Showing papers in "Physica E-low-dimensional Systems & Nanostructures in 2022"

Fabrication of a g-C3N4/MoS2 photocatalyst for enhanced RhB degradation

Abstract: The graphitic C 3 N 4 (g-C 3 N 4 ) is a new non-metallic semiconductor material , which has the advantages of high thermal, sensitive visible light response and stability. It has great application potential in the fields of hydrogen production by water decomposition, organic matter degradation, gas sensing and carbon dioxide reduction. In this article, two-dimensional (2D) g-C 3 N 4 nanosheets and their nanocomposites were prepared, and the photocatalytic degradation of organic compounds was investigated. Field emission scanning electron microscope (FESEM) test demonstrates that the thickness of g-C 3 N 4 nanosheets stripped from g-C 3 N 4 material is uniform and thin. The X-ray diffraction demonstrates that the g-C 3 N 4 nanosheet is a 3- s -triazine ring crystal structure. Furthermore, g-C 3 N 4 /MoS 2 nanocomposites were fabricated by impregnation calcination method. FESEM showed that the g-C 3 N 4 /MoS 2 nanocomposites exhibited nanosheets with uniform thickness. Transmission electron microscopy and X-ray photoelectron spectroscopy illustrated that the composites had both g-C 3 N 4 and MoS 2 components. Moreover, the experiment of photocatalytic degradation of Rhodamine B exhibited that after 90 min illumination, and the degradation efficiency of g-C 3 N 4 , g-C 3 N 4 nanosheets, MoS 2 and g-C 3 N 4 /MoS 2 nanocomposites were 80.2%, 91%, 91.5% and 99.4%, respectively. The degradation rate of g-C 3 N 4 /MoS 2 nanocomposites was 2.1 times that of g-C 3 N 4 nanosheets. Therefore, the successful combination of MoS 2 and g-C 3 N 4 has significantly improved the photocatalytic properties of g-C 3 N 4 nanosheets.

Terahertz narrowband perfect metasurface absorber based on micro-ring-shaped GaAs array for enhanced refractive index sensing

Abstract: In this paper, a narrowband perfect metasurface absorber (MSA) based on micro-ring-shaped structure GaAs array was proposed and investigated theoretically in terahertz (THz) region, which can be applicable for the enhanced refractive index (RI) sensing. Simulation results show that the proposed perfect MSA can achieve an absorbance of 99.9% at 2.213 THz and the Q-factor of about 460.08, which can be confirmed efficiently by the coupling mode theory (CMT). The perfect absorption of the designed structure is mainly contributed to the guided mode of the critical resonance coupling. The absorption properties of the proposed structure can be adjusted by changing the geometrical parameters of GaAs structure. Owing to its higher Q-factor, the proposed MSA can enhance the RI sensing application, and the sensitivity of about 1.45 THz/RIU can be achieved. The research provides a new route for the construction of the highly efficient MSA with potential applications in sensing, detecting, and imaging in THz region. • A narrowband perfect metasurface absorber (MSA) based on micro-ring-shaped GaAs array was proposed. • The MSA can achieve an absorbance of 99.9% at 2.213 THz and the Q-factor of about 481.08. • The absorption properties of the MSA can be adjusted by changing the geometrical parameters of GaAs structure. • The MSA can enhance the RI sensing application, and the sensitivity of about 1.45 THz/RIU be achieved.

Two-dimensional MgP3 monolayer with remarkably tunable bandgap and enhanced visible-light and UV optical absorptions

Abstract: Two-dimensional (2D) monolayered magnesium triphosphides (MgP3) is identified as a new member of the 2D XP3 family. Interestingly, a strain less than 8% can induce the bandgap of the MgP3 monolayer changing in a large range from 0.32 to 1.35 eV. On the basis of the first-principles calculations, the geometrical structure of the newfound MgP3 monolayer is relaxed, and the dynamical/thermal stabilities are assured by carrying out calculations of phonon dispersion and ab initio molecular dynamics simulation, respectively. The HSE06 calculations give a direct bandgap of 1.18 eV and enhanced visible-light and UV optical absorptions for the MgP 3 monolayer with strain-free. The carrier mobility is higher than those of the several previously reported XP 3 monolayers and demonstrates a significant difference between the electron and the hole carrier mobilities. Strain engineering can significantly affect both the bandgap and optical absorption. These findings indicate that the MgP3 monolayer could have potential applications of optoelectronic, photovoltaic , and photocatalytic materials or devices.

