Nanogold dispersed into glass and polymer matrices and its application as passive sampler for gaseous elemental mercury

Abstract

Due to the global distribution of gaseous mercury in the atmosphere and the serious consequences that this pollutant can cause to human health, reliable means of measuring its concentrations and distribution in the atmosphere are necessary. Passive samplers, designed to be inexpensive, portable, simple to operate and without the need of using electricity to operate, can provide an efficient alternative as compared to current active sampling techniques. Efficient passive samplers are a necessity to be applied in mercury sampling indoor and in field applications. In this sense, the main objective of the project is to develop gold nanocomposites dispersed in glass and polymer matrix for application as passive samplers for gaseous elemental mercury (GEM). For this purpose, it is intended to prepare the nanocomposites from the direct reduction of gold in small discs of the commercial porous Varapor 100® glass. As a polymer matrix, polydimethylsiloxane (PDMS) will be used, which will be prepared in the form of small solid pieces in the laboratory for subsequent deposition of gold. Both materials will be immersed in solutions containing ions Au3+, and then carried out the reduction step using sodium borohydride solution. The samples will be characterized by Ultraviolet-visible spectroscopy, atomic force microscopy, scanning and transmission electron microscopy. These analyzes will allow to obtain information about the formation of nanogold, elemental composition, dispersion of gold in the matrices, besides the size and crystallinity of the nanostructures. Laboratory tests will be performed, exposing the samples to controlled amounts of GEM, and afterwards, testes will be carried out exposing the samplers to the external environment. The retained mercury in the samplers will be quantified by doing measurements with a mercury direct analyzer (DMA), allowing to estimate the degree of GEM retention per sample and the limit of detection. Nanogold when exposed to mercury, will form Au-Hg amalgam. This may change the color of the samplers, which may be an important visual indicator of GEM retention. The samplers will be photographed and be analyzed with a portable color meter for colorimetric analysis. Crossing the results of quantification of GEM and color, in the case of a good correlation, it will be possible to construct a calibration curve, which will allow optimizing the application of the samplers for future field applications. (AU)