Quantification and visualization of penicillin G residues in milk using a ratiometric fluorescent nanoprobe based on carbon dots and gold nanoclusters

Abstract

Developing an effective assay for monitoring penicillin G (PNG) is important for safeguarding ensuring public health and food safety. This work details the application of carbon dots (CDs) emitting blue light and gold nanoclusters (GNCs) with red emission as ratiometric fluorescence (RF) probes for the sensitive detection of PNG. The RF probe under a single excitation of 360 nm wavelength displayed two discrete emission peaks at 444 and 660 nm related to CDs and GNCs, respectively. Following the introduction of PNG, the red fluorescence intensity of GNCs was found to be reduced through the inner filter effect (IFE); meanwhile, the blue fluorescence of CDs remained unchanged under optimal conditions. The quantification of PNG can be achieved by this RF nanoprobe by following the I660/I444 ratio in two ranges of 0.1–0.8 ppm and 0.8–30.0 ppm and with a limit of detection (LOD) as low as 30 ppb. Furthermore, the RF probe has been successfully employed to determine PNG in milk samples with acceptable recoveries and results were validated by HPLC. Finally, the visual capability of this RF probe can greatly enhance and facilitate on-site determination process of PNG.