Theoretical investigation of emodin conjugated doped B12N12 nanocage by means of DFT, QTAIM and PCM analysis

Abstract: The surface-modified nanomaterials are considered effective drug carriers due to their high electronic sensitivity and reactivity towards various drug molecules. In this work, we have modified B12N12 nanocage by doping metal atoms (Al and Ga) to form AlB11N12 and GaB11N12 nanocages, and deeply scrutinized the interactions of these nanocages towards emodin (ED) drug via DFT calculations. Our calculations demonstrated that AlB11N12 and GaB11N12 show high sensitivity and reactivity towards the ED than B12N12 in both gas and solvent media. ED interacts with AlB11N12 and GaB11N12 in gas media with energies −46.69 and −51.29 kcal/mol and in solvent media with −57.50 and −47.05 kcal/mol whereas the interaction energies of ED/B12N12 system are found about −22.48 and −24.68 kcal/mol in gas and water media respectively. The adsorption process significantly effects on the HOMO and LUMO levels which leads to reduction of Eg of ED/AlB11N12 and ED/GaB11N12 approximately 42.48% and 52.03%. Thus, the electrical conductivity greatly enhanced due to the reduction of Eg which can produce electrical signal. This phenomenon implies that AlB11N12 and GaB11N12 could be used as promising electronic drug sensor for ED. Furthermore, QTAIM and RDG analysis also indicate the strong hydrogen-bonded interaction between ED and both AlB11N12, and GaB11N12.

Understanding delivery and adsorption of Flutamide drug with ZnONS based on: Dispersion-corrected DFT calculations and MD simulations

Abstract: The unique features of zinc oxide nanosheet (ZnONS) as an appropriate platform for Flutamide molecule was considered by means of density functional theory (DFT) framework with van der Waals (vdW) approximation via Perdew–Burke–Ernzerhof variant of the generalized gradient approximation (PBE-GGA) method along with double zeta polarization (DZP) basis set. The most stable model of interaction between Flutamide molecule and ZnONS is specified and adsorption energies (E ads) are assessed. In energetically favorable configuration, O atoms of –NO2 group of Flutamide interacts with a Zn atom of the ZnONS at 2.11 A with Eads of −20.616 kcal mol−1 . We have scrutinized charge analysis between species involved through famous Mulliken, Hirshfeld and Voronoi approaches. Furthermore, we have examined the density of states (DOS) and the projected density of states (PDOS) for the energetically favorable model to explore the interaction of the drug molecule with the ZnONS. Besides, quantum molecular descriptors (QMD) are also analyzed upon interaction of drug molecule on ZnONS. To deeper knowledge the details of the interaction between the Flutamide and the ZnONS, Quantum Theory of Atoms in Molecules (QTAIM) calculations are implemented. The values of ▽ 2 ρ(BCP) and H(BCP) for (Flutamide)O⋯Zn(ZnONS) at the most stable configuration are positive and G/|V| is greater than 1, it denotes the non-covalent interaction between Flutamide with ZnONS. The DFT calculation based on molecular dynamics (MD) approach are utilized to acquire a better understand into the nature of the Flutamide drug and ZnONS interactions. The MD outcomes demonstrate that when the Flutamide molecule takes longer time to link with ZnONS, the Flutamide/ZnONS complex becomes stable. Moreover, after Flutamide molecule adsorption phenomenon the electrical conductivity generates an electrical signal. The outcomes affirmed the potential of a ZnONS as a drug delivery system (DDS) for drug molecule to remedy cancer and may be an appropriate sensor for the Flutamide drug detection.

Plasmonic metasurface with quadrilateral truncated cones for visible perfect absorber

Abstract: Solar radiation is mainly concentrated in the visible and infrared spectra ranges, and its perfect absorption has great significance to solar cell, energy harvester, emitter, perfect stealth, and hot-electron device fields. In this study, we theoretically design and numerically demonstrate a highly efficient broadband visible perfect absorber (VPA) using plasmonic metasurface , which consists of quadrilateral truncated cones configuration. The electromagnetic properties of VPA are discussed by changing the geometrical parameters, especially to the absorption intensity of VPA. VPA processes perfect absorption (100%) at the wavelength of 490 nm and the minimum absorption is 99.51% at the wavelength of 772 nm. The averaged absorption is 99.91% spanned the whole visible spectrum. The excellent absorption performance is revealed by the Fabry-Perot resonance, localized surface plasmon resonance (SPR), and propagating SPR . VPA exhibits ultrahigh absorption, wide incident angle, and polarization-independent characteristics. It proves that the designed VPA has great potential in thermal photovoltaics and energy harvesting applications. • A highly efficient broadband visible perfect absorber (VPA) using plasmonic metasurface is presented. • VPA processes perfect absorption (100%) at the wavelength of 490 nm. • The average absorption is 99.91% spanned the whole visible spectrum. • The averaged absorption intensities are 99.91%, 99.8%, and 94.7% at the incident angles of 0°, 20°, and 60°, respectively. • VPA exhibits ultrahigh absorption, wide incident angle, and polarization-independent characteristics.

