Fluorescence Sensor Setup Design and Optimization for Water Quality

Water supports ecosystems that provide habitats for various plant and animal species. Without regular monitoring, contamination may go unnoticed. Water sensors for physicochemical parameters are commercially available, but contaminant sensors still encounter obstacles. This paper explores the feasibility of an optical sensor platform based on fluorescence targeting water quality. This was designed to prevent photobleaching and other sources of fluorescence signal loss and has self-referencing capabilities. This paper details the optical setup and its optimization, including a 450 nm laser source with a measured variation of 0.55% and a fluorophore emitting at 511 nm. The stability test of the whole setup showed 10.8% variation, which implies that a possible analyte response needs to be above 10.8% to be detected. In this paper, we show how to reduce this threshold to 1%. This was possible by combining a duplicated setup approach with the use of an automatic shutter, reducing the exposure time of the fluorophore from 5 to 1 s. Furthermore, a probe tip development that could allow the direct integration of a selective layer for a target contaminant is demonstrated. The presented optical sensor system can serve as a water quality fluorescence-based sensor.