| Nanosized particles are important because of their unique properties, different from the bulk, which leads to their enhanced catalytic, photocatalytic and electronic properties. This work has dealt with three different nanoparticle systems in the context of three different aspects of nanoparticle properties: (a) photocatalytis (TiO2/metal) system, (b) luminescence (CdSe) (c) alloying (Pt-Ag and Pd-Ag).; The initial photocatalytic enhancement obtained by adding noble metal on semiconductor nanoparticles, degrades as fast as in 15 minutes and questions their long-term performance. XANES measurements on such irradiated systems like TiO2/Au, TiO2/Pt, TiO2/Ir indicates a positive oxidation state of these noble metals which renders them as recombination centers for photo-excited electrons and explains the decreased photocurrent. The oxidation is caused by holes. The EXAFS results also indicate a change of the interfacial structure under the effect of UV-irradiation, thus affecting the energetics. The change induced varies from metal to metal. Au nanocluster forms following UV while there is oxide formation in cases of Pt and Ir.; CdSe nanocrystals have potential use as non-linear optical materials. The luminiscence characteristics from these particles can be controlled with surface treatment, by changing the charge-trapping characteristics and electron/hole relaxation dynamics. A current problem under consideration in the synthesis of CdSe nanoparticles is the improvement of the stability of the capping material. A preliminary XAFS study has been conducted on novel CdSe nanoparticles synthesized with CdO precursor capped with TOPO. By changing the initial synthesis parameters, the EXAFS results show an extra layer of Cd capping in the case with higher Cd percentage, accounting for their observed luminescence stability.; Bimetallic nano-catalysts have enhanced properties compared to monometallics, the quality of their performance being related to the degree of alloying of the two metals. The binary phase diagram of bulk metals is modified in nanoparticles by the presence of surface. The degree of alloying has been probed in 2 nm (smallest attainable size) Ag/Pt systems (completely immiscible in bulk) and cylindrical 2 nm wide Ag/Pd systems (completely miscible in bulk). In both the cases, the metals tend to retain their bulk alloying characteristics. Pt and Ag segregate while Pd and Ag alloy. |
