Effects of V and Gd doping on novel positive colossal electroresistance and quantum transport in PbPdO2 thin films with (002) preferred orientation.

In this work, PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 thin films with (002) preferred orientation were prepared using a pulsed laser deposition technique. The temperature dependence of resistivities ρI(T) was investigated under various applied DC currents. Colossal electroresistance (CER) effects were found in PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2. It was found that the positive CER values of PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 reach 3816% and 154% for I = 1.00 µA at 10 K, respectively. In addition, the ρI(T) cycle curves of PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 thin films showed a critical temperature similar to that of PbPdO2 (Tc = 260 K). Particularly, charge transfer between O1- and O2- was confirmed by in situ XPS. Additionally, based on first-principles calculations and internal electric field models, the CER and magnetic sources in PbPd0.9V0.1O2 and PbPd0.9Gd0.1O2 can be well explained. Finally, it was found that thin film samples doped with V and G ions exhibit weak localization (WL) and weak anti-localization (WAL) quantum transport properties. Ion doping leads to a transition from WAL to WL. The study results indicate that PbPdO2, one of the few oxide topological insulators, can exhibit novel quantum transport behavior after ion doping.

Removal of diclofenac sodium from water using a polyacrylonitrile mixed-matrix membrane embedded with MOF-808.

MOF-808, owing to the synergistic effect of its large surface area and surface charge matching, showed a diclofenac sodium (DCF) removal capacity as high as 630 mg g-1, and the ability to adsorb 436 mg g-1 DCF in two hours, outperforming many common Zr-MOFs under the same conditions. Importantly, a series of free-standing mixed-matrix membranes made by combining polyacrylonitrile with MOF-808 were fabricated and exhibited high efficiency of removing DCF from water via an easily accessible filtration method.

Coral-like CoSe2@N-doped carbon with a high initial coulombic efficiency as advanced anode materials for Na-ion batteries.

Na-ion batteries (NIBs) have attracted great interest as a possible technology for grid-scale energy storage for the past few years owing to the wide distribution, low cost and environmental friendliness of sodium resources and similar chemical mechanisms to those of established Li-ion batteries (LIBs). Nonetheless, the implementation of NIBs is seriously hindered because of their low rate capability and cycling stability. This is mainly because the large ionic size of Na+ can reduce the structural stability and cause sluggish reaction kinetics of electrode materials. Herein, three-dimensional nanoarchitectured coral-like CoSe2@N-doped carbon (CL-CoSe2@NC) was synthesized through solvothermal and selenizing techniques. As a result, CL-CoSe2@NC for NIBs at 2 A g-1 exhibits an ultrahigh specific capacity of 345.4 mA h g-1 after 2800 cycles and a superhigh initial coulombic efficiency (ICE) of 93.1%. Ex situ XRD, HRTEM, SAED and XPS were executed to study the crystal structure evolution between Na and CoSe2 during sodiation/de-sodiation processes. The aforementioned results indicate that the improved sodium storage property of CL-CoSe2@NC could be attributed to better electrode kinetics and a stable SEI film because of the 3D nanoarchitecture and the existence of the NC layer.

Noble metal-free bimetallic phosphide-decorated Zn0.5Cd0.5S with efficient photocatalytic H2 evolution.

The rapid recombination of charge carriers in semiconductor-based photocatalysts results in a low photocatalytic activity. Co-catalysis is considered a promising strategy to improve the photocatalytic performance of semiconductors. In this study, a bimetallic phosphide was grown by a facile in situ growth method. Loading the cocatalyst (7 wt% NiCoP) leads to activity enhancement by a factor of approximately 27 times in the visible-light-driven hydrogen evolution relative to the pristine Zn0.5Cd0.5S. The photocatalysis shows a high hydrogen evolution rate of 19.5 mmol g-1 h-1, which is much higher than that of the single metal phosphide (Ni2P: 7.0 mmol g-1 h-1; CoxP: 8.1 mmol g-1 h-1) and 7 wt% Pt modified Zn0.5Cd0.5S (0.3 mmol g-1 h-1). Its apparent quantum efficiency reaches 41.6% at 420 nm. Moreover, the photocatalyst exhibits a remarkable photostability for five consecutive cycles of photocatalytic activity measurements with a total reaction time of 15 hours. The excellent photocatalytic activity of the photocatalyst was attributed to the in situ-formed NiCoP cocatalyst, which not only acts as a reactive site but also accelerates the separation of charge carriers.

