| 1. |
- Ahmed, Shahbaz, et al.
(author)
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Accurate First-Principles Evaluation of Structural, Electronic, Optical and Photocatalytic Properties of BaHfO3 and SrHfO3 Perovskites
- 2022
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In: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 892
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Journal article (peer-reviewed)abstract
- A reliable first-principles account of experimentally observed physical properties of perovskite oxides is crucial for realizing their employment in electronic and optical devices. In this context, SCAN meta-GGA functional of DFT offers good approximation for the exchange-correlation energy; facilitating accurate determination of structural and energetic properties. However, SCAN is unable to reproduce electronic and optical properties of wide bad gap materials. In the present study, we report systematic DFT calculations to show that structural, energetic, electronic and optical properties of hafnium based BaHfO3 and SrHfO3 perovskite oxides can be accurately determined through a combine application of SCAN and Tran-Blaha modified Becke-Johnson (TB-mBJ) meta-GGAs. The structural and energetic properties computed using SCAN functional for both BaHfO3 and SrHfO3 are found to be in good agreement with experimental data; achieving a level of accuracy comparable to computationally expansive hybrid DFT calculations. On the other hand, TB-mBJ calculated band gaps computed using the SCAN optimized lattice parameters provide better agreement with experimental data at a low computational cost. The optical properties, band edge potentials and effective masses of the charge carriers in BaHfO3 and SrHfO3 are also computed to examine the combined application of SCAN and TB-mBJ meta-GGAs in predicting the photocatalytic performance of these wide band gap materials. Our results clearly show that the combination of the two meta-GGAs provide a computationally economical route for evaluating the photocatalytic performance of alkaline-earth metal hafnates.
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| 2. |
- Saeed, Aamer, et al.
(author)
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Identification of novel C-2 symmetric Bis-Azo-Azamethine molecules as competitive inhibitors of mushroom tyrosinase and free radical scavengers : synthesis, kinetics, and molecular docking studies
- 2022
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In: Journal of Biomolecular Structure and Dynamics. - : Taylor & Francis. - 0739-1102 .- 1538-0254. ; 40:10, s. 4419-4428
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Journal article (peer-reviewed)abstract
- Tyrosinase is a multi-copper enzyme found in plants, animals and microorganisms, plays a critical role in the melanogenesis and browning process critical to cosmetics and food industries. Many natural, semi-synthetic and synthetic inhibitors have been discovered. To this end, a small library of symmetrical Bis-Azo-Azamethine hybrids 5a–j was synthesized and characterized through spectroscopic and analytical data and explored for mushroom tyrosinase and free radical scavenging activity. All of the molecules 5a–j explicated better potential compared to the standard Kojic acid. On the whole, compound 5i having IC50 value 0.002 ± 0.004 µM was found to be the most potent derivative. The Kinetic studies were performed for 5i and indicating the mode of inhibition in a competitive manner. Structure Activity Relationship (SAR) analysis and docking studies were carried out. Thus compound 5i bearing bulky naphthyl groups was most potent and, The molecular docking indicated formation of two hydrogen bonds with Arg268 and one hydrophobic interaction with Glu322. The carbonyl oxygen of 5i interacts with Arg268 and form two hydrogen bonds having lengths 2.44 and 2.62 Å, respectively. In the same way, compounds 5a–j were appraised for DPPH free radical scavenging ability and five of them 5d, 5e, 5h, 5i and 5j were found to exhibit higher % scavenging potency compared with vitamin C, as the standard. Interesting compound 5i was again the most potent in the series. The current investigation points towards the role of naphthyl group in design of new inhibitors of melanogenesis and the antioxidants with improved efficacy.
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| 3. |
- Liu, Peijie, et al.
