KrF pulsed laser deposition of chromium oxide thin films from Cr8O21 targets

Chromium oxides, CrxOy, are of great interest due to the wide variety of their technological applications. Among them, CrO2 has been extensively investigated in recent years because it is an attractive compound for use in spintronic heterostructures. However, its synthesis at low temperatures has been a difficult task due to the metastable nature of this oxide. This is indeed essential to ensure interface quality and the ability to coat thermal-sensitive materials such as those envisaged in spintronic devices. Pulsed Laser Deposition (PLD) is a technique that has the potential to meet the requirements stated above. In this work, we describe our efforts to grow chromium oxide thin films by PLD from Cr8O21 targets, using a KrF excimer laser. The as-deposited films were investigated by X-ray diffraction and Rutherford backscattering spectrometry. Structural and chemical composition studies showed that the films consist of a mixture of amorphous chromium oxides exhibiting different stoichiometries depending on the processing parameters, where nanocrystals of mainly Cr2O3 are dispersed. The analyses do not exclude the possibility of co-deposition of Cr2O3 and a low fraction of CrO2.

KrP laser CVD of chromium oxide by photodissociation of Cr(CO)(6)

This work reports on the synthesis of chromium oxide thin films prepared by photodissociation of Cr(CO)(6) in an oxidizing atmosphere, using a pulsed UV laser (KrF, lambda = 248 nm). The experimental conditions, which should enable the synthesis of CrO2, are discussed and results on the deposition of CrxOy films on Al2O3 (0001) substrates are presented.

Structural and optical studies of Au doped titanium oxide films

Thin films of TiO2 were doped with Au by ion implantation and in situ during the deposition. The films were grown by reactive magnetron sputtering and deposited in silicon and glass substrates at a temperature around 150 degrees C. The undoped films were implanted with Au fiuences in the range of 5 x 10(15) Au/cm(2)-1 x 10(17) Au/cm(2) with a energy of 150 keV. At a fluence of 5 x 10(16) Au/cm(2) the formation of Au nanoclusters in the films is observed during the implantation at room temperature. The clustering process starts to occur during the implantation where XRD estimates the presence of 3-5 nm precipitates. After annealing in a reducing atmosphere, the small precipitates coalesce into larger ones following an Ostwald ripening mechanism. In situ XRD studies reveal that Au atoms start to coalesce at 350 degrees C, reaching the precipitates dimensions larger than 40 nm at 600 degrees C. Annealing above 700 degrees C promotes drastic changes in the Au profile of in situ doped films with the formation of two Au rich regions at the interface and surface respectively. The optical properties reveal the presence of a broad band centered at 550 nm related to the plasmon resonance of gold particles visible in AFM maps. (C) 2011 Elsevier B.V. All rights reserved.

Cellular hypomethylation is associated with impaired nitric oxide production by cultured human endothelial cells

Hyperhomocysteinemia (HHcy) is a risk factor for vascular disease, but the underlying mechanisms remain incompletely defined. Reduced bioavailability of nitric oxide (NO) is a principal manifestation of underlying endothelial dysfunction, which is an initial event in vascular disease. Inhibition of cellular methylation reactions by S-adenosylhomocysteine (AdoHcy), which accumulates during HHcy, has been suggested to contribute to vascular dysfunction. However, thus far, the effect of intracellular AdoHcy accumulation on NO bioavailability has not yet been fully substantiated by experimental evidence. The present study was carried out to evaluate whether disturbances in cellular methylation status affect NO production by cultured human endothelial cells. Here, we show that a hypomethylating environment, induced by the accumulation of AdoHcy, impairs NO production. Consistent with this finding, we observed decreased eNOS expression and activity, but, by contrast, enhanced NOS3 transcription. Taken together, our data support the existence of regulatory post-transcriptional mechanisms modulated by cellular methylation potential leading to impaired NO production by cultured human endothelial cells. As such, our conclusions may have implications for the HHcy-mediated reductions in NO bioavailability and endothelial dysfunction.

Risk of colorectal cancer associated with the C677T polymorphism in 5,10-methylenetetrahydrofolate reductase in Portuguese patients depends on the intake of methyl-donor nutrients

Background: Polymorphisms located in genes involved in the metabolism of folate and some methyl-related nutrients are implicated in colorectal cancer (CRC). Objective: We evaluated the association of 3 genetic polymorphisms [C677T MTHFR (methylene tetrahydrofolate reductase), A2756G MTR (methionine synthase), and C1420T SHMT (serine hydroxymethyltransferase)] with the intake of methyl-donor nutrients in CRC risk. Design: Patients withCRC(n 196) and healthy controls (n 200) matched for age and sex were evaluated for intake of methyl-donor nutrients and the 3 polymorphisms. Results: Except for folate intake, which was significantly lower in patients (P 0.02), no differences were observed in the dietary intake of other methyl-donor nutrients between groups. High intake of folate ( 406.7 g/d) was associated with a significantly lower risk of CRC (odds ratio: 0.67; 95% CI: 0.45, 0.99). The A2756G MTR polymorphism was not associated with the risk of developing CRC. In contrast, homozygosity for the C677TMTHFRvariant (TT) presented a 3.0-fold increased risk of CRC (95% CI: 1.3, 6.7). Similarly, homozygosity for the C1420T SHMT polymorphism also had a 2.6-fold increased risk (95% CI: 1.1, 5.9) of developing CRC. When interactions between variables were studied, low intake of all methyl-donor nutrients was associated with an increased risk ofCRC in homozygous participants for the C677T MTHFR polymorphism, but a statistically significant interaction was only observed for folate (odds ratio: 14.0; 95% CI: 1.8, 108.5). No significant associations were seen for MTR or SHMT polymorphisms. Conclusion: These results show an association between the C677T MTHFR variant and different folate intakes on risk of CRC.

Study of Annealed Indium Tin Oxide-Films prepared by RF Reactive Magnetron Sputtering

Tin doped indium oxide (ITO) films were deposited on glass substrates by rf reactive magnetron sputtering using a metallic alloy target (In-Sn, 90-10). The post-deposition annealing has been done for ITO films in air and the effect of annealing temperature on the electrical, optical and structural properties of ITO films was studied. It has been found that the increase of the annealing temperature will improve the film electrical properties. The resistivity of as deposited film is about 1.3 x 10(-1) Omega*cm and decreases down to 6.9 x 10(-3) Omega*cm as the annealing temperature is increased up to 500 degrees C. In addition, the annealing will also increase the film surface roughness which can improve the efficiency of amorphous silicon solar cells by increasing the amount of light trapping.

Fabrication of electrochemically reduced graphene oxide/cobalt oxide composite for charge storage electrodes

Electrochemically-reduced graphene oxide (Er-GO) and cobalt oxides (CoOx) were co-electrodeposited by cyclic voltammetry, from an electrolyte containing graphene oxide and cobalt nitrate, directly onto a stainless steel substrate to produce composite electrodes presenting high charge storage capacity. The electrochemical response of the composite films was optimized by studying the parameters applied during the electrodeposition process, namely the number of cycles, scan rate and ratio between GO/Co(NO3)(2) concentrations in the electrolyte. It is shown that, if the appropriate conditions are selected, it is possible to produced binder-free composite electrodes with improved electrochemical properties using a low-cost, facile and scalable technique. The optimized Er-GO/CoOx developed in this work exhibits a specific capacitance of 608 F g(-1) at a current density of 1 A g(-1) and increased reversibility when compared to single CoOx. (C) 2015 Elsevier B.V. All rights reserved.