Raman bands in Ag nanoparticles obtained in extract of Opuntia ficus-indica plant

• ΑgNP nanoparticles obtained by an extract of plant.
• Raman bands observed in AgNP.
• Vibration modes determined from DFT calculations in agreement with experimental results.
• Breathings modes in small Ag clusters.

Silver nanoparticles have been obtained in an extract of Opuntia ficus-indica plant. The size and distribution of nanoparticles were quantified by atomic force microscopy (AFM). The diameter was estimated to be about 15 nm. In addition, energy dispersive X-ray spectroscopy (EDX) peaks of silver were observed in these samples. Three Raman bands have been experimentally detected at 83, 110 and 160 cm−1. The bands at 83 and 110 cm−1 are assigned to the silver–silver Raman modes (skeletal modes) and the Raman mode located at 160 cm−1 has been assigned to breathing modes. Vibrational assignments of Raman modes have been carried out based on the Density Functional Theory (DFT) quantum mechanical calculation. Structural and vibrational properties for small Agn clusters with 2≤n≤9 were determined. Calculated Raman modes for small metal clusters have an approximation trend of Raman bands. These Raman bands were obtained experimentally for silver nanoparticles (AgNP).