Direct redox sensing of uranium using copper oxide quantum dots

Journal of Molecular Liquids, Volume 292, 15 October 2019, 111455 

GauravBhanjana, InderpreetToor, Ganga RamChaudhary, NeerajDilbaghi, Ki-HyunKim, SandeepKumar

Advances in technology are driving the population toward portable devices and inexpensive sensors. Although a massive volume of water is accessible across the globe, there are problems with access to potable water. Quality checks ensure timely management of several aquatic contaminants. This research article reports a novel electrochemical technique for direct determination of uranyl ions in water samples based on copper oxide (CuO) quantum dots (QDs: size range 5–10 nm). The QDs were synthesized by a chemical precipitation method and were obtained in monoclinic phase of pure CuO with highly crystalline nature. The band gap of the synthesized CuO quantum dots was found to be 2.6 eV. These CuO QDs were coated on gold (Au) surfaces to fabricate CuO/Nafion/Au electrodes. Nanoengineering of CuO QDs was further explored to produce efficient electro-catalysts for direct redox sensing of uranyl ions (U⁶⁺). Cyclic voltammetry (CV) procedures were optimized and standardized for qualitative and quantitative determination of uranyl ions in water samples. The fabricated sensing electrode displayed a high sensitivity of 130 μA cm⁻² ppm⁻¹ with a limit of detection at 0.009 ppm (linear range: 0.01 to 0.1 ppm), which is below the maximum permissible limit (i.e. 0.03 ppm). The fabricated electrode was responsible for sole conversion of U⁴⁺ into U⁶⁺ with a corresponding oxidation peak.