Surface-enhanced Raman spectroscopy investigation of PO3- (4) to Ag/Al2O3 nanopatterned substrates binding and its dynamics for sensitive detection of phosphate in water

We provide fast and sensitive detection of phosphate dissolved in water using Raman spectroscopy. To this end, phosphate-scavenging planar core/shell surface-enhanced Raman spectroscopy (SERS) probes consisting of Al2O3- capped Ag nanopatterned sapphire substrate were prepared and optimized. Thanks to scavenging, the probes provide enhancement sufficient to readily detect phosphate at levels occurring in water sources. In particular, the SERS probes were successfully tested for selective detection of all phosphate ions and down to 1 p.M phosphate concentration (30 p.g/L of phosphorus in the solution). The novelty of our contribution lies in real-time SERS monitoring of the phosphate Raman markers, which allowed to study the dynamics of phos-phate interaction with the nano-structured surface of the probes. Under natu-ral conditions (neutral to basic environment), the phosphates adsorb on the probes in form of PO3- (4) in two steps.