Photoinduced formation of colloidal Au by a near-infrared femtosecond laser

Abstract

A Au colloid was prepared in a 5 mM HAuCl 4 solution through irradiation with a focused infrared femtosecond laser at 800 nm. The Au colloid was characterized by absorption spectra, transmission electron microscopy, and x-ray diffraction analysis. The appearance of absorption peak around 526 nm in the absorption spectra and the wine-red color of sample solution HAuCl 4 under focused laser irradiation verified the formation of Au colloid. The solution color changed in the order of yellow → orange → wine-red due to the local formation of Au nanoparticles near the focus. The pulse energy, focus position of laser beam, and solvent composite play important roles in formation, grain size, and stability of the Au colloid. A mechanism for the precipitate of Au nanoparticles was proposed, and a multiphoton process of femtosecond laser was involved.

Recent Advances in the Synthesis of Plasmonic Bimetallic Nanoparticles

“…Photochemical reduction is an important approach and has been applied to the synthesis of metallic nanoparticles [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]. However, its use in the synthesis of bimetallic nanoparticles is not well established.…”

Metal ion reductions by femtosecond laser pulses with micro-Joule energy and their efficiencies

“…[2][3] In the case of singly and/or doubly charged ions, they seem to develop into nanoparticles (NPs). NP formation using femtosecond pulses has been extensively studied, including for NPs of Au [4][5][6][7][8][9], Ag [5,10,11], Pd [12,13], and others. [14] The NP formation would be initiated by a reduction of charged metal and complex ions to neutral atoms by electrons produced by water ionization and/or direct multi-photon atomization.…”

“…The simple absorption experiments in this paper reveal that water is the major absorption species and atomization and/or surfactant ionization via multi-photon absorption makes a minor contribution. 4 ii) Second, how efficient are these reductions? In the present study, we successfully estimated the initial reduction efficiencies for the formation of NPs based on the spectral changes of metal ions.…”

“…[3] In previous reports, formation of NPs was accomplished using pulses with rather high energy of 0.3-0.5 milli-Joules/pulse with a duration of 30-130 fs. [4,6,7,[9][10][11][12][13][14] This sub-milli-Joule laser irradiation condition is known as the strong optical breakdown (SOB) condition. [5] An optical breakdown (OB) of the medium generates vigorous plasma conditions with bubble formation.…”

Applications of Shaped Femtosecond near-IR Laser Irradiation in the Generation of Metal Nanoparticles

“…Reduction of aqueous [AuCl 4 ] -during fs laser irradiation has been attributed to the reactive reducing radicals such as (H . ) and solvated free electrons (e aq -) produced from dissociation and ionization of the water that occurs in the region of the laser focus [7,8].…”