Visualization and Transport of Quantum Dot Nanomaterials in Porous Media

Abstract

This paper presents our research on the visualization and transport phenomena of quantum dot nanomaterials in porous media. It includes the development of a non-intrusive, high spatial and temporal resolution method to visualize transport and measure quantum dot nanomaterials concentration in porous media, allowing to characterize the mechanisms that control the transport, or lack of mobility, of engineered nanomaterials — quantum dots — in subsurface complex and heterogeneous environment. The visualization technique used to explore the transport of quantum dot nanomaterials is a toolbox that allows to characterize a wide range of flow and transport phenomena due to mesoscale heterogeneities. The characterization of these flow and transport phenomena includes the visualization and/or quantification of flow, fluid content and nanoparticle concentrations. The visualization technique selected to investigate transport of quantum dot nanomaterials in two-dimensional variably saturated porous media is a non-intrusive method based on fluorescence resulting from the quantum dots optical properties. The visualization procedure consists of exciting fluorescent quantum dots in porous media by using a UV light located in the front of the chamber and in characterizing the water content with the light transmitted through the porous media by using light emitted devices (LEDs) as a light source placed in the back of the chamber. The visualization, calibration and image analysis are performed using an image software. Experiments investigating quantum dot nanomaterials transport in unsaturated zone demonstrates the effects of preferential flow and gas-water interfaces on the transport of quantum dot nanomaterials through the vadose zone.