Nanoscale structuration and optical properties of thin gold films on textured FTO

In this work, we propose a methodology to synthesize metallic nanoparticles on textured Fluorine Tin Oxide (FTO) surface by laser irradiations of deposited Au films. In particular, the breakup of the Au films into nanoparticles (NPs) is observed as a consequence of the melting and solidification processes induced by laser irradiations. The mean Au NPs size and surface density evolution are analyzed as a function of the laser fluence. Optical characterizations of the glass/FTO/Au NPs multilayer show, in the absorption spectra, plasmonic peaks due to the Au NPs and an improvement of the light absorption efficiency from the sample with larger Au NPs. The simulated trends of the ratio between the scattering and absorption cross section suggest that the absorption efficiency dominates over the scattering efficiency in the spectral range between 200 and 600 nm. The simulation shows that, by varying the NPs radius from about 18 to 24 nm, the radiation-scattered intensity remains symmetric in forward and reverse directions. These results indicate that the surface coverage size distribution of Au NPs is the key parameter to correlate the structural and optical properties of the glass/FTO/Au NPs multilayer. Furthermore, electrical characterizations highlight a reduction in the sheet resistance of the textured FTO due to the presence of the NPs. We compare these results with those obtained for the same systems when standard furnace annealing processes are used to obtain the Au NPs on the textured FTO surface.     

Synthesis,characterization, photocatalytic and reusability studies of capped ZnS nanoparticles

This paper presents results of a study on the structural and morphological properties of 2-mercaptoethanol (2-ME) capped ZnS nanoparticles (NPs). The photocatalytic and reusability study of the synthesized NPs to degrade dyes was also done. ZnS semiconductor NPs were synthesized via chemical precipitation route using 2-ME as a stabilizing agent. The as-prepared NPs were characterized by X-ray diffraction (XRD) technique to confirm the nanometer sized particle formation. Morphological features of capped ZnS NPs were determined by transmission electron microscopy (TEM). Dynamic light scattering (DLS) technique was used to determine the hydrodynamic size of capped ZnS NPs. UV-Vis studies were done to determine the absorption edge and bandgap of the capped ZnS NPs. Fourier transform infrared spectroscopy (FT-IR) studies were done to confirm the presence of 2-ME on the surface of NPs. Photocatalytic studies of the as-prepared ZnS NPs were done by taking Ponceau S and crystal violet dyes as model pollutants. Their comparative degradation behaviour has been discussed. Reusability study of ZnS NPs was done to ensure its applicability as recycled catalyst in photocatalysis. The result showed photocatalytic enhancement of reused catalyst. Possible reason has been discussed in this work.     

Toward p-type conduction in Cs-doped ZnO: an eco-friendly synthesis method

An alcohol-free, eco-friendly technique was adapted for the synthesis of undoped ZnO and Cs-(cesium) doped ZnO nanoparticles (NPs). The effect of annealing and dopant concentration on its structural and optical properties was investigated. X-ray diffraction results confirmed the formation of polycrystalline hexagonal wurtzite structure and enhanced crystallinity was observed for 1 mol%: Cs-doped ZnO NPs. Scanning electron microscopy results revealed triangular-shaped NPs and increase in the crystallite size is noticed with increase in dopant concentration. UV–visible results showed shift in the band edge toward higher wave length side with increasing Cs concentration. Reduction in bandgap was observed for Cs-doped ZnO NPs, due to quantum confinement effect. Transmittance value increased to 86 % with the inclusion of Cs in ZnO lattice. Room temperature photoluminescence analysis of Cs-doped ZnO NPs reveals bandedge emission along with 450 nm emission due to Zn vacancy and Zn interstitial defects. Electrical measurements confirmed the realization of p-type conductivity in Cs-doped ZnO NPs with a carrier concentration of 1.3 × 10¹⁸/cm³.     

