Nano

It is of great significance to prepare electrochemical glucose sensors with high selectivity and stability via effective and rapid methods. In this work, the self-support electrode with copper and nickel-based oxide is prepared by chemical-etching reaction which occurred under the property of electrochemical potential difference. In this processing, nickel foam is etched selectively by Cu${}^{2+}$ ions and they not only act as self-supporting electrode substrate, but also as nickel ions precursor of NiO. Moreover, the reaction can be completely satisfied on 30 min at room temperature. As a self-supporting electrode nonenzymic glucose electrochemical sensor, the electrode exhibited a wide linear range (0.04–3.00mM), low detection limit (0.02mM) with high sensitivity of 1096$\mu A\cdot {\mathrm{\text{mM}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ and good selectivity, repeatability and stability. Furthermore, the application of the prepared sensor provides an avenue for the application of the transition metal materials in the field of electrochemical sensing.

Flower-shaped nanometer zinc oxide and its complex incorporating La–Nd have been prepared using hydrothermal method with zinc chloride and urea as raw materials, ethylene glycol as morphology controller. The powdered samples were characterized by scanning electron microscopy, X-ray diffractometry, photocatalytic test with solutions of reactive dyes as indicators. In conclusion, the optimum doping ratios of La/Nd are considered to be 3%/3%. When 3%La–3%Nd/ZnO was served as photocatalyst, considerable degradations of dyes were caused under the ultraviolet and visible light without exception, owing to the expanded excitation wavelength and reduced band gap of ZnO after incorporating. While using the compound material in effluent treatment containing reactive dyes, the decomposition rate of dyes, respectively, reached 99.99% and 80% or more under UV-light and visible irradiation for 60 min, appreciable removal effects of organic pollutants were obtained, testifying 3%La–3%Nd/ZnO to be a splendid UV-Vis catalyst.

As heavy-metal-free alternatives to Cd- and Pb-containing semiconductor nanocrystals (NCs), ternary I–III–VI₂ compounds NCs have been actively studied, especially the CuInS₂ NCs. Recently, it has been found that thick ZnS shelling can greatly improve the photochemical stability of such NCs, which undoubtedly enhances their application potential although it is still limited by the development of synthetic methods. This paper provides a facile method for preparation of thick-shell CuInS₂/ZnS NCs. The effects of reaction temperatures ($220^{\circ }$C and $300^{\circ }$C) and sulfur precursors (dodecanethiol and sulfur powder) on the shell overgrowth are discussed in detail. When low reaction temperature ($220^{\circ }$C) and inactive sulfur precursor are used, the overgrowth of ZnS shell is considerably slow and raising temperature have a limited impact on the particles’ size. On the contrary, high reaction temperature and reactive sulfur precursor can effectively improve the overgrowth rate of ZnS shell, and then thick-shell CuInS₂/ZnS NCs can be received. Furthermore, a high-speed centrifugation method is used to screen out product NCs with a relatively uniform size.

The growth of pathogenic bacteria seriously threatens human health. Effective inhibition of pathogenic bacteria in the human body and the surrounding environment is of great urgency. In this work, we propose a strategy in preparing bacteriophage-like gold nanoparticles (B-AuNPs) for antibacterial applications. B-AuNPs were prepared by multiple in-situ reducing reactions on the surface of AuNPs. It was shown that the secondary-reduced AuNPs (B₁-AuNPs) have a bacteriophage shaped morphology. Under near infrared laser, B₁-AuNPs could almost completely inhibit bacterial growth at low concentrations within 5 min, due to the combined effects of increased temperature and reactive oxygen species (ROS). Moreover, B-AuNPs can be easily separated from the dead bacteria and the recycled B-AuNPs remain the high antibacterial efficiency. It is concluded that B-AuNPs have great potentials in the antibacterial researches for biocontrol, biomedicine and environmental engineering.

