In this work we use gap-fitting procedure to tune the long-range corrected functionals and accurately investigate the electronic and optical properties of the five main molecules composing Buriti oil (extracted from Mauritia flexuosa L.) in the framework of density functional theory (DFT) and time-dependent (TD) DFT. The characteristic length (1/ω) was observed to be entirely system dependent, though we concluded that its determination is of fundamental importance to rescue geometrical, electronic, and optical properties with accuracy. We demonstrate that our approach of tuning characteristic length for each system resulted in an absorbance spectra in better experimental agreement when compared to the traditional methodology. Therefore, this study indicates that the tuning of the range-separation parameter is crucial to improve the description of the optical properties of conjugated molecules when TDDFT is used. For example, the wavelength of maximum absorption, λmax, for the phytofluene, obtained using B3LYP, is 381 nm, while using the gap-fitting procedure for the tuned-LC-BLYP the estimated λmax changed to 358 nm. The latter estimate is in better agreement with the experimental value of 350 nm.

We present an extensive study of the optical properties of Myrcia sylvatica essential oil with the goal of investigating the suitability of its material system for uses in organic photovoltaics. The methods of extraction, experimental analysis, and theoretical modeling are described in detail. The precise composition of the oil in our samples is determined via gas chromatography, mass spectrometry, and X-ray scattering techniques. The measurements indicate that, indeed, the material system of Myrcia sylvatica essential oil may be successfully employed for the design of organic photovoltaic devices. The optical absorption of the molecules that compose the oil are calculated using time-dependent density functional theory and used to explain the measured UV-Vis spectra of the oil. We show that it is sufficient to consider the α-bisabolol/cadalene pair, two of the main constituents of the oil, to obtain the main features of the UV-Vis spectra. This finding is of importance for future works that aim to use Myrcia sylvatica essential oil as a photovoltaic material.

No abstract