Tunable electronic structures, Rashba splitting, and optical and photocatalytic responses of MSSe-PtO2 (M = Mo, W) van der Waals heterostructures

Binding energies, AIMD simulation and phonon spectra confirm both the thermal and dynamical stabilities of model-I and model-II of MSSe-PtO2 (M = Mo, W) vdWHs. An indirect type-II band alignment in both the models of MSSe-PtO2 vdWHs and a larger Rashba spin splitting in model-II than in model-I provide a platform for experimental design of MSSe-PtO2 vdWHs for optoelectronics and spintronic device applications. Transfer of electrons from the MSSe layer to the PtO2 layer at the interface of MSSe-PtO2 vdWHs makes MSSe (PtO2) p(n)-type. Large absorption in the visible region of MoSSe-PtO2 vdWHs, while blue shifts in WSSe-PtO2 vdWHs are observed. In the case of model-II of MSSe-PtO2 vdWHs, a further blue shift is observed. Furthermore, the photocatalytic response shows that MSSe-PtO2 vdWHs cross the standard water redox potentials confirming their capability to split water into H+/H2 and O2/H2O.

Correction: First principles study of electronic and optical properties and photocatalytic performance of GaN-SiS van der Waals heterostructure

[This corrects the article DOI: 10.1039/D1RA06011B.].

Correction: Revealing the electronic, optical and photocatalytic properties of PN-M2CO2 (P = Al, Ga; M = Ti, Zr, Hf) heterostructures

[This corrects the article DOI: 10.1039/D3NA00017F.].

Revealing the electronic, optical and photocatalytic properties of PN-M2CO2 (P = Al, Ga; M = Ti, Zr, Hf) heterostructures

Using DFT, the electronic structure, optical, and photocatalytic properties of PN (P = Ga, Al) and M₂CO₂ (M = Ti, Zr, Hf) monolayers and their PN-M₂CO₂ van der Waals heterostructures (vdWHs) are investigated. Optimized lattice parameters, bond length, bandgap, conduction and valence band edges show the potential of PN (P = Ga, Al) and M₂CO₂ (M = Ti, Zr, Hf) monolayers in photocatalytic applications, and the application of the present approach to combine these monolayers and form vdWHs for efficient electronic, optoelectronic and photocatalytic applications is shown. Based on the same hexagonal symmetry and experimentally achievable lattice mismatch of PN (P = Ga, Al) with M₂CO₂ (M = Ti, Zr, Hf) monolayers, we have fabricated PN-M₂CO₂ vdWHs. Binding energies, interlayer distance and AIMD calculations show the stability of PN-M₂CO₂ vdWHs and demonstrate that these materials can be easily fabricated experimentally. The calculated electronic band structures show that all the PN-M₂CO₂ vdWHs are indirect bandgap semiconductors. Type-II[-I] band alignment is obtained for GaN(AlN)-Ti₂CO₂[GaN(AlN)-Zr₂CO₂ and GaN(AlN)-Hf₂CO₂] vdWHs. PN-Ti₂CO₂ (PN-Zr₂CO₂) vdWHs with a PN(Zr₂CO₂) monolayer have greater potential than a Ti₂CO₂(PN) monolayer, indicating that charge is transfer from the Ti₂CO₂(PN) to PN(Zr₂CO₂) monolayer, while the potential drop separates charge carriers (electron and holes) at the interface. The work function and effective mass of the carriers of PN-M₂CO₂ vdWHs are also calculated and presented. A red (blue) shift is observed in the position of excitonic peaks from AlN to GaN in PN-Ti₂CO₂ and PN-Hf₂CO₂ (PN-Zr₂CO₂) vdWHs, while significant absorption for photon energies above 2 eV for AlN-Zr₂CO₂, GaN-Ti₂CO₂ and PN-Hf₂CO₂, give them good optical profiles. The calculated photocatalytic properties demonstrate that PN-M₂CO₂ (P = Al, Ga; M = Ti, Zr, Hf) vdWHs are the best candidates for photocatalytic water splitting.

Structural, electronic and thermoelectric properties of GeC and MXO (M = Ti, Zr and X = S, Se) monolayers and their van der Waals heterostructures

Vertical stacking of two-dimensional materials into layered van der Waals heterostructures is considered favourable for nanoelectronics and thermoelectric applications. In this work, we investigate the structural, electronic and thermoelectric properties of GeC and Janus monolayers MXO (M = Ti, Zr; X = S, Se) and their van der Waals (vdW) heterostructures using first-principles calculations. The values of binding energies, interlayer distances and thermal stability confirm the stability of these vdW heterostructures. The calculated band structure shows that GeC monolayer have a direct band gap while MXO (M = Ti, Zr; X = S, Se) and their van der Waals heterostructures show indirect band nature. Partial density of states confirms the type-II band alignment of GeC–MXY vdW heterostructures. Our results shows that ZrSeO (GeC) monolayers and GeC–ZrSO vdW heterostructures have higher power factor, making them promising for thermoelectric device applications.

