Delamination between thin-film metal and substrate is a major cause of failure in polyimide based neural microelectrode arrays. Chemical adhesion is the only way to establish a long-term bond that will allow two materials to stick to each other even in a wet environment, given that the materials do not deteriorate in the presence of water. This study assesses, by means of peel and shear tests, a long-term quantitative and comparative study of the adhesion of polyimide to various metallic and other inorganic layers of interest. Polyimide (BPDA-PPD) was cured on the layers, which involve platinum, gold and tungsten-titanium as commonly used implant metals and diamond-like carbon (DLC), silicon carbide (SiC), silicon dioxide (SiO2) and silicone nitride (SiN) as potential adhesion promoters to be used later as intermediate layers between metal and polyimide. The adhesion was observed over one year under accelerated-aging conditions by storing the specimens in 60°C saline (corresponding to 40000 hrs at 37°C). Only silicon carbide and amorphous carbon showed almost unaffected adhesion to polyimide over the testing period. No water intrusion at the interface was observed and the strong bond is almost fully maintained.

In this paper, a novel hyperspectral image acquisition system able to obtain a set of narrowband images (~2,25 nm of bandwidth) and the related composition of monochrome images in the near-infrared is described. The aim of this system is to discriminate the materials by their optical spectral response in the range of 900-1700 nm. This system has been developed in the framework of a collaborative project that includes the improvement of the automatic composition of reflectographic mosaics in order to study the underdrawing of large formats big artworks in real-time. The main features of this project are detailed in this paper. Furthermore, a few enlightening results of the hyperspectral system and new lines of research are shown.

Polymeric materials have been attracted the attention of researchers in various R&D applications. In this research, attempts were made to evaluate the changes in blood compatibility of polyethylene terephthalate (PET) by grafting acrylic acid (AAc) and immobilizing heparin by employing two-step plasma treatment. The PET surface was modified by using a novel method named “two-step plasma treatments” (TSPT). While first plasma is creating active sites for grafting, the second plasma polymerizing pre-adsorbed reactive monomer onto the surface of films. Finally, heparin immobilization was performed in the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide. All films were characterized by attenuated total reflection Fourier transformed infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM). The surface hydrophilicity of films was studied by water contact angle test and blood compatibility evaluated by Lactate dehydrogenase method (LDH Test). In vitro studies based on LDH results demonstrared that platelet adhesion onto the modified surfaces with heparin was drastically reduced in comparison with unmodified PET.

Using a Sutton and Chen interatomic potential, we study the molecular dynamics of Au-Pd nanoparticles with an initial icosahedral structure at different temperatures and concentrations, where each relative concentration of the 561-atom particles was made by placing atoms of the same species at equivalent sites, in order to identify under which conditions the melting transition temperature appears for each particle. In addition, we compute global order parameters in order to correlate the obtained results with the caloric curves of each particle. As a result, we observe that the melting transition temperature depends on the relative atomic positions of gold and palladium. The melting transition temperature of the Au-Pd alloy particles appears at higher temperature than that of the pure-gold particle. From the analysis of the structure of the particles, we found that the melting temperature increases with the proportion of gold atoms, and for those particles with a higher concentration of palladium on the surface, we observe an early migration of gold atoms before the melting transition temperature appears.

We report the results of photoluminescence measurements on ZnO bulk crystals implanted with both stable and radioactive species involving the group IV impurities Ge, Si and Sn. We previously confirmed the identity of a line emerging at 3.3225 eV as being related to Ge and present here uniaxial stress data which show that the defect responsible has trigonal symmetry. Experiments with Si provide circumstantial evidence of a connection with the well-known line at 3.333 eV. Our measurements indicate that for the case of Sn on the Zn site luminescence is not observed. We also confirm that the I9 and I2 lines are due to substitutional In impurities.

A novel nanoparticulated form of the poorly water-soluble anticancer drug paclitaxel (PTX) suitable for intravenous administration has been developed using sonication-assisted layer-by-layer (LbL) assembly. The nanoparticles contain up to 70 wt.% of the drug and consist of 150-180 nm solid crystal paclitaxel cores coated with 20-30 nm thick shells of alternative layers of PEGylated poly-L-lysine and heparin. Dispersions of PTX nanoparticles are stable in different biological solvents at concentrations up to 5 mg/ml. Intravenous administration of the LbL-coated nano-crystalline PTX to mice via tail injection provided the preliminary confirmation of their safety and tolerability.

