Expanding the Applicability of Raman Spectroscopy for Monitoring Photocatalytic Degradation

Compared to other types of wastewater pollutants, dangerous chemical compounds such as pharmaceuticals, pesticides, and herbicides are difficult to remove and consequently being detected (at least in part because detection limits have decreased) in drinking water at increasing concentrations. Photocatalytic degradation degrades harmful compounds to innocuous end products using energy from light. Although it is effective and cost-efficient, the underlying chemical mechanisms are not understood well enough to ensure that dangerous intermediate products are not formed during the degradation process. Raman spectroscopy can be used to analyze photocatalytic degradation reactions in real time, identifying intermediate products based on spectral features. Due to fast data acquisition, Raman studies can identify those intermediate products which are short-lived and could be missed by slower conventional methods. In the current research, colloidal gold nanoparticles were introduced to increase sensitivity via surface-enhanced Raman spectroscopy (SERS), and later modified to maintain signal intensity over a longer period of time. Additionally, an internal standard was introduced for ratiometric determination of analyte concentration. These procedural modifications serve to expand the applicability of Raman spectroscopy for in-situ reaction monitoring