TiO2 microspheres (TMS) with perfect spherical morphology were synthesized by spray drying of a hydrothermally cured aqueous suspension of TiO2 nanoparticles. TiO2 powders (TP) obtained by drying the nanoparticle suspension were studied simultaneously to determine which was the most efficient photocatalyst. SEM images and laser granulometry on TMS show spherical morphology with the diameter ranging from 2 to 10 mu m. TMS had high specific surface area after annealing as seen from BET analyses. XRD analyses show that TMS consist of anatase and rutile crystalline phases where the rutile fraction increases with annealing temperature and above 500 degrees C rutile dominates anatase. Raman spectroscopy shows several Raman bands from anatase and rutile phases and supports the XRD results of phase transformation with increasing annealing temperature. Photodegradation of organic pollutants in aqueous solution under UV light irradiation establishes the higher photocatalytic activity of TMS with respect to TP. The highest efficiency was found on the 400 degrees C annealed TMS.

In this study, we examine at both experimental and fundamental levels, the experimental evidence of nanoparticle formation in transmission electron microscopy (TEM) metal grids annealed at temperatures lower than the melting point of the corresponding metal bulk material. Our experimental investigation considers the most thermally unstable TEM grids (i.e. Cu-grids) and inspects the possible sources and mechanisms of contamination of thin films, conventionally deposited on carbon-coated Cu-grids. The investigations are supported by morphological-compositional analyses performed in different regions of the TEM sample. Then, a general model is formulated and discussed in order to explain the grid thermal instability, based on the critical role of edge-melting (i.e. melting initiated at edges and corners of the grid bars), the enhanced rate of evaporation from a liquid surface and the polycristallinity of the grid bars. Hence, we totally disregard conventional arguments such as bulk evaporation and metal vapor pressure and, in order to emphasize and clarify the alternative point of view of our model, we also overview the nano-scale melting phenomenology relevant to our discussion and survey the discrepancies reported in the literature. (C) 2016 Elsevier B.V. All rights reserved.

In this paper we report on the effects of the insertion of Cr atoms on the electrical and optical properties of indium tin oxide (ITO) films to be used as electrodes in spinpolarized light-emitting devices. ITO films and ITO(80 nm)/Cr-doped ITO(20 nm) bilayers and Cr-doped ITO films with a thickness of 20 nm were grown by pulsed ArF excimer laser deposition. The optical, structural, morphological wand electrical properties of ITO films and ITO/Cr-doped structures were characterized by UV-Visible transmission and reflection spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Hall-effect analysis. For the different investigations, the samples were deposited on different substrates like silica and carbon coated Cu grids. ITO films with a thickness of 100 nm, a resistivity as low as similar to 4 x 10(-4) Omega cm, an energy gap of similar to 4.3 eV and an atomic scale roughness were deposited at room temperature without any post-deposition process. The insertion of Cr into the ITO matrix in the upper 20 nm of the ITO matrix induced variations in the physical properties of the structure like an increase of average roughness (similar to 0.4-0.5 nm) and resistivity (up to similar to 8x10(-4) Omega cm). These variations were correlated to the microstructure of the Cr-doped ITO films with particular attention to the upper 20 nm.

Brookite titanium dioxide (TiO2) nanorods. synthesized by a surfactant-assisted aminolysis route, were used as precursors for the fabrication of thin films by using the matrix-assisted pulsed-laser deposition (MAPLE) technique. Thin films with controllable thickness were grown on a variety of substrates for different characterizations. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of rough TiO2 films incorporating individually distinguishable nanocrystals with different shapes. Suitable alumina substrates equipped with interdigitated electrical contacts (IDC) and heating elements were used to fabricate gas-sensing devices based on resistive transduction mechanism. Electrical characterization measurements in controlled environment were carried out. Typical gas sensor parameters (such as gas response, sensitivity, stability and detection limit) towards selected oxidizing and reducing gases, namely NO2 and CO, respectively, were extracted in dark condition. Very interesting optically activated enhancement of the response towards NO2 oxidizing gas was achieved in controlled atmosphere upon irradiating the sensing layer with UV light with low energy close to the TiO2 sensing layer band-gap width. (C) 2011 Elsevier B.V. All rights reserved.

