Physicochemical characterizations of functional hybrid liposomal nanocarriers formed using photo-sensitive lipids.

With recent advances in the field of diagnostics and theranostics, liposomal technology has secured a fortified position as a potential nanocarrier. Specifically, radiation/photo-sensitive liposomes containing photo-polymerizable cross-linking lipids are intriguing as they can impart the vesicles with highly interesting properties such as response to stimulus and improved shell stability. In this work, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphoethanolamine (DTPE) is used as a photo-polymerizable lipid to form functional hybrid-liposomes as it can form intermolecular cross-linking through the diacetylenic groups. Hybrid-liposomes were formulated using mixtures of DTPE and saturated lipids of different chain lengths (dipalmitoylphosphatidylcholine (DPPC) and dimirystoilphosphatidylcholine (DMPC)) at different molar ratios. The physico-chemical characteristics of the liposomes has been studied before and after UV irradiation using a combination of techniques: DSC, QCM-D and solid-state NMR. The results signify the importance of a subtle modification in alkyl chain length on the phase behavior of the hybrid-liposomes and on the degree of crosslinking in the shell.

Controlled synthesis of ultrathin ZnO nanowires using micellar gold nanoparticles as catalyst templates.

We demonstrate a simple and effective approach to control the diameter of ultrathin ZnO nanowires with high aspect ratios and high densities over large areas. Diblock copolymer-based nanoparticle arrays exhibiting a high degree of hexagonal order and offering easy control of particle size (typically 1-10 nm) and interparticle spacing (25-150 nm) are utilized as nanocatalysts for the subsequent growth of semiconductor nanowires. The as-grown ZnO nanowires exhibit a single crystal hexagonal wurtzite structure and grow along the [0002] direction. Facetted catalyst particles were observed at the tip of the nanowires after synthesis, thus suggesting a catalyst-assisted vapor-solid-solid (VSS) rather than a vapor-liquid-solid (VLS) growth mechanism, the latter being frequently used in semiconductor nanowire production. Such a growth process allows us to easily prepare ultrathin ZnO nanowires with tunable diameters well below 10 nm by taking advantage of the inherent size control of the micellar method during deposition of the catalyst nanoparticles. Raman spectroscopy reveals a phonon confinement effect as the diameter of nanowires decreases. Photoluminescence spectra of these ultrathin nanowires indicate a blue shift of the free excitons and their phonon replicas by 37 meV induced by quantum confinement.

Metallization of organic surfaces: Pd on thiazole.

Results from electrochemical studies, in situ STM, and ex situ angle-resolved XPS on self-assembled monolayers (SAMs) of thiazole on Au(111) are reported for the first time. Although STM seems to indicate a low density of molecules organized in small ordered domains, a quantitative chemical analysis of the sample surface by XPS clearly points toward the formation of a densely packed molecular layer. The stability of the thiazole SAM against reductive desorption is found to be very comparable with that for thiol-SAMs on gold. This results from the formation of Au-S bonds between the molecules and their support as evidenced by XPS, thereby rebuting speculations that the ring nitrogen is responsible for the attachment of such molecules to gold surfaces. Consequently, the N-atoms terminating the molecular layer are available as active sites for the complexation with Pd ions thereby allowing the deposition of Pd islands with monatomic height on top of the thiazole SAM. The importance of such studies for metal-molecule interconnections is briefly addressed.