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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 10
BKCSDE 32(10)
October 20, 2011 

Multinuclear Solid-state NMR Investigation of Nanoporous Silica Prepared by Sol-gel Polymerization Using Sodium Silicate
Sun Ha Kim, Oc Hee Han,*, Jong Kil Kim, Kwang Ho Lee
Silica, Nuclear magnetic resonance, MAS NMR, Surface functionalization
Multinuclear solid-state nuclear magnetic resonance (NMR) experiments were performed to investigate the local structure changes of nanoporous silica during hydrothermal treatment and surface modification with 3- aminopropyltriethoxysilane (3-APTES). The nanoporous silica was prepared by sol-gel polymerization using inexpensive sodium silicate as a silica precursor. Using 1H magic angle spinning (MAS) NMR spectra, the hydroxyl groups, which play an important role in surface reactions, were probed. Various silicon sites such as Q2, Q3, Q4, T2, and T3 were identified with 29Si cross polarization (CP) MAS NMR spectra and quantified with 29Si MAS NMR spectra. The results indicated that about 25% of the silica surface was modified. 1H and 29Si NMR data proved that the hydrothermal treatment induced dehydration and dehyroxylation. The 13C CP MAS and 1H MAS NMR spectra of 3-APTES attached on the surface of nanoporous silica revealed that the amines of the 3-aminopropyl groups were in the chemical state of NH3 + rather than NH2.
3644 - 3649
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