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The adsorption of bovine serum albumin (BSA) on fused silica at neutral pH was investigated at the single-molecule level by total internal reflection fluorescence microscopy. Dye-labeled BSA molecules that adsorbed on the quartz surface lit up as discrete, fluorescent dots which eventually disappeared upon desorption. Movies of these events offered unprecedented details for kinetics modeling. The results suggested that 99.3% of the BSA was not sticky, and even if adsorbed, it would desorb in minutes. In contrast, the remaining 0.7% was not only sticky, but would anchor in due course. Such population heterogeneity, otherwise masked in ensemble measurements, sheds new light on our understanding of protein adsorption. The methodology is also generally applicable to the studies of macromolecules at interfaces.

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High-quality ZnS:Mn thin films have been deposited on ͑001͒Si substrates at various temperatures using pulsed laser deposition. Their structural properties were characterized by x-ray diffraction. Optical studies by spectroscopic ellipsometry, optical transmittance, and photoluminescence measurements were systematically carried out on all film samples. In the analysis of the measured SE spectra, a modified double-layer Sellmeier model was adopted to represent the optical properties of the ZnS:Mn films. In this model, the films were assumed to consist of two layers-a bottom bulk ZnS:Mn layer and a surface layer composed of bulk ZnS:Mn as well as void. Good agreement was obtained between the measured spectra and the model calculations. Changes in the refractive indices of the ZnS:Mn films as a function of growth temperature were investigated. The PL and absorption measurements revealed that the orange-yellow emission band at ϳ590 nm and the absorption edge at ϳ370 nm upshifted to shorter wavelengths for films deposited at higher substrate temperatures. These results imply that the energy gap of the ZnS:Mn films increases with growth temperature. The observed changes of optical properties in these films are correlated to their structural qualities.

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