S^2? source. TEM images have clearly shown that size distribution of the particles lie in the range of 5–30 nm. The optical absorption bandgap of the synthesized nanocrystals has been found to be in the range of 3.69–3.74 eV. Magnetization study has shown the ‘diamagnetic’ behavior of synthesized ZnS nanocrystallites with a weak ferromagnetic behavior in the low field regime. The observed weak ferromagnetism has been understood due to the presence of defects in the synthesized ZnS nanoparticles.     

The fabrication of polypyrrole–TiO2 nanorod array heterojunction with strong ultraviolet photoresponse

We prepare the heterojunction consisting of the TiO₂ nanorod array and polypyrrole (PPy) by using the photoexcited TiO₂ nanorod array to initiate polymerization. The structures of the heterojunction composites are investigated using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The dependence of the charge transfer resistances of the composite films on reaction time is shown by the electrochemical impedance. Devices are prepared from the PPy–TiO₂ composite films, which are synthesized in various reaction time, and photoresponse measured. The device exhibits strong photoresponse to ultraviolet lights, thus having potential as a photoconductive UV detector.     

Novel silicon carbide/polypyrrole composites; preparation and physicochemical properties

Novel silicon carbide/polypyrrole (SiC/PPy) conducting composites were prepared using silicon carbide as inorganic substrate. The surface modification of SiC was performed in aqueous solution by oxidative polymerization of pyrrole using ferric chloride as oxidant. Elemental analysis was used to determine the mass loading of polypyrrole in the SiC/PPy composites. Scanning electron microscopy showed the surface modification of SiC by PPy. PPy in composites was confirmed by the presence of PPy bands in the infrared spectra of SiC/PPy containing various amounts of conducting polymer. The conductivity of SiC/PPy composites depends on PPy content on the surface. The composite containing 35 wt.% PPy showed conductivity about 2 S cm⁻¹, which is in the same range as the conductivity of pure polypyrrole powder prepared under the same conditions using the same oxidant. PPy in the composites was clearly detected by X-ray photoelectron spectroscopy (XPS) measurements by its N1s and Cl2p peaks. High resolution scans of the C1s regions distinguished between silicon carbide and polypyrrole carbons. The fraction of polypyrrole at the composite surface was estimated from the silicon and nitrogen levels. The combination of XPS and conductivity measurements suggests that the surface of the SiC/PPy composites is polypyrrole-rich for a conducting polymer mass loading of at least 12.6 wt.%.     

Radiolytic synthesis of conducting polypyrrole/carbon nanotube composites

Conducting polypyrrole (PPy)/multi-wall carbon nanotube (MWNT) composites have been synthesized by the in situ gamma radiation-induced chemical polymerization method at room temperature. The resulting cable-like morphology of the composite (PPy–MWNT) structures was characterized by elemental analysis, Fourier transform infrared, field-emission scanning electron microscope, thermal gravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscope. The standard four-point probe method was utilized for measuring the conductivity of the samples. We observed no significant chemical reaction between the polymer and carbon nanotube, which only showed that polypyrrole chains are tightly coated on to MWNT. The physical properties of the composites (PPy–MWNT) were measured and showed that the MWNT were modified by conducting polypyrrole with various properties enhanced.     

Steam-assisted crystallization of TPA+-exchanged MCM-41 type mesoporous materials with thick pore walls

Hierarchical MCM-41/MFI composites were synthesized through ion-exchange of as-made MCM-41 type mesoporous materials with tetrapropylammonium bromide and subsequent steam-assisted recrystallization. The obtained samples were characterized by powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis, FT-IR, ¹H–¹³C CP/MAS and nitrogen adsorption–desorption. The XRD patterns show that the MCM-41/MFI composite possesses both ordered MCM-41 phase and zeolite MFI phase. SEM and TEM images indicate that the recrystallized materials retained the mesoporous characteristics and the morphology of as-made mesoporous materials without the formation of bulky zeolite, quite different from the mechanical mixture of MCM-41 and MFI structured zeolite. Among others, lower recrystallization temperature and the introduction of the titanium to the parent materials are beneficial to preserve the mesoporous structure during the recrystallization process.     

