STM and STS Studies of One-Dimensional Row Growth: Ag on Si(5 5 12)

We have studied the growth of Ag on Si(5 5 12) using scanning tunneling microscopy and spectroscopy (STM/STS). At metal coverages as low as 0.05 monolayer (ML), Ag forms well-ordered overlayer rows, or one-dimensional clusters, on the underlying silicon surface. To produce these ordered structures, it is necessary to anneal the surface to 450°C. As the coverage is increased above 0.05 ML, the rows grow in length and number until the surface forms a periodic array of such structures at 0.25 ML. A statistical analysis of the rows reveals a linear increase in median row length as a function of coverage. With regard to their electronic behavior, STS measurements show a significantly narrower band gap along the Ag rows than is found on the underlying silicon structures. Therefore, the deposited Ag atoms do retain some metallic behavior.     

Algebras Generated by Semicentral Idempotents

Let be a unital K-algebra, where K is a commutative ring with unity. An idempotent is {\it left semicentral\/} if , and is {\it SCI-generated\/} if it is generated as a K-module by left semicentral idempotents. This paper develops the basic properties of SCI-generated algebras and characterizes those that are also prime, semiprime, primitive, or subdirectly irreducible. Minimal ideals and the socle of SCI-generated algebras are investigated. Conditions are found to describe a large class of SCI-generated algebras via generalized triangular matrix representations. SCI-generated piecewise domains are characterized. Examples are given that illustrate the breadth and diversity of the class of SCI-generated algebras.     

CW and Pulsed EPR Study of Silver Nanoparticles in a SiO2 Matrix

Metallic silver nanoparticles were prepared by the sol-gel method in an SiO2 matrix. The process includes complexation of silicon alkoxides with metal salts, hydrolysis, polycondensation, formation of powder, and subsequent thermal treatment first in oxidizing and second in reducing atmospheres. The sizes of metallic particles were determined both by X-ray diffraction and transmission electron microscopy. These measurements revealed sizes of metallic particles between 1 and 20 nm, depending upon processing conditions. The magnetic properties were investigated using electron paramagnetic resonance spectroscopy in the temperature range between 4 and 300 K. The spin-lattice relaxation time T1 was measured by pulsed EPR. The temperature dependence of T1 is described by the relation 1/T1 Tn, where 0.4 < n < 1. This behavior is unusual and different from any well-known relaxation processes such as Raman, Direct or the Orbach-Aminov.     

催化荧光法测定超痕量银的研究

基于在乙酸介质中，邻菲罗啉存在下，银对过硫酸钾氧化罗丹明６Ｇ具有催化作用，建立了催化荧光法测定超痕量银的新方法。方法的检出限为５．８０×１０＾－２μｇ／Ｌ，线性范围为２．００￣４０．００ｎｇ／２５ｍＬ。３０多种常见离子基本不干扰测定，将方法用于茶叶、阳极泥、水样中银含量的测定，结果满意。