From Centrosymmetry to Noncentrosymmetry: Precise Structural Regulation and Characterization on ZnHPO3·2H2O Polymorphs.

Polymorphs of ZnHPO3·2H2O with centrosymmetry (Cmcm) and noncentrosymmetry (C2) structures were prepared by modified solution evaporation and seed-crystal-induced secondary nucleation methods. In Cmcm-ZnHPO3·2H2O, the zinc atoms are only octahedrally coordinated, while in C2-ZnHPO3·2H2O, they feature both tetrahedral and octahedral coordination. As a result, Cmcm-ZnHPO3·2H2O features a 2D layered structure with lattice water molecules located in the interlayer space, while C2-ZnHPO3·2H2O features a 3D electroneutral framework of tfa topology connected by Zn(1)O4, Zn(2)O6, and HPO3 units. The UV-visible diffuse reflectance spectra associated with Tauc's analyses give a direct bandgap of 4.24 and 4.33 eV for Cmcm-ZnHPO3·2H2O and C2-ZnHPO3·2H2O, respectively. Moreover, C2-ZnHPO3·2H2O exhibits a weak second harmonic generation (SHG) response and a moderate birefringence for phase matching, indicating its potential as a nonlinear optical material. Detailed dipole moment calculation and analysis confirmed that the SHG response mainly derived from the HPO3 pseudo-tetrahedra.

Constructing Co-S interface chemical bonds over Co@NC/ZnIn2S4 for an efficient solar-driven photocatalytic H2 evolution.

Developing novel photocatalysts with an intimate interface and sufficient contact is significant for the separation and migration of photogenerated carriers. In this work, a novel Co@NC/ZnIn2S4 heterojunction with a strong Co-S chemical bond was formed at the interface between Co@NC and ZnIn2S4, which accelerated charge separation. Meanwhile, the recombination of the electron-hole pairs was further restricted by the Co@NC/ZnIn2S4 Schottky junction. The Co@NC (5 wt%)/ZnIn2S4 composite exhibited an H2 evolution rate of 33.3 µmol h-1, which is 6.1 times higher than that of the pristine ZnIn2S4, and Co@NC/ZnIn2S4 showed excellent stability in the photocatalytic water splitting reaction. Its apparent quantum yield reached 38% at 420 nm. Furthermore, the Kelvin probe test results showed that the interfacial electric field formed as the driving force for interface charge transfer was oriented from Co@NC to ZnIn2S4. In addition, the Co-S bond as a high-speed channel facilitated the interfacial electron transfer. This work reveals that in situ formed chemical bonds will pave the way for designing high-efficiency heterojunction photocatalysts.

Ultrafast charge separation in a WC@C/CdS heterojunction enables efficient visible-light-driven hydrogen generation.

The rapid recombination of photogenerated carriers and strong photocorrosion have considerably limited the practical application of CdS in the field of photocatalysis. Loading a cocatalyst has been widely utilized to largely enhance photocatalytic activity. In the present work, a WC@C cocatalyst was prepared by a novel molten salt method and explored as an efficient noble-metal-free cocatalyst to significantly enhance the photocatalytic hydrogen evolution rate of CdS nanorods. The WC@C/CdS composite photocatalyst with a 7 wt% content of WC@C showed the highest photocatalytic hydrogen evolution rate of 8.84 mmol g-1 h-1, which was about 21 and 31 times higher than those of CdS and 7 wt% Pt/CdS under visible light irradiation. A high apparent quantum efficiency (AQY) of 55.28% could be achieved under 420 nm monochromatic light. Furthermore, the photocatalytic activity of the 7 wt% WC@C/CdS photocatalyst exhibited good stability for 12 consecutive cycles of the photocatalytic experiment with a total reaction time of 42 h. The excellent photocatalytic performance of the photocatalyst was attributed to the formation of a Schottky junction and the loading cocatalyst, which not only accelerated the separation of the photogenerated carrier but also provided a reactive site for hydrogen evolution. This work revealed that WC@C could act as an excellent cocatalyst for enhancing the photocatalytic activity of CdS nanorods.

