The main objective of this work is to provide information associated with the optical, structural and morphological properties of Si nanoparticles needed to accomplish novel applications. Chapters 1 deal with a short literature overview of the research on Si nanoparticles and introduce the state-of-the-art in the synthesis, properties and applications of Si nanoparticles. In Chapter 2, the experimental procedures for synthesizing and modifying Si nanaoparticles thin films are described. In this chapter concentrates on the description of the PLA technique for fabricating Si nanoparticles films and then discusses which diagnostic tools to examine these parameters. This leads to a natural demarcation of the analytical tools, into those for examining the spectroscopy, the structural and surface morphology properties of the deposited films. The chapter ends with a list of the instrumentation used in the experimental work. In Chapter 3, the experimental observations, calculations and explanations of the findings are discussed. Finally, the conclusions drawn in the work are presented in Chapter 4.