Design of a graphene-based multi-band metamaterial perfect absorber in THz frequency region for refractive index sensing

Abstract: In this paper, a multi-band metamaterial perfect absorber, formed by an array of combined H and U-shaped graphene stripes, is proposed. The structure is numerically simulated using the finite element method . The simulation results show that if the graphene layer's chemical potential is equal to 0.9eV, three absorption peaks are found in the proposed system's transmission spectrum at frequencies of 5.29, 6.76, and 9.1 THz with absorption coefficients of 99%, 99.8%, and 86%, respectively. Using an external DC-bias voltage which changes the chemical potential of the graphene layer, the absorption spectra of the combined absorber can be adjusted. It is also shown that the proposed absorber can act as a good refractive index sensor, with a maximum sensitivity of 1783 GHz /RIU , where RIU stands for the refractive index unit. Based on the simulation results, the proposed absorber appears to be a good candidate for applications such as biochemical sensing. • A graphene multi-band metamaterial perfect absorber formed by array of H-shapes and double U-shaped ribbons is proposed. • The finite element method is used for the simulation of the proposed device. • A maximum sensitivity of 1783 (GHz/RIU) has been achieved. • When μ c = 0.9 eV and τ = 1 ps, the proposed structure has three absorption peaks. • The absorption efficiency of the peaks are 99%, 99.8% and 86%, respectively.

Understanding delivery and adsorption of Flutamide drug with ZnONS based on: Dispersion-corrected DFT calculations and MD simulations

Abstract: The unique features of zinc oxide nanosheet (ZnONS) as an appropriate platform for Flutamide molecule was considered by means of density functional theory (DFT) framework with van der Waals (vdW) approximation via Perdew–Burke–Ernzerhof variant of the generalized gradient approximation (PBE-GGA) method along with double zeta polarization (DZP) basis set. The most stable model of interaction between Flutamide molecule and ZnONS is specified and adsorption energies (Eads) are assessed. In energetically favorable configuration, O atoms of –NO2 group of Flutamide interacts with a Zn atom of the ZnONS at 2.11 Å with Eads of −20.616 kcal mol−1. We have scrutinized charge analysis between species involved through famous Mulliken, Hirshfeld and Voronoi approaches. Furthermore, we have examined the density of states (DOS) and the projected density of states (PDOS) for the energetically favorable model to explore the interaction of the drug molecule with the ZnONS. Besides, quantum molecular descriptors (QMD) are also analyzed upon interaction of drug molecule on ZnONS. To deeper knowledge the details of the interaction between the Flutamide and the ZnONS, Quantum Theory of Atoms in Molecules (QTAIM) calculations are implemented. The values of ▽2ρ(BCP) and H(BCP) for (Flutamide)O⋯Zn(ZnONS) at the most stable configuration are positive and G/|V| is greater than 1, it denotes the non-covalent interaction between Flutamide with ZnONS. The DFT calculation based on molecular dynamics (MD) approach are utilized to acquire a better understand into the nature of the Flutamide drug and ZnONS interactions. The MD outcomes demonstrate that when the Flutamide molecule takes longer time to link with ZnONS, the Flutamide/ZnONS complex becomes stable. Moreover, after Flutamide molecule adsorption phenomenon the electrical conductivity generates an electrical signal. The outcomes affirmed the potential of a ZnONS as a drug delivery system (DDS) for drug molecule to remedy cancer and may be an appropriate sensor for the Flutamide drug detection.

Ab-initio modelling for gas sensor device: based on Y-doped SnS2 monolayer

Abstract: In this work, we have investigated the adsorption behavior of small gas molecules like CO, NO, CO2, NO2 and NH3 on Yttrium(Y) doped SnS2 monolayer by employing density functional theory simulations. Y-doping effect on the physicochemical properties of the pure SnS 2 monolayer is first studied, then adsorption mechanism was analyzed by adsorption energy, charge transfer, structural properties, magnetic properties , electronic properties such as density of states, charge density and band structure. In addition, the transport properties are evaluated to propound the gas adsorption response of Yttrium (Y) doped -SnS 2 system on the device level. The result shows that all the gas molecules were strongly adsorbed on the Yttrium (Y) site of the Y-doped SnS2 monolayer through formation of strong covalent bonds and Y- doped SnS2 monolayers can be employed as a potential candidate for gas sensing applications. Here in, to evaluate the sensing capability, the molecular model of the adsorption systems was constructed, and density functional theory (DFT) was used to calculate the adsorption behavior of these gases.

