共查询到20条相似文献,搜索用时 31 毫秒
1.
Irina Yu. Grubova Maria A. Surmeneva Roman A. Surmenev Erik C. Neyts 《RSC advances》2020,10(62):37800
Hydroxyapatite (HAP) is frequently used as biocompatible coating on Ti-based implants. In this context, the HAP-Ti adhesion is of crucial importance. Here, we report ab initio calculations to investigate the influence of Si incorporation into the amorphous calcium-phosphate (a-HAP) structure on the interfacial bonding mechanism between the a-HAP coating and an amorphous titanium dioxide (a-TiO2) substrate, contrasting two different density functionals: PBE-GGA, and DFT-D3, which are capable of describing the influence of the van der Waals (vdW) interactions. In particular, we discuss the effect of dispersion on the work of adhesion (Wad), equilibrium geometries, and charge density difference (CDD). We find that replacement of P by Si in a-HAP (a-Si-HAP) with the creation of OH vacancies as charge compensation results in a significant increase in the bond strength between the coating and substrate in the case of using the PBE-GGA functional. However, including the vdW interactions shows that these forces considerably contribute to the Wad. We show that the difference (Wad − Wad(vdW)) is on average more than 1.1 J m−2 and 0.5 J m−2 for a-HAP/a-TiO2 and a-Si-HAP/a-TiO2, respectively. These results reveal that including vdW interactions is essential for accurately describing the chemical bonding at the a-HAP/a-TiO2 interface.Dispersion interactions play a significant role in altering the bonding strength of the hydroxyapatite coating to the substrate, and such interactions is critical in molecular simulations. 相似文献
2.
Combining two different layered structures to form a van der Waals (vdW) heterostructure has recently emerged as an intriguing way of designing electronic and optoelectronic devices. Effects of the strain on the electronic properties of GaN/graphene heterostructure are investigated by using first-principles calculation. In the GaN/graphene heterostructure, the strain can control not only the Schottky barrier, but also contact types at the interface. Moreover, when the uniaxial strain is above −1% or the biaxial strain is above 0%, the contact type transforms to ohmic contact. These results provide a detailed understanding of the interfacial properties of GaN/graphene and help to predict the performance of the GaN/graphene heterostructure on nanoelectronics and nanocomposites.Combining two different layered structures to form a van der Waals (vdW) heterostructure has recently emerged as an intriguing way of designing electronic and optoelectronic devices. 相似文献
3.
Tingting Sui Yafei Lian Mingxia Xu Lisong Zhang Yanlu Li Xian Zhao Xun Sun 《RSC advances》2018,8(13):6931
The formation energies, charge transition levels, and electronic structures of positively charged, neutral, and negatively charged hydrogen vacancies in the NH4H2PO4 (ADP) crystal are investigated in the framework of density functional theory with local and hybrid exchange–correlation functionals. The inclusion of nonlocal exchange opens the ADP fundamental band gap by nearly 1 eV and well reproduces the experimental value. The van der Waals (vdW) interaction is found to have a major influence on the energetics of charged hydrogen vacancies in ADP. The calculated relative stability of and with vdW interaction could well explain the break point on the measured conductivity curve of the ADP crystal in the high temperature region. On the other hand, a missing H atom in the (H2PO4)− group is found to be more energetically preferable than NH4+. It could capture a hole carrier to form a molecular-type polaron with its adjacent two O atoms, and be responsible for the optical absorption under irradiation by a high-intensity laser beam.Hybrid DFT calculations with vdW correction well explain the defect-induced conductivity break of ADP in the high-temperature region. 相似文献
4.
Using ab initio calculations, we present a two-dimensional (2D) α-2D-germanene dioxide material with an ideal sp3 bonding network which possesses a large band gap up to 2.50 eV. The phonon dispersion curves and molecular dynamics (MD) simulation under the chosen parameters suggest that the novel 2D structure is stable. The dielectric function and absorption spectrum also show the consistent band gap within the electronic structure diagram, suggesting possible application as an ultraviolet light optical detector. The calculated carrier mobility of 4.09 × 103 cm2 V−1 s−1 can be observed along the x direction, which is much higher than that of MoS2 (∼3.0 cm2 V−1 s−1). Finally, we found that α-2D-germanene dioxide could potentially act as an ideal monolayer insulator in so-called van der Waals (vdW) heterostructure devices. These findings expand the potential applications of the emerging field of 2D α-2D-germanene dioxide materials in nanoelectronics.Using ab initio calculations, we present a two-dimensional (2D) α-2D-germanene dioxide material with an ideal sp3 bonding network which possesses a large band gap up to 2.50 eV. 相似文献
5.
