The characteristics of Raman spectroscopy of isomer CBD- and THC-Au nanoparticles using the density functional theory

The isomers cannabidiol (CBD) and D9-tetrahydrocannabinol (THC) can both be extracted from cannabis. We use density functional theory to study the Raman activity spectra, frontier molecular orbitals, and molecular electrostatic potentials of CBD, THC, and their respective gold complexes. A selectivity enhancement phenomenon for the spectral peaks at frequencies of 1144 cm(-1) and 1553 cm(-1) in the Raman spectrum of the CBD-Aun complex, and at frequencies of 865 cm(-1), 1335 cm(-1), and 1553 cm(-1) in the Raman spectrum of the THC-Au-n complex, was observed and explained. The frontier molecular orbital energy gaps of CBD and THC are 5.4085 eV and 5.4461 eV, respectively, indicating that CBD is more likely to react than THC. The CBD/THC-Au complexes had the strongest chemical activities and greater charge transfer effects with an Au-3 cluster. The most electronegative sites of CBD and THC were found from molecular electrostatic potential (MEP) mapping. It is assumed that these sites are the adsorption sites of the CBD/THC molecules and gold surface. The MEP of the CBD/THC complexes also demonstrates the charge transfer effect between CBD/THC and Au. Both the selectivity phenomenon in the Raman activity spectra of the complex and the above assumption are explained by a surface selection rule. The conformation of the CBD/THC molecules on the gold surface are determined, showing that CBD is adsorbed vertically through the resorcinol structure while THC is adsorbed vertically through the tetrahydropyran and benzene ring. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this study, the Raman activity spectra, frontier molecular orbitals, and molecular electrostatic potentials of CBD, THC, and their respective gold complexes were investigated. The results show that CBD is more reactive than THC, with CBD/THC-Au complexes displaying stronger chemical activities and greater charge transfer effects. The most electronegative sites of CBD and THC were identified as the adsorption sites on the gold surface.