Theoretical and Experimental Research of Luminescent Properties of Nanoparticles

Abstract

Theoretical research is performed on isolated nanoparticles (NPs) and NP-containing composite films with establishing analytically the concentration of nonequilibrium charge carriers and luminescence intensity as functions of surface recombination rate s, radius, diffusion length, lifetime of minority charge carriers, and other parameters. A hyperbolic dependence of the photoluminescence intensity (PL) on the parameter s is found. It is shown theoretically and experimentally that the photostimulated rise of s of NPs brings about quenching, while its decline favors amplification of PL. The microphotoluminescence PL intensity is established as a function of exciting laser exposure time for powdered carbon nanoparticles (CNPs), solutions of CNPs, and composite films based on PVOH polymers and CNPs with average particle diameters of 1.3 and 1.7 nm. Furthermore, the PL signal intensity of films processed at temperatures of 100–200°C decreases upon their exposure to a high-power-density 532-nm excitation radiation and rises in the case of films treated at 220–340°C. Almost always, the PL intensity of exposed dry CNP powders abruptly drops. The study allows putting forward a new method for contactless and rapid measurement of the parameters of luminescent NPs.