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A method was developed to prepare silver-doped sol-gel Ðlms for surface-enhanced Raman scattering (SERS) detection. The technique involves Ðrst doping silver ions as a silver ammine complex into a sol-gel [ Ag(NH 3 ) 2 ' ] matrix, followed by chemical reduction of the doped silver ions into the corresponding silver metal particles. The silver-doped sol-gel Ðlms coated on a glass substrate exhibit strong enhancement (24 000-fold) of Raman scattering from molecules adsorbed on the surface. Very stable SERS spectra of benzoic acid over a period of 48 h were obtained with the new silver substrate.

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Any modern society should be concerned over the well-being of the visually impaired citizen. It is the responsibility of the society to lessen the inconvenience and anxiety experienced by the handicapped. In addition to helping one to avoid obstacles on the sidewalks, technology can further help in navigating to places. In this paper we attempt to create a supportive environment with timely and useful information to guide the visually impaired to comfortably roam in a city that cares.

The characteristics of a rubidium metal vapor filter (MVF) for its use as a laser scatter filter for single molecule detection (SMD) were investigated. This investigation was done by a simulation along with experimental observation. A monochromator was used to elucidate the spectral components of the background in SMD. The major contributors to the background were laser transmission and fluorescence of the rubidium vapor. Experiments on the filter's performance under varying conditions such as MVF temperature, MVF pressure, and laser power were done. It was found that the integrated transmission intensity decreased with increasing pressure and temperature while it increased for increasing laser powers. The computer simulation modeled the experimentally observed profiles very well. Through the simulation, it was determined that the limitation on the attenuation by the MVF was due to the transmission of the broad-band stimulated emission “wings” of the Ti:sapphire laser.