Electric Field-induced Charge Transfer of (Bu4N)2[Ru(dcbpyH)2-(NCS)2] on Gold, Silver, and Copper Electrode Surfaces Investigated by Means of Surface-enhanced Raman Scattering

Joo, Sang‐Woo

doi:10.5012/bkcs.2007.28.8.1405

Cited by 16 publications

(3 citation statements)

References 28 publications

(31 reference statements)

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“…Figure a plots the intensity of the 1317 cm –1 band with 638 and 785 nm laser excitations as a function of potential. The potential difference is in agreement with the difference of laser excitation energy, which means that the photon-induced charge transfer (PICT) mechanism ,− is involved in the enhancement of the band. Illustrated schematically in Figure b is the charge-transfer process from the HOMO of N719 to the Fermi level of the TiO 2 shell under 638 and 785 nm excitation, compared with the interamolecular charge transfer under 532 nm excitation.…”

Section: Resultssupporting

confidence: 71%

Dimeric Core–Shell Ag₂@TiO₂ Nanoparticles for Off-Resonance Raman Study of the TiO₂–N719 Interface

et al. 2015

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In this paper, we present a nanoparticle-enhanced Raman spectroscopic study of TiO 2 -N719 (bis(tetrabutylammonium) [cis-di(thiocyanato)-bis (2, 2-bipyridyl-4-carboxylate-4-carboxylic acid)-ruthenium(II)])) interface by employing Ag 2 @TiO 2 dimeric core-shell nanoparticles, where the TiO 2 shell serves as an active semiconductor surface. The Ag 2 @TiO 2 nanoparticles are synthesized by connecting two Ag nanoparticles with thiol-modified complementary DNAs, followed by coating a 2 nm thin layer of TiO 2 on the Ag 2 dimeric nanoparticles. The Ag 2 @TiO 2 dimeric core-shell nanoparticles show red-shift of plasmon resonance frequency compared with Ag@TiO 2 core-shell nanoparticles, and provide significant SERS enhancement over the Ag@TiO 2 nanoparticles, which allows for the investigation of SERS of TiO 2 -N719 interface under off-resonance condition using low energy 785 nm laser excitation. Fine potential dependent Raman measurements show that thiocyano and carboxyl groups of the N719 molecule can adsorb on TiO 2 shell competitively: Along with negative potential excursion, the thiocyano is replaced by carboxyl, which is accompanied by conformation change of the molecule involving orientation change of the bipyridine ring. Furthermore, the potential of maximum intensity of the inter-ring vibration band shifts towards more positive value with laser excitation wavelength from 638 to 785 nm, which verifies the photon-driven charge transfer mechanism from the HOMO of N719 to the conduction bands of TiO 2 . Three-dimensional finite-difference time-domain (3D-FDTD) simulations are performed to evaluate the electromagnetic (EM) enhancement from the Ag 2 @TiO 2 dimeric core-shell nanoparticles. The present work demonstrates that the Ag 2 @TiO 2 dimeric core-shell structures provide significant plasmon resonance, which can be used for Raman investigations of interfaces formed with the semiconductor shell layers of the nanoparticles.

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Section: Resultssupporting

confidence: 71%

Dimeric Core–Shell Ag₂@TiO₂ Nanoparticles for Off-Resonance Raman Study of the TiO₂–N719 Interface

et al. 2015

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“…2067 cm –1 in free N3 powder. On the basis of such a large blue-shift (∼80 cm –1 ), it was concluded that Au@Ag is adsorbed on N3 via the S atom of SCN groups, similarly to the case of the Ag/N3 system, ,,, as illustrated in Figure . Compared to the spectrum of N3, a new band for ν s (COO – ) appears at ca.…”

Section: Resultsmentioning

confidence: 79%

Reduced Charge-Transfer Threshold in Dye-Sensitized Solar Cells with an Au@Ag/N3/n-TiO₂ Structure As Revealed by Surface-Enhanced Raman Scattering

Wang

Han

et al. 2018

J. Phys. Chem. C

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Interfacial information, such as the binding type and charge transfer (CT) processes, is critical for the investigation of dye-sensitized solar cells (DSSCs). Herein, Au@Ag core–shell nanoparticles (NPs) were employed for the fabrication of Au@Ag/N3/n-TiO2 systems. With the help of the CT degree (ρCT), surface-enhanced Raman scattering (SERS) spectra are utilized to evaluate the CT processes upon layer-by-layer addition of TiO2 to metal/N3/n-TiO2 systems based on Au@Ag, Ag, and Au. The layer-dependent SERS intensity and ρCT for Au@Ag/N3/n-TiO2 revealed a CT enhancement involving TiO2 at excitation wavelengths of 488, 514.5, 647, and 785 nm, whereas Ag/N3/n-TiO2 presented such enhancement only at excitation wavelengths of 488 and 514.5 nm. The mechanisms of CT process are proposed to explain such reduced CT energy threshold: In Au@Ag/N3/n-TiO2, an equivalent CT process involving TiO2 is first proposed, in which the electrons are directly transferred from the HOMO level of N3 to the much lower CB3 level of the Au@Ag/TiO2 complex due to energy level equilibration, which reduces the CT threshold involving TiO2 below1.58 eV, extends the CT response region involving TiO2 from 488 to 514.5 nm (Ag/N3/n-TiO2) to 488–785 nm and enhances the CT efficiency in the high-energy region. Finally, Au@Ag1–5 with different Ag/Au ratios were prepared for the fabrication of bimetal/N3/n-TiO2 systems. In the Au@Ag1/N3/n-TiO2 and Au@Ag2/N3/n-TiO2 systems, the decreased CT threshold is induced by energy level equilibration; in the Au@Ag4/N3/n-TiO2 system, it is due to the dual effects of energy level equilibration and activation of Ag at the core–shell surface induced by the inner Au.

