Physicochemical Insights into As, Cd, Hg, and Pb Heavy Metals and Catechol Sensing on a Buckled Si9C15 Nanosheet: A First-Principles Study

The contamination of water resources by toxic heavy metals and organic pollutants poses a serious ecological and human health challenge, which demands the development of efficient sensing materials. A detailed investigation was undertaken to examine the adsorption and sensing performance of the recently synthesized Si9C15 nanosheet toward hazardous heavy metals (As, Cd, Hg, and Pb) and the organic pollutant catechol (CC) based on density functional theory (DFT). The pristine Si9C15 nanosheet was found to be mechanically stable, isotropic, and hydrophilic. Cd and Hg exhibited comparatively weak adsorption with binding energy values of −0.46 eV (−0.42 eV) and −0.43 eV (−0.41 eV) in vacuum (water), whereas strong adsorption was observed for As and Pb with binding energy values of −3.43 eV (−3.46 eV) and −2.18 eV (−2.25 eV), respectively. Catechol exhibited moderate adsorption in vacuum (−0.74 eV), which became stronger in the presence of water (−1.36 eV), owing to additional intermolecular interactions. Noticeable optical responses were observed for heavy metal and catechol-decorated Si9C15 nanosheets. Catechol exhibited a rapid recovery time of 2.70 s at room temperature. Collectively, these results establish the potential of the Si9C15 nanosheet as a multifunctional platform for monitoring toxic heavy metals and the organic contaminant catechol in water.