聚吡咯网状纳米结构的合成及表征

采用原位聚合法,以聚乙二醇-6000(PEG-6000)为表面活性剂合成网状纳米聚吡咯(PPy),并考察了反应物的物质的量比对产品的形貌和吸波性能影响。利用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、矢量网络分析仪对其进行表征,结果表明,Py∶HCl∶FeCl3物质的量比为1∶0.5∶2时,聚吡咯的吸波性能最佳,在3430MHz处达到了-38.9dB。     

Effect of processing on the particle size of tin oxide nano-powders

Nano sized tin oxide powders have been synthesized via two different chemical routes namely solid-state and sol–gel route for the fabrication of tin oxide gas/odors sensor. The synthesized powders have been characterized by simultaneous thermo gravimetric and differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy. The effect of synthesis routes have been investigated on particle size and morphology of tin oxide powders. Powder XRD patterns show that the synthesized powders have tetragonal (rutile) crystal structure. FESEM of formed thick films reveal that powder prepared by solid-state reaction route is less agglomerated as compared to the powder prepared by sol–gel route. XRD and FESEM indicate that there is the formation of tin oxide nanoparticles in the range of 15–50 nm. FTIR spectrums of synthesized powders show Sn-O or Sn-O-Sn stretching modes and its lattice modes at 615 and 494 cm^?1.     

Growth and characterization of silicon nitride films for optoelectronics applications

Silicon nitride (Si₃N₄) films have been deposited by thermal-CVD system and characterized by the ellipsometry, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The present paper reports the effect of deposition temperature on the physical and optical properties of deposited Si₃N₄ films. The stress of the film has been observed to be tensile in nature and it is found to be decreased by increasing the deposition temperature through ellipsometric study. The increase in refractive index of the film has been observed with increasing deposition temperature. The Si–H, N–H and Si–N–Si stretching characteristic peaks of Si₃N₄ films have been observed with significant intensities by using FTIR spectroscopy. The peak positions of Si–N–Si stretching absorption band and the corresponding full width at half maxima (FWHM) have also been analyzed. The FWHM observed to be increasing on corresponding increase in the deposition temperature, which indicates the improvement in the deposited films quality. However, films deposited in the temperature range of 780–850 °C, have some amount of H contents. The total H concentration in the films decreases with corresponding increase in deposition temperature, which reveals that the densification of deposited films increases on increasing the deposition temperature. The SEM and EDAX have been used to carry the morphological and compositional analysis of the deposited films, respectively.     

Low temperature synthesis of high quality carbon nanospheres through the chemical reactions between calcium carbide and oxalic acid

Carbon nanospheres (CNSs) were synthesized through the chemical reactions of calcium carbide and oxalic acid without using catalysts. The chemical reactions were carried out in a sealed stainless steel pressure vessel with various molar ratios at temperatures of 65–250 °C. The synthesized CNSs have been characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) attached to the SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The total yield of carbonaceous materials relative to the starting material is about 4% (w/w). SEM and TEM results reveal that the percentage of CNSs is high (>95%). The CNSs that have been synthesized are roe-like spheres of relatively uniform size with diameters of 60–120 nm. The attached EDS result shows that the carbon content of CNSs reaches up to 98%.     

Characterization and temperature-dependent conductivity of polyaniline nanocomposites encapsulating gold nanoparticles on the surface of carboxymethyl cellulose

Polyaniline nanocomposites encapsulating gold nanoparticles on carboxymethyl cellulose surface were prepared via the polymerization of aniline hydrochloride with different carboxymethyl cellulose (CMC) concentrations (wt.%) using HAuCl₄ as oxidant. The synthesized composites were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology was studied by electron diffraction scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The embedded crystallinity of the composites was investigated by X-ray diffraction (XRD) analyses. The electrical property of the composites was examined by temperature-dependent DC conductivity in the range of 300–500 K. The composites exhibited higher electrical conductivities with increased CMC concentration under equivalent conditions. Activation energy for electron transport was also calculated based on the conductivity data.     

