All-trans-β-carotene absorption shift and electron-phonon coupling modulated by solvent polarizability

Song

et al. 2019

Sci Rep

Metal-enhanced fluorescence of carotenoids, all- trans -β-carotene and 8′-apo-β-carotene-8′-al dispersed in thin layers of polystyrene and polyethylene glycol were investigated by time-resolved fluorescence spectroscopy. The weak emission signals of carotenoids in polymer films were increased by 4–40 times in the presence of a silver island film and the emission lifetimes of both carotenoids were measured as significantly shortened. The energy transfer from the intermediate states of carotenoids to the silver islands and the subsequent surface plasmon coupled emission were proposed for the mechanisms of metal-enhanced fluorescence. The fluorescence enhancements of carotenoids in the polymer films were also investigated statistically over a wide area of the silver island films.

Section: Resultssupporting

confidence: 66%

Metal-enhanced fluorescence and excited state dynamics of carotenoids in thin polymer films

Song

et al. 2019

Sci Rep

“…The values of the HR factor of H-capped polyynes reported in Fig. 4a are larger than those of the radial breathing mode of carbon nanotubes 11 , 20 , and are comparable with the HR factors found for β-carotene 21 , 22 , 41 . Recently, Martinati et al calculated the HR factor of long sp-carbon chains ( 100 carbon atoms) confined in carbon nanotubes from wavelength-dependent resonance Raman measurements and found an average value of 1.82 as a possible upper limit for long chains towards carbyne 9 .…”

Section: Discussionsupporting

confidence: 81%

Electron-phonon coupling and vibrational properties of size-selected linear carbon chains by resonance Raman scattering

et al. 2022

UV resonance Raman spectroscopy of size-selected linear sp-carbon chains unveils vibrational overtones and combinations up to the fifth order. Thanks to the tunability of the synchrotron source, we excited each H-terminated polyyne (HCnH with n = 8,10,12) to the maxima of its vibronic absorption spectrum allowing us to precisely determine the electronic and vibrational structure of the ground and excited states for the main observed vibrational mode. Selected transitions are shown to enhance specific overtone orders in the Raman spectrum in a specific way that can be explained by a simple analytical model based on Albrecht’s theory of resonance Raman scattering. The determined Huang–Rhys factors indicate a strong and size-dependent electron-phonon coupling increasing with the sp-carbon chain length.

“…The longest wavelength absorption maximum of Beta Carotene has been shown to be shifted from ~476 nm in ethanol to ~515 nm in 1:1 ethanol water solution due to J aggregation [ 35 , 38 , 39 , 40 ]. Similar spectral shifting in a range of solvents has been documented, depending on polarisability [ 37 , 61 , 62 ], and the UV-Vis spectrum of Beta Carotene in solution is also pressure-dependent, the longest wavelength absorption maximum shifting as low as ~580 nm in carbon disulphide solution at 0.96 GPa [ 63 ]. In H aggregates of Zeaxanthin, prepared in Ethanol:Water mixtures, the UV-vis spectrum is dominated by a strong feature at 370 nm, while in 1:9 THF:Water solutions, the longest wavelength absorption maximum is shifted from 485 nm to ~510 nm [ 64 , 65 ].…”

Section: Discussionmentioning

confidence: 55%

Quantitative Raman Analysis of Carotenoid Protein Complexes in Aqueous Solution

et al. 2022

Carotenoids are naturally abundant, fat-soluble pigmented compounds with dietary, antioxidant and vision protection advantages. The dietary carotenoids, Beta Carotene, Lutein, and Zeaxanthin, complexed with in bovine serum albumin (BSA) in aqueous solution, were explored using Raman spectroscopy to differentiate and quantify their spectral signatures. UV visible absorption spectroscopy was employed to confirm the linearity of responses over the concentration range employed (0.05–1 mg/mL) and, of the 4 Raman source wavelengths (785 nm, 660 nm, 532 nm, 473 nm), 532 nm was chosen to provide the optimal response. After preprocessing to remove water and BSA contributions, and correct for self-absorption, a partial least squares model with R2 of 0.9995, resulted in an accuracy of the Root Mean Squared Error of Prediction for Beta Carotene of 0.0032 mg/mL and Limit of Detection 0.0106 mg/mL. Principal Components Analysis clearly differentiated solutions of the three carotenoids, based primarily on small shifts of the main peak at ~1520 cm−1. Least squares fitting analysis of the spectra of admixtures of the carotenoid:protein complexes showed reasonable correlation between norminal% and fitted%, yielding 100% contribution when fitted with individual carotenoid complexes and variable contributions with multiple ratios of admixtures. The results indicate the technique can potentially be used to quantify the carotenoid content of human serum and to identify their differential contributions for application in clinical analysis.