Inhibition of Aspergillus VosA protein by lactic acid bacteria metabolites (in silico study)

In this work, we performed an in silico study using 3D structure protein of VosA, and analyzed the protein interaction via molecular docking using PyRx to test the inhibition efficacy of 15 metabolites compounds produced by lactic acid bacteria in conidia germination protein of Aspergillus. The antifungal docking findings revealed that these compounds showed good interactions and binding affinity against the target involved in conidia germination. The highest binding energy (-6.3 kcal/mol) was given by stearic acid. This interaction is due to the residue amines Ser and Phe. Palmitic acid also showed a good binding affinity with -6 kcal/mol. Lactic acid has not the same efficiency as palmitic, and stearic acid, which represented a value of -3.6 kcal/mol, the values recorded by cytidine was from -5 kcal/mol, which was also important compared to oxalic and acetic acid. DOI: http://dx.doi.org/10.5281/zenodo.560999

Exploring thermoelectric materials for renewable energy applications: The case of highly mismatched alloys based on AlBi1-xSbx and InBi1-xSbx

The high throughput thermoelectric devices are considered promising futuristic energy source to control global warming and realize the dream of green energy and sustainable environment. The ability of the highly mismatched alloys (HMAs), to show the intriguing impact on the physical properties with controlled modifications, has extended their promise to thermoelectric applications. Here, we examine comprehensively the potential of the two prototypical HMAs such as AlBi1-xSbx and InBi1-xSbx for thermoelectric applications within density functional theory together with the Boltzmann transport theory. For comprehensive understanding, alloying of these materials has been performed over the entire composition range. From our calculations, we found, the replacement of Sb with Bi leads to a significant evolution in the energy band-gap and effective masses of the charge carriers that consequently deliver enhancement in thermoelectric response. Improvement of magnitude 1.25 eV and 0.986 eV has been respectively recorded in band-gaps of AlBi1-xSbx and InBi1-xSbx for the across composition alloying. Similarly, by the electronic-structure engineering of HMAs, thermoelectric properties such as, the Seebeck coefficients over Fermi-level were found to be improved from 82.90 µV/K to 107.52 µV/K for AlBi1-xSbx and 60.32 µV/K to 92.73 µV/K for InBi1-xSbx. As a result, the thermoelectric figure of merit (ZT) and power factor show considerable enhancement as a function of alloying composition for both alloys at room temperature. However, at a higher temperature, the thermal conductivity of these materials experience an exponential increase, results in lower ZT values. Overall, the observed evolution in the electronic structure and thermoelectric response for replacing Sb over Bi is significant in AlBi1-xSbx as compared to InBi1-xSbx. Hence, with the capability of significant and controlled evolution in electronic-structure and subsequent thermoelectric properties, HMAs particularly AlBi1-xSbx are believed potential candidates for thermoelectric applications

A systematic study on Pt based, subnanometer-sized alloy cluster catalysts for alkane dehydrogenation: effects of intermetallic interaction

Platinum-based bimetallic nanoparticles are analyzed by the application of density functional theory to a series of tetrahedral Pt3X cluster models, with element X taken from the P-block, preferably group 14, or from the D-block around group 10. Almost identical cluster geometries allow a systematic investigation of electronic effects induced by different elements X. Choosing the propane-to-propene conversion as the desired dehydrogenation reaction, we provide estimates for the activity and selectivity of the various catalysts based on transition state theory. No significant Brønsted-Evans-Polanyi-relation could be found for the given reaction. A new descriptor, derived from an energy decomposition analysis, captures the effect of element X on the rate-determining step of the first hydrogen abstraction. Higher activities than obtained for pure Pt4 clusters are predicted for Pt alloys containing Ir, Sn, Ge and Si, with Pt3Ir showing particularly high selectivity

Selectivity control in Pt-catalyzed cinnamaldehyde hydrogenation

Chemoselectivity is a cornerstone of catalysis, permitting the targeted modification of specific functional groups within complex starting materials. Here we elucidate key structural and electronic factors controlling the liquid phase hydrogenation of cinnamaldehyde and related benzylic aldehydes over Pt nanoparticles. Mechanistic insight from kinetic mapping reveals cinnamaldehyde hydrogenation is structure-insensitive over metallic platinum, proceeding with a common Turnover Frequency independent of precursor, particle size or support architecture. In contrast, selectivity to the desired cinnamyl alcohol product is highly structure sensitive, with large nanoparticles and high hydrogen pressures favoring C=O over C=C hydrogenation, attributed to molecular surface crowding and suppression of sterically-demanding adsorption modes. In situ vibrational spectroscopies highlight the role of support polarity in enhancing C=O hydrogenation (through cinnamaldehyde reorientation), a general phenomenon extending to alkyl-substituted benzaldehydes. Tuning nanoparticle size and support polarity affords a flexible means to control the chemoselective hydrogenation of aromatic aldehydes

