Amino acid analysis of lipases from oil pollutant isolates: Cunninghamella verticillata and Geotrichum candidum

Lipase is an enzyme commonly used in food, dairy, and other industries. Fungal lipases are more commonly used due to their secretion and easier production. Analyses of the amino acid composition of microbial lipases will hasten their potential usage in industrial applications. In this study, the major amino acid compositions of lipases secreted by oil pollutant isolates (Cunninghamella verticillata and Geotrichum candidum) enriched with fatty substances were analyzed by high performance liquid chromatography. Among eight major amino acids found in these lipases, histidine and ornithine were predominant. Lysine was absent from lipase generated by C. verticillata, while glutamine was absent from that produced by G. candidum. Conversely, glutamic acid, asparagine, histidine and arginine were present in slightly higher amounts in G. candidum. However, a slight decrease in aspartic acid and ornithine was observed in G. candidum. Analyses of the amino acids composition of lipase can potentially facilitate to predict the nature of this enzyme

Optical properties of quantum dots

The full potential-linearized augmented plane wave implemented in WIEN2K code to calculate the indirect energy gap (Γ–X) using density functional theory, thermal evaporation, and chemical bath deposition techniques are employed for analysis and characterization of different elements, compounds, and alloys semiconductors. Theoretically, modern implementations allow for a number of approximations to exchange and correlation and make no approximations to the shape of the crystal potential, unlike methods employing the atomic sphere approximation which assumes spherical symmetry around each atom. Additionally, Engel–Vosko generalized gradient approximation and modified Becke Johnson (mBJ) formalisms are used to optimize the corresponding potential for energetic transition and optical properties calculations as a function of quantum dot diameter to test the validity of our model of quantum dot potential. The refractive index and optical dielectric constant are investigated to explore best applications for solar cells. Experimentally, the structural and optical properties of X-ray diffractometer, ultra-violet (UV-vis), and transmission electron microscopy. The obtained results are in accordance with other experimental and theoretical data

Introduction to quantum dots

Quantum dots belong to a class of nanomaterials and are defined based on a fundamental length scale in materials, i.e., the exciton Bohr radius. Particles/clusters lower than the exciton Bohr radius are defined as quantum dots. In this chapter, the nanomaterials are defined based on the surface atoms and classification of nanomaterials based on morphologies are presented. The necessary theoretical framework is provided to define quantum dots based on the density of electronic energies. A protocol to determine the realistic materials structure is detailed. Properties of quantum dots such as size-dependent emission and size-dependent thermal properties are detailed. The surface effects of quantum dots on the charge transport through them is presented. Finally, the thermophysical properties of quantum dots are presented

Lubricated Conditions Imposed on Coating Multi-layer on Wear Resistance Under Cr2O3 Effect

Lubricated pin-on-disk sliding wear tests were performed on applied to Al-0.1Mg-0.35Ni-Si Alloy by using the spray coating method has been investigated. Different loads were 5, 10, and 15 N at a sliding velocity, 1.32 m/s at room temperature and 60% relative humidity. The surfaces were analyzed by using X-ray diffraction the residual (XRD), energy dispersive (EDS), scanning of (SEM) and (AFM), respectively. The results have showed that the thickness of Cr 2 O 3 coating was significantly related under the identical cold spray condition. These methods have contributed much of the understanding of quality and properties of surfaces. The (Cr 2 O 3 ) coating has great potential as a wear-resistant. The hardness increased from 102 ± 5 HV to 116.4 ± 2.5 HV at coating thickness 45 µm and friction coefficient reduced from 0.29 to 0.24; and the wear rate was about 2.11X10 -13 m 3 N -1 m -1 while hardness was increased from 102 ± 5 HV to 108 ± 3.5 HV at coating thickness 15 µm. The friction reduced from 0.31 to 0.29 at same coating thickness alloys, and the wear rate was about 2.73X10 -13 m 3 N -1 m -1 . The tribological properties of Cr 2 O 3 coating have exhibited low friction and beneficial to improve the adhesion which was clear on worn surfaces of Cr 2 O 3 coating. Crack, powder flocculation and powder formation are caused by the wear mode of the surface. Brittle fracture was found; while, adhesion and oxidation are the main mechanism of wear during the test

