Resonance Raman Spectra of Purified PS Ⅱ Core Antenna Complexes CP43 and CP47

PSⅡ core antenna complexes, CP43 and CP47, were purified from spinach (Spinacia oleracea L.) by DEAE Fractogel TSK 650S anion exchange chromatography. Their normal temperature (298 K) resonance Raman spectra were measured. The results suggest that all β carotenoids bound to CP43 and CP47 are in all trans configuration and likely in twisted conformations.

Resonance Raman Study of Aggregated Meso-tetra（4-pyridinium）porphyrin Diacid

Resonance Raman spectra of aggregated meso-tetra（4-pyridinium）porphyrin diacid （H8TPyP^6＋） were studied with excitation near the exciton absorption bands of 470 nm. The UV-Vis absorption and resonance light scattering spectra of HsTPyP^6＋ monomers and aggregates were also measured. The observed Raman bands of monomeric and aggregated HsTPyP^6＋ were assigned on the basis of the observed deuteration shifts and by comparing with the Raman spectra of analogous porphyrin diacids. Aggregation causes moderate downshifts （2-6 cm^-1） for high-frequency modes involving the in-plane CC/CN stretches of the porphyrin core and a dramatic upshift （12 cm^-1） for the out-of-plane saddling mode of the porphyrin ring. The structural changes induced by aggregation and the possible hydrogen bonding interaction between the HsTPyP^6＋ molecules in the aggregate are discussed based on the spectral observations.

Chemical Enhancement on Surface-Enhanced Resonance Raman Scattering of Au3-1,4-BenzenedithioI-Au3 Junction

Surface-enhanced Raman scattering （SERS） and surface-enhanced resonance Raman scattering （SERRS） spectra of the 1,4-benzenedithiol molecule in the junction of two Au3 clusters have been calculated using density functional theory （DFT） and time-dependent DFT method. In order to investigate the contribution of charge transfer （CT） enhancement, the wavelengths of incident light are chosen to be at resonance with four representative excited states, which correspond to CT in four different forms. Compared with SERS spectrum, SERRS spectra are enhanced enormously with distinct enhancement factors, which can be attributed to CT resonance in different forms.

Resonance Raman Spectroscopic and Theoretical Study of Geometry Distortion of Thiourea in 2^1A State

The A-band resonance Raman spectra of thiourea were obtained in water and acetonitrile solution. B3LYP/6-311＋＋G（3df,3pd） and RCIS/6-311＋＋G（3df,3pd） calculations were done to elucidate the ultraviolet electronic transitions, the distorted geometry structure and the saddle point of thiourea in 21A excited state, respectively. The resonance Raman spectra were assigned. The absorption spectrum and resonance Raman intensities were modeled using Heller＇s time-dependent wavepacket approach to resonance Raman scattering. The results indicate that largest change in the displacement takes place with the C--S stretch mode u6 （｜△｜=0.95） and noticeable changes appear in the H5N3H6＋H8N4H7 wag v5 （｜△｜=0.19）, NCN symmetric stretch^-C--S stretch＋N3H6＋H8N4 wag v4 （｜△｜=0.18）, while the moderate intensities of 2-15 and 4-15 are mostly due to the large excited state frequency changes of v15, but not due to its significant change in the normal mode displacement. The mechanism of the appearance of even overtones of the S-CN2 out of plane deformation is explored. The results indicate that a Franck-Condon region saddle point is the driving force for the quadric phonon mechanism within the standard A-term of resonance Raman scattering, which leads to the pyramidalization of the carbon center and the geometry distortion of thiourea molecule in 21A excited state.

