Decrease of surface to volume ratio in spherical nanoparticles led to red-shift in SPR diagram. But in same size nanoparticles, shape alteration, from sphere to cube, with respect to increase of surface to volume ratio, caused red-shift in SPR diagram. It means there are other factors could have an affect on the SPR.
SPR is the excitation of surface electrons. Increase in size will lead the red shift means decrease in the surface electrons
SPR is the excitation of surface electrons. Increase in size will lead the red shift means decrease in the surface electrons
On changing the shape from Cube to sphere because the cube has several distinct symmetries for dipole resonance compared with only one for the sphere and it has been seen that the most intense peak is red-shifted compared with that of the sphere, a phenomenon often observed for nano-structures with sharp corners. It is due to surface charges accumulation at sharp corners and this segregation of charges into corners increases charge separation so thereby reduces the restoring force for electron oscillation. The weaker restoring force in turn manifests itself in a red-shift of the resonance peak.
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