Experimental measurement of viscosity and electrical conductivity of water-based γ-Al2O3/MWCNT hybrid nanofluids with various particle mass ratios

Journal of Thermal Analysis and Calorimetry - The hybridization of nanoparticles is a concept employed for the improvement of the thermal properties of nanofluids. Presently, there is a scarcity of...     

Heat transfer analysis of Cu–Al2O3 hybrid nanofluid with heat flux and viscous dissipation

Journal of Thermal Analysis and Calorimetry - Current research explores the influence of Cu–Al2O3 MHD hybrid nanofluid on heat conveyance and flow in a permeable channel with heat flux and...     

Magnetohydrodynamic flow of Cu–Fe3O4/H2O hybrid nanofluid with effect of viscous dissipation: dual similarity solutions

Journal of Thermal Analysis and Calorimetry - This study shows multiple solutions, heat transfer characteristics, and stability analysis of the magnetohydrodynamic (MHD) flow of hybrid nanofluid...     

Targeted analysis with benchtop quadrupole–orbitrap hybrid mass spectrometer: Application to determination of synthetic hormones in animal urine

Sensitive and unequivocal determination of analytes/contaminants in complex matrices is a challenge in the field of food safety control. In this study, various acquisition modes (Full MS/AIF, Full MS + tMS/MS, Full MS/dd MS/MS and tSIM/ddMS/MS) and parameters of a quadrupole–orbitrap hybrid mass spectrometer (Q Exactive) were studied in detail. One of the main conclusions has been that, reducing the scan range for Full MS (using the quadrupole) and targeted modes give higher signal-to-noise (S/N) ratios and thereby better detection limits for analytes in matrix. The use of Q Exactive in a complex case, for the confirmatory analysis of hormones in animal urine is presented. A targeted SIM data dependent MS/MS (tSIM/ddMS/MS) acquisition method for determination of eight synthetic hormones (trenbolone, 17α ethinylestradiol, zeranol, stanozolol, dienestrol, diethylstilbestrol, hexestrol, taleranol) and a naturally occurring hormone (zearalenone) in animal urine were optimized to have sensitive precursors from targeted SIM mode and trigger MS/MS scans over the entire chromatograph peak. The method was validated according to EC/657/2002. CCα (decision limit) for the analytes ranged between 0.11 μg L⁻¹ and 0.69 μg L⁻¹ and CCβ (detection capability) ranged between 0.29 μg L⁻¹ and 0.90 μg L⁻¹.     

Binary α-Fe2O3–Co3O4 nanostructures for advanced oxidation process: Role of synergy for enhanced catalysis

Iron and its binary oxides are meticulously exploited for environmental remediations. However, only limited studies have been carried out on the degradation of industrial organics by advanced oxidation process. In this study, iron oxide, cobalt oxide, and iron–cobalt binary oxides were synthesized by a modified hydrothermal method as heterogeneous Fenton-like catalysts for the removal of methylene blue (MB) from wastewaters. The oxide nanostructures were characterized by different analytical techniques. Studying the effects of various parameters such as catalyst dose, MB concentration, and H₂O₂ concentration, the reaction conditions were optimized to enhance the removal of MB dye. The results revealed that α-Fe₂O₃–Co₃O₄ shows much higher activity than both Co₃O₄ and α-Fe₂O₃ for the degradation of MB at room temperature and beyond. The binary α-Fe₂O₃–Co₃O₄ shows degradation efficiency of 96.4% at 65 °C within 60 min. Furthermore, the binary α-Fe₂O₃–Co₃O₄ catalyst retains its activity for up to four successive cycles. A probable mechanism is also proposed, involving the generation of ‧OH radical as well as Fe²⁺/Fe³⁺ or Co²⁺/Co³⁺ redox couple of the binary α-Fe₂O₃–Co₃O₄ catalyst.     

Effect of MWCNT–Fe3O4/water hybrid nanofluid on the thermal performance of ribbed channel with apart sections of heating and cooling

Journal of Thermal Analysis and Calorimetry - A two-dimensional (2D) numerical simulation is performed to simulate the laminar forced convection of a nanofluid in a ribbed channel with apart...     

