Study of indium tin oxide thin film as fluorescence enhancers for optical biosensing in water quality analysis

This study presents an optical investigation on Indium Tin Oxide (ITO) thin film used as enhancers in an optoelectronic device designed for the detection of emerging micro-contaminants (EMCs) in water, known to cause risks to human health and environment. The accurate detection of these substances is crucial for mitigating health issues and pollution, encouraging the development of numerous water quality analysis devices in recent decades. Lab-on-a-chip (LOC) systems offer a promising solution for maintaining low limits of detection (LoD), high sensitivity and real-time response, achieving compactness, cost-effectiveness and ease of fabrication. The focus of this research lies in the development of an integrated optoelectronic device based on an evanescent waveguide structure immersed in water, which relies on fluorescence to detect micro-contaminants in water solutions. Specifically, to enhance the performances, a study based on the introduction of a transparent conductive oxide layer onto a polymer waveguide built on a glass substrate is presented. The assessment was conducted using a 540 nm light excitation source due to its compatibility with a broad spectrum of fluorophores. Results demonstrate a significant improvement in waveguide-layer coupling efficiency with an ITO thickness of 125 nm. These findings offer a promising support for the use of such devices in high-performance lab-on-a-chip systems for water quality monitoring.