[show abstract][hide abstract] ABSTRACT: Surface-enhanced Raman scattering (SERS) study of tryptophan was carried out in silver hydrosol. The surface adsorption properties of tryptophan were investigated due to its biological importance. Tryptophan is an essential amino acid needed for the normal growth in infants and for nitrogen balance in adults. DFT calculations using B3LYP functional with LANL2DZ basis set was carried out to support the experimental Raman and SERS data. The strong enhancement of 1343 cm(-1) band, assigned to the CO(2) sym. stretching vibration in the SERS spectrum along with a red shift of 63 cm(-1), manifests that chemical mechanism contributes to the SERS activity. Moreover, the observed features in the SERS spectrum as well as theoretical calculations infer that tryptophan is chemisorbed to the silver surface directly through the oxygen and nitrogen atoms of the carboxylate and amino groups with an edge-on orientation with the indole ring lying nearly perpendicular to the silver surface. The SERS enhancement factors for various Raman vibrations of tryptophan were found to be of the order of 10(5)-10(6).
Journal of Colloid and Interface Science 05/2012; 380(1):141-9. · 3.17 Impact Factor
[show abstract][hide abstract] ABSTRACT: The synthesis and characterization of water-soluble dispersions of Ag nanoparticles by the reduction of AgNO(3) using tryptophan under alkaline synthesis conditions are reported. The Ag nanoparticle formation was very slow at low concentration and rapid at extremes. For surface modification and redox reactions, manipulating the interparticles interaction controlled the size of Ag nanoparticles aggregates. Our results suggest that the replacement of the BH(4)(-) ions adsorbed on the nanoparticle surface by tryptophan destabilizes the particles and further caused aggregation. A mechanism is proposed for the formation of silver nanoparticles by tryptophan. The experimental results are supported by theoretical calculations. The Ag nanoparticles were characterized by UV-vis absorption, dynamic light scattering and transmission electron microscopy techniques.
[show abstract][hide abstract] ABSTRACT: Photophysical characteristics of capped and uncapped CdS particles have been investigated in aqueous solution. It is seen
that the fluorescence spectrum shifts towards lower energies in the presence of toluene dithiol (TDT) and dimercaptophthalic
acid (DMPA). This shift, which is due to quenching of shallow traps, is more predominant with TDT. Also, the presence of excess
Cd2+ ions at the surface of the CdS particles facilitates the binding of dithiolenes.
Research on Chemical Intermediates 01/2008; 34(1):31-41. · 0.88 Impact Factor