Multifunctional Copper Nanoclusters for the Detection of pH and Berberine Hydrochloride

The copper nanoclusters (CuNCs) have been garnered significant attention owing to their low cost raw materials, outstanding optical properties, environmental friendliness and good biocompatibility. In this study, copper nanoclusters stabilized by Acid Chromic Blue K (ACBK-CuNCs) were synthesized. The optimal excitation wavelength of the synthesized ACBK-CuNCs is 344 nm and the optimal emission wavelength is 460 nm. Its fluorescence intensity can be retained for more than two weeks, which indicated that the antioxidant capacity of the synthesized ACBK-CuNCs is strong. It was noted that the fluorescence intensities of the synthesized ACBK-CuNCs significantly increased with the decrease of pH. There are good linear correlation between the fluorescence intensity ratio of the system to the fluorescence intensity of the original solution (F/F₀) and the pH of the medium. Based on this finding, a method for fluorescence analysis to detect the pH of solution was developed. Additionally, it was discovered that the fluorescence intensity of CuNCs could be quenched efficiently by Berberine hydrochloride (BH), and there is a favorable linear relationship between the change value of fluorescence intensity of CuNCs ((F₀ - F) / F₀) and the concentration of BH. This gave rise to the establishment of a fluorescence analysis method for determining the concentration of BH. Simultaneously, visual quantitative detection for BH and pH was achieved based on smartphones and colorimetric analysis software using ACBK-CuNCs as the fluorescent probes.