A turn-on fluorescent nanoprobe based on N-doped silicon quantum dots for rapid determination of glyphosate

N-Doped silicon quantum dots (N-SiQD) were synthesized using N-[3-(trimethoxysily)propyl]-ethylenediamine and citric acid as silicon source and reduction agent, respectively. The N-SiQD shows a strong blue fluorescence with a high quantum yield of about 53%. It is found that a selective static quenching process occurs between N-SiQDs and Cu²⁺. Glyphosate can inhibit this phenomenon and trigger the rapid fluorescence enhancement of the quenched N-SiQDs/Cu²⁺ system due to the specific interaction between Cu²⁺ and glyphosate. With such a design, a turn-on fluorescent nanoprobe based on N-SiQD/Cu²⁺ system was established for rapid determination of glyphosate. The determination signal of N-SiQD/Cu²⁺ was measured at the optimum emission wavelength of 460 nm after excitation at 360 nm. Under optimal conditions, the turn-on nanoprobe showed a linear relationship between fluorescent response and glyphosate concentrations in the range 0.1 to 1 μg mL^-1. The limit of determination was calculated to 7.8 ng mL^-1 (3σ/S). Satisfactory recoveries were obtained in the determination of spiked water samples, indicating the potential use for environmental monitoring. Graphical abstract Schematic representation of N-SiQD/Cu²⁺ system for glyphosate determination. Fluorescence quenching of N-SiQDs induced by copper ions and the succedent fluorescent "turn on" triggered by glyphosate.