Electrical transport behaviour of silver–PMMA nanocomposite films at low temperature

In this study, the silver nanoparticles, capped with oleylamine, were embedded in polymethylmethacrylate (PMMA) using sonication to fabricate Ag–PMMA nanocomposites. The well-dispersed nanocomposite samples are analysed using UV-Vis absorption spectroscopy, atomic force microscopy and small angle X-ray scattering. The interfacial interaction of Ag nanoparticles and PMMA polymer is investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. It is concluded that a ligand-exchange process occurs when capped silver nanoparticles are incorporated in PMMA polymer. Electrical resistivity of nanocomposite samples was measured by a four-probe technique in the 70–300?K range. The nanocomposites showed a transition with onsets at ～230 and ～160?K. They exhibited a semiconductor-like conductivity at higher temperatures, a rapid metallic conductivity at middle range and nearly temperature independent conductivity at lower temperatures.     

Study of dielectric and piezoelectric properties of Pb(Ni,Nb)O3–Pb(Zr,Ti)O3 ceramics using mechanically activated powder

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al₂O₃.     

Preparation and characterization of polymer/inorganic nanoparticle composites through electron irradiation

In this paper, we report a new method to prepare the polymer/inorganic nanoparticle composites using electron irradiation-induced polymerization. The mixture of nanoparticles and MMA solution were co-irradiated by 1.6 MeV electron beam to a dose of 10, 20 and 30 kGy at a dose-rate of 60 kGy/h in air at room temperature. The products after irradiation were extracted using a soxhlet extractor with boiling xylene and investigated by X-ray diffraction (XRD), Fourier transmission infrared (FTIR), X-ray photoelectron spectroscopy (XPS), optical absorption spectra (OAP) and photoluminescence (PL). The FTIR and XPS results show that there exist some unextractable PMMA in the nanocomposites after extraction, indicating a strong interaction between the PMMA and nanoparticles. PL results show that new luminescence peaks appear at 415 and 420 nm for the nanocomposites of anatase and γ-Al₂O₃.     

Charging and discharging mechanisms of organic bistable devices based on ZnO nanoparticles capped with a poly N-vinylcarbazole polymer

Scanning electron microscopy and energy-dispersive spectrometer images of hybrid nanocomposites of ZnO nanoparticles capped with a poly N-vinylcarbazole (PVK) that was fabricated using the spin-coating technique showed that the ZnO nanoparticles were capped with a PVK polymer layer. The measurement of the current-voltage (I-V) of the Al/ZnO nanoparticles capped with a PVK layer/indium-tin-oxide/glass devices at 300 K showed electrical bistability and negative differential resistance, which indicate the nonvolatile nature of the memory effect of the electron captured in the ZnO nanoparticles. The charging and discharging mechanisms of the organic bistable devices that were fabricated using hybrid nanocomposites of ZnO nanoparticles capped with a PVK layer are described based on the I-V results.     

Conducting nanocomposites of poly(N-vinylcarbazole) with single-walled carbon nanotubes

The in situ solid-state polymerization of N-vinylcarbazole (NVC) at an elevated temperature in the presence of single-walled carbon nanotubes (SWCNTs) leads to the formation of new types of composite materials, the morphology and properties of which were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and electrical property measurements. FTIR spectroscopy and XPS studies confirmed the ability of SWCNTs to initiate the in situ polymerization of NVC monomers. FE-SEM and TEM results showed the coating of the outer surfaces of SWCNTs by the PNVC hompolymer with separation of individual SWCNTs from the bundles. Thermogravimetric analysis revealed a moderate improvement in the thermal stability of the nanocomposites at a higher temperature region relative to the base polymer. The electrical conductivity of neat polymer dramatically improved in the presence of SWCNTs. For example, dc electrical conductivity increased from 10(-16)-10(-12) S x cm(-1) for neat PNVC to approximately 10(-6) S x cm(-1) for nanocomposite containing 9 wt% SWCNTs.     

