Polymorphism of CMONS Nanocrystals Grown in Silicate Particles through a Spray-Drying Process

The preparation of core-shell nanoparticles constituted by organic nanocrystals embedded in amorphous organosilicate shells is based on the controlled drying of micrometer-sized droplets produced from the atomization of sol-gel solutions. This leads to the formation of an organosilicate crust at the first stage of the droplet drying, followed by the confined nucleation and growth of dye nanocrystals in the cores of the resulting silicate particles. We selected CMONS as model dye because it is strongly fluorescent, only in the crystal state. To specify the coupled effects of confined nucleation and growth and that of the nature of silicate matrix on crystallinity and polymorphism of CMONS nanocrystals, we characterized the core-shell nanoparticles by electron microscopies and absorption, fluorescence and second-harmonic generation (SHG) spectroscopies. This polymorphism control of CMONS nanocrystal allows enhancing and tuning their fluorescence and second harmonic generations. This is promising for the development of biological tracers involving fluorescence excited by two-photon absorption.