In the last few years, a little word has attracted enormous attention, and investigation from all over the world. The word is "nano." What it presents in terms of science and technology, which are also called nanoscience and nanotechnology, is much more than just a word describing a specific length scale. It has dramatically changed every aspect of the way we think in science and technology and will certainly bring more and more surprises into our daily life as well as into the world of the future. This thesis consists of four parts of which Part-1 gives a brief overview of the synthesis, properties and applications of nanomaterials. Part-2 deals with the synthesis and characterization of different nanostructures of metal oxides and a detailed study of their gas sensing characteristics. Part-3 of the thesis contains results of studies on the electrical properties and hydrogen-sensing characteristics of field effect transistors (FETs) based on nanorods of ZnO and WO2.72. Part-4 of the thesis deals with the supercapacitive behavior of RuO2 and IrO2 functionalized mesoporous carbon and results of studies on the interaction of SWNTs with electron donor and acceptor molecules.