Interface Reaction for the Self-Assembly of Silver Nanocrystalst.pdfVIP

Interface Reaction for the Self-Assembly of Silver Nanocrystals under Microwave-Assisted Solvothermal Conditions Feng Gao, Qingyi Lu, and Sridhar Komarneni* Materials Research Institute, The PennsylVania State UniVersity, UniVersity Park, PennsylVania 16802 ReceiVed August 12, 2004. ReVised Manuscript ReceiVed December 4, 2004 We propose a one-step interface reaction for the direct synthesis of hexagonally arranged spherical silver nanoparticles under microwave-assisted solvothermal conditions without the requirement of the presynthesis of uniform silver nanoparticles or special precursors and the technique of size-selective precipitation. The ratio between ethylene glycol and dodecylthiol shows its effect on the nucleation and growth of silver and thus the morphology and arrangement of the obtained nanoparticles. At a low volume ratio, nanoparticles with a rectangular shape arranged in orthogonal arrays could be observed. This simple method has its generality, and by easily substituting thiourea aqueous solution for ethylene glycol, silver sulfide superlattices of nanoparticles could be synthesized. Introduction Fine metal particles in the nanometer range have attracted considerable interest and have found numerous applications in various fields such as catalysis; optical, microelectronic, and magnetic devices; and biological diagnostic probes due to their conspicuous physical-chemical properties that differ markedly from those of bulk materials. 1-4 Especially for noble metal nanoparticles such as silver (Ag), the interest is mostly focused on their catalytic applications because these nanoparticles can serve as a bridge between homogeneous and heterogeneous catalysis and bring new opportunities for catalysis. 5,6 Until now, various methods have been utilized for the preparation of silver nanoparticles, such as chemical reduction using a series of chemical reductants including NaBH4, N2H4, NH2OH, ethanol, ethylene glycol, and N,N- dimethyformamide (DMF), 7-11 aero