Calculated Seebeck coefficient (a) and (b) electrical conductivity (c) and (d) and power factor (e) and (f) of GeC–TiSO, GeC–TiSeO, GeC–ZrSO and GeC–ZrSeO vdW heterostructures for 300 K and 800 K, respectively.

Correction: First principles study of electronic properties and optoelectronic performance of type-II SiS/BSe heterostructure

Correction for ‘First principles study of electronic properties and optoelectronic performance of type-II SiS/BSe heterostructure’ by Shah Saleemullah Sabir et al., New J. Chem., 2023, 47, 4537–4542, https://doi.org/10.1039/D2NJ06198H.

A first principles study of a van der Waals heterostructure based on MS2 (M = Mo, W) and Janus CrSSe monolayers

The strategy of stacking two-dimensional materials for designing van der Waals heterostructures has gained tremendous attention in realizing innovative device applications in optoelectronics and renewable energy sources. Here, we performed the first principles calculations of the geometry, optoelectronic and photocatalytic performance of MS₂-CrSSe (M = Mo, W) vdW heterostructures. The mirror asymmetry in the Janus CrSSe system allows the designing of two models of the MS₂-CrSSe system by replacing S/Se atoms at opposite surfaces in CrSSe. The feasible configurations of both models of the MS₂-CrSSe system are found energetically, dynamically and thermally stable. The studied heterobilayers possess an indirect type-I band alignment, indicating that the recombination of photogenerated electrons and holes in the CrSSe monolayer is hence crucial for photodetectors and laser applications. Remarkably, a red-shift in the optical absorption spectra of MS₂-CrSSe makes them potential candidates for light harvesting applications. More interestingly, all heterobilayers (except W(Mo)S₂-CrSSe of model-I(II)) reveal appropriate band edge positions of the oxidation and reduction potentials of the photocatalysis of water dissociation into H⁺/H₂ and O₂/H₂O at pH = 0. These results shed light on the practical design of the MS₂-CrSSe system for efficient optoelectronic and photocatalytic water splitting applications.

First principles study of optoelectronic and photocatalytic performance of novel transition metal dipnictide XP2 (X = Ti, Zr, Hf) monolayers

Low cost and highly efficient two dimensional materials as photocatalysts are gaining much attention to utilize solar energy for water splitting and produce hydrogen fuel as an alternative to deal with the energy crisis and reduce environmental hazards. First principles calculations are performed to investigate the electronic, optical and photocatalytic properties of novel two dimensional transition metal dipnictide XP₂ (X = Ti, Zr, Hf) monolayers. The studied single layer XP₂ is found to be dynamically and thermally stable. TiP₂, ZrP₂ and HfP₂ systems exhibit semiconducting nature with moderate indirect band gap values of 1.72 eV, 1.43 eV and 2.02 eV, respectively. The solar light absorption is found to be in energy range of 1.65–3.3 eV. All three XP₂ systems (at pH = 7) and the HfP₂ monolayer (at pH = 0) that straddle the redox potentials, are promising candidates for the water splitting reaction. These findings enrich the two dimensional family and provide a platform to design novel devices for emerging optoelectronic and photovoltaic applications.

Low cost and highly efficient two dimensional materials as photocatalysts are gaining much attention to utilize solar energy for water splitting and produce hydrogen fuel as an alternative to deal with the energy crisis and reduce environmental hazards.

Intriguing interfacial characteristics of the CS contact with MX2 (M = Mo, W; X = S, Se, Te) and MXY ((X ≠ Y) = S, Se, Te) monolayers

Using (hybrid) first principles calculations, the electronic band structure, type of Schottky contact and Schottky barrier height established at the interface of the most stable stacking patterns of the CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) MS vdWH are investigated. The electronic band structures of CS–MX₂ and CS–MXY MS vdWH seem to be simple sum of CS, MX₂ and MXY monolayers. The projected electronic properties of the CS, MX₂ and MXY layers are well preserved in CS–MX₂ and CS–MXY MS vdWH. Their smaller effective mass (higher carrier mobility) render promising prospects of CS–WS₂ and CS–MoSeTe as compared to other MS vdWH in nanoelectronic and optoelectronic devices, such as a high efficiency solar cell. In addition, we found that the effective mass of holes is higher than that of electrons, suggesting that these heterostructures can be utilized for hole/electron separation. Interestingly, the MS contact led to the formation of a Schottky contact or ohmic contact, therefore we have used the Schottky Mott rule to calculate the Schottky barrier height (SBH) of CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) MS vdWH. It was found that CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) (in both model-I and -II) MS vdWH form p-type Schottky contacts. These p-type Schottky contacts can be considered a promising building block for high-performance photoresponsive optoelectronic devices, p-type electronics, CS-based contacts, and for high-performance electronic devices.

