Computational investigation of pristine, Al-, and Ga-doped Zn12O12 nanoclusters as detection platforms for methadone in gas and solvent phases

Electrochemical sensors are emerging as promising tools for point-of-care diagnostic medical devices, benefiting from advancements in nanomaterials. These nanomaterials enable the development of smaller, more sensitive, and selective sensors while reducing fabrication and maintenance costs. This work presents a comprehensive theoretical investigation of the potential application of pristine, Ga- and Al-doped Zn₁₂O₁₂ nanoclusters for detecting methadone, a critical analyte in various medical and law enforcement applications. Employing density functional theory (DFT) calculations at the B3LYP-D level with the 6–311 G (d, p) basis set, we have elucidated the interactions between these nanoclusters and methadone. The results reveal that methadone exhibits intense adsorption energies of -41.02, -39.79, and -59.77 kcal/mol on the pristine Zn₁₂O₁₂, GaZn₁₁O_12, and AlZn₁₁O₁₂ nanoclusters, respectively, in their most stable configurations. The doped nanoclusters, GaZn₁₁O₁₂ and AlZn₁₁O₁₂, displayed significant gap energies (E_g) changes upon methadone adsorption, indicating enhanced sensitivity towards this analyte. The UV–Vis spectroscopic analysis showed that methadone adsorption on the GaZn₁₁O₁₂ and AlZn₁₁O₁₂ nanoclusters led to distinct spectral shifts and oscillator strength variations compared to the Zn₁₂O₁₂ nanocluster. The transition theory calculations highlighted the GaZn₁₁O₁₂ nanocluster's short recovery time of 0.44 s, a crucial attribute for practical applications. Solvent effect studies demonstrated the stability of the methadone/GaZn₁₁O₁₂ complex in water and revealed its heightened polarization, as evidenced by the increased dipole moment. These findings suggest that the GaZn₁₁O₁₂ nanocluster is a promising candidate for detecting methadone in gas and liquid phases, with favorable attributes such as high sensitivity, rapid reversibility, and stability in gas and aqueous environments. Thus, this nanocluster can be used in sensor devices.