Summary of Article: melanin as a material for solar light absorbers

 

The infrared transmission spectra, Optical Density spectra, atomic force microscopy is used in study.

As per Lambert-Beer law

d is the melanin film thickness, ln(Ub/Us)  is measured from Optical Density.

The absorption coefficient decreases to ~ 10^4 cm−1 in the visible and near infrared region. So it is reasonable to consider these films as efficient light absorbers of near-ultraviolet radiation.

Melanin conductivity is due to extensive π-conjugation, at which electrons are delocalized across the entire oligomer stack(Oligomer stacks are a result of intermolecular π-π stacking, which is a process that involves the overlap of π-orbitals in the rings of a molecule)

An exponential growth in conductivity with increasing hydration level was observed for melanin film in experiment. 

Fourier Transform Infrared transmission spectrum of eumelanin film has found the presence of OH groups and CHn bonds with both sp3 and sp2 hybridizations. The ratio between the sp2 and sp3 hybridized CHn bonds may play a role in defining the film optical and electrical properties. Higher concentrations of sp2 hybridized bonds may lead to an increase in conductivity.

Source: https://arxiv.org/pdf/2412.07609#:~:text=The%20films%20demonstrate%20indirect%20allowed,in%20photovoltaic%20solar%20energy%20converters.