Optical Properties and Radial Breathing Modes Present in Cu Amorphous Quantum Dots Obtained by Green Synthesis

Colloidal copper quantum dots with amorphous structure have been obtained by green synthesis using the extract of the plant Opuntia ficus-indica. The quantum dots obtained had a size of approximately 1 nm. The optical properties studied have shown a band in the absorption spectrum centered at 550 nm, originated by plasmon resonance. The broad width of the absorption band is discussed in terms of electronic excitations by Density Functional Theory (DFT) calculations. The Raman spectrum of the sample also presented a Raman band to low wavenumbers centered at 273 cm(-1). Additionally, DFT was employed to study the vibrational modes present in minimum energy copper clusters (Cu-n, n = 3-12). The Radial breathing modes were found between 270-330 cm(-1), in low-energy structures of Cu.