Pd nanoparticles generated onto gel type ion-exchange resins under catalytic conditions show high activity, selectivity and durability in partial hydrogenation reactions under mild condition, thus providing a green, low-cost option to fine-chemicals production. The application to the continuous-flow synthesis of the leaf alcohol fragrance cis-3-hexen-1-ol is demonstrated.

As electronic devices get smaller and more powerful, energy density of energy storage devices increases continuously, and moving components of machinery operate at higher speeds, the need for better thermal management strategies is becoming increasingly important. The removal of heat dissipated during the operation of electronic, electrochemical, and mechanical devices is facilitated by high-performance thermal interface materials (TIMs) which are utilized to couple devices to heat sinks. Herein, we report a new class of TIMs involving the chemical integration of boron nitride nanosheets (BNNS), soft organic linkers, and a copper matrix - which are prepared by chemisorption coupled electrodeposition approach. These hybrid nanocomposites demonstrate bulk thermal conductivities ranging from 211 to 277 W/(m.K), which are very high considering their relatively low elastic modulus values on the order of 21.2 to 28.5 GPa. The synergistic combination of these properties lead to the ultra-low total thermal resistivity values in the range of 0.38 to 0.56 mm2.K/W for a typical bondline thickness of 30-50 µm, advancing the current state-of-art transformatively. Moreover, its coefficient of thermal expansion (CTE) is 11 ppm/K, forming a mediation zone with a low thermally-induced axial stress due to its close proximity to the CTE of most coupling surfaces needing thermal management.

This study describes the preparation of ion-imprinted polymers (IIPs) for the selective removal of Hg(II) ions from aqueous media. Polymeric sorbents were prepared using different synthesis approaches to understand the influence of diphenylcarbazone (DPC), used as non-polymerizable ligand, on absorption performance. In particular, bulk polymerization was first used to prepare two polymers, IIP1 and IIP2, in the absence and presence of DPC. The trapping of the ligand in IIP2, demonstrated by Fourier Transform Infrared Spectroscopy, promotes the formation of ternary complexes with mercury ions, and 4-vinylpyridine induces an increase in binding performance, as indicated by the K-a values (1.7 x 10(3) +/- 0.4 M-1 and 12.1 x 10(3) +/- 0.5 M-1, respectively) of IIP1 and IIP2 high affinity binding sites. A third polymer (IIP3) was also synthesized using precipitation polymerization to evaluate the contribution of morphological characteristics on absorption performance compared with the addition of DPC. Competitive studies revealed a stronger influence of IIP3 morphology on selectivity performance. Indeed, monodisperse microbeads were obtained only in this case. Finally, the applicability of the polymers to real-world samples was demonstrated through batch experiments using drinking water spiked with 1 mu g ml(-1) of Hg(II) ions, and the best removal efficiency of nearly 80% was obtained for IIP2.

In this paper we report on optical absorption measurements performed on several metal oxide nanoparticles (ZnO, CeO2, Fe2O3) as a function of temperature in the range 25500 °C, in order to study the optical properties, and to investigate how several heating cycles could affect nanoparticle structural stability and absorption characteristics. These are quite important issues to be investigated in order to assess the possibility to use such metal-oxide nanoparticles as gas-based high temperature nanofluid in concentrated solar power (CSP).

