Effective Dispersion of CuPd Alloy Nanoparticles Using the Taylor Vortex Flow for the Preparation of Catalysts with Relatively Clean Surfaces

Dispersion is a crucial issue in nanoparticle preparation, e.g., a nanocatalyst of a high surface–volume ratio. Unfortunately, most synthetic approaches strongly depend on an excessive amount of stabilizers and inactive supporting materials for nanoparticle dispersion, resulting in a serious loss of the active surface. In this research, an approach employing a Taylor vortex flow (TVF) is first reported to obtain the effective dispersion of nanoparticles in the synthesis. Completely dispersed nanoparticles of the CuPd alloy less than 5 nm were easily synthesized in a continuous Couette–Taylor (CT) reactor due to the strong and periodic shear field of TVF. Thus, 3.2 nm sized nanoparticles were synthesized at a rotation speed of 1200 rpm and a mean residence time of 2 min despite the use of at least 6–14 times less stabilizer compared with conventional synthetic approaches. However, large aggregates of nanoparticles are always produced in a conventional continuous stirring tank reactor (CSTR) even with a high concentration of stabilizer and a high agitation speed of 3000 rpm. Furthermore, we systematically examined the effect of various synthetic parameters such as rotating speeds, mean residence times, and concentrations of reagents and stabilizers on the dispersion and size of CuPd alloy nanoparticles. Moreover, the well-dispersed CuPd alloy nanoparticles prepared in the CT reactor exhibited enhanced electrocatalytic activity for formic acid oxidation (FAO) compared with CuPd aggregates prepared in CSTR

Stabilizer-Free PdCu Nanoparticles Dispersed on Carbon Using Taylor Vortex Flow as Catalysts for Electrochemical Oxidation of Formic Acid

Stabilizers play a critical role in synthesizing small and well-dispersed nanoparticles with large catalytic surface areas. Simultaneously, they strongly bind to the surface of the nanoparticles and interfere with the catalytic reaction. In this study, we report that the effects of stabilizers can be replaced by the periodic and uniform fluid shear of Taylor vortex flow (TVF). Small PdCu alloy nanoparticles well-dispersed on carbon were synthesized in the Couette–Taylor reactor using TVF without the stabilizer. TVF could provide effective micromixing for a fast reaction and uniform fluid shear to prevent aggregation in nanoparticle synthesis, thus forming small and well-dispersed nanoparticles. In contrast, turbulent eddy flow generated by impeller agitation in a mixing tank reactor could only synthesize aggregates of nanoparticles seriously, indicating the importance of the periodic uniform flow. The synthesized stabilizer-free PdCu nanoparticles (Pd41Cu59/C) showed 1.4 times and 3 times higher mass activity than PdCu/C covered with a stabilizer (polyvinylpyrrolidone) and commercial Pd/C toward electrochemical formic acid oxidation, respectively

Functionalized Amphiphilic Diblock Fullerene Derivatives as a Cathode Buffer Layer for Efficient Inverted Organic Solar Cells

The amphipathic interface layer sandwiched between cathode and active layers had always played a role to balance interface compatibility and interfacial energy barriers in inverted organic solar cell (OSC) devices. Two functionalized amphiphilic diblock fullerene derivatives named C60-2DPE and C60-4HTPB were synthesized and applied as an interface layer in modifying zinc oxide (ZnO). Based on their amphipathic characteristics, the solvent treatment was introduced to cause an obvious self-assembly of the two materials on ZnO. The introduced cathode buffer layer could improve the interface compatibility between ZnO and the organic active layer effectively with its amphipathic blocks. Based on the PTB7-Th:PC71BM system, the OSC devices with a functionalized fullerene derivative layer could reach a power conversion efficiency of 9.21 and 8.86% for C60-2DPE and C60-4HTPB , respectively

Densities and Viscosities for the Ternary Mixture of <i>n</i>‑Undecane (1) + Methyl Decanoate (2) + <i>n</i>‑Butanol (3) and Corresponding Binaries from <i>T</i> = 293.15 to 333.15 K and at Atmospheric Pressure

It has been proved that the general performance of aviation fuels can be improved with the addition of biofuels. To understand the fundamental physical properties of the blends, n-undecane, methyl decanoate, and n-butanol were chosen as model compounds to construct a mixed system. Densities (ρ) and viscosities (η) of the ternary system n-undecane + methyl decanoate + n-butanol and its corresponding binary systems n-undecane + methyl decanoate, n-undecane + n-butanol, and methyl decanoate + n-butanol were measured at different temperatures T = (293.15–333.15 K) and atmospheric pressure p = 0.1 MPa. The excess molar volumes (VmE) and the viscosity deviations (Δη) of the binary systems and the ternary system were correlated to the Redlich–Kister equation and four semi-empirical equations, respectively. The VmE values of the ternary system and binary systems are all positive over the entire concentration range at each experimental temperature, while their Δη values are all negative. The experimental results can provide reliable data for the compatibility of biofuels and fossil fuels

