Electrochemical detection of lead ions using carbon nanotube post electrodes

Heavy metal ions above their recommended limits are highly toxic to human health. Even at low levels, contaminants such as Pb in drinking water can severely affect vulnerable population of the society. Therefore, developing rapid, effective, stable, and convenient sensors for Pb detection has gained significant attention. In this study, considering the excellent properties of carbon nanotubes (CNTs), CNT post electrodes were fabricated by embedding them in a nonconducting polymer. The CNT posts were derived from a closely packed CNT forest with a diameter of 0.3 mm containing millions of vertically aligned pillars. The highly stable CNT post electrodes were employed for the electrochemical sensing of heavy metal ions in 0.1 M citric acid. A linear range of 9.64-168.7 nM (2-35 ppb) was observed for Pb ions. Further, linear ranges of 0.0786-7.86 mu M (5-500 ppb) and 15.73-157.36 mu M (1000-10000 ppb) were also obtained for Cu ions. Notably, the electrode containing a single CNT post was capable of the electrochemical detection of Pb ions at the ppb level. With this electrode, the sensitivity and limit of detection were 0.5095nA/nM and 2 nM (0.5 ppb) for Pb ions, and 24.53 mu A/ppb and 41.67 nM (2.64 ppb) for Cu ions, respectively. The limit of detection for Pb ions is lower than the maximum permissible limit in drinking water set by the World Health Organization. Due the electrochemical method employed on its detection, the reported sensor can simultaneously detect Pb, Cu and Zn ions in tap water.