Perylene dye@SiO2 core–shell nanoparticles with intense fluorescence

Abstract

PD/CC@SiO₂ core–shell nanoparticles (PD: perylene dye, CC: cholecalciferol/vitamin D₃) were prepared using a water-based injection method. Specifically, a solution of the PD (fluorescent red (FR), fluorescent orange (FO), fluorescent yellow (FY)), CC, and octyltriethoxysilane (OTES) as a silica precursor in ethanol was injected in water at 70 °C and pH 5. The core–shell nanoparticles exhibited an outer particle diameter of 29 ± 11 nm and an inner core of 12 ± 4 nm. Suspensions (up to 10 mg mL⁻¹) were colloidally highly stable due to the negative surface charging (−40 to −50 mV). CC efficiently allowed disturbing of the π-stacking of the PD, such that, e.g., FR/CC@SiO₂ nanoparticles with 10 wt% FR showed intense emission with quantum yields near unity (98%) and without any concentration quenching. In contrast to the freely-dissolved dyes, PD in the nanoparticle core did not show any photobleaching even after 20 hours of continuous UV illumination (280 nm). As proof-of-the-concept, suspensions and thin films were realised showing intense emission from red to yellow. Exemplarily, FR/CC@SiO₂ core–shell nanoparticles were examined in detail, including electron microscopy, element mapping, dynamic light scattering, infrared spectroscopy, elemental analysis, UV-Vis spectroscopy, and photoluminescence spectroscopy.