Electronic band structure, type of Schottky contact and Schottky barrier height established at the interface of the CS–MX₂ (M = Mo, W; X = S, Se, Te) and CS–MXY ((X ≠ Y) = S, Se, Te) MS vdWH.

Intriguing electronic, optical and photocatalytic performance of BSe, M2CO2 monolayers and BSe-M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures

Using density functional (DFT) theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M₂CO₂ (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M₂CO₂ (M = Ti, Zr, Hf) van der Waals (vdW) heterostructures. Optimized lattice constant, bond length, band structure and bandgap values, effective mass of electrons and holes, work function and conduction and valence band edge potentials of BSe and M₂CO₂ (M = Ti, Zr, Hf) monolayers are in agreement with previously available data. Binding energies, interlayer distance and Ab initio molecular dynamic simulations (AIMD) calculations show that BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures are stable with specific stacking and demonstrate that these heterostructures might be synthesized in the laboratory. The electronic band structure shows that all the studied vdW heterostructures have indirect bandgap nature – with the CBM and VBM at the Γ–K and Γ-point of BZ for BSe–Ti₂CO₂, respectively; while for BSe–Zr₂CO₂ and BSe–Hf₂CO₂ vdW heterostructures the CBM and VBM lie at the K-point and Γ-point of BZ, respectively. Type-II band alignment in BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures prevent the recombination of electron–hole pairs, and hence are crucial for light harvesting and detection. Absorption spectra are investigated to understand the optical behavior of BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures, where the lowest energy transitions are dominated by excitons. Furthermore, BSe–M₂CO₂ (M = Ti, Zr, Hf) vdW heterostructures are found to be potential photocatalysts for water splitting at pH = 0, and exhibit enhanced optical properties in the visible light zones.

Using density functional theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M₂CO₂ (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M₂CO₂ (M = Ti, Zr, Hf) van der Waals heterostructures.

First principles study of electronic and optical properties and photocatalytic performance of GaN-SiS van der Waals heterostructure

The vertical stacking of two-dimensional materials via van der Waals (vdW) interaction is a promising technique for tailoring the physical properties and fabricating potential devices to be applied in the emerging fields of materials science and nanotechnology. The structural, electronic and optical properties and photocatalytic performance of a GaN-SiS vdW heterostructure were explored using first principles calculations. The most stable stacking configuration found energetically stable, possesses a direct staggered band gap, which is crucial for separating photogenerated charged carriers in different constituents and is efficacious for solar cells. Further, the charge transfer occurred from the SiS to GaN layer, indicating that SiS exhibits p-type doping in the GaN-SiS heterobilayer. Interestingly, a systematic red-shift was observed in the optical absorption spectra of the understudy heterobilayer system. Moreover, the conduction band edge and valence band edge of the monolayers and corresponding heterostructure were located above and below the standard redox potentials for photocatalytic water splitting, making these systems promising for water dissociation for hydrogen fuel production. The results provide a route to design the GaN-SiS vdW heterostructure for the practical realization of next-generation light detection and energy harvesting devices.

First-principles study of the electronic structures and optical and photocatalytic performances of van der Waals heterostructures of SiS, P and SiC monolayers

Designing van der Waals (vdW) heterostructures of two-dimensional materials is an efficient way to realize amazing properties as well as open up opportunities for applications in solar energy conversion, nanoelectronic and optoelectronic devices. The electronic structures and optical and photocatalytic properties of SiS, P and SiC van der Waals (vdW) heterostructures are investigated by (hybrid) first-principles calculations. Both binding energy and thermal stability spectra calculations confirm the stability of these heterostructures. Similar to the corresponding parent monolayers, SiS–P (SiS–SiC) vdW heterostructures are found to be indirect type-II bandgap semiconductors. Furthermore, absorption spectra are calculated to understand the optical behavior of these systems, where the lowest energy transitions lie in the visible region. The valence and conduction band edges straddle the standard redox potentials of SiS, P and SiC vdW heterostructures, making them promising candidates for water splitting in acidic solution.

