SEMICONDUCTOR NANOPARTICLES AND THEIR INTERACTION WITH ORGANIC DYES

Abstract

The composites having the compositions Ti02/Dye, CdS/Dye, and CdS/Ti02/Dye (where Dye is an organic dye possessing donor-acceptor architecture and carboxylic acid groups) have been synthesized and characterized by different physical methods such as absorption spectroscopy, fluorescence spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and thermogravimetric analysis. The composites derived from (E)-2-cyan-3-((4-(diethylamino) phenyl) acrylic acid (D2) and Ti02 exhibited a morphology change from spherical shape of the Ti02 nanoparticles to the rod shape in the composite. The change in the morphology may be due to the presence of alkyl chain in the dye. The thermal studies revealed an improved stability for each composite when compared to that of the dyes. This establishes the presence of interaction between the anatase Ti02 nanoparticles and the dye molecules. The interaction of blue and green emitting CdS colloids with the dyes were also investigated by optical and thermal studies. Dyes (Z)-2-cyano-3-((4-(dimethylamino) phenyl) acrylic acid (D1), (E)-2-cyano-3-((4-(diethylamino) phenyl) acrylic acid (D2) and (E)-2-cyano-3-((4-(diphenylamino) phenyl) acrylic acid (D4) effectively accepted the energy from the blue and green emitting CdS colloids in solution. On the contrary no efficient energy transfer occurred between the blue and green emitting CdS particles to the dye (E)-2-cyano-3-((4-(methoxy) phenyl) acrylic acid (D3). The anomalous behavior is attributed to the comparatively smaller overlap integral observed between the emission of CdS and absorption of the dye (D3). Further a slight red-shift observed on increasing the dye concentration may be arising due to the aggregation of the dyes on the CdS surface. The tricomponent composite CdS-Ti02/D2 also showed a change in the morphology from homogeneous spherical particles (CdS-Ti02) to nanofibers (CdS-Ti02/D2).