Green synthesis of gold nanoparticles of different sizes and shapes using agar–agar water solution and femtosecond pulse laser irradiation

Mechanism of Improved Au Nanoparticle Size Distributions Using Simultaneous Spatial and Temporal Focusing for Femtosecond Laser Irradiation of Aqueous KAuCl4

“…Femtosecond (fs) laser irradiation of aqueous [AuCl 4 ] − in the presence of chemical surfactants has recently emerged as a promising “green” method for synthesizing size-tunable AuNPs, typically by varying the concentration of the added surfactant in solution during irradiation. − Nanoparticle formation in these experiments is generally attributed to the reduction of [AuCl 4 ] − to Au(0) ,, by reactive species such as hydrogen radical (H • ) and solvated free electrons (e aq – ) generated through optical breakdown of water. , Under these conditions, the quantity of reactive water species produced during laser irradiation determines the reagent concentration. Laser filamentation is an important aspect of femtosecond laser propagation that strongly influences the intensity in the sample and therefore the reagent concentration.…”

“…White light generation (a result of filamentation) has been reported to enhance AuNP fragmentation through linear absorption of the radiation via the surface plasmon resonance (SPR), − thus reducing the average particle size distribution of AuNPs in solution. Also, stirring of the solution is typically omitted in femtosecond laser AuNP synthesis, ,− and circulation of the solution occurs only by diffusion and cavitation bubble-induced currents. The dynamics of laser produced cavitation bubbles has been shown to be highly sensitive to the shape of the laser plasma, which in turn is strongly influenced by filamentation.…”

Gold Nanoparticle Synthesis Using Spatially and Temporally Shaped Femtosecond Laser Pulses: Post-Irradiation Auto-Reduction of Aqueous [AuCl4]−

“…Femtosecond (fs) laser irradiation of aqueous [AuCl 4 ] − in the presence of a variety of surfactants in solution has been employed to generate and stabilize Au NPs. − Reduction of aqueous [AuCl 4 ] − using high-energy, near-infrared fs laser irradiation has been attributed to reactions of radicals (H•) and solvated free electrons (e aq – ) produced from homolytic dissociation of water and ionization in the plasma that occurs in the region of the laser focus. ,, The mechanism for reduction of aqueous [AuCl 4 ] − is based on the production of the reducing agents from water, in distinct contrast with UV photolysis where reduction of [AuCl 4 ] − is accomplished by direct homolysis of Au–Cl bonds. , …”

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

“…Plasmonic nanoparticles such as gold and silver are among the most extensively studied nanomaterials and thus serve as a benchmark to evaluate general methodologies for formation and stabilization of metal nanoparticles. Femtosecond (fs) laser irradiation of aqueous [AuCl 4 ] -in the presence of a variety of surfactants in solution has been shown to generate and stabilize Au NPs [4][5][6]. Reduction of aqueous [AuCl 4 ] -during fs laser irradiation has been attributed to the reactive reducing radicals such as (H . )…”