Eco-friendly ZnO-modified SPCE platform for highly sensitive electrochemical sensing of heavy metal contaminants

There are serious threats to the environment and human health from the growing contamination of water supplies by hazardous heavy metals, such as Pb(II), Cd(II), Hg(II), and As(III). Despite their sensitivity, conventional analytical methods’ field usability is limited by their need for costly equipment and centralized labs. Thus, there is a pressing need to develop portable, environmentally friendly, and extremely sensitive electrochemical sensors. Conventional ZnO nanoparticle manufacturing methods sometimes require energy-intensive procedures and dangerous ingredients. By combining phyto-assisted ZnO nanoparticles with a screen- printed carbon electrode (SPCE), this study seeks to provide an economical and environmentally friendly electrochemical sensing platform for the ultra-trace detection of many heavy metal ions. The leaf extract of Lepisanthes rubiginosa was used as a natural stabilizing and reducing agent in the green synthesis of ZnO nanoparticles. The nanoparticles were drop-cast onto an activated SPCE after being integrated into a polyvinyl alcohol (PVA) matrix. Electrochemical impedance spectroscopy and structural and morphological characterizations (UV-Vis, XRD, FTIR, SEM-EDX) verified effective synthesis and improved charge-transfer characteristics. The PVA/ZnO-modified SPCE demonstrated exceptional electrochemical performance and a markedly decreased charge-transfer resistance. A straightforward cyclic voltammetry method was used to obtain ultra-trace detection limits of 2 nM for Pb(II), 1–50 fM for Cd(II), 1 fM for Hg(II), and 100 fM for As(III). The sensor uses a cheap disposable electrode and green synthesis, and it shows better sensitivity than several published platforms. In order to identify heavy metals in real time, this work offers a portable, extremely sensitive, and sustainable electrochemical platform that connects environmental monitoring and green nanotechnology.