(author)
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Transport behavior and thermoelectric properties of SnSe/SnS heterostructure modulated with asymmetric strain engineering
- 2022
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In: Computational materials science. - : Elsevier. - 0927-0256 .- 1879-0801. ; 207
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Journal article (peer-reviewed)abstract
- Strain engineering of two-dimensional materials provides specific regulation method for the crystal structure, electric transport behavior and hence thermoelectric properties. Since the layer components of the van der Waals heterojunction exhibit discrepant response to strains, it provides a platform for manipulation of emergent electronic and thermoelectric properties. Here, motivated by the promising thermoelectric materials SnSe and its analogue, we design a specific high-promising thermoelectric candidate based on SnSe-SnS heterostructures, focusing on the strain induced asymmetric bonding-transition and its effect on thermoelectric properties. The compressed SnS/SnSe hetero-bilayer shows significantly enhanced anisotropic electrical transport properties, due to depressed carrier scattering rate along the robust weak bonding direction. In this armchair direction, extremely high power factor values (3600 μW/(cm⋅K2) for n-type and 4000 μW/(cm⋅K2) for p-type) are predicted at ∼1021 cm−3 at 700 K. We obtain a new state-of-the-art thermoelectric material with extremely high thermoelectric power factor and pave the way for strain engineering of thermoelectric van der Waals heterostructures with robust in-plane weak bonding.
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| 4. |
- Muhammad, Zahir, et al.
(author)
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Temperature Modulating Fermi Level Pinning in 2D GeSe for High‐Performance Transistor
- 2022
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In: Advanced Electronic Materials. - : John Wiley & Sons. - 2199-160X. ; 8:7
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Journal article (peer-reviewed)abstract
- 2D layered germanium selenide (GeSe) material possesses in-plane anisotropy because of low-symmetry crystal structure with a new degree of freedom for enhanced optical and electronic properties. However, their systematic vibrational and electronics properties are still under the scope to study. Herein, the vibrational properties of GeSe sheets are studied by Raman spectroscopy. Whereas, the temperature-dependent electronic band structure is studied using angle-resolved photoemission spectroscopy (ARPES) combined with density functional theory calculations. Moreover, the field-effect transistor (FET) is fabricated on a few-layer GeSe with high performance. The vibrational modes (Formula presented.) and (Formula presented.) demonstrates linear softening as the temperature increases, with temperature coefficient value associated by anharmonic phonon–phonon/electron coupling. Besides, the enhanced dielectric screening effect of long-range Coulomb and interlayer interaction is observed from bulk to monolayer. Similarly, ARPES results further show Fermi level movement toward the valance band as increased temperature represents hole doping to pining the Fermi level, which indicates superior carrier concentration for electronic properties. The fabricated FET device on six layers GeSe exhibits high carrier mobility of 52.89 cm2 V−1 s−1 with an on/off ratio above 4 × 105 at room temperature, while it decreased below the room temperature. Our results provide the important figure of merit for GeSe-based novel nanoelectronic and thermoelectric devices.
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| 5. |
- Siddique, Suniya, et al.
(author)
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Realizing High Thermoelectric Performance in p-Type SnSe Crystals via Convergence of Multiple Electronic Valence Bands
- 2022
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:3, s. 4091-4099
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Journal article (peer-reviewed)abstract
- SnSe crystals have gained considerable interest for their outstanding thermoelectric performance. Here, we achieve excellent thermoelectric properties in Sn0.99–xPbxZn0.01Se crystals via valence band convergence and point-defect engineering strategies. We demonstrate that Pb and Zn codoping converges the energy offset between multiple valence bands by significantly modifying the band structure, contributing to the enhancement of the Seebeck coefficient. The carrier concentration and electrical conductivity can be optimized, leading to an enhanced power factor. The dual-atom point-defect effect created by the substitution of Pb and Zn in the SnSe lattice introduces strong phonon scattering, significantly reducing the lattice thermal conductivity to as low as 0.284 W m–1 K–1. As a result, a maximum ZT value of 1.9 at 773 K is achieved in Sn0.93Pb0.06Zn0.01Se crystals along the bc-plane direction. This study highlights the crucial role of manipulating multiple electronic valence bands in further improving SnSe thermoelectrics.
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