Formation of Au-Pt alloy nanoparticles on a Si substrate by simple dip-coating at room temperature.

Spherical Au-Pt alloy nanoparticles of 10 nm average size have been prepared on a H-terminated Si(100) substrate by an extremely simple method of dip-coating. X-ray photoelectron spectroscopy and glancing-incidence X-ray diffraction confirm the formation of Au-Pt alloy. The Au(3+) ions are first reduced on the Si substrate upon dipping, and the freshly formed Au nuclei then work as a "catalyst" by promoting the reduction of PtCl(6)(2-) ions on the Au nuclei. The subsequent interdiffusion of Au and Pt atoms leads to the observed alloy formation. The present method provides an environment-friendly, low-cost route to preparing anode electrodes in fuel cells.

Efficacy of a sealant : study on the efficacy of a sealant (Light Bond) in preventing decalcification during multibracket therapy.

AIM: Decalcification remains a serious problem when treating patients with a multibracket appliance. The objective of this study was to classify patients with decalcification in terms of where it occurs, and to compare its potential reduction using a smooth surface sealant with a control group with no sealant. We also aimed to discover whether this enamel sealant would affect the incidence of bracket loss. MATERIAL AND METHODS: A total of 78 patients aged 11.6 to 39.5 years (median: 15.9 years) treated at a private orthodontic practice were examined for signs of decalcification within a maximum of 3 months after debonding. The indexing system used for evaluation subdivided the tooth's labial surface into four zones for quantifying the area affected (0-3) and severity of the decalcification (0-3). Preexisting areas of demineralization were excluded based on photographic evidence. We used cumulative logistical regression to investigate the sealant effect. Bracket loss was evaluated according to patient records. RESULTS: In patients with sealed labial surfaces, we observed a significantly reduced level of severity in the areas affected by decalcification (p = 0.013) and the depth of demineralization (p = 0.080). Sealant application reduced the median incidence of bracket loss by half. CONCLUSIONS: Our results demonstrate that Light Bond Reliance, the viscous sealant used in this study, may assist in preventing or reducing the incidence of enamel demineralization. We also noted a correlation between the sealant's use and the incidence of bracket loss in the treatment group.

Near-surface oxidized sulfur modifications and self-assembly of thiol-modified aptamer on Au thin film substrates influenced by piranha treatment.

Self-assembly of thiol-modified oligonucleotides on Au films has great importance for biosensor applications. Prior to the self-assembly, a piranha treatment (PT) is commonly used to clean the Au surface. Here we report that near-surface oxidized sulfur modifications on Au thin films by PT for longer than 60 s have serious effects on the self-assembled monolayer (SAM) formation of thiol-modified single-stranded thrombin binding aptamer (s-TBA), and a PT time of 10-30 s is optimal for s-TBA SAM formation. These results have important implication to SAM formation of biomolecules, especially for the thiol-modified ones where a careful consideration of this key step could significantly enhance the SAM formation and biosensor performance.