Synthesis of 16-Mercaptohexadecanoic acid capped gold nanoparticles and their immobilization on a substrate

Controlled assembly of nanoparticles on substrates is a promising path to develop miniaturized electronic and optical devices. Among the important issues to be addressed in this area include immobilization of the nanoparticles on substrates in order to ensure that the system is robust. In this work, 16-mercaptohexadecanoic acid (16-MHDA) capped gold nanoparticles with a narrow size distribution have been synthesized through a single phase synthesis method and subsequently immobilized on to silicon surface through covalent molecular assembly. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the absence of unreacted thiol in the synthesized gold nanoparticles. Presence of gold nanoparticles on Si surface after the immobilization process was confirmed through XPS. Cross-sectional high resolution transmission electron microscopy (HR-TEM) images provide direct evidence that the particles are indeed anchored to the silicon surface. The formation of uniform-sized and separated acid functionalized gold nanoparticles and their immobilization on to Si provide a basis for further nano-structuring.     

Reducing HAuCl(4) by the C(60) dianion: C(60)-directed self-assembly of gold nanoparticles into novel fullerene bound gold nanoassemblies

The C(60) dianion is used to reduce tetrachloroauric acid (HAuCl(4)) for the first time; three-dimensional C(60) bound gold (Au-C(60)) nanoclusters are obtained from C(60)-directed self-assembly of gold nanoparticles due to the strong affinities of Au-C(60) and C(60)-C(60). The?process was monitored in situ by UV-vis-NIR spectroscopy. The resulting Au-C(60) nanoclusters were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive spectroscopy (EDS), x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and FT-IR and Raman spectroscopies. TEM demonstrates the formation of 3D nanonetwork aggregates, which are composed of discrete gold nanocores covered with a C(60) monolayer. The SAED and XRD patterns indicate that the gold nanocores inside the capped C(60) molecules belong to the face-centred cubic crystal structure, while the C(60) molecules are amorphous. The EDS and XPS measurements validate that the Au-C(60) nanoclusters contain only Au and C elements and Au(3+) is reduced to Au(0). FT-IR spectroscopy shows the chemiadsorption of C(60) to the gold nanocores, while Raman spectroscopy demonstrates the electron transfer from the gold nanocores to the chemiadsorbed C(60) molecules. Au-C(60) nanoclusters embedded in tetraoctyl-n-ammonium bromide (TOAB) on glassy carbon electrodes (GCEs) have been fabricated and have shown stable and well-defined electrochemical responses in aqueous solution.     

Electrochemical sensing of sulphur dioxide: a comparison using dodecanethiol and citrate capped gold nanoclusters

A comparison of cyclic voltammograms of dodecanethiol (DDT) capped Au nanoclusters (5.0 0.5 nm) and trisodium citrate (Cit) capped Au nanoclusters (approximately 10-15 nm) modified glassy carbon electrode shows a dramatic variation in the current when exposed to a small amount of sulphur dioxide. This is explained using the electrocatalytic properties of Au nanoclusters towards the oxidation of SO2, thus facilitating the fabrication of electrochemical sensors for the detection of SO2. The intrinsic redox changes observed for gold nanocluster-modified glassy carbon electrodes disappear on passing SO2, despite a dramatic current increase, which indeed scales up with the amount of dissolved SO2. Interestingly, a complete rejuvenation of the redox behavior of gold is also observed on subsequent removal of SO2 from the solution by passing pure nitrogen for 15 minutes. Further, these nanoclusters when characterized with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) after SO2 passage reveal a variety of SO2 adsorption modes on gold surface. XP spectra also show a shift of 1.03 eV towards higher binding energy indicating a strong adsorption of SO2 gas, while FTIR gives conclusive evidence for the interaction of SO2 with gold nanoparticles.     

Polyaniline–CdS nanocomposites: effect of camphor sulfonic acid doping on structural, microstructural, optical and electrical properties

Nanocomposites of CdS nanocrystals with conducting polyaniline doped with camphor sulfonic acid (CSA) have been prepared by spin coating technique and investigated by X-ray diffraction, field emission scanning electron microscopy (FESEM), fourier transform infra red spectroscopy (FTIR), UV–visible spectroscopy and electrical transport method. The X-ray diffraction patterns showed broad peaks due to formation of nanoparticles of CdS in polyaniline matrix. FESEM showed that the transformation of morphology from agglomeration to nanopetals. The FTIR spectra confirmed the interaction between CSA and polyaniline (PANi)–CdS nanocomposite. The UV–visible spectrums revealed the enhancement of doping level for the PANi–CdS nanocomposites which is assigned to the existence of greater number of charges on the polymer backbone. DC electrical conductivity studies showed an increase in conductivity of PANi–CdS nanocomposites from 6.9?×?10^?6 to 3.14?×?10^?4 due to addition of CSA (10–50?%).     

