Bright yellow fluorescent nitrogen and boron doped-CNPs based turn “off–on” probe for highly sensitive and selective detection of glyphosate and hypochlorite

Abstract

In the present work, water-soluble fluorescent nitrogen/boron-doped carbon nano particles (N/B-CNPs) were prepared using o-phenylenediamine and boric acid precursors by a simple one step hydrothermal (HT) method. High Resolution Transmission Electron Microscope (HR-TEM) analysis showed that the N/B-CNPs are spherical in shape with an average size of ∼ 15 nm. The functional and structural composition of N/B-CNPs were confirmed by Fourier Transform Infrared (FTIR), Raman and Nuclear Magnetic Resonance (NMR) spectral studies. N/B-CNPs exhibited excellent photophysical property and photostability at different physiological conditions. N/B-CNPs showed bright yellow fluorescence at 566 nm upon excitation at 400 nm. N/B-CNPs were utilized as a fluorometric probe towards the simultaneous detection of glyphosate and hypochlorite. The fluorescence intensity of N/B-CNPs was selectively quenched in the presence of glyphosate (turn-off) and quenched emission intensity was restored in the presence of hypochlorite (turn-on). The fluorescence quenching mechanism was further ascertained using Stern-Volmer and time resolved fluorescence analysis. The detection probe showed a linear response for glyphosate over the concentrations range of 5.00 to 85.00 µM, with a limit of detection value of 0.088 µM. While in the case of hypochlorite the turn-on assay exhibited good linearity over the range of 5.00 to 50.00 µM with limit of detection as low as 0.12 nM. The N/B-CNPs turn-off/turn-on fluorometric assay exhibited excellent sensitivity and selectivity towards glyphosate and hypochlorite, even in the presence of other interference ions. The practical applicability of the proposed assay was demonstrated by fabricating a paper strip-based sensor and fluorescent thin film. Furthermore, the in vivo toxicity of the N/B-CNPs was evaluated in plant by performing dosage dependent assay.