Silica-Based Nanohybrids Containing Dipyridine, Urethan, or Urea Derivatives

New nanohybrids were synthesized by grafting organosilanes on silica nanoparticles. These nanohybrids containing dibipyridine, urea, and urethan functionalities can be used as new synthons for nanotechnology, catalysis, or nanocomposites. The influence of the organosilane amount was studied together with the pH and solvent effects. The nanohybrids have been thoroughly characterized by diffuse reflectance IR Fourier transform (DRIFT) and NMR spectroscopies, electron microscopy (transmission and scanning), thermogravimetry (thermogravimetric analysis and differential thermal analysis), and nitrogen adsorption. We have demonstrated that grafting can occur in two ways on the silica surface: organosilane oligomer grafting or organosilane monolayer grafting. Through the synthesis of new organosilanes, containing dipyridine functionality combined with methylaminopropylsilane, interesting electronic and complexing properties are now available on the silica surface for further reactivity. This has been obtained for both triethoxysilyl and dimethylethoxysilyl derivatives with the same grafting ratio indicating that dimethylethoxysilane is a good precursor for developing nanohybrid chemistry. In this case, organosilane monolayer grafted nanoparticules were ascertained. Once grafted, the chemical integrity of ureas, urethan, and dipyridine silanes were preserved, as demonstrated by DRIFT and 13 C cross polarization magic angle spinning (CP MAS) NMR spectroscopies, and covalent grafting on silanol sites was confirmed by 29 Si CP MAS NMR experiments. The size and morphology of silica nanoparticles were retained after grafting as long as the organosilane-to-silica ratio did not exceed 2 mmol g −1, even in water or water/alcohol mixtures. This work demonstrates that it is possible to limit the grafting to lower oligomers, giving nanohybrids with very interesting chemical surface reactivity.