Enhanced sensing performance of carboxymethyl cellulose sodium to hydrogen sulphide gas and methylene blue dye by constructing CuO@ZnO core/shell heterostructure: A DFT/TD-DFT study

Abstract Anthropogenic air and water pollution are two of the world's most serious public health threats, causing around 9 million fatalities each year. Accordingly, CuO, ZnO, and CuO@ZnO core/shell structures were optimized utilizing the time-dependent density functional theory (TD-DFT) method to study the effect of CuO@ZnO core/shell on the sensitivity of carboxymethyl cellulose sodium (CMC). Absorption spectra and optical band gap (E g ) have been investigated utilizing the TD-DFT method. The calculated E g values for CuO and ZnO equal 1.23 and 3.29 eV, respectively, which agree well with those reported in the literature. The effects of H 2 S gas and methylene blue dye (MB) adsorption on the electronic characteristics of dimer CMC /CuO@ZnO structures were investigated in terms of TDM, HOMO/LUMO energy, and molecular electrostatic potential (MESP). The TDM in dimer CMC/CuO@ZnO structure was increased to 72.152 and 67.606 Debye, while ΔE was reduced by 6.42% and 82.57% due to the adsorption of H 2 S and MB dye, respectively. This means that it has a faster response to MB than to H 2 S. Additionally, MESP confirms the increased reactivity of dimer CMC/CuO@ZnO due to the adsorption process. As a result, dimer CMC/CuO@ZnO structures appear to be attractive candidates for H 2 S and MB dye sensing applications.