P.V. Kazakevich

Internal segregation of nanoparticles irradiated by laser radiation

The effect of the removal of zinc from brass nanoparticles has been experimentally discovered upon irradiating their suspension in ethanol by laser radiation. The analysis of the absorption spectra of nanoparticles shows that brass nanoparticles are transformed to copper nanoparticles during irradiation. The results are interpreted in terms of the high-pressure-induced modification of the phase diagram of nanoparticles. This pressure is caused by, first, the small radius of nanoparticles and, second, the pressure of the surrounding-liquid vapors upon the laser heating of nanoparticles.

Formation of core-shell nanoparticles by laser ablation of copper and brass in liquids

Experimental results are presented on the ablation of copper and brass targets in a liquid environment: ethanol, acetone, or water by irradiation with either a pulsed copper vapour laser (0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). The ablated material was ejected into the surrounding liquid as nanoparticles of average size 20 nm. The nanoparticle composition depends on the nature of the liquid. Ablation of 60%Cu, 40%Zn brass in ethanol results in formation of core-shell nanoparticles. Brass nanoparticles were characterized by a well-defined plasmon peak at 510-520 nm.

Frequency up-conversion of infrared laser radiation in the human retina

Experimental observation is reported of conversion in a human retina of infrared laser radiation (with a wavelength of 1.06 μm) into the visible upon scattering by a solid target. The wavelength of this visible radiation, as estimated by several independent observers, is around 0.557 μm. Frequency up-conversion is observed down to a peak power on the retina of only 150 W/cm2, while, for other laser sources, this threshold is as low as 1 W/cm2. It is suggested that the observed conversion is due to the second-harmonic generation in the periodic structure of the retina of a human eye. Deviation of the observed wavelength from that of the second harmonic in vacuum is ascribed to the spectral dependence of the refractive index of rhodopsin molecules within the retina.