查看更多>>摘要：The perovskite CaSnO3/g-C3N4 heterostructure nanocomposite was successfully prepared via facile solid-state route. The properties of morphology, structural, optical, functional, elemental, surface, electrochemical and photocatalytic performances were investigated. The synthesised CaSnO3 (CS) nanoparticles were grafted on the g-C3N4 nanosheets and their photocatalytic performance were determined. The introduction of g-C3N4 possesses solid-solid intimately contacted interfaces with CS that provides more transport paths and effectively improve the separation of photogenerated electrons and holes (e -/h+). Thus, the formation of CaSnO3/g-C3N4 (CGN) heterostructures exhibits with tunable optical bandgap and suppresses the charge recombination process that leads to improve the photocatalytic efficiency. Compared with bare CS the CGN photocatalyst achieves 95% of degradation efficiency over methylene blue (MB) dye in 120 min of UV-visible light irradiation. The possible photocatalytic degradation mechanism was discussed. Furthermore, the CGN photocatalyst has been utilized for 4 repeated runs of experiments which shows good stability and reusability after the degradation experiments.
查看更多>>摘要：Graphene oxide can have a massive influence on industries related to concrete and construction in the coming years. Due to the oxygenated capabilities connected to the aromatic structure, it has an improved ability to disperse in mixes in comparison to the other graphene-based materials. Very few researchers have given their idea about the influence of graphene oxide plus fibers on the durability and mechanical behavior of cement -based composites. Five different mixes were developed with utilization of graphene oxide (0%, 0.03%, 0.06%, 0.09% and 0.12% by cement weight) and 2% of steel fibers was added by binder weight. Experimental tests were performed related to mechanical and water permeation characteristics. The concrete mix with 0.12% of graphene oxide has displayed a significant result in terms of mechanical properties and other durability testing in contrast to the other sample mixtures. The permeability and sorptivity of the fiber-strengthened concrete samples in the utilization of graphene oxide were noted to have decreased with increment of graphene oxide content in the mixes in comparison to the reference sample. The synthesized graphene oxide was structurally categorized with the help of FT-IR, EDX, and XRD tests. Microstructural behavior was assessed with the help of XRD spectra on sample cured at 90 days, and the concrete quality was assessed with an ultrasonic pulse velocity test. The study showed that M5 mix (0.12% GO and 2% steel fibers) enhanced compressive and split tensile strength up to 56% and 37%, M5 mix also showed highest average velocity for UPV test and lower values for sorptivity test which indicates improved mechanical properties, durability and reduced porosity. Thus, concrete with GO and steel fibers can be confidently used in building application as sustainable and economic construction material.
查看更多>>摘要：& nbsp;This work investigates the fatigue behaviors of diamond-like carbon (DLC) films by conducting cyclic tensile tests and interfacial fatigue tests via molecular dynamics. It is found that the strength of DLC films is reduced with the increasing cycle number due to the irreversible sp(3)-sp(2) transition of carbon atoms induced by tensile deformation. Regions with high sp(2)C fraction are easy to deform owing to their weak strength, thus the atomic strains are almost localized in such regions. The weakest region is regarded as the defect of the films and suffers from the most severe strain localization. As a result, many sp(3)C atoms are transformed into sp(2) hybridization in the defect, destroying the integrity of sp(3)C network. Hence, the film failure occurs in the defect because of its badly degraded strength. Furthermore, interfacial fatigue of DLC films is induced by the sp(3)-sp(2) transition during the cyclic tensile tests.
查看更多>>摘要：On the basis of the Density functional theory (DFT) combined with non-equilibrium Green's function (NEGF), we have investigated the application potential of the boron, nitrogen and phosphorus co-doped seven-atom-wide armchair graphene nanoribbons field effect transistor (7-AGNR-FET). The transfer characteristics indicate that the gate voltage (VG) can modulate the electronic transport properties of 7-AGNR FET, and the ION/IOFF ratio reaches 128.67. When a positive drain voltage (VD) is applied, the device exhibits appreciate working behavior with a saturation drain-source current (IDS) of 76.21 mu A. Transmission pathways, transmission spectra and Molecular projection self-consistent Hamiltonian (MPSH) are calculated to explain the variations in current including negative differential resistance (NDR) effect under negative VD. The negative VG affects the height of the channel barrier and causes the rectifying effect. Moreover, band structures and projected density of states (PDOS) shows the performances of devices strongly depend on doping positions. This NPN-doped device simulates the structure of MOSFET as realistically as possible, and it possesses promising applications in memory device and rectifier of carbon-based integrated circuits.
