Bright yellow fluorescent N-doped Ti3C2 MXene quantum dots as “on/off/on” nanoprobe for selective As3+ ion detection

Abstract

Ti3C2 MXene quantum dots (MQDs) are considered as emerging nanomaterial in recent times, while maximum of MQDs exhibit limited emission properties in the blue-light region. Longer wavelength emissive quantum dots are highly desirable in different biological aspects including deep tissue penetration, superior signal-to-noise ratio, reduced radiation damage, etc. In this study, bright yellow fluorescent nitrogen-doped MQDs (N-MQDs) were successfully prepared using one-pot hydrothermal method. The synthesized N-MQDs showed maximum emission at 570 nm upon excitation wavelength of 420 nm with an optimum fluorescence quantum yield of 13.8 %. Interestingly, the emission of N-MQDs could be significantly quenched upon the addition of As3+ ion. Mechanism investigation revealed that static quenching were involved behind the fluorescence decrement via the formation of non-fluorescent complex due to the interaction of N-MQDs’ functional groups and As3+. The quenched fluorescence was surprisingly recovered upon the treatment of 2-amino-6-methoxybenzothiazole (MBTZ) in the complex. Strong interaction of MBTZ with As3+ lead to the detachment of quencher from N-MQDs resulted in fluorescence recovery. The re-appearance of N-MQDs’ functional groups after the addition of MBTZ was confirmed from spectroscopic study. Thus, fluorescence “on/off/on” phenomenon was utilised from N-MQDs nanoprobe for instantaneous detection of As3+ and MBTZ. The values for limit of detection were calculated as 30 nM and 0.44 µM with a good linearity for respective As3+ and MBTZ. In addition, solid sensor has been fabricated to recognize As3+ in wastewater revealing its potentiality towards on-site application in near future.