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[en] The property of nano-powder was reviewed with emphasis on its Coulomb blockade effects. Ag-colloid of different concentration with different particle size was prepared. Ag-PVA composite colloid was obtained by mixing Ag-colloid with PVA solution. TEM showed that Ag particles (<100 nm) were uniformly dispersed in PVA. The resistivity at room and low temperatures and breakdown field strength of samples were investigated. The results show that dielectric properties of composite change while Ag content or distributing state changes. The composite with 20-30 nm Ag particles has a higher resistivity and breakdown field than its matrix. In a word, Coulomb blockade effects of metal powders could improve resistivity and breakdown field of its matrix
[en] Six new inorganic–organic hybrids based on rigid triangular N-containing ligands, NaCu"I_2(tib)_4(H_2O)_4[H_2PW"VW"V"I_1_1O_4_0][H_2PW"V"I_1_2O_4_0]·6H_2O (1), Cu"I"I_3(tib)_4Cl_4[H_2PW"V"I_1_2O_4_0]_2·4H_2O (2), Co(tib)_2[PW"V_3W"V"I_9O_3_8]·5H_2O (3), Cu"I"I_3(tib)_2[P_2Mo"V"I_5O_2_2(O_2)]·4H_2O (4), Mn(pytpy)_2Mo"V"I_4O_1_3 (5) and Co(pytpy)_2Mo"V"I_4O_1_3 (6) (tib=1,3,5-tris(1-imidazolyl)benzene, pytpy=4’-(4”-pyridyl)2,4’:6’,4”-terpyridine), have been hydrothermally synthesized. Single crystal X-ray diffraction studies revealed that compounds 1–4 display two-dimensional (2D) layered structures, and in compounds 1–3, the adjacent Keggin anions link with each other by W–O–W covalent interactions to form 1D inorganic chains. Compounds 5–6 are 3D “pillar-layer” frameworks based on bimetal–oxide layers pillared by the pytpy ligands. The compounds have been characterized by elemental analysis, powder X−ray diffraction, X-ray photoelectron spectroscopy and thermo gravimetric analyses. Moreover, the electrochemical and catalytic properties of compound 1 have been investigated as well. - Graphical abstract: Six new inorganic–organic hybrids based on rigid triangular N-containing ligands have been obtained under hydrothermal conditions and characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compounds 1–4 display two-dimensional (2D) layers structure, and in compounds 1–3, the adjacent Keggin anions link with each other by W–O–W covalent interactions to form 1D inorganic Keggin anions chains. Compounds 5–6 are 3D “pillar-layer” frameworks based on bimetal–oxide layers pillared by the pytpy ligands. - Highlights: • MOFs based on POMs have been prepared. • Six new compounds based on rigid triangular N-containing ligands. • The adjacent POMs only share the oxygen atom to form a 1D inorganic Keggin chains.
[en] The transport properties of the three scenarios of the strained graphene magnetic barriers, where the first one is composed of the strained stripe in the positive magnetic field and the pristine stripe in the negative magnetic field on the left and right sides respectively, the second one is just the result of exchanging the stripes in the first one, and the last one contains the fully strained stripes on both sides, have been investigated. It is found that the first two configurations own the same evolution behavior both in transmission and conductance versus the strain, the joint contributions from the strains in the first two configurations lead to the enhancement both in transmission and conductance in the third one. The strain tends to devastate the regular shape of the energy bands within the scope of higher momentum/energy, where the more severe damage is observed in the superlattices with the fully strained periodic unit cell. The uniformity of the periodic unit between the left and right stripes in the third scenario makes the energy gaps of the superlattices diminish and even disappear in contrast to its first two counterparts, where the discrepancy between the strained stripe on the left side and pristine stripe on the right side increases the inhomogeneity, and thus the energy gaps.