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“…Pérez León et al completed the specific peak assignments of N719 adsorbed on Ag and Au nanoparticles (NPs) based on previous reports for Raman spectroscopy (RS), resonance Raman scattering (RRS), SERS, , and surface enhanced resonance Raman scattering (SERRS) . Joo presented that N719 had a relatively perpendicular geometry with its bipyridine ring on the metal surfaces and the carboxyl groups would likely be deprotonated. The occurrence of charge transfer between N719 and metal electrode surfaces had been examined by the variation of ν(SCN) in SERS spectra.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Charge Transfer in Ag/N719/TiO₂ Interface by Surface-Enhanced Raman Spectroscopy

Wang

Sui

et al. 2016

J. Phys. Chem. C

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The interfaces of metal−dye molecule−semiconductor sandwich structure are very important in the investigation of dyesensitized solar cells (DSSCs) where metals are used to enhance absorption. In this work, we first designed and synthesized Ag/N719 and Ag/N719/TiO 2 sandwich systems to investigate the chemical binding type at the interfaces of Ag/N719/TiO 2 . The results of the Raman spectra under the laser excitations of 532, 633, and 785 nm clarified that the SCN groups adsorbed on the Ag surface via the S terminal and the TiO 2 layer possibly bound to Ag/N719 via the ester linkage (OCO) of the COOH group in N719. Then, we optimized the Ag substrate as an SERS detection platform and selected the Ag sol film as the substrate. Last, the relationship between the "degree of CT (ρ CT )" in the SERS spectra and the charge transfer (CT) process was investigated by tuning the contribution from the chemical effect. We found that, owing to the introduction of TiO 2 , the intensity and ρ CT first increased (n = 0−2) and then decreased (n = 2−3) with the increase of the number of TiO 2 layers under 532 and 633 nm laser excitations. However, the intensity decreased (n = 0−3) with the increase of the number of TiO 2 layers under the laser excitation of 785 nm, and there was no obvious change about ρ CT . Meanwhile ρ CT became higher with the increase of the laser excitation energy at the interfaces with the same TiO 2 layer number. In order to explain these variations about ρ CT , we utilize ultraviolet photoelectron spectroscopy (UPS) and UV− vis spectra to calculate energy levels for better understanding the charge transfer (CT) process, and the calculation result is in accordance with the variation tendency of ρ CT .

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Electric Field-induced Charge Transfer of (Bu₄N)₂[Ru(dcbpyH)₂-(NCS)₂] on Gold, Silver, and Copper Electrode Surfaces Investigated by Means of Surface-enhanced Raman Scattering

Cited by 16 publications

References 28 publications

Dimeric Core–Shell Ag₂@TiO₂ Nanoparticles for Off-Resonance Raman Study of the TiO₂–N719 Interface

Dimeric Core–Shell Ag₂@TiO₂ Nanoparticles for Off-Resonance Raman Study of the TiO₂–N719 Interface

Reduced Charge-Transfer Threshold in Dye-Sensitized Solar Cells with an Au@Ag/N3/n-TiO₂ Structure As Revealed by Surface-Enhanced Raman Scattering

Investigation of Charge Transfer in Ag/N719/TiO₂ Interface by Surface-Enhanced Raman Spectroscopy

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Electric Field-induced Charge Transfer of (Bu4N)2[Ru(dcbpyH)2-(NCS)2] on Gold, Silver, and Copper Electrode Surfaces Investigated by Means of Surface-enhanced Raman Scattering

Cited by 16 publications

References 28 publications

Dimeric Core–Shell Ag2@TiO2 Nanoparticles for Off-Resonance Raman Study of the TiO2–N719 Interface

Dimeric Core–Shell Ag2@TiO2 Nanoparticles for Off-Resonance Raman Study of the TiO2–N719 Interface

Reduced Charge-Transfer Threshold in Dye-Sensitized Solar Cells with an Au@Ag/N3/n-TiO2 Structure As Revealed by Surface-Enhanced Raman Scattering

Investigation of Charge Transfer in Ag/N719/TiO2 Interface by Surface-Enhanced Raman Spectroscopy

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Electric Field-induced Charge Transfer of (Bu₄N)₂[Ru(dcbpyH)₂-(NCS)₂] on Gold, Silver, and Copper Electrode Surfaces Investigated by Means of Surface-enhanced Raman Scattering

Dimeric Core–Shell Ag₂@TiO₂ Nanoparticles for Off-Resonance Raman Study of the TiO₂–N719 Interface

Dimeric Core–Shell Ag₂@TiO₂ Nanoparticles for Off-Resonance Raman Study of the TiO₂–N719 Interface

Reduced Charge-Transfer Threshold in Dye-Sensitized Solar Cells with an Au@Ag/N3/n-TiO₂ Structure As Revealed by Surface-Enhanced Raman Scattering

Investigation of Charge Transfer in Ag/N719/TiO₂ Interface by Surface-Enhanced Raman Spectroscopy