Flexible point-of-use phosphate electrochemical sensors based on electrodeposited molybdenum oxide

To enable <i>in situ</i> phosphate monitoring for healthcare and environmental sustainability, this work demonstrates an electrochemical sensor based on electrodeposited mixed-valence molybdenum oxide (MoO_<i>x</i>) for selective phosphate sensing in complex aqueous media. The MoO_<i>x</i> film induces strong, specific detection through coordination between Mo centers and phosphate anions, generating well-defined redox signals under square wave voltammetry. The sensor exhibits a broad linear dynamic range between 10-1000 μM, a sensitive detection limit of 8 μM, and high specificity against competing anions including Cl^-, SO₄^2-, NO₃^-, CO₃^2-, and SiO₃^2-. The sensors accurately measure phosphate levels in artificial saliva and influent wastewater field samples, with results validated to match those of standard molybdenum blue assays. The compact, flexible system achieves stable performance across varying ionic strengths, proving its robustness as a low-cost point-of-use monitoring platform for phosphate.