Rapid and sensitive fluorescence and smartphone dual-mode detection of dopamine based on nitrogen-boron co-doped carbon quantum dots.

A dual-mode fluorescence and colorimetric biosensor based on nitrogen-boron co-doped carbon quantum dot (N-B CQDs) for rapid and sensitive detection of dopamine (DA) was developed. The quantum dot luminescent materials, N-B CQDs, were prepared by a one-step microwave-assisted method. The N-B CQDs were characterized using SEM, HR-TEM, XRD, FT-IR, Raman, fluorescence, and UV-Vis techniques. The dual-mode assays of fluorescence and colorimetric methods were used for detection of DA. The high fluorescent N-B CQDs mediated turn-off assay for the facile room temperature detection of dopamine via inner filter effect (IFE) and Forster resonance energy transfer (FRET) processes at basic pH. The colorimetric detection of DA was also developed via in-house android application using a smartphone and N-B CQD solution-based nanosensor. The smartphone-based colorimetric biosensors generated more reliable information for quantitative analysis of color changes than the naked eye. Furthermore, a smartphone application with N-B CQD solution-based nanosensor was integrated to monitor the color changes through the DA addition. Wide linear ranges were achieved for DA in the ranges 0.25-50 µM and 5-500 µM with fluorescence and smartphone-based method, respectively. The satisfactory results of the dual-mode detection of DA, not only in aqueous solution, but also in human urine and serum biological sample demonstrated its potential application in biosensing, as a point of care diagnostic tool. Graphical abstract.