A Sensitive Turn off – Turn on Fluorescent Probe for Detection of Biothiols Using Mno2@Carbon Dots

Abstract

Presently, the combination of carbon quantum dots (CQDs) and metal oxide nanostructures in one frame are being considered for the sensing of purine compounds. In this work, a combined system of CQDs and MnO2 nanostructures was used for the detection of anticancer drugs – 6-Thioguanine (6-TG) and 6-Mercaptopurine (6-MP). The CQDs were synthesized using bottom-up approach through microwave synthesizer and the MnO2 nanostructures (nanoflowers and nanosheets) were synthesized using facile hydrothermal technique. The CQDs exhibited excellent fluorescence emission at 420 nm when excited at 320 nm wavelength. When combining CQDs and MnO2 nanostructures, quenching of fluorescence was observed which was attributed to fluorescence resonance energy transfer (FRET) mechanism, where CQDs act as electron donor and MnO2 nanostructures act as acceptor. This fluorescence quenching behaviour disappeared on the addition of 6-TG and 6-MP due to the formation of Mn-S bond. The detection limit (LOD) of 0.01 M for 6-TG and 6-MP was achieved with the linear range of concentration of 0-50 M using both MnO2nanoflowers (NF) and nanosheets (NS). Moreover, the as-prepared fluorescence-sensing technique was successfully employed for the detection of bio-thiol group in enapril drug. Thus a facile, costeffective and benign chemistry approach for biomolecule detection was designed.