Abstract
Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell, created under laser heating of nanoparticle in water, were theoretically investigated. Vapor shell expansion leads to decreasing up to one to two orders of magnitude in comparison with initial values of scattering and extinction of the radiation with wavelengths 532 and 633 nm by system while shell radius is increased up to value of about two radii of nanoparticle. Subsequent increasing of shell radius more than two radii of nanoparticle leads to rise of scattering and extinction properties of system over initial values. The significant decrease of radiation scattering and extinction by system of nanoparticle-vapor shell can be used for experimental detection of the energy threshold of vapor shell formation and investigation of the first stages of its expansion.PACS: 42.62.BE. 78.67. BF
Highlights
Metal nanoparticles (NPs) and other nanostructures are widely used in nanotechnology, physical chemistry, catalysis, biology, and laser nanomedicine for different purposes during past 10 years [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
Optical detection and diagnostics of NPs via scattering have the advantages in comparison with others and can be carried out on the base of detection of radiation scattered from NPs placed in some medium
We found the general trends of nonlinear behavior of NP-vapor shell system-decrease of absorption and decrease and subsequent increase of scattering and extinction with increasing of shell radius, beginning from the initial period of shell expansion
Summary
Metal nanoparticles (NPs) and other nanostructures are widely used in nanotechnology, physical chemistry, catalysis, biology, and laser nanomedicine for different purposes during past 10 years [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] ( see the references in these papers). The determination of sizes, concentrations, and placements of NPs in different media is carried out by different methods-transmission electron microscopy, small-angle X-ray scattering, laser scanning microscopy, optical diagnostics, etc. Optical detection and diagnostics of NPs via scattering have the advantages in comparison with others and can be carried out on the base of detection of radiation scattered from NPs placed in some medium (liquid). Nonlinear thermo-optical effects can be achieved under the action of laser radiation on NP, absorption of laser energy, NP heating, heat exchange with surrounding liquid, and its explosive vaporization. The resulting shell around laser-heated NP can cause spatial confined and highly localized thermomechanical damage to the surrounding medium. This feature should be taken into account for practical applications. The process is observed by means of the detection of transmission and scattering of the probe laser beam with wavelength 633 nm [19,22,23,24,25,26]
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