Electrochemical Spectroscopic Methods for the Fine Band Gap Electronic Structure Mapping in Organic Semiconductors

Functionality of organic photonic devices is markedly influenced by the electronic band structure of the used materials. An easy and quick determination of the density of states function (DOS) in the whole energy range from HOMO to LUMO, including the presence of defect states in the band gap, is a prerequisite to a successful design of photonic devices. In this study we present the fine band gap electronic structure mapping in P3HT with two electrochemical spectroscopic methods: the energy-resolved electrochemical impedance spectroscopy (ER-EIS) and the kinetic sensitive voltcoulometry (VCM). We showed that the P3HT exposition to air results in the change of light-induced polaron states in the band gap. The electrochemically measured data are compared with those from the literature, obtained with combined optical spectroscopic methods, electrical methods, or first-principles calculations. The ER-EIS method has been shown as capable of providing valuable information on the DOS in the whole energy range from HOMO to LUMO, and the VCM method opens the possibility to study separately the charge transfer (redox) processes with different kinetics. © 2015 American Chemical Society.Slovak Research and Development Agency [APVV-0096-11]; Scientific Grant Agency VEGA [2/0165/13, 1/0501/15

The Antifungal Properties of Super-Hydrophobic Nanoparticles and Essential Oils on Different Material Surfaces

This study was undertaken to determine the in vitro antifungal activities of super-hydrophobic nanoparticles (SHNPs), essential oils (EOs), and their mixtures (SHNPs/EOs). We have applied a thin layer of SHNPs in combination with various concentrations of three EOs: Arborvitae (Thuja plicata), Oregano (Origanum vulgare L.), and Thyme (Thymus vulgaris). The mixtures were spread on the surface of different materials: whitewood, sandstone, and paper. The antifungal and protective properties of these SHNP and EO mixtures were evaluated. The parameter Rr (ratio of reflectivity) was determined to identify the color changes of substrates. Digital microscopy was used to measure the colonization area of molds and also their penetration in the analyzed materials. Surprisingly, the use of SHNPs alone showed a balanced compromise in order to inhibit the mold growth on assayed surfaces

Thickness effect on structural defect-related density of states and crystallinity in P3HT thin films on ITO substrates

We report on a study of thickness effect on the formation of structural defect-related density of states (DOS) in the band gap of poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films spincoated on ITO substrates. The energy-resolved electrochemical impedance spectroscopy and grazing-incidence wide-angle X-ray scattering were used to correlate the DOS with the degree of crystallinity in P3HT thin films. We found an exponential increase of the defect DOS in the band gap with increasing fraction of the amorphous phase when decreasing the film thickness. The exponent increases abruptly when reducing the thickness down to 30 nm, which indicates two thickness regions with different dynamics of the defect DOS formation driven by increasing the fraction of the amorphous phase. Moreover, we observed the co-existence of two P3HT polymorphic crystalline phases with different backbone spacings, which results in the appearance of a peculiar DOS satellite peak above the highest occupied molecular orbital. The volume of the minor, more dense, crystalline phase exhibits a thickness dependence with a maximum plateau around 40 nm. These results suggest an important effect of the substrate roughness on the crystallinity and polymorphism of P3HT thin films depending on the film thickness with general implications for polymer thin films. © 2018 American Chemical Society.P3HT, SAS Institute; COFORD, Programme of Competitive Forestry Research for Development; APVV-0096-11, APVV, Agentúra na Podporu Výskumu a Vývoja; 2/0092/18; 1/0501/15; 2/0163/17; 26240220047; FEDER, European Regional Development FundSlovak Research and Development Agency [APVV-0096-11]; Scientific Grant Agency VEGA [1/0501/15, 2/0163/17, 2/0092/18]; Research and Development Operational Programme - ERDF [26240220047

Protection and Disinfection Activities of Oregano and Thyme Essential Oils Encapsulated in Poly(ε-caprolactone) Nanocapsules

The biocolonization of building materials by microorganisms is one of the main causes of their degradation. Fungi and bacteria products can have an undesirable impact on human health. The protection and disinfection of sandstone and wood materials are of great interest. In this study, we evaluated the protection and disinfection activity of oregano and thyme essential oils encapsulated in poly(ε-caprolactone) nanocapsules (Or-NCs, Th-NCs) against four types of environmental microorganisms: Pleurotus eryngii, Purpureocillium lilacinum (fungal strains), Pseudomonas vancouverensis, and Flavobacterium sp. (bacterial strains). The surfaces of sandstone and whitewood samples were inoculated with these microorganisms before or after applying Or-NCs and Th-NCs. The concentration-dependent effect of Or-NCs and Th-NCs on biofilm viability was determined by the MTT reduction assay. The results showed that Or-NCs and Th-NCs possess effective disinfection and anti-biofilm activity. Diffuse reflectivity measurements revealed no visible color changes of the materials after the application of the nanoencapsulated essential oils

Protection and Disinfection Activities of Oregano and Thyme Essential Oils Encapsulated in Poly(ε-caprolactone) Nanocapsules

The biocolonization of building materials by microorganisms is one of the main causes of their degradation. Fungi and bacteria products can have an undesirable impact on human health. The protection and disinfection of sandstone and wood materials are of great interest. In this study, we evaluated the protection and disinfection activity of oregano and thyme essential oils encapsulated in poly(ε-caprolactone) nanocapsules (Or-NCs, Th-NCs) against four types of environmental microorganisms: Pleurotus eryngii, Purpureocillium lilacinum (fungal strains), Pseudomonas vancouverensis, and Flavobacterium sp. (bacterial strains). The surfaces of sandstone and whitewood samples were inoculated with these microorganisms before or after applying Or-NCs and Th-NCs. The concentration-dependent effect of Or-NCs and Th-NCs on biofilm viability was determined by the MTT reduction assay. The results showed that Or-NCs and Th-NCs possess effective disinfection and anti-biofilm activity. Diffuse reflectivity measurements revealed no visible color changes of the materials after the application of the nanoencapsulated essential oils

Real-Time Monitoring of Growth and Orientational Alignment of Pentacene on Epitaxial Graphene for Organic Electronics

The interaction between a graphene layer and pentacene (PEN) molecules leads to the formation of a lying-down phase, which can improve charge transport for organic vertical field effect transistors and enhance the optical absorption for increased light harvesting in organic solar cells. Here, we present a comprehensive study of PEN growth on epitaxial graphene on silicon carbide (SiC). Simultaneous grazing-incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS) were used in situ for real-time monitoring of the PEN crystal growth with millisecond time resolution to identify two distinct anisotropic growth stages after the nucleation of the first monolayer (ML). In the first stage up to 1.5 nm, we observe rapid growth of pentacene domains along the (010) and (001) facets. This growth behavior is saturating after 1.5 nm. In a second stage, this is followed by continuous lateral crystal growth in only one in-plane direction (100) forming needle-shaped domains. In the second stage, an uninterrupted linear growth of the lying-down PEN phase is found based on the (001) diffraction up to 15 nm. Ex situ atomic force microscopy and polarized confocal Raman microscopy were used to further support the real-time observations of aligned PEN films on graphene