In this paper, graphdiyne (GDY)−modified glassy carbon electrode was prepared and further used for the sensitive and simultaneous detection of three target heavy metal ions of Zn²⁺, Cd²⁺ and Hg²⁺ by codeposition with Bi³⁺ in the mixture solution. GDY−modified electrodes exhibit a larger electrode area and abundant active sites, which is favorable for absorbing more metal ions. Bismuth has low toxicity and can form alloys with zinc, cadmium and mercury. Therefore, three kinds of heavy metal ions can be pre-concentrated with bismuth on the GDY−modified electrode surface, and the following stripping analysis results in high sensitivity and selectivity. By using differential pulse anodic stripping voltammetry, the detection ranges of Zn²⁺, Cd²⁺ and Hg²⁺ were from 2.0 to 100.0 μM with low detection limits of 0.255 μM, 0.367 μM and 0.796 μM, respectively. In addition, the sensor showed excellent repeatability, reproducibility, and stability, which was applied to sensitive analysis of river water samples with satisfactory results.

To design a new electrochemical horseradish peroxidase (HRP) biosensor with excellent analytical performance, black phosphorene (BP) nanosheets and single-walled carbon nanotubes (SWCNTs) nanocomposites were used as the modifier, with a carbon ionic liquid electrode (CILE) as the substrate electrode. The SWCNTs-BP nanocomposite was synthesized by a simple in situ mixing procedure and modified on the CILE surface by the direct casting method. Then HRP was immobilized on the modified electrode with Nafion film. The electrocatalysis of this electrochemical HRP biosensor to various targets was further explored. Experimental results indicated that the direct electrochemistry of HRP was realized with a pair of symmetric and quasi-reversible redox peaks appeared, which was due to the presence of SWCNTs-BP on the surface of CILE, exhibiting synergistic effects with high electrical conductivity and good biocompatibility. Excellent electrocatalytic activity to trichloroacetic acid (TCA), sodium nitrite (NaNO₂), and hydrogen peroxide (H₂O₂) were realized, with a wide linear range and a low detection limit. Different real samples, such as a medical facial peel solution, the soak water of pickled vegetables, and a 3% H₂O₂ disinfectant, were further analyzed, with satisfactory results, further proving the potential practical applications for the electrochemical biosensor.