Detection, detoxification, and anti-counterfeiting applications of pullulan-modified nitrogen-doped carbon dots

Nitrogen-doped carbon dots (N-CDs) modified with pullulan were prepared using a hydrothermal method for use in sensing, detoxification, and anti-counterfeiting applications. The excitation-independent N-CDs demonstrated selectivity for hydroquinone and 4-nitrophenol (4-NP) with detection limits of 58 and 13 nM. The N-CD-based detection method was extended to environmental samples such as bottled water, tap water, and river water, and acceptable relative standard deviations (RSDs) and good recoveries were found. In the presence of NaBH4, N-CDs converted the toxic MB to colorless leuco-methylene blue in 10.5 minutes, confirming that the catalytic ability of N-CDs can be evaluated using MB as a model pollutant. With an excellent quantum yield of 31%, the N-CDs had the potential as a fluorescent ink for anti-counterfeiting applications by helping to visualize fingerprints, drawings, and chemical structures under 365 nm UV light while being completely invisible in daylight and sunlight. The N-CDs have significant potential for industrial use as fluorescent inks, detoxification catalysts, and pollutant sensors.