NMR Characterization of Phosphonic Acid Capped SnO2 Nanoparticles
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- 作者：Gregory P. Holland ; Ramesh Sharma ; Jacob O. Agola ; Samrat Amin ; Virgil C. Solomon ; Poonam Singh ; Daniel A. Buttry ; Jeffery L. Yarger
- 刊名：Chemistry of Materials
- 出版年：2007
- 出版时间：May 15, 2007
- 年：2007
- 卷：19
- 期：10
- 页码：2519 - 2526
- 全文大小：280K
- 年卷期：v.19,no.10(May 15, 2007)
- ISSN：1520-5002
文摘
Phosphonic acid capped SnO2 nanoparticles with diameters less than 5 nm were synthesized andcharacterized with multinuclear solution and solid-state magic angle spinning (MAS) NMR. Two typesof phosphonic acid ligands were used to derivatize the SnO2 surface, producing (i) water soluble SnO2nanoparticles capped with 2-carboxyethanephosphonic acid (CEPA) and (ii) insoluble SnO2 nanoparticlescapped with phenylphosphonic acid (PPA). Multiple surface environments were observed with 31P solutionand solid-state MAS NMR for both capping agents. The 31P resonances of derivatized SnO2 nanoparticlesdisplay isotropic chemical shifts that are more shielded compared to the native phosphonic acids.This observation is indicative of a strong interaction between the phosphonic acid group and the SnO2surface. 1H MAS NMR spectra display a complete absence of the acidic protons of the phosphonic acidgroups, strongly supporting the formation of P-O-Sn linkages. 1H 
31P cross polarization (CP)build-up behavior confirms the absence of the vast majority of phosphonic acid protons. Some of thebuild-up curves displayed oscillations that could be fit to extract the magnitude of the 1H-31Pdipolar coupling constant. The dipolar coupling can then be used to calculate the distance betweenphosphorus and the close proximity protons. The results presented herein indicate primarily bi- andtridentate phosphonic acid bonding configuration at the SnO2 surface, in both CEPA and PPA cappednanoparticles.
31P cross polarization (CP)build-up behavior confirms the absence of the vast majority of phosphonic acid protons. Some of thebuild-up curves displayed oscillations that could be fit to extract the magnitude of the 1H-31Pdipolar coupling constant. The dipolar coupling can then be used to calculate the distance betweenphosphorus and the close proximity protons. The results presented herein indicate primarily bi- andtridentate phosphonic acid bonding configuration at the SnO2 surface, in both CEPA and PPA cappednanoparticles.