Simulation of the Linear and Nonlinear Optical Properties of Colloids Containing Metallic Core–Dielectric Shell Nanoellipsoids

Furtado, Livia A. de M.; Malagón, Luis Arturo Gómez

doi:10.1007/s11468-014-9753-9

Cited by 7 publications

(5 citation statements)

References 32 publications

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“…For NPs made of noble metals, such as silver and gold, the optical response, based on a microscopic description, is associated with the interaction of their free electrons with the incident optical field, from the intraband and interband transitions. The contributions for the dielectric function of isolated NPs can be described by using the critical point model (CPM), which includes interband transitions in the violet/near-UV region, in conjunction with the Drude free-electron model, through the expression: , where , with ε ∞ being the high-frequency limit dielectric permittivity, λ p the plasma wavelength, and γ k the damping in the k- direction because anisotropic particles are analyzed ( k = x , y , and z ). The parameters within the sum, such as the amplitude, A j , phase, ϕ j , and the interband transition wavelength, λ j , referring to the CPM were obtained by fitting the dielectric function of gold (bulk) obtained experimentally in ref , as reported in refs and .…”

Section: Theoretical Analysismentioning

confidence: 99%

“…The contributions for the dielectric function of isolated NPs can be described by using the critical point model (CPM), which includes interband transitions in the violet/near-UV region, in conjunction with the Drude free-electron model, through the expression: , where , with ε ∞ being the high-frequency limit dielectric permittivity, λ p the plasma wavelength, and γ k the damping in the k- direction because anisotropic particles are analyzed ( k = x , y , and z ). The parameters within the sum, such as the amplitude, A j , phase, ϕ j , and the interband transition wavelength, λ j , referring to the CPM were obtained by fitting the dielectric function of gold (bulk) obtained experimentally in ref , as reported in refs and . However, intraband transitions are size dependent, owing to the confinement of conduction electrons in nanometric dimensions.…”

Section: Theoretical Analysismentioning

confidence: 99%

“…For instance, in metal–dielectric core–shell NPs, although a reduction in thermal conductivity is expected due to the dielectric shell, the nanostructure shows better thermal stability and avoids melting of the metal core. In this case, the effective dielectric function [eq ] can be modeled by using two confocal ellipsoids, substituting P k for P S,k and ε (λ) for the dielectric function of an isolated core–shell NP, given by where ε s is the dielectric constant of the shell ( ε s = 2.25 for the SiO 2 shell), ε C , k = ε NP , k is given by eq , and γ = ( L NP, x L NP, y L NP, z )/( L S,x L S,y L S,z ) is the ratio between the dimensions of the inner (core NP) and outer (shell) ellipsoids. The depolarization factors P NP , k and P S , k are calculated in the same way as in eq , but using the core NP and shell dimensions, respectively.…”

Section: Theoretical Analysismentioning

confidence: 99%

“…45 For NPs made of noble metals, such as silver and gold, the optical response, based on a microscopic description, is associated with the interaction of their free electrons with the incident optical field, from the intraband and interband transitions. The contributions for the dielectric function of isolated NPs can be described by using the critical point model (CPM), which includes interband transitions in the violet/ near-UV region, in conjunction with the Drude free-electron model, through the expression: 46,47 where…”

Section: Theoretical Analysismentioning

confidence: 99%

“…For instance, in metal− dielectric core−shell NPs, although a reduction in thermal conductivity is expected due to the dielectric shell, the nanostructure shows better thermal stability and avoids melting of the metal core. In this case, the effective dielectric function [eq 2] can be modeled by using two confocal ellipsoids, 46 substituting P k for P S,k and ε (λ) for the dielectric function of an isolated core−shell NP, given by…”

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confidence: 99%

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Improving the Performance of Direct Solar Collectors and Stills by Controlling the Morphology and Size of Plasmonic Core–Shell Nanoheaters

et al. 2021

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Plasmonic nanofluids, based on metal nanoparticles (NPs), has received tremendous attention for its potential to increase the efficiency of solar energy harvesting and harnessing systems. The ability to manage their optical absorption by tuning localized surface plasmon (LSP) bands is the reason why metal NPs are considered excellent nanoheaters with unique thermo-optic properties. In this work, we demostrate the influence of the tuning of plasmonic nanofluid absorption bands in different spectral regions, by modifying the morphology and size of the core–shell NPs, on the efficiency of plasmonic nanoheaters to heat fluids and generate steam. Five plasmonic nanofluids containing spherical Au@SiO2, rodlike Au@SiO2, with three different aspect ratios, and spherical SiO2@Au nanoshells were fabricated and characterized to study the local heating induced by plasmon-enhanced light absorption. Gains of up to 28.3 times in the nanofluid temperature increase in direct absorption solar collectors (DASCs) and 7.5 times in the amount of steam generated in the solar ethanol distillation were measured from control over LSP resonances of spherical and rodlike core–shell NPs. Energy distribution analysis shows that plasmonic nanofluids present an efficient energy transfer management, dedicating ∼72% of the absorbed energy to heating liquids at low levels of solar irradiance. However, at high solar irradiances, the good spectral matching between the plasmonic nanofluid LSP bands and the solar irradiance spectrum promotes strong local heating around the core–shell NPs, allowing local temperatures above the boiling point to be reached. Under these conditions, plasmonic nanofluids spend a small amount of energy to heat liquids and they transfer ∼83% of the absorbed energy to generate steam. Thus, a 7.7-fold increase in solar ethanol vaporization rate was achieved. The experimental results, understood from the optical properties of core–shell plasmonic NPs by using the Maxwell–Garnett theoretical model, corroborate the importance of fabricating nanoheaters with projected geometries to maximize the efficiency of solar collectors and stills.

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