With the vast advancement in electronic devices, there have been more and more demands to go down to smaller and smaller sizes for the sake of compactness. It is interesting to see how the properties of these so-called nanoparticles differ from those of the bulk and how some novel beneficial aspects arise out of them, by virtue of their small size effects. In this dissertation, we have attempted to understand three different aspects of nanoparticle applications, namely (a) photocatalysis, (b) luminescence and (c) alloying.