RIFF began with fundamental investigations into the fluorescence behaviour of faecal indicator pigments (FIPs) and their interactions with different zinc salts. These studies established the anion-dependent photophysical understanding required to maximize fluorescence response of FIP-Zn2+ complexes and provided the scientific foundation for developing highly sensitive detection methods.
Building on these findings, a hybrid glass/quartz-fibre test-strip with an engineered detection zone was developed and integrated into a compact smartphone-based optical sensing platform using 3D printing technology. The portable device incorporates a light-emitting diode 480 nm, optical filters, lenses, a diffuser, a custom-designed 3D-printed housing, and a smartphone camera for fluorescence detection. The platform enables rapid analysis within one minute using only a small sample volume, making it suitable for field applications.
During the project, the original membrane enrichment strategy evolved into a more practical sensing approach based on hybrid test-strips and integrated opto-fluidic technologies. A miniaturized opto-fluidic sensing platform was developed by combining optimized 3D-printed opto-fluidic chips with optical detection components and automated fluid handling. The opto-fluidic system enables continuous and controlled flow monitoring with improved sensitivity, selectivity, low reagent consumption, and efficient separation technology for FIPs. Both sensing platforms were successfully validated using environmental water samples, including wastewater treatment plant effluents and river water samples, demonstrating reliable performance under real-world conditions.
The project RIFF generated significant scientific and technological outputs, including a published international PCT patent application (PCT/EP2024/075029) protecting the developed sensing technology, a peer-reviewed open-access publication in ACS Sensors, additional manuscripts currently under preparation, presentations at major international conferences, public engagement activities, and extensive dissemination through institutional press releases, scientific media, and online platforms. These activities have substantially increased the visibility and potential future exploitation of the project results.