Lattice Boltzmann study of multi-walled carbon nanotube (MWCNT)-Fe3O4/water hybrid nanofluids natural convection heat transfer in a Π-shaped cavity equipped by hot obstacle

In the present paper, the effect of nanofluid and the hot obstacle in a Π-shaped cavity is investigated. Lattice Boltzmann method is used to simulate the fluid flow and heat transfer. The effects of the parameters such as the nanoparticle solid volume fraction, the Rayleigh number, aspect ratio of cavity and hot obstacle position on the flow pattern and heat transfer parameters are studied. The numerical results are compared with previous results for validation, and a good agreement obtained. It is found that the average Nusselt number is increased by increasing the nanoparticle solid volume fraction, the Rayleigh number and the aspect ratio of cavity. Moreover, the effect of Rayleigh number on the average Nusselt number at high Rayleigh numbers (10⁵–10⁶) is more pronounced than that at low Rayleigh numbers (10³–10⁴) due to the different heat transfer mechanisms. The position of the hot obstacle affects the heat transfer significantly. When the hot obstacle is located on the center, the heat transfer is more effective.

     

On the hydrothermal features of radiative Fe3O4–graphene hybrid nanofluid flow over a slippery bended surface with heat source/sink

Journal of Thermal Analysis and Calorimetry - The present investigation concentrates on the hydrothermal features of both hybrid nanofluid and usual nanofluid flow over a slippery permeable bent...     

Charge density analysis of 2-methyl-4-nitro-1-phenyl-1H-imidazole-5-carbonitrile: an experimental and theoretical study of C≡N···C≡N interactions

The experimental charge density distribution was determined for 2-methyl-4-nitro-1-phenyl-1H-imidazole-5-carbonitryle, using the Hansen-Coppens multipole model. Free R factor calculations were performed with MoPro software to find optimal restraints for a physically meaningful model. The crystal packing is determined to some extent by weak C-H···O and C-H···N hydrogen bonds but mostly by a lateral electrostatic interaction between antiparallel side-by-side C≡N groups. Electrostatic energy calculations were performed based on the experimental data and are in line with the high-level, explicitly correlated theoretical SCS-RI-MP2-F12 calculations of total energy. The molecular dipole moment and atomic charge values were compared for different experimental and theoretical models, to highlight the dependence of the electrostatic property outputs on the applied restraints. Interesting O···O contacts are also described. The results are compared with two recently investigated nitroimidazole derivatives, namely, 1-(2'-aminophenyl)-2-methyl-4-nitroimidazole and 1-phenyl-4-nitroimidazole.     

A combined theoretical and experimental study to improve the thermal stability of recombinant D-lactate dehydrogenase immobilized on a novel superparamagnetic Fe3O4NPs@metal–organic framework

Lactate dehydrogenase (LDH) is an enzyme that catalyzes the reduction of nicotinamide adenine dinucleotide (NADH) and pyruvate to nicotinamide adenine dinucleotide (NAD⁺) and D-lactate in the final step of anaerobic glycolysis. This enzyme belongs to the family of oxidoreductases. Humans possess two isoforms of LDH enzyme: NAD-dependent L-lactate dehydrogenase (L-LDH) and NAD-dependent D-lactate dehydrogenase (D-LDH). D-LDH is released during tissue damage, and is a sign of diseases such as kidney stones, heart failure, and some types of cancers and appendicitis. Accordingly, the design and construction of biosensors for the determination of lactate levels are important. The thermal sensitivity of D-LDH and low protein production in the host bacteria limit the use of this protein in certain applications. To solve these problems, two solutions were used in this study. First, the codon-optimized 1008 bp D-LDH gene fused with a histidine tag was cloned at the NcoI/XhoI sites and expressed in E. coli BL21. Second, a new metal–organic framework (Fe₃O₄NPs@Ni-MOF) was synthesized and used for immobilization and stabilization of D-LDH. Fe₃O₄NPs@Ni-MOF core-shell nanocomposites were characterized by Fourier transform infrared spectroscopy, vibrating sample magnetometer, scanning electron microscopy, X-ray diffraction, and the Brunauer–Emmett–Teller method. In comparison with the free enzyme, the immobilized enzyme presented better stability at high temperatures. The immobilization of the enzyme could be useful because most reactions happen at high temperatures in industry. To examine the effect of Fe₃O₄NPs@Ni-MOF on the adsorption and conformation of D-LDH at the atomistic level, a molecular dynamics simulation was carried out. Our study showed that the interaction between Fe₃O₄NPs@Ni-MOF and D-LDH involved van der Waals interactions, hydrophobic interaction energies, cation–π interaction between the Ni ions of the MOF with the enzyme residues and also, the hydrogen bond interactions between enzyme and heteroatoms in the MOF. Root mean square fluctuation and secondary structure analysis showed that Fe₃O₄NPs@Ni-MOF protected the conformation of the enzyme.     

