Synthesis and catalytic reactions of nanoparticles formed by electrospray ionization of coinage metals

Noble metals can be ionized by electrochemical corrosion and transported by electrospray ionization. Mass spectrometry (MS) showed solvated metal ions as the main ionic constituent of the sprayed droplets. Collection of the electrospray plume on a surface yielded noble metal nanoparticles (NPs) under ambient conditions. The NPs were characterized by several techniques. Under typical conditions, capped-nanoparticle sizes averaged 2.2 nm for gold and 6.5 nm for silver. The gold nanoparticles showed high catalytic activity in the reduction of p-nitrophenol by NaBH₄. Efficient catalysis was also observed by simply directing the spray of solvated Au⁺ onto the surface of an aqueous p-nitrophenol/NaBH₄ mixture. Organometallic ions were generated by spiking ligands into the spray solvent: for example, Cu^I bipyridine cations dominated the spray during Cu electrocorrosion in acetonitrile containing bipyridine. This organometallic reagent was shown to be effective in the radical polymerization of styrene. High catalytic activity: Copper, silver, and gold solids are ionized to the +1 oxidation state ions by electrospray in acetonitrile (ACN) as an anhydrous organic solvent. Collection of the solvated ions leads to formation of nanoparticles that serve as catalysts for bulk reactions, for example the reduction of p-nitrophenol by NaBH ₄.