Nanogel for Selective Recognition of Nanoparticles in Water Samples

Abstract

Nanoparticles (NPs) represent emerging pollutants that still pose analytical challenges for their detection in environmentally relevant samples due to their extremely low concentrations, high colloidal background, and the need to perform speciation analysis. They are also one of the interfering matrices during the analysis of metal ions and contaminants in water samples. Currently, conventional analytical techniques such as Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) are used for the detection of NPs, but such techniques require bulky instrumentation and are difficult to be automated for online analysis. In this study, we aim to develop a nanoparticle-imprinted hydrogel (NPIH, NANOGEL) to detect and capture NPs in water samples. The principle of the Nanogel originates from the well-known concept of molecularly imprinted polymers (MIPs). Cadmium sulfide/Selenide/Zinc sulfide core/shell quantum dots (QDs) were used as the template NP, creating specific pore cavities in the Nanogel that can selectively bind to certain analytes. Quantification of NPs detected in water samples was then made possible by transducing this selective detection process into an analytical signal using a quartz crystal microbalance (QCM). The Nanogel was shown to demonstrate good repeatability, reproducibility, and stability in terms of its performance. The high selectivity of the Nanogel was determined to be attributed to the size of cavities and their surface characteristics. Ionic interference was present and, heavy metal cations showed an affinity for the NANOGEL synthesized; however, they were demonstrated to be minimized by the selection of porogenic solvents during the synthesis of NANOGEL. We believe that the Nanogel would provide a highly selective and sensitive approach for the detection of NPs in aqueous samples and the removal of NPs from contaminated water resources. It will serve useful in environmental applications.