In situ synthesis of an inorganic–organic hybrid based on a molybdenum-oxo chain: [Cu2(pz)(Mo3O10)] n

A polyoxomolybdate, [Cu₂(pz)(Mo₃O₁₀)] _n (pz?=?pyrazine) (1), has been synthesized hydrothermally and characterized by elemental analysis, IR, X-ray photoelectron spectra, and thermogravimetric analysis. Single-crystal X-ray diffraction demonstrates that 1 has a 3-D architecture constructed by combination of {Mo₃O₁₀} units and [Cu₂(pz)]²⁺. All the terminal oxygen atoms of the polyoxomolybdate are coordinated by univalent copper. Pyrazine came from in situ decarboxylation of 2-pyrazinecarboxylic acid and Cu⁺ from the in situ reduction of Cu²⁺ during the hydrothermal synthesis.     

Structural phase transition,thermal analysis,and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH3)2NH2]2ZnBr4

An organic–inorganic hybrid compound [(CH₃)₂NH₂]₂ZnBr₄ has been prepared at room temperature under the slow evaporation method. Its structure was solved at 150 K using the single-crystal X-ray diffraction method. [(CH₃)₂NH₂]₂ZnBr₄ crystallizes in the monoclinic system – a = 8.5512 (12) Å, b = 11.825 (2) Å, c = 13.499 (2) Å, β = 90.358 (6)°, V = 1365 (4) ų, and Z = 4, space group P2₁/n. In the structure of [(CH₃)₂NH₂]₂ZnBr₄, tetrabromozincate anions are connected to organic cations through N–H⋯ Br hydrogen bonds. Differential scanning calorimetry (DSC) measurements indicate that [(CH₃)₂NH₂]₂ZnBr₄ undergoes four phase transitions at T₁ = 281 K, T₂ = 340 K, T₃ = 377 K, and T₄ = 408 K. Meanwhile, several studies including DSC measurements and variable-temperature structural analyses were performed to reveal the structural phase transition at T = 281 K in [(CH₃)₂NH₂]₂ZnBr₄. Conductivity and dielectric study as a function of temperature (378 < T [K] < 423) and frequency (10⁻¹ < f [Hz] < 10⁶) were investigated. Analysis of equivalent circuit, alternating current conductivity, and dielectric studies confirmed the phase transition at T₄. Conduction takes place by correlated barrier hopping in each phase.     

Structure and characterization of an organic–inorganic hybrid compound: [Pr(NMP)4(H2O)4]H[SiMo12O40]·2NMP·1.5H2O

The organic–inorganic hybrid compound containing the cationic donor [Pr(NMP)₄(H₂O)₄]³⁺ and polyoxometalate acceptors of the Keggin structural type SiMo₁₂O₄₀ ^4– has been synthesized in high yield (83%). An X-ray crystallographic study showed that the crystal structure was constructed by electrostatic attraction and O—HO hydrogen bonds between coordinated water molecules and the dodesilicontungstate polyanion. Furthermore, the e.s.r. spectra in the solid state at 110 K indicate the presence of a Mo⁵⁺.     

