Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell duri
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NANO EXPRESS
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Nonlinear thermo-optical properties of twolayered spherical system of gold nanoparticle core and water vapor shell during initial stage of shell expansion Victor K Pustovalov1* and Liudmila G Astafyeva2
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 Background 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 [1-15] (also 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. [1-15]. In many cases, 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). However, as NP radius r0 decreases, the scattered intensity drops as r06 and, as result, the detection difficulties will be increased [16]. Effective strategy for solving of this difficulty could be the use of nonlinear
* Correspondence: [email protected] 1 Belarusian National Technical University, Independence pr. 65, Minsk, 220013, Belarus Full list of author information is available at the end of the article
thermo-optical effects as a result of NP optical absorption and heating. 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 liquid evaporates around rapidly heated NP, and spherical vapor shell (bubble) is formed near to an NP surface. It is possible to determine the temperature of heated NP, or determine the thermal refractive index change of ambient medium or formation of vapor shell (bubble) in the heated vicinity of absorbing NP [8,17]. The formation and expansion of vapor nanobubbles is attractive tool for diagnostics and applications in laser nanotechnology [8,18-26]. The resulting shell around la
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