Laser-induced growth and reformation of gold and silver nanoparticles
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The sizes, shapes, and growth rates of gold and silver nanoparticles stabilized with polyvinylpyrrolidone in water can be controlled by using picosecond laser pulses. The nucleation of small metal clusters formed with NaBH4 addition to produce nanoparticles takes two months with aging but 30 min with laser irradiation. Laser pulses can also induce nanoparticles to have narrow size and shape distribution or to undergo aggregation into much larger particles. The latter process is more likely found when the metal is silver or the irradiation wavelength is short. Laser-induced growth and shape transformation processes are explained in terms of BH4 − depletion, metal fusion, and electron ejection followed by disintegration.
KeywordsNucleation Optical fabrication Picosecond pulses Polyvinylpyrrolidone Shape transformation Colloids
This work was supported by the Nano R&D Program of the Korea Science and Engineering Foundation (KOSEF) funded by the Ministry of Education, Science, and Technology (M10703000871–07M0300–87110). We are also thankful to the Center for Space-Time Molecular Dynamics of KOSEF (R11–2007–012–01002–0) for partial support while S.J.K. acknowledges the BK21 Scholarship as well.
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