Fabrication and characterization of a novel PMO containing riboflavin-5'-phosphate sodium salt for sensitive detection of pesticide ferbam

Abstract A highly sensitive and low-cost optical nanosensor of organic-inorganic hybrid material for pesticide ferbam detection was prepared by utilizing a novel organic siloxane precursor obtained from riboflavin-5'-phosphate sodium salt (Rf). A panel of characterizations was carried out to understand the structure, morphology and surface chemistry of the Rf periodic mesoporous organosilica (Rf-PMO) spherical nanosensors. For the Rf-PMO materials, the doped silica nanoparticles exhibit strong fluorescence emission at 520 nm, on account that the greater steric hindrances and the more separated state of π-conjugate planer platforms between Rf molecules embedded within the silica framework can both enhance the fluorescence emission and reduce the self-quenching of fluorescence produced by stacking aggregation of Rf. The electron spin resonance (ESR) spectra prove that the prepared Rf-PMO materials can participate in the redox reaction through electron transfer with the pesticide ferbam. Utilized the reducing reaction mechanism of Rf-PMO, it is applied to detect pesticide ferbam with high sensitivity and selectivity, with the limit of detection (LOD) in aqueous solution as low as 6.97 × 10-9 M. Moreover, the X-ray absorption near-edge spectroscopy (XANES) of Fe K-edge shows a coordination structure through the interaction between iron ions from ferbam and O and N atoms in Rf-PMO. X-ray photoelectron spectroscopy (XPS) further reveals the redox mechanism. Therefore, the designed and prepared Rf-PMO is potentially valuable to food safety monitoring involving ferbam as the nanosensor, due to its hypersensitivity and selectivity.