Highly stable branched cationic polymer-functionalized black phosphorus electrochemical sensor for fast and direct ultratrace detection of copper ion.

Abstract Copper ions (Cu2+) is an indispensable trace element in the process of metabolism and intake of excessive Cu2+ may lead to fatal diseases such as Alzheimer's disease. It is highly demanding to develop a sensitive, selective and convenient method for Cu2+ detection. In this work, thin-layer structured polyethyleneimine (PEI) decorated black phosphorus (BP) nanocomposite is one-step synthesized for an electrochemical sensor toward direct detection of Cu2+. This sensor achieves a wide detection range of 0.25–177 μM, a low detection limit of 0.02 μM much below the Environmental Protection Agency (EPA) maximum contaminant levels for drinking water (20 μM for Cu2+), and much faster response (1.5 s response time) and simpler operation than the conventional tedious anodic stripping voltammetry, ranking one of the best among all reported Cu2+ sensor. The great sensing enhancement is mainly due to a synergistic effect of BP and PEI of the composite, of which the former offers the reactivity while the latter splits the thick BP to thin-layer structured PEI-BP composite for larger reaction area. Meanwhile, a flexible sensor has been successfully fabricated and applied in detecting of Cu2+ in real samples of river, confirming the application feasibility of PEI-BP sensor in water environment control.