Effects of near-field electromagnetic coupling in dimers of nanoparticles with a silver core and a J-aggregate dye shell

We report a theoretical study of the plasmon–exciton coupling effect on the absorption spectra of pairs of closely spaced double-layer hybrid nanoparticles consisting of a metallic core and a J-aggregate dye shell. The effect of frequency conversion of plasmonic lines due to the near-field interaction between plasmons and Frenkel excitons of the organic shell is demonstrated. The effect leads to the appearance of additional spectral lines in the longwavelength part of the spectrum of the system of hybrid particles. The shapes and the relative intensities of the additional lines exactly reproduce the specific features of the original spectrum of plasmonic absorption bands in uncoated metallic nanoparticles. The discovered phenomenon can be used to design new types of highsensitivity nanosensors, based on plasmon–exciton effects and principles of near-field optics.