Photoluminescence Decay Lifetime Study of Hydrothermally Synthesized Highly Porous Ruthenium–Silica Composite for Optical Dissolved Oxygen Sensing Application

Pore size and surface area of photoluminescence (PL)-based transition metal composites play crucial roles in facilitating oxygen diffusion, thereby enhancing the response and sensitivity of optical dissolved oxygen (DO) sensors. In this study, we successfully applied the hydrothermal method to synthesize a porous ruthenium composite embedded in a silica matrix, demonstrating its effectiveness for optical DO sensing applications. The ruthenium–silica (Ru–Si) composites were synthesized using Ru(bpy)32+ and tetraethyl orthosilicate (TEOS) as precursors, with reaction temperatures ranging from 120 °C to 200 °C over a fixed duration of 4 h. The structural, morphological, and compositional characterization techniques confirmed the successful synthesis and evaluated the porosity, surface features, and chemical structure of the resulting composites. The optimized Ru–Si composite exhibited the highest porosity, characterized by a specific surface area of 996.78 m2 g– 1, and exhibited the highest decay lifetime of 8.14 μs in deionized (DI) water, compared to other composites. Importantly, we demonstrate an excellent linear response of the synthesized Ru–Si composite to DO concentrations ranging from 2.58 to 11.16 mg L–1, with a Stern–Volmer constant of 0.12. Furthermore, a density functional theory study was conducted to investigate the electronic transitions and to elucidate the oxygen quenching mechanism of the excited Ru composite with molecular oxygen. The calculated photophysical parameters of the composite show good agreement with the experimental results. Preliminary results suggest that the synthesized Ru–Si with high pore size and surface area could be an efficient and effective composite for use in DO sensing applications.