Palladium-gold bimetallic nanoparticles stabilized by daptomycin for sensitive colorimetric detection of sulfide ions

Sulfide ion is an important form of sulfur element, which is widely present in nature and has wide applications in industrial production and medicine. However, excessive sulfur ions may cause water acidification, harm aquatic organisms and destroy the balance of the ecological environment. In addition, long-term exposure to polluted water also poses a threat to human health, such as respiratory diseases or central nervous system symptoms. Therefore, it is crucial to develop a reliable and highly sensitive sulfur ion detection platform.

In this work, daptomycin as a template was used to prepare 2.12-6.76 nm palladium-gold bimetallic nanoparticles (Pd_nAu-Dap NPs). Pd_nAu-Dap NPs catalyzed 3,3',5,5'-tetramethylbenzidine (TMB) to generate blue oxidized TMB (oxTMB) in the presence of H₂O₂. Pd₃Au-Dap NPs exhibited excellent peroxidase-like activity at 30 °C and pH = 4. Furthermore, the peroxidase-like enzymatic activity of Pd₃Au-Dap NPs had excellent stability under different environments. More importantly, the enzyme catalytic kinetics of Pd₃Au-Dap NPs conformed to the typical Michaelis-Menten equation. In addition, Sulfide ions have reducing properties, which can inhibit the generation of oxTMB and reduce its absorbance at 652 nm. Therefore, sulfide ions can be detected by affecting the color change of oxTMB at different sulfide ion concentrations, which makes the detection process of sulfide ions simpler and more convenient, and has great development advantages.

A colorimetric detection platform for sulfide ions detection was established by Pd₃Au-Dap NPs. The detection linear range was from 0 to 70 μM, and the limit of detection was 0.58 μM. The colorimetric detection platform had excellent anti-interference properties and had been successfully utilized for sulfide ions detection in both seawater and lake water, demonstrating bright potential for practical applications.