Optical properties of Er3+–Ag co-doped ZnO nanocrystals prepared by combustions method

The Er³⁺–Ag co-doped ZnO nanocrystals have been synthesized by citric acid-assisted combustions method. The effect of different concentration of silver nanoparticles (NPs) on Er³⁺ doped ZnO nanocrystals and the optical behaviors are explored. The nanocrystals were characterized by X-ray diffractions, scanning electron microscopy, UV–Vis–NIR absorption spectra, X-ray photoelectron spectroscopy, and photoluminescence, respectively. The luminous intensity of Er³⁺ doped ZnO nanocrystals was significantly influenced by the concentration of silver NPs. A large enhancement in up-conversion intensity has been observed when the concentration of silver NPs was 0.10 mol%. The effect of localized surface plasmon resonance of silver NPs and the energy transfer between the silver NPs and Er³⁺ ions (²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2) are discussed as the sources of enhancement or quenching.     

Janus nanofiber: a new strategy to achieve simultaneous enhanced magnetic-photoluminescent bifunction

Magnetic-photoluminescent bifunctional Janus nanofibers have been successfully fabricated by electrospinning technology using a homemade parallel spinneret. NaYF₄:Eu³⁺ and Fe₃O₄ nanoparticles (NPs) were respectively incorporated into polyvinyl pyrrolidone (PVP) and eleactrospun into Janus nanofibers with NaYF₄:Eu³⁺/PVP as one strand nanofiber and Fe₃O₄/PVP as another strand nanofiber. The morphologies, structures, magnetic and photoluminescent properties of the as-prepared samples were investigated in detail by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, vibrating sample magnetometry and fluorescence spectroscopy. The results show Janus nanofibers simultaneously possess superior magnetic and luminescent properties due to their special structure, and the luminescent characteristics and saturation magnetizations of the Janus nanofibers can be tuned by adding various amounts of NaYF₄:Eu³⁺ NPs and Fe₃O₄ NPs. Compared with Fe₃O₄/NaYF₄:Eu³⁺/PVP composite nanofibers, the magnetic-photoluminescent bifunctional Janus nanofibers provide better performances due to isolating NaYF₄:Eu³⁺ NPs from Fe₃O₄ NPs. The novel magnetic-photoluminescent bifunctional Janus nanofibers have potential applications in the fields of new nano-bio-label materials, drug target delivery materials and future nanodevices owing to their excellent magnetic and luminescent performance. More importantly, the design conception and construction technology are of universal significance to fabricate other bifunctional Janus nanofibers.     

Highly oriented single-phase blend films of high- and low-density polyethylene

The microstructures of highly oriented drawn films of blends of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) were investigated by transmission electron microscopy, electron diffraction, X-ray diffraction, and differential scanning calorimetry (DSC). The average crystal size, as well as long period, crystalline content, and melting endotherm peak, decreased as LDPE was added to the blend. When the LDPE content exceeded ～ 50%, the film texture changed from a single crystal texture to fibre symmetric. Segregation of the two polyethylenes was not detected at low LDPE contents in as-drawn or melted and recrystallized films. In the as-drawn films, a low temperature tail began to appear on endotherm melting peaks at LDPE contents ?70%, indicating the onset of segregation. In meltcrystallized films, however, two distinct melting endotherm peaks were visible for LDPE contents ?50%. An equilibrium melting point of 141° C and end surface free energy of 101 erg cm^?2 (101 × 10^?7 J cm^?2) were determined by use of the Thomson equation. The close agreement between these values and literature values for HDPE suggested that the crystals present in HDPE/LDPE blends were thermodynamically equivalent to HDPE crystals of equal size, implying that branches were excluded from the crystalline phase.     

Effects of SEBS-g-MA copolymer on non-isothermal crystallization kinetics of polypropylene

The non-isothermal crystallization kinetics of pure PP and PP/SEBS-g-MA blends up to volume fraction, Φ _d (0–0.50) was studied by differential scanning calorimetry at four different cooling rates. Crystallization parameters were analyzed by Ozawa and Liu models. The Ozawa model fits in the PP/SEBS-g-MA blends and indicates the effect of SEBS-g-MA copolymer on the crystallization process of polypropylene. Augis–Bennet model has been used to calculate activation energy, ?E, during non-isothermal crystallization process. The value of ?E decreased with SEBS-g-MA due to flexibility of SEBS-g-MA by which movements of chains of PP become easier.     

