scholarly journals Resonance Raman Spectro-Electrochemistry to Illuminate Photo-Induced Molecular Reaction Pathways

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 245 ◽  
Author(s):  
Linda Zedler ◽  
Sven Krieck ◽  
Stephan Kupfer ◽  
Benjamin Dietzek
Keyword(s):  
Structural Changes ◽  
Raman Band ◽  
Resonance Raman Spectroscopy ◽  
Spectroscopic Method ◽  
Resonance Raman ◽  
Reaction Pathways ◽  
Excitation Wavelength ◽  
Absorption Bands ◽  
The Individual ◽  
Sequential Reduction

Electron transfer reactions play a key role for artificial solar energy conversion, however, the underlying reaction mechanisms and the interplay with the molecular structure are still poorly understood due to the complexity of the reaction pathways and ultrafast timescales. In order to investigate such light-induced reaction pathways, a new spectroscopic tool has been applied, which combines UV-vis and resonance Raman spectroscopy at multiple excitation wavelengths with electrochemistry in a thin-layer electrochemical cell to study [RuII(tbtpy)2]2+ (tbtpy = tri-tert-butyl-2,2′:6′,2′′-terpyridine) as a model compound for the photo-activated electron donor in structurally related molecular and supramolecular assemblies. The new spectroscopic method substantiates previous suggestions regarding the reduction mechanism of this complex by localizing photo-electrons and identifying structural changes of metastable intermediates along the reaction cascade. This has been realized by monitoring selective enhancement of Raman-active vibrations associated with structural changes upon electronic absorption when tuning the excitation wavelength into new UV-vis absorption bands of intermediate structures. Additional interpretation of shifts in Raman band positions upon reduction with the help of quantum chemical calculations provides a consistent picture of the sequential reduction of the individual terpyridine ligands, i.e., the first reduction results in the monocation [(tbtpy)Ru(tbtpy•)]+, while the second reduction generates [(tbtpy•)Ru(tbtpy•)]0 of triplet multiplicity. Therefore, the combination of this versatile spectro-electrochemical tool allows us to deepen the fundamental understanding of light-induced charge transfer processes in more relevant and complex systems.

Application of UV-Vis and resonance Raman spectroscopy to study bleaching and photoyellowing of thermomechanical pulps

Holzforschung ◽  
2006 ◽  
Vol 60 (3) ◽  
pp. 231-238 ◽  
Author(s):  
Anna-Stiina Jääskeläinen ◽  
Anna-Maija Saariaho ◽  
Jouko Vyörykkä ◽  
Tapani Vuorinen ◽  
Pavel Matousek ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Light Exposure ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Excitation Wavelength ◽  
Thermomechanical Pulp ◽  
Pulp Bleaching ◽  
Absorption Bands ◽  
Peroxide Bleaching ◽  
Brightness Reversion

Abstract The chemistry of thermomechanical pulp bleaching and brightness reversion was studied. First, UV-Vis reflectance spectroscopy was used to obtain information on the reactive structures in pulp. Based on these data, a Raman excitation wavelength was chosen close to the absorption bands of the chromophores formed to take advantage of the resonance enhancement (resonance Raman spectroscopy). Fluorescence was rejected with a picosecond Kerr gate. The results revealed that coniferyl aldehyde structures were partly removed by alkaline peroxide bleaching and these structures were further degraded during light exposure. However, this reaction was obviously not responsible for chromophore formation in the pulp. On the other hand, based on the resonance Raman spectra, formation of quinonoid structures, possibly para-quinones, was a more prominent explanation for the brightness reversion.

scholarly journals Time-resolved surface-enhanced resonance Raman spectro-electrochemistry of heme proteins

2010 ◽  
Vol 24 (1-2) ◽  
pp. 125-129 ◽  
Author(s):  
Marc Grosserueschkamp ◽  
Christoph Nowak ◽  
Wolfgang Knoll ◽  
Renate L. C. Naumann
Keyword(s):  
Heme Proteins ◽  
High Performance ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Excitation Wavelength ◽  
Silver Surface ◽  
Rotating Disc ◽  
Measuring Cell ◽  
Surface Enhanced ◽  
Silver Substrate

Heme proteins such as cytochrome c (cc) play a fundamental role in many biological processes. Surface-enhanced resonance Raman spectroscopy (SERRS) combined with electrochemical methods is an ideal tool to study the redox processes of heme proteins. In this context we designed a new measuring cell allowing for simultaneous electrochemical manipulation and high sensitive SERRS measurements of heme proteins. The measuring cell is based on an inverted rotating disc electrode for excitation by using a confocal Raman microscope. Furthermore, we developed a SER(R)S-active silver modified silver substrate for spectro-electrochemical applications. For this purpose silver nanoparticles (AgNPs) were adsorbed on top of a planar silver surface. The substrate was optimized for an excitation wavelength of 413 nm corresponding to the resonance frequency of heme structures. An enhancement factor of 105was achieved. The high performance of the new measuring cell in combination with the new silver substrate was demonstrated using cc as a reference system.

