White Light Assisted Photosensitized Synthesis of Ag Nanoparticles: Excited-State Hydrogen Bonding Roles

Ag nanoparticles (NPs) with different surface morphologies can be synthesized through white light irradiation of photochemically prepared Ag nanoseeds within 20 min. The fundamental photophysical and photochemical properties of benzil in deaerated solvents at room temperature are investigated through analyzing nanosecond absorption spectra. In ethanol, after the single photon excitation of benzil by 355 nm nanosecond laser pulses, one kind of reactive intermediate with a long-lived lifetime of 375.83 ± 93.70 μs is generated and capable of reducing the coexisted Ag + to generate Ag nanoseeds with their diameters in the range from 3 to 12 nm. Theoretical calculations indicate that the reactive intermediate is benzil-ethanol hydrogen-bonded complex biradical (ben-eth biradical). Furthermore, the excited-state hydrogen bonding dynamics and its influence on the photophysical and photochemical properties are discussed. White light irradiation under air can make these Ag nanoseeds grow in size with a speed of 10 nm/min and have unique morphologies. In particularly, the nanowhisker covered Ag NPs can be synthesized and possess a unique narrow optical absorption peak at 325 nm. This work not only provides insights into the mechanisms of photosensitized synthesis of Ag nanoseeds but also emphasizes the utilization of white light as a convenient and efficient tool to tailor morphologies of Ag NPs.