Asphalt concrete modification with waste PMMA/ATH

This paper presents recycling of waste PMMA/ATH powder in asphalt concrete mixture. Waste PMMA/ATH is generated in large amounts during shaping process of acrylic sheets. Recycling waste polymers rationally and efficiently has become one of the priorities of road pavement industry in recent years. Therefore, in this study waste PMMA/ATH powder was incorporated in an asphalt mixture. In one case waste PMMA/ATH was used as an asphalt binder modifier and in other case as a partial replacement for fine aggregate fraction. Basic performance characteristics of asphalt mixtures were evaluated by measuring material properties such as rutting potential and stripping resistance. Binder characteristics were determined also on artificially aged samples. With both modification methods, improved performance characteristics of asphalt mixture were achieved which can increase road pavement durability. Finally, waste PMMA/ATH allowed us to prepare an asphalt mixture that had strongly enhanced mechanical properties regarding to the wheel tracking test and could also have less negative effects on the environment as indicated by moisture susceptibility test results.     

Investigation of phase intergrowth morphologies in the system Zn2SiO4-SiO2 by photo-emission electron microscopy

By means of photo-emission electron microscopy, which is described briefly, X-ray diffraction and electron microprobe analysis the hypo- and hypereutectic solidification in the system Zn₂SiO₄-SiO₂ has been investigated. Faceted (idiomorphic) growth of stableα? and metastableΒ-zinc silicate with some excess SiO₂ on the hypoeutectic side of the phase diagram and a metastable region of liquid immiscibility on the SiO₂-rich (hypereutectic) side determine the respective phase intergrowth morphologies. Unconstrained eutectic solidification causes a “divorced eutectic” where the zinc silicate constituent grows first from the undercooled liquid, which is simultaneously enriched in SiO₂.     

Flux growth of silicates with vapour transported silicon

As a result of a proposed vapour transport mechanism, silicate crystals have been grown from fluxed melts which originally contained only trace amounts of silicon. The melts were contained in platinum crucibles in a sillimanite, Al₂SiO₅, muffle, and the flux consisted of PbF₂, or PbF₂ + PbO, occasionally with additional MoO₃. It is postulated that a volatile siliceous species resulted from the reaction of PbF₂ vapour with the muffle and that this species transported Si into the fluxed melts. The silicate crystals produced include Er₂SiO₅, Dy₂SiO₅, Mg₂SiO₄·MgF₂, a new material of formula Dy₄SiO₈, and several new rare earth compounds with the apatite structure.     

Structure of reconstituted collagen hollow fibre membranes

Small- and wide-angle X-ray scattering (SAXS and WAXS) methods were employed to study the structure of reconstituted collagen hollow fibre membranes and the changes that ensue upon entry of water. The tails of the SAXS curves were analysed and were shown to obey Porod's Law. WAXS and water absorption measurements as a function of relative humidity were combined with density measurements to determine the relative volume fractions of water in the “free” and “bound” states. Treating the hollow fibre as a two phase system and employing Porod's Law, average length parameters transverse to the fibre axis were extracted for the collagen fibrils and the water filled pores. All this information was synthesized to yield a model of the structural changes in the hollow fibre caused by water. Implications of such a model for qualitative and quantitative prediction of changes in properties were studied.     

