au/ag bimetallic nanocomposites as a highly sensitive plasmonic material

We report au/ag bimetallic nanocomposites as a highly sensitive plasmonic material. a unit approach via a three-dimensional numerical modeling is introduced to observe collective plasmon resonance in au/ag bimetallic nanocomposites as well as au mono-metallic nanoensembles. au nanoensembles provide consistently identical plasmon wavelength, independent of inter-unit distance. in analogy with mono-metallic nanoensembles, au/ag bimetallic nanocomposites distinctly feature converging dual plasmon resonance peaks to a single plasmon resonance peak, strongly depending on the packing density and the unit size. an effective unit size of bimetallic nanocomposites is below 2.5 nm in a subwavelength structure, which is small enough to feature bimetallic nanocomposites. as a result, the au/ag bimetallic nanocomposites clearly show exceptionally high sensitivity and figure-of-merit (approximately 3-fold of conventional plasmon sensitivity and 4.3-fold of conventional plasmon fom), resulting from coupled au-ag quadrupole bimetallic nanounits. this study provides essential rationales for au/ag bimetallic nanocomposites serving as a desirable and alternative plasmonic material for advanced nanoplasmonic-sensing technologies.