Structural Dynamics of Phenyl Azide in Light-Absorbing Excited States： Resonance Raman and Quantum Mechanical Calculation Study

The excited state structural dynamics of phenyl absorbing S2（A＇）, S3（A＇）, and S6（A＇） states were troseopy and complete active space self-consistent and the UV absorption bands were assigned on azide （PhN3） after excitation to the light studied using the resonance Raman specfield calculations. The vibrational spectra the basis of the Fourier transform （FT）- Raman, FT-infrared measurements, the density-functional theory computations and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohex- ane, acetonitrile, and methanol solvents were, respectively, obtained at 273.9, 252.7, 245.9, 228.7, 223.1, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PhN3. The results indicated that the structural dynamics in the S2 （A＇）, S3（A＇）, and S6（A＇） states were significantly different. The crossing points of the potential energy surfaces, S2S1（1） and S2S1（2）, were predicted to play a key role in the low-lying excited state decay dynamics, in accordance with Kasha＇s rule, and NT=N8 dissociation. Two decay channels initiated from the Franck-Condon region of the S2（A＇） state were predicted： the radiative S2,min→S0 radiative decay and the S2→S1 internal conversion through the crossing points S2S1 （1）/S2S1（2）.

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Surface-enhanced resonance Raman scattering （SERRS） of Rhodamine 6G （R6G） adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even ＂breathing＂ of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

Combined spatial frequency spectroscopy analysis with visible resonance Raman for optical biopsy of human brain metastases of lung cancers

The purpose of this study is to examine optical spatial frequency spectroscopy analysis(SFSA)combined with visible resonance Raman(VRR)spectroscopic method,for thefirst time,to discriminate human brain metastases of lung cancers adenocarcinoma(ADC)and squamous cell carcinoma(SCC)from normal tissues.A total of 31 label-free micrographic images of three type of brain tissues were obtained using a confocal micro-Raman spectroscopic system.VRR spectra of the corresponding samples were synchronously collected using excitation wavelength of 532 nm from the same sites of the tissues.Using SFSA method,the difference in the randomness of spatial frequency structures in the micrograph images was analyzed using Gaussian functionfitting.The standard deviations,calculated from the spatial frequencies of the micrograph images were then analyzed using support vector machine(SVM)classifier.The key VRR biomolecularfingerprints of carotenoids,tryptophan,amide II,lipids and proteins(methylene/methyl groups)were also analyzed using SVM classifier.All three types of brain tissues were identified with high accuracy in the two approaches with high correlation.The results show that SFSA–VRR can potentially be a dual-modal method to provide new criteria for identifying the three types of human brain tissues,which are on-site,real-time and label-free and may improve the accuracy of brain biopsy.

Investigation of the Short-Time Photodissociation Dynamics of Furfural in S2 State by Resonance Raman and Quantum Chemistry Calculations

Raman(resonance Raman,FT-Raman),IR and UV-visible spectroscopy and quantum chemistry calculations were used to investigate the photodissociation dynamics of furfural in S2 state.The resonance Raman(RR)spectra indicate that the photorelaxation dynamics for the S0→S2 excited state is predominantly along nine motions:C=O stretchν5(1667 cm-1),ring C=C antisymmetric stretchν6(1570 cm-1),ring C=C symmetric stretchν7(1472 cm-1),C2-O6-C5 symmetric stretch/C1-H8 rock in planeν8(1389 cm-1),C3-C4 stretch/C1-H8 rock in planeν9(1370 cm-1),C5-O6 stretch in planeν12(1154 cm-1),ring breathν13(1077 cm-1),C3-C4 stretchν14(1020 cm-1),C3-C2-O6 symmetric stretchν16(928 cm-1).Stable structures of S0,S1,S2,T1 and T2 states with Cs point group were optimized at CASSCF method in Franck-Condon region there are S2/S1 conical intersection was found by state average method and RR spectra.