First-Principles Calculations to Investigate the Effect of Van der Waals Interactions on the Crystal and Electronic Structures of Tin-Based 0D Hybrid Perovskites

The electronic structures of four tin-based 0D hybrid perovskites ((NH3(CH2)2C6H5)2[SnCl6], (C6H10N2)[SnCl6], (C9H14N)2[SnCl6], and (C8H12N)2[SnCl6]) were determined by the DFT method employing the pseudopotential plane wave as implemented in the CASTEP code, and the first transition in each compound has been investigated based on the partial density states and dielectric function. According to the structural properties, incorporating organic cations with the appropriate structure, shape, and strong H-bonding functionality into hybrid perovskite crystals is very beneficial for preventing ion migration and thus enhances the efficiency of hybrid perovskite-based devices. Based on those properties employing the DFT+D method for the dispersion force, the effect of Van der Waals interaction on electronic structure was explained based on the nature of the first electronic transition. The similarity between the experimental and optimized structure was investigated by using a Bilbao crystallographic server. The study of optical properties shows that the Van der Waals interactions have a slight effect on the energy level of the curves. However, the profiles of curves are conserved. The absorption curves of the researched compounds are elaborated

Synthesis of carbon-based quantum dots from starch extracts: Optical investigations

Carbon-based quantum dots (C-QDs) were synthesized through microwave-assisted carbonization of an aqueous starch suspension mediated by sulphuric and phosphoric acids. The as-prepared C-QDs showed blue, green and yellow luminescence without the addition of any surface-passivating agent. The C-QDs were further analyzed by UV−vis spectroscopy to measure the optical response of the organic compound. The energy gaps revealed narrow sizing of C-QDs in the semiconductor range. The optical refractive index and dielectric constant were investigated. The C-QDs size distribution was characterized. The results suggested an easy route to the large scale production of C-QDs materials

Structural, elastic and lattice dynamical properties of the alkali metal tellurides: First-principles study

We report a detailed first-principles density functional calculations to understand the systematic trends for crystal structure, elastic and lattice dynamical properties of the anti-fluorite alkali metal tellurides M2Te depending from the type of the M cations (M are Li, Na, K and Rb). The calculated equilibrium lattice parameters are in very good agreement with the available experimental data. Single-crystal and polycrystalline elastic moduli and their related properties of the title compounds were calculated via the stress-strain method. The relatively weak values of the calculated elastic moduli demonstrate the weak resistance of these compounds to applied external forces. Phonon dispersion curves throughout the Brillouin zone and corresponding density of states were calculated using the linear response approach. No imaginary phonon modes were found, which indicate the dynamical stability of the examined materials. The atomic displacements at Γ point were determined. Low-frequency dielectric properties and infrared response were investigated

First-Principles Calculations to Investigate the Effect of Van der Waals Interactions on the Crystal and Electronic Structures of Tin-Based 0D Hybrid Perovskites

The electronic structures of four tin-based 0D hybrid perovskites ((NH3(CH2)2C6H5)2[SnCl6], (C6H10N2)[SnCl6], (C9H14N)2[SnCl6], and (C8H12N)2[SnCl6]) were determined by the DFT method employing the pseudopotential plane wave as implemented in the CASTEP code, and the first transition in each compound has been investigated based on the partial density states and dielectric function. According to the structural properties, incorporating organic cations with the appropriate structure, shape, and strong H-bonding functionality into hybrid perovskite crystals is very beneficial for preventing ion migration and thus enhances the efficiency of hybrid perovskite-based devices. Based on those properties employing the DFT+D method for the dispersion force, the effect of Van der Waals interaction on electronic structure was explained based on the nature of the first electronic transition. The similarity between the experimental and optimized structure was investigated by using a Bilbao crystallographic server. The study of optical properties shows that the Van der Waals interactions have a slight effect on the energy level of the curves. However, the profiles of curves are conserved. The absorption curves of the researched compounds are elaborated