New plasmonic materials in visible spectrum through electrical charging

Due to their negative permittivity, plasmonic materials have found increasing number of applications in advanced photonic devices and metamaterials, ranging from visible wavelength through microwave spectrum. In terms of intrinsic loss and permittivity dispersion, however, limitations on available plasmonic materials remain a serious bottleneck preventing practical applications of a few novel nano-photonic device and metamaterial concepts in visible and nearinfrared spectra. To overcome this obstacle, efforts have been made and reported in literature to engineer new plasmonic materials exploring metal alloys, superconductors, graphene, and heavily doped oxide semiconductors. Though promising progress in heavily doped oxide semiconductors was shown in the near-infrared spectrum, there is still no clear path to engineer new plasmonic materials in the visible spectrum that can outperform existing choices noble metals, e.g. gold and silver, due to extremely high free electron density required for high frequency plasma response. This study demonstrates a path to engineer new plasmonic materials in the visible spectrum by significantly altering the electronic properties in existing noble metals through high density charging/discharging and its associated strong local bias effects. A density functional theory model revealed that the optical properties of thin gold films (up to 7 nm thick) can be altered significantly in the visible, in terms of both plasma frequency (up to 12%) and optical permittivity (more than 50%). These corresponding effects were observed in our experiments on surface plasmon resonance of a gold film electrically charged via a high density double layer capacitor induced by a chemically non-reacting electrolyte. © 2013 SPIE

First-principle investigation of thermoelectric and optoelectronic properties of Rb2KScI6 and Cs2KScI6 double perovskite for solar cell devices

Double perovskite (DP) halides are a reliable source of renewable energy that plays a vital role to fulfill the requirements of energy crunch. Therefore, the analysis of these perovskite halides have promising uses for thermoelectric and optoelectronics purposes. We investigated the thermoelectric and optoelectronics properties of Rb2KScI6 and Cs2KScI6 halides for use in renewable energy devices by using FP-LAPW + lo approach based on DFT. The calculated Goldsmith's tolerance factor and enthalpy of the formation of studied halides reveal that these are structurally and thermodynamically stable in cubic phase. Moreover, the analyzed value of Poisson and Pugh ratio reveals ductile nature of these materials. Further, we computed the bandgaps by analyzing electronic characteristics. For bandgap calculations of Rb2KScI6 (Eg = 2.75 eV) and Cs2KScI6 (Eg = 2.65 eV), we employed mBJ potentials to obtain precise values as comparison to experimental values. The complex dielectric function used to reveal the optical properties of the analyzed materials. The calculated optical results clearly show the maximum absorption of light in infrared (IR) region revealed that the analyzed materials are appropriate for optoelectronic purposes. The thermoelectric behavior was examined as to figure of merit (ZT), electrical-conductivity (EC), the Seebeck-coefficient (S) as well as thermal-conductivity. Animatedly in future, the analyzed consequences would be supportive to experimental investigation of Rb2KScI6 and Cs2KScI6 for renewable energy device applications

First-principles investigations of electronic structures and optical spectra of wurtzite and sphalerite types of ZnO1-xSx (x=0, 0.25, 0.50, 0.75 &1) alloys

Alloying of the zinc oxide (ZnO) with sulfur (S) chalcogen reveals vivid modifications of its electronic and optical properties driven by the dramatic restructuring of electronic structure. Here, we systematically executed mutual alloying of ZnO and ZnS in two different structural phases namely the wurtzite and sphalerite phases. Evolution in the physical properties of the designed ZnO1-xSx alloys for the compositions, x = 0, 0.25, 0.50, 0.75 and 1 has been comprehensively examined by using full-potential linearized augmented-plane-wave plus local orbital approach within density functional theory. It is observed that the replacement of the Oxygen by Sulfur atoms significantly affects the band-structure profiles of ZnO1-xSx alloys in both wurtzite and sphalerite geometries. Furthermore, by increasing the S contents in ZnO1-xSx alloys, the conduction band minimum is found to be moved in the upward direction resulting in enhancement of the bandgaps. The electronic bandgaps of ZnO1-xSx alloys were enhanced from 2.65 eV to 3.68 eV in wurtzite and from 2.50 eV to 3.60 eV in sphalerite phase. Similarly, the imaginary parts of the dielectric function of ZnO1-xSx move towards a high energy regime with an increase in S composition, which resulted in a blueshift in their absorption edges. Our results are found well-matching with available theoretical and experimental results. The variation in the energy bandgaps and optical properties makes the S-rich ZnO a promising candidate for ultraviolet photoelectronic devices

