Measuring dissolved oxygen in pond water with high-resolution by optical gas sensor

Dissolved Oxygen (DO), the oxygen molecule present in water, is essential for the survival of aquatic organisms, as fluctuations in its levels lead to stress, suffocation, or death, underscoring the importance of monitoring. Among the various DO monitoring methods such as titration, electrochemical, and photometric sensing, photoluminescence-based optical sensing stands out for its stability, fast response, and high sensitivity. Despite advancements, there remains a strong demand for a high-resolution optical DO sensor with enhanced performance. This study seeks to address these limitations by developing a highly sensitive, high-resolution optical DO sensor through exploiting a nanoporous Anodic Aluminum Oxide (AAO) membrane. The sensor is developed using Platinum(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) as the indicator molecule embedded in a sol-gel matrix, which is spin-coated onto a 200 nm pore-sized AAO membrane, with glass substrate included for comparison. After initial optimization, the sensor is tested for DO sensing, showing a strong DO response (I0/I, where I0 and I represent phosphorescence intensity in water without and with dissolved oxygen, respectively) values of 6.5 on glass, and 26.2 on the AAO membrane. These results demonstrate the sensor's capability for detecting subtle variations in DO concentration, underscoring its potential for advanced water quality and ecological studies.