查看更多>>摘要：? 2022Hydrogenated diamond (C[sbnd]H diamond) inverters have been fabricated by normally-off Al/BaF2/C-H diamond metal-insulator-semiconductor field effect transistors (MISFETs) and load resistors. Electron beam evaporation was used to deposit BaF2 film on the diamond surface at room temperature to reduce thermal degradation effect on the C[sbnd]H bond and adsorbates during the deposition. The resulting 4-μm normally-off MISFET achieves the maximum saturation drain current, on-resistance, maximum transconductance and switching ratio of ?113.4 mA/mm, 37.1 Ω·mm, 35.4 mS/mm and 108, respectively. Effective hole mobility of more than 200 cm2/V·s is achieved in a large gate voltage range (?0.35 V ≤ VGS -VTH ≤ ?4.35 V). Correspondingly, based on the high-performance diamond MISFET, the diamond inverters exhibit good voltage transfer characteristics and dynamic switching characteristics at the frequency of 50 kHz.
查看更多>>摘要：? 2022The magnetic dual Z-scheme composite photocatalyst g-C3N4/BiVO4/CoFe2O4 was successfully fabricated via a high-temperature solid-state route. The photocatalytic activity of the as-prepared composites was evaluated by detecting the variation in rhodamine B (RhB) concentration under visible light irradiation. The results show that the composite exhibits much higher photocatalytic activity than bare g-C3N4, bare BiVO4 or the binary composite of g-C3N4/BiVO4, and that the degradation efficiency of RhB can reach 94.5% within 100 min. The trapping experiments indicate that all three radicals ·OH, ·O2? and h+ contribute to the photocatalytic degradation of RhB, and that ·OH radicals play the most important role, followed by superoxide anion ·O2? radicals and finally by holes h+. The hole scavenger EDTA shows a positive influence on the photocatalytic degradation of RhB; it only takes 30 min to degrade 99.6% of RhB, which is nearly 3.5 times faster than that without EDTA. Moreover, the cycle tests prove that the as-prepared composite photocatalyst has good stability and reusability; after 10 consecutive cycles, no obvious deactivation was observed. It also shows excellent performance in water splitting for hydrogen evolution with overpotential values of ?155 mV at a current density of 10 mA cm?2.
查看更多>>摘要：? 2022 Elsevier B.V.J-aggregates nanostructure proposed for realization of plasmonic manufactories like switchable localized surface resonances (LSR) due to their optical nonlinearities' properties. J-aggregates to enhancement of light-matter interaction is applied. In this regard, we propose a novel graphene/J-aggregate plasmonics coupler with subwavelength structure at telecommunication range. Utilizing device geometries and optical properties optimized for enhanced light-matter interactions lets us to harness the propagation of TM (TE) modes without the change of configuration. Here, the coupling parameters have been numerically and investigated using the finite-difference time-domain (FDTD) method. The results show that the coupling condition can be tuned by optical properties of graphene in turn leads to a tunable plasmonics coupler. It is shown that, by considering magnetic field of 0.01 T and graphene chemical potential of mc = 0.45 eV, the TM mode, and magnetic field of 0.02 T and graphene chemical potential of mc = 0.4 eV, the TE mode can be propagated in the selected ports. With the above behavior, the proposed structure may potentially be applied in telecommunication links.
查看更多>>摘要：? 2022 Elsevier B.V.Although there are several reports about the beneficial performance of metal doped graphitic carbon nitrides (g-C3N4) in various photocatalytic reactions, the effect of different alkali metal dopants has not been studied systematically. Series of undoped, Li-, Na- and K-doped samples was synthetized and used for the preparation of novel type of photocatalysts, composed of palladium nanoparticles supported on alkali metals-doped graphitic carbon nitride. Palladium loading was achieved via citrate reduction of palladium precursor in the presence of the carbon nitride material. Several physicochemical characterization methods such as attenuated total reflection infrared-(ATR-IR), diffuse reflectance UV–visible spectroscopy, high-resolution transmission microscopy (HRTEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and thermogravimetric analysis (TGA) were used to get information about the morphology and composition of the novel composites. According to the optical characterization results, the band gap of g-C3N4 decreased upon Na- and K doping but increased after Li-doping. The palladium nanoparticles were distributed over the support and appeared in dispersed (undoped g-C3N4, Li-g-C3N4) or agglomerated (Na-g-C3N4, K-g-C3N4) form with individual particle size below 5 nm. The catalytic performance of these composite materials was tested in two processes: (i) photodegradation of methyl orange and (ii) hydrogen production from methanol. The Na- doping of graphitic carbon nitride was found to be a key issue to enhance hydrogen production. The carbon nitride matrix was found to be stable during the photocatalytic experiments, while the Pd component underwent certain changes during the photocatalytic reforming reaction of methanol. Our results indicated that the really acting metallic Pd cocatalyst was formed mainly in situ.