The electronic structures and optical and photocatalytic properties of SiS, P and SiC van der Waals (vdW) heterostructures are investigated by (hybrid) first-principles calculations.

Stacking effects in van der Waals heterostructures of blueP and Janus XYO (X = Ti, Zr, Hf: Y = S, Se) monolayers

Using first-principles calculations, the geometry, electronic structure, optical and photocatalytic performance of blueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers and their corresponding van der Waal heterostructures in three possible stacking patterns, are investigated. BlueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers are indirect bandgap semiconductors. A tensile strain of 8(10)% leads to TiSeO(ZrSeO) monolayers transitioning to a direct bandgap of 1.30(1.61) eV. The calculated binding energy and AIMD simulation show that unstrained(strained) blueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers and their heterostructures are thermodynamically stable. Similar to the corresponding monolayers, blueP-XYO (X = Ti, Zr, Hf: Y = S, Se) vdW heterostructures in three possible stacking patterns are indirect bandgap semiconductors with staggered band alignment, except blueP-TiSeO vdW heterostructure, which signifies straddling band alignment. Absorption spectra show that optical transitions are dominated by excitons for blueP and XYO (X = Ti, Zr, Hf; Y = S, Se) monolayers and the corresponding vdW heterostructures. Both E VB and E CB in TiSO, ZrSO, ZrSeO and HfSO monolayers achieve energetically favorable positions, and therefore, are suitable for water splitting at pH = 0, while TiSeO and HfSeO monolayers showed good response for reduction and fail to oxidise water. All studied vdW heterostructures also show good response to any produced O2, while specific stacking reduces H+ to H2.

Two-dimensional blue phosphorene–BAs vdW heterostructure with optical and photocatalytic properties: a first-principles study

In this work, we investigated the electronic, optical and photocatalytic properties of a blue phosphorene–BAs (BlueP–BAs) vdW heterostructure using first-principles calculations.

Type-I band alignment of BX-ZnO (X = As, P) van der Waals heterostructures as high-efficiency water splitting photocatalysts: a first-principles study

In this work, we perform first-principles calculations to examine the electronic, optical and photocatalytic properties of the BX–ZnO (X = As, P) heterostructures. The interlayer distance and binding energy of the most energetically favorable stacking configuration are 3.31 Å and −0.30 eV for the BAs–ZnO heterostructure and 3.30 Å and −0.25 eV for the BP–ZnO heterostructure. All the stacking patterns of the BX–ZnO heterostructures are proved to have thermal stability by performing AIMD simulations. The BAs–ZnO and BP–ZnO heterostructures are semiconductors with direct band gaps of 1.43 eV and 2.35 eV, respectively, and they exhibit type-I band alignment, which make them suitable for light emission applications with the ultra-fast recombination between electrons and holes. Both the BAs–ZnO and BP–ZnO heterostructures can exhibit a wider optical absorption range for visible-light owing to their reduced band gaps compared with the isolated BAs, BP and ZnO monolayers. The band alignment of both the BAs–ZnO and BP–ZnO heterostructures can straddle the water redox potential and they would have better performances owing to the direct band gap and the reduced band gap. All these findings demonstrate that the BX–ZnO heterostructures can be considered as potential photocatalysts for water splitting.

In this work, we perform first-principles calculations to examine the electronic, optical and photocatalytic properties of the BX–ZnO (X = As, P) heterostructures.

van der Waals heterostructures based on MSSe (M = Mo, W) and graphene-like GaN: enhanced optoelectronic and photocatalytic properties for water splitting

The geometric structure, electronic, optical and photocatalytic properties of MSSe-g-GaN (M = Mo, W) van der Waals (vdW) heterostructures are investigated by performing first-principles calculations. We find that the MoSSe-g-GaN heterostructure exhibits type-II band alignment for all stacking patterns. While the WSSe-g-GaN heterostructure forms the type-II or type-I band alignment for the stacking model-I or model II, respectively. The average electrostatic potential shows that the potential of g-GaN is deeper than the MSSe monolayer, leading to the formation of an electrostatic field across the interface, causing the transfer of photogenerated electrons and holes. Efficient interfacial formation of interface and charge transfer reduce the work function of MSSe-g-GaN vdW heterostructures as compared to the constituent monolayer. The difference in the carrier mobility for electrons and holes suggests that these heterostructures could be utilized for hole/electron separation. Absorption spectra demonstrate that strong absorption from infrared to visible light in these vdW heterostructures can be achieved. Appropriate valence and conduction band edge positions with standard redox potentials provide enough force to drive the photogenerated electrons and holes to dissociate water into H+/H2 and O2/H2O at pH = 0.