Synthesis and luminescence properties of highly uniform SiO2@LaPO4:Eu3+ core–shell phosphors

SiO₂@LaPO₄:Eu³⁺ core–shell phosphors have been successfully synthesized by a one-step and economical wet-chemical route at low temperature. The as-obtained products were characterized by means of photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The SEM, EDS and XPS analysis indicate that SiO₂@LaPO₄:Eu³⁺ core–shell phosphors can only be synthesized in a pH range of 8–11 and the possible mechanism has been proposed. The XRD results demonstrate that the structure of LaPO₄:Eu³⁺ layers is transferred into monoclinic phase from hexagonal phase after annealing at 800 °C for 2 h. The SiO₂@LaPO₄:Eu³⁺ phosphors show strong orange–red luminescence under ultraviolet excitation. The relative emission intensity of Eu³⁺ increases with increasing the annealing temperature and the number of coating cycles, and the optimum concentration for Eu³⁺ was determined to be 5 mol% of La³⁺ in SiO₂@LaPO₄ phosphors.     

Studies on the structural and optical properties of zinc oxide nanobushes and Co-doped ZnO self-aggregated nanorods synthesized by simple thermal decomposition route

Pure and Co-doped zinc oxide nanomaterials were prepared by a simple low temperature synthesis and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), diffused reflectance spectroscopy (DRS) and electron paramagnetic resonance (EPR) techniques. The results showed the formation of nanobushes that consists of several nanowires for pure ZnO and the nanorods formed by self-aggregation for Co-doped ZnO. The presence of Co²⁺ ions replacing some of the Zn²⁺ in the ZnO lattice was confirmed by EPR and DRS studies. The mechanism for the formation of self-aggregated and self-aligned ZnO rods after the incorporation of cobalt in the lattice by the building block units is discussed in this study. Morphological studies were carried out using SEM and HR-TEM, which supports the validity of the proposed mechanism for the formation of ZnO nanobushes and Co-doped ZnO nanorods. The synthesized nanomaterials were found to have good optoelectronic properties.     

Interfacial synthesis of platinum loaded polyaniline nanowires in poly(styrene sulfonic acid)

Polyaniline-poly(styrene sulfonic acid)-platinum (PANI-PSS-Pt) composite is prepared through an interfacial polymerization route. The composite is obtained by incorporating Pt nanoparticles into conductive PANI matrix by the reduction of Pt⁴⁺ ions to Pt nanoparticles during the oxidative polymerization of aniline in PSS as medium. The interfacial synthesis offers the microenvironment for the growth of PANI nanostructures with simultaneous incorporation of Pt nanoparticles to result PANI-PSS-Pt nanocomposite. PANI-PSS-Pt nanocomposite is characterized by UV-Vis absorption spectroscopy, FTIR spectroscopy, scanning microelectronic microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).     

Synthesis of polyaniline/ZrO<Subscript>2</Subscript> nanocomposites and their performance in AC conductivity and electrochemical supercapacitance

Polyaniline/zirconium oxide (PANI/ZrO₂) nanocomposites have been synthesized by incorporating ZrO₂ nanoparticles into the PANI matrix via liquid–liquid interfacial polymerization method. The composite formation and structural changes in PANI/ZrO₂ nanocomposites were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). PXRD pattern of PANI/ZrO₂ nanocomposites exhibited sharp and well-defined peaks of monoclinic phase of ZrO₂ in PANI matrix. SEM images of the composites showed that ZrO₂ nanoparticles were dispersed in the PANI matrix. The FT-IR analysis revealed that there was strong interaction between PANI and ZrO₂. AC conductivity and dielectric properties of the nanocomposites were studied in the frequency range, 50–10⁶ Hz. AC conductivity of the nanocomposites obeyed the power law indicating the universal behaviour of disordered media. The nanocomposites showed high dielectric constant in the order of 10⁴, which could be related to dielectric relaxation phenomenon. Further, the materials were checked for their supercapacitance performance by using cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). Among the synthesized nanocomposites, PANI/ZrO₂-25 wt.% showed a higher specific capacitance of 341 F g^?1 at 2 m Vs^?1 and good cyclic stability with capacitance retention of about 88% even after 500 charge–discharge cycles.