Collective Scattering of Light on Gold Nanospheres Dispersed in Diethylene Glycol Microdroplet

Light scattering on a freely suspended, evaporating droplet of suspension of gold nanospheres (125 nm radius) in diethylene glycol is studied, revealing both local and nonlocal properties of the system. When the average distance between the nanospheres at the droplet surface matches the wavelength of light, a (broad) maximum, associated with the collective scattering on them, is observed. The number of nanospheres at the droplet surface can be found then. A fine modulation of the maximum is associated with the whispering gallery modes of the composite droplet. The Fano profile identified in the modulation is interpreted as an interference of collective scattering and whispering gallery modes. The ultra narrow enhancement-and-quench structure recognizable in the modulation is interpreted as associated with the creation and destruction of collective oscillation of plasmons of individual nanospheres. It is proposed that this phenomenon can be perceived as whispering gallery modes-assisted creation and destruction of a global plasmon.