A quantitative comparison of third-order nonlinear optical properties of colloidal gold nanoshells (NSs) and gold nanorods (NRs) in water solutions has been carried out using open- and closed-aperture Z-scan measurements, performed with femtosecond laser pulses over a broad range of wavelengths. Absorption saturation was found to be a dominant effect for all the studied nanoparticles; however, two-photon absorption (2PA) properties were also detected, and were clearly resolved especially at the shortest wavelengths used. The value of the merit factor σ2/M (2PA cross section scaled by the molecular weight) for the NRs (10×35 nm) at 530 nm is 7.5 (GM·mol/g), while for the NSs it is 1.9 (GM·mol/g) at the same wavelength.
A detailed comparison of third-order nonlinear optical properties of colloidal gold nanoshells (NSs) and gold nanorods (NRs) in water solutions has been carried out with the open- and closed-aperture Z-scan measurements, performed with femtosecond laser pulses over a broad range of wavelengths. Absorption saturation was found to be a dominant effect for all the studied nanoparticles, however two-photon absorption properties are also detected, especially at the shortest wavelengths studied. The value of the merit factor σ2/M (two-photon absorption cross section scaled by the molecular weight) for the NRs (10nm × 35 nm) at 530 nm is 7.5 (GM·mol/g), while for the NSs is 1.9 (GM·mol/g) at the same wavelength.
We synthesized a mixture composed of gold nanoparticles of various shapes using the wet chemistry method. The final
solution contained long nanorods, balls, disks and different spherical nanoparticles. To separate particles of individual
shapes from the reaction mixture, the solution was centrifuged in a glucose density gradient. A distribution of
nanoparticles based on their diameters was observed and each section was collected independently and each type of
nanoobjects was characterised separately. Finally, the difference in nanoparticle shapes depending on the presence of
Ag+ ions in the growth solution is reported and its influence on the separation is discussed.
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