Using N-doped Carbon Dots Prepared Rapidly by Microwave Digestion as Nanoprobes and Nanocatalysts for Fluorescence Determination of Ultratrace Isocarbophos with Label-Free Aptamers

The strongly fluorescent and highly catalytic N-doped carbon dots (CD_N) were rapidly prepared by a microwave irradiation procedure and were characterized by electron microscopy (EM), laser scattering, infrared spectroscopy (IR), and by their fluorescence spectrum. It was found that the CD_N had a strong catalytic effect on the fluorescence reaction of 3,3′,5,5′-tetramethylbenzidine hydroxide ((TMB)⁻H₂O₂) which produced the oxidation product of TMB (TMB_OX) with strong fluorescence at 406 nm. The aptamer (Apt) was adsorbed on the CD_N surfaces which weakened the fluorescence intensity due to the inhibition of catalytic activity. When the target molecule isocarbophos (IPS) was added, it reacted with the Apt to form a stable conjugate and free CD_N which restored the catalytic activity to enhance the fluorescence. Using TMB_OX as a fluorescent probe, a highly sensitive nanocatalytic method for determination of 0.025⁻1.5 μg/L IPS was established with a detection limit of 0.015 μg/L. Coupling the CD_N fluorescent probe with the Apt⁻IPS reaction, a new CD fluorescence method was established for the simple and rapid determination of 0.25⁻1.5 μg/L IPS with a detection limit of 0.11 μg/L.

Abstract licence: CC BY

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