Yu Ding's research while affiliated with Ocean University of China and other places

Copper ions (Cu²⁺) pollution in the water environment poses a great threat to the health function of life-sustaining metabolic activities. However, the current detection methods need relatively expensive instruments, complex operation procedures and long time, so a facile and direct detection method is desired to be developed. In this work, the Ni-based composite wires with p-n junction (the Ni/NiO/ZnO/Chitosan wire) and Schottky junction (the Ni/NiO/Au/Chitosan wire) were fabricated, and the barrier driven electrochemical sensing mechanism was studied. The direct and facile detection of Cu²⁺ was achieved with a wide linear range (0–6000 nM) and a low LOD (0.81 nM). The excellent stability and recovery in real water samples made the Ni-based composite wires a promising candidate for the practical application. The interfacial barriers of semiconductor can be used as a special sensing factor to develop novel sensors.

Analytes with similar redox properties are normally difficult to distinguish through classic electrochemical methods. This becomes especially true for the on‐site detection in seawater where the high salinity and complex chemical components can impose severe interference. Hereby introducing numerous nanoscale heterojunctions in the Cu/CuO/reduced graphene oxide (rGO)/polypyrrole (PPy) and Cu/CuO/rGO/chitosan electrochemical sensors, tunable interfacial energy barriers to exponentially regulate the electrochemical signal can be constructed. Importantly, these energy barriers are independent to redox but closely related to the electrostatic interaction from absorbed charged analytes such as Hg2+ and Cu2+. Moreover, the similar sensing principle is also valid for the energy barriers in p‐n junctions as demonstrated in the Ni/NiO/ZnO/PPy sensor. The good anti‐interference properties and ultrahigh sensitivity of this sensing mode offers new opportunities in trace analyte detection in harsh environments such as seawater. By constructing different metal wires based hierarchical structures, interfacial energy barriers of Schottky or p‐n junctions are successfully introduced into the electrochemical sensors. The height of the energy barrier can be modified corresponding to the different charged analytes, which can be exponentially reflected in the electrochemical response of the sensor with outstanding specificity.

The NiMn2O4/C necklace-like microspheres (NLM)¹ were successfully prepared by hydrothermal method and oil bath. This unique necklace-like structure makes them exhibit the enhanced intrinsic oxidase-like activity, as the special interface can help capture electrons from 3,3',5,5'-tetramethylbenzidine. The fabricated NiMn2O4/C NLM were successfully used as the high-performance oxidase mimetic to catalyze the oxidation of TMB directly for the color reaction. A simple colorimetric method for detection of ascorbic acid by fading was developed, and the high sensitivity with the low detection limit (0.047 μM) was achieved. It is a facile route to fabricate the NiMn2O4/C NLM as the high-performance oxidase mimetic for colorimetric biosensing.

Electrochemical sensing signal is easily interfered by substance with similar redox, which is difficult to be eliminated. The adjusting effect of interfacial barrier on electrochemical response was proposed to suppress this interference. Porous reduced graphene oxide encapsulated ZnO microspheres were prepared and used for detecting dopamine. The response to dopamine is enhanced and the responses to ascorbic acid and uric acid are decreased by changing the barrier height. An ultrahigh sensitivity (1240.74 μA mM⁻¹ cm⁻²) with a wide linear range is 1−600 μM and excellent selectivity to dopamine is achieved. Employing the interfacial barrier to adjust electrochemical response is a promising approach to improve the specificity and sensitivity of electrochemical sensors.

A novel type of electrochemical sensor for detection of phosphate in water environment was developed by combining the interfacial barrier of p-n junction with the adsorption of phosphate. The electrochemical response was produced by the induced change of the barrier height, which was only caused by the specific adsorption of phosphate. Two linear concentration ranges (0 - 0.045 mg·L-1 and 0.045 - 0.090 mg·L-1) with two sensitivities (4.98 µA·(µg·L-1)-1 and 1.28 µA·(µg·L-1)-1) were found. The good performance made the sensor meet the requirements of the World Health Organization for drinking water (1 mg·L-1 of phosphate) well. It is an approach to develop electrochemical sensors by employing the interfacial barrier effects on electrochemistry.