Dip-pen nanolithography-fabricated Bi and Hg meta-chemical surface sensors for ultra-sensitive detection of heavy metals in water

The toxicity of heavy metals in water sources requires the use of sensitive devices capable of detecting levels in the parts-per-billion (ppb) range. In this study, meta-chemical surface (MCS-Bi and MCS-Hg) sensors were developed using dip-pen nanolithography (DPN), which enhanced the detection of Cd(II), Pb(II), and Cu(II) at ppb levels, due to DPN's unique ability to control the surface-to-volume (S/V) ratio of patterned nanoclusters. The density functional theory results indicate that the binding strengths between the heavy metals and the active species (Hg and Bi) are comparable. The difference in the S/V ratio affects the detection limit (0.26 ± 0.04 and 0.52 ± 0.02 ppb for MCS-Bi and MCS-Hg, respectively). This finding highlights the relevance of MCS sensors to the environmental field, their enhanced detection capabilities for toxic materials, and the reduced use of hazardous materials like mercury. The results provide a concrete methodology for reducing the toxicity of analytical devices without compromising sensitivity.