Abstract
A colloidal dispersion of uniform organosilica nanoparticles could be produced via the disassembly of the non-surfactant-templated organosilica powder nanostructured folate material (NFM-1). This unusual reaction pathway was available because the folate and silica-containing moieties in NFM-1 are held together by noncovalent interactions. No precipitation was observed from the colloidal dispersion after a week, though particle growth occurred at a solvent-dependent rate that could be described by the Lifshitz-Slyozov-Wagner equation. An organosilica film that was prepared from the colloidal dispersion adsorbed folate-binding protein from solution but adsorbed ions from a phosphate-buffered saline solution to a larger degree. To our knowledge, this is the first instance of a colloidal dispersion of organosilica nanoparticles being derived from a macroscopic material rather than from molecular precursors.
Highlights
Hybrid materials of nanostructured silica, organosilica, and organics can be used as precursors for porous materials or as vehicles for a controlled delivery of molecules and display useful optical and electronic properties.[1,2] The internal structures of such hybrid materials can be tuned by varying the fractions of their components as well as by moderating the intermolecular interactions among the components during the formation of the hybrid material
The nanostructured composite NFM-1 was synthesized from folic acid, Si(OEt)[4], and H2N(CH2)3Si(OEt)[3] in water.[3]
To better understand the contents of the dispersion and the factors influencing its formation, we examined the colloidal dispersion derived from NFM-1 in HCl(aq)−THF immediately after filtering
Summary
Hybrid materials of nanostructured silica, organosilica, and organics can be used as precursors for porous materials or as vehicles for a controlled delivery of molecules and display useful optical and electronic properties.[1,2] The internal structures of such hybrid materials can be tuned by varying the fractions of their components as well as by moderating the intermolecular interactions among the components during the formation of the hybrid material. Nanoparticles of silica, mesoporous silica, organosilica, and various hybrid materials are relevant to applications in biomedicine and other fields.[9−11] Their nanoscopic dimension allows them to be dispersed in solvents and to be assembled into mesoscaled structures, even in a crystalline manner.[12] Typically, organosilica particles are synthesized from smallmolecule organosilanes, RxSi(OR′)4−x (R may be a bifunctional bridge or contain other functional groups), under sol−gel conditions[10,13] in analogy to the Stöber approach that has been quite successful in the synthesis of monodisperse nanoscale particles of silica[14] and mesoporous silica.[15,16] The nanoscale dimension is controlled via the synthetic parameters (solvents, concentration, pH, etc.). Forming a layer on their surfaces, and the particles were less dense than expected for analogous silica particles Extending these studies, we here present a solution-based method to treat macroscopic powder of the mesostructured organic−organosilica−silica hybrid NFM-1 (Figure 1) to give a suspended silica-rich solid and dispersed nanoparticles; this constitutes the first synthesis of dispersed organosilica nanoparticles from a macroscopic organosilica material. The chemical composition and the stability of the dispersed nanoparticles were studied, as was the use of thin films derived from the coarsening dispersion in the microgravimetric detection of folate-binding protein (FBP)
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