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APTS-modified silicon dioxide using different methods, APTS layer structure has generated a variety of characterization methods significantly different, the researchers have used infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance and elemental analysis APTS layers were characterized to give the modification amount APTS, APTS layer thickness, density amino, bonding structure information.

How to determine the amount of APTS-modified silicon dioxide surface is very important. There are many methods to characterize the amount of modification APTS, elemental analysis is an effective method, which can accurately given surface C, H, N elements amount to calculate the amount of modification of APTS. Elemental analysis method is susceptible to interference as water, ethanol and other substances in the sample preparation and sample testing process to fully dry, avoid contact with the air thus reducing test errors. Gimpel and Unger et titration method for the determination of the amount of the APTS modification: After modification of silica with ethanol APTS after washing to remove unreacted APTS, added NaCl and HCl solution 012molPL of 015molPL will aminopropyl APTS layer protonation, ethanol solution and then washed to remove excess NaCl and HCl, then washed with 015molPL of Na2SO4, the supernatant was collected and washed with 011molPL AgNO3 titration of the supernatant was washed Cl-1, calculated by the silica surface APTS amount of Cl-1 modification amount.

Walcarius Panel adopts acid-base titration method for the quantitative amount APTS modifications: toluene phase APTS-modified silicon dioxide dispersed in water, with HCl solution titration 10-2molPL and record the pH of the solution, with the addition of HCl the amount of horizontal, vertical axis as the pH value of the titration curve. During the titration, HCl reacted first with free amino group (3) occurs when the free amino fully protonated, appears first reaction equilibrium point; while continuing to join HCl, HCl and the protonated amine further reaction (4), when when the reaction is complete, the emergence of the second reaction equilibrium.


 

 

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