Composites of Porous Carbon and Copper-Based Nanoparticles for the Electrochemical Analysis of Chemical Oxygen Demand

The intensive monitoring of water quality enforced by new wastewater regulations calls for the developing of fast and low-cost analytical technologies. Electrochemical sensors are poised to become alternative technologies for the sensitive analysis of environmentally relevant chemicals. A prerequisite for this evolution is engineering analyte-specific electrodes which are easily processed and can be mass-produced. This work studies different routes to prepare composites comprising a porous carbon matrix with Cu or Cu2O nanoparticles as electrodes to analyze chemical oxygen demand (COD) in wastewaters. The materials were prepared by physical mixing of the two components and one-pot chemical synthesis, characterizing their microstructure, porosity, nanoparticle distribution, and crystallinity. Then, their analytical performance was assessed by measuring glucose as a standard analyte and testing three real samples from a wastewater treatment plant. While all the materials performed well in the COD analysis, in excellent agreement with those obtained by the standard dichromate method, a one-pot synthesis approach stands out for its ease of production and analytical response. This one-step liquid processing is scalable and compatible with the industrial manufacturing of electrochemical sensors of planar configuration by screen-printing or microfabrication techniques.