Luminescent lanthanide doped SiO2/Hydroxylapatite (HAp) core/shell nanoparticles (NPs) were synthesized by sol-gel technology. The resulting NPs exhibited an amorphous SiO2 core and a crystalline luminescent shell. The formation of the HAp layer was possible at pH 8.5. The characterization of the resulting NPs was done by transmission electron microscopy, X-ray diffraction analysis, inductively-coupled plasma combined with optical emission spectrometry, and photoluminescence spectroscopy. Additionally, the newly developed SiO2/HAp:Ln3+ core/shell NPs were tested for their biocompatibility, e. g. by an in vitro cell culture based assay.

The effect of energetic oxygen bombardment of the TiO2 rutile {110} surface is studied by means of molecular dynamics simulations using a variable charge potential. A random selection of O atoms and O2 molecules are incident successively and normally onto the surface. At an energy of 5 eV the surface becomes saturated with oxygen until covered with between 1 and 2 monolayers of adatoms. As the fluence further increases Ti atoms are pulled out from the bulk and become surrounded by the O atoms forming well-defined atomic clusters on the surface which then desorb. At bombardment energies of 400 eV, the O atoms penetrate into the bulk and voids form whose surfaces are decorated with oxygen atoms. As the O fluence further increases the surface is sputtered and the voids then intersect the surface forming a very rough topography.

Ternary thallium chalcogenides of the formula Tl4 MQ 4, where M = Zr and Hf and Q = S, Se, and Te were synthesized and characterized. Our X-ray diffraction studies on suitable single crystals reveal that the sulphides and selenides are isostructural, with monoclinic space group P, whereas the corresponding tellurides crystallize in the rhombohedral crystal system (R). The structures of the sulphides and selenides are comprised of zigzag chains of edge-sharing MQ 6 octahedra, whereas the MTe6 octahedra are interconnected via common faces to form linear trimeric units. In all cases, the atoms adopt common oxidation states, namely Tl+, M 4+, and Q 2–. The electronic structure calculations using the linear muffin tin orbital (LMTO) method predicted band gaps of 1.7 eV, 1.3 eV and 0.3 eV for the sulphides, selenides and tellurides, respectively, implying sulphides and selenides are large band gap materials, and the tellurides narrow gap semiconductors. Their electronic transport properties are also evaluated with respect to the thermoelectric energy conversion.

Our work focuses on the earliest events of homo-/heterogeneous nucleationfrom an initial supersaturated solution to the subsequent growth of nuclei.The combined use of conductance, together with hydrogen and calcium ISEs hasprovided new insights into the mechanisms of crystal nucleation and phasestability. We propose that two types of ACP are formed during HAPnucleation. The initial subcritical calcium-phosphate ion clusters form anamorphous [CaHPO4·xH2O] phase (ACP-1), whichtransforms to amorphous [Ca3(PO4)2](ACP-2), and subsequently to HAP. This study is a major step forward in ourunderstanding of the earliest nucleation events in vitro and in vivo.Additives may influence HAP nucleation by interacting with ACP clustersduring the early induction period.

A series of Ca1-xSrxS:Eu2+ y mol% phosphors were synthesized with solid state reactions and with various Ca/Sr ratio and Eu2+ doping concentrations. The influences of the lattice composition and the Eu2+ doping level on photoluminescent properties were analyzed. With doping concentrations between 0.1 to 3 mol%, concentration quenching takes place leading to the decrease of luminance; the emission maxima are also red-shifted. Further, this work reports enhanced photosynthetic activities of intact spinach leaves due to spectral modification of simulated solar irradiation by one synthesized phosphor (Ca0.4Sr0.6S:Eu1 mol%). The CO2 assimilation rates of intact spinach leaves were monitored with an effective homemade photosynthesis measurement system with controlled light conditions. The phosphor could efficiently convert the photosynthetically less active green part of the solar spectrum into the red, with a broad-band red emission centered at 650 nm and a halfband-width of 68 nm, giving an excellent match with the absorption spectrum of spinach chloroplasts. By careful referencing the photon flux, we found an enhanced photosynthetic activities by about 30 % due to the emission of the phosphor.