A first-principles study of electronic structure and photocatalytic performance of GaN-MX2 (M = Mo, W; X= S, Se) van der Waals heterostructures

Modeling novel van der Waals (vdW) heterostructures is an emerging field to achieve materials with exciting properties for various devices. In this paper, we report a theoretical investigation of GaN-MX2 (M = Mo, W; X= S, Se) van der Waals heterostructures by hybrid density functional theory calculations. Our results predicted that GaN-MoS2, GaN-MoSe2, GaN-WS2 and GaN-WSe2 van der Waals heterostructures are energetically stable. Furthermore, we find that GaN-MoS2, GaN-MoSe2 and GaN-WSe2 are direct semiconductors, whereas GaN-WS2 is an indirect band gap semiconductor. Type-II band alignment is observed through PBE, PBE + SOC and HSE calculations in all heterostructures, except GaN-WSe2 having type-I. The photocatalytic behavior of these systems, based on Bader charge analysis, work function and valence and conduction band edge potentials, shows that these heterostructures are energetically favorable for water splitting.

Electronic properties and enhanced photocatalytic performance of van der Waals heterostructures of ZnO and Janus transition metal dichalcogenides

Vertical stacking of two-dimensional materials into layered van der Waals heterostructures has recently been considered as a promising candidate for photocatalytic and optoelectronic devices because it can combine the advantages of the individual 2D materials. Janus transition metal dichalcogenides (JTMDCs) have emerged as an appealing photocatalytic material due to the desirable electronic properties. Hence, in this work, we systematically investigate the geometric features, electronic properties, charge density difference, work function, band alignment and photocatalytic properties of ZnO-JTMDC heterostructures using first-principles calculations. Due to the different kinds of chalcogen atoms on both sides of JTMDC monolayers, two different possible stacking patterns of ZnO-JTMDC heterostructures have been constructed and considered. We find that all these stacking patterns of ZnO-JTMDC heterostructures are dynamically and energetically feasible. Moreover, both ZnO-MoSSe and ZnO-WSSe heterostructures are indirect band gap semiconductors and present type-I and type-II band alignments for model-I and model-II, respectively. The Rashba spin polarization of the ZnO-WSSe heterostructure for model-I is greater than that in the others. Furthermore, valence (conduction) band edge potentials are calculated to understand the photocatalytic behavior of these systems. Energetically favorable band edge positions in ZnO-Janus heterostructures make them suitable for water splitting at zero pH. We found that the ZnO-Janus heterostructures are promising candidates for water splitting with conduction and valence band edges positioned just outside of the redox interval.

Computational insights into structural, electronic and optical characteristics of GeC/C2N van der Waals heterostructures: effects of strain engineering and electric field

Vertical heterostructures from two or more than two two-dimensional materials are recently considered as an effective tool for tuning the electronic properties of materials and for designing future high-performance nanodevices. Here, using first principles calculations, we propose a GeC/C₂N van der Waals heterostructure and investigate its electronic and optical properties. We demonstrate that the intrinsic electronic properties of both GeC and C₂N monolayers are quite preserved in GeC/C₂N HTS owing to the weak forces. At the equilibrium configuration, GeC/C₂N HTS forms the type-II band alignment with an indirect band gap of 0.42 eV, which can be considered to improve the effective separation of electrons and holes. Besides, GeC/C₂N vdW-HTS exhibits strong absorption in both visible and near ultra-violet regions with an intensity of 10⁵ cm⁻¹. The electronic properties of GeC/C₂N HTS can be tuned by applying an electric field and vertical strains. The semiconductor to metal transition can be achieved in GeC/C₂N HTS in the case when the positive electric field of +0.3 V Å⁻¹ or the tensile vertical strain of −0.9 Å is applied. These findings demonstrate that GeC/C₂N HTS can be used to design future high-performance multifunctional devices.

Vertical heterostructures from two or more than two two-dimensional materials are recently considered as an effective tool for tuning the electronic properties of materials and for designing future high-performance nanodevices.

Electronic structures, and optical and photocatalytic properties of the BP–BSe van der Waals heterostructures

The combination of two-dimensional materials in the form of van der Waals (vdW) heterostructures has been shown to be an effective method for designing electronic and optoelectronic equipment.

