Optical properties of copper clusters in zeolite 4A with surface enhanced Raman spectroscopy applications

• Published in: Applied physics. A, Materials science & processing Vol. 128; no. 8
• Main Authors: Leal-Perez, J. E., Flores-Valenzuela, J., Cortez-Valadez, M., Hurtado-Macías, A., Vargas-Ortiz, R. A., Bocarando-Chacon, J. G., Almaral-Sánchez, J. L.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2022; Springer Nature B.V
• Subjects: Absorption spectra; Applied physics; Characterization and Evaluation of Materials; Charge transfer; Clusters; Condensed Matter Physics; Copper; Density functional theory; Electron transfer; Electron transitions; Electronegativity; Ion exchange; Machines; Manufacturing; Materials science; Methylene blue; Molecular orbitals; Nanotechnology; Optical and Electronic Materials; Optical properties; Physics; Physics and Astronomy; Processes; Raman spectroscopy; Spectrum analysis; Substrates; Surface chemistry; Surfaces and Interfaces; Thin Films; Zeolites; Zeolite 4A; Theoretical and experimental analysis; Copper ions; Chemical enhancement mechanism
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-022-05785-6

In this study, we used the ion exchange properties of zeolite 4A to stabilize copper ionic species. These species showed absorption bands in the ultraviolet region between 210 and 320 nm. Complementarily, DFT (Density-Functional Theory) at different levels of approximation was employed in combination with the LANL2DZ (Los Alamos National Laboratory 2 double zeta) and SDD (Stuttgart/Dresden) basis sets to find hints of optical absorption behavior associated with electronic transitions. The copper clusters in ZA were evaluated as SERS (Surface-Enhanced Raman Spectroscopy) substrate using pyridine (Py) and methylene blue (MB) molecules. Additionally, molecular descriptors as electron transfer factor, electronegativity and global hardness were considered to study the charge transfer between the molecular systems and the ionic copper species. The DFT calculations suggest that the Cu 3 + cluster manifests optically. The molecular descriptors allowed to identify the effect of charge transfer from the analyte to the cluster, specifically toward the LUMO or higher energy orbitals, and the systems obtained showed capacity as SERS substrates, evaluated on Py and MB.