Broadband and thermally switchable reflective metasurface based on Z-shape InSb for terahertz vortex beam generation

Abstract: In this paper, a broadband and thermally switchable reflective metasurface based on InSb Z-shape resonator (ZSR) structure was proposed for the vortex beam generation in terahertz (THz) region. Numerical simulation results indicate that the operation frequency range and efficiency will be basically unchanged when the external environment temperature increases from 300 K to 340 K, but gradually decreased when the temperature decreases from 300 K to 240 K. More specifically, the proposed InSb metasurface can transform the normal incident circular-polarization (CP) wave to its orthogonal component with conversion coefficient over 0.8 from 0.65 THz to 1.66 THz (relative bandwidth of 87.4%) after reflection when the temperature is changed from 300 K to 340 K. However, the bandwidth will be narrowed and conversion coefficient will be limited with the temperature decreases from 300 K to 240 K. The full 2π phase shift could be obtained at operation frequency by rotating the InSb ZSR structure along the wave propagation direction. Taking advantages of the above characteristics, the reflective THz vortex beams carrying orbital angular momentum (OAM) with topological charge of l = ±1, ±2, and ±3 at the temperature of 300 K over a broadband range can be achieved. In addition, thermal switchable effect of the vortex beams with topological charge of l = 2 at three different frequencies also can be observed. The further numerical results also indicate that the generated reflective THz vortex beams have high mode purity by the designed InSb metasurface. Our work provides a potentially efficient method for the development and integration of the broadband and switchable wavefront controlling devices.

Nonlocal free vibration characteristics of power-law and sigmoid functionally graded nanoplates considering variable nonlocal parameter

Abstract: In this study, the effects of the variable nonlocal parameters on the free vibration of power-law and sigmoid functionally graded nanoplates are investigated using a simple inverse hyperbolic shear deformation theory incorporating with nonlocal elasticity theory. The novelty of this study is that the nonlocal parameter is assumed to vary smoothly through the thickness of the functionally graded nanoplates. The governing equations of motion are established using the variation form of Hamilton's principle, and they are solved via Navier's closed-form solution. Some verification studies are carried out to demonstrate the accuracy and efficiency of the proposed algorithm in predicting the free vibration behavior of functionally graded nanoplates. The effects of some parameters such as the aspect ratio, the side-to-thickness ratio, the power-law index as well as the variation of the nonlocal parameters are also considered carefully. The results show that the variation of the nonlocal parameter plays significant effects on the free vibration response of the functionally graded nanoplates. The influence of the nonlocal parameters on the free vibration of various kinds of functionally graded nanoplates is completely different, it depends on the variation of the material ingredients across the thickness of the functionally graded nanoplates.

Theoretical investigation of electronic and optical properties of the 2D-MoSe2/GaN heterostructure nanosheet

Abstract: Two-dimensional (2D) metal dichalcogenides have recently fascinated the consideration of researchers due to their exceptional electronic and optical characteristics. Despite this, the higher photo-generated carrier recombination rate constrains their technical utilization. Implementing a promising approach may result in the construction of 2D heterostructures , which may improve photocatalytic activity . This article presents the electronic structure, optical, thermodynamical, and photocatalytic characteristics of MoSe 2/GaN heterostructures. In 2D-MoSe2/GaN, the MoSe2 and GaN nanosheets interact through the van der Waals forces with a binding energy of −1.72 eV. The electronic structures of the heterostructure confirm that it is a type-II indirect band-gap semiconductor with a band-gap of 1.71 eV. Work function studies revealed that the studied heterojunctions exhibit enhanced photocatalytic activity.

A density functional theory study on favipiravir drug interaction with BN-doped C60 heterofullerene

Abstract: We have performed to study the possibility of a stable interaction between favipiravir drug molecule and BN-doped C60 (CBN) heterofullerene. The structural, electronic, reactivity and optical properties for the mentioned interactions are examined in detail. Adsorption energies between favipiravir drug and CBN heterofullerene are calculated in the range of −3.41 and −23.95 kcal/mol. The adsorption energy of configuration A is −23.95 kcal/mol means that B–O bonding in configuration A is stronger than that of B–N and C–O in other configurations. The results mean that the O atom of favipiravir interacts strongly with B atom of the heterofullerene. The smallest value of the E g (0.4 eV) means that charge transfer can easily occur between occupied and unoccupied orbitals of the favipiravir and CBN heterofullerene. The charge transfer from adsorbed the favipiravir to CBN heterofullerene was confirmed by the WBI and FBO analyses. From the absorption peaks obtained UV–visible (UV–vis) spectra indicate that all configurations can absorb in the visible light region. Finally, these results may guide drug delivery systems.

A square-lattice D-shaped photonic crystal fiber sensor based on SPR to detect analytes with large refractive indexes

Abstract: With the booming of nanotechnology, surface plasmon resonance (SPR) technology has become one of the most active research hotspots in optical sensing. In this work, a square-lattice photonic crystal fiber (PCF) sensor based-SPR with indium tin oxide (ITO) coating is investigated to detect analytes with large refractive indexes (RIs) varying from 1.380 to 1.405. To confirm the dependence of sensing characteristics on the geometrical parameters, the finite element method (FEM) is applied to modeling and numerical simulation. The big air holes in cladding cause a birefringence effect, which is stronger with y-polarization mode. In this way, the maximum and average spectral sensitivity of 60,000 and 18,400 nm/RIU can be achieved with resolution in 10−6 order. Furthermore, this sensor which provides a high-sensitivity detection in large analyte RIs with near-infrared region (1500–2800 nm) shows excellent figure of merit (FOM), signal-to-noise ratio (SNR) and detection limit (DL). There will be more extensive space and prospect for progression in biochemical safety with DNA hybridization, blood glucose analysis and organic chemical samples detection involved.

