On the Synthesis and Chemical Vapour Deposition of Group 13 Precursors Towards Metal Oxide Thin Films

Various routes towards novel chlorogallium bis(alkoxides) and heteroleptic gallium alkoxides have been investigated. Compounds of the type, [GaCl(OR2)2] and [Ga(OR2)2(OR’)] (R = CH2CH2NMe2, CH2CH2NEt2, CH2CH2CH2NMe2; R’ = Me, Et, iPr, tBu), were synthesised using air sensitive methods and analysed by a variety of techniques. The chlorogallium bis(alkoxides) showed diastereotopic NMR splitting and in depth 1H NMR studies and DFT calculations were carried out on [GaCl(OCH2CH2CH2NMe2)2] to investigate the in situ ring conversion mechanism. Thermogravimetric analysis was employed to study the decomposition characteristics of the compounds, which were then used as single-source precursors towards gallium oxide thin films using aerosol-assisted chemical vapour deposition (AACVD). Amorphous, transparent films of Ga2O3 were deposited at 450 °C onto glass and quartz substrates. Subsequent annealing at 1000 °C gave crystalline films. Nitrogen-doped indium oxide films were deposited by AACVD via the in situ reaction of [In{NtBu(SiMe3)}3] and three equivalents of HOCH2CH2NMe2. The resultant films had a range of morphologies depending on solvent and temperature employed during the deposition. The cubic phase In2O3 films deposited had band gaps of ~2.9 eV suggesting nitrogen incorporation. These films were tested on steel and titanium substrates for their visible light water-splitting properties. Films were tested for their hydrogen production but limited activity as a photocatalyst was observed in the visible region. However, In2O3 nanoparticles produced using a solvothermal method and Ti- and Ta-doped In2O3 thin films grown via AACVD were tested for their gas sensing properties. Sensors were tested against reducing oxidising gases. The In2O3 nanoparticles showed the highest response to all gases, in particular ethanol. In2O3:Ta also showed a significant response to ethanol and smaller responses to other gases. Overall, novel precursors have been used as single-source precursors to main group oxide thin films, which were deposited via AACVD. Photocatalytic and gas sensing applications of these films have been explored

Structural and Dynamic Properties of Gallium Alkoxides

A comparison of chlorido-gallium functionalized alkoxides as precursors for aerosol-assisted chemical vapor deposition (AACVD) was carried out. Variable-temperature (VT)-NMR studies were used to probe the fluxional behavior of these alkoxides in solution, and hence their utility as precursors. The synthesis involved the initial isolation of the dimer [GaCl(NMe2)2]2 via a salt metathesis route from GaCl3 and 2 equiv of LiNMe2. This dimer was then reacted with 4 equiv of HOCH2CH2CH2NEt2, resulting in the formation of Ga[μ-(OCH2CH2CH2NEt2)2GaCl2]3 (1). Mass spectrometry and VT-NMR confirmed the oligomeric structure of 1. Tuning of the ligand properties, namely, the chain length and substituents on N, resulted in formation of the monomers [GaCl(OR)2] (R = CH2CH2NEt2, (2); CH2CH2CH2NMe2, (3)). VT-NMR studies, supported by density functional theory calculations, confirmed that the ligands in both 2 and 3 possess a hemilabile coordination to the gallium center, owing to either a shorter carbon backbone (2) or less steric hindrance (3). Both 2 and 3 were selected for use as precursors for AACVD: deposition at 450 °C gave thin films of amorphous Ga2O3, which were subsequently annealed at 1000 °C to afford crystalline Ga2O3 material. The films were fully characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-visible spectroscopy, and energy dispersive X-ray analysis

A Brief Etymology of the Collateral Circulation

It is well known that the protective capacity of the collateral circulation falls short in many individuals with ischemic disease of the heart, brain and lower extremities. In the past fifteen years, opportunities created by molecular and genetic tools, together with disappointing outcomes in many “angiogenic” trials, has led to a significant increase in the number of studies that focus on: 1) understanding the basic biology of the collateral circulation; 2) identifying the mechanisms that limit the collateral circulation’s capacity in many individuals; 3) devising methods to measure collateral extent, which has been found to vary widely among individuals; and 4) developing treatments to increase collateral blood flow in obstructive disease. Unfortunately, accompanying this increase in reports has been a proliferation of vague terms used to describe the disposition and behavior of this unique circulation, as well as the increasing miss-use of well-ensconced ones by new (and old) students of the collateral circulation. With this in mind, we provide a brief glossary of readily understandable terms to denote the formation, adaptive growth, and mal-adaptive rarefaction of the collateral circulation. We also propose terminology for several newly discovered processes that occur in the collateral circulation. Finally, we include terms used to describe vessels that are sometimes confused with collaterals, as well as terms describing processes active in the general arterial-venous circulation when ischemic conditions engage the collateral circulation. We hope this brief review will help unify the terminology used in collateral research

Nicotinic acid adenine dinucleotide phosphate (NAADP) regulates autophagy in cultured astrocytes.

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca(2+)-mobilizing messenger that in many cells releases Ca(2+) from the endolysosomal system. Recent studies have shown that NAADP-induced Ca(2+) mobilization is mediated by the two-pore channels (TPCs). Whether NAADP acts as a messenger in astrocytes is unclear, and downstream functional consequences have yet to be defined. Here, we show that intracellular delivery of NAADP evokes Ca(2+) signals from acidic organelles in rat astrocytes and that these signals are potentiated upon overexpression of TPCs. We also show that NAADP increases acidic vesicular organelle formation and levels of the autophagic markers, LC3II and beclin-1. NAADP-mediated increases in LC3II levels were reduced in cells expressing a dominant-negative TPC2 construct. Our data provide evidence that NAADP-evoked Ca(2+) signals mediated by TPCs regulate autophagy