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.The two dimensional GaN–SiS van der Waals heterostructure is a promising candidate for optoelectronic and photocatalytic water splitting. 相似文献
6.
The crystal structure of boehmite (γ-AlOOH) contains a large amount of hydrogen bonds that are joined into chains by sharing hydrogen-bond donor and acceptor oxygen atoms. The hydrogen ions in the hydrogen-bond chains are highly mobile and have complicated structural characterizations, and this feature may well be utilized for proton-conducting applications, but the mechanism is unknown without the dynamic parameters of the hydrogen-transfer processes. We propose probable hydrogen-transfer paths and compute their energy barriers using density functional theory with van der Waals density functionals, on both perfect and vacancy-containing crystal structures. It is revealed that the energy barriers are generally below 21 kJ mol−1 in a perfect crystal, and 14 kJ mol−1 in a vacancy-containing structure. The low energy barriers are indicators of the high proton conductivity of boehmite even at room temperature.Energy barriers for hydrogen-transfer processes are generally below 21 kJ mol−1 in a perfect crystal, and 14 kJ mol−1 in a vacancy-containing structure. The low energy barriers are indicators of the high proton conductivity of boehmite. 相似文献
7.
In this study, the adsorption behavior of mono-cationic acridinium derivatives on a synthetic clay mineral (Sumecton SA) was investigated. The acridinium derivatives were adsorbed on the clay surface without aggregation, as found from the changes in the absorption spectra of the acridinium derivatives with SSA and without SSA represented by two-component equilibrium systems of adsorbed and non-adsorbed components. Following the Langmuir isotherm analysis, the adsorption equilibrium constants and maximum adsorption amounts were determined for acridinium derivatives, and the Gibbs free energy change (ΔG) was calculated to be in the range of −33.8 to 40.0 kJ mol−1 from the adsorption equilibrium constants. These results indicated that the adsorption of acridinium derivatives on the clay surface was an exergonic reaction. Moreover, thermodynamic parameters such as enthalpy change (ΔH) and entropy change (ΔS) were obtained from the temperature effect experiments. For all acridinium derivatives, ΔH (from −7.82 to −26.0 kJ mol−1) and ΔS (0.047–0.088 kJ mol−1 K−1) were found to be negative and positive, respectively. It was suggested that not only electrostatic interactions, but also van der Waals forces and hydrophobic interactions played an important role in the adsorption of cationic aromatic molecules on the clay surface. Because these thermodynamic parameters showed a strong correlation with the molecular cross-sectional area of acridinium derivatives, it was suggested that the contribution of hydrophobic interactions became smaller as the molecular cross-sectional area became larger.Thermodynamic studies indicate that van der Waals and hydrophobic interactions contribute to the adsorption of mono-cationic acridinium derivatives on the clay surface. 相似文献
8.
Peng Lin Nengshen Xu Xiaolin Tan Xuhui Yang Rui Xiong Cuilian Wen Bo Wu Qilang Lin Baisheng Sa 《RSC advances》2021,12(2):998
Constructing van der Waals (vdW) heterostructures has been proved to be an excellent strategy to design or modulate the physical and chemical properties of 2D materials. Here, we investigated the electronic structures and solar cell performances of the g-C3N4/WTe2 heterostructure via first-principles calculations. It is highlighted that the g-C3N4/WTe2 heterostructure presents a type-II band edge alignment with a band gap of 1.24 eV and a corresponding visible light absorption coefficient of ∼106 cm−1 scale. Interestingly, the band gap of the g-C3N4/WTe2 heterostructure could increase to 1.44 eV by enlarging the vdW gap to harvest more visible light energy. It is worth noting that the decreased band alignment difference resulting from tuning the vdW gap, leads to a promotion of the power conversion efficiency up to 17.68%. This work may provide theoretical insights into g-C3N4/WTe2 heterostructure-based next-generation solar cells, as well as a guide for tuning properties of vdW heterostructures.g-C3N4/WTe2 heterostructure with tunable vdW gap shows a favorable solar energy conversion performance. 相似文献
9.
