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NMR spectroscopy can be given a specific chemical environment APTS modified sample surface atoms of the silicon dioxide, and thereby obtain information about the state of bonding layer APTS and amino APTS state with the silica surface and between the APTS. After Satu and other vapor deposition method silica surface modified with APTS, characterized by SiCPPMASNMR APTS bonding state of Si atoms.

Linde and Chu et al studied the use 13CCPPMASNMR in toluene under anhydrous conditions APTS-modified silicon dioxide reaction process amino interaction with the silica surface. By APTS molecule atom chemical shift B2C identified amino silica surface may occur three kinds of interactions: between the amino and hydroxyl groups of silica surface of the silicon hydrogen bond interactions; amino silica surface hydroxyl groups of silicon proton transfer after the formation of an ionic interaction; hydroxyamino silicon autocatalytic APTS molecules form hydrogen bonds with the silica surface condensation to form Si) O) Si covalent bond. Based on the results of these experiments Linde et flipping mechanism proposed toluene under anhydrous conditions in the reaction with the silica APTS: first APTS forming hydrogen binding to the silica surface silanol groups via an amino group to the silica surface, wherein the portion hydrogen bond proton transfer and a stronger ionic interaction, this time with an amino group of the surface binding and ethoxylated APTS exposed surface; heat curing treatment after reaction and after the reaction in toluene, and the next amino autocatalysis APTS silica surface silanol condensation forming Si) O) Si covalent bond, an amino group after release Si) O) Si bond is formed, after inversion APTS amino exposed surface. Chu and other used 15NCPPMASNMR further confirms this reversal mechanism.

After silica surface modified by APTS, the alkaline amino on APTS affect the APTS modification of silica chemical stability. Waddell after APTS modification of silica in toluene, placed after the APTS modification of silica in ethanol, found placed after a period of time, take samples of the clear liquid to join excessive salicylaldehyde ethanol solution, the solution will become a bright yellow. This suggests that the silicon dioxide surface APTS in ethanol solution understand from happening, disintegrate the APTS react with salicylaldehyde became yellow schiff base. Generated by the schiff base have absorption peak at 404 nm, the peak at 404 nm to monitor APTS dissociation degree in ethanol solution. Vrancken APTS, etc with a known concentration of salicylaldehyde with excessive reaction, using ultraviolet absorption spectrum made APTS standard curve, which can quantitatively detecting APTS in ethanol solution from the amount of the actual solution. Adopt the method of similar to Vrancken work, Markowitz with fluorescent amine as markers to determine the amount of APS dissociation.

 

 

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