查看更多>>摘要：? 2022 The AuthorsSingle-crystal diamond needles in the form of micrometer-scale sharp pyramids were produced using a combination of chemical vapor deposition and thermal oxidation processes. These diamond needles with atomic-sized fluorescent defects (color centers) attract great interest for practical applications as a platform for creation of optical quantum sensing probes and optical quantum communication elements. Particular color centers localization providing suitable luminescence characteristics is required for these applications. Here we report about formation of nitrogen-vacancy (NV), silicon-vacancy (SiV) and germanium-vacancy (GeV) centers in the single-crystal diamond needles during direct current discharge plasma enhanced chemical vapor deposition (PE CVD). Luminescent characteristics of the needles were observed by confocal photoluminescence mapping. Analysis of experimental results allows us proposing possible mechanisms of impurities introduction into the crystal lattice during needles growth. These mechanisms include gas decomposition and etching of substrate material during CVD. The proposed mechanisms were approved by realization of CVD process protocols resulting in controllable formation of NV, SiV and GeV centers in single-crystal diamond needles including formation of thin NV- and SiV- enriched layers by tuning deposition process parameters. The proposed experimental approaches in combination with revealed mechanisms for introduction of favorable impurities make single-crystal diamond needles promising candidates for scanning quantum sensing, quantum communication and hyperpolarization experiments.
查看更多>>摘要：? 2022Self-consistent charge density functional tight-binding simulations are performed to investigate the adjustments of adsorption behaviors of C60 onto perfect or defective graphene owing to the applied electrical field. For the C60 adsorbed on the perfect graphene, the effect of the applied electrical field on the physical adsorption is visually displayed from the Mulliken charges on the atoms of the C60-graphene nanohybrid systems. When the C60 is adsorbed on the graphene with one vacancy, the differential charge density and optimized geometry as well as the adsorption energy are used to identify chemical, physical, or no adsorption. The applied electric field can adjust adsorption behaviors for some configurations accompanying with the atom arrangements in the graphene.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, a novel hierarchical web-like microstructure was fabricated by aligning interconnected NiFeMn hydroxide garlands on rGO-modified Ni foam (NiFeMn hydroxide/rGO/Ni foam) with a one-pot two-step hydrothermal method. During the first step at 50 °C, the redox reaction between GO and Ni foam results in the formation of rGO membrane on Ni foam. During the second step at 135 °C, urea decomposed and the produced NH3·H2O reacted with metal cations to form amorphous NiFeMn ternary hydroxide. The obtained binder-free electrode was characterized with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Brunauer-Emmett-Teller gas sorptometry measurements (BET). The electrochemical performances of NiFeMn hydroxide/rGO/Ni foam were investigated with cyclic voltammetry (CV) and galvanostastic charge/discharge technique (GCD). NiFeMn hydroxide/rGO/Ni foam presents a high areal capacity of 35.1 C cm?2, capacity retention of 81.1% after 5000 GCD cycles at 30 mA cm?2 and excellent rate capability. The asymmetric supercapacitor (ASC) assembled with NiFeMn hydroxide/rGO/Ni foam and activated carbon (AC) presents a ultra-high energy density of 40.73 W h m?2 at the power density of 79.38 W m?2, suggesting its good application prospect in energy storage.
