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Nanocomposite films grown on a silica slide substrate are a suitable model for developing and, eventually, improving optical devices. Here optical properties of silver nanoparticle (AgNP) films coated with Eu3+ complex, grown directly on a silica slide substrate, were studied. The growth of the film was done by functionalizing the silica slide surface with an organosilane molecule, 3-Aminopropyltriethoxysilane (APTES), by covalent bonding, followed by Ag+ interaction with subsequent reduction process, resulting in a yellow film typical of silver nanoparticles (NPs). Then, in the next step, to form the nanocomposite, the AgNP film was coated with the Eu3+ complex. The X-ray diffraction (XRD) peak characteristic of silver in the cubic face-centered phase (plane 111) was identified and transmission electron microscopy (TEM) images confirmed that AgNPs bound to the silica substrate. The UV–Vis spectra displayed a plasmon absorption band, which was widened and slightly shifted to a higher wavelength due to the Eu3+ complex presence. Furthermore, the Eu3+ complex emission was increased in the AgNP film due to metal enhanced fluorescence (MEF). In order to exploit these emission properties, in some luminescent devices, the nanocomposite must be assembled in solid films. These changes in the optical properties of AgNP films when interacting with the Eu3+ complex are of great perspective for applications in optical devices, and this luminescent thin film configuration is an interesting system to explore nanocomposite materials. [ABSTRACT FROM AUTHOR]

Abstract A simple and versatile route to synthesize nanocomposite thin films containing polythiophene, gold nanoparticles and carbon nanotubes is demonstrated. The strategy is based on a liquid-liquid interfacial reaction, in which polythiophene and gold nanoparticles are concomitantly synthesized through a reaction between an aqueous solution of tetrachloroauric acid and a n-hexane solution of thiophene containing carbon nanotubes previously dispersed. The three-component nanocomposite is obtained directly as a thin and homogeneous film, self-assembled at the liquid-liquid interface, and easily transferable to ordinary substrates. Different reaction times were investigated, and the materials were characterized by several techniques, such as SEM, TEM, profilometry and EDS to inform about the morphology and the elementary composition, FTIR, Raman, TGA, UV–Vis and DRX about the structure of the materials and the electrochemical properties were investigated by cyclic voltammetry. The presence of carbon nanotubes accelerates the reaction, yielding greater amount of product when compared to similar reactions conducted without the carbon nanotubes. The proportion between the components, amount of products and film thickness can be controlled by the reaction time. It is observed that the amount of both polythiophene and gold nanoparticles increases with the increasing reaction time, inducing the formation of polymer agglomerates over de carbon nanotubes and the anisotropic growth of gold nanoparticles. The presence of CNT increases the electrochemical stability of the films when compared to similar ones without CNT. The potentiality of the prepared nanocomposite as electrochemical sensor was evaluated for voltammetric determination of dopamine. Best results were found for a PT/Au/CNT film prepared after 4.5 h of reaction, with a limit of detection of 0.69 μmol L−1. Graphical abstract Unlabelled Image Highlights • Direct and one-pot synthesis and processing of multifunctional material as thin films. • Innovative technique to prepare thin film of a multi-component material impossible to be done using conventional routes. • Optical and electrochemical properties of materials designed by the synthesis. • Large potentiality as electrochemical sensor demonstrated by dopamine electrochemical sensing. [ABSTRACT FROM AUTHOR]

This work demonstrates a simple and one-step synthesis of polythiophene/gold nanoparticles (PT/Au) nanocomposite thin films, through a liquid–liquid (L/L) interfacial polymerization route. Starting from an aqueous solution of tetrachloroauric acid (acting both as metallic gold source and oxidizing agent to start the oxidative polymerization of thiophene), and a solution of thiophene in n-hexane, a biphasic L/L system was originated. In the following, the interface acted as a meeting-point for the reactants, and the polymerization reaction took place, leading to self-assembled PT/Au film between the two immiscible liquids. These films were easily deposited over different substrates (glass, silicon, plastics) and characterized through different techniques. The influence of both the reactants ratio and the reaction time on the structure and morphology of the films were evaluated. The films obtained with a shorter reaction time exhibited spherical gold nanoparticles (around 3 nm diameter) homogeneously dispersed into a polymeric matrix. The increase of both the reaction time and the thiophene/gold precursor ratio led to agglomerated and anisotropic gold structures wrapped by a thin layer of polythiophene. Overall, PT/Au films are transparent, homogeneous, stable, flexible and presented reversible electrochromic properties, which make them suitable for application in different systems and devices, as demonstrated here for electrochromic application. [ABSTRACT FROM AUTHOR]

An innovative, single-pot synthesis for chemically producing graphene/polyaniline nanocomposites is presented. The method, which is based on chemical reactions at liquid-liquid interfaces, begins with benzene and aniline and ultimately yields nanocomposites as thin films of polyaniline mixed with graphene. These films self-assembled at the water-benzene interface are easily transferable to any kind of ordinary substrates, plastics included. Nanocomposites prepared with different polymer/graphene ratios show differentiated structures and morphologies, resulting in excellent pseudocapacitive behaviors (specific capacitance of 267.2 F cm −3 ). The construction of all-solid, transparent, and flexible supercapacitor device from this nanocomposite is also presented. [ABSTRACT FROM AUTHOR]