The effect of time and voltage on the fabrication of self ordered nano porous aluminum oxide structure is studied. A two-step anodization process in 0.4M sulphuric acid and at low temperature was used to prepare structure with pore diameter between 20 to 29 nm. The surface morphology, including porous structure mainly, is characterized using scanning electron microscopy. Pore density 1010 to 1011 cm-2 is found. Thickness and electrical response are performed to these films. Capacitive sensor measurements for different water concentration are presented and discussed. The gas sensibility dependences with pore diameter and thickness layer are also reported.

By using electric-field-induced second-harmonic generation (EFISHG) measurement, we analyzed photovoltaic effect of two-layer solar cells (indium zinc oxide/pentacene/C60/Al). Results evidently showed that negative and excessive charges Qs accumulated at the two-layer interface under illumination, e.g., Qs =-1.7×10-9 C/cm2 at 0.05 mW/cm2 and –3.6×10-9 C/cm2 at 0.5 mW/cm2, while a short-circuit current flowed. The open-circuit voltage changed in accordance with accumulation charge Qs , and finally saturated. Modeling that accumulated negative charge is a source of space charge field and directly effects on the electrostatic energy stored in OSCs, dependence of the open voltage on the accumulated charge Qs was explained.

Reported is the photoluminescence enhancement due to surface plasmon from the metallic nanoparticles that are linked to the surface of a GaAs capped InAs quantum dots.In this study, spherical silver (Ag) nanoparticles are investigated where the different densities of Ag nanoparticles are deposited on four InAs/GaAs quantum dot samples. The PL enhancement due to Ag nanoparticles has been observed to be improved with increasing nanoparticle density. The photoluminescence enhancement is interpreted in terms of enhanced scattering from the surface plasmon excited in the Ag nanoparticles.

Ge quantum dots were grown on Si(100)-(2x1) using pulsed laser deposition while the laser is also exciting the substrate during film growth. The growth mode and morphology was probed by scanning tunneling microscopy (STM). Epitaxial growth at a substrate temperature of ∼250 °C was achieved by using laser excitation of the substrate. The morphology of the quantum dots changed with increased laser excitation energy density although the faceting of the individual quantum dots remained the same. A purely electronic mechanism of enhanced surface diffusion of the Ge adatoms is proposed.

Bacteriophytochromes (Bphs) are red-light photoreceptors found in photosynthetic and non-photosynthetic bacteria that have been engineered into infrared fluorescent protein markers. Bphs are composed of a photosensory module that is covalently linked to an effector/regulatory module, usually a histidine kinase (HK) domain. Light-induced, global structural changes are proposed to originate within the covalently attached biliverdin chromophore, a linear tetrapyrrole, and propagate through the protein. Bphs undergo reversible photoconversion between two distinct red and far-red light absorbing states, denoted Pr and Pfr respectively. For most Bphs, Pr is the dark-adapted state. The energy dissipated during Pr/Pfr photoconversion is proposed to directly impact the infrared fluorescence quantum yield. At this time, only structures of three different Bphs have been published, all of truncated proteins in their respective dark-adapted states. We have utilized scanning probe microscopy (SPM) to investigate the structure of intact Bphs in the light-adapted state in order to gain new insight into the mechanism of photoconversion and fluorescence. Scanning tunneling microscopy (STM) analysis of a pair of Bphs from photosynthetic bacterium R. palustris, RpBphP2 (P2) and RpBphP3 (P3) in their light-adapted states is presented in these proceedings. The concentration of the depositing protein has a key role in the molecular arrangements observed on the highly-ordered pyrolytic graphite (HOPG) surface. For example, at a high protein concentration, a hexagonal lattice of Bphs is observed by STM on a HOPG surface. Upon dilution, the photoreceptors self-organize into fiber-like structures on the surface. In these fibers, the dimer interface and the individual domains of the Bphs can be assigned and directly compared to a structural model of the intact, full-length proteins. In summary, SPM has potential to be an effective method for gaining new insight into Bph structure and dynamics.