A new paratungstate-A-based organic–inorganic hybrid compound: Synthesis,structure and photocatalytic property of [Co(en)3]2[H2W7O24]·8H2O

A new paratungstate-A-based organic–inorganic hybrid compound with the chemical formula of [Co(en)₃]₂[H₂W₇O₂₄]·8H₂O (en = ethylenediamine) (1) has been hydrothermally synthesized and structurally characterized by the elemental analysis, IR, TG, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group P2₁/c with a = 17.216(3) Å, b = 14.986(3) Å, c = 23.088(8) Å, β = 128.151(2)°, V = 4684.2 Å³, Z = 1, R₁ = 0.0484, and wR₂ = 0.1087. The structure of 1 consists of the [H₂W₇O₂₄]⁴⁻ building blocks and [Co(en)₃]²⁺ metal-organic cationic moieties, which are packed together via the electrostatic forces and extensive hydrogen-bonding interactions to form a three-dimensional supramolecular framework. Interestingly, compound 1 represents the first structurally-defined hybrid compound based on the metastable paratungstate-A polyoxoanions and metal–organic units. The degradation of Rhodamine-B (RhB) under UV irradiation with 1 as the heterogeneous photocatalyst has been investigated, showing a good photocatalytic property of 1 for RhB degradation.     

Two fumarato-bridged Co(II) coordination polymers: syntheses,crystal structures and properties of Co(H2O)4L and [Co3(H2O)4(OH)2L2]·2H2O with H2LHOOCCHCHCOOH

Two fumarato-bridged Co(II) coordination polymers Co(H₂O)₄L 1 and [Co₃(H₂O)₄(OH)₂L₂]·2H₂O 2 with H₂LHOOCCH CHCOOH were prepared. Complex 1 consists of polymeric chains _∞¹[Co(H₂O)₄(C₄H₂O₄)_2/2], which result from octahedrally coordinated Co atoms bridged by bis-monodentate fumarate anions and are assembled by interchain hydrogen bonds. Within 2, the edge-shared Co₂O₁₀ bi-octahedra are connected to the CoO₆ octahedra to form 1D cobalt oxide chains and 3D open framework generated from the chains inter-linked by bis-bidentate fumarate anions displays rhombic tunnels, which are filled with the lattice H₂O molecules. Thermal and magnetic behaviors of both the title coordination polymers are discussed. Crystal data: (1) monoclinic, P2₁/c, Z=4, a=7.493(1) Å, b=14.377(1) Å, c=7.708(1) Å, β=99.54(1)°, V=818.9(2) Å³, R₁=0.0304, and wR₂=0.0669 for 1487 observed reflections (I⩾2σ(I)) out of 1877 unique reflections; (2) monoclinic, P2₁/c, Z=2, a=6.618(1) Å, b=8.172(2) Å, c=15.578(3) Å, β=96.30(3)°, V=837.4(3) Å³, R₁=0.0360 and wR₂=0.0663 for 1442 observed reflections (I⩾2σ(I)) out of 1927 unique reflections.     

Synthesis and characterization of silica-coated Fe3O4 nanoparticle@silylpropyl triethylammonium polyoxometalate as an organic–inorganic hybrid heterogeneous catalyst for the one-pot synthesis of tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones

In this study, silica-coated Fe₃O₄ nanoparticle@silylpropyl triethylammonium polyoxometalate catalyst was fabricated and characterized using atomic absorption, inductively coupled plasma optical emission spectrometry, elemental analysis, thermogravimetric analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry analyses. The activity of this catalyst was examined in the synthesis of tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones. The bonding of the polyoxometalate to the surface of the nanoparticles exhibited excellent catalytic activity in this synthesis. Besides, the catalyst showed good reusability and recovery from the reaction mixture. Tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones were synthesized in high yields in the presence of inexpensive supported solid acid catalysts under classical heating conditions.