Photo-chemical synthesis and deposition of noble metal nanoparticles

Highly dispersed nanoparticles of transition and noble metals are utilized for hydrocarbon reactions and rearrangements important to the chemical industry. The need to obtain 1 to 3 nm particles with narrow size distributions has prompted the development of alternative processing methods. In this paper, a novel, dry method to synthesize nanoparticles from a frozen salt solution is reported. Pd nanoparticles were synthesized by photo-chemical decomposition of palladium acetate (PdAc) within a host matrix of chloroform using an excimer laser operating at 248 nm. Frozen composite targets were ablated at fluences ranging from 0.25 J/cm² to 0.75 J/cm² at a processing pressure of 10 mTorr. The ejected nanoparticles were deposited on continuous carbon coated and lacey carbon transmission electron microscopy (TEM) grids at ambient temperature. Characterization was performed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDXS). High-resolution TEM analysis showed definitive evidence that the size distributions of the nanoparticles were narrow, exhibiting mean diameters ranging from 2.15 nm to 2.62 nm. PACS 81.15.Fg; 68.37.Lp; 81.07.Wx; 81.07.Bc; 81.10.Dn