Temperature dependence of graphene oxide reduced by hydrazine hydrate

Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95?°C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15?°C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp(2) structure after being reduced by hydrazine hydrate at high temperature (>60?°C), leading to the electric conductivity of GO increasing from 1.5 × 10(-6) to 5 S cm(-1), while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.     

Synthesis and characterization of gold cubic nanoshells using water-soluble GeO₂templates

Size-tunable GeO? nanocubes were initially prepared by a modified sono-assisted reverse micelle method and then functionalized with an amino-terminated silanizing agent. Subsequently, gold decorated GeO? nanocomposites were prepared at pH ≈ 7 and 80?°C. It was found that well-dispersed gold nanoparticles on GeO? nanocubes could be obtained only if gold salt is abundant to favor simultaneous, homogeneous nucleation of gold particles. Additional gold ions were reduced onto these attached 'seed' particles accompanied by synchronous dissolution of water-soluble GeO? cores, resulting in gold hollow cubic shells. The GeO? nanocubes and Au/GeO? nanocomposites as well as gold hollow cubic shells were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and UV-visible spectroscopy. In particular, gold hollow cubic shells feature a plasmon resonance peak at above 900 nm, which renders it quite promising in biochemical applications.     

Adsorption of carbon dioxide and methane on nanosized sodalite octahydrate zeolite

Nanosized sodalite octahydrate zeolite has been developed using a crystallization room temperature in the absence of organic templates. The best aging time found was 120?h and in this time the nanosized sodalite octahydrate zeolite is formed. The samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-Transform Infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and N₂ adsorption–desorption isotherm. The equilibrium adsorption capacities of pure gases CO₂ and CH₄ were measured at 298 and 308?K up to 20?bar on both powder and granules of sodalite octahydrate zeolite. With increasing temperature, the adsorption capacity decreases for both sodalite octahydrate zeolite powder and granules. The selectivity of CO₂ at 308?K over CH₄ was 6.53.     

Characterization of silver nanoparticles synthesized on titanium dioxide fine particles

Silver nanoparticles with a narrow size distribution were synthesized over the surface of two different commercial TiO(2) particles using a simple aqueous reduction method. The reducing agent used was NaBH(4); different molar ratios TiO(2):Ag were also used. The nanocomposites thus prepared were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), dynamic light scattering (DLS) and UV-visible (UV-vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopy studies (TEM and STEM) we observed that the silver nanoparticles are homogeneously distributed over the surface of TiO(2) particles and that the TiO(2):Ag molar ratio plays an important role. We used three different TiO(2)Ag molar ratios and the size of the silver nanoparticles is 10, 20 and 80?nm, respectively. It was found that the antibacterial activity of the nanocomposites increases considerably comparing with separated silver nanoparticles and TiO(2) particles.     

Transparent poly(methyl methacrylate)/ZnO nanocomposites based on KH570 surface modified ZnO quantum dots

Transparent luminescent ZnO embedded PMMA polymer has been synthesized by means of grafting poly(methyl methacrylate) (PMMA) onto the surface of ZnO QDs after g-methacryloxypropyl trimethoxy silane (KH570) modification. The resulting ZnO/PMMA nanocomposites with KH570-modified nanoparticles have better dispersibility and preserve the superior luminescence of ZnO nanoparticles in the nanocomposites. The obtained PMMA/ZnO nanocomposite films show high transparency, high UV-shielding efficiency and improved thermal stability. The obtained nanocomposite was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), X-ray powder diffraction (XRD), thermogravimetry (TG), ultraviolet-visible (UV-vis) absorption spectroscopy.     

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.     

Grafting of gold nanoparticles and nanorods on plasma-treated polymers by thiols

Grafting of gold nanoparticles and nanorods on the surface of polymers, modified by plasma discharge, is studied with the aim to create structures with potential applications in electronics or tissue engineering. Surfaces of polyethyleneterephthalate and polytetrafluoroethylene were modified by plasma discharge and subsequently, grafted with 2-mercaptoethanol, 4,4′-biphenyldithiol, and cysteamine. The thiols are expected to be fixed via one of –OH, –SH or –NH₂ groups to reactive places on the polymer surface created by the plasma treatment. “Free” –SH groups are allowed to interact (graft) with gold nanoparticles and nanorods. Gold nano-objects were characterized before grafting by transmission electron microscopy and UV–Vis spectroscopy. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electrokinetic analysis (zeta potential determination) were used for the characterization of polymer surface at different modification phases. It was proved by FTIR and XPS measurements that the thiols were chemically bonded on the surface of the plasma-treated polymers, and they mediate subsequent grafting of the gold nano-objects. On the surfaces, modified polymers were indicated some objects by AFM, size of which was dramatically larger in comparison with that of original nanoparticles and nanorods. This result and the other results of UV–Vis spectroscopy indicate an aggregation of deposited gold nano-objects.     