Laser interference patterning-induced microstructural modifications have been investigated in two noble metal-incorporated oxide thin film systems: Pd0.25Pt0.75Ox and gold-incorporated yttria-stabilized zirconia - Au-YSZ. Transmission electron microscopy was used to investigate the influence of the laser treatment on the microstructure of the samples. In the case of Pd0.25Pt0.75Ox, the formation of a nanocomposite arrangement resulted from the precipitation of metal nanograins in the oxide matrix triggered by laser irradiation. In Au-YSZ, the starting microstructure consisted of gold nanograins embedded in a YSZ matrix. A noticeable growth and coalescence of gold nanograins occurred near the surface in the region of maximum interference. Simultaneously, a foamy morphology, mostly consisting of gold crystals, was formed at the film surface. In contrast to thermal annealing, the laser treatment proposed here is a fast procedure to partially relocate gold at the film surface and provide a local solid lubrication.

A detailed analysis of photovoltaic front surface phosphor-based spectral modification and light scattering by hetero-structure was conducted. Phosphor based spectral downconversion is a well known laser technology. The analysis assumes that both sunlight energy and photovoltaic performance are at peak sunlight photon flux within the spectral range. Further, the analysis presented here indicates that parasitic losses and light scattering within the spectral range are large enough to offset any expected gains. For example, analysis of up-conversion phosphor-based approaches indicates that these are likely to suffer unexpectedly large losses in the peak spectral region due to parasitic absorption when attempting to down convert UV light.

Thermoelectric generators are actively being pursued to recover waste heat from the auto exhaust gas to improve vehicle fuel economy. Efficiency of a thermoelectric generator is defined as the ratio of electrical power output to the heat input. In a typical thermoelectric generator, a heat exchanger captures the heat from the medium (ex: hot exhaust gas heat) and this heat needs to be transferred to the hot end of the thermoelectric elements with minimum losses. It is important to understand and minimize these thermal losses to improve the efficiency of a thermoelectric generator. Accurate measurement of the thermal interface resistance parameters is also important because they are used in a comprehensive thermoelectric system model to predict the performance of the generator under actual use conditions. To understand the factors influencing the thermal interface resistance, and to determine the effective thermal interface resistance between the heat exchanger and the thermoelectric hot shunts in a prototype generator that is currently being developed for auto exhaust heat recovery application, we have designed and built a test setup to characterize the thermal interface resistance under high heat flux conditions. Measured temperature profiles in the test sample, heat input into the test device and its geometry are fed into a thermal model to extract the thermal conductance parameters. Factors affecting the thermal interface resistance and the influence of different interface materials were evaluated. Suitable solutions with minimum thermal loss were selected for building the prototype thermoelectric generator for waste heat recovery application and validating the system model.

In this work, we report investigations on plasmonic nano-disks using cathodoluminescence (CL) imaging and spectroscopy. 50 nm thick gold disks fabricated using electron beam lithography were studied and several modes were identified. Detailed analysis of the modes using monochromatic imaging and CL spectra showed strong size dependence. Our investigations on these plasmonic nano-disks allow understanding of light-matter interaction at nanoscale, with several potential applications including next generation plasmonic nano-lasers.

We synthesized ZnS nanocrystals from identical raw material solution by the thermal decomposition of an amine complex. The shapes of products were changed by simply varying heating rate. At higher heating rate, we obtained the isotropic zincblende nanocrystals. At the lower heating rate, the nanorods were formed and the length was increased with the decrease of heating rate. The nanorods had wurtzite structure below 175 °C, and consequently transformed to zincblende phase during a temperature rise to 200 °C. These particle shapes and phases were related to the adsorption properties of amine ligands. Additionally, the synthesized ZnS nanodots and nanorods exhibited predominantly band-edge emission in fluorescence spectra.