Van der Waals heterostructures of SiC and Janus MSSe (M = Mo, W) monolayers: a first principles study

Favorable stacking patterns of two models with alternative orders of chalcogen atoms in SiC-MSSe (M = Mo, W) vdW heterostructures are investigated using density functional theory calculations. Both model-I and model-II of the SiC-MSSe (M = Mo, W) vdW heterostructures show type-II band alignment, while the spin orbit coupling effect causes considerable Rashba spin splitting. Furthermore, the plane-average electrostatic potential is also calculated to investigate the potential drops across the heterostructure and work function. The imaginary part of the dielectric function reveals that the first optical transition is dominated by excitons with high absorption in the visible region for both heterostructures. Appropriate band alignments with standard water redox potentials enable the capability of these heterostructures to dissociate water into H⁺/H₂ and O₂/H₂O.

Using DFT calculations, we have investigated the electronic structure, Rashba effect, optical and photocatalytic performance of SiC-MSSe (M = Mo, W) van der Waals heterostructures with different stacking patterns of chalcogen atoms.

Effects of electric field and strain engineering on the electronic properties, band alignment and enhanced optical properties of ZnO/Janus ZrSSe heterostructures

The formation of van der Waals heterostructures (vdWHs) have recently emerged as promising structures to make a variety of novel nanoelectronic and optoelectronic devices. Here, in this work, we investigate the structural, electronic and optical features of ZnO/ZrSSe vdWHs for different stacking patterns of ZnO/SeZrS and ZnO/SZrSe by employing first-principles calculations. Binding energy and ab initio molecular dynamics calculations are also employed to confirm the structural and thermal stability of the ZnO/ZrSSe vdWHs for both models. We find that in both stacking models, the ZnO and ZrSSe layers are bonded via weak vdW forces, leading to easy exfoliation of the layers. More interestingly, both the ZnO/SeZrS and ZnO/SZrSe vdWHs posses type-II band alignment, making them promising candidates for the use of photovoltaic devices because the photogenerated electrons–holes are separated at the interface. The ZnO/ZrSSe vdWHs for both models possess high performance absorption in the visible and near-infrared regions, revealing their use for acquiring efficient photocatalysts. Moreover, the band gap values and band alignments of the ZnO/ZrSSe for both models can be adjusted by an electric field as well as vertical strains. There is a transformation from semiconductor to metal under a negative electric field and tensile vertical strain. These findings demonstrate that ZnO/ZrSSe vdWHs are a promising option for optoelectronic and nanoelectronic applications.

Here, in this work, we investigate the structural, electronic and optical features of ZnO/ZrSSe vdWHs for different stacking patterns of ZnO/SeZrS and ZnO/SZrSe by employing first-principles calculations.

Effects of different surface functionalization on the electronic properties and contact types of graphene/functionalized-GeC van der Waals heterostructures

Constructing vertical heterostructures by placing graphene (Gr) on two-dimensional materials has recently emerged as an effective way to enhance the performance of nanoelectronic and optoelectronic devices.

Electronic structure, optoelectronic properties and enhanced photocatalytic response of GaN–GeC van der Waals heterostructures: a first principles study

In this work, we systematically studied the electronic structure and optical characteristics of van der Waals (vdW) heterostructure composed of a single layer of GaN and GeC using first principles calculations. The GaN–GeC vdW heterostructure exhibits indirect band gap semiconductor properties and possesses type-II energy band arrangement, which will help the separation of photogenerated carriers and extend their lifetime. In addition, the band edge positions of the GaN–GeC heterostructure meet both the requirements of water oxidation and reduction energy, indicating that the photocatalysts have the potential for water decomposition. The GaN–GeC heterostructure shows obvious absorption peaks in the visible region, leading to the efficient use of solar energy. Tensile and compressive strains of up to 10% are also proposed. Tensile strain leads to an increase in the blue shift of optical absorption, whereas a red shift is observed in the case of the compressive strain. These fascinating characteristics make the GaN–GeC vdW heterostructure a highly effective photocatalyst for water splitting.

In this work, we systematically studied the electronic structure and optical characteristics of van der Waals (vdW) heterostructure composed of a single layer of GaN and GeC using first principles calculations.

Electronic and photocatalytic properties of two-dimensional boron phosphide/SiC van der Waals heterostructure with direct type-II band alignment: a first principles study

Designing van der Waals (vdW) heterostructures of two-dimensional materials is an efficient way to realize amazing properties as well as opening opportunities for applications in solar energy conversion and nanoelectronic and optoelectronic devices. In this work, we investigate the electronic, optical, and photocatalytic properties of a boron phosphide–SiC (BP–SiC) vdW heterostructure using first-principles calculations. The relaxed configuration is obtained from the binding energies, inter-layer distance, and thermal stability. We show that the BP–SiC vdW heterostructure has a direct band gap with type-II band alignment, which separates the free electrons and holes at the interface. Furthermore, the calculated absorption spectra demonstrate that the optical properties of the BP–SiC heterostructure are enhanced compared with those of the constituent monolayers. The intensity of optical absorption can reach up to about 10⁵ cm⁻¹. The band edges of the BP–SiC heterostructure are located at energetically favourable positions, indicating that the BP–SiC heterostructure is able to split water under working conditions of pH = 0–3. Our theoretical results provide not only a fascinating insight into the essential properties of the BP–SiC vdW heterostructure, but also helpful information for the experimental design of new vdW heterostructures.

