Development of electrochemical heavy metals microsensors using Dip-Pen Nanolithography (DPN)

Zorik Shamish, NRCN, Omer, Israel (zoriksh@gmail.com)

 

 

Rapid globalization and industrialization have caused an increase in heavy metals concentrations, especially lead (Pb) and mercury (Hg), in wastewater. The traditional methods for identifying and quantifying these pollutants are often complex and inaccessible, especially in the ppt-ppb range. To improve the detection method, we turn to electrochemical sensors, which offer reasonable costs and high portability, making them ideal for on-site analysis. 

The current study presents an innovative method for patterning ink (a mixture of glutathione, PMMA, and acetonitrile) as nanoclusters on gold working electrodes using Dip-Pen Nanolithography (DPN) for Meta-Chemical-Surface (MCS) production. These MCS sensors improve sensitivity by maximizing the surface area to volume (S/V) ratio of the nanoclusters. 

The results indicate that the MCS sensor could detect Pb(II) and Hg(II) in the ppt-ppb range, and as expected, the sensitivity for Hg(II) decreases when the solution includes two heavy metals compared to one (LoD of 0.78 ppb and 0.18 ppb, respectively). However, the sensitivity for Pb(II) increases as the two metals are in the solution, compared to one (LoD of 0.81 ppb and 1.01 ppb, respectively). 

DFT calculations were done in order to explain these results. The calculations indicate that lead can bind to the carbonate residue better than the sulfur residue; however, mercury doesn’t bind to the carbonate residue when present individually. Mercury binds to the carbonate residue only when lead binds to the sulfur residue. For lead, the addition of mercury increases the binding strength; however, for mercury, the addition of lead decreases the binding strength. These are important results for the wastewater treatment field.