Covalently functionalized uniform amino-silica nanoparticles. Synthesis and validation of amine group accessibility and stability

This paper describes the synthesis and characterization of colloidally stable, 18 nm silica nanoparticles that are functionalized with amine groups. Electron microscopy, small-angle X-ray scattering (SAXS), and dynamic light scattering show the amine grafting does not impact particle size. SAXS and DLS confirm the particles do not aggregate at 10 mg mL(−1) and pH 2 for 30 days. Ninhydrin analysis, fluorescamine binding, and NMR studies of carboxylic acid binding show that the amines are present on the surface and accessible with maximum loading calculated to be 0.14 mmol g(−1). These materials should find a range of use in nanotechnology applications.