A large number of poisonous chemicals, such as PFOA, PFOS, and mercury ions, are mandated to be controlled in drinking water with their permissible concentrations below parts-per-billion (ppb). In this context, an increase in the concentration is a necessary step preceding detection. Apart from their selective absorption ability, metal-organic frameworks (MOFs) have an extraordinarily large internal surface area, which can be used for extraction. In terms of detection methods, Raman spectroscopy is a powerful non-invasive chemical detection technology characterized by portability, accuracy, and speed. In addition, concentrations in the ppb range and below can be detected with surface-enhanced Raman scattering (SERS). As a result, a combination of the SERS and extraction method may allow the detectable concentration limit in the parts-per-trillion (ppt) range. This research is devoted to the design of Ag@MIL-53 core-shell nanostructures for detection of chemicals in ppt level. The bulk absorption ability of MIL-53 to PFTeDA in water is determined, where the absorption saturation time of MIL-53 is found to be around 43 min. In addition, the Raman intensity of PFTeDA with Ag@MIL-53 is enhanced by more than a factor of 10x over pure Ag substrate. Furthermore, we have achieved a detectable concentration of 1 ppm for PFTeDA (Raman peak of 731 cm-1) using Ag@MIL-53. We plan to use filter paper as the substrate for suction filtration to increase the concentration of target chemicals on the SERS substrate and to obtain further reduction on detectable concentrations.
Project ended: 08/19/2021