Low temperature crystallization of glasses in the H2O-NaCl-dimethyl sulphoxide ternary system

The determination and application of ternary H₂O-NaCl-cryoprotective agent phase diagram information appears to offer materials scientists and biologists a unique opportunity for co-operative research. Dimethyl sulphoxide (DMSO) is a widely used cryoprotective agent and in this investigation the H₂O-NaCl-DMSO system appears to develop a glassy phase even at relatively low cooling rates (25°C min^?1) for those water-rich compositions where the ratio of DMSO to NaCl varies from 2 to 1/2. This glassy phase is relatively unstable and the kinetics of the glass-to-crystalline phase transition have been investigated and shown to be first order. Activation energies (Q) and the times required for the completion of this first order transformation have been evaluated by differential thermal analysis. Such information may be useful in interpreting the effects of long term storage on rapidly frozen biological materials perfused with DMSO.     

Synthesis,structural and optical characterization of ZrO2 core–ZnO@SiO2 shell nanoparticles prepared using co-precipitation method for opto-electronic applications

Nanocrystalline Zirconia (ZrO₂) and Zinc oxide (ZnO) as well as Silica (SiO₂) coated ZrO₂ core–shell structures were synthesized by both Co-precipitation and seeded polymerization technique. The phase analysis and the core–shell structure formation were confirmed by X-ray diffraction (XRD), FESEM and high resolution transmission electron microscopy (HRTEM) analysis. The existence of SiO₂ on ZrO₂@ZnO was characterized by FT-IR measurement. UV–Vis study reveals coating of ZnO over Zirconia shows red shift in the absorption spectra. Photoluminescence studies show the non-monotonous variation in luminescence behavior of these core–shell nanoparticles. This investigation explains that the interfacial effect between the core (ZrO₂) and the shell materials (ZnO and SiO₂) can be exploited to tune the optical properties of the material. This implies that we can envisage the core–shell materials as potential candidates for optical–electronic devices.     

An infrared spectroscopic study of vacuum-evaporated SiO-CeO2 thin films

Infrared spectra of vacuum-evaporated SiO-CeO₂ thin films are reported for a series of thin films of varying compositions. They show a systematic shift of the SiO “O stretch” frequency from a value of 1040 cm^?1 in the pure (100 mol %) SiO film to 950 cm^?1 in the 16 mol % SiO84 mol % CeO₂ film, as well as a gradual diminishing of the band at 876 cm^?1 with increasing CeO₂ concentration. After introducing the general perspective for the analysis of the infrared spectra of amorphous solids, and tetrahedrally bonded compounds in particular, it is proposed that the first two features of the spectra result from a chemical association between nonbridging oxygen atoms of the SiO network and cerium atoms. This entails the interpretation of the band at 876 cm^?1 as being due to the stretching vibrations of the non-bridging oxygen atoms. The effect of annealing on the spectra is also presented and explained in terms of creation of new Si-O-Si linkages.     

Synthesis and characterization of a new type of electro-optic polymer without carbon main chains

A new type of electro-optic (EO) polymer is prepared in this work. The main chain of the EO polymer is made of polyphosphazenes, and the side chain consists of carbazole based nitro azobenzene. The principle and method of preparation are given and the characteristics of this material are studied in details. The polymer with an EO coefficient of 35 pm/V has fine stability and can be easily processed. It also shows photoconductivity due to the carbazole group. This polymer thin film is obtained through performance improvement. Terahertz (THz) wave can be detected using the device, which is made of the new polymer. Owing to its fascinating properties, this new type of EO polymer has the potential to be widely applied in photorefractive materials as well as for emission and detection of THz radiation.     

Mechanical property enhancement of PVDF/graphene composite based on a high-quality graphene

In this paper, we adopted hot-pressing treatment to convert the regular reduced graphene oxide (RGO) from chemical exfoliation to the high-quality graphene (HQG), and then the HQG/poly vinylidene fluoride (PVDF) composite films were prepared by spin coating. The microstructural characterizations and property measurements revealed that (1) The HQG was free of defects and oxygen-containing functional groups on the surface, and exhibited a homogeneous dispersion and a well composite with PVDF; (2) The storage modulus of the HQG/PVDF composite was nearly twice higher than that of RGO/PVDF composite, and eight times higher than that of pure PVDF; and (3) The optimum additive amount of HQG with PVDF was at between 3 and 5 wt%. It is expected that the present HQG has a potential applications in polymer composites.     

