Point-of-need electrochemical detection of Cu²⁺ via target-accelerated growth of gold nanoparticles

A point-of-care sensor was initially reported for portable detection of Cu 2+ ions. • It was based on the Cu 2+ -accelerated growth of gold nanoparticles. • These nanoparticles could enhance the conductivity of screen-printed electrodes. • Only a hand-held electrochemical reader was required to achieve a detection limit down to ∼1.6 nM. This paper initially reports an electrochemical method for point-of-care sensing of divalent copper (Cu 2+ ) ions by combining screen-printed electrodes (SPEs) with a hand-held current reader. In the buffer of 4-morpholineethanesulfonic acid, chloroauric acid can be slowly reduced into gold nanoparticles (GNPs). In the presence of Cu 2+ , the analyte is able to significantly promote the growth process of GNPs. These GNPs generated in the reaction solution then act as efficient electronic nanoconductors to greatly enhance the SPE’s conductivity leading to an enhanced current response. The enhancement degree of this current signal is positively proportional to Cu 2+ concentration in the sample. The results indicate that this new electrochemical method only requires disposable SPEs without functional modification and a user-friendly, portable current reader to linearly detect Cu 2+ in a concentration range of 24.41 - 6250 nM. Its detection limit is estimated to be about 1.6 nM (3σ rule), which is far lower than the maximum allowable concentrations in drinking water stipulated by the World Health Organization (∼30 µM) and the National Health Commission of China (∼15 µM). The acceptable recovery of Cu 2+ in several real water samples (i.e., drinking water, tap water and pond water) is between 98.03 and 106.95%. Download: Download high-res image (118KB) Download: Download full-size image