N–C dot/Cr (VI) nanoprobe: a fluorescent uric acid sensor

Abstract

Detection of uric acid (UA) is inevitable today, as very less amount of uric acid in human leads to Fanconi Syndrome, Wilson’s disease and cardiovascular disorders. Here, we report an eco-friendly synthesis of a nitrogen-doped carbon dot/Chromium (VI) [N–C dot/Cr (VI)] fluorescent nanoprobe for nanomolar detection of uric acid. N–C dot/Cr (VI) nanoprobe is synthesized using solvent free, fast, easy, green, pyrolysis method, which is characterized using UV–VIS, FTIR, XRD, SEM- EDX and PL technique. Addition of Cr (VI) to fluorescent N–C dot leads to immediate turn OFF in fluorescence with the formation of N–C dot/Cr (VI) nanocomposite. The lowest detection limit of Cr (VI) by N–C dot is 1.42\u2009×\u200910–9 M. For the first time, we are reporting uric acid, a reducing agent to reduce Cr (VI) to lower valent Cr (III)/Cr (0). The addition of uric acid turns ON the fluorescence with the elimination of inner filter effect (IFE) thus N–C dot/Cr (VI) nanoprobe functioning as a Turn Off–On fluorescent nanosensor for the detection of UA. The efficiency of the sensor is based on fluorescence resonance energy transfer between N-Carbon dots and chromium (VI). A linear response was noted with every nanomolar addition of uric acid. The lowest detection limit toward sensing of UA is found to be 12.5\u2009×\u200910–9 M. Thus, the novelty of this method is nanomolar amount of redox species is enough to form a stable nanocomposite and the N-CDs/Cr (VI) nanocomposite is able to sense nanomolar to millimolar concentration of uric acid within a few seconds. The nanoprobe is found to be stable, simple and cost effective which can be extended for detection of uric acid in vegetables, fruits and also in clinical studies.