Robust and high-sensitivity thermal probing at the nanoscale based on resonance Raman ratio (R3)

Raman spectroscopy-based temperature sensing usually tracks the change of Raman wavenumber,linewidth and intensity,and has found very broad applications in characterizing the energy and charge transport in nanomaterials over the last decade.The temperature coefficients of these Raman properties are highly material-dependent,and are subjected to local optical scattering influence.As a result,Raman-based temperature sensing usually suffers quite large uncertainties and has low sensitivity.Here,a novel method based on dual resonance Raman phenomenon is developed to precisely measure the absolute temperature rise of nanomaterial(nm WS_(2) film in this work)from 170 to 470 K.A 532 nm laser(2.33 eV photon energy)is used to conduct the Raman experiment.Its photon energy is very close to the excitonic transition energy of WS_(2) at temperatures close to room temperature.A parameter,termed resonance Raman ratio(R3)Ω=I_(A1g)/IE_(2g) is introduced to combine the temperature effects on resonance Raman scattering for the A_(1g) and E_(2g) modes.Ω has a change of more than two orders of magnitude from 177 to 477 K,and such change is independent of film thickness and local optical scattering.It is shown that when Ω is varied by 1%,the temperature probing sensitivity is 0.42 K and 1.16 K at low and high temperatures,respectively.Based on Ω,the in-plane thermal conductivity(k)of a∼25 nm-thick suspended WS_(2) film is measured using our energy transport state-resolved Raman(ET-Raman).k is found decreasing from 50.0 to 20.0 Wm^(−1) K^(−1) when temperature increases from 170 to 470 K.This agrees with previous experimental and theoretical results and the measurement data using our FET-Raman.The R3 technique provides a very robust and high-sensitivity method for temperature probing of nanomaterials and will have broad applications in nanoscale thermal transport characterization,non-destructive evaluation,and manufacturing monitoring.

Selective conformer detection of short-lived base pair tautomers: A computational study of the unusual guanine-cytosine pairs using ultrafast resonance Raman spectroscopy

Base pair mismatch has been regarded as the main source of DNA point mutations, where minor shortlived tautomers were usually involved. However, the detection and characterization of these unnatural species pose challenges to existing techniques. Here, by using systematic structural and ultrafast resonance Raman(RR) spectral analysis for the four possible conformers of guanine-cytosine base pairs, the prominent marker Raman bands were identified. We found that the hydrogen bonding vibrational region from 2300 cm^(-1) to 3700 cm^(-1) is ideal for the identification of these short live species. The marker bands provide direct evidence for the existence of the tautomer species, thus offering an effective strategy to detect the short-lived minor species. Ultrafast resonance Raman spectroscopy would be a powerful tool to provide direct evidence of critical dynamical details of complex systems involving protonation or tautomerization.

Structural insights of catalytic intermediates in dialumene based CO_(2) capture: Evidences from theoretical resonance Raman spectra

CO_(2) capture is considered as one of the most ideal strategies for solving the environmental issues and against global warming.Recently,experimental evidence has suggested that aluminum double bond(dialumene) species can capture CO_(2) and further convert it into value-added products.However,the catalytic application of these species is still in its infancy.Both the dynamics mechanism of CO_(2) fixation and the detailed structures of catalytic intermediates are not well understood.In this work,we investigate the structure dependent resonance Raman(RR) signals for different reaction intermediates.Ab-initio simulations of spontaneous resonance Raman(spRR) and time-domain stimulated resonance Raman(stRR) give spectral signatures correlated to the existence of different intermediates during the CO_(2)-dialumene binding process.The unique Raman vibronic feature s contain rich structural information with high temporal resolution,enabling to monitor the transient catalytic intermediates under reaction conditions.Our work shows that RR can be used to monitor intermediates during the dialumene based CO_(2) capture reaction.The spectral features not only provide insight into the structural information of intermediate species,but also allow a deeper understanding of the dynamical details of this kind of catalytic process.

Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region

Aluminium nanohole arrays with fixed diameter were fabricated by focused ion beam and the periodicities were turned.Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region were studied experimentally and theoretically,which revealed that the SERRS enhancement factor was as high as 6 orders.

