Gold nanoparticles: fabrication by laser ablation technique and their optical and morphological studies

Abstract

Material particles of the size of few nano-meters to couple of hundreds of nano-meters exhibit size and shape dependent properties and the consequent versatility and importance in their use have made them an exciting and interesting field of research. Of these, noble metal nano-particles, particularly gold nano-particles have shown tremendous potential for their wide range of applicability not only in fundamental sciences like physics, chemistry and biology, but also in applied sciences such as in designing and developing varieties of nano-particle based devices and sensors. The number of articles published on noble metal nano-particles, particularly gold and silver nano-particles has gone up in exponential rate since the early nineties of the last century. One of the major thrust areas of nano-particles and their science and technology research are their fabrication. In the nineties of the last century and the first half of the last decade chemical methods dominated over all other methods, including the laser ablation technique which started emerging. The main disadvantage including a host of other drawbacks of conventional nano-particle generation techniques such as mechanical milling and grinding or even the chemical method like the sol-gel process is that it almost invariably picks up impurities which make them unusable and hence undesirable for many applications e.g. biological applications. Pulsed laser ablation is an attractive and a promising alternative, addressing the shortcomings of the conventional methods, including the chemical methods. In this chapter we discuss mostly about the nano-particle fabrication, with particular emphasis on gold nano-particles in colloids, using nano second laser pulses. A number of variables of the ablating laser pulse have been used to control the size of the fabricated nano-particles. These were done without the use of chemicals/chemical surfactants, which provided a good and clear understanding of the laser parameters on the control of the nano-particle size. Possible explanations of all observations are given.