Chapter One

The area of nanoparticles (nanocrystallites (nc) or quantum dots) is one of the most active areas of science today. In particular, silicon nanoparticles is a burgeoning and fascinating area of science and one that has significant technological implications. This new charge of interest came nearly a decade after the exciting discovery by Canham in 1990 of visible red photoluminescence (PL) at room temperature with a quantum efficiency of few percent, from electrochemically etched silicon (porous silicon (PS) layer). Although in the ensuing years, the quantum efficiency remained practically small, dashing hopes for optoelectronics integration from this development stimulated a variety of physical, chemical, physiochemical, and electrochemical techniques to produce dispersions of luminescent nanometre sized silicon crystallites. The research led by Nayfeh at Illinois in 2000 has shown that reducing the size of an elemental Si crystal to a few tens of atoms (~1nm), without altering its chemical composition, effectively creates a new material, a nanoparticle with novel properties – both electronic and non-electronic, including ultrabright ultrastable luminescence – that were not available before. This research demonstrated that single-element Si particles – an abundant, stable, environmentally benign, malleable nanomaterial – have versatile and wide-ranging optical, electronic, and (derivatized) biocompatible properties. These properties have drawn the interest of engineering, physics, chemistry, material science, and biology, and medical researchers alike.

Ultrabright silicon structures are part