Pharmaceutical and food surfaces of relevant composite materials and the characterization thereof

The main motivation is to understand surface-interface of materials in order to manipulate the systems and then get involved in technology. Particulate and composite materials, used in Pharmaceutical and Food, are subjected to structural modifications during the chain of steps of production and manufacturing processes. The processing objective is often to induce a macroscopic change in order to setup the material for the next processing step. One critical aspect is that the various unit operations meant to adjust the macroscopic properties that invariably induce structural changes at the microscopic scale on the materials. Being unintended, such microscopic changes are also uncontrolled and are the source of the often unpredictable and poorly understood bulk behavior of many particulate materials. It is therefore of critical relevance to develop a fundamental insight at the microscopic structure of such materials, by probing and mapping them at the nanoscale level. This study probes the interface and surfaces of stress-free and stress-induced materials with characterization thereof. Submicron particles are always produced during pharmaceutical and food processing in an uncontrolled and poorly understood manner. The high surface to volume ratio often makes them dominant on the bulk behavior of the in-process materials used for manufacturing. The structural properties controlling in-process response are size dependent, falling over the length scales ranging from nanometers to a few micrometers. In this domain, structural surface mapping is critical to the dispersion and agglomeration control to understand and enable bulk functionality of powders. Working with films has been demonstrated to be an effective way of immobilizing nanoparticulate systems in a dry and uniform manner. The use of polymer–particle composite films results in better reproducibility of in-process systems than the single component counterpart. Therefore, nanoscale mapping of surfaces of such composites results in a more systematic way of characterizing the critical processing attributes of food and pharmaceutical materials that will lead to a higher performance and acceptable shelf-life stability

The catalytic reduction of NO by H-2 on Ru(0001): Observation of NHads species

Adsorption of NO and the reaction between NO and H-2 were investigated on the Ru(0001) surface by X-ray photoelectron spectroscopy (XPS). Surface composition was measured after NO adsorption and after the selective catalytic reduction of nitric oxide with hydrogen in steady-state conditions at 320 K and 390 K in a 30:1 mixture of H-2 and NO (total pressure = 10(-4) mbar). After steady-state NO reduction, molecularly adsorbed NO in both the linear on-top and threefold coordinations, NHads and N-ads species were identified by XPS. The coverage of the NHads and N-ads species was higher after the reaction at 390 K than the corresponding values at 320 K Strong destabilisation of N-ads by O-ads was detected. A possible reaction mechanism is discussed. (c) 2005 Elsevier B.V. All rights reserved

Large-scale Graphitic Thin Films Synthesized on Ni and Transferred to Insulators: Structural and Electronic Properties

We present a comprehensive study of the structural and electronic properties of ultrathin films containing graphene layers synthesized by chemical vapor deposition (CVD) based surface segregation on polycrystalline Ni foils then transferred onto insulating SiO2/Si substrates. Films of size up to several mm's have been synthesized. Structural characterizations by atomic force microscopy (AFM), scanning tunneling microscopy (STM), cross-sectional transmission electron microscopy (XTEM) and Raman spectroscopy confirm that such large scale graphitic thin films (GTF) contain both thick graphite regions and thin regions of few layer graphene. The films also contain many wrinkles, with sharply-bent tips and dislocations revealed by XTEM, yielding insights on the growth and buckling processes of the GTF. Measurements on mm-scale back-gated transistor devices fabricated from the transferred GTF show ambipolar field effect with resistance modulation ~50% and carrier mobilities reaching ~2000 cm^2/Vs. We also demonstrate quantum transport of carriers with phase coherence length over 0.2 $\mu$m from the observation of 2D weak localization in low temperature magneto-transport measurements. Our results show that despite the non-uniformity and surface roughness, such large-scale, flexible thin films can have electronic properties promising for device applications.Comment: This version (as published) contains additional data, such as cross sectional TEM image

Spectroscopic properties of colloidal indium phosphide quantum wires

Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence efficiencies through photochemical etching in the presence of HF result only in photochemical thinning or photo-oxidation, without a significant influence on quantum-wire photoluminescence. However, photo-oxidation produces residual dot and rod domains within the wires, which are luminescent. The results establish that the quantum-wire band gaps are weakly influenced by the nature of the surface passivation, and that colloidal quantum wires have intrinsically low photoluminescence efficiencies

Probing the State of Water on the Surface of Pharmaceutical Salts by X-ray Photoelectron Spectroscopy

•The results with both trifluoperazine di-HCl and clonidine HCl provide strong evidence for dissociative adsorption of water on organic hydrochloride salts. •This strongly bound water may act as nuclei for further moisture uptake and cause stability problems for moisture-labile salts. •Future work will investigate: • Role of surface chemistry and defect density of various faces of clonidine HCl single crystals on the extent of dissociation • Comparison between clonidine HCl, clonidine HBr and clonidine free bas

Controllable Surface Expression of Bioactive Peptides Incorporated into a Silica Thin Film Matrix

Mammalian cell culture platforms often require biomolecular modification to enhance cell adhesion and proliferation, Often, these modifications are performed using self-assembled monolayers or whole protein coatings, Such its collagen. These protocols are inherently useful but generally suffer from repeatability. Undesirable conditions during self-assembly can lead to complications in the surface presentation of the biological ligands. Whole proteins are often unstable and derived from animal sources, making them less attractive for tissue engineering applications. As the biological effect of the material often depends strongly on the concentration of the integrated ligand(s), any complication due to synthesis or stability can lead to unexpected biological results. In this research, we expand upon previous work in peptide-silane modifications to sol-gel derived silica matrixes, demonstrating that the surface density of the peptide can be calibrated by simply modifying the starting liquid precursor concentration. The potential for calibration of peptide surface presentation allows for well-defined cell culture platforms that have the potential to mimic natural proteins in a stable, repeatable manner