A pilot study for distinguishing basal cell carcinoma from normal human skin tissues using visible resonance Raman spectroscopy

Aim: The aim of the study is to test visible resonance Raman (VRR) spectroscopy for rapid skin cancer diagnosis,and evaluate its effectiveness as a new optical biopsy method to distinguish basal cell carcinoma (BCC) from normal skin tissues.Methods: The VRR spectroscopic technique was undertaken using 532 nm excitation. Normal and BCC human skin tissue samples were measured in seconds. The molecular fingerprints of various native biomolecules as biomarkers were analyzed. A principal component analysis - support vector machine (PCA-SVM) statistical analysis method based on the molecular fingerprints was developed for differentiating BCC from normal skin tissues.Results: VRR provides a rapid method and enhanced Raman signals from biomolecules with resonant and nearresonant absorption bands as compared with using a near-infrared excitation light source. The VRR technique revealed chemical composition changes of native biomarkers such as tryptophan, carotenoids, lipids and proteins.The VRR spectra from BCC samples showed a strong enhancement in proteins including collagen type I combined with amide I and amino acids, and a decrease in carotenoids and lipids. The PCA-SVM statistical analysis based on the molecular fingerprints of the biomarkers yielded a 93.0% diagnostic sensitivity, 100% specificity, and 94.5%accuracy compared with histopathology reports.Conclusion: VRR can enhance molecular vibrational modes of various native biomarkers to allow for very fast display of Raman modes in seconds. It may be used as a label-free molecular pathology method for diagnosis of skin cancer and other diseases and be used for combined treatment with Mohs surgery for BCC.

Experimental and Density Functional Theory Calculation Studies on Raman and Infrared Spectra of 1,1＇-Binaphthyl-2,2＇-diamine

The IR absorption, visible excited normal Raman, and UV-excited near-resonant Raman （UVRR） spectra of 1,1＇-binaphthyl-2,2＇-diamine （BINAM） were measured and analyzed. Density functional theory calculations were carried out to investigate its vibrational frequencies, infrared absorption, normal Raman, and near-resonance Raman intensities. The observed Raman and IR bands of BINAM were assigned with respect to the local vibrations of substituted 2-naphthylamine. Several Raman bands of BINAM were found selectively enhanced in the UVRR in comparison with the normal Raman spectrum. Possible excited state geometry distortion was discussed based on the resonance Raman intensity analysis.

Resonant Raman Scattering and Photoluminescence Emissions from Above Bandgap Levels in Dilute GaAsN Alloys

The transitions of E0 ,E0 ＋A0, and E＋ in dilute GaAs（1-x） Nx alloys with x = 0.10% ,0.22% ,0.36% ,and 0.62% are observed by micro-photoluminescence. Resonant Raman scattering results further confirm that they are from the intrinsic emissions in the studied dilute GaAsN alloys rather than some localized exciton emissions in the GaAsN alloys. The results show that the nitrogen-induced E E＋ and E0 ＋ A0 transitions in GaAsN alloys intersect at a nitrogen content of about 0.16%. It is demonstrated that a small amount of isoelectronic doping combined with micro-photoluminescence allows direct observation of above band gap transitions that are not usually accessible in photoluminescence.

The stimulated Raman scattering competition between solute and solvent in Rhodamine B solution

The competition between the stimulated resonance Raman scattering （SRRS） of Rhodamine B （RhB） and the stimulated Raman scattering （SRS） of ethanol （C2H50H） is observed at the RhB in C2H5OH solution. For different concentrations of the solution, the peak wavelengths of the SRRS, the amplified spontaneous emission （ASE）, the fluorescence and the absorption of RhB are different. The SRRS of RhB and the SRS of C2H50H are simultaneously generated when the concentration of the solution is 10-5 mol/L and the energy of the excitation laser is 20.4 mJ. Otherwise, only either the SRRS of RhB or the SRS of C2H5OH is generated. The SRRS can be amplified by the ASE gain when the SRRS is near the peak of the ASE, and the peak wavelength of the SRRS coincides with the wavelength of the maximal intensity ASE.

