Stability, spectroscopic, electrochemistry and QTAIM analysis of Cu-Zn(n−1)O(n) clusters for glucose sensing application: A study on theoretical and experimental insights

Clusters of (ZnO)(n) (n = 2–4) have been shown to play a central role in the detection of glucose entity based on the existence of photo-induced electrons (PE), which facilitates the interaction between (ZnO)(n) clusters and glucose entity guests. The electrochemistry experiment has confirmed the detection of glucose by the title clusters. The optimization, energetic parameters, and vibrational frequency calculations have indicated that the Cu-Zn(n−1)O(n)-glucose are more stable than the (ZnO)(n)-glucose complexes. It has been demonstrated that the Cu doping enhanced the chemical behavior of the clusters and formed a high intramolecular charge transfer (ICT) in the system. The glucose sensing by all the forms of Cu-Zn(n−1)O(n) clusters showed that the Cu–Zn(3)O(4), Cu-Wurtzite, and Cu-Rocksalt clusters are the most suitable for adsorbing the glucose guest. The HOMO/LUMO iso-surfaces of the complexes showed that the electron concentrations are localized in the d orbitals and mainly in the form of the d(10) orbitals around Zn atoms. The molecular electrostatic potential (MEP) has clearly indicated that a high charge transfer occurs between the copper and the oxygen atoms, which facilitate the adsorption of glucose. The reactivity parameters also indicated that the Wurtzite-glucose complex has a high electrophilicity index (ω), which means a good acceptor behavior to interact with glucose. Additionally, the bond between the (ZnO)(n) clusters and the glucose polar element has been studied in detail by using QTAIM theory. Finally, the theoretical and experimental studies prove that the Cu-Zn(n−1)O(n) clusters are very suitable and competent compounds for detecting glucose.