Polymer coatings for sensitive analysis of colloidal silica nanoparticles in water

A new analytical approach has been developed for the sensitive detection of trace nanomaterials in water using silica as model inorganic nanoparticles. Our novel approach is based on coating of the nanoparticles with a polymer to make them larger in size for better ultraviolet (UV) light absorption. These polymer-coated nanoparticles can be separated from the monomer and polymer by capillary electrophoresis (CE) due to differences in their ionic charge, size, and surface functionality. Controlled polymerization of 2-hydroxypropyl methacrylate (HPMA) on silica nanoparticles increased their UV detection sensitivity by 5-7-fold. A second coating with polydopamine produced an extra 2-fold increase of the UV detection sensitivity. With both polyhydroxypropyl methacrylate and polydopamine coatings, a significant total enhancement of 10-14-fold in detection sensitivity was attained. Alternatively, addition of bisphenol A or polyvinyl alcohol to the HPMA polymerization mixture resulted in 9-10-fold increase of SiO2 detection sensitivity due to additional absorption of the UV detector light