Leaching assessments of toxic metals in waste plasma display panel glass

<div><p>The plasma display panel (PDP) is rapidly becoming obsolete, contributing in large amounts to the electronic waste stream. In order to assess the potential for environmental pollution due to hazardous metals leached from PDP glass, standardized leaching procedures, chemical speciation assessments, and bioavailability tests were conducted. According to the Toxicity Characteristic Leaching Procedure (TCLP), arsenic in back glass was present at 4.46 ± 0.22 mg/L, close to its regulation limit of 5 mg/L. Zn is not available in the TCLP, but its TCLP leaching concentration in back glass is 102.96 ± 5.34 mg/L. This is because more than 90% of Zn is in the soluble and exchangeable and carbonate fraction. We did not detect significant levels of Ag, Ba, or Cu in the TCLP leachate, and the main fraction of Ag and Ba is residual, more than 95%, while the fraction distribution of Cu changes SEP by SEP. Ethylenediamine tetraacetic acid (EDTA)- and diethylenetriamine pentaacetic acid (DTPA)-extractable Ag, As, Ba, Cu, Zn, and Ni indicate a lower biohazards potential. These results show that, according to the EPA regulations, PDP glass may not be classified as hazardous waste because none of the metals exceeded their thresholds in PDP leachate. However, the concentrations of As and Zn should be lowered in the manufacturing process and finished product to avoid potential pollution problems.</p><p>Implications: <i>The plasma display panel is rapidly becoming obsolete because of the liquid crystal display. In this study, the leachability of heavy metals contained in the waste plasma display panel glass was first examined by standardized leaching tests, typical chemical speciation assessments, and bioavailability tests, providing fundamental data for waste PDP glass recovery, recycling, and reuse.</i></p></div

A₃A′₃Zn₆Te₄O₂₄ (A = Na, A′ = Rare Earth) Garnets: A‑Site Ordered Noncentrosymmetric Structure, Photoluminescence, and Na-Ion Conductivity

A large number of oxides that adopt the centrosymmetric (CS) garnet-type structure (space group Ia3̅d) have been widely studied as promising magnetic and host materials. Hitherto, no noncentrosymmetric (NCS) garnet has been reported yet, and a strategy to NCS garnet design is therefore significant for expanding the application scope. Herein, for the series A3A′3Zn6Te4O24 (A = Na, A′ = La, Eu, Nd, Y, and Lu), we demonstrated that the structural symmetry evolution from CS Ia3̅d (A′ = La) to NCS I4122 (A′ = Eu, Nd, Y, and Lu) could be achieved due to the A-site cationic ordering-driven inversion symmetry breaking. Na3A′3Zn6Te4O24 (A′ = rare earth) are the first garnets that possess NCS structures with A-site cationic ordering. Diffuse reflectance spectra and theoretic calculations demonstrated that all these NCS garnets are indirect semiconductors. Moreover, their potential applications as host materials for red phosphors and Na-ion conductors were also investigated in detail, which firmly confirmed the NCS structure and A-site cationic ordering. Our findings have paved the way to design NCS or even polar garnets that show intriguing functional properties, such as ferroelectricity, multiferroicity, and second harmonic generation

Densities and Viscosities for the Ternary Mixtures of <i>n</i>‑Undecane (1) + Butylcyclohexane (2) + 1‑Pentanol (3) and Corresponding Binaries at <i>T</i> = (293.15 to 333.15) K

The actual composition is known to be highly responsible for the physical and chemical properties of a fuel. To understand the foundational physical properties of an aviation kerosene substitute mixture for hypersonic aircraft, n-undecane, butylcyclohexane, and 1-pentanol were used to construct a ternary system. The values of density (ρ) and viscosity (η) for the ternary system and three corresponding binaries were measured at temperatures T = (293.15 to 333.15) K and pressure p = 0.1 MPa. The Redlich–Kister equation was used to fit the excess molar volumes (VmE) and viscosity deviations (Δη) of the binary systems, while those of the ternary system were correlated with four semi-empirical formulas (Cibulka, Singh, Redlich–Kister, and Nagata–Tamura equations). The experimental results show that the VmE values of the three binary mixtures have a positive relationship with the mole fraction of nonpolar components, while Δη values have a negative relationship. The non-ideal behavior of mixtures is discussed from the perspective of molecular interactions and structural effects. This work provides data support and guidance for fuel compatibility research

Crystal Growth and First-Principles Calculations of the Mid-IR Laser Crystal Dy³⁺:PbGa₂S₄

A Dy3+-doped PbGa2S4 crystal with low phonon energy has been proved to be able to achieve the direct lasing of a mid-infrared laser. The single-crystal growth of Dy3+:PbGa2S4 was investigated in this work. On the basic of the high-purity polycrystalline material synthesized using a pressure-assisted method, a Dy3+:PbGa2S4 single crystal with φ 21 × 50 mm3 was successfully grown using the Bridgman method with a crucible–capsule technique. To understand the cleavage character of the PbGa2S4 crystal and get further insight into its electronic and phonon properties, the electronic, phonon, and mechanical properties of the PbGa2S4 host were investigated using first-principles calculations. PbGa2S4 exhibits not only a large electronic energy gap (2.76 eV) but also a low phonon energy (392 cm–1) due to the incorporation of heavy Pb atoms between the interlayers. The high-frequency phonon bands of PbGa2S4 are mainly contributed by the vibrations of Ga–S atoms in the layer network formed by GaS4 units. However, the weak Pb–S bonding connecting the alternating layers results in cleavage behavior of the PbGa2S4 crystal. We believe that the results of this paper could provide useful references for preparing or designing new chalcogenide hosts for mid-infrared lasers