(618e) Surfactant-Mediated Synthesis of Bismuth Oxychloride Nanoflowers for Electrochemical Detection of Heavy Metal Ions

Contamination of municipal water with heavy metal ions poses a significant but often invisible risk to public health. While governmental agencies such as the Environmental Protection Agency (EPA) work diligently to set and enforce regulatory limits on heavy metal levels, their focus tends to be on localized hotspots in high-risk areas. Their sample analysis techniques are generally costly, inaccessible to the public, and require specialized training. Moreover, their oversight is limited to public infrastructure, leaving private water systems vulnerable to corrosion and contamination. While individuals can ship private water samples to local laboratories for analysis, practical monitoring of potential drinking water contamination requires more active and decentralized sensing methods to ensure reliability.

Recognizing the growing need for independent oversight in identifying and addressing toxic exposure, we proposed the use of high surface area bismuth oxychloride nanoflowers for detection of zinc and lead ions in drinking water. In consideration of the electrochemical methodology of sensing and their simple manufacturing procedure, they are an improved material for widespread use. Our method for the synthesis of the high surface area bismuth oxychloride nanoflowers involved the hydrolysis of bismuth chloride salt in an aqueous environment of sodium dodecyl sulfate. Generally, the reaction of bismuth chloride with water results in thin plate-like bismuth oxychloride structures primarily dominated by the 001 crystalline phase. We discovered that presence of surfactant sodium dodecyl sulfate was capable of crystallization behavior, encouraging the growth of 101 and 110 phases while reducing the 001 growth. The resulting structure was a uniform nanoflower material, as in the provided figure. This simple synthesis approach required no toxic materials for chemical reduction and proceeded immediately upon introduction of the salt into water, making it a highly scalable methodology.

In this work we proposed a mechanism for the formation of the uniform nanoflower structure, uniquely associated with the sodium dodecyl sulfate surfactant. We proposed that this growth is a result of the enhanced presence of the 110 and 101 crystalline phases, which undergo branching during crystallization in a uniform, concentric pattern. With additional surfactant addition, the restricted 001 growth encouraged further branching along additional angles from derivative phases such as 102, 103, 111, 112, etc., creating complex, high surface area flower structures. The as-synthesized nanoflowers were then suspended in Nafion solutions and deposited onto a glassy carbon electrode. Subsequent cyclic voltammetry analysis demonstrated the response to the analyte ions (Pb(II), Zn(II)), allowing for the detection of lead and zinc ions independently and simultaneously down to 1ppm. The implication of these results is the potential of bismuth-based structures for portable and accessible detection of heavy metal ions. Through parameter-focused structural optimization, we anticipate further improvements in sensitivity, paving the way for more effective monitoring of water quality and protection of public health.