This work reports the inherent peroxidase-like properties of Ruthenium (Ru) nanoframes. After templating with Palladium (Pd) seeds, Ru nanoframes with an octahedral shape, average edge length of 6.2 nm, and thickness of 1.8 nm were synthesized in high purity (>95 %) and good uniformity. Using the oxidation of 3,3',5,5'-tetram-ethylbenzidine (TMB) by H2O2 as a model catalytic reaction, the Ru frames were demonstrated to be approximately three times more active than natural peroxidases in catalyzing the formation of colored products. As compared to their natural counterparts, Ru frames have a stronger binding affinity to TMB as well as a weaker binding affinity to hydrogen peroxide during the catalysis. The Ru frames as peroxidase mimics proved to be chemically and thermally stable. This work represents the first demonstration of Ru nanostructure-based peroxidase mimics and is therefore expected to inspire future research on bio-applications of Ru nanomaterials.

A highly dense and uniform layer of Au nanoparticles (NPs) on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film has been produced by the pulsed laser deposition (PLD) technique toward the production of an improved efficiency photovoltaic device. The advantage of PLD over other techniques is the easy and precise control of the Au NPs size and spatial distribution, without needing of further NP surface functionalization. The efficiency enhancement factor related to Au NPs doping has been evaluated in a solar cell based on poly-(3-hexylthiophene):[6,6]-phenyl-C-61-butyric acid methyl ester (P3HT:PCBM) diffused bilayer. The short-circuit current density, J (SC), increases by 18 % and the power conversion efficiency by 22 %, respectively, in comparison with an equivalent device without Au NPs. The optical and morphological properties of the Au NPs layer have been selected in order to evaluate the contribution of the surface plasmon resonance as enhancement factor of the solar cell efficiency, in a range size where light scattering is negligible.

This paper reports an investigation into the aging of pyrolyzed cobalt/polypyrrole (Co/PPy) oxygen reduction reaction (ORR) electrocatalysts, based on quasi-in-situ photoelectron microspectroscopy. The catalyst precursor was prepared by potentiostatic reverse-pulse coelectrodeposition from an acetonitrile solution on graphite. Accelerated aging was obtained by quasi-in-situ voltammetric cycling in an acidic electrolyte. Using photoelectron imaging and microspectroscopy of single Co/PPy grains at a resolution of 100 nm, we tracked the ORR-induced changes in the morphology and chemical state of the pristine material, consisting of uniformly distributed similar to 20 nm nanoparticles, initially consisting of a mixture of Co(II) and Co(III) oxidation states in almost equal amounts. The evolution of the Co 2p, O 1s, and N 1s spectra revealed that the main effects of aging are a gradual loss of the Co present at the surface and the reduction of Co(III) to Co(II), accompanied by the emergence and growth of a N 1s signal, corresponding to electrocatalytically active C-N sites.

Noble-metal nanoframes are of great interest to many applications due to their unique open structures. Among various noble metals, Ru has never been made into nanoframes. In this study, we report for the first time an effective method based on seeded growth and chemical etching for the facile synthesis of Ru nanoframes with high purity. The essence of this approach is to induce the preferential growth of Ru on the corners and edges of Pd truncated octahedra as the seeds by kinetic control. The resultant Pd-Ru-core frame octahedra could be easily converted to Ru octahedral nanoframes of similar to 2 nm in thickness by selectively removing the Pd cores through chemical etching. Most importantly, in this approach the face-centered cubic (fcc) crystal structure of Pd seeds was faithfully replicated by Ru that usually takes an hcp structure. The fcc Ru nanoframes showed higher catalytic activities toward the reduction of p-nitrophenol by NaBH4 and the dehydrogenation of ammonia borane compared with hcp Ru nanowires with roughly the same thickness.