Red mud is a solid waste residue from the caustic soda leaching of bauxite ores to produce alumina by the Bayer process. Red mud contains large quantity of alkali and aluminosilicate, so it is potentially available to prepare inorganic polymeric materials by geopolymerisation process. However, the activity or dissolubility of the aluminosilicate phases in red mud is significantly poor, which constraints the geopolymerisation process. Therefore, some pretreatment process for red mud is necessary to improve the adhesive property and dissolubility of Bayer red mud. In this study, mineral phase transformation and dissolubility of a typical red mud sample were studied under different thermal treatment processes. The thermal behavior of the red mud was studied by TG-DTA. The crystalline phases of the samples calcined at 200-1000 °C for different hours were determined by XRD, and the dissolubility was determined by alkaline leaching test. The TG-DTA pattern shows no obvious endothermic or exothermic peaks, and the weight loss increases continuously as the temperature rises, which indicates that the crystalline phases transform continuously as the temperature rises, consistent with the XRD results. As the calcination temperature rises from 200 to 800 °C, several kinds of crystalline phase in original red mud, including gibbsite, katoite, muscovite, natrodavyne disappeared in succession, accompanied with the formation of nepheline, gehlenite, sodium aluminum silicate, and some amorphous aluminosilicate. The calcined products are more likely to dissolve. But when it rises over than 800 °C, the content of gehlenite increases, and the phase of which is stable. As the calcination temperature rises from 200 to 1000 °C, the dissolubility of aluminosilicate in the red mud under high alkaline conditions increases firstly and then decreases after over 800 °C. Therefore, the optimum temperature of thermal treatment for red mud is about 800 °C. This study could contribute to the following preparation of geopolymeric material made from red mud, especially the pretreatment process of red mud.

A series of NiW catalysts supported on SBA-15-type materials modified with Al, Ti or Zr were prepared and tested in simultaneous hydrodesulfurization (HDS) of two model compounds: dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Catalysts were prepared by incipient wetness impregnation of SBA-type materials (pure silica SBA-15, Al-SBA-15, Ti-SBA-15 or Zr-SBA-15) using Keggin-type heteropolyacid H4SiW12O40 as active phase precursor and nickel nitrate. Nominal composition of the catalysts was 19 wt.% of WO3 and 3 wt.% of NiO. The supports and catalysts were characterized by SEM-EDX, N2physisorption, small-angle and powder XRD, UV-Vis DRS, TPR and HRTEM. It was shown that a good dispersion of Al, Ti and Zr species on the SBA-15 surface was reached. The characteristic structure of the SBA-15 support was preserved in all supports and NiW catalysts. Addition of metal atoms (Al, Ti, Zr) on the SBA-15 surface prior to catalysts’ preparation improved dispersion of Ni and W oxide species in calcined catalysts. HRTEM characterization of sulfided catalysts showed that the dispersion of NiW active phase was also better on metal-containing SBA-15 supports than on the pure silica one. All NiW catalysts supported on metal-containing SBA-15 materials showed an outstanding catalytic performance in HDS of both model compounds used (DBT and 4,6-DMDBT). A good correlation was found between the dispersion of sulfided NiW active phase and catalytic activity results. The highest HDS activity was obtained with the NiW catalyst supported on Zr-containing SBA-15 molecular sieve, which makes it a promising catalytic system for ultra-deep hydrodesulfurization of diesel fuel.

We studied the polarization-dependent photoluminescence (PL) of a-plane GaN /AlGaN multiple quantum wells (MQWs) grown on r-plane sapphire substrate with the various well width from 1.5 to 7.33 nm. To clarify the reasons of light emission polarization properties, we applied the 6×6 k‧p model to simulate the E-k dispersion relation and the wave functions to obtain the polarization optical transitions. According to the experimental result, the PL emission peak position exhibits a red-shifted with increasing well width, due to the reduction of the quantum confinement effect. The polarization ratio of a-plane GaN/AlGaN MQWs increased from 0.236 to 0.274 with increasing the quantum well width. This phenomenon is believed to be that y-polarized light emission gradually dominates the PL spectrum and thus enhances the polarization ratio.

We report formation of thin silicon oxide films on the silicon surfaces by combination of oxygen radical and high pressure H2O vapor heat treatment for passivation of silicon surfaces at a low temperature. Oxygen plasma was generated by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O2 and Ar at 2 sccm, 2x10-2 Pa and at a power of 50 W. Oxygen radical was produced from the plasma via a metal mesh closing plasma in the reactor. The top surfaces of 20 Wcm n-type silicon substrates with the rear surface coated by thermally grown SiO2 layers were exposed by oxygen radical from 1 to 5 min to oxidize the silicon surface. The samples were subsequently annealed with 9.0x105 Pa H2O vapor heat treatment at 260oC for 3 h. The effective minority carrier lifetime estimated using photo-induced carrier microwave absorption system in the case of 635 nm light illumination at 1.5 mW/cm2 to the top surface increased from 1.3x10-4 to 5.1x10-4s as the oxygen radical treatment duration increased from 1 to 5 min. The recombination velocity decreased from 380 to 90 cm/s. 500 kHz capacitance response with bias gate voltages characteristics of metal oxide semiconductor structure resulted in the effective oxide thicknesses (EOT) ranging from 1.3 to 1.7 nm. These results indicate a capability of thin oxide formation and effective passivation of silicon surfaces at a low temperature.

