Vibrational frequency of the silver nanomaterial

A quantitative model for size-dependent vibrational frequency of nanomaterial explained by the quasispherical approach. We studied the variation of vibrational frequency with the change in cluster size. The maximum change in vibration frequency occurs within the size D < 30 nm, cos of the large surface/volume of that size. It is demonstrated that the vibrational frequency of nanomaterials decreases by increasing the cluster size for a positive sign while it increases with increasing the size for negative sign. It is found that the vibrational frequency of Silver (Ag) nanomaterial increases rapidly in smaller cluster size and then the rate of decrement becomes slower and tends to unity on increasing the cluster size. A blue shift (material lattice is compressed the Raman shift increases so it gains energy i.e. blue shift) occurs with +ve sign due to the lattice deformation while redshift (Heating, contraction of materials leads to frequency decrease i.e. redshift) occurs with -ve sign. Therefore, we concluded that the vibrational frequency of nanomaterials does not show a universal trend with size. Reasonable agreement between the experimental data and finding of our model for vibrational frequency has been found.