科研之友
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摘要
We report the UV-light-induced formation of water aerosol/droplets in air based on laser-light scattering measurements, differential mobility analyses and cavity ring-down laser spectroscopy (CRDS), and propose a mechanism. It was shown that UV-light (185 nm) irradiation of air within a soap bubble rapidly produced water droplets under supersaturated conditions. Multiple UV irradiation cycles were demonstrated to increase particle sizes in a controlled reaction chamber. We propose that the reaction mechanism is initiated by oxygen (O-2) photodissociation and ozone (O-3) formation and further photodissociation of O-3 leads to sequential dark reactions, generating hydrogen peroxide (H2O2) as a hygroscopic stable product. Exciting excess O-3 in wet air with mid-UV radiations (254 tun) was also demonstrated to produce water particles, indicating that this series of reactions can be started at an intermediate stage using a longer wavelength of UV light. For the first time, it was demonstrated that H2O2 in air is a precursor of the initial nucleation of water with two different aerosol formation schemes at 263 K: a) from a mixture of H2O2 and water vapor in dark and b) from a mixture of 03 and water vapor by mid-UV (266 nm) light irradiation. These results indicate that H2O2 can capture water molecules and form water particles.
- 出版日期2014-5-15