We investigate the structural, electronic, optical and photocatalytic properties of boron phosphide and SiC monolayers and their corresponding van der Waals heterostructure by density functional theory.

Ellipsometric-based novel DNA biosensor for label-free, real-time detection of Bordetella parapertussis

Pertussis (or whooping cough) is a contagious disease mainly affecting infants and children and predominantly caused by Bordetella pertussis followed by Bordetella parapertussis. B. parapertussis causes a milder cough but usually symptomatically appears like B. pertussis infection. Thus the epidemiology of illness caused by B. parapertussis is not well understood. In this study, a sensitive and specific method for the rapid diagnosis of B. parapertussis is presented. The covalent immobilization of thiol-terminated DNA oligonucleotides (ss DNA SAM) on a silicon surface by disulfide bond formation is investigated with atomic force microscopy (AFM) and ellipsometry. The measurements indicated an average layer thickness of 5 ± 0.84 nm for 2 μg/μl concentration and 24 h incubation time. This thickness changed to 8.4 ± 0.92 nm for the same concentration (2 μg/μl) by altering the incubation time to 48 h. Ellipsometric data recorded before and after hybridization of B. parapertussis revealed an increase in mean grain area from 91 nm2 to 227 nm2 and a change in the refractive index from 1.489 to 1.648 for 2 μg/μl B. parapertussis, respectively. This change in the refractive index was used to evaluate the amount of adsorbed molecules and their density. The results showed that the density of adsorbed molecules increased from 0.2 to 0.97 g/cm3 after B. parapertussis attachment, respectively. To confirm the hybridization of B. parapertussis to ss DNA SAM, the ds DNA SAM was denatured and the ss DNA SAM surface was reproduced with an average height variation of 6.42 ± 0.75 nm. This showed the stability of the DNA film that can be tuned by varying the concentration and incubation time, thus providing a robust method for the label-free detection of B. parapertussis other than routinely used PCR detection.

Forecasting the critical role of intermittent therapies for the control of bone resorption

BACKGROUND

Osteoporosis is a chronic metabolic disease characterized by an imbalance of bone resorption and formation, leading to bone fragility and increased susceptibility to fracture. Parathyroid hormone is approved therapy for the treatment of osteoporosis.

METHODS

The intermittent therapy of parathyroid hormone requires accurate administration. Meta-analysis is conducted to draw a clear picture of the impact of intermittent therapy and dose rates relative to time, on the osteoporotic patients. A novel mathematical model is presented in this article synchronised with the parametric values, depicted from meta-analysis.

FINDINGS

Results obtained from the mathematical model are in close agreement with the results obtained from the clinical trials. The model can be used to forecast the drug potency and dosage rates, to control the vicious cycle of osteoporosis.

INTERPRETATIONS

The intermittent administration of parathyroid hormone, rather than the continuous administration, is more effective, furthermore it is also concluded that a mathematical model, linked with the extensive literature of clinical trials, using meta-analysis can help in drug administration and future clinical studies of drug development.

Tailoring the structural and electronic properties of an SnSe2/MoS2 van der Waals heterostructure with an electric field and the insertion of a graphene sheet

van der Waals heterostructures by stacking different two-dimensional materials are being considered as potential materials for nanoelectronic and optoelectronic devices because they can show the most potential advantages of individual 2D materials.

Optoelectronic and solar cell applications of Janus monolayers and their van der Waals heterostructures

Janus monolayers and their van der Waals heterostuctures are investigated by hybrid density functional theory calculations.

Band alignment and optical features in Janus-MoSeTe/X(OH)2 (X = Ca, Mg) van der Waals heterostructures

van der Waals heterostructures can be effectively used to enhance the electronic and optical properties and extend the application range of two-dimensional materials.

Assessing the association between unstimulated whole salivary flow rate (UWSFR) and oral health status among healthy adult subjects: A cross-sectional study

BACKGROUND

This study aimed to test the association between the unstimulated whole salivary flow rate (UWSFR) and the oral health status represented by dental and gingival status among healthy adult subjects.

