Revealing the effect of Co/Cu (d7/d9) cationic doping on an electronic acceptor ZnO nanocage surface for the adsorption of citric acid, vinyl alcohol, and sulfamethoxazole ligands: DFT-D3, QTAIM, IGM-NCI, and MD analysis

Abstract

The electron-spin duality and propagation of the active sites of free electrons are of interest for adsorbing the guests and fixing them with strong hydrogen bonds (HB). The coherence of the systems with the guests is one of the main parameters that favor the experimentation of new systems on primary column adsorption phenomena. The stability and the adaptable symmetries in all directions justify the use of a “nanocage” (ZnO) for studying adsorption phenomena. The formation of stable electronic charge transfer paths between sites occupied by very stable atomic orbitals ensures the success of the adsorption of the ligands. Electronic characterization (MES, FMO, DOS, and cationic doping) is used to describe the movement of the intra-Cu-Co/Zn19O20 electrons. The phenomena of charge transfer, stability, types of orbital occupations, adsorption sites, electron migration direction, conductivity, and reactivity of such systems are thoroughly explored. Based on these findings, the efficiency of a Cu–Co/Zn19O20 nanocage to adsorb three different ligands (medical ligands, prostate biomarkers, and antibiotics) is studied. From the reactivity parameter discussions, it is found that the copper or cobalt-doped nanocage-Citric Acid has a strongly electronegative index (4.40 eV and 4.91 eV) and hardness (1.99 eV and 1.82 eV) properties. The Fourier transform infrared analyses and orbital localizations (α and β) clearly demonstrate that the charge transfer occurs inter-surface, from nanocages to adsorbed ligands. Bader’s theory analysis for the adsorption ligands VA (Vinyl Alcohol), CA (Citric Acid), and SMX (Sulfamethoxazole) by the doped copper and cobalt nanocages demonstrates that these systems are much more adequate for adsorbing the ligand antibiotics than the other hosts. The highly adsorbent energy of sulfamethoxazole by Cu–Zn19O20 is equal to − 582.86 kJ. mol-1. The IGM-NCI/ELF analyses support these findings, revealing that the Cu/Co–Zn19O20 nanocages adsorb SMX via hydrogen bonding and van der Waals interactions, as they also did in DFT-D3 and FT-IR analyses. LOL analyses support this claim by visualizing single-pair spins in excess surrounding acceptor atoms (O) in the two systems. Molecular dynamics simulations show that SMX is quickly adsorbed by nanocages of Zn19O20 doped with copper (d9) or cobalt (d7).