Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10429674 | Biosensors and Bioelectronics | 2005 | 8 Pages |
Abstract
Sol-gel derived bulk and thin films were prepared from different compositions at low pH (â¼2.0) containing varying concentrations of ethanol from 15 to 60% at constant water (H2O)/tetraethyl-orthosilicate (TEOS) ratio (RÂ =Â 4). The fluorescence microscopic and spectroscopic measurements on fluorescent probe, Hoechst 33258 (H258) entrapped in these compositions were carried out at different days of storage to monitor the effects of concentration of ethanol on the internal environment of sol-gel materials. Fluorescence microscopic observations on sol-gel thin films, prepared by dip coating technique depicted uniform and cracked surface at withdrawal speed 1Â cm/min (high speed) and 0.1Â cm/min (low speed) respectively, which did not change during aging. Fluorescence spectral measurements showed emission maximum of H258 at â¼535Â nm in fresh sols at all concentrations of ethanol which depicted slight blue shift to 512Â nm during aging in bulk. No such spectral shift has been observed in sol-gel thin films coated at high speed whereas thin films coated at low speed clearly showed an additional band at â¼404Â nm at 45 and 60% concentration of ethanol after about one month of storage. Analysis of the fluorescence lifetime data indicated single exponential decay (1.6-1.8Â ns) in fresh sol and from third day onwards, invariably double exponential decay with a short (Ï1) and a long (Ï2) component were observed in sol-gel bulk with a dominant Ï1 at â¼1.2Â ns at all concentrations of ethanol. A double exponential decay consisting of a short component (Ï1) at â¼0.2Â ns and a long component (Ï2) at â¼3.5Â ns were observed at all ethanol concentrations in both fresh and aged sol-gel thin films. Further, distribution analysis of lifetimes of H258 showed two mean lifetimes with increased width in aged bulk and thin films. These results are likely to have strong implications in designing the internal environment for applications in biosensors.
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Authors
R. Gupta, S. Mozumdar, N.K. Chaudhury,