Tensile failure mechanisms in carbon fibre reinforced plastics

Tensile failure mechanisms in type I carbon fibre-reinforced epoxy resin have been studied by examining the modes of failure of cured and semi-cured CFRP and of fibre bundle specimens. The rigid matrix in the cured material modified the appearance of the fractured specimen but by detecting the acoustic emission generated during loading the basic fibre bundle behaviour was found to exert a major influence on fracture. Microscopic examination of fractured CFRP specimens has revealed that consecutive fibre failure may be restricted to sub-bundles as a result of shearing between these sub-bundles, and that the material is weakened by a number of internal failures that are not necessarily connected. Ultimate failure seems to be statistically determined and it is a characteristic of the material that some scatter in the strength of CFRP must be expected.     

Performance improvement of pentacene organic field-effect transistor through introducing polymer buffer layers

Pentacene organic field-effect transistors (OFETs) employing poly(methyl methacrylate) (PMMA), polystyrene and polyvinylidene fluoride as the electrode buffer layers by simple spray-coating fabrication process were systematically investigated. Significant performance enhancement of the OFETs was obtained. By analyzing the morphologies of pentacene films grown on gold electrodes and the electrical characteristics of these OFETs, the performance improvement was attributed to the uniform and hydrophobic properties of polymer surface, leading to a remarkable reduction of contact resistance at the pentacene/electrodes interface. Moreover, the results showed that the device employing PMMA as the electrode buffer layer exhibited the highest hole mobility of 0.59 cm²/Vs, which was almost five times of the control one. Such effect was ascribed to the optimal surface energy and appropriate dielectric constant of PMMA, which were favorable for the growth of pentacene crystal and responsible for the highest performance of OFET using PMMA as the electrode buffer layer.     

Study on electromechanical characterization of piezoelectric polymer PVDF in low-frequency band

Polyvinylidene fluoride (PVDF), a piezoelectric polymer material, is well known as one of the best smart materials to be used for tactile sensors in robots for its good performance. It has been used in many applications including sensors, actuators and surface acoustic wave (SAW) devices. This paper presents an experimental setup and experimental procedures for studying the electromechanical characterization of piezoelectric polymer films, by which the electromechanical characterization of the PVDF films under quasi-static loads and dynamic loads in a wide range of frequency can be researched. Through quasi-static tests, the stress–strain relationships of PVDF films in different directions were obtained. Furthermore, the viscoelastic and piezoelectric properties of PVDF films were analyzed based on the measurement results of dynamic tests under low frequency from 5 Hz to 200 Hz, and some suggestions of the applications of PVDF piezoelectric films in robot tactile sensor are presented.     

Interfacial energetics in the TD-nickel and TD-nichrome systems

The absolute (mean) interfacial free energies are measured in thoria-dispersed (2 vol %) (TD)-nickel and the TD-nichrome (Ni-20% Cr) systems at 1200° C utilizing techniques of scanning electron and transmission electron microscopy. Values of particle/matrix interfacial energies for TD-NiCr and TD-Ni were measured at 2300 and 2000 erg cm^?2 respectively based upon measured values of 2040 and 2200 erg cm^?2 for the surface free energies for nichrome (80∶20 NiCr) and pure nickel respectively, by the method of zero creep and the measurement of grain-boundary groove angles in the electron microscope. Values of 900 erg cm^?2 and 1040 erg cm^?2 were measured for the surface and grain-boundary free energies for thoria (ThO₂). The particle/matrix adhesive energy for TD-nichrome was measured to be roughly half that for the TD-nickel system based upon the classical interfacial adhesion concept. It is concluded that the apparent difference in particle/matrix interfacial strength between TD-nickel and TD-nichrome results by a more complex mechanism than simple interfacial decohesion involving phase separation.