NMR characterization of phosphonic acid capped SnO2 nanoparticles

Gregory P. Holland, Ramesh Sharma, Jacob O. Agola, Samrat Amin, Virgil C. Solomon, Poonam Singh, Daniel Buttry, Jeffery Yarger

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87 Scopus citations


Phosphonic acid capped SnO2 nanoparticles with diameters less than 5 nm were synthesized and characterized with multinuclear solution and solid-state magic angle spinning (MAS) NMR. Two types of phosphonic acid ligands were used to derivatize the SnO2 surface, producing (i) water soluble SnO2 nanoparticles capped with 2-carboxyethanephosphonic acid (CEPA) and (ii) insoluble SnO2 nanoparticles capped with phenylphosphonic acid (PPA). Multiple surface environments were observed with 31P solution and solid-state MAS NMR for both capping agents. The 31P resonances of derivatized SnO2 nanoparticles display 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 SnO2 surface. 1H MAS NMR spectra display a complete absence of the acidic protons of the phosphonic acid groups, 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 the build-up curves displayed oscillations that could be fit to extract the magnitude of the 1H-31P dipolar coupling constant. The dipolar coupling can then be used to calculate the distance between phosphorus and the close proximity protons. The results presented herein indicate primarily bi- and tridentate phosphonic acid bonding configuration at the SnO2 surface, in both CEPA and PPA capped nanoparticles.

Original languageEnglish (US)
Pages (from-to)2519-2526
Number of pages8
JournalChemistry of Materials
Issue number10
StatePublished - May 15 2007

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry


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