Exploring the Cobalt-Histidine Complex for Wide-Ranging Colorimetric O Detection.

Developing a robust, cost-effective, and user-friendly sensor for monitoring molecular oxygen (O) 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) complex, a bioinspired model of O-carrying metalloproteins, for rapid and reliable sensing of O from 0 to 100% saturation levels under realistic conditions. We have established two distinct colorimetric O 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) 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 sensing, leading to practical and straightforward solutions. This metal-amino acid complex's broad-spectrum sensing of O has widened the scope of bioinspired model complexes for divergent applications in industrial sectors.