Characterization of siloxane adsorbates covalently attached to TiO 2

Nobuhito Iguchi, Clyde Cady, Robert C. Snoeberger, Bryan M. Hunter, Eduardo M. Sproviero, Charles A. Schmuttenmaer, Robert H. Crabtree, Gary W Brudvig, Victor S. Batista

Research output: Chapter in Book/Report/Conference proceedingConference contribution

15 Citations (Scopus)

Abstract

Siloxanes with the general formula R-(CH2)n-Si-(OR') 3 form durable bonds with inorganic materials upon hydrolysis of labile -OR' groups, and serve as robust coupling agents between organic and inorganic materials. In the field of dye-sensitized solar cells, functionalization of TiO2 thin-films with siloxane adsorbates has been shown to be useful as a surface-passivation technique that hinders recombination processes and improves the overall efficiency of light-to-electricity conversion. However, the attachment of siloxane adsorbates on TiO2 surfaces still remains poorly understood at the molecular level. In this paper, we report the characterization of 3-(triethoxysilyl) propionitrile (TPS) adsorbates, covalently attached onto TiO2 surfaces. We combine synthetic methods based on chemical vapor deposition, Fourier transform (FT) infrared (IR) spectroscopy and electronic structure calculations based on density functional theory (DFT). We predict that trifunctional siloxanes form only 2 covalent bonds, in a 'bridge' mode with adjacent Ti4+ ions on the TiO2 surface, leaving 'dangling' alkoxy groups on the surface adsorbates. Our findings are supported by the observation of a prominent fingerprint band at 1000-1100 cm-1, assigned to Si-O-C stretching modes, and by calculations of binding enthalpies at the DFT B3LYP/(LACVP/6-31G**) level of theory indicating that the 'bridge' binding (ΔHb= -55 kcal mol-1) is more stable than 'tripod' motifs (ΔHb= -45 kcal mol-1) where siloxanes form 3 covalent bonds with the TiO2 surface. The alkoxysiloxane groups are robust under heat and water treatment and are expected to be particularly relevant for analytical methods since they could be exploited for immobilizing other functionalities onto the TiO2 surfaces.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
Volume7034
DOIs
Publication statusPublished - 2008
EventPhysical Chemistry of Interfaces and Nanomaterials VII - San Diego, CA, United States
Duration: Aug 11 2008Aug 12 2008

Other

OtherPhysical Chemistry of Interfaces and Nanomaterials VII
CountryUnited States
CitySan Diego, CA
Period8/11/088/12/08

Fingerprint

Siloxanes
siloxanes
Adsorbates
TiO2
Covalent bonds
inorganic materials
covalent bonds
Density Functional
Density functional theory
Tripod
density functional theory
tripods
Passivation
Functionalization
water treatment
Infrared Spectroscopy
Chemical Vapor Deposition
Coupling agents
Electronic Structure
Solar Cells

Keywords

  • Binding enthalpy
  • DFT
  • IR vibrational spectroscopy
  • Linkers
  • Silanes
  • Siloxanes
  • Solar cells
  • TiO

ASJC Scopus subject areas

  • Applied Mathematics
  • Computer Science Applications
  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Iguchi, N., Cady, C., Snoeberger, R. C., Hunter, B. M., Sproviero, E. M., Schmuttenmaer, C. A., ... Batista, V. S. (2008). Characterization of siloxane adsorbates covalently attached to TiO 2 . In Proceedings of SPIE - The International Society for Optical Engineering (Vol. 7034). [70340C] https://doi.org/10.1117/12.798938

Characterization of siloxane adsorbates covalently attached to TiO 2 . / Iguchi, Nobuhito; Cady, Clyde; Snoeberger, Robert C.; Hunter, Bryan M.; Sproviero, Eduardo M.; Schmuttenmaer, Charles A.; Crabtree, Robert H.; Brudvig, Gary W; Batista, Victor S.

Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7034 2008. 70340C.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Iguchi, N, Cady, C, Snoeberger, RC, Hunter, BM, Sproviero, EM, Schmuttenmaer, CA, Crabtree, RH, Brudvig, GW & Batista, VS 2008, Characterization of siloxane adsorbates covalently attached to TiO 2 . in Proceedings of SPIE - The International Society for Optical Engineering. vol. 7034, 70340C, Physical Chemistry of Interfaces and Nanomaterials VII, San Diego, CA, United States, 8/11/08. https://doi.org/10.1117/12.798938
Iguchi N, Cady C, Snoeberger RC, Hunter BM, Sproviero EM, Schmuttenmaer CA et al. Characterization of siloxane adsorbates covalently attached to TiO 2 . In Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7034. 2008. 70340C https://doi.org/10.1117/12.798938
Iguchi, Nobuhito ; Cady, Clyde ; Snoeberger, Robert C. ; Hunter, Bryan M. ; Sproviero, Eduardo M. ; Schmuttenmaer, Charles A. ; Crabtree, Robert H. ; Brudvig, Gary W ; Batista, Victor S. / Characterization of siloxane adsorbates covalently attached to TiO 2 . Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7034 2008.
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