Abstract
We predict the optical properties (in particular optical absorbance and reflectance anisotropy spectra (RAS)) of the silicon(001) surface organically functionalized by the adsorption of chosen tetr...
Highlights
Eumelanin is a photoprotective pigment widely present in living organisms: it is interesting both for its biological role and in view of possible applications, e.g., as a photoactive layer in hybrid solar cells
Studies of the electronic properties and optical absorption spectra of monomeric constituents of eumelanin (namely, DHI, DHICA (5,6-dihydroxyindole-2-carboxylic acid), IQ, and MQ) and of small chromophores in other biomolecules have been addressed by some of us using a systematic approach in the past years
In this work we investigate, by plane wave density functional theory (DFT), the absorption spectra and reflection anisotropy spectra (RAS) of the DHI-like tetramer-functionalized Si(001) surface, focusing on the effect of molecule adsorption in terms of sensitivity to the type of adsorbed molecule and to its adsorption configuration
Summary
Eumelanin is a photoprotective pigment widely present in living organisms: it is interesting both for its biological role and in view of possible applications, e.g., as a photoactive layer in hybrid solar cells. Studies of the electronic properties and optical absorption spectra of monomeric constituents of eumelanin (namely, DHI, DHICA (5,6-dihydroxyindole-2-carboxylic acid), IQ (indolequinone), and MQ (quinone-methide)) and of small chromophores in other biomolecules have been addressed by some of us using a systematic approach in the past years In many of those cases the role of the single small-scale constituent turned out to be of fundamental importance.[9−11] In the case of eumelanin, as mentioned above, the scenario is different,[6,8] and oligomerization needs to be taken into account in order to properly describe the experimental absorption spectrum of the pigment. The relative differences in total energy among the investigated systems are in all cases very small (below 0.1% of the total energy of the adsorbed system), with the 0° geometry being slightly energetically disfavored (favored, respectively) with respect to the other two orientations for PNZ (IMIM, respectively)
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