Wannian Zhang Ming-Yuan Zhang Kai Wang Ruixia Sun Shanlin Zhao Zhiqiang Zhang Yu-Peng He Fang Yu 《RSC advances》2021,11(45):28286
Understanding the effect of surfactant structure on their ability to modify interfacial properties is of great scientific and industrial interest. In this work, we have synthesized four amide based ionic surfactants under acidic or basic conditions, including CTHA·HCl, CTEA·HCl, CTHA−Na+ and CTEA−Na+. Experiments have proved that the anionic surfactant with polyethylene oxide groups (CTEA−Na+) had the lowest surface tension on the water/n-decane interface. Molecular dynamics simulations have been applied to investigate the structural effect on the adsorption behavior of four different surfactants. The surface tension, interface thickness, interface formation energy, density profiles, order parameters, radial distribution function on the water/n-decane interfaces were calculated and compared. During the equilibrium states, we found that the interface configuration of two cationic surfactants are almost linear while the two anionic surfactants are changed to bending shapes due to the different positions of the hydrophilic head groups. Further DFT study and wavefunction analysis of surfactants have shown that CTEA−Na+ can form stronger vdW interactions with n-decane molecules due to a more neutral electrostatic potential distribution. Meanwhile, the introduction of polyethylene oxide groups has offered more H-bonding sites and resulted in more concentrated H-bonding interactions with water molecules. The difference of weak interactions may contribute to the conformational change and finally affect the interface properties of these ionic surfactants.The difference of weak interactions may contribute to the conformational change and finally affect the interface properties of these ionic surfactants. 相似文献
10.
Using density functional theory (DFT) calculations we investigate the structural and electronic properties of a heterogeneous van der Waals (vdW) structure consisting of silicene and NiI2 single layers. We observe an interaction between the two layers with a net charge transfer from the ferromagnetic semiconductor NiI2 to silicene, breaking the inversion symmetry of the silicene structure. However, the charges flow in opposite directions for the two spin channels, which leads to a vdW heterostructure with a spin-polarized band gap between the π and π* states. The band gap can be tuned by controlling the vertical distance between the layers. The features shown by this vdW heterostructure are new, and we believe that silicene on a NiI2 layer can be used to construct heterostructures which have appropriate properties to be used in nanodevices where control of the spin-dependent carrier mobility is necessary and can be incorporated into silicon based electronics.Using density functional theory (DFT) calculations we investigate the structural and electronic properties of a heterogeneous van der Waals (vdW) structure consisting of silicene and NiI2 single layers. 相似文献
11.
An energetic ionic salt (EIS)-based cocrystal formation, cyclotetramethylene tetra-nitramine (HMX)/hydrazine 5,5′-bitetrazole-1,1′-diolate (HA·BTO), is predicted based on molecular dynamics simulations. HA·BTO is a newly-synthesized environmentally friendly energetic ionic salt with good detonation performance and low sensitivity. Calculated powder X-ray diffraction patterns and intermolecular interactions deduce the formation of the new cocrystal structure. Radial distribution function analysis suggests that hydrogen bonds and van der Waals (vdW) forces exist between the H⋯O pairs of HMX and HA·BTO, while the hydrogen bonds between the H of HA·BTO and the O of HMX play a prominent role. The cohesive energy density and mechanical properties are also analyzed. The cohesive energy density of the HMX/HA·BTO cocrystal is larger than that of the composite of HMX and HA·BTO, indicating an improvement in crystal stability by cocrystalization. Compared to both HMX and HA·BTO, HMX/HA·BTO has smaller Young modulus, bulk modulus and shear modulus values, but larger K/G values and a positive Cauchy pressure, suggesting decreased stiffness and improved ductibility. Moreover, the calculated formation energy is −405.79 kJ mol−1 at 298 K, which implies that the proposed cocrystal structure is likely to be synthesized at ambient temperature. In summary, we have predicted an EIS-based cocrystal formation in which the safety and mechanical properties of HMX have been improved via cocrystalization with HA·BTO, and this provides deep insight into the formation mechanism of the EIS-based cocrystal.An energetic ionic salt-based cocrystal formation, HMX/HA·BTO, is predicted based on molecular dynamics simulations. 相似文献
12.
