Exploring the Cobalt–Histidine Complex for Wide-Ranging Colorimetric O(2) Detection

[Image: see text] Developing a robust, cost-effective, and user-friendly sensor for monitoring molecular oxygen (O(2)) ranging from a minute to a medically relevant level (85–100%) in a stream of flowing breathable gas is vital in various industrial domains. Here, we report an innovative application of the cobalt(l-histidine)(2) complex, a bioinspired model of O(2)-carrying metalloproteins, for rapid and reliable sensing of O(2) from 0 to 100% saturation levels under realistic conditions. We have established two distinct colorimetric O(2) detection techniques, which can be executed with the use of a common smartphone camera and readily available color-detecting software. A series of spectroscopic experiments were performed to demonstrate the molecular-level alteration in cobalt(l-histidine)(2) following its exposure to oxygen, leading to an exclusive pink-to-brown color change. Therefore, this study establishes a template for designing bioinspired molecular complexes for O(2) sensing, leading to practical and straightforward solutions. This metal-amino acid complex’s broad-spectrum sensing of O(2) has widened the scope of bioinspired model complexes for divergent applications in industrial sectors.