(707b) Sensing Chemical and Biological Substances with CdS Nanowires

Sensing of amino acids and metal ions with CdS nanowires was discussed. First, differential sensing of tyrosine and serine achieved with well aligned CdS nanowire arrays by exploring the pH-dependent photoluminescence behavior of the nanowire arrays toward exposure to the two amino acid solutions was successfully demonstrated and discussed. The contrasting trend in photoluminescence intensity with respect to variations in analyte concentration observed at pH 11 served as the check point for the present differential sensing. Second, sensing of Ag+ and Cu2+ with ethylenediamine (EN)-capped CdS nanowires (NWs) was successfully demonstrated and the relevant mechanism was revealed with a direct observation of the side product of the sensing event. The binding of Ag+ and Cu2+ at the surfaces of the EN-capped CdS NWs triggered an in-situ growth of Ag and Cu nanocrystals, respectively, causing decay in the photoluminescence of the CdS NWs and rapid color change of the solution recognizable to naked eyes.