title: Synthesis of ultrabright nanoporous fluorescent silica discoids using an inorganic silica precursor.
abstract: The templated sol-gel synthesis of ultrabright fluorescent nanoporous silica particles based on the use of organic silica sources has previously been reported. The use of organosilanes as the main silica precursors has a number of issues, in particular, the low robustness of the synthesis due to instability of the organic silica source. Here we report on a novel synthesis of ultrabright fluorescent nanoporous silica discoids (a specific shape in-between the sphere and disk) of 3.1 ± 0.7 microns in size, which were prepared using a stable inorganic sodium silicate silica source. Organic fluorescent dye Rhodamine 6G (R6G) was physically (non-covalently) entrapped inside cylindrical nanochannels of ∼4-5 nm in diameter. In contrast to the synthesis with organic silica precursors, the obtained particles showed an excessive leakage of dye. To prevent this leakage, we modified the synthesis by adding a small amount of a secondary silica source. The synthesized particles show virtually no leakage, high photostability, and a brightness equivalent to the fluorescence of up to 7 × 10(7) free R6G molecules. This is about 7 times higher than the fluorescent brightness of particles of the same size made of CdSe/ZnS quantum dots, and 420 times higher than the brightness of the same volume of aqueous solution of free R6G dye.
authors.affiliation: Department of Physics, Clarkson University, Potsdam, NY 13699-5820, USA.
authors.forename: Dmytro O
authors.initials: DO
authors.lastname: Volkov
authors.forename: Eun-Bum
authors.initials: EB
authors.lastname: Cho
authors.forename: Igor
authors.initials: I
authors.lastname: Sokolov
mesh_terms: D007287:Inorganic Chemicals / Q000138:chemical synthesis*; D008163:Luminescent Measurements / Q000379:methods*; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D016062:Porosity; D012235:Rhodamines / Q000737:chemistry*; D012822:Silicon Dioxide / Q000138:chemical synthesis*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013499:Surface Properties
chemical_list: D007287:Inorganic Chemicals; D012235:Rhodamines; C026188:rhodamine 6G; D012822:Silicon Dioxide