The book is about the synthesis and characterization of Zinc oxide nanoparticles. Here nanoparticles are synthesized by sol gel and direct precipitation method. Among the semiconductor metal oxides, some semiconductor structures are identified for their unique and vast potential applications in optoelectronic, field effect transistors, solar cells, photoluminescence devices, and diluted magnetic semiconductors, etc. The interesting development in optoelectronic applications arises due to environmentally friendly short energy, laser diodes and white light producing technologies that work beyond room temperature.