Ultrathin two-dimensional transition metal dichalcogenides represent a promising new class of materials with surface-enhanced Raman scattering (SERS) activities. Previous work mainly focused on the SERS effects of transition metal dichalcogenide crystals with sizes of micrometer scale. The enhancement effect is usually nonuniform on the SERS substrates. In this paper, we report a chemical vapor deposition method for the preparation of centimeter-scale MoSe₂ films with uniform and high SERS activity. The molybdenum precursors are supplied in a “face-to-face” manner from a silica gel plate to the growth substrate, which guarantees uniform nucleation and growth of the monolayer MoSe₂. We demonstrate that the monolayer MoSe₂ film has strong SERS effect, which can be attributed to charge transfer between MoSe₂ and the probe molecules. The detection limit of Rhodamine B on monolayer MoSe₂ is determined to be 10${}^{-7}$mol/L, and the Raman enhancement factor is estimated to be $5.58\times 10^4$. Due to its atomic uniformity and chemical stability, the MoSe₂ film can serve as an ideal two-dimensional SERS material for detection of various molecules.

Graphene is one of the most attractive two-dimensional materials that can be used for efficient desalination due to its ideal physical properties and high performance in ion selectivity and salt rejection. Here, in this paper, molecular dynamics simulations were applied to investigate the possibility of using a parallel nanopore system to pump ions so that the ions of both cation and anion species in the middle compartment could be evacuated at an extremely rapid rate. By building hexagonal parallel single-layer graphene films with spacing of 3.0 nm and changing the pore numbers and surface charge densities of the nanopores, the efficiency of desalination could be well controlled. It is found that the ion concentration decreases exponentially with time. The more the number of nanopore is, the stronger the surface charge density of nanopore is, the evacuation of ions in the middle compartment is more obvious, offering a new means for controlling the desalination efficiency. The simulations performed here provide theoretical insights for designing and fabricating high efficient and less energy consumption graphene desalination devices in the future.

Layered g-C₃N₄ was obtained through secondary calcination, and the MoS₂–Ag/g-C₃N₄ catalyst was prepared via hydrothermal and light deposition methods. XRD, SEM and TEM results proved that the MoS₂–Ag/g-C₃N₄ sandwich biscuit structure was successfully obtained, and the sharper diffraction peak of MoS₂–Ag/g-C₃N₄ than g-C₃N₄ or MoS₂ is attributed to the synergistic crystallinity effect. SPR effect of Ag increases the electron transport time, which effectively prolonging the survival time of electron–hole pairs. Compared the degradation performance of 10mg/L rhodamine B (RhB) with different ratios of materials, 10wt.% MoS₂–Ag/g-C₃N₄ has the highest degradation property. The degradation rate remains at 87.2% under the best condition after four cycles proved that the MoS₂–Ag/g-C₃N₄ composite possesses good stability.

Green and efficient mass production of graphene sheets with high quality and electrical conductivity is intriguing for both academic scientists and industry. Among numerous production methods suffering from complexity or harsh chemical media, direct and high-yield exfoliation of graphite in water seems to be the best choice. In this study, efforts were made to prepare high-quality and stable graphene dispersions with the highest possible concentrations through an ultrasound-assisted liquid-phase exfoliation (LPE) in water directly from two types of natural graphites. The rigorous structural, morphological and electrical analyses were conducted on both graphite and graphene samples to quantitatively identify the effect of graphite sources on the LPE yield and the quality of the graphene nanosheets produced in the presence of an ionic surfactant. The results obtained by TEM, AFM, XRD and Raman spectroscopy indicated the successful and efficient production of single and few layer graphene sheets with the remarkable concentration of 3.18mg.ml${}^{-1}$ in water. Moreover, the results signified that the structural quality, electrical conductivity and production yield of the graphene layers undoubtedly depend on the structural properties of graphite source. In fact, the graphite source greatly influences the final properties and potential applications of the produced graphene layer and the results are so important for the future graphene industry.

