The electrodeposition of highly reflective lead dioxide coatings

In the presence of a suitable surfactant, such as hexadecyltrimethylammonium chloride or bromide, highly reflective and hard lead dioxide coatings with a black appearance can be electrodeposited from methanesulfonic acid media at room temperature (295 K). The reflective PbO₂ coatings are compact, adherent to the (vitreous carbon or carbon-polymer) substrate and can be formed at current densities of 10 to 100 mA cm^?2 at a thickness up to several hundred microns. The coatings were characterised by measurement of surface optical reflectance, surface roughness, surface microstructure, phase composition and crystallite size. The reflective PbO₂ films were found to mainly consist of the alpha (orthorhombic) phase with feather-like and orientated microstructures. The crystallite size and surface roughness were in the order of tens of nanometres and their optical reflectance was several orders of magnitude higher than matte coatings produced in the absence of additives.     

Mersiphyllines A and B from Kopsia. Determination of relative configuration at a quaternary center via formation of an alkaloid-borane complex

Two new pentacyclic alkaloids, mersiphyllines A (1) and B (2), belonging to the novel mersinine group, and incorporating carboxylic acid functionalities on a quaternary center, were isolated from Kopsia singapurensis. The structures were determined by spectroscopic analysis. Determination of the relative configuration at the quaternary center bearing the acid function was facilitated by the formation of an alkaloid-borane complex. The structure of 1 was also confirmed by X-ray diffraction analysis.     

High-index and low loss polyethylene terephatate optical waveguides

In this paper, the fabrication and characterization of a high-index low loss polyethylene terephatate (PET) optical waveguide is presented. Dip-coating technique has been used to fabricate the optical waveguide using PET. Various waveguide properties, such as mode effective refractive index, optical loss, dispersion and waveguide thickness as a function of temperature of waveguides and substrates have been reported. Optical losses of as low as 0.7 dB cm^–1 waveguides can be obtained if the formation temperature can be controlled between 30 and 35°C. In addition, we suggested that it is a suitable material for optoelectronic waveguide devices.