Spintronics in halide perovskites has drawn significant attention in recent years, due to their highly tunable spin-orbit fields and intriguing interplay with lattice symmetry. Here, we perform ...first-principles calculations to determine the spin relaxation time (T
) and ensemble spin dephasing time (Formula: see text) in a prototype halide perovskite, CsPbBr
. To accurately capture spin dephasing in external magnetic fields we determine the Landé g-factor from first principles and take it into account in our calculations. These allow us to predict intrinsic spin lifetimes as an upper bound for experiments, identify the dominant spin relaxation pathways, and evaluate the dependence on temperature, external fields, carrier density, and impurities. We find that the Fröhlich interaction that dominates carrier relaxation contributes negligibly to spin relaxation, consistent with the spin-conserving nature of this interaction. Our theoretical approach may lead to new strategies to optimize spin and carrier transport properties.
An efficient semiempirical computational methodology is developed for the simulation of Tip-Enhanced Raman Spectroscopy (TERS), by combining the discrete-dipole approximation (DDA), the bond ...polarizability model (BPM), and density functional theory (DFT) to describe the vibrational properties of the material system. The method is illustrated for C60 whose TERS spectra are determined for different frequencies of incident illumination and for different tip shapes. The information on the local properties of the structure is correlated with the computed TERS signature, which is obtained by scanning the tip over the molecule. The method is versatile and is found to have a modest computational cost while allowing one to highlight the main features differentiating TERS from conventional Raman spectroscopy.
Kombucha has become a flavored tea drink fermented with a symbiotic community of fungi, yeast, and bacteria. Kombucha has been reported to show functional medicinal importance attributed to the ...presence of some critical metabolites and bioactive compounds. We developed kombucha on three different substrates like black tea, green tea, and Psidium guajava (guava) juice extract. Kombucha enriched with guava extract showed maximal growth in terms of weight (fresh and dry) and moisture percentage. Further, the total phenol, total flavonoid, and characterization of different phenolic compounds like gallic acid, catechin, guaiacol and coumaric acid with guava juice extract fermented kombucha exhibiting maximal production. Also, the high DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) radical scavenging activity over the control. The kombucha tea fermented on guava extract showed significant antimicrobial activity against eleven human pathogenic bacterial strains and four pathogenic fungi. From the current study, we conclude that the preparation of kombucha tea using guava juice extract might be used as a supplementary food product due to its high nutritional value.
In this thesis, first-principles calculations based on density functional theory (DFT) are used to study the electronic and vibrational properties of 2D, 1D, and 0D carbon nanostructures. Newly ...proposed carbon nanomaterials with tunable properties are potential candidates of sil- icon replacement in nanoelectronic applications. Part of studying new theoretical materials is assessing their dynamical stability, which is verified through performing phonon calculations on different investigated structures. Patterning 2D carbon allotropes into quasi-1D nanorib- bons is a broadly adopted strategy to open an electronic band gap, which is a desirable feature in areas such as field-effect transistors and switching devices. DFT calculations are performed on 1D tripentaphene nanoribbons to show that some of the investigated ribbons have semiconducting properties unlike their corresponding 2D tripentaphenes. Additionally, a DFT study on 2D naphthylene-β structure shows that the system exhibits semiconducting properties in its spin-polarized state due to its bipartition nature, where in a previous study, the system was confirmed to be metallic in its spin-paired state. Raman scattering is a reliable and non-destructive technique for the characterization of materials. As the graphene nanoribbons are transferred from their growth substrate to the device substrate, characterization of the ribbons is needed to identify their lengths and any defects as part of testing the functionality of the device. Raman spectra of 17-armchair graphene nanoribbons (17-AGNRs) are computed to study the effect of the length and width of the ribbons on the frequencies of the vibrational modes. The computed Raman spectra are then compared with experimental data, where the length and edge type of the ribbons measured in the experiment are identified. Finally, a computational method for the calculation of tip-enhanced Raman scatter- ing (TERS) is developed, where the target molecule is placed in the proximity of a noble- metal nanoparticle at a probing tip leading to the enhancement of the Raman signal. This method uses the discrete-dipole approximation (DDA) to compute the optical response of the nanoparticle, while the polarizabilty of the target molecule is calculated by using the bond polarizability model. TERS spectra are calculated for biphenyl and buckminster- fullerene molecules, and then compared with experimental data confirming the reliability of the method. It is shown that as the tip get sharper, and the incident field is in resonance with the nanoparticle, the TERS effect is more pronounced. Finally and more interestingly, 2D and 3D plots showing scans of the molecule are obtained, which provide visualization of the structure in real space as well as its constituents and chemical properties on the molecular level.
The aim of this study was to investigate the ligninolytic system of fungal strains isolated from Egyptian agricultural soil which are efficient in biodegradation and mineralization of lignin. They ...were identified morphologically, microscopically and confirmed by RAPD profiles. Based on PCR amplification and sequencing of the 18S rDNA gene an analytical phylogenetic tree was drawn for species confirmation. The screening experiment revealed that Emericella nidulans, Aspergillus fumigatus, Phoma betae, Penicillium oxalicum and Humicola grisea exhibited maximum potential for high lignin degradation. They showed higher lignin peroxidase and laccase activities. By process optimization, enhanced lignin degradation (94%) was achieved within 7 days in lignin-glucose medium when compared with lignin degradation (70%) obtained in glucose-free medium. The ligninolytic enzymatic activities had a great potential for decolorization of chemically different synthetic dyes (Azure B, Safranin, Crystal Violet and Malachite Green). The highest enzymatic activities and the highest decolorization rates were detected at a dye concentration of 0.2 g/L. The dye decolorization rate significantly increased with tryptophan addition as (1 mmol/L). Humicola grisea showed the highest decolorization rate (99%) with azure B. Phoma beta also showed a high decolorization rate (99% with crystal violet and 90% with safranin). The observed activity enhancement resulted from the protective effect of tryptophan against H
2
O
2
inactivation.
Impact of Banana Enzymes on Growth and Fruit Development Abdellatif, sawsan A.; Fadel, Mayada; Elkhawas, Ahmed
Future Perspectives of Medical, Pharmaceutical and Environmental Biotechnology,
07/2024, Letnik:
1, Številka:
2
Journal Article
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