Nanoparticles in aqueous environment: electrochemical, nanogravimetric, STM and AFM studies
In order to evaluate potential exposure of ecosystems to engineered as well as natural aquatic colloids and nanoparticles (NPs), methods must be available for measuring spatial and temporal trends in the concentration, size distribution, metal content of these NPs and their interaction in the different environmental compartments. Here we propose an electrochemical and piezo-nanogravimetric study of metal, metal-oxides and chalcogenide nanoparticles in combination with sophisticated methods such as atomic force and scanning tunneling microscopy, ICPMS and separation techniques such as ultrafiltration and Diffusion Gradients in Thin Films. We offer electrochemistry due to its simplicity and prompt response, low cost and relatively high sensitivity and selectivity, as alternative analytical technique for characterization and quantification of different here preferably chalcogenide based NPs. Voltammetric measurements in combination with electrochemical nanogravimetric measurements (EQCM) and Scaning Tunneling Microscopy (STM) as well as Atomic Force Microscopy (AFM) on different electrode surfaces (Hg and Au electrode) will give more details and information related to attachment, adsorption, deposition and interaction between selected NPs and functionalized electrode surfaces. By following changes in the resonance frequency which will be in the same time accompanied with some changes in current produced during oxido-reduction processes it is possible to characterize physico-chemical properties and to calculate the mass of NPs deposited on the Au surface over a broad range of environmentally relevant solution chemistries including variation in ionic strength, composition, pH, ion valence, particle sizes. The particle deposition mechanisms will be studied in relation with variations of particle charge, particle sizes and applied electrode potential all with the aim to improve and develop new analytical method for fast, selective qualitative and quantitative NPs characterization in natural waters. Method which development is planned in the laboratory will be tested and intercalibrated on the field. We expect that understanding of the environmental impact of engineered NPs will significantly benefit from the lessons learnt with natural NPs. As study sites we offer four types of samples: 1) oxic seawater samples from North Adriatic as the source of natural aquatic colloids and NPs mainly produced during intensive phytoplankton bloom and occasionally appearance of mucous aggregates; 2) hypoxic/anoxic samples of stratified seawater Lake Rogoznica on the eastern Adriatic coast enriched by FeS; 3) industrial waste waters including sea-marinas of engineered NPs; 4) wet deposition from atmosphere. We expect that research proposed here would contribute to further studies and applications of NPs in chemical/biochemical sensing.