The controllable synthesis of orange-red emissive Au nanoclusters and their use as a portable colorimetric fluorometric probe for dopamine

Facile and accurate detection of dopamine (DA) in biological samples is crucial for diagnostic needs. This study reports a portable colorimetric fluorescent probe for the tracing of DA based on orange-red emitting Au nanoclusters (AuNCs). The AuNCs were reduced and stabilized with l-methionine by strictly controlling the reaction conditions. The resultant l-methionine capped AuNCs (M-AuNCs) exhibit bright and stable orange-red emission with a quantum yield of 31.08%. The excitation/emission wavelength is located at 420 nm/610 nm, and the large Stoke's shift of 190 nm endows the M-AuNCs with great potential as a late-model sensing probe for life studies and environmental science. The M-AuNCs exhibit unique specificity and excellent sensitivity for tracing DA by an on-off strategy with a lower limit of detection (LOD) of 3.96 nM (S/N = 3) within a linear range of 10-100 nM. Notably, the colorimetric detection results can be explored as a visual sensor for sensitive, reliable and real-time/on-site detection of DA with the assistance of a smartphone. The LOD can be determined as 81.94 nM within a wide linear range of 0.1-1.0 mu M by a smartphone. Furthermore, the M-AuNCs as a late-model potable probe allow simple and rapid discrimination of DA in serum, and the cellular imaging of the M-AuNCs indicated that the detection of DA can also be achieved in living cells, demonstrating their great feasibility for the tracing of DA in real samples.

Automated summary

This study presents a fluorescent probe based on Au nanoclusters for tracing dopamine. The probe exhibits high specificity and sensitivity for dopamine detection through an on-off strategy, and can be used for real-time detection with the assistance of a smartphone. Additionally, the probe allows for detection of dopamine in serum and living cells.