The two-dimensional (2D) vertical van der Waals (vdW) stacked homojunction is an advantageous configuration for fast low-power tunneling field effect transistors (TFETs). We simulate the device performance of the sub-10 nm vertical SnSe homojunction TFETs with ab initio quantum transport calculations. The vertically stacked device configuration has an effect of decreasing leakage current when compared with its planar counterpart due to the interrupted carrier transport path by the broken connection. A subthreshold swing over four decades (SSave_4 dec) of 44.2–45.8 mV dec−1 and a drain current at SS = 60 mV dec−1 (I60) of 5–7 μA μm−1 are obtained for the optimal vertical SnSe homojunction TFET with Lg = 10 nm at a supply voltage of 0.5–0.74 V. In terms of the device''s main figures of merit (i.e., on-state current, intrinsic delay time, and power delay product), the vertical SnSe TFETs and NCTFETs outperform the 2022 and 2028 targets of the International Technology Roadmap for Semiconductors requirements for low-power application (2013 version), respectively.The vertical SnSe homojunction TFETs and NCTFETs are potential candidates for fast low-power application. 相似文献
13.
Pham T. Huong M. Idrees B. Amin Nguyen N. Hieu Huynh V. Phuc Le T. Hoa Chuong V. Nguyen 《RSC advances》2020,10(40):24127
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. 相似文献
14.
Carlo Guardiani William A. T. Gibby Miraslau L. Barabash Dmitry G. Luchinsky Peter V. E. McClintock 《RSC advances》2019,9(35):20402
Selective permeation through graphene nanopores is attracting increasing interest as an efficient and cost-effective technique for water desalination and purification. In this work, using umbrella sampling and molecular dynamics simulations with constant electric field, we analyze the influence of pore charge on potassium and chloride ion permeation. As pore charge is increased, the barrier of the potential of mean force (PMF) gradually decreases until it turns into a well split in two subminima. While in the case of K+ this pattern can be explained as an increasing electrostatic compensation of the desolvation cost, in the case of Cl− the pattern can be attributed to the accumulation of a concentration polarization layer of potassium ions screening pore charge. The analysis of potassium PMFs in terms of forces revealed a conflicting influence on permeation of van der Waals and electrostatic forces that both undergo an inversion of their direction as pore charge is increased. Even if the most important transition involves the interplay between the electrostatic forces exerted by graphene and water, the simulations also revealed an important role of the changing distribution of potassium and chloride ions. The influence of pore charge on the orientation of water molecules was also found to affect the van der Waals forces they exert on potassium.Increase of graphene pore charge determines decrease of PMF barrier that turns into well: current increases, reaches plateau and declines. 相似文献
15.
Weijing Kong Qiaolin Du Yinan Qu Changyu Shao Chaoqun Chen Jian Sun Caiyun Mao Ruikang Tang Xinhua Gu 《RSC advances》2022,12(6):3454
It is currently known that crosslinking agents can effectively improve the mechanical properties of dentin by crosslinking type I collagen. However, few scholars have focused on the influence of crosslinking agents on the collagen-mineral interface after crosslinking. Analysis of the Fourier transform infrared spectroscopy (FTIR) results showed that hydrogen bonding occurs between the tannic acid (TA) molecule and the collagen. The crosslinking degree of TA to collagen reached a maximum 41.28 ± 1.52. This study used TA crosslinked collagen fibers to successfully induce dentin biomineralization, and the complete remineralization was achieved within 4 days. The crosslinking effect of TA can improve the mechanical properties and anti-enzyme properties of dentin. The elastic modulus (mean and standard deviation) and hardness values of the remineralized dentin pretreated with TA reached 19.1 ± 1.12 GPa and 0.68 ± 0.06 GPa, respectively, which were close to those of healthy dentin measurements, but significantly higher than those of dentin without crosslinking (8.91 ± 1.82 GPa and 0.16 ± 0.01 GPa). The interface energy between the surface of collagen fibers and minerals decreased from 10.59 mJ m−2 to 4.19 mJ m−2 with the influence of TA. The current work reveals the importance of tannic acid crosslinking for dentin remineralization while providing profound insights into the interfacial control of biomolecules in collagen mineralization.Tannic acid acts as a cross-linker to promote the biomineralization of dentin and adjusts the mineralization interface through the wetting effect. 相似文献
16.