Strain modulation of electronic and optical properties of monolayer MoSi2N4

Abstract: The strain engineering is an important approaches to modulate the electronic and optical properties of materials . Recently, a new two dimensional material monolayer MoSi 2N4 has been successfully synthesized with excellent electronic performance. The electronic properties of monolayer MoSi2N4 without and with in-plane strain are systematically investigated by first-principles calculation. The calculation results reveal monolayer MoSi2N4 is an indirect bandgap semiconductor with bandgap 1.74 eV (PBE) and 2.31 eV (HSE06), but it can be transformed to a direct bandgap under the certain in-plane strain, such as 3% and 4% biaxial compressive strain. In-plane strain can effectively modulate the band structure, bandgap, and the carrier effective mass. Furthermore, the optical properties of unstrained and transformed to direct bandgap situations are calculated. The light absorption capacity of monolayer MoSi 2N4 is stronger in the ultraviolet band, and can be changed when it is transformed to a direct bandgap. The electrical and optical properties can be modulated by strain engineering, making it is a promising candidate of strain-modulated optoelectronic devices .

A density functional theory study on favipiravir drug interaction with BN-doped C60 heterofullerene

Abstract: We have performed to study the possibility of a stable interaction between favipiravir drug molecule and BN-doped C 60 (CBN) heterofullerene. The structural, electronic, reactivity and optical properties for the mentioned interactions are examined in detail. Adsorption energies between favipiravir drug and CBN heterofullerene are calculated in the range of −3.41 and −23.95 kcal/mol. The adsorption energy of configuration A is −23.95 kcal/mol means that B–O bonding in configuration A is stronger than that of B–N and C–O in other configurations. The results mean that the O atom of favipiravir interacts strongly with B atom of the heterofullerene. The smallest value of the E g (0.4 eV) means that charge transfer can easily occur between occupied and unoccupied orbitals of the favipiravir and CBN heterofullerene. The charge transfer from adsorbed the favipiravir to CBN heterofullerene was confirmed by the WBI and FBO analyses. From the absorption peaks obtained UV–visible (UV–vis) spectra indicate that all configurations can absorb in the visible light region. Finally, these results may guide drug delivery systems. • An adsorption occurs between CBN heterofullerene and favipiravir drug molecule. • The attraction and repulsion interactions between heterofullerene and drug are explored by RDG analyses. • The charge transfers are confirmed by WBI and FBO analyses. • All configurations can absorb in the visible light region. • CBN heterofullerene can be used as a drug delivery system.

Theoretical investigation of electronic and optical properties of the 2D-MoSe2/GaN heterostructure nanosheet

Abstract: Two-dimensional (2D) metal dichalcogenides have recently fascinated the consideration of researchers due to their exceptional electronic and optical characteristics. Despite this, the higher photo-generated carrier recombination rate constrains their technical utilization. Implementing a promising approach may result in the construction of 2D heterostructures, which may improve photocatalytic activity. This article presents the electronic structure, optical, thermodynamical, and photocatalytic characteristics of MoSe2/GaN heterostructures. In 2D-MoSe2/GaN, the MoSe2 and GaN nanosheets interact through the van der Waals forces with a binding energy of −1.72 eV. The electronic structures of the heterostructure confirm that it is a type-II indirect band-gap semiconductor with a band-gap of 1.71 eV. Work function studies revealed that the studied heterojunctions exhibit enhanced photocatalytic activity.

Development of an amperometric biosensor for dopamine using novel mesoporous silicon nanoparticles fabricated via a facile stain etching approach

Abstract: Mesoporous silicon (PSi) modified glassy carbon electrode (GCE) was studied for the first time for efficient detection of dopamine (DA). A facile stain etching method was used to synthesize the single crystalline PSi nanoparticles, which was confirmed by the SAED. The morphological study of PSi NPs by FESEM and TEM showed the random distribution of pores with less than 25 nm pore size. The X-ray diffraction (XRD), Raman spectra , and Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were also used in characterizing the PSi NPs. The-as fabricated PSi NPs modified GCE biosensor can measure a wide range of dopamine (0.5–333.3 μM) in phosphate buffer solution (PBS) with a sensitivity value of 0.2715 μAμM −1cm−2 with an extremely low limit of detection (LOD) of 3.2 nM. This non-enzymatic dopamine biosensor was also tested for the possible impact of common interfering substances, which showed very good selectivity . The current modified electrode was further employed to analyze human blood serums and dopamine hydrochloride injection samples to detect DA, where it showed very acceptable analytical results. Additionally, the current PSi/GCE biosensor showed exceptional reproducibility, repeatability, and long-term stability.

