Dielectric and Thermal Effects on the Optical Properties of Natural Dyes: A Case Study on Solvated Cyanin

Malcıoğlu, Osman Barış
Gebauer, Ralph
Varsano, Daniele
Baroni, Stefano
The optical properties of the flavylium state of the cyanin dye are simulated numerically by combining Car-Parrinello molecular dynamics and linear-response time-dependent density functional theory calculations. The spectrum of the dye calculated in the gas phase is characterized by two peaks in the yellow and in the blue (green and violet), using a GGA-PBE (hybrid-B3LYP) DFT functional, which would bring about a greenish (bright orange) color incompatible with the dark purple hue observed in nature. Describing the effect of the water solvent through a polarizable continuum model does not modify qualitatively the resulting picture. An explicit simulation of both solvent and thermal effects using ab initio molecular dynamics results instead in a spectrum that is compatible with the observed coloration. This result is analyzed in terms of the spectroscopic effects of the molecular distortions induced by thermal fluctuations.


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Optical properties of Ga2SeS crystals grown by Bridgman method were investigated by transmission, reflection and ellipsometry measurements. Analysis of the transmission and reflection measurements performed in the wavelength range of 400-1100 nm at room temperature indicated the presence of indirect and direct transitions with 2.28 eV and 2.38 eV band gap energies. Ellipsometry measurements were carried out in the 1.2-6.0 eV spectral region to get information about optical constants, real and imaginary part...
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Spatio-temporal transformation of the femtosecond laser pulses at 1550 nm wavelength in c-Si is observed using the methods of time-resolved microscopy. The temporal dynamics of the pulse manifests itself both in widening of the frequency spectrum and in the change of on-axis time-width. It is shown, that along with Kerr effect, two-photon absorption also contributes to the temporal reshaping of the laser pulse. Despite the fact that absorption length for green light in c-Si is as small as 1 A mu m, generati...
Citation Formats
O. B. Malcıoğlu, R. Gebauer, D. Varsano, and S. Baroni, “Dielectric and Thermal Effects on the Optical Properties of Natural Dyes: A Case Study on Solvated Cyanin,” JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, pp. 15425–15433, 2011, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/42876.