Growth of hydroxyapatite on physiologically clotted fibrin capped gold nanoparticles

The growth of hydroxyapatite (HAp) on physiologically clotted fibrin (PCF)-gold nanoparticles is presented for the first time by employing a wet precipitation method. Fourier transform infrared (FTIR) spectroscopy confirmed the characteristic functionalities of PCF and HAp in the PCF-Au-HAp nanocomposite. Scanning electron microscopy (SEM) images have shown cuboidal nanostructures having a size in the range of 70-300?nm of HAp, whereas 2-50?nm sized particles were visualized in high-resolution transmission electron microscopy (TEM). Energy-dispersive x-ray (EDX) and x-ray diffraction (XRD) studies have confirmed the presence of HAp. These results show that gold nanoparticles with PCF acted as a matrix for the growth of HAp, and that PCF-Au-HAp nanocomposite is expected to have better osteoinductive properties.     

Gold nanoparticle induces masking of amines and some therapeutic implications

Citrate capped gold nanoparticles (GNP) are effective in masking protein amines. The extent of such masking is quantified using Fourier Transform Infra Red (FTIR) spectroscopy. A strong correlation is shown to exist between a shift of amide-II peak intensity (1600-1500 cm(-1)) caused by GNP and the number of exposed amines in a given protein. The result is validated using eight different proteins. The expected out-come of such masking is inhibition of interaction between any external ligand and such amines. The prediction is validated using a simple non-enzymatic glycation of clinically important protein like crystallin.     

Hybrid composite material based on polythiophene derivative nanofibers modified with gold nanoparticles for optoelectronics applications

Conjugated polymers have been extensively applied as active materials in nanostructured platforms for optical and electrical devices. The incorporation of metal nanoparticles (NPs) into the polymer-based platform arises as a strategy to develop novel hybrid functional nanocomposites with enhanced electrical and optical properties. However, efficient and simple processing routes to produce such nanocomposites are still on demand. In this work, we present an effective route to obtain functional nanocomposites based on electrospun nanofibers coated with gold nanoparticles, displaying interesting optical and electrical properties. Polymethyl methacrylate (PMMA) electrospun nanofibers doped with poly(3-hexyl thiophene-2,5-diyl) (P3HT) were obtained by the electrospinning technique, and displayed a strong red emission centered at 650 nm assigned to P3HT. Such nanofibers were deposited on to fluorine-doped tin oxide electrodes and with modified with gold nanoparticles (AuNPs) in order to produce hybrid composite materials. The performance of electrodes modified with PMMA/P3HT-AuNPs composite material was evaluated by impedance spectroscopy and revealed an enhancement of electron transfer kinetics, which indicates it as a potential platform for optical and electrochemical (bio)sensors.     

Synthesis of metallic nanoparticles protected with N,N,N-trimethyl chitosan chloride via a relatively weak affinity

A water-soluble cationic chitosan derivative, N,N,N-trimethyl chitosan chloride (TMC), was synthesized and used as a stabilizing reagent for the synthesis of highly stable Au, Ag and Pt nanoparticles in a single-phase of neutral aqueous solution. The morphology and stability of metallic nanoparticles were evaluated by transmission electron microscopy and UV-vis spectroscopy. The results showed that well-dispersed metallic nanoparticles have a spherical morphology with diameters of about 3 ± 0.5?nm. The prepared gold nanoparticles are stable in the aqueous solution (no significant changes in their morphology and size within 10?months) due to repulsion between the charged polymer shell coatings around the metallic nanoparticles. The relatively low affinity of TMC on gold nanoparticles was confirmed by using a ligand exchange experiment. The mechanism stabilizing the chitosan derivative and the neighbouring gold nanoparticles was identified by FTIR, (1)H NMR and (13)C NMR measurements.