Development of an amperometric biosensor for dopamine using novel mesoporous silicon nanoparticles fabricated via a facile stain etching approach

Abstract: Mesoporous silicon (PSi) modified glassy carbon electrode (GCE) was studied for the first time for efficient detection of dopamine (DA). A facile stain etching method was used to synthesize the single crystalline PSi nanoparticles, which was confirmed by the SAED. The morphological study of PSi NPs by FESEM and TEM showed the random distribution of pores with less than 25 nm pore size. The X-ray diffraction (XRD), Raman spectra, and Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were also used in characterizing the PSi NPs. The-as fabricated PSi NPs modified GCE biosensor can measure a wide range of dopamine (0.5–333.3 μM) in phosphate buffer solution (PBS) with a sensitivity value of 0.2715 μAμM−1cm−2 with an extremely low limit of detection (LOD) of 3.2 nM. This non-enzymatic dopamine biosensor was also tested for the possible impact of common interfering substances, which showed very good selectivity. The current modified electrode was further employed to analyze human blood serums and dopamine hydrochloride injection samples to detect DA, where it showed very acceptable analytical results. Additionally, the current PSi/GCE biosensor showed exceptional reproducibility, repeatability, and long-term stability.

Electronic structure, optical and thermoelectric properties of Ge2SeS monolayer via first-principles study

Abstract: The electronic, optical and thermoelectric properties of the Ge 2SeS monolayer were detailed using the first-principle calculations. The dynamic stability of the Ge2SeS structure monolayer has been confirmed by the phonon dispersion curve. Our electronic calculations indicate that the Ge2 SeS monolayer is a semiconductor at equilibrium state with an indirect bandgap lower/larger than that of the GeS/GeSe monolayer calculated by generalized gradient approximation (GGA) of Perdew Burke Ernzerhof (PBE) functional. The optical properties such as dielectric constant, reflectivity , extinction coefficient, and absorption coefficient versus the energy were investigated. In addition, the thermoelectric properties are obtained using the semi-classical Boltzmann transport theory. The results show a large Seebeck coefficient of 2470 μV/K at 300K, the electronic figure of merit ( ZTe) is 0.91 in Ge2SeS monolayer at 300 K. The predicted optical and thermoelectric properties could make the Ge2SeS monolayer a potential candidate for applications in optoelectronic and energy conversion technologies at room temperature.

A comparative DFT study on prospective application of C24, Si12C12, B12N12, B12P12, Al12N12, and Al12P12 nanoclusters as suitable anode materials for magnesium-ion batteries (MIBs)

Abstract: In the present study, the interaction of both Mg and Mg2+ species with C24, Si12C12, B12N12, B12P12, Al12N12, and Al12P12 fullerene-like cage structures are systematically investigated through density functional theory framework. Accordingly, the interaction energies and energy gaps are considered for these systems. The studied cages show remarkable cell voltage of 2.7–3.7 V, mainly owing to great differences in the interaction energies of Mg and Mg2+ adduct systems. Since design of high energy density materials is an attractive domain for researchers, the obtained results might be useful in designing new materials with even better energy storage density.

Electronic structure, optical and thermoelectric properties of Ge2SeS monolayer via first-principles study

Abstract: The electronic, optical and thermoelectric properties of the Ge 2 SeS monolayer were detailed using the first-principle calculations. The dynamic stability of the Ge 2 SeS structure monolayer has been confirmed by the phonon dispersion curve. Our electronic calculations indicate that the Ge 2 SeS monolayer is a semiconductor at equilibrium state with an indirect bandgap lower/larger than that of the GeS/GeSe monolayer calculated by generalized gradient approximation (GGA) of Perdew Burke Ernzerhof (PBE) functional. The optical properties such as dielectric constant, reflectivity , extinction coefficient, and absorption coefficient versus the energy were investigated. In addition, the thermoelectric properties are obtained using the semi-classical Boltzmann transport theory. The results show a large Seebeck coefficient of 2470 μV/K at 300K, the electronic figure of merit ( ZT e ) is 0.91 in Ge 2 SeS monolayer at 300 K. The predicted optical and thermoelectric properties could make the Ge 2 SeS monolayer a potential candidate for applications in optoelectronic and energy conversion technologies at room temperature. • First-principles calculations on electronic structure, optical and thermoelectric properties of Ge 2 SeS monolayer. • Dynamic stability of the Ge 2 SeS structure monolayer has been confirmed by the phonon dispersion curve. • Ge 2 SeS monolayer is a semiconductor with an indirect bandgap of 1.47 eV. • A high electronic figure of merit (ZT e ) of 0.91 have been predicted in Ge 2 SeS monolayer at 300 K. • Optical properties of the Ge 2 SeS monolayer have been investigated in agreement with reported experimental results.