查看更多>>摘要：In this study, Gd and Fe doped La1-xGdxNi1-yFeyO3 NPs were synthesized by co-precipitation and their nano composites (NCs) with reduced graphene oxide (r-GO) were fabricated by ultra-sonication approach. The as fabricated La1-xGdxNi1-yFeyO3/r-GO was characterized by Raman scattering, thermogravimetric analysis (TGA) and X-ray diffraction (XRD), scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX), Brunauer-Emmett-Teller (BET) techniques along with electrical conductivity and photocatalytic studies. Analysis revealed that the NPs had distorted rhombohedral geometry and their crystallite size was in the range of 19-27 nm. The surface area of La1-xGdxNi1-yFeyO3/r-GO NCs increased from 67 to 153 m(2)/g by doping and adding r-GO. Two probe current-voltage (I-V) analysis shows the electrical conductivity of the material improved from 5.2 x 10(-2) S/m to 4.8 x 10(5) S/m by doping and adding r-GO. The photocatalytic performance of LaNiO3, La1-xGdxNi1-yFeyO3/r-GO NPs and La1-xGdxNi1-yFeyO3/r-GO/r-GO NCs was evaluated by degrading methyl green (MG) dye under solar light irradiation. Results revealed that the LaNiO3 and La1-xGdxNi1-yFeyO3 NPs degraded up to 38.1% and 62.3% MG dye under solar irradiation for 70 min. It was observed that La1-xGdxNi1-yFeyO3/r-GO NCs furnished 93.8% higher MG dye compared to LaNiO3, La1-xGdxNi1-yFeyO3/r-GO NCs had excellent degradation efficiency due to the combined effect of doping Gd and Fe and adding r-GO. This was due to the defect in the structure of La1-xGdxNi1-yFeyO3/r-GO, which inhibited the recombination of charge carrier species. NCs with excellent electrical conductivity and photocatalytic activity could have potential applications as a photocatalyst under solar light irradiation.
查看更多>>摘要：Through first-principles calculations, we employed anisotropic compression to T-carbon and identified several carbon allotropes. Among them, we predict a novel body-centered tetragonal carbon allotrope with space group I4(1)/amd (No. 141), in which sixteen carbon atoms comprise four-and five-and eight-membered rings within a unit cell; we name it as bct-C-16-II. Phonon spectrum calculations exhibit that it is dynamically stable under pressure up to at least 100 GPa. This bct-C-16-II is energetically more stable than T-carbon and the previously proposed bct-C-16-I, although it has higher energy than graphite or diamond. Our calculations also show that bct-C-16-II may be super-hard with Vickers hardness around 55 GPa, comparable to cubic boron nitride. Its ideal tensile and shear strength is calculated to be around 75 and 43 GPa, respectively. We simulated the trans-formation pathway of importance from T-carbon to this novel bct-C-16-II phase. The energy barrier is estimated to be around 0.187 eV/atom, which provides a possible approach to synthesize it. The achievement of other carbon allotropes indicates that the tetrahedral units in T-carbon are not very strong under anisotropic strains that T-carbon might be considered as a good precursor to synthesize other carbon materials. The discovery of this new phase may enrich our knowledge of carbon materials and their formation mechanisms.
查看更多>>摘要：Element decomposition is a promising modification technique for enhancing the photocatalytic activity of TiO2. Firstly, (i) It may accelerate photogenerated electron-hole separation as electron traps, (ii) broaden the sunlight absorption region into the visible range and promote surface electron excitation by plasmon resonances excited under visible light and (iii) modify the surface performance of semiconductors. Herein, we describe the intro-duction of carbon dots (CDs) as solid-state electron mediator on TiO2 sheets (TNs) via a highly effective hydrothermal process. The as-prepared CDs/TNs nanocomposites was measured by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy analysis. The results proved that CDs were firmly scattered in the TNs interface. Furthermore, the resultant CDs/TNs nanocomposites exhibited remarkable photocatalytic activity for the degradation of different model pollutants under visible light, which is considerably superior to that of bare TNs. The enhanced photocatalytic activity highlights that CDs can promote the separation and migration efficiency of photoexcited electron-hole pairs. The striking stability of CDs/TNs was investigated by performing five successive cycles of degradation of Congo red. Moreover, the degradation intermediates of three pollutants were monitored by liquid chromatography-tandem mass spectrometry, and potential removal pathways are proposed. We firmly believe that this work may inspire new insights and approaches for the design of highly efficient photocatalysts.
