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 language | English |
|---|---|
| Title of host publication | Proceedings of SPIE - The International Society for Optical Engineering |
| Volume | 7034 |
| DOIs | |
| Publication status | Published - 2008 |
| Event | Physical Chemistry of Interfaces and Nanomaterials VII - San Diego, CA, United States Duration: Aug 11 2008 → Aug 12 2008 |
Other
| Other | Physical Chemistry of Interfaces and Nanomaterials VII |
|---|---|
| Country | United States |
| City | San Diego, CA |
| Period | 8/11/08 → 8/12/08 |
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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
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 proceeding › Conference contribution
}
TY - GEN
T1 - Characterization of siloxane adsorbates covalently attached to TiO 2
AU - Iguchi, Nobuhito
AU - Cady, Clyde
AU - Snoeberger, Robert C.
AU - Hunter, Bryan M.
AU - Sproviero, Eduardo M.
AU - Schmuttenmaer, Charles A.
AU - Crabtree, Robert H.
AU - Brudvig, Gary W
AU - Batista, Victor S.
PY - 2008
Y1 - 2008
N2 - 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.
AB - 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.
KW - Binding enthalpy
KW - DFT
KW - IR vibrational spectroscopy
KW - Linkers
KW - Silanes
KW - Siloxanes
KW - Solar cells
KW - TiO
UR - http://www.scopus.com/inward/record.url?scp=56249090404&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=56249090404&partnerID=8YFLogxK
U2 - 10.1117/12.798938
DO - 10.1117/12.798938
M3 - Conference contribution
SN - 9780819472540
VL - 7034
BT - Proceedings of SPIE - The International Society for Optical Engineering
ER -