Fe3+-functionalized carbon quantum dots: A facile preparation strategy and detection for ascorbic acid in rat brain microdialysates

Abstract

This study reports an Fe3+-functionalized carbon quantum dots (Fe3+-functionalized CQDs) for the highly sensitive and selective detection of ascorbic acid (AA) in rat brain microdialysates based on the specific redox reaction between iron(III) ions and AA. The carbon quantum dots (CQDs) were synthesized by one-step pyrolysis of a small organic molecules i.e. tris(hydroxymethyl)aminomethane (Tris). Fe3+ can tightly chelate to the surface of CQDs by the hydroxyl group to form Fe3+-functionalized CQDs while the fluorescence of CQDs can be effectively quenched by Fe3+ via Fluorescence resonance energy transfer (FRET). The fluorescence of the Fe3+-functionalized CQDs can be sensitively turned on by AA to give an “on–off–on” fluorescence response through the oxidation–reduction between Fe3+ and AA since the produced Fe2+ has much lower chelating ability to CQDs and the fluorescence of CQDs can be restored. This Fe3+-functionalized CQDs based nanoprobe shows high selective and sensitive response in the concentration of AA ranging from 0.1μM to 50μM with the detection limit as lower as 9.1nM, which is lower than other assays. Finally, the proposed fluorescent probe was successfully applied to direct analysis of AA in biological fluids, i.e. rat brain microdialysates, and may pave a new route to the design of effective carbon quantum dots-based fluorescence probes for other bioassay.