ZnO nanostructures have attracted a great deal of interest because of their biocompatibility and outstanding optical and piezoelectric properties. Their uses are widely varying, including as the active element in sensors, solar cells, and nanogenerators. One of the major complications in device development is how to grow ZnO nanowires in well aligned and patterned films with predefined geometrical shape and aspect ratio. Controlled growth is required to achieve the optimal density of nanowires and to produce a defined geometric structure for incorporation in the device. In this work, we have presented a method by which vertically aligned ZnO nanowires could be grown in defined patterns on surfaces without the use of resists. We used a hydrothermal method to grow ZnO nanowires on a substrate through growth modifiers that was pre-patterned with a seeding solution by means of microcontact printing. This method produced vertically aligned ZnO nanowires of predefined size and shape with pattern resolution high enough for the production of rows of single nanowires. The nanowires were characterized by using scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) techniques.

We have investigated the interfacial contact properties of the CMOS compatible electrode materials W, TiW, Ta, TaN and TiN to doped-Sb2Te phase change material (PCM). This interface is characterized both in the amorphous and in the crystalline state of the doped-Sb2Te. The electrical nature of the interface is characterized by contact resistance measurements and is expressed in terms of specific interfacial contact resistance (ρC). These measurements are performed on four-terminal Kelvin Resistor test structures. Knowledge of the ρC is useful for selection of the electrode in the integration and optimization of the phase change memory cells.

Single Walled Carbon Nanotubes (SWNTs) dispersions are obtained after ultrasonication in Cellulose Nanocrystals (CNs) colloidal suspensions and they are found to be stable during several months. Similarly to CNs suspensions, SWNTs/CNs dispersions are used to elaborate multilayered thin films by the layer by layer method. Characterizations of the growth pattern, Raman and optical properties of the films are investigated. The presence of isolated SWNTs in each bi-layer is attested by characteristic Raman and luminescence signals. These films may be interesting for sensing applications.

We report on the influence of radio-frequency magnetron sputtering variables (working pressure and deposition atmosphere) and post-deposition thermal treatment processing upon the structural, optical and electrical properties of c-axis highly textured ZnO thin films. The films’ crystallinity increased progressively with argon pressure for the inert atmosphere experiments and with the oxygen dilution in the working atmosphere (up to 10%) for the reactive atmosphere experiments. The post-deposition annealing treatment at 450°C/1h in air reduced the strain in the ZnO films and enhanced their crystallinity and texturing. The ZnO films had an average transmittance of ∼90% in visible range and an average band-gap of ∼3.4 eV, regardless of the sputtering variables used. The samples prepared at the higher argon pressure (0.45 Pa) had a resistivity with one order of magnitude smaller than the samples prepared at the lower pressures.

Cationic rosette nanotubes (RNTs) were generated by functionalization of selfcomplementary twin guanine-cytosine (G^C) motifs with up to 15 L-lysine residues (Kn.T, n = 1–15). siRNA binding capacity was determined by gel retardation assay on agarose gel. Up to K5.T, siRNA complexation was a function of oligolysine-chain length and mole ratio of Kn.T. At higher Kn.T, local cationic density employed by supramolecular assembly emerged as a contributor to siRNA complexation. We have shown that no effective siRNA binding was achieved with equivalent mole ratios of corresponding oligolysine peptides (not conjugated to the G∧C motif). With K12.T, siRNA complexation gave spherical structures in the range of 200 nm, which was internalized and retained by human cell lines without noticeable cytotoxicity. In this report, we demonstrate for the first time the capacity of the RNTs as siRNA carriers that can be tailored to achieve maximum siRNA loading efficiency without carrier-associated cell toxicity. We anticipate these cationic RNTs to be effective in the delivery of biologicallyfunctional siRNA.

We studied the effect of RTP and furnace annealing on the transport properties and electroluminescence of Si-nc embedded in SiO2 layers, and of Er ions coupled to Si-nc. The light emitting devices have been fabricated in a CMOS line by implantation of Si and Er in SiO2. The results show that for the same annealing temperature, furnace annealing decreases electrical conductivity and increases probability of impact excitation, which leads to an improved external quantum efficiency. Correlations between phenomenological transport models, annealing regimes, and erbium electroluminescence are observed and discussed.