查看更多>>摘要：Since graphene was discovered in 2004, two-dimensional (2D) carbon materials have been investigated for many applications including as energy storage materials, gas sensors, and heterogeneous catalysts. Recently, a new type of carbon material, termed a biphenylene network has been successfully synthesized, and consists of four-, six-and eight-membered rings in its structure. In this work, we perform density functional theory (DFT) calculations to study the methane oxidation reaction on a pristine biphenylene network nanosheet to understand its catalytic property. We found that the four-membered ring of the biphenyl network nanosheet possesses much stronger catalytic activity for O-2 decomposition and methane conversion to methanol than does the pristine graphene nanosheet. In addition, our results show that both methanol formation and formyl aldehyde formation mechanisms can occur on the biphenyl network nanosheet. Methanol formation is a kinetic reaction control process at 500 K, while the formyl aldehyde formation is the thermodynamic reaction control process at a higher temperature of 600 K. Thus, the operating temperatures will control the selectivity of methane oxidation reaction on the biphenyl network nanosheet. This finding shows that the pure carbon material biphenyl network nano sheet might be an excellent metal-free catalyst for methane oxidation reactions.
查看更多>>摘要：Plasma-assisted polishing (PAP) was confirmed to be high-efficiency and high-quality when applied to single crystal diamond (SCD) substrates. The effects of polishing pressure applied to the SCD substrate and sliding speed between the polishing plate and SCD substrate in PAP were systematically investigated in this study. Higher polishing pressures or sliding speeds resulted in a higher material removal rate (MRR) of SCD substrate, and the highest MRR achieved 5.3 mu m/h. In the case of PAP conducted at low polishing pressures such as 62.5, 81.3 kPa, scanning white light interferometer (SWLI) (84-mu m square) and atomic force microscope (AFM) (5-mu m square) measurements revealed an atomic-scale smooth surface without the surface texture depending on the crystal direction and the lowest Sq roughness of 0.3 nm (84-mu m square) was achieved. Correspondingly, at low polishing pressure of 62.5 kPa, MRRs in PAP along the <100> and <110> directions were nearly identical, suggesting that isotropic removals occurred. In the case of PAP performed at high polishing pressures such as 143.8, 246.9, and 350.0 kPa, SWLI and AFM measurements revealed a rough surface with bands of grooves along <100> direction. Correspondingly, at high polishing pressures of 246.9 and 350.0 kPa, MRRs in PAP along <100> direction were-11 and-12 times faster than that in <110> direction, respectively, suggesting that anisotropic removals occurred. Moreover, scanning transmission electron microscopy and angle-resolved X-ray photoelectron spectroscopy measurements confirmed that no damage or non-diamond layer was present on the PAP-processed SCD substrate. However, as the sliding speed varied, both SWLI and AFM measurements demonstrated that Sq roughness remained nearly constant with the same polishing pressure applied to the SCD substrate.
查看更多>>摘要：Carbon nanotubes (CNTs) have demonstrate potential applications in various molecules' encapsulation due to their nanoscale cylinder structures, used as desirable nanocarriers and nanocontainers for molecular systems. Here, we have studied the incorporation of 5-fluorouracil (5-FU) as an anticancer and provide molecular origin information to develop drug delivery at nanoscale. Quantum mechanics-based calculations showed that armchair CNT (7,7) with a diameter of 9 angstrom ca. was a favorable nanotube for 5-FU encapsulation. The calculated barrier energy developed based on the NEB technique showed that no barrier activation energy occurs during the incorporation of 5-FU into CNT (7,7). Structural geometries, electronic structure, charge analysis, and molecular properties of more stable complex have been analyzed. This structure of encapsulated drug remained inert, and the interaction nature was typical for the strong physisorption that demonstrating favorable factors for safe drug delivery. The presence of CNTs for the loading of 5-FU facilitates the increased reactivity of fluorouracil reac-tivity compared to the pristine one. The mechanical properties of the nanotube after drug encapsulation were calculated by Young's modulus and the results showed that the strength of CNTs decreased slightly after the incorporation of 5-FU into the nanotube.
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Elsevier