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13P-IV
Pioneering pulsed laser synthesis of colloids
A. Fojtik1
1NRNU MEPhI - Institut of Engineering Physics for Biomedicine, Moscow, Russia and Czech Technical University, Prague, Czech Republic
In the year 1991 it has been assumed, that all substantial facts and technologies regarding nanoparticles were already known. We have been using all available methods. What more was left? Could lasers be put to a good use? Attempts were made, but without any particular breakthrough... At that time, we aimed to new type of nanostructures and we really had not expected that usage of lasers could bring us something revolutionary. But there was a surprise waiting around the corner...We hoped that by an absorption of intense laser beam by a solid state material, producing temperature of plasma of many thousands kelvins (similar like in sonochemistry, where several thousand kelvins are reached in oscillating gas bubbles in a liquids [1]), similar effects could be reached. Nothing more, nothing less. Initiating plasma by a focused laser beam (694nm Ruby laser flash) to thin film of solid state material thus creates conditions similar to a plasma discharge and cause ablation condition. When some liquid surrounds „hot plasma spot", evaporated products are very quickly cooled down and very small nanoparticles can be produced. We hoped that maybe under these conditions new colloidal particles and clusters could be produced. Perhaps even some new form of nanostructures? All was working. What we had learnt from this experiment? We concluded that smaller particles are formed with increasing laser energy. Relatively broad size distribution was found in all experiments at laser synthesis of colloids. (At that time we did not expect that this idea would have such an enthusiastic following). Presently, situation for such a field of research, i.e., „Nanoparticle Generation by Lasers in Liquids", is becoming a much hotter topic due to availability of picosecond and femtosecond lasers. Where are we now and what's next? Open the research mainly for biomedical and biomedicine applications. For example, only this way can be prepare Fe /Ag magnetic nanoparticles, with high purity, which are at top interest for research against HIV virus and strategically defence against gram-positive batteries like anthrax (our attempt). See the lecture.
References
[1] A. Fojtik, A. Henglein, Laser Ablation of Films and Suspended particles in a Solvent: Formation of Cluster and Colloid Solutions, Ber. Buns. Phys. Chem., Vol.97, No.9, 1993, p.252.
