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[en] The polymer nanocomposite ZnS/Poly (methylmethacrylate) was prepared by the solution casting method and its structural and optical properties were investigated using XRD, SEM, TEM, HRTEM, and Raman spectroscopy. The basic material, ZnS, has the cubic structure and its crystallite size was estimated to be 2.3 nm, which implies that a strong confinement regime is in effect. Analysis of Raman spectra was performed using the fitting procedure based on effective medium theory. As a result, the surface optical phonon (SOP) mode was detected. It was found that the shape and position of the SOP mode depend on the type of the composite. © 2019 Elsevier B.V.
[en] Highlights: • Bonding the superalkali M3O to B40 nanocage can form the stable D-A framework. • Linking of superalkali M3O can effectively narrow the wide band gap of B40 nanocage. • All the composite M3O-B40 systems can exhibit the large first hyperpolarizability. • All of them can also present the considerably large second hyperpolarizability. Inspired by the fascinating finding of all-boron fullerene B40 (Nat Chem, 2014, 6, 727), we propose a new and effective strategy to construct a series of typical Donor-Acceptor (D-A) frameworks via linking the superalkali M3O (M = Li and K) unit with the low ionization potential to the B40 nanocage with large electron affinity. By means of the density functional theory computations, we have systematically investigated the structures, electronic properties, the first and second hyperpolarizabilities of these modified B40 nanocage systems. Owing to the formation of a B–O chemical bond, these composite systems (M3O)n-B40 (M = Li and K, n = 1 and 2) can possess the considerably large binding energy ranging from 57.0 to 99.8 kcal/mol, indicating their high structure stabilities. Compared with the pristine B40 nanocage, linking the superalkali M3O can effectively narrow the wide energy gap from the original 2.86 eV to 0.61–1.11 eV, and significantly increase the first and second hyperpolarizabilities to as large as 5.00 × 104–2.46 × 105 au and 1.48 × 107–4.85 × 108 au, respectively, owing to the occurrence of evident electron transfer process in this kind of typical D-A framework. These fascinating findings will be advantageous for promoting the potential applications of the inorganic boron-based nanosystems in the new type of electronic nanodevices and high-performance nonlinear optical materials.
[en] Highlights: • Incorporation of Al NPs enhanced UV–visible-NIR photovoltaic responses. • Effects of both absorption and scattering by SPs improved solar cell performance. • Chemical and field-effect passivations by SiO2 were utilized. We report to apply Al nanoparticles (NPs) to enhance the photovoltaic response of crystalline- or c-Si solar cell from the ultraviolet (UV) throughout the visible and near infrared (NIR) regimes. Al NPs were induced by solid thermal annealing and embedded in a SiO2 layer that was to passivate the front side of solar cell. Upon the excitation of surface plasmons (SPs) on the Al NPs under light illumination, an enhancement of broadband absorption of the solar cell was observed. The incorporation of Al NPs led to a relative 13.8% increase in photoelectric conversion efficiency of c-Si solar cell, and an external quantum efficiency enhancement from the UV throughout the visible and NIR regimes. The improvement of c-Si solar cell performance was attributed to both effects of absorption and scattering by SPs.
[en] Highlights: • Two different types of Co3O4 was synthesized by direct and indirect thermolysis of MOF-71. • Indirect thermolysis of MOF-71 represented higher specific capacitance of 320 F/g. • A high energy density of 13.51 Wh/kg along with a power density of 9775 W/kg were obtained. In this work, two different types of Co3O4 nano-crystals were synthesized by (i) conventional direct solid state thermolysis of cobalt terephthalate metal-organic framework (MOF-71) and (ii) new indirect solid state thermolysis of Co(OH)2 derived by alkaline aqueous treatment of MOF-71. The products were then characterized by X-ray diffraction technique (XRD), Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Reflection electron energy loss spectroscopy (REELS), Brunauer, Emmett, and Teller (BET), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. By REELS analysis the energy band gap of MOF-71 was determined to be 3.7 eV. Further, electrochemical performance of each Co3O4 nanostructure was studied by the cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode system in KOH electrolyte. An asymmetric supercapacitor was fabricated using indirect Co3O4 nanoparticles as cathode and electrochemically reduced graphene oxide as anode, and the electrochemical properties were studied and showed a high energy density of 13.51 Wh kg−1 along with a power density of 9775 W kg−1 and good cycling stability with capacitance retention rate of 85% after 2000 cycles.