[en] Graphical abstract: Supramolecular photocatalyst of RGO-cyclodextrin-TiO2 was achieved, which showed high photocatalytic activity and adsorption capacity. Highlights: •Supramolecular photocatalyst of RGO-cyclodextrin-TiO2 was achieved. •β-CD molecules acted as linkers between RGO and monodisperse TiO2 nanoparticles. •Reduction of GO and preparation of RGO-cyclodextrin-TiO2 was simultaneous. •The prepared RGO-cyclodextrin-TiO2 shows high photocatalytic activity and adsorption capacity. -- Abstract: Reduced graphene oxide (RGO)/β-cyclodextrin (β-CD)/titanium oxide (TiO2) supramolecular photocatalyst was synthesized with a one-pot hydrothermal method. The reducing process was accomplished with the attaching of β-CD and generation of TiO2. β-CD acted as a linker between RGO and monodisperse TiO2 nanoparticles. The structure and composition of the hybrid had been characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermal gravimetric analysis, X-ray diffraction and Transmission electron microscopy. The as-prepared RGO-CD-TiO2 showed significant enhanced performance for phenol and Cr (VI) removal, due to the effective transfer of photo-generated electron from TiO2 to RGO and improved absorbance performance of the hybrid
[en] Little Higgs models with T-parity predict the existence of the new sources of flavor-violating interactions between SM fermions and mirror fermions. We analyze corrections to the anomalous magnetic dipole moments of leptons from Bar-Zee-type diagrams in the LHT model. We find that the contributions of the LHT model are not sensitive to the new flavor mixing matrix and the value is of the order of 10-11. (orig.)
[en] Highlights: • RGO/CoMoO_4 nanocomposites are prepared by microwave irradiation for the first time. • RGO/CoMoO_4 nanocomposites show a high specific capacitance of 322.5 F g"−"1. • Enhanced electrical conductivity leads to superior electrochemical performance. • Low crystallinity of CoMoO_4 is favorable to improve the electrochemical performance. - Abstract: A facile and efficient strategy for preparing reduced graphene oxide–cobalt molybdate (RGO/CoMoO_4) nanocomposites assisted by microwave irradiation for the first time is demonstrated. The resulting nanocomposites are comprised of CoMoO_4 nanoparticles that are well-anchored on graphene sheets by in situ reducing. The prepared RGO/CoMoO_4 nanocomposites have been thoroughly characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and X-ray photoelectron spectroscopy. Importantly, the prepared nanocomposites exhibit excellent electrochemical performance for supercapacitors. Results show that RGO/CoMoO_4 nanocomposites exhibited much better electrochemical capability than pure-CoMoO_4 and RGO/CoMoO_4 for annealing. RGO/CoMoO_4 nanocomposites with 37.4 wt% CoMoO_4 content achieved a specific capacitance about 322.5 F g"−"1 calculated from the CV plots at 5 mV s"−"1, which was higher than that of pure-CoMoO_4 (95.0 F g"−"1) and RGO/CoMoO_4 for annealing (102.5 F g"−"1). The good electrochemical performance can be attributed to the synergistic effects of the individual components
[en] Highlights: • RGO/CoWO_4 composites were successfully prepared through a facile hydrothermal method. • RGO/CoWO_4 composites show much higher specific capacitances than pure CoWO_4. • Enhanced electrical conductivity leads to superior electrochemical performance. - Abstract: A facile one-pot hydrothermal method was provided for synthesis of the reduced graphene oxide-cobalt tungstate (RGO/CoWO_4) nanocomposites with the enhanced electrochemical performances for supercapacitors for the first time. The resulting nanocomposites are comprised of CoWO_4 nanospheres that are well-anchored on graphene sheets by in situ reducing. The prepared RGO/CoWO_4 nanocomposites have been thoroughly characterized by Fourier–transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, Thermogravimetric analysis, Scanning electron microscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, and N_2 adsorption–desorption. Importantly, the prepared nanocomposites exhibit superior electrochemical performance to CoWO_4 as electrodes for supercapacitors. As a result, RGO/CoWO_4 nanocomposites with 91.6 wt% CoWO_4 content achieved a specific capacitance about 159.9 F g"−"1 calculated from the CV curves at 5 mV s"−"1, which was higher than that of CoWO_4 (60.6 F g"−"1). The good electrochemical performance can be attributed to the increased electrical conductivity and the creation of new active sites due to the synergetic effect of RGO and CoWO_4 nanospheres. The cyclic stability tests demonstrated capacitance retention of about 94.7% after 1000 cycles, suggesting the potential application of RGO/CoWO_4 nanocomposites in energy-storage devices