Raman Scattering at Resonant or Near-Resonant Conditions： A Generalized Short-Time Approximation

We investigate the dynamics of resonant Raman scattering in the course of the frequency de- tuning. The dephasing in the time domain makes the scattering fast when the photon energy is tuned from the absorption resonance. This makes frequency detuning to act as a camera shutter with a regulated scattering duration and provides a practical tool of controlling the scattering time in ordinary stationary measurements. The theory is applied to resonant Raman spectra of a couple of few-mode model systems and to trans-1,3,5-hexatriene and guanine-cytosine （G-C） Watson-Crick base pairs （DNA） molecules. Besides some particular physical effects, the regime of fast scattering leads to a simplification of the spectrum as well as to the scattering theory itself. Strong overtones appear in the Raman spectra when the photon frequency is tuned in the resonant region, while in the mode of fast scattering, the overtones are gradually quenched when the photon frequency is tuned more than one vibra- tional quantum below the first absorption resonance. The detuning from the resonant region thus leads to a strong purification of the Raman spectrum from the contamination by higher overtones and soft modes and purifies the spectrum also in terms of avoidance of dissociation and interfering fluorescence decay of the resonant state. This makes frequency detuning a very useful practical tool in the analysis of the resonant Raman spectra of complex systems and considerably improves the prospects for using the Raman effect for detection of foreign substances at ultra-low concentrations.

Influence of tip geometry on the spatial resolution of tip enhanced Raman mapping

In 2013,a breakthrough experiment pushed the Raman mapping of molecules via the tip-enhanced Raman scattering（TERS） technique to a sub-nanometer spatial resolution,going into the single-molecule level.This surprising result was well explained by accounting for the critical role of elastic molecule Rayleigh scattering within a plasmonic nanogap in enhancing both the localization and the intensity level of the Raman scattering signal.In this paper,we theoretically explore the influence of various geometric factors of the TERS system on the spatial resolution of Raman mapping,such as the tip curvature radius,tip conical angle,tip–substrate distance,and tip–molecule vertical distance.This investigation can help to find out the most critical geometric factor influencing the spatial resolution of TERS and march along in the right direction for further improving the performance of the TERS system.

Structural Dynamics of 3-Dimethylamino-2-methyl-propenal in S2（ππ^＊） State

The photophysics of 3-dimethylamino-2-methyl-propenal （DMAMP） after excitation to the S2 （ππ^＊） electronic state was studied using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The transition barriers of the ground state tautomerization reactions between DMAMP and its three isomers were determined at B3LYP/6-311＋＋G（d,p） level of theory. The vibrational spectra were assigned. The A- band resonance Raman spectra were obtained in acetonitrile with excitation wavelengths in resonance with the first intense absorption band to probe the structural dynamics of DMAMP. The B3LYP-TD computation was carried out to determine the relative A-band resonance Raman intensities of the fundamental modes, and the result indicated that the vibronic-coupling existed in Franck-Condon region. Complete active space self-consistent field （CASSCF） calculations were carried out to determine the excitation energies of the lower-lying singlet and triplet excited states, the conical intersection points and the intersystem crossing points. The A-band short-time structural dynamics and the corresponding decay dynamics of DMAMP were obtained by analysis of the resonance Raman intensity pattern and CASSCF computations. It was found that a sudden de-conjugation between C1=O6 and C2=C3 occurred at the Franck-Condon region of the S2（ππ^＊） state, while the enhancement of the conjugation interaction between C3 and N（CH3）2, and between C1 and C2 evolutions shortly after the wavepacket leaves away the Pranck-Condon region via the excited state charge redistribution. The de-conjugation interaction between C1=O6 and C2=C3 made the rotation of C3=N（CH3）2 group around the C2-C3 bond much easier, while the enhanced conjugation between C1 and C2, and between C3 and N（CH3）2 made the rotation around the C1-C2 bond and C3-N5 more difficult. It was revealed that the initial structural dynamics of DMAMP was predominantly towards the CI-I（S2/S0） point, while the opportunities towards either CI-2（S2/S0） or CI-3（S2/S0） point were negligible. Two decay channels of DMAMP from S2,FC（ππ^＊） to So or Tl,min via various CIs and ISCs were proposed.