Acrylic based films containing thermo-chemically synthesized magnetite nanoparticles (NPs) were prepared by UV-curing. A stable dispersion of Fe3O4 NPs in n-hexane was added to polyethylene glycol diacrylate (PEGDA) oligomer or to hexanediol diacrylate (HDDA) oligomer, producing a blend whose viscosity matches the processing requirements for inkjet printing technology. Morphologic characterization is provided by means of Field Effect SEM on a representative nanocomposite section.

By real-time FT-IR analysis it was shown that Fe3O4 NPs are able to initiate radical chain-grown polymerization under UV light, for what concerns the HDDA matrix. Tight cross-linked transparent polymeric films were obtained after 1 minute of UV irradiation.

The magnetic properties of the produced films were studied by means of an Alternating-Gradient Force Magnetometer (AGFM) in the temperature range 10 – 300 K and up to 18 kOe. The isothermal magnetization curves of both HDDA and PEGDA -based nanocomposites showed that these hybrid systems must be described as interacting superparamagnets (ISP) characterized by inter-particle magnetic interactions dominating over intra-particle effects.

SU-8 is being increasingly used as a compliant structural material for MEMS applications due to its interesting properties such as lower Young’s modulus and higher mechanical and thermal stability. One of the popular classes of MEMS devices is a piezoresitive microcantilever. Ultra-sensitive polymer composite cantilevers made up of SU-8 as a structural layer and 10% carbon Black in SU8 as a piezoresistive layer with lower Young’s modulus and higher gauge factor have been reported recently by our group. Higher electrical conductivity at lower concentration of conductive filler is of increased interest. Here we report a novel composite with purified multiwall carbon nanotubes (MWNT) in SU8 as a piezoresistor. MWNT were modified with octadecyl triphenyl phosphonium bromide (OTPB) in order to achieve debundled MWNT. A microcantilever device with integrated MWNT/SU-8 composite has been fabricated and characterized.

We have focused to grow cubic GaN (c-GaN) on Si(100) substrates using boronmonophosphide (BP) buffer crystals. The growth of GaN was carried out by MOVPE on BP/Si(100) substrate of 2 inches in diameter. By the several evaluations, it was recognized that when the growth temperature is around 750˚C, c-GaN was dominant. The typical growth rate was about 0.5μm/h. We obtained c-GaN layer over 2.5μm thick without cracking.

Silver jewelry and repoussé work have been a significant part of the material culture of Tibet for centuries. While objects such as offering bowls, skullcups, butter lamps, ewers, portable shrines and incense burners serve religious purposes, many other type of objects are important in the secular life of Tibetans. This secular silver material culture includes items such as necklaces, bracelets, rings, hair ornaments, amulet cases, vessels, belts or waistbands and hooks for milk pails or butter churners.

The discussion presented here focuses on secular silver objects made in the workshop of a traditional Tibetan silversmith in the town of Songpan in northwestern Sichuan Province, China (traditionally comprising part of eastern Tibet). With interruptions in traditional practices during the Cultural Revolution, the question has been raised about whether or not such practices have continued [1]. This research is part of an effort to document traditional Tibetan craft practices and identify threats to their preservation. Workshop processes start with the craftsman acquiring the silver, making or buying tools, arranging the work area, and the customer commissioning a piece. Technical processes include working the silver ingot to form an object, annealing and quenching, making silver wire, filigree, granulation, soldering, inlay work, pickling and finishing.

Some changes have been introduced in how the workshop operates during the lifetime of the current craftsman, leading to differences between his procedures and that of his father, under whom he apprenticed. Some of these changes are due to technological advances (new equipment becoming available) and some are due to larger societal changes (for example, new government regulations regarding purchasing of raw silver). These changes are often in technological style affecting the fabrication stages, but not necessarily visible in completed objects, which retain their traditional forms, visual style and functions.