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Development of an Electrochemical Nanosensor Array for the Detection and Quantification of Trace Amounts of Lead and Copper by Dip-Pen Nanolithography
Rahma Okbi; Rahmaokbi1999@gmail.com
Prof. Ariela Burg1, Dr. Moshe Zohar1, Dr. Dror Shamir2 1SCE - Shamoon College of Engineering, Be’er-Sheva 2Nuclear Research Center Negev, Israel.
Industrial development and rapid population growth have led to increased pollution in wastewater and water sources, with heavy metals significantly contributing to this contamination. Heavy metals, particularly lead, are known to be hazardous even at very low concentrations in the ppb )parts per billion( range and can cause serious health problems in humans. According to the WHO )World Health Organization(, the maximum permissible concentration of lead in drinking water is 10 ppb, highlighting the need for the development of sensitive and accurate sensors for the detection and quantification of lead in water.
One widely used technique for detecting heavy metals is ‘inductively coupled plasma mass spectrometry’ )ICP-MS(, which can detect low concentrations in the ppb range and simultaneously detects multiple cations; however, this instrument is expensive and not portable. Therefore, many research groups, including ours, have been working on developing electrochemical sensors. These electrochemical sensors offer short measurement times and are both cost-effective and portable. Nevertheless, a key limitation of such sensors is their inability to detect multiple cations simultaneously; also, many cannot detect concentrations within the permissible limits set by the WHO.
In this study, we initiated the development of nanosensors in the form of meta-chemical surfaces )MCS( using an NLP2000 device, which operates based on dip-pen nanolithography )DPN( technique. This method involves the deposition of nanoclusters of ink onto the electrode surface in a straightforward and cost-effective manner. The ink used is a mixture of the ligand, D-penicillamine, and the polymer, polymethyl methacrylate )PMMA(.
The sensitivity and efficiency of these sensors were assessed by electrochemical methods, revealing that they were capable of detecting lead in the presence of copper. The obtained limits of detection )LoD( were 0.30 ppb for lead alone and 0.41 ppb for lead in the presence of copper ions in solution, respectively.
Density functional theory )DFT( calculations were conducted to further explain sensor sensitivity for the determination of Gibbs free energy values, indicating the binding strength between the ligand and the cations. The results showed that the binding reactions were exothermic, with the binding of D-penicillamine to lead being more exothermic in the presence of PMMA )ΔG0 = -17.61 kcal/mol with PMMA and ΔG0 = -9.83 kcal/mol without PMMA(. This suggests that the presence of PMMA enhances the binding between the ligand and lead.
Additionally, we investigated the impact of an organic compound )acetonitrile( on the lead detection process. Unlike ICP-MS, which cannot analyze organic solutions, our sensor successfully detected lead in the presence of acetonitrile, demonstrating its robustness in various environments.
Our sensor, developed by means of the DPN method, is capable of detecting lead, in the presence of copper even in the presence of an organic contaminant, with high sensitivity in the ppb range.
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