Computational investigations on the 4-cyanopyridine adsorbed on ZnO-graphene oxide nanocomposite toward the efficient performance of surface-enhanced Raman scattering

The structural, energetic, and Raman vibrational properties of adsorbed 4-cyanopyridine (4-CNP) on the Zn12O12 and Zn12O12-graphene oxide (GO) substrates are investigated using the dispersion corrected density functional theory (DFT-D3). The 4-CNP is chemisorbed on Zn12O12 and Zn12O12-GO at the Zn atom through its pyridine N atom with interaction energies of about-1.492 and-1.436 eV, respectively. Humidity played trivial role in adsorption properties whereas dispersion forces affected interaction energy of adsorbed 4-CNP on the Zn12O12. Various functionals with different Hartree-Fock exchange gave different electronic properties for adsorbed 4-CNP on the Zn12O12. For both complexes, the N...Zn interaction was recognized to be electrostatic attraction and partly covalent bonding in nature using the AIM analysis. The calculated vibrational wavenumbers and intensities of Raman spectra of isolated 4-CNP, 4-CNP/Zn12O12, and 4-CNP/Zn12O12-GO complexes with DFT-D3 showed that the bonding mode of 4-CNP contribute significantly to the estimated Raman scattering enhancement. These findings are helpful for the effective performance and possible improvement of the surfa-ce-enhanced Raman scattering technique for semiconducting substrates tuning the ultrasensitive approaches for detection of single molecules.