Hexagonal close packed (hcp) nickel nanoparticles stabilized by polyvinylpyrrolidone (PVP) were synthesized through the thermal treatment of face centered cubic (fcc) nickel nanoparticles. Controlling both the temperature of the heat treatment and the amount of PVP was possible the control of the hcp/fcc rate in the samples, where the higher Ni/PVP ratio produces only the hcp-nickel phase (average size of 8.9 nm) highly stable in air. The crystalline structure, the presence of PVP, the size of the nanoparticles and the stability of the hcp-nickel were confirmed using X-ray diffractometry, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy, scanning electron microscopy and thermogravimetric analysis. Thin films of hcp and fcc nickel nanoparticles were prepared through a biphasic system and deposited over indium-doped tin oxide (ITO) substrates, which were electrochemically characterized and applied as glycerol amperometric sensors in NaOH medium. Parameters as the number of cycles applied and the scan rate were evaluated and indicate that hcp nickel nanoparticles are more reactive to form Ni(OH) 2 and lead to more electroactive Ni(OH) 2 structure. The hcp nickel nanoparticles-modified electrode showed the best sensitivity (0.258 μA L μmol −1 ) and detection limit (2.4 μmol L −1 ) toward glycerol. [ABSTRACT FROM AUTHOR]

We report here the synthesis and characterization of transparent and homogeneous thin films of reduced graphene oxide/silver nanoparticles (rGO/AgNPs) nanocomposites, starting from graphene oxide (GO) or reduced graphene oxide (rGO), directly obtained at a water/toluene liquid–liquid interface. Different films (obtained by varying the Ag/rGO or Ag/GO ratio) were prepared, deposited over glass or plastic substrates, and characterized by X-ray diffraction, UV–Vis and Raman spectroscopy, thermal analysis, transmission and scanning electron microscopy. Samples were evaluated as substrates for surface-enhanced Raman spectroscopy (SERS), using dilute solutions (1 × 10 −7 mol L −1 ) of a common probe molecule, 4-aminothiophenol (4-ATP). These materials exhibit significant high-quality SERS activity, and enhanced modes could be observed for 4-ATP, which suggested that charge transfer occurred between the Ag nanoparticles and 4-ATP molecules. [ABSTRACT FROM AUTHOR]

Abstract: The present work describes for the first time the synthesis and characterization of single wall carbon nanotubes/polyaniline (SWNTs/PAni) nanocomposite thin films in a liquid–liquid interface, as well as the subsequent construction of a flexible all-solid supercapacitor. Different SWNTs/PAni nanocomposites were prepared by varying the ratio of SWNT to aniline, and the samples were characterized by scanning and transmission electron microscopy, Raman and UV–Vis spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The pseudo-capacitive behavior of the nanocomposites was evaluated by charge/discharge galvanostatic measurements. The presence of the SWNTs affected the electronic and vibrational properties of the polyaniline and also improved the pseudo-capacitive behavior of the conducting polymer. A very thin and flexible all-solid device was manufactured using two electrodes (polyethylene terephthalate-PET covered with the SWNT/PAni nanocomposite separated by a H2SO4-PVA gel electrolyte). The pseudo-capacitive behavior was characterized by a volumetric specific capacitance of approximately 76.7 F cm−3, even under mechanical deformation, indicating that this nanocomposite has considerable potential for application in new-generation energy storage devices. [Copyright &y& Elsevier]

Abstract: The optical, electrical and structural properties of thin film tin oxide (TO), F-doped tin oxide (FTO; n F ≈6×1020 cm−3) and highly F-doped tin oxide (hFTO; n F ≈10×1020 cm−3), grown by spray pyrolysis technique, are studied by atomic force microscopy, Hall effect, X-ray fluorescence and transmission/reflection measurements. The resistivity (ρ =32×10−4 Ωcm for intrinsic tin oxide) shows intriguing characteristics when F concentration n F is increased (ρ =6×10−4 Ωcm for FTO but 25×10−4 Ωcm for hFTO) whereas the carrier concentration is almost constant at high F concentration (n c ≈6×1020 cm−3 for FTO and hFTO). Thus, F seems to act both as a donor and a compensating acceptor in hFTO. The high carrier concentration has a strong effect on the optical band-edge absorption. Whereas intrinsic TO has room-temperature band-gap energy of E g ≈3.2eV with an onset to absorption at about 3.8eV, the highly doped FTO and hFTO samples show relatively strong absorption at 2–3eV. Theoretical analysis based on density functional calculations of FTO reveals that this is not a defect state within the band-gap region, but instead a consequence of a hybridization of the F donor states with the host conduction band in combination with a band filling of the lowest conduction band by the free carriers. This allows photon-assisted inter-conduction band transitions of the free electrons to energetically higher and empty conduction bands, producing the below-gap absorption peak. [Copyright &y& Elsevier]