Abstract
Microplastic pollution represents a severe environmental and public health risk, contaminating oceans, freshwater, and drinking water. Despite awareness, scalable detection is limited by current methods, such as Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, which are costly, slow, and require specialized infrastructure. There is an urgent need for accessible, interference-resistant technologies capable of both rapid field detection and laboratory quantification. This project introduces a dual-dye optical sensing system leveraging Thermally Activated Delayed Fluorescence (TADF) and Förster Resonance Energy Transfer (FRET). The mechanism uses a luminescence-based logic-gate approach where two structurally similar 1,8-naphthalimide dyes undergo environment-dependent interactions. By combining FRET, TADF, and distinct emission profiles, the system ensures high specificity and robustness against environmental interferences.
The project develops a dual-mode strategy integrating smartphone-based time-gated luminescence for field use and laboratory-based quantitative spectroscopy for forensic analysis. The smartphone method enables real-time, on-site detection by capturing long-lived TADF emission through time-gated imaging. This builds on research by the MIT collaborator, who demonstrated that CMOS rolling shutter mechanisms in commercial smartphones can achieve sensitivity comparable to laboratory-grade instrumentation. Simultaneously, forensic quantification will employ steady-state and time-resolved spectroscopy, correlating emission shifts, luminescence lifetimes, and FRET efficiency to quantify concentrations and differentiate polymer types. These methods will be benchmarked against Raman, FTIR, and optical microscopy to ensure high accuracy, reproducibility, and regulatory applicability.
The project integrates the complementary expertise of the PI and co-PI. The PI recently demonstrated that these dyes exhibit FRET interactions when encapsulated in polymeric matrices, enhancing triplet formation and TADF emission. The MIT collaborator pioneered smartphone-based time-gated detection for portable sensing. Together, they will optimize detection wavelengths, time-gating conditions, dye concentrations, and polymer interactions across diverse aqueous conditions. The system will be validated using environmental samples from rivers, oceans, industrial effluents, and tap water. Integrating pre-concentration methods will ensure detection at environmentally relevant concentrations, contributing to scalable workflows for monitoring and regulatory enforcement.
Aligned with LAQV-REQUIMTE’s Sustainable Chemistry line, this work supports UN Sustainable Development Goals 12 and 14. By merging green chemistry with accessible detection, the project provides a low-cost solution bridging the gap between innovation and application. Requested funding will support proof-of-concept validation, a dedicated researcher, and the MIT collaboration. By proving the feasibility of a portable, interference-resistant system, this project lays the groundwork for commercialization and large-scale adoption.
PT PIs
João Avo, Associação para a Inovação e Desenvolvimento da FCT (NOVA.ID.FCT)
MIT PIs
Timothy M. Swager, Department of Chemistry, MIT