查看更多>>摘要：? 2022 Elsevier B.V.Hydroxyl chloride has attracted extensive attention in recent years due to its outstanding performance relative to other similar anode materials. In this paper, Co2(OH)3Cl was introduced into graphene aerogels by a one hot-pot method to fabricate a Co2(OH)3Cl/graphene aerogels composite (Co2(OH)3Cl/GA) with a 3D loose-porous structure. The Co2(OH)3Cl particles are evenly dispersed and independently wrapped within the 3D graphene network, preventing particle agglomeration and alleviating the volume effect while also providing a more convenient multi-dimensional channel for electron transmission. Hence, Co2(OH)3Cl/GA electrode delivered a superior cycling capacity of 615 mAh g?1 at 1.6 A g?1 after 150 cycles. Furthermore, due to the high conductivity and superior mechanical flexibility of the 3D porous matrix, Co2(OH)3Cl/GA composite could also achieve good performance even as a free-standing electrode without additives and metal foil. More importantly, the lithium storage mechanism of Co2(OH)3Cl/GA free-standing electrode during charge-discharging progress could be detected more clearly by ex situ XRD and XANES because the interferences of metal foil and additives were avoided. The mechanism research results reveal that the reversible lithiation/de-lithiation progress of Co2(OH)3Cl/GA is mainly attributed to the reversible reaction of Co(OH)2 + 2Li+ + 2e? ? Co0 + 2LiOH. The collected evidence also suggests that the chlorine element may participate in the formation of solid-electrolyte-interface (SEI) film, which is conducive to enhancing the electrode stability.
查看更多>>摘要：? 2022 Elsevier B.V.In recent decades, heterostructured photocatalysts have gained the great interest for their ability to possess higher photocatalytic activity. In this investigation, we synthesized g-C3N4 decorated α-Fe2O3 nanostructure by hydrothermal method to develop heterostructure. XRD, SEM, TEM, UV-DRS characterizations on the prepared sample revealed that g-C3N4 nanoparticles with 5–10 nm were decorated on the surface of the α-Fe2O3 spherical nanoparticles having the dimension of 50–100 nm. The designed g-C3N4@α-Fe3O4 heterostructure exhibit better photodegradation towards methyl orange under visible light exposure than pristine α-Fe2O3 with pseudo-first-order kinetics. The pseudo-first-order kinetic rate constant (k) for α-Fe2O3, and g-C3N4@α-Fe2O3, was determined to be 0.0171 min?1 and 0.02899 min?1, respectively. The g-C3N4@α-Fe2O3 exhibited greater photocurrent density than that of the α-Fe2O3 sample under simulated solar irradiance. In comparison with pristine α-Fe2O3 (83%), S-scheme g-C3N4@α-Fe2O3 heterostructure exhibited higher photodegradation efficiency (94%) since it had narrow bandgap energy, enhanced charged transportation, and reduced charges recombination owing to engineered heterostructure. The mechanism for the improved photodegradation efficiency of g-C3N4@α-Fe2O3 was discussed and found that O2[rad]– radicals participate a major function in the photodegradation of methyl orange dye, followed by [rad]OH? radicals. The designed g-C3N4 decorated α-Fe2O3 heterostructure may be a possible material for the treatment of textile effluents.
查看更多>>摘要：? 2022Perovskite NaTaO3 nanocrystals were synthesized using hydrothermal route, and were employed as substrate to deposit several high rGO mass ratios (NaTaO3/rGOx, x = 0, 10, 15 and 20%). X-Ray Diffraction (XRD) proved that NaTaO3 has an orthorhombic perovskite crystalline structure; this phase was conserved after the deposit of rGO, noting a varying of the orientation at the interface. The composites were analyzed by Infrared-spectroscopy (IR), which the absorbed frequencies were all ascribed to different vibrational modes inside the NaTaO3 and rGO structures. Scanning Electron Microscope (SEM) images illustrate the formation of the heterojunction and the mixing of NaTaO3 and rGO sheets with grain seize around 300 nm, and RAMAN-spectroscopy illustrates the obtaining of weak stacked graphene and disordered nano-graphene sheets. In addition, Photoluminescence (PL) reveals large Stocks shift about 60 nm, both XRD and PL reveal that the electronic and structural properties are affected by the deposited rGO. The composites were evaluated for their enhanced adsorptive performance, about 12 mg/g was measured for NaTaO3/rGO20%; and various kinetic models were employed for the adsorption, proving that the adsorption mechanism is governed by film-diffusion and/or chemical reactions process. Finally, the combined process adsorption-photocatalysis for NaTaO3/rGOx illustrate a total elimination of pollutant compared to pristine NaTaO3.
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