Exploring single-layered SnSe honeycomb polymorphs for optoelectronic and photovoltaic applications

Single-layered tin selenide that shares the same structure with phosphorene and possesses intriguing optoelectronic properties has received great interest as a two-dimensional material beyond graphene and phosphorene. Herein, we explore the optoelectronic response of the newly discovered stable honeycomb derivatives (such as α, β, γ, δ, and ɛ) of single-layered SnSe in the framework of density functional theory. The α, β, γ, and δ derivatives of a SnSe monolayer have been found to exhibit an indirect band gap, however, the dispersion of their band-gap edges demonstrates multiple direct band gaps at a relatively high energy. The ɛ-SnSe, however, features an intrinsic direct band gap at the high-symmetry Γ point. Their energy band gaps (0.53, 2.32, 1.52, 1.56, and 1.76 eV for α-, β-, γ-, δ-, and ɛ-SnSe, respectively), calculated at the level of the Tran-Blaha modified Becke-Johnson approach, mostly fall right in the visible range of the electromagnetic spectrum and are in good agreement with the available literature. The optical spectra of these two-dimensional (2D) SnSe polymorphs (besides β-SnSe) are highly anisotropic and possess strictly different optical band gaps along independent diagonal components. They show high absorption in the visible and UV ranges. Similarly, the reflectivity, refraction, and optical conductivities inherit strong anisotropy from the dielectric functions as well and are highly visible-UV polarized along the cartesian coordinates, showing them to be suitable for optical filters, polarizers, and shields against UV radiation. Our investigations suggest these single-layered SnSe allotropes as a promising 2D material for next-generation nanoscale optoelectronic and photovoltaic applications beyond graphene and phosphorene

First-principles investigations of structural parameters, electronic structures and optical spectra of 5–5- and BeO-type of ZnO1-xSx alloys

Due to the multifunctionality of the ZnO and its physical robustness, substantial research is focused on its alloying with different materials. Here, we investigate the optoelectronic properties of mutual alloying of 5–5 type and BeO type of ZnO with ZnS (such as ZnO1-xSx for x = 0, 0.25, 0.50, 0.75, and 1). By using density functional theory (DFT), calculations for the structural, electronic, and optical properties of 5–5 type and BeO type ZnO1-xSx are carried out. We have noticed that the incorporation of S atom in 5–5 type ZnO1-xSx has reduced its bandgap from 3.12 eV to 2.63 eV. On the other hand, a remarkable improvement from 2.85 eV to 3.75 eV in the bandgaps of BeO type ZnO1-xSx has been observed which makes the BeO type ZnO1-xSx more favorable for the future optoelectronic applications. Furthermore, the valence band maximum of 5–5 type ZnO1-xSx is strongly affected by the S composition, as a result, the nature of the bandgap has been transformed from direct to indirect bandgap at x = 0.50 composition. The imaginary part of the dielectric function, the onset of the absorption spectrum, and conductivity are found to experience a redshift. Whereas the static dielectric constants and static refractive indices are found to be increased with S content in both types of ZnO1-xSx alloys. Our results show that BeO type ZnO1-xSx alloys are relatively promising candidates for optoelectronic devices

Thermoelectric properties of the novel cubic structured silicon monochalcogenides: A first-principles study

The low-cost and non-toxic candidates of the Group-IV monochalcogenide family have attracted significant attention in recent years for large-scale thermoelectric applications. We conduct comprehensive investigations of the thermoelectric response of relatively inexpensive and less toxic cubic structured Si-monochalcogenides (π-SiS, π-SiSe, and π-SiTe) for renewable energy applications. The full-potential linearized-augmented-plus-local-orbital method within density functional theory has been adopted to calculate the ground state energies, whereas the semi-classical Boltzmann transport theory has been used for the calculations of thermoelectric properties. The Si-monochalcogenides in cubic phase demonstrate large values of thermopowers that amounts to 1740.0 μV/K, 1405.0 μV/K, and 771.92 μV/K of the π-SiS, π-SiSe, and π-SiTe respectively at 300 K. The thermopowers show an insignificant response to increase in temperature which is beneficial for the high-temperature thermoelectric applications of these materials. The optimal values of thermoelectric power factors of the cubic structured Si-chalcogenides occur at attainable doping levels and have been originated from the joint contribution of moderate electrical conductivities and thermopowers. These materials demonstrate the figure of merit values approaching unity and have shown a trivial response to the temperature gradient. Moreover, the occurrence of the optimal values of thermoelectric coefficients for electrons doped regime suggests the n-type doping as an easy option for enhancing the thermoelectric performance of these materials. Our investigations show that the Si-monochalcogenides in cubic phase feature interesting thermoelectric performance and can be used as a suitable replacement for the toxic and expensive binary chalcogenides for thermoelectric applications