Solution-Processable Bismuthene Nanosheets for Ultrasensitive Sensing of Heavy Metal Ions via Anodic Stripping Voltammetry

Bismuthene, a two-dimensional nanostructured material derived from the environmentally friendly and nontoxic element bismuth, holds significant potential for sustainable electrocatalytic applications. However, the large-scale application of bismuthene is hindered by the absence of a high-throughput method for synthesizing solution-processable bismuthene nanosheets, which are essential for the straightforward and low-cost fabrication of bismuthene-based nanostructure devices. This study introduces a simple solvothermal method for synthesizing bismuthene nanosheets, using hexamethylenetetramine (HMTA) as a structure-directing agent and in situ-generated hydrogen (H₂) from the alkaline hydrolysis of NaBH₄ as the reducing agent. The structural and electron transfer properties were characterized by using microscopic, spectroscopic, and electrochemical analyses. To demonstrate the electrocatalytic application potential, a bismuthene-modified screen-printed carbon nanotube electrode was fabricated as a nanosensor for the quantitative detection of heavy metal ions in contaminated water. The nanosensor exhibited a wide linear concentration range and low detection limits of 0.1 and 0.16 ppb (μg/L) for Cd and Pb, respectively. Additionally, the sensor was integrated with a microfluidic flow cell, demonstrating its applicability for the flow-through analysis of Cd and Pb ions. The nanosensor showed high selectivity for Cd and Pb ions in the presence of other metal ions with excellent repeatability and sensor-to-sensor reproducibility, evidenced by a relative standard deviation of 2% and 10%, respectively.