Abstract : Using RHEED and STM, we have studied surface reconstructions and formation of islands and interfaces for the 6.1 Angstrom family of compound semiconductors (InAs, GaSb, AlSb). The structure and stoichiometry of MBE-grown antimonide surfaces lead to growth and roughening mechanisms that are distinctly different from other III-V materials. When a new material is grown on an antimonide surface, some blurring of the resulting heterointerface must occur in the form of monolayer islands or atomic-scale intermixing.
Chitosan (CS) modified multi-walled carbon nanotubes (MWCNTs) were used as adsorbents (CS-MWCNTs) to adsorb Congo red (CR, anionic dye) from solution in batch mode.The structure and morphology of CS-MWCNTs were characterized by TEM, FTIR, Raman and XPS.The results from analysis of FTIR and XPS showed that CS was successfully loaded onto the MWCNTs.Raman analysis showed that the basic structure of MWCNTs after CS modification did not change.Adsorption studies were performed at different pH, coexisted ions concentrations, contact time and CR concentrations in the batch mode.Results showed that the pH of CR solution at 4.0 was best for the adsorption and the adsorption capacity could reach up to 623 mg•g -1 at 303K.The adsorption of the CR solution reached equilibrium within 8 h.Adsorption equilibrium data can be predicted by the Freundlich model while the kinetic adsorption data follow a pseudo-second-order model.Thermodynamic results showed that the adsorption process was spontaneous, and endothermic.The CR-loaded adsorbent can be regenerated using a 0.01 mol•L -1 NaOH solution, the regeneration rate can still reach 71% after three cycles.CS-MWCNTs may be available in removal of anionic dyes from solution.
We first reported the hetero-epitaxial growth with good lattice matching of cubic structure La2O3 dielectric ultra-thin films on InP substrates by PLD. Epitaxial relationship between the La2O3 film and InP substrate, namely [001]La2O3||[001]InP and [012]La2O3||[012]InP, and cross-section of the stack without interface layer have been revealed by RHEED and HRTEM. The band offset for La2O3/InP is evaluated to be 1.62 eV for valence band and 2.61 eV for conduction band by XPS. A leakage current of 2 × 10−4 A/cm2 at bias voltage of −1 V and small equivalent oxide thickness of 0.3 nm have been measured on the capacitors with W/La2O3/InP/Al stack.
A 4,5-quinolimide derivative, BNA, bearing the amide-DPA receptor, was synthesized as a turn-on fluorescent sensor for Cd2+. Under physiological conditions, BNA could distinguish Cd2+ from Zn2+, showing turn-on fluorescence behaviour and an increased fluorescence lifetime. BNA and Cd2+ formed a 1 : 1 stoichiometric complex, and the detection limit was measured to be as low as 11 nM. Furthermore, BNA was utilized for fluorescence imaging of Cd2+ in live cells. To the best of our knowledge, it is the first 4,5-quinolimide-based sensor for the detection of metal ions.
Electrochemical N₂ reduction (ENR) offers a promising route for NH₃ production. To promote this kinetically sluggish process, the design and development of electrocatalysts with high performance, good durability, low cost, and earth abundance are highly demanded. Here, we report a facile approach for the synthesis of metal-doped ultrafine W₁₈O₄₉ nanowires with significantly enhanced capability for electrocatalytic N₂ reduction to produce NH₃ within a wide pH range. In particular, the Mo-doped W₁₈O₄₉ catalyst can reduce N₂ to NH₃ with a faradaic efficiency approaching 12.1% at −0.2 V (versus the reversible hydrogen electrode, vs. RHE) and an NH₃ yield rate of 5.3 μgNH₃ h–¹ mgcₐₜ.–¹ at −0.5 V (vs. RHE) in 0.1 M Na₂SO₄, which is about two times higher than that of pristine W₁₈O₄₉. We find occurrence of strong electron transfer from Mo to W, which facilitates N₂ adsorption and activation, thus accelerating the ENR to generate NH₃. This work provides a simple and effective method to modify metal oxides for efficient electrochemical N₂ fixation.
In situ temperature monitoring has become extremely imperative in high-temperature harsh environments and polymer-derived ceramics (PDCs) as sensing materials have attracted great attention. However, the stability and oxidation/corrosion resistance of PDCs cannot be simultaneously achieved at the moment, limiting their practical application. Herein, polymer-derived SiAlBCN ceramics were synthesized via polymer conversion method under different pyrolysis temperatures. Their microstructure evolution, high temperature sensing properties and stability were investigated in detail. The results show that the amorphous SiAlBCN phase grows more ordered and the size of the free carbon phase enlarges with the increasing temperature. The defects concentration displays a decreasing tendency. Concurrently, the SiAlBCN ceramics as sensing materials exhibit a good temperature-resistance property from room temperature to 1100 °C. The fabricated SiAlBCN temperature sensor possesses excellent stability, repeatability and accuracy. Moreover, SiAlBCN ceramics exhibit distinguished oxidation/corrosion resistance after 100 h treatment at 1200 °C in a water/oxygen environment, which is attributed to their low corrosive rate constant (0.57 mg·(cm2·h)-1) and oxidative rate constant (3.43 mg2·(cm4·h)-1). Therefore, polymer-derived SiAlBCN ceramics as sensing materials, which possess outstanding stability and oxidation/corrosion resistance, have great potential for in-situ monitoring of extreme environmental temperatures in the future.
The traditional silicon-based pressure sensors cannot meet the demand of pressure information acquisition in high-temperature extreme environments for future nuclear power, aerospace and automobile industries due to their low sensitivity, limited detection temperature and complex processing. Herein, a capacitive pressure sensor is fabricated using polymer-derived SiCN ceramics with microstructures to improve the sensitivity. Based on the near formability of the liquid polymer precursor, several SiCN ceramics with convex microarrays are prepared successfully via a sample replication strategy. A capacitive pressure sensor is subsequently fabricated and its performance is measured at different pressure (0~800 kPa) from room temperature to 500 ℃. The results show that the SiCN ceramic capacitive pressure sensor exhibits low hysteresis, good non-linearity of 0.26%, outstanding repeatability and high sensitivity of 0.197 pF/MPa under room temperature. When the test temperature reaches 500 ℃, the performance of the prepared capacitive pressure sensor has no degradation, keeping competent sensitivity of 0.214 pF/MPa and nonlinear error of 0.24%. Benefitting from the preeminent high-temperature properties, e.g., excellent oxidation/corrosion resistance and thermal stability, SiCN ceramics capacitive pressure sensors have great potential in the application of high-temperature and harsh environments.
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