MATERIAL AND METHODS

This work was a cross-sectional study of patients attending the undergraduate dental clinics at AlFarabi College for Dentistry and Nursing, Riyadh, Saudi Arabia. The study population consisted of 502 systemically healthy adults aged 18-35 years. UWSFR was collected for all study participants and expressed as ml/min. Oral health status was estimated using the Community Periodontal Index (CPI) and the Oral Hygiene Index-Simplified (OHI-S). The number of decayed teeth and the number of available teeth were also calculated to evaluate dental status.

RESULTS

The mean UWSFR was 0.42 (±0.3) ml/min, and the male participants significantly had more UWSFR than the females. UWSFR was significantly affected by CPI, OHI-S, body mass index (BMI) and gender as indicated in the univariate analysis. However, multiple regression analysis revealed that only gender was a significant predictor of UWSFR. The male subjects were shown to have a higher average of 0.133 ml/min than the females.

CONCLUSIONS

High BMI scores, moderate-to-severe gingivitis and low level of oral hygiene increased UWSFR. However, further longitudinal studies are recommended to test the role of salivary cytokine levels to validate the exact association between the UWSFR and the oral health status.

Electronic structure, optical and photocatalytic performance of SiC–MX2 (M = Mo, W and X = S, Se) van der Waals heterostructures

The stacking of monolayers in the form of van der Waals heterostructures is a useful strategy for band gap engineering and the control of dynamics of excitons for potential nano-electronic devices.

Testicular cancer: The usage of central review for pathology diagnosis of orchiectomy specimens

BACKGROUND

Radical orchiectomy specimens present a unique set of challenges for pathology assessment owing to their rarity and complexity. This study compares second opinion pathology reports generated at a single, large academic institution to primary reports from outside hospitals.

METHODS

A database search was conducted for orchiectomy cases that were sent to our institution for management of testicular cancer from 2014 to 2015. Cases sent for consultation without a finalized diagnosis from the outside hospitals were excluded. A total of 221 consecutive cases were evaluated for comparison of final diagnoses between the outside institution and central pathology review.

RESULTS

This study revealed significant discrepancy involving multiple parameters between original and second opinion pathology reports. Of 221 cases of germ cell tumors assessed, 31% showed some discrepancy of histologic subtype. Overall, reporting of lymphovascular invasion changed in 22% of cases; of those, initially called positive 23% were changed to negative and of those initially called negative 12% were changed to positive. Although the overall discrepancy for spermatic cord invasion was 9%, an initial positive diagnosis was negated 35% of the time. The pathologic stage was altered in 23% of cases, mostly secondary to differences interpreting lymphovascular and spermatic cord invasion.

CONCLUSION

Pathologists evaluating orchiectomy specimens should be aware of the major pitfalls in classification and staging, many of which may affect patient management.

Investigation on the structural, dielectric and impedance analysis of manganese substituted cobalt ferrite i.e., Co1−xMnxFe2O4 (0.0 ≤ x ≤ 0.4)

The microstructure and cation distribution of Co_1−xMnxFe₂O₄ were investigated and correlated with their electrical properties. Here, Mn substitution enhances the resistive properties which make them favorable for high-frequency applications.

Handling and reporting of orchidectomy specimens with testicular cancer: areas of consensus and variation among 25 experts and 225 European pathologists

AIMS

The handling and reporting of testicular tumours is difficult due to their rarity.

METHODS AND RESULTS

A survey developed by the European Network of Uro-Pathology (ENUP) and sent to its members and experts to assess the evaluation of testicular germ cell tumours. Twenty-five experts and 225 ENUP members replied. Areas of disagreement included immaturity in teratomas, reported by 32% of experts but 68% of ENUP. Although the presence of rete testis invasion was reported widely, the distinction between pagetoid and stromal invasion was made by 96% of experts but only 63% of ENUP. Immunohistochemistry was used in more than 50% of cases by 68% of ENUP and 12% of experts. Staging revealed the greatest areas of disagreement. Invasion of the tunica vaginalis without vascular invasion was interpreted as T1 by 52% of experts and 67% of ENUP, but T2 by the remainder. Tumour invading the hilar adipose tissue adjacent to the epididymis without vascular invasion was interpreted as T1: 40% of experts, 43% of ENUP; T2: 36% of experts, 30% of ENUP; and T3: 24% of experts, 27% of ENUP.

CONCLUSIONS

There is remarkable consensus in many areas of testicular pathology. Significant areas of disagreement included staging and reporting of histological types, both of which have the potential to impact on therapy.