[en] Highlights: • (4-APH)(4-APH2)[AsO4]·H2O was synthesized by slow solvent evaporation method. • X-ray crystallographic study has been carried out. • The compound crystallizes in triclinic system with space group P at 150 K. • Each organic chain is formed by monoprotonated cations [C5H7N2]+ and diprotonated cations [C5H8N2]2+ which is disordered. • Vibrational spectral analysis (IR and Raman) has been done. Single crystals of a new organic–inorganic hybrid compound, with the formula (4-APH)(4-APH2)[AsO4]·H2O, was synthesized at room temperature by slow evaporation method and characterized by X-ray diffraction at 150 K, DSC–TG measurements, FT-IR and Raman spectroscopies. The title salt, (C5H7N2)(C5H8N2)[AsO4]·H2O, contains mono and diprotonated 4-aminopyridine cations, an arsenate trianion and one water molecule. The diprotonated 4-ammoniumpyridinium dication [C5H8N2]2+ is disordered over two positions with refined site occupancies of 0.73 and 0.27 however the monoprotonated 4-aminopyridinium cation [C5H7N2]+ is ordered. The 4-aminopyridinium rings are essentially planar and occur in stacks along b axis. In the crystal, the AsIII atom is coordinated by four O atoms in a slightly distorted tetrahedral geometry. The arsenate O atoms link the 4-aminopyridinium cations and water molecules into a three-dimensional network via intermolecular O–H···O and N–H···O hydrogen bonds. Additionally, in this structure, the different types and the nature of aromatic–aromatic interactions can distinguish between a stacked arrangement are parallel displaced and T-shaped conformation. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. On the basis of detailed vibrational studies, the detailed assignment confirms the presence of the organic groups and the anionic entities. Besides, the thermal analysis studies have been performed, but no phase transition was found in the temperature range 298–625 K. Results from X-ray crystallography, Raman, IR spectroscopy and thermal analysis are combined to provide a description of the new organic arsenate monohydrate, (C5H7N2)(C5H8N2)[AsO4]·H2O.
[en] Highlights: • First report of simple and low cost SILAR synthesized Bi2S3 thin film as a pseudocapacitive electrode material. • Interconnected nanoparticles with porous morphology with uniform nanostructured possessed good crystallinity. • Bi2S3 thin film is a promising electrode material for supercapacitor with specific capacitance of 289 Fg−1. Bi2S3 thin film electrode has been synthesized by simple and low cost successive ionic layer adsorption and reaction (SILAR) method on stainless steel (SS) substrate at room temperature. The formation of interconnected nanoparticles with nanoporous surface morphology has been achieved and which is favourable to the supercapacitor applications. Electrochemical supercapacitive performance of Bi2S3 thin film electrode has been performed through cyclic voltammetry, charge-discharge and stability studies in aqueous Na2SO4 electrolyte. The Bi2S3 thin film electrode exhibits the specific capacitance of 289 Fg−1 at 5 mVs−1 scan rate in 1 M Na2SO4 electrolyte.
[en] Highlights: • A novel method is reported to improve the mobilities in 2D MoS2 transistors. • The synergy process with UV and ozone plasma treatment is developed for 2D nanoelectronics. • An energy band model based on Schottky barrier modulation is proposed to understand the underlying mechanism. Mobility engineering through physical or chemical process is a fruitful approach for the atomically-layered two-dimensional electronic applications. Unfortunately, the usual process with either illumination or oxygen treatment would greatly deteriorate the mobility in two-dimensional MoS2 field-effect transistor (FET). Here, in this work, we report that the mobility can be abnormally enhanced to an order of magnitude by the synergy of ultraviolet illumination (UV) and ozone plasma treatment in multilayer MoS2 FET. This abnormal mobility enhancement is attributed to the trap passivation due to the photo-generated excess carriers during UV/ozone plasma treatment. An energy band model based on Schottky barrier modulation is proposed to understand the underlying mechanism. Raman spectra results indicate that the oxygen ions are incorporated into the surface of MoS2 (some of them are in the form of ultra-thin Mo-oxide) and can further confirm this proposed mechanism. Our results can thus provide a simple approach for mobility engineering in MoS2-based FET and can be easily expanded to other 2D electronic devices, which represents a significant step toward applications of 2D layered materials in advanced cost-effective electronics.
