Effect of TiO₂particles on normal and resonance Raman spectra of coumarin 343: a theoretical investigation

Abstract

It is well known that interfacial structures and charge transfer in dye-sensitized solar cells are extremely important for the enhancement of cell efficiency. Here, the normal Raman spectra (NRS) and resonance Raman spectra (RRS) of a C343-sensitized TiO2 cluster (Ti9O18) are theoretically predicted from combined electronic structure calculations and a vibrationally-resolved spectral method to reveal the relationship between interfacial geometries and excited-state dynamics. The results show that although the NRS of free C343 and the C343-TiO2 cluster correspond to the vibrational motions of C343 in a high frequency domain, their mode frequencies show obvious differences due to the interaction of the TiO2 cluster on C343, and several new Raman active fingerprint modes, such as bidentate chelating bonding modes, can be used to determine interfacial geometries. However, the resonance Raman activities of low-frequency modes are significantly enhanced and several modes from the TiO2 cluster can be observed, consistent with experimental measurements. Furthermore, the RRS from a locally excited state and a charge transfer state of C343-TiO2 are dramatically different, for instance, new Raman active modes with 1212 cm(-1), 1560 cm(-1) and 1602 cm(-1), corresponding to the motions of CH2 rocking, C=C/C-N/C=O stretching and C=O/C=C stretching, appear from the charge transfer state. The obtained information on mode-specific reorganization energies from these excited states is greatly helpful to understand and control interfacial electron transfer.

Preferred Molecular Orientation of Coumarin 343 on TiO2 Surfaces: Application to Dye-Sensitized Solar Cells

“… Similar coumarin derivatives have been shown to bind to the TiO 2 surface via a bidentate chelating carboxylate mode . For modeling purposes, this carboxylate···TiO 2 separation is assumed to be 2.05 Å; this model is consistent with previous spectroscopic results, even though alternative geometries have been speculated via computation . With diffraction data published by Honda et al, the maximum possible dye-layer thickness corresponds to the sum of this dye···TiO 2 separation and the fully extended length of the dye molecule (Figure ), that is, the longest dimension of the dye along its molecular mean plane ( d max = 11.42 Å).…”

“…though alternative geometries have been speculated via computation. 27 With diffraction data published by Honda et al 22 the maximum possible dye-layer thickness corresponds to the sum of this dye...TiO 2 separation and the fully extended length of the dye molecule (Figure 1) C343 features a molecular width of 6.04 Å (defined as the distance between atoms O1 and C5 perpendicular to the molecular length (Figure 1), from diffraction data. 22 This indicates a theoretical APM of 33.12 Å 2 , (Figure 4(a)), which is 16.18 Å 2 smaller than the area per molecule derived from the measurements using Equation (2).…”

Attomolar Sensing Based on Liquid Interface-Assisted Surface-Enhanced Raman Scattering in Microfluidic Chip by Femtosecond Laser Processing

“…57 As indicated in Figure 3c, the SERS chip may be used to detect coumarin, a prohibited food additive. 58,59 The detection limit for coumarin was 10 −7 M, which clearly is much lower than that for ordinary Raman measurement (Supporting Information, Figure S4a). LI-SERS Investigation in a Microfluidic Chip.…”

“…The chip lifetime is almost comparable to that reported for commercially available chips . As indicated in Figure c, the SERS chip may be used to detect coumarin, a prohibited food additive. , The detection limit for coumarin was 10 –7 M, which clearly is much lower than that for ordinary Raman measurement (Supporting Information, Figure S4a).…”

Atmospheric-pressure plasma treatments applied on titanium dioxide layer for Sb2S3 solar cells applications

“…At the region of 0-1000 cm -1 , shows the vibrational modes between 100-900 cm -1 , related to characteristic peaks of Anatase phase TiO2 according to previous works (Ekoi et al 2019). Also, it is possible to see a peak around 1374 cm -1 corresponding to the C-H2 bending observed in pure PVP (Zidan et al 2019), while the band at 1800-1900 cm -1 is related to carbonyl compounds, caused by the stretching of the C=O bond (L. Yang, Wu, and Zhao 2015) (Colthup, Daly, and Wiberley 1990).…”