Plasmon-Mediated Catalytic Oxidation of sec-Phenethyl and Benzyl Alcohols

Surface plasmon excitation of aqueous colloidal gold nanoparticles with visible light in the presence of H₂O₂ led to rapid and selective oxidation of sec-phenethyl and benzyl alcohols to acetophenone and benzaldehyde, respectively. Laser drop, light emitting diode, and microwave irradiation have been used as energy sources. Interestingly, sec-phenethyl alcohol conversion was calculated to be 95% in 20 min when monochromatic 530 nm LEDs were used, being as good or better yield than the corresponding laser and microwave techniques. These results demonstrate the versatility of this inexpensive arrangement. Further attention was placed on the possible mechanism for Au nanoparticle plasmon-mediated alcohol oxidations in the presence of H₂O₂. We propose electron transfer with the nanoparticle surface, as well as the participation of peroxyl and ketyl free radicals as fundamental steps in the reaction pathway.