[en] Highlights: • ZnO–Sb2S3 hybrid nanostructures were grown by chemical bath deposition method. • Dominant oxide phase of Sb was observed in ZnO–Sb2S3 nanostructures. • Zinc sulfide interlayer was introduced between ZnO–Sb2S3 nanostructures. • Considerable improvement in Sb2S3 structure is reported by interlayer introduction. Metal-oxide chalcogenide nanostructures as part of hybrid systems are very important for photovoltaic and optoelectronic applications. It is however known that the various interfaces within the hybrid structures play a crucial role in limiting the efficiency of these devices. Here we report on the improvement of Sb2S3 structure through modification of interface between Zn-oxide nanostructures and chalcogenides. ZnO nanorods were grown on fluorine doped tin oxide (FTO) substrate by chemical bath deposition (CBD) method. X-ray diffraction (XRD) and SEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the ZnO nanorod arrays. Antimony tri-sulfide (Sb2S3) was deposited on ZnO nanords by CBD and subsequently annealed at 300 °C in argon environment for 30 min. XRD and the XPS analysis of ZnO–Sb2S3 system showed the dominant presence of Sb2O3 rather than Sb2S3. Since oxidation of Sb2S3 is understood to proceed mainly from the ZnO–Sb2S3 interface, a ZnS interlayer was introduced between ZnO nanorods and Sb2S3 by chemical route. The subsequent structural and optical properties of the ZnO–ZnS–Sb2S3 system are analyzed in detail. The introduction of sulfide interlayer prevents the oxidation of Sb2S3 which is evident from reduced oxide phase in Sb2S3. Significant improvement in the structural and optical properties of Sb2S3 are reported as compared to the parent ZnO–Sb2S3 system. This gain in the optical properties of hybrid ZnO–ZnS–Sb2S3 nanostructures is explained as being related to successful prevention of Sb2O3 formation at the Sb–ZnO interface and stabilization of the desired Sb2S3.
[en] A systematic study has been done on the structural and electronic properties of carbon, boron nitride and aluminum nitride nanotubes with structure consisting of periodically distributed tetragonal (T ≡A2X2), hexagonal (H ≡A3X3) and dodecagonal (D ≡A6X6) (AX=C2, BN, AlN) cycles. The method has been performed using first-principles calculations based on density functional theory (DFT). The optimized lattice parameters, density of state (DOS) curves and band structure of THD-NTs are obtained for (3, 0) and (0, 2) types. Our calculation results indicate that carbon nanotubes of these types (THD-CNTs) behave as a metallic, but the boron nitride nanotubes (THD-BNNTs) (with a band gap of around 4 eV) as well as aluminum nitride nanotubes (THD-AlNNTs) (with a band gap of around 2.6 eV) behave as an semiconductor. The inequality in number of atoms in different directions is affected on structures and diameters of nanotubes and their walls curvature.
[en] Highlights: • TPyP-RGO hybrid has been fabricated via ionic self-assemble method. • TPyP covalent bonds present between the double surface of RGO sheets. • A reversible on/off photo-current density of 45.89 μA/cm2 has been recorded for prepared nanocomposite. • The modified g-C3N4 effectively enhanced photocatalytic ability of the composites. • An ultrasensitive electrochemical aptasensor was fabricated by the TPyP/RGO to detect thrombin. We have synthesized cationic mesa-tetra(4-pyridyl) porphine (TPyP)-reduced graphene oxide (RGO) hybrid structures through chemical reduction and subsequent ionic self-assembly. UV–vis spectroscopy, fluorescence emission spectroscopy and scanning and transmission electron microscopies are used to analyze the structures, which indicate that TPyP covalent bonds present between the double surface of RGO sheets. A reversible on/off photo-current density of 45.89 A/cm2 has been observed when the as-formed TPyP/RGO nanocomposite is placed in the environment of pulsed white-light illumination. In addition, an ultrasensitive electrochemical aptasensor could be fabricated by the as-prepared TPyP/RGO to detect thrombin. A linear response to thrombin has been observed with the as-formed electrochemical aptasensor in the concentration range of 1–1200 nM. Besides, the limitation of detection is determined to be 0.3 nM.