Resonance Raman labels: spectroscopic studies on cis- and trans-4-benzylidene-2-phenyl-Δ2 -oxazolin-5-one and an isotopically substituted analog

1978 ◽  
Vol 56 (2) ◽  
pp. 232-239 ◽  
Author(s):  
K. Kumar ◽  
D. J. Phelps ◽  
P. R. Carey
Keyword(s):  
Raman Spectra ◽  
Electronic Transition ◽  
Raman Band ◽  
Resonance Raman ◽  
Spectroscopic Studies ◽  
Trans Isomers ◽  
Absorption Bands ◽  
Cis And Trans Isomers ◽  
Raman Excitation Profiles ◽  
Cis And Trans

The absorption and preresonance Raman spectra of cis- and trans-4-benzylidene-2-phenyl-Δ2-oxazoIin-5-one are reported. Although steric considerations suggest that the π electron pathway in the cis isomer is considerably distorted compared to the trans isomer, the Raman and absorption spectra of the two isomers are strikingly similar. Preresonance Raman excitation profiles for the cis and trans isomers indicate that the main features in the Raman spectra owe their intensity to coupling to the 360 nm absorption band present in both isomers. It is proposed that both the electronic dipole transition responsible for this absorption and the vibrational modes giving rise to the intense Raman bands are localized in the —C=C—N=C—Ph part of the molecule. Thus the main Raman and absorption bands are insensitive to isomerization in the benzylidene portion. Support for a localized electronic transition, polarized along the —C=C—N=C—Ph long axis, comes from Raman depolarization ratio (ρ) measurements which show that ail intense Raman features in both cis and trans isomers have ρ ∼ 0.33. Further support comes from ir and resonance Raman spectra of trans-4-(4-dimethylamino-3-nitrobenzylidene)-2-phenyloxazolin-5-one substituted either with 13C in the 4 position, or with 15N, in the oxazolinone ring. These spectra indicate that the main Raman feature seen in all 4-benzylidene-2-phenyloxazolinonesat 1561 cm−1 is a symmetric stretching mode associated with the —C=C—N=C— chain and that this feature has some C=N stretching character. The substitution experiments also show that the weak 1654 cm−1 Raman band has a high degree of C=C stretching character and may represent an essentially antisymmetric mode from the C=C—N=C moiety. The preresonance Raman excitation profiles show that the intensity enhancement follows an FB2 type dependence. The utility of the Raman spectrum as a probe for the chromophore responsible for the electronic transition in a highly conjugated system is discussed.

scholarly journals Monitoring membrane protein structural changes and interactions via deep UV resonance Raman spectroscopy

2015 ◽  
Author(s):  
◽  
Mia C. Brown
Keyword(s):  
Membrane Proteins ◽  
Structural Changes ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
The Body ◽  
Intramembrane Proteolysis ◽  
Parkinson’S Diseases ◽  
Uv Resonance Raman ◽  
Uv Resonance Raman Spectroscopy ◽  
Deep Uv

Membrane proteins perform a variety of functions within our cells. They transport nutrients and waste across the lipid barrier, transmit signals from one part of the body to another, and run our immune system. However, despite their ubiquitous and vital presence in all organisms, relatively little is known about this class of proteins compared to their soluble counterparts. Intramembrane proteolysis is a process involving membrane proteins that occurs in all biological organisms and has garnered particular interest due to its involvement in various disease pathologies, such as Alzheimer's and Parkinson's Diseases. In this work I have set out to use deep UV resonance Raman (DUVRR) spectroscopy to characterize structural and environmental transitions of proteins and applied the results to studies involving intramembrane proteolysis in an effort to better understand the key concepts behind it.

Self-Absorption in Resonance Raman and Rayleigh Scattering: A Numerical Solution

1988 ◽  
Vol 42 (8) ◽  
pp. 1458-1466 ◽  
Author(s):  
Michael Ludwig ◽  
Sanford A. Asher
Keyword(s):  
Rayleigh Scattering ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Excitation Wavelength ◽  
Signal Attenuation ◽  
Scattering Geometry ◽  
Capillary Sample ◽  
Spectral Signal ◽  
Spectral Detection ◽  
First Time

We have numerically calculated the parameters necessary to correct Raman intensities for self-absorption for Raman measurements utilizing a 90° scattering geometry and a cylindrical capillary sample cell. We display curves that can be used to extract these parameters for any sample absorbances at the incident laser excitation wavelength and the Raman scattered wavelength. These results make it possible, for the first time, to quantitatively utilize resonance Raman spectroscopy to determine concentrations of analytes. These parameters can also be used to numerically correct resonance Raman excitation profile measurements for self-absorption. These results clearly illustrate the dependence of spectral signal-to-noise ratios and spectral detection limits upon signal attenuation due to self-absorption.

scholarly journals Rapid Raman Spectroscopic Analysis of Stress Induced Degradation of the Pharmaceutical Drug Tetracycline

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1866 ◽  
Author(s):  
Christian Domes ◽  
Timea Frosch ◽  
Juergen Popp ◽  
Torsten Frosch
Keyword(s):  
Raman Spectroscopy ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Pharmaceutical Products ◽  
Small Sample ◽  
Small Concentration ◽  
Stress Factors ◽  
Excitation Wavelength ◽  
Raman Spectroscopic ◽  
Concentration Changes

Stress factors caused by inadequate storage can induce the unwanted degradation of active compounds in pharmaceutical formulations. Resonance Raman spectroscopy is presented as an analytical tool for rapid monitoring of small concentration changes of tetracycline and the metabolite 4˗epianhydrotetracycline. These degradation processes were experimentally induced by changes in temperature, humidity, and irradiation with visible light over a time period of up to 23 days. The excitation wavelength λexc = 413 nm was proven to provide short acquisition times for the simultaneous Raman spectroscopic detection of the degradation of tetracycline and production of its impurity in small sample volumes. Small concentration changes could be detected (down to 1.4% for tetracycline and 0.3% for 4-epianhydrotetracycline), which shows the potential of resonance Raman spectroscopy for analyzing the decomposition of pharmaceutical products.

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