Mg-Containing Zn3O3 Structures for Detection of CO2: A DFT Study on CHEM Effects of SERS and Electronic Properties

Surface-enhanced Raman spectra (SERS)and electronic-structure-basedproperties are important tools for investigation of the molecularsensing ability of nanoparticles. The present computational studyis intended to explore the sensing ability of Zn3O3 and Mg-containing Zn3O3 structuresfor CO2 molecules by CHEM effects of the SERS technique.Geometries of CO2-adsorbed Zn3O3,Zn2MgO3 (Mg as a substitutional impurity), andZn(3)O(3)Mg (Mg as an interstitial impurity) structuresare modeled using the B3LYP/6-31G(d,p) level of density functionaltheory. The Mg site of the Zn2MgO3 and Zn3O3Mg structures is preferential for the adsorptionof CO2. The observed energy trends are supported by geometricalanalysis, molecular orbital interactions, redshifts in CO2 vibrational modes, and topological properties. Raman activity enhancementof the CO2 symmetric vibrational mode is significant whenthe molecule is adsorbed at the Mg site of Zn3O3Mg. The observed Raman activity enhancement is supported by SERSspectra obtained from anharmonic calculations carried out on B3LYP/6-31G(d,p)geometries and substantiated by a larger change in the polarizabilitywith energy corresponding to the symmetric vibrational mode of CO2. The TDDFT calculations, frequency-dependent polarizabilities,and charge transfer interactions show that Zn3O3Mg is a good substrate for sensing of CO2, with visiblewavelengths, by resonance Raman effect. The trends with adsorptionenergy, Raman activity, and excited state properties are also substantiated by B3LYP/6-311+G(d,p) calculations.