Edward PC Lai

Silica (SiO2) and titanium dioxide (TiO2) nanoparticles are widely used in agricultural, cosmetic and medical products. However, sampling devices are not readily available to help environmental scientists assess the levels of these nanoparticles that have been emitted and released to air by various sources. In this work, airborne particulates were bubbled through water containing either a surfactant (sodium dodecyl sulfate) or chemical reagent (ammonium molybdate + ascorbic acid) and transferred into an aqueous suspension. Changes in the UV-visible spectrum were measured for different concentrations of silica (1 to 5 mg/ml) and titanium dioxide (1 to 3 mg/ml) nanoparticles at a fixed concentration of sodium dodecyl sulphate (4 mg/ml) or ammonium molybdate/ ascorbic acid (chemical reagent). Capillary electrophoresis with UV detection at 190 nm verified the attraction between titanium dioxide and dodecyl sulfate anions. A strong peak of UV light absorption at 311 nm was observed for titanium dioxide nanoparticles added to the reagent. Silica nanoparticles did not react with the reagent, even though the absorption peak at 280 nm varied linearly with their concentration. A UV absorption peak at 328 nm verified the formation of a complex between the reagent and dissolved silicate. Advantages of the sampling device include simple construction, low surfactant or chemical reagent cost, and high collection efficiency.

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