Hydrogenated amorphous silicon-germanium alloy thin films (a-Si1-xGex:H) were deposited using reactive magnetron sputtering. Dual targets of silicon and germanium were sputtered in an argon + hydrogen atmosphere using rf excitation. Films with x = 0.4 were deposited as a function of substrate temperature and hydrogen partial pressure, and were evaluated by dark and photoconductivity, infrared absorption, and optical transmission. Photosensitivity reached a maximum value of about 5000 between 150 and 200 °C. Using the stretching modes in the region of 2000 cm-1, the hydrogen bonding was characterized in terms of the preferential attachment ratio (PA), which represents the ratio of H bonded to silicon to that bonded to germanium. The PA shows a systematic increase with increasing temperature, independent of hydrogen partial pressure. The interplay between thermodynamic and kinetics effects in determining PA and film quality will be discussed.

The synthesis of semi-interpenetrating networks (SIPN) based on linear poly(ethyl 2-cyanoacrylate) (PECA) and oligo(ethylene glycol) diglycidyl ether (OEGDG) based polymer networks was motivated by the hypothesis that the brittleness of polycyanoacrylates may be overcome by incorporating them into a polymer network architecture. A sequential synthetic route was applied, in which first PECA was prepared by anionic polymerization. Subsequently, OEGDG was crosslinked with different anhydrides and curing catalysts to form networks with hydrolyzable ester bonds and interpenetrating PECA. These SIPNs showed a low water uptake compared to other polyether based networks. Some of the obtained materials were transparent and exhibited a great flexibility, which was maintained also after 24 h of immersion in water and subsequent drying. Such networks could be components of future stimuli-sensitive material systems.

Heterostructured Ba0.8Sr0.2TiO3/ZrO2/Ba0.8Sr0.2TiO3 thin films are fabricated on the platinized Si substrates by a sol-gel process. The current versus voltage measurements are taken on these films by varying the thickness of ZrO2 layer. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in leakage current which is very essential for the low dissipation energy and hence faster operation of memory devices. It is observed that the leakage current further decreases as the ZrO2layer thickness increases. Also it is seen that different conduction mechanisms are contributing to the leakage current in the different field regions. Poole-Frenkel (PF), space charge limited current (SCLC), and Ohmic mechanisms are the dominating conduction processes in high, medium, and low field regions respectively. An energy band diagram is given to explain the Ohmic conduction in the low field region and the Poole-Frenkel conduction mechanism in the high field region for these devices.

Density functional theory and molecular dynamics were used to study the generation of hydrogen peroxide around a nickel atom anchored on a pyridine-like nitrogen-doped graphene (PNG) layer. First, we found that two hydrogen molecules are adsorbed around the nickel atom, with adsorption energy 0.95 eV/molecule. Then we studied the interaction of oxygen molecules with this system at atmospheric pressure and 300 K. It is found that two hydrogen peroxide molecules are formed. However, at 700 K, one hydrogen peroxide molecule, and one water molecule are desorbed. One oxygen atom stays bound to the nickel atom.

Simultaneous wide- and small- angle X-ray scattering (WAXS-SAXS) has revealed a stress-induced bimodal orientation of POSS crystals and PCL chains, both in a constrained POSS/PCL crosslinked network architecture with shape memory properties. POSS/PCL nanocomposites with molecular weight of 2,600 g/mol exhibiting shape memory behavior were synthesized and variation of crosslinker molar ratio was used to obtain POSS/PCL networks with different crosslink density (Alvarado-Tenorio et al., Macromolecules, 44, 5682, 2011). In that study it was shown that there are POSS crystals embedded in an amorphous PCL matrix, and the POSS crystals were ordered in a cubic nanostructure. In this work, it will be shown that elongation at room temperature of all the networks yielded a double-induced orientation (90º and 180º) of the POSS crystals, as indicated by the 101 reflection. Moreover, it was also detected stretched-induced crystallization of the otherwise amorphous PCL chains. Furthermore, SAXS data showed long periods in the meridional and equatorial orientations of 630 Å, 90 Å and 45 Å corresponding to a lamellar nanostructure of PCL chains. The induced bimodal orientation of the POSS-PCL molecular network will be correlated with its shape memory properties.