In the present report, we present a combined experimental and theoretical study on the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) doping mechanism of regioregular poly(3-hexyl thiophene) (P3HT). First, we focus on the effects of LiTFSI doping in both crystalline and amorphous structures of P3HT by performing a complete structural analysis supported by classical molecular dynamics (MD) calculations. Then, we study the effects of LiTFSI doping on electronic properties such as charge transfer and charge transport by performing Raman and impedance spectroscopy, in both cases supported by density of functionals theory (DFT) calculations using periodic boundary conditions. Our structural analysis suggests that the LiTFSI dopant is mainly located in the amorphous region and only a small fraction is located in the crystalline region. In addition, our DFT calculations also suggest that the LiTFSI dopant can effectively act as an electronic acceptor only when it is located in the vicinity of and is accessible to the thiophene rings of P3HT due to the formation of a π•••Li chemical bond as an anchoring mechanism, permitting the electronic charge loss of thiophene rings through the sulfonyl groups. A thorough understanding of the LiTFSI doping mechanism of poly(alkyl thiophenes) (P3HT in this particular case) is crucial to elucidating not only the electronic but also the eventual mixed ionic−electronic transport mechanism and its promising properties, particularly as electrodes for lithium ion battery applications.

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Vitamin A and its esters are commonly found in topical applications because of their advantageous properties, however, have the drawback that are highly sensitive to ultraviolet radiation. The aim of this work was to develop and characterize a novel formulation of solid lipid nanoparticles suitable for topical applications in order to protect vitamin A from degradation. Vitamin A-loaded nanoparticles were successfully prepared by hot homogenization employing Gelucire 44/14 ® and cetyl alcohol as carrier materials, showing an entrapment efficiency of more than 90%. Particle size, measured by dynamic light scattering, was ca. 40 nm, while transmission electron microscopy images showed that dried nanoparticles were spherical with an average size of about 30-50 nm. Small angle X-ray scattering was used to study their aspect ratio and their physicochemical properties were evaluated by differential scanning calorimetry, infrared spectroscopy and X-ray powder diffraction, additionally, stability of vitamin A was studied by UV-Vis spectroscopy.

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In the present report, we focused on the study of the out-of-plane electrical transport of multiwalled carbon nanotube (MWCNT)-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) composites (PEDOT:PSS-MWCNTs) as electrodes for solar cell applications. The out-of-plane direct current and alternating current electrical transport, rarely studied but not less relevant, was additionally supported with in-plane and out-of-plane confocal Raman microscopy and grazing incidence small-angle X-ray scattering characterizations. The main relevance of our study is the monitoring of the polymer structure all across the polymeric film by using confocal Raman spectroscopy and its correlation with electrical transport. Modifications in the PEDOT benzenoid and quinoid conformations were observed in the vicinities of MWCNTs, and the enrichment of PSS at the indium tin oxide electrode interface was also evidenced. In consequence, the low MWCNT loadings into PEDOT:PSS lead to an increase of the out-of-plane conductivity, but the heavier MWCNT loadings lead to a drastic decrease. The tuning of the doping level of these polymer composites and the understanding of the interface structure are crucial to fabricate electrodes with higher out-of-plane conductivities for organic solar cell applications.

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