Simultaneous label-free and pretreatment-free detection of heavy metal ions in complex samples using electrodes decorated with vertically ordered silica nanochannels

In this work, indium tin oxide coated glass (ITO) decorated with vertically-ordered mesoporous silica film (VMSF/ITO) is synthesized and applied as electrochemical sensor for simultaneous label-free and pretreatment-free detection of Pb²⁺, Cu²⁺, and Cd²⁺ in human serum and soil leaching solution. Using differential pulse voltammetry (DPV), the electrochemical detection consists of electro-deposition of metal species and subsequent anodic stripping in the silica nanochannels. Because of the electrostatic enrichment and nano-confinement effects, VMSF/ITO is able to simultaneously detect Pb²⁺, Cu²⁺, and Cd²⁺ in a mixture with low detection limits (2.6 nM, 32 nM and 230 nM, respectively). Moreover, VMSF confer the electrode with excellent anti-fouling and anti-interference property through steric exclusion and electrostatic repulsion. Direct analysis of complex biological (human serum) and environmental (soil leaching solution) samples could be finished within 10 min without the usual need of tedious pretreatment. Furthermore, the VMSF/ITO sensor can be reused for several times without performance degradation.