[en] A series of inorganic organic hybrid materials based on polyoxometalates(POMs), namely, [M"I"I(HL)_2(H_2O)_2][Mo"V"I_6O_2_0] [M=Co (1), Ni (2), Cu (3), Zn (4)], [Mn"I"VL_2(H_2O)_2][Mo"V"I_6O_2_0] (5), and (HL)_3PMO_1_2O_4_0 (6) [L=3-(4-pyridyl)pyrazole], have been synthesized. The compounds have been characterized by elemental analysis, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. The results from single-crystal X-ray diffraction indicate that 1–5 are isostructural. It is worth noting that the polyanions are bridged by Mo–O–Mo to form 1D inorganic chains, which are further connected via M ions to form 2D nets. In compound 6, the ligands are used as the positive ions to balance the charge of the compound. Moreover, the magnetic properties of compound 5 have also been investigated in detail. - Graphical abstract: In complex 1, The Co ion is six coordinated by four oxygen atoms from two Mo_6O_2_0 and two water molecules, and two N atoms from two different ligand. It is noticeable that there is an one-dimensional chain molybdate, which is combined by O–Mo–O, then the chain parallel with each other, the Mo_6 anion acts as a bidentate ligand providing O7 atoms to bridge CoII ions to form a 2D inorganic layer. Finally every nets become 3D structure by hydrogen bond. - Highlights: • Novel inorganic–organic hybrid materials have been prepared. • Compounds 1–5 contain the 1D molybdate chains composed of (MoO_6) octahedra. • The 1D chains parallel with each other to form a 2D inorganic layer
[en] Four new polyoxometalate(POM)–templated metal–organic frameworks based on flexible ligands, namely, [Cu_6(bip)_1_2(PMo"V"I_1_2O_4_0)_2(PMo"VMo"V"I_1_1O_4_0O_2)]·8H_2O(1), [Cu"I_3Cu"I"I_3(bip)_1_2(PMo"V"I_1_2O_4_0)_2(PMo"V_1_2O_3_4)]·8H_2O(2), [Ni_6(bip)_1_2(PMo"V"I_1_2O_4_0)(PMo"V"I_1_1Mo"VO_4_0)_2]Cl·6H_2O(3), [Co"I"I_3Co"I"I"I_2(H_2bib)_2(Hbib)_2(PW_9O_3_4)_2(H_2O)_6]·6H_2O(4) (bip=1,3-bis(imidazolyl)propane, bib=1,4-bis(imidazolyl)butane) have been obtained under hydrothermal condition and characterized by single-crystal X-ray diffraction analyses, elemental analyses, and thermogravimetric (TG) analyses. The studies of single crystal X-ray indicate that compounds 1–3 crystallize in the trigonal space group P-3, and compound 4 crystallizes in the triclinic space group P-1. Compounds 1 and 3 represent 3D frameworks, and POMs as the guest molecules are incorporated into the cages which are composed of the ligands and metals, while compounds 2 and 4 show 3D frameworks by hydrogen bonds. This compounds provide new examples of host–guest compounds based on flexible bis(imidazole) ligands. In addition, the electrochemical property and the catalytic property of compound 1 have also been investigated. - Graphical abstract: Four inorganic–organic hybrid compounds based polyoxometalates (POMs) and flexible ligands, namely, have been obtained under hydrothermal conditions and characterized by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, and thermogravimetric (TG) analyses. Compounds 1–3 are new examples of host–guest compounds based on flexible bis(imidazole) ligands and POMs as the guest molecules are incorporated into the cages which are composed of the ligands and metals. - Highlights: • Polyoxometalate–templated metal–organic frameworks have been prepared. • POMs as the guest molecules are incorporated into the cages. • The cages are flexibility based on flexible bis(imidazole) ligands
[en] Room temperature methane (CH_4) gas sensing properties of Au-decorated vanadium oxide (VO_x) nanostructured films have been prepared by dc-magnetron sputtering of V metal, followed by rapid thermal annealing (RTA) in O_2 atmosphere from 470 °C to 500 °C on the sapphire substrate. The structural properties of the Au/VO_x films were measured by X-ray diffraction (XRD) and vanadium oxide phases were found and identified as VOx. The films showed a cracking and porous morphology structure, measured by field emission scanning electron microscope (FESEM). The CH_4-sensing properties of the sensor based on Au/VO_x composite films were carried out in the temperatures span ranging from room temperature (∼25 °C) to 100 °C. The films sensors achieved their maximum response values toward CH_4 at room temperature (RT) and the optimal concentration at the concentration of 1500 ppm. At RT, the sensor exhibited higher gas response, good repeatability and excellent selectivity characteristics toward CH_4 gas due to its high specific surface area, special structure, and large amounts of oxygen vacancies. Obtained results revealed that the Au/VO_x films sensors showed a broad commercial applications prospect to detect CH_4 in the field of RT. - Highlights: • Au/VO_x films were prepared involving sputtering and rapid thermal annealing. • A mixture of vanadium dioxide and vanadium pentoxide were synthesized. • The Au/VO_x films methane sensor could operate at room temperature (∼25 °C). • The optimal operating concentration was obtained at 1500 ppm toward methane.