15 N CP/MAS NMR as an instrument in structure investigations of organosilicon polymers

Brendler, Erica; Ebrecht, E.; Thomas, B.; Boden, G.; Breuning, T.

doi:10.1007/s002160051168

Cited by 6 publications

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“…Experimentally, the chemical shifts observed in these glasses are found to range from −270 ppm to −317 ppm and they correlate to −N and >N-. , While we have not conducted experiments to assign the signals detected in 15 N-amino modified TiO 2 uniquely, reasonable assignments can be made by comparison to well-characterized N-containing polymeric, ceramic, and glassy systems. For instance, the 15 N signals of organosilicon and silazane (NSiH, NSiH 2 , NSi 3 ), and borazine (BNH, BNH 2 , BN) polymers have specifically been assigned to the number of nearby protons using inversion recovery cross-polarization (IRCP) experiments. − These studies have determined that the low-field signal is normally tricoordinated N with no hydrogen atoms attached, while the −NH 2 and −NH functionalities are the high field signal. Also, in preceramic graphitic carbon nitride ( g -C 3 N 4 ) materials the different CN x H y aminate groups observed by 15 N IRCP have been assigned to NH, NH 2 , and tertiary N and their chemical shifts follow the same trend …”

Section: Discussionmentioning

confidence: 99%

¹⁵N Solid State NMR and EPR Characterization of N-Doped TiO₂ Photocatalysts

et al. 2007

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The solid-state nuclear magnetic resonance (SSNMR) analysis and structural characterization of N-doped TiO2 nanoparticle and monolayer materials suitable for visible photocatalysis is reported. The SSNMR analysis of 15N-doped TiO2 synthesized using 15N-urea before calcination indicates formation of various amino functionalities of the type NH, NH2, NH3, and probably NH4 +, while the NMR spectrum of the yellow powder that results from high-temperature calcination shows that these nitrogen species oxidize to form nitrate. These and nonisotopically labeled materials were characterized also by X-ray diffraction, UV−vis, and electron paramagnetic resonance spectroscopy. Monitoring the oxidation of 1,2-13C-trichloroethylene (TCE), photochemical activity was confirmed by monitoring the production of CO2 by 13C NMR analysis. The powdered form of N-doped TiO2 proved to be a highly efficient visible light catalyst by oxidizing all of the TCE to chlorinated alkyl and acyl containing molecules along with CO2. The performance of a TiO2−N−TiO2/porous Vycor 7930 borosilicate glass monolayer catalyst was in turn evaluated by monitoring the photochemical oxidation of ethanol and acetone with UV−vis light, and it was found to perform better than TiO2-only monolayers. Direct nitridation of TiO2 powders and monolayers also was conducted to compare the 15N SSNMR and to discern if there is a nitridic bond in these materials. The SSNMR results provide more evidence supporting the hypothesis that the nitrogen atom in N-doped TiO2 is present in interstitial sites when N is in a highly oxidized state.

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Section: Discussionmentioning

confidence: 99%

¹⁵N Solid State NMR and EPR Characterization of N-Doped TiO₂ Photocatalysts

et al. 2007

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“…Overlapping between two bonds occurs after the formation of crosslinked bonds in the pyrolysis of hydroborated polyhydridovinylsilazane. 15 N chemical shifts at 56.0 ppm and 41.0 ppm reported in the literature attribute to the formation of two kinds of bonds: Si-N-Si and Me 3 Si-N-B, respectively[26].…”

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confidence: 92%

Synthesis and pyrolysis of novel polysilazane to SiBCN ceramic

JongSang

Butt

Baney

et al. 2005

Journal of Non-Crystalline Solids

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“…An additional narrow signal of small intensity at -341 ppm is due to remaining small amounts of crystalline NH 4 Cl. 34 Own investigations 35 and the comparison with literature data 26,34,36,37 lead to the conclusion that the 15 N chemical shift is often strongly influenced by the next nearest neighbors. Thus, the values cannot simply be transferred from one system to another.…”

Section: Resultsmentioning

confidence: 99%

Interaction of Polychloromethylsilanes with Ammonia and Ammonium Chloride

et al. 2004

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Polychloromethylsilanes were reacted with ammonia at various temperatures and pressures to achieve shape stabilization of preceramic green fibers. Besides the aspired cross-linking process, other reactions took place due to the interaction with NH4Cl, deposited as a byproduct at the polymer surface. FT/IR, 13C, 29Si, and 15N solid-state NMR investigations and X-ray powder diffraction were applied to follow the dynamics of the reaction and to characterize the obtained products. They prove that during annealing under argon back reactions occur. With annealing under ammonia, pressures up to 4 bar and temperatures >200 °C completely rearrange the polysilane into a polysilazane skeleton. The resulting silazane exhibits a cagelike structure. Reactions causing this rearrangement are discussed.

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15 N CP/MAS NMR as an instrument in structure investigations of organosilicon polymers

Cited by 6 publications

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¹⁵N Solid State NMR and EPR Characterization of N-Doped TiO₂ Photocatalysts

¹⁵N Solid State NMR and EPR Characterization of N-Doped TiO₂ Photocatalysts

Synthesis and pyrolysis of novel polysilazane to SiBCN ceramic

Interaction of Polychloromethylsilanes with Ammonia and Ammonium Chloride

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15 N CP/MAS NMR as an instrument in structure investigations of organosilicon polymers

Cited by 6 publications

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15N Solid State NMR and EPR Characterization of N-Doped TiO2 Photocatalysts

15N Solid State NMR and EPR Characterization of N-Doped TiO2 Photocatalysts

Synthesis and pyrolysis of novel polysilazane to SiBCN ceramic

Interaction of Polychloromethylsilanes with Ammonia and Ammonium Chloride

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¹⁵N Solid State NMR and EPR Characterization of N-Doped TiO₂ Photocatalysts

¹⁵N Solid State NMR and EPR Characterization of N-Doped TiO₂ Photocatalysts