First-principles calculations of optical properties of 2D CaFBr and BaFBr monolayers

Abstract: Advanced works have been significantly committed to the progression of next-generation optoelectronic plans based on 2D materials, due to their novel optical properties that are distinctive from those of 3D materials. In this Way, we apply the generalized gradient approximation in the framework of density functional theory to examine the optical properties of 2D halide XFBr (where X = Ba or Ca), such as absorption, conductivity, refractive index, and dielectric function. According to our DFT–PBE calculations, the static dielectric constants of BaFBr and CaFBr are 1.40 and 1.50, respectively, which can be used as a good dielectric material since materials with high dielectric constants are helpful in the fabrication of high-value capacitors. The reflectivity index spectrum for each layer reveals that the reflectivity is crucial in the visible–ultraviolet area up to 25 eV, showing that it has potential as a wonderful sheet material.

Preparation of carbon quantum dots using bike pollutant soot: Evaluation of structural, optical and moisture sensing properties

Abstract: Humidity sensor-based carbon quantum dots (CQDs) have been prepared using waste bike pollutant soot. The synthesized CQDs were characterized using a UV–Visible light chamber, UV–Visible spectroscopy , photoluminescence spectroscopy, TEM, and FTIR research. Initially, the sample was exposed in a closed chamber to UV–Visible light, which produced green luminescence. The photo luminescent spectrometer revealed the emission of green spectra as well as the approximate size of the CQDs. TEM and HRTEM confirmed the spherical shaped particles ∼2 nm in size. The FTIR spectra indicated the existence of a functional group. The sensing element was fabricated using the spin coating method on a borosilicate substrate and was used as a humidity sensor. Carbon quantum dots have excellent humidity sensing properties, as evidenced by measurements of sensitivity, ageing effect, repeatability, reaction, and recovery times. Many humidity sensors based on metal oxides, semiconductors, and polymers have been investigated and developed. The novelty of the work, electrical humidity sensor has been proposed using the waste pollutant soot. • The sustainable, cost effective and rapid synthesis of pollutant bike soot carbon quantum dot. • The prepared were imperiled for electrical humidity sensing. • The first, second, third and fourth layers of sensing characteristics are reported. • The beauty of the experiment is that the electrical humidity sensor is proposed to design by using the waste pollutant soot.

Strain and external electric field modulation of the electronic and optical properties of GaN/WSe2 vdWHs

Abstract: Recently, the GaN/WSe2 van der Waals heterostructures (vdWHs) were successfully synthesized in experiments, providing a pathway for designing the nitride semiconductor materials with transition metal dichalcogenides (TMDs) heterostructures. To insight into the physical mechanism of the GaN/WSe2 vdWHs, the geometrical, electronic and optical properties of the systems are examined based on the first-principles calculations. Our results indicate that the GaN/WSe2 heterostructures exhibit typical type-I band alignment with the bandgap values around 2.20 eV at HSE06 level. Biaxial and external electric field not only can cause the evolution of the band alignment to transfer from type-I to type-II, but also can realize semiconductor-metal transition. In addition, compressive strain enhances the light absorption intensity in the ultraviolet region and tensile strain enables the GaN/WSe2 vdWHs to appear a distinct peak in infrared (IR) region. These flexible and tunable characteristics of type-I GaN/WSe2 vdWHs are more convenient for the design of IR detectors, photovoltaic and light emission devices.

Effect of oxygen atoms adsorption and doping on hexagonal boron nitride

Abstract: h-BN is an excellent material, which can be used as insulating coating in aerospace field. However, it was reported that oxygen is inevitably attached to surface of h-BN when it works in oxygen-rich environment. In particularly, oxygen is doped when h-BN has defects. In this study, the effect of oxygen adsorption and doping on monolayer h-BN is studied by first principles . We found that mono-oxide, meta-dioxide and meta-trioxide can destroy the symmetry to a relatively large extent than para-dioxide, which reduces the band gap. Meanwhile, oxygen can repair the lattice when h-BN has a nitrogen defect, while multiple oxygen-doped will result in lattice distortion of different degrees when there are many defects. In particularly, the band gap of single-oxygen doping based on diatomic vacancy is relatively small. This study is helpful to evaluate the properties of h-BN in atomic-oxygen-rich environment. And it has certain significance for the application of h-BN in band gap engineering.

