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Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell during initial stage of shell expansion.

Pustovalov VK, Astafyeva LG - Nanoscale Res Lett (2011)

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Belarusian National Technical University, Independence pr, 65, Minsk, 220013, Belarus. pustovalovv@mail.ru.

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.

No MeSH data available.


Related in: MedlinePlus

Efficiency cross sections σabs (a) and σsca (b) of laser radiation. With wavelength 532 nm by two-layered spherical system gold NP core and water vapor shell for the radii r0 = 10 nm (1), 20 nm (2), 40 nm (3), 60 nm (4), 80 nm (5), and 100 nm (6), and for the range of system radii r1 = (1 ÷ 10) r0.
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Figure 5: Efficiency cross sections σabs (a) and σsca (b) of laser radiation. With wavelength 532 nm by two-layered spherical system gold NP core and water vapor shell for the radii r0 = 10 nm (1), 20 nm (2), 40 nm (3), 60 nm (4), 80 nm (5), and 100 nm (6), and for the range of system radii r1 = (1 ÷ 10) r0.

Mentions: Figure 5 presents cross sections σabs and σsca of laser radiation with wavelength 532 nm by two-layered spherical system gold NP core and water vapor shell for the radii r0 = 10, 20, 40, 60, 80, and 100 nm as a function of the radii relations r1/r0 in the interval of radii r1 = (1 to 10)r0. As shown in Figure 4a, absorption cross sections σabs are decreased for all range of 1 <r1/r0 < 10 and for the interval of core radii 10 nm ≤ r0 ≤ 100 nm. At first, this decrease is reasonably sharp from two to four times, and then after achievement of value Δr1 ≤ r0, σabs slowly reduces. It is determined by the shielded effect of vapor shell when irradiation cannot reach the absorbing core. The growth of the core radii results in essential increase of absorption cross sections σabs as long as r0 ≤ 60 nm. For r0 ≤ 60 nm, the dependence of σabs(r0) becomes oscillating and undergoes less effect of core radius. Scattering cross sections of σsca are also lowered in the interval of 1 <r1/r0 < 2 (Figure 4b). Then, σsca is sharply increased in the interval r1/r0 = 2 to 10. Scattering cross section σsca is decreased up to one to two orders of magnitude depending on r0, for example, for r0 = 20 nm is decreased from σsca = 2.5 × 10-12 cm2 (r1/r0 = 1) to σsca = 8.5 × 10-14 cm2 (r1/r0 = 2) for λ = 532 nm. After achievement of minimal value, σsca increases and at r1 = (2 to 3.5) r0 cross section σsca achieves initial value of σsca(r1 = r0). It means that the scattering property of system NP-vapor shell is equal initial value of σsca for pure NP at this value of r1. After this moment, the increase of r1/r0 leads to growth of σsca up to values two to four orders of magnitude greater than initial values of this one. This effect is due to the complicated two-layered spherical system, and the fact that the growth of vapor shell leads to change of median complex refractive index of two-layered NP: the real part of the complex refractive index increases and the imaginary part is decreased. Therefore, at first, the scattering cross sections of NPs fall and then begin to grow when expanding the vapor shell thickness and value of r1/r0 increases.


Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell during initial stage of shell expansion.

Pustovalov VK, Astafyeva LG - Nanoscale Res Lett (2011)

Efficiency cross sections σabs (a) and σsca (b) of laser radiation. With wavelength 532 nm by two-layered spherical system gold NP core and water vapor shell for the radii r0 = 10 nm (1), 20 nm (2), 40 nm (3), 60 nm (4), 80 nm (5), and 100 nm (6), and for the range of system radii r1 = (1 ÷ 10) r0.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211867&req=5

Figure 5: Efficiency cross sections σabs (a) and σsca (b) of laser radiation. With wavelength 532 nm by two-layered spherical system gold NP core and water vapor shell for the radii r0 = 10 nm (1), 20 nm (2), 40 nm (3), 60 nm (4), 80 nm (5), and 100 nm (6), and for the range of system radii r1 = (1 ÷ 10) r0.
Mentions: Figure 5 presents cross sections σabs and σsca of laser radiation with wavelength 532 nm by two-layered spherical system gold NP core and water vapor shell for the radii r0 = 10, 20, 40, 60, 80, and 100 nm as a function of the radii relations r1/r0 in the interval of radii r1 = (1 to 10)r0. As shown in Figure 4a, absorption cross sections σabs are decreased for all range of 1 <r1/r0 < 10 and for the interval of core radii 10 nm ≤ r0 ≤ 100 nm. At first, this decrease is reasonably sharp from two to four times, and then after achievement of value Δr1 ≤ r0, σabs slowly reduces. It is determined by the shielded effect of vapor shell when irradiation cannot reach the absorbing core. The growth of the core radii results in essential increase of absorption cross sections σabs as long as r0 ≤ 60 nm. For r0 ≤ 60 nm, the dependence of σabs(r0) becomes oscillating and undergoes less effect of core radius. Scattering cross sections of σsca are also lowered in the interval of 1 <r1/r0 < 2 (Figure 4b). Then, σsca is sharply increased in the interval r1/r0 = 2 to 10. Scattering cross section σsca is decreased up to one to two orders of magnitude depending on r0, for example, for r0 = 20 nm is decreased from σsca = 2.5 × 10-12 cm2 (r1/r0 = 1) to σsca = 8.5 × 10-14 cm2 (r1/r0 = 2) for λ = 532 nm. After achievement of minimal value, σsca increases and at r1 = (2 to 3.5) r0 cross section σsca achieves initial value of σsca(r1 = r0). It means that the scattering property of system NP-vapor shell is equal initial value of σsca for pure NP at this value of r1. After this moment, the increase of r1/r0 leads to growth of σsca up to values two to four orders of magnitude greater than initial values of this one. This effect is due to the complicated two-layered spherical system, and the fact that the growth of vapor shell leads to change of median complex refractive index of two-layered NP: the real part of the complex refractive index increases and the imaginary part is decreased. Therefore, at first, the scattering cross sections of NPs fall and then begin to grow when expanding the vapor shell thickness and value of r1/r0 increases.

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Belarusian National Technical University, Independence pr, 65, Minsk, 220013, Belarus. pustovalovv@mail.ru.

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.

No MeSH data available.


Related in: MedlinePlus