This paper reports the synthesis of Au nanoparticles by 30-fs pulses irradiation of a sample containing HAuCl4 and chitosan, a biopolymer used as reducing agent and stabilizer. We observed that it is a multi-photon induced process, with a threshold irradiance of 3.8 × 10(11) W/cm2 at 790 nm. By transmission electron microscopy we observed nanoparticles from 8 to 50 nm with distinct shapes. Infrared spectroscopy indicated that the reduction of gold and consequent production of nanoparticles is related to the fs-pulse induced oxidation of hydroxyl to carbonyl groups in chitosan.
Articles you may be interested inEr:Yb-doped oxyfluoride silicate glass waveguide amplifier fabricated using femtosecond laser inscription Appl. Phys. Lett. 90, 131102 (2007) 3D-waveguides containing silver nanoparticles have been fabricated in tungsten leadpyrophosphate glass by femtosecond laser micromachining. Nucleation and growth of nanoparticles occur in a single step process when high repetition rate laser (MHz) is employed, while an additional annealing is required for the irradiation using kHz laser system. The presence of nanoparticles locally changes the refractive index, and, therefore, the elliptical structures produced by direct laser writing were able to guide light. By increasing the pulse energy applied during the micromachining, the waveguide size increased from 2 to 30 lm, while their propagation loss decrease from 1.4 to 0.5 dB/mm at 632.8 nm. V C 2014 AIP Publishing LLC.
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