Graphene or its derivates are used as an electrode material for the fabrication of supercapacitors (SCs). However, graphene or its composites readily agglomerate or stack in water, which seriously imparts SC energy efficiency. Presently, we used a new composite using $\alpha$-MnO₂ nanowires and nitrogen-doped reduced graphene oxide ($\alpha$-MnO₂/NRGO) for the fabrication of electrodes required in symmetric SCs. Hydrothermally synthesized $\alpha$-MnO₂ nanowires have a smooth surface, good dispersion, and a high length-to-width ratio. The formation of stable and densely networked structures and the synergy between NRGO and $\alpha$-MnO₂ nanowires enable the $\alpha$-MnO₂/NRGO film electrode to show a large area-specific capacitance (386.8mFcm${}^{-2}$) at 1mA$\cdot$cm${}^{-2}$ current density; the capacity retention is 62.4% when the current density increases from 1mA$\cdot$cm${}^{-2}$ to 10mA$\cdot$cm${}^{-2}$. The flexible and symmetrical $\alpha$-MnO₂/NRGO SC was assembled using $\alpha$-MnO₂/NRGO film electrodes in 1 M Na₂SO₄ electrolyte with a cellulose paper separator, has good capacitance retention (94%), excellent Coulombic efficiency (99%) after 3000 cycles, and high energy density (28.22$\mu$Wh$\cdot$cm${}^{-2}$) at 0.8mW$\cdot$cm${}^{-2}$ power density. The $\alpha$-MnO₂ nanowires/NRGO hybrid film flexible and symmetrical SCs are characterized by high energy storage, good cycle life and Columbic efficiency, which offer promising applications in the portable and wearable electronics industry.

MXenes have excellent electrochemical performance due to their remarkable electrical conductivity and abundant surface functional groups. However, the smaller interlayer spacing and self-stacking limit their practical applications. Herein, the Ba${}^{2+}$ ions pillared Ti₃C₂ MXene (Ba${}^{2+}$–Ti₃C${}_2)$ with enlarged interlayer spacing has been successfully fabricated by electrostatic self-assembly. The pillared Ba${}^{2+}$ ions between Ti₃C₂ layers can enlarge interlayer spacing, increase specific surface area, expose more active sites and provide open ions transfer channels due to its pillaring effects on the layered structure of Ti₃C₂. The Ba${}^{2+}$–Ti₃C₂ exhibits a higher specific capacitance (168F$\cdot {\mathrm{\text{g}}}^{-1}$ at 0.2A$\cdot {\mathrm{\text{g}}}^{-1})$ than pure Ti₃C₂ (123 F$\cdot {\mathrm{\text{g}}}^{-1}$ at 0.2A$\cdot$g${}^{-1})$ and outstanding cycle performance, which remains at 164 F$\cdot {\mathrm{\text{g}}}^{-1}$ after 1100 cycles at 1A$\cdot {\mathrm{\text{g}}}^{-1}$. The Ba${}^{2+}$–Ti₃C₂//AC asymmetric supercapacitor achieved a high power density of 1140W$\cdot$Kg${}^{-1}$ as well as long cycle stability with capacitance retention of 86.35% at a current density of 1A$\cdot$g${}^{-1}$ after 4000 cycles. The results demonstrate that expeading interlayer spacing can obviously enhance and optimize the supercapactive performance of MXenes, providing an idea to design the 2D energy storage materials with large interlayer spacing and high rate capability.