The construction of van der Waals heterostructures based on 2D polarized materials is a unique technique to achieve enhanced photocatalytic performance. We have investigated the intrinsic electric field and photocatalytic properties of the MoTe2/GeS heterostructure via first-principles calculations. The results showed that a dipole-induced electric field induced by the GeS monolayer and an interface-induced electric field induced by the interface between the GeS monolayer and the MoTe2 monolayer emerge in the 2D polarized MoTe2/GeS heterostructure. The dipole-induced electric field contributes mainly to the total intrinsic electric field. Moreover, the 2D polarized MoTe2/GeS heterostructure possesses many excellent and distinguished photocatalytic performance parameters, such as a direct semiconductor bandgap of 1.524 eV, a wide light spectrum ranging from the ultraviolet to near-infrared region with a high absorption coefficient (about 106 cm−1), a total intrinsic electric field, which reduces the probability of the recombination of photo-generated electron–hole pairs effectively, and a suitable band alignment for the water-splitting reaction. These indicate that the 2D polarized MoTe2/GeS van der Waals heterostructure is a potential novel high-efficient photocatalyst for water-splitting.The 2D polarized material-based MoTe2/GeS heterojunction would be a highly efficient photocatalyst for producing hydrogen energy. 相似文献
17.
The nonlinear optical properties of van der Waals bilayer heterostructures composed of graphene/h-BN and graphene/phosphorene nanoflakes are investigated using time-dependent density functional theory. Our calculated results show a significant enhancement of the first-hyperpolarizability value, β in heterostructures relative to the pristine nanoflakes at λ = 1064 nm. The calculated enhancement in optical nonlinearity mainly results from in-plane anisotropy induced by the interlayer electronic coupling between the adjacent nanoflake layers; a higher degree of anisotropy is induced by puckered phosphorene compared to atomically flat h-BN yielding χ(2) value corresponding to the second harmonic generation of ∼50 pm V−1 in the zigzag graphene/phosphorene bilayer heterostructure. The calculated results clearly show that graphene-based nanoflake heterostructures giving large NLO coefficients together with high electron mobility of these materials offer new opportunities as candidate materials of choice for next-generation photonics and integrated quantum technologies.The nonlinear optical properties of van der Waals bilayer heterostructures composed of graphene/h-BN and graphene/phosphorene nanoflakes are investigated using time-dependent density functional theory. 相似文献
18.
van der Waals (vdW) heterojunctions are of interest in two-dimensional electronic and optoelectronic devices. In this work, first-principles calculations were used to study the atomic and electronic properties of the MoS2/C3N vdW heterojunction. The results show that there is no overlap of the band gaps for the MoS2 and C3N monolayers in the heterojunction, indicating the MoS2/C3N vdW heterostructure has a type III alignment. The MoS2/C3N vdW heterostructure is a broken-gap heterojunction. The effects of biaxial strain and external electric field on the band structure of the vdW heterostructure were also investigated. The alignment type cannot be changed, but the band overlap can be tuned. The present work reveals that the MoS2/C3N heterostructures are quite favorable for applications in tunneling devices based on the broken-gap heterostructures.van der Waals (vdW) heterojunctions are of interest in two-dimensional electronic and optoelectronic devices. 相似文献
19.
Md. Rasidul Islam Md. Sakib Hasan Khan Md. Rayid Hasan Mojumder Sohail Ahmad 《RSC advances》2023,13(3):1943
This research unravels the photocatalytic properties of a 2D ZnO/SiC van der Waals hetero-bilayer for potential water-splitting applications by first-principles calculations. Four unique stacking patterns are considered in studying the electronic and optical properties in the presence and absence of biaxial external strain. For pattern-I and II, large negative binding energy and positive phonon frequencies are observed, denoting chemical and mechanical stabilities. Under the HSE-06 pseudo potential, the calculated bandgap value for pattern-I and II reaches 2.86 eV and 2.74 eV, respectively. 2D ZnO/SiC shows a high absorption coefficient (∼105 cm−1). The absorption peak under biaxial strain could reach ∼3.5 times the peak observed under unstrained conditions. Under strain, a shift from compressive to tensile biaxial strain (−6% to 6%) results in a bandgap decrease from 3.18 eV to 2.52 eV and 3.09 eV to 2.43 eV, for pattern-I and II, respectively. The observed strain-driven kinetic overpotential for 2D ZnO/SiC pattern-I and II easily engenders photocatalytic redox reactions. The excellent mechanical durability and strain-driven large kinetic overpotential suggest 2D ZnO/SiC heterobilayers as a prospective material for water-splitting H2-fuel production.This research unravels the photocatalytic properties of a 2D ZnO/SiC van der Waals hetero-bilayer for potential water-splitting applications by first-principles calculations. 相似文献
20.
Thi-Nga Do M. Idrees Bin Amin Nguyen N. Hieu Huynh V. Phuc Nguyen V. Hieu Le T. Hoa Chuong V. Nguyen 《RSC advances》2020,10(53):32027
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. 相似文献