Characterization and antibacterial activity of Ti doped ZnO nanorods prepared by hydrazine assisted wet chemical route

Abstract: In this study, a simple hydrazine assisted wet chemical method was used to prepare pure and Ti doped ZnO nanorods . The structural properties of pure and Ti doped ZnO nanorods were investigated by XRD analysis. Williamson-Hall (W–H) method was used to determine the crystallite size , strain and dislocation density of the samples. TEM analysis revealed rod like morphology for Ti doped ZnO nanoparticles . The presence of elements such as Zn, Ti and O of the doped sample was confirmed by EDS. XPS spectrum suggests that Ti 4+ ions well substitute Zn 2+ ions in doped nanocrystal . The Raman study further established the formation of ZnO wurtzite structure in both pure and Ti doped ZnO nanorods. The band gap of pure and Ti doped ZnO nanorods were estimated by the Tauc relation as 3.03 eV and 2.91 eV respectively. From the PL spectra, it is observed that the intensity of the polychromatic defect emissions of Ti doped ZnO nanorods is higher than pure ZnO, with some additional defect emissions. The antibacterial activity of Ti doped ZnO nanorods slightly decreased against gram-positive and gram-negative bacteria when compared to pure ZnO. • Synthesis of pure and Ti doped ZnO nanorods by a facile hydrazine assisted wet chemical method. • Confirmation of substitution of Ti 4+ ions into Zn 2+ ions in doped nanocrystal from XPS spectrum. • The band gap of pure and Ti doped ZnO nanorods were estimated by the Tauc relation as 3.03 eV and 2.91 eV. • Intensity of the polychromatic defect emissions of Ti doped ZnO nanorods is higher than pure ZnO. • The antibacterial activity of Ti doped ZnO nanorods is slightly lower than pure ZnO and higher than certain doped ZnO nanostructures.

Theoretical treatment of interaction of pyrazinamide with graphene and h-SiC monolayer: A DFT-D3 study

Abstract: Functionalization of nanostructured materials with organic molecules is a hopefully advanced technology in nanobiotechnology to develop horizontal bioinorganic nanodevices for pharmaceutical applications. In the present study, by using dispersion modified density functional theory (DFT‒D3) calculations, we provide a versatile exploration on the functionalization of h‒SiC and graphene monolayer with a pyrazinamide drug. We present a detailed description of the structural geometries, the interaction strength, the charge transfers, and the interacting host-guest complexes with various approaching configurations. Finally, for the most stable complexes, the quantum atom in molecule (AIM) theory analysis was performed to better account for the interaction nature in a molecule‒surface interface. The use of h‒SiC monolayer combined with pyrazinamide was found to be more effective for biofunctionalization with the interaction energy of −33.92 kcal/mol compared with pyrazinamide‒graphene complex with interaction energy of −13.24 kcal/mol. The AIM analysis indicated the highly polar attraction accompanied with partially covalent bonding in pyrazinamide/h‒SiC system while the interaction nature in pyrazinamide attached to graphene surface was found to be electrostatic and physisorption. We have intensely confidence that our findings will stimulate future research works focused on functionalized nano-bio materials applications for drug delivery, nano-bio sensors, nanomedicine, and relevant biological field of interests.

First-principles study on N2, H2, O2, NO, NO2, CO, CO2, and SO2 gas adsorption properties of the Sc2CF2 monolayer

Abstract: In this work, we systematically investigated the gas adsorption properties of N2, H2, O2, NO, NO2, CO, CO2, and SO2 on the MXene Sc2CF2 monolayer using first-principles calculations. We determined structural geometries, adsorption energies, bandgap, charge transfer, density of states, and charge density difference of adsorption systems. We found that all N2, H2, O2, CO, CO2, SO2, NO, and NO2 molecules are physisorbed on the Sc2CF2 monolayer. The adsorption energies show that the Sc2CF2 monolayer exhibits low adsorption selectivity in respect of the studied gas molecules. Spin-polarized DOS indicates the transitions of non-magnetic pristine MXene Sc2CF2 to magnetic systems after O2, NO and NO2 adsorptions. Especially, we observed the semiconductor-to-semimetal transition of the Sc2CF2 monolayer by NO adsorption, while the adsorptions of CO, CO2, H2, N2, SO2, NO2 and O2 molecules do not change the conductive behavior of the Sc2CF2 monolayer. Our results suggest that the Sc2CF2 monolayer is a novel potential sensing nanomaterial for detecting NO gas.

Study of photoionization cross section and binding energy of shallow donor impurity in multilayered spherical quantum dot

Abstract: In the framework of the effective mass approximation and by using the finite element method , we have studied the simultaneous effects of position dependent effective mass (PDEM) and dielectric function on the shallow donor impurity binding energy and photoionization cross section in a multilayered spherical quantum dot . We have also investigated the influence of conduction band nonparabolicity and polaronic mass on the both binding energy and photoionization cross section (PCS). The obtained results have shown that the nonparabolicity and polaronic mass effects enhance the binding energy and photoionization cross section. Furthermore, it can be concluded from this research that the binding energy and the PCS are strongly dependent on the geometrical parameters, and PDEM. Changes in binding energy and photoionization cross section have physical reasons, which are discussed in details. • The photoionization cross section (PCS) and the binding energy are strongly dependent on the width of the structure layers. • The conduction band nonparabolicity and the polaronic mass effects enhance the binding energy and reduce the PCS peak magnitude. • The dependence of the dielectric function ε ( r ) on the electron coordinates makes the amplitude peak of the PCS take high values.