Mechanical alloying is used to prepare the Co${}_{0.9}$Cu${}_{0.1}$Si alloy. Mesoporous silicon SBA-15 is employed as the template to synthesize mesoporous carbon CMK-3. For the purpose of improving the electrochemical properties of Co${}_{0.9}$Cu${}_{0.1}$Si alloy, Co${}_{0.9}$Cu${}_{0.1}\mathrm{\text{Si}}+x$ CMK-3 ($x=3\%$, 6%, 9% and 12% mass fraction) alloys are fabricated via ball-milling. As the negative electrodes of Ni–MH batteries, the discharge capacities of alloys are tested by the LAND CT2001A tester and three-electrode system. Finally, the composite alloys show different properties for hydrogen storage. A maximum discharge capacity (558.7mAh/g) is achieved for Co${}_{0.9}$Cu${}_{0.1}\mathrm{\text{Si}}+6\%$ CMK-3 electrode. Superfluous CMK-3 is not beneficial to enhance the discharge capacity of Co${}_{0.9}$Cu${}_{0.1}$Si alloy. Moreover, Co${}_{0.9}$Cu${}_{0.1}\mathrm{\text{Si}}+x$ CMK-3 electrodes exhibit better corrosion and oxidation resistance, which leads to higher capacity retention for CMK-3/Co${}_{0.9}$Cu${}_{0.1}$Si composites. The comparative studies on HRD and kinetic properties of Co${}_{0.9}$Cu${}_{0.1}$Si and Co${}_{0.9}$Cu${}_{0.1}\mathrm{\text{Si}}+6\%$ CMK-3 are also conducted. The $R_{\mathrm{\text{ct}}}$ of Co${}_{0.9}$Cu${}_{0.1}$Si alloy reduces and $I_0$ increases after doping of CMK-3. The special structural characteristics and higher conductivity of CMK-3 can offer more electrochemical active sites and accelerate hydrogen diffusion. Accordingly, the electrochemical activity and kinetic properties are enhanced for CMK-3/Co${}_{0.9}$Cu${}_{0.1}$Si composites.

A mixed potential-type NO₂ sensor was fabricated using yttria-stabilized zirconia (YSZ) as the electrolyte and mesoporous WO₃ as the sensing electrode for the detection of NO₂ in vehicle exhausts. The mesoporous WO₃ with a diameter of 7 nm was synthesized using the hard template method. The sensor showed excellent performance in the detection of 30–500ppm of NO₂ at 300^∘C and 500^∘C. However, commercial WO₃ only operate well at 500^∘C. The response of the mesoporous WO₃ was higher and the test temperature was lower compared to that of commercial WO₃. XPS combined with NO₂-TPD was used to explain the high activity of mesoporous WO₃ at medium-low temperature, and the mechanism of mixed electromotive force was verified by electrochemical impedance spectroscopy. Furthermore, the sensor exhibited high NO₂ selectivity in the presence of interfering gases, such as NO, CO, CO₂ and NH₃. Most importantly, the sensor had excellent repeatability and stability.

AlGaN offers new opportunities for the development of the solid-state ultraviolet (UV) luminescence, detectors and high-power electronic devices, however, problems such as low growth rate and poor crystallization quality are common in the growing process of AlGaN material. In this paper, a new reaction cavity for high-temperature MOCVD AlGaN growth was carried out through the research of resistance heated, and the thermal field of high-temperature MOCVD growth was numerically simulated. Based on the high-temperature MOCVD reaction cavity, an orthogonal experimental method was used to simulate the process parameters, and the range, variance and matrix analysis were conducted on the calculation results. The finite element analysis was conducted on the temperature field, pressure field, velocity field, and the high-temperature MOCVD AlGaN growth model was established.

Bi₂S₃/MoS₂/g-C₃N₄ nanocomposite was synthesized using a solid-state method for the first time. Thiourea and bulk Bi₂MoO₆ were used as the precursors and were reacted under a nitrogen atmosphere. Bi₂S₃/MoS₂/g-C₃N₄ was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microcopy, X-ray photoelectron spectra and ultraviolet–visible diffuse reflectance spectroscopy. The structure of Bi₂S₃/MoS₂/g-C₃N₄ is a three-dimensional network structure formed by uniform loading of g-C₃N₄ and MoS₂ around the rod-like Bi₂S₃ framework. The photodegradation performance was evaluated by the degradation of rhodamine B during irradiation by a 350 W Xe lamp. The degradation rate of Bi₂S₃/MoS₂/g-C₃N₄ towards rhodamine B reached 95.1% after irradiation for 150min. This study will provide new insights into the design of efficient and stable heterostructures for photocatalytic applications.