Synthesis of Silver Nanoparticles Using CO2-Laser Heated Vaporization/Condensation

 

Pamela Dopart and Brian M. Tissue

 

Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg VA 20461-0212

 

This paper describes conditions for laser-heated, gas-phase condensation of silver metal nanoparticles. Pressed pellets of silver salts and silver salts mixed with Y2O3 or MgO were used as vaporization targets. Vaporization of silver salts directly was limited in duration due to reduction of the targets to silver metal. The mixed targets did not undergo reduction and produced films of silver black. The highest yields attained were 59.2 mg over 90 minutes for the mixed targets and 33 mg over 7 minutes for the silver salts. The films of nanoparticles were characterization by SEM, UV-Vis absorption of the surface plasmon resonance (SPR) region, and FTIR spectroscopy. SEM of the films showed the particle size to be 30-50 nm with a dense film morphology when prepared at low chamber pressures (<1 Torr) and a porous fractal morphology for >1 Torr. Annealing the nanoparticles changed the appearance of the film from black to brown-orange with a large increase in the SPR absorption band.

 


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SEM images of mixed target nanoparticles after vaporization under pressures of (A) 0.10, (B) 0.50, and (C) 1 Torr N2.



UV-vis absorption spectra of SPR band of gas-phase-deposited Ag nanoparticles after annealing at 400oC.