Solution-Processable\nBismuthene Nanosheets for Ultrasensitive\nSensing of Heavy Metal Ions via Anodic Stripping Voltammetry

Bismuthene, a two-dimensional nanostructured material\nderived from\nthe environmentally friendly and nontoxic element bismuth, holds significant\npotential for sustainable electrocatalytic applications. However,\nthe large-scale application of bismuthene is hindered by the absence\nof a high-throughput method for synthesizing solution-processable\nbismuthene nanosheets, which are essential for the straightforward\nand low-cost fabrication of bismuthene-based nanostructure devices.\nThis study introduces a simple solvothermal method for synthesizing\nbismuthene nanosheets, using hexamethylenetetramine (HMTA) as a structure-directing\nagent and in situ-generated hydrogen (H<sub>2</sub>) from the alkaline\nhydrolysis of NaBH<sub>4</sub> as the reducing agent. The structural\nand electron transfer properties were characterized by using microscopic,\nspectroscopic, and electrochemical analyses. To demonstrate the electrocatalytic\napplication potential, a bismuthene-modified screen-printed carbon\nnanotube electrode was fabricated as a nanosensor for the quantitative\ndetection of heavy metal ions in contaminated water. The nanosensor\nexhibited a wide linear concentration range and low detection limits\nof 0.1 and 0.16 ppb (μg/L) for Cd and Pb, respectively. Additionally,\nthe sensor was integrated with a microfluidic flow cell, demonstrating\nits applicability for the flow-through analysis of Cd and Pb ions.\nThe nanosensor showed high selectivity for Cd and Pb ions in the presence\nof other metal ions with excellent repeatability and sensor-to-sensor\nreproducibility, evidenced by a relative standard deviation of 2%\nand 10%, respectively.