Nanogold Array Sensors Leveraging Interaction-Sensitive UV Shifts for Portable Speciation of Phosphorus in Water

The sensitive and cost-effective identification of diverse phosphorus species, particularly organophosphorus compounds, is crucial for advanced wastewater treatment. Herein, we developed a colorimetric sensor array based on gold nanoparticles (nano-Au) that utilizes UV–vis spectral shifts induced by interactions with phosphorus species. Four molecular modifiers, i.e., cysteamine (CS), neodymium (Nd), cetyltrimethylammonium bromide (CTAB), and tributylhexadecylphosphonium bromide (THPB), were strategically incorporated into the nano-Au receptors to generate distinct response patterns via coordination, hydrophobic interactions, and electrostatic attractions. These optical “fingerprints” were deciphered using pattern recognition techniques. The sensor array successfully differentiated 11 phosphorus species (including organophosphonic acids, organophosphate esters, and inorganic phosphates, with 100% classification accuracy for the 11 target species within the tested training set) at concentrations ranging from 1.0 to 50 mg/L, both individually and in mixtures; it exhibits high sensitivity, with detection limits ranging from 0.17 to 0.94 mg/L for the 11 phosphorus species. The sensor array demonstrated robust anti-interference capability, achieving recoveries between 90%–96% in both simulated and real water matrices. Notably, the sensor enabled in situ determination of residual phosphorus concentrations in actual phosphorus adsorption treatments, and the yielded results are highly consistent with standard spectroscopic measurements, highlighting its practical potential for simplifying environmental monitoring and water quality analysis.