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Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products

Katrien De Keukeleere, Sofie Coucke, Els De Canck UGent, Pascal Van Der Voort UGent, Fabien Delpech, Yannick Coppel, Zeger Hens UGent, Isabel Van Driessche UGent, Jonathan S. Owen and Jonathan De Roo UGent (2017) CHEMISTRY OF MATERIALS. 29(23). p.10233-10242
abstract
Although TiO2, ZrO2, and HfO2 nanocrystals are often synthesized in tri-n-octylphosphine oxide (TOPO), it is unclear whether TOPO also serves as ligand. Using liquid and solid state H-1 and P-31 nuclear magnetic resonance spectroscopy and X-ray fluorescence spectroscopy, we show that the nanocrystal surface is capped by several derivatives of TOPO. In the P-31 NMR spectrum, di-n-octylphosphinate (delta = 57 ppm) and P,P'-(di-n-octyl) pyrophosphonate (delta = 20 ppm) are found coordinated to the nanocrystal. In addition, hydrogen chloride associates with the metal oxide nanocrystal surface and protonates TOPO. The resulting hydroxyl-tri-n-octylphosphonium, [HO-PR3](+), is tightly associated with the nanocrystal surface (delta(P-31) = 73 ppm) due to electrostatic interactions and hydrogen bonding. To simplify the complex surface composition, we exchange the original surface species for carboxylate or phosphonate ligands. The protonation of TOPO is an unexpected example of lyophilic ion pairing between an acidic metal oxide nanocrystal and a weakly basic ligand molecule that is formed in nonpolar solution. Our results contrast with the classically envisaged L-type binding motif of TOPO to surface metal ions. The generality of this stabilization mode and its relevance to catalysis is discussed.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
journal title
CHEMISTRY OF MATERIALS
volume
29
issue
23
pages
10233 - 10242
Web of Science type
J
Web of Science id
000418206600044
ISSN
0897-4756
1520-5002
DOI
10.1021/acs.chemmater.7b04580
language
English
UGent publication?
yes
classification
U
copyright statement
I have transferred the copyright for this publication to the publisher
id
8543507
handle
http://hdl.handle.net/1854/LU-8543507
date created
2018-01-03 15:10:00
date last changed
2018-01-03 15:10:00
@article{8543507,
  abstract     = {Although TiO2, ZrO2, and HfO2 nanocrystals are often synthesized in tri-n-octylphosphine oxide (TOPO), it is unclear whether TOPO also serves as ligand. Using liquid and solid state H-1 and P-31 nuclear magnetic resonance spectroscopy and X-ray fluorescence spectroscopy, we show that the nanocrystal surface is capped by several derivatives of TOPO. In the P-31 NMR spectrum, di-n-octylphosphinate (delta = 57 ppm) and P,P'-(di-n-octyl) pyrophosphonate (delta = 20 ppm) are found coordinated to the nanocrystal. In addition, hydrogen chloride associates with the metal oxide nanocrystal surface and protonates TOPO. The resulting hydroxyl-tri-n-octylphosphonium, [HO-PR3](+), is tightly associated with the nanocrystal surface (delta(P-31) = 73 ppm) due to electrostatic interactions and hydrogen bonding. To simplify the complex surface composition, we exchange the original surface species for carboxylate or phosphonate ligands. The protonation of TOPO is an unexpected example of lyophilic ion pairing between an acidic metal oxide nanocrystal and a weakly basic ligand molecule that is formed in nonpolar solution. Our results contrast with the classically envisaged L-type binding motif of TOPO to surface metal ions. The generality of this stabilization mode and its relevance to catalysis is discussed.},
  author       = {De Keukeleere, Katrien and Coucke, Sofie and De Canck, Els and Van Der Voort, Pascal and Delpech, Fabien and Coppel, Yannick and Hens, Zeger and Van Driessche, Isabel and Owen, Jonathan S. and De Roo, Jonathan},
  issn         = {0897-4756},
  journal      = {CHEMISTRY OF MATERIALS},
  language     = {eng},
  number       = {23},
  pages        = {10233--10242},
  title        = {Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products},
  url          = {http://dx.doi.org/10.1021/acs.chemmater.7b04580},
  volume       = {29},
  year         = {2017},
}

Chicago
De Keukeleere, Katrien, Sofie Coucke, Els De Canck, Pascal Van Der Voort, Fabien Delpech, Yannick Coppel, Zeger Hens, Isabel Van Driessche, Jonathan S. Owen, and Jonathan De Roo. 2017. “Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products.” Chemistry of Materials 29 (23): 10233–10242.
APA
De Keukeleere, K., Coucke, S., De Canck, E., Van Der Voort, P., Delpech, F., Coppel, Y., Hens, Z., et al. (2017). Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products. CHEMISTRY OF MATERIALS, 29(23), 10233–10242.
Vancouver
1.
De Keukeleere K, Coucke S, De Canck E, Van Der Voort P, Delpech F, Coppel Y, et al. Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products. CHEMISTRY OF MATERIALS. 2017;29(23):10233–42.
MLA
De Keukeleere, Katrien, Sofie Coucke, Els De Canck, et al. “Stabilization of Colloidal Ti, Zr, and Hf Oxide Nanocrystals by Protonated Tri-n-octylphosphine Oxide (TOPO) and Its Decomposition Products.” CHEMISTRY OF MATERIALS 29.23 (2017): 10233–10242. Print.