In this paper we report on the growth and structural characterization of very thin (20 nm) Cr-doped ITO films, deposited at room temperature by double-target pulsed laser ablation on amorphous silica substrates. The role of Cr atoms in the ITO matrix is carefully investigated with increasing doping content by transmission electron microscopy (TEM). Selected-area electron diffraction, conventional bright field and dark field as well as high-resolution TEM analyses, and energy dispersive x-ray spectroscopy demonstrate that (i) crystallization features occur despite the low growth temperature and small thickness, (ii) no chromium or chromium oxide secondary phases are detectable, regardless of the film doping levels, (iii) the films crystallize as crystalline flakes forming large-angle grain boundaries; (iv) the observed flakes consist of crystalline planes with local bending of the crystal lattice. Thickness and compositional information about the films are obtained by Rutherford back-scattering spectrometry. Results are discussed by considering the combined effects of growth temperature, smaller ionic radius of the Cr cation compared with the trivalent In ion, doping level, film thickness, the double-target doping technique and peculiarities of the pulsed laser deposition method.

The objective of this paper is to study the morphology, structure, and composition, as well as the thermal-induced morphological, structural, and chemical changes of copper(Cu)/titanium nitride(TiN) bilayers versus Cu single layers, deposited on silicon substrates for microelectronic applications. These characterizations aimed to assess the reliability of Cu metallization for local interconnect and to investigate the barrier capability of TiN against Cu diffusion into the silicon (Si) substrate. Moreover, this paper provides a fundamental study of the temperature-induced interactions between Cu and Si, intermediated by the presence of a thin TiN layer. Cu thin films were sputtered onto Si substrates, with and without the interposition of thin TiN layers, and were successively annealed at temperature as high as 600. C. Different nitrogen flux percentages in the sputtering mixture (Ar + N-2) were used for the deposition of the barriers. X-ray diffraction (XRD) analyses were carried out in order to study the structural evolution of the layers, before and after the annealing. Scanning electron microscopy (SEM) observations gave information about the surface and cross section morphology, and spatially resolved energy dispersive X-ray Spectroscopy (EDS) profiles provided chemical information about the cross-sectional distribution of the atomic species and their possible interdiffusion. The barrier efficacy has been demonstrated by comparing the morphological and chemical modifications of the annealed Cu layers, with and without the presence of the TiN layer, and their effects on the electrical properties of the Cu films.

In this work, the evolution of the Au assisted-growth of ZnO nanorods deposited by vapour phase deposition both on sapphire and on indium-tin-oxide on glass (ITO-glass) substrates has been studied. Our investigation demonstrates that the growth proceeds first as a 3D growth, giving rise to a buffer layer, few microns thick, formed by ZnO grains with different orientation. Then a 1D transition occurs with the nucleation of a dense array of vertically aligned nanorods. A different degree of crystalline order and nanorods alignment was found between the samples grown on ITO-glass and sapphire substrates, which was ascribed to the different morphology that the Au seed layer acquires on the two different substrates. A semi-quantitative analysis of the ZnO crystalline orientation was carried out by X-ray diffraction (XRD) measurements performed at fixed incidence configuration and supported by high resolution scanning electron microscopy (HR-SEM) investigations on focused ion beam (FIB) prepared cross-sections.

In this work, we synthesized porous nanohydroxyapatite/collagen composite scaffold (nHA-COL), which resemble extracellular matrices in bone and cartilage tissues. Nano hydroxyapatite (nHA) was successfully nucleated in to the collagen matrix using hen eggshell as calcium biogenic source. Porosity was evaluated by apparent and theoretical density measurement. Porosity of all scaffolds was in the range of 95-98%. XRD and TEM analyses show the purity and size of nucleated HA around 10 nm and selected area electron diffraction (SAED) analysis reveals the polycrystalline nature of nucleated HA. SEM analysis reveals (i) all the scaffolds have interconnected pores with an average pore diameter of 130 micron and (ii) aggregates of hydroxyapatite were strongly embedded in the collagen matrix for both composite scaffolds compared with pure collagen scaffold. EDS analysis shows the Ca/P stoichiometric ratio around 1.67 and FTIR reveals the chemical interaction between the collagen molecule and HA particles. The testing of mechanical properties evidenced that incorporation of HA resulted in up to a two-fold increase in compressive modulus with high reinforcement level (similar to 7 kPa for 50HA-50COL) compared to pure collagen scaffold.