Surface plasmon absorption study of silver NP thin film containing 2,2′-bipyridine

The fine tuning of localized surface plasmon resonance (LSPR) of Ag-NP film containing 2,2′-bipyridine (bipy), self-assemble at room temperature when solution cast from dispersions on the glass substrate is described. The suspension of Ag colloid was prepared via polyol reduction stabilization using microwave radiations. SEM, EDS study reveals that NPs are uniform in size and reduced to metallic Ag. The cooperative SPR (approx. at 418 nm) of 2D assembly has been depressed due to 2,2′-bipyridine ligand structured around Ag-NPs showing red shift (456 nm). The cooperative resonance can be controlled by varying impingement time of microwave power on film. As the impingement time increased co-operative resonance begins blue shift due to increase in the cooperative interaction between Ag-NPs via decomposition of bipyridine. The co-operative resonance of 2D assembly that is at 418 nm was regained after complete removal of 2,2′-bipyridine at higher temperatures thus showing tunable LSPR properties of Ag-Bipy nanostructure. Opposite type of behavior that is strong damping were seen in case of Ag-NPs in solution phase. Temperature dependent viscosity characteristics suggest that Plasmon damping can be attributed to decrease in viscosity of Ag-NP solution.