RESUMO
Electron and hole transport characteristics were evaluated for perylene-based and pyrene-based compounds using electron-only and hole-only devices. The perylene presented a columnar hexagonal liquid crystal phase at room temperature with strong molecular π-stacking inside the columns. The pyrene crystallizes bellow 166 °C, preserving the close-packed columnar rectangular structure of the mesophase. Photophysical analysis and numerical calculations assisted the interpretation of positive and negative charge carrier mobilities obtained from fitting the space charge limited regime of current vs voltage curves. The pyrene-based material demonstrated an electron mobility two orders of magnitude higher than the perylene one, indicating the potential of this class of materials as electron transporting layer.
RESUMO
Carbendazim (MBC) is a fungicide widely used in agriculture which allows the high productivity of several cultures, a necessary condition considering the growing of the world population. Moreover, MBC has environmental impact mainly on the soil and water sources, and consequently, on animal and human lives. However, even though the toxicity of fungicides is well established, their action mechanism in cell membranes are not completely understood. Herein, we investigate the interaction of different polar headgroups: dimethyldioctadecylammonium bromide (DODAB), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG); and different chain unsaturation degrees DPPC, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with MBC. Lipid monolayers at the air/water interface were applied as mimetic systems of cell membranes to investigate the interaction with MBC dissolved in the ultrapure water subphase. It was found that the interaction is driven preferably by electrostatic forces of the headgroups, with higher affinity for DODAB (cationic), intermediate for DPPC (zwitterionic), and absent for DPPG (anionic), considering the monolayer in the condensed phase. DODAB-MBC electrostatic interaction was consistent with FTIR (cast films). We also investigated giant unilamellar vesicles (GUVs) of zwitterionic lipids (DPPC, POPC, and DOPC) with distinct chain unsaturations in the presence of MBC by confocal microscopy and molecular dynamic (MD) simulations. The results indicate that, unlike the chain unsaturation, the polar headgroups play key role on the lipid-MBC interaction.
RESUMO
The control of molecular architectures has been exploited in layer-by-layer (LbL) films deposited on Au interdigitated electrodes, thus forming an electronic tongue (e-tongue) system that reached an unprecedented high sensitivity (down to 10(-12) M) in detecting catechol. Such high sensitivity was made possible upon using units containing the enzyme tyrosinase, which interacted specifically with catechol, and by processing impedance spectroscopy data with information visualization methods. These latter methods, including the parallel coordinates technique, were also useful for identifying the major contributors to the high distinguishing ability toward catechol. Among several film architectures tested, the most efficient had a tyrosinase layer deposited atop LbL films of alternating layers of dioctadecyldimethylammonium bromide (DODAB) and 1,2-dipalmitoyl-sn-3-glycero-fosfo-rac-(1-glycerol) (DPPG), viz., (DODAB/DPPG)5/DODAB/Tyr. The latter represents a more suitable medium for immobilizing tyrosinase when compared to conventional polyelectrolytes. Furthermore, the distinction was more effective at low frequencies where double-layer effects on the film/liquid sample dominate the electrical response. Because the optimization of film architectures based on information visualization is completely generic, the approach presented here may be extended to designing architectures for other types of applications in addition to sensing and biosensing.