Phosphorus doped and defect modified graphitic carbon nitride for boosting photocatalytic hydrogen production.

The enhancement of photogenerated carrier separation efficiency is a significant factor in the improvement of photocatalyst performance in photocatalytic hydrogen evolution. Heteroatom doping and defect construction have been considered valid methods to boost the photocatalytic activity of graphitic carbon nitride. Herein, we report graphitic carbon nitride modified with P doping and N defects (PCNx), and the effects of doping and defects were investigated in photocatalytic H2 evolution. Its hydrogen evolution rate can reach up to about 59.1 µmol h-1, which is more than 123.1 times higher than pristine graphitic carbon nitride under visible light irradiation. Importantly, the apparent quantum efficiency reaches 8.73% at 420 nm. The excellent performance of the PCNx photocatalyst was attributed to the following aspects: (I) the large BET surface area of PCNx affords more active sites for H2 production and (II) the introduction of P and N defects can accelerate the charge carrier separation and transfer efficiency, leading to more efficient photocatalytic hydrogen production. The photocatalyst showed obviously enhanced activities.

Rational construction of yolk-shell CoP/N,P co-doped mesoporous carbon nanowires as anodes for ultralong cycle life sodium-ion batteries.

Owing to the natural abundance and low-cost of sodium, sodium-ion batteries offer advantages for next-generation portable electronic devices and smart grids. However, the development of anode materials with long cycle life and high reversible capacity is still a great challenge. Herein, we report a yolk-shell structure composed of N,P co-doped carbon as the shell and CoP nanowires as the yolk (YS-CoP@NPC) for a hierarchically nanoarchitectured anode for improved sodium storage performance. Benefitting from the 1D hollow structure, the YS-CoP@NPC electrode exhibits an excellent cycling stability with a reversibly capacity of 211.5 mA h g-1 at 2 A g-1 after 1000 cycles for sodium storage. In-depth characterization by ex situ X-ray photoelectron spectroscopy and work function analysis revealed that the enhanced sodium storage property of YS-CoP@NPC might be attributed to the stable solid electrolyte interphase film, high electronic conductivity and better Na+ diffusion kinetics.

Design and synthesis of yolk-shell Fe2O3/N-doped carbon nanospindles with rich oxygen vacancies for robust lithium storage.

Ferric oxide (Fe2O3) is an attractive anode material for lithium-ion batteries (LIBs) with a high theoretical capacity of 1005 mA h g-1. However, its practical application is greatly restrained by the rapid capacity fading caused by the large volume expansion upon lithiation. To address this issue, we have designed and synthesized a unique yolk-shell Fe2O3/N-doped carbon hybrid structure (YS-Fe2O3@NC) with rich oxygen vacancies for robust lithium storage. The obtained results show that YS-Fe2O3@NC delivers a high reversible capacity of 578 mA h g-1 after 300 cycles at a current density of 5 A g-1, about 11 times that (53.7 mA h g-1) of pristine Fe2O3. Furthermore, a high specific capacity of 300.5 mA h g-1 even at 10 A g-1 is achieved. The high reversible capacities, excellent rate capability and cycle stability of YS-Fe2O3@NC might be attributed to the elaborate yolk-shell nanoarchitecture. Moreover, electron percolation and a local built-in electric field induced by oxygen vacancies in the Fe2O3 matrix could also enhance the kinetics of Li+ insertion/deinsertion.

Mixed-Cation Mixed-Metal Halide Perovskites for Photovoltaic Applications: A Theoretical Study.

Perovskite solar cells based on multiple cations have shown excellent optoelectronic properties with high power conversion efficiency. Herein, the structural, electronic, and optical properties of mixed-cation mixed-metal perovskites MA1-x Cs x Pb0.25Sn0.75I3 were studied by employing the first-principles calculations for the first time. Our calculated results reveal that these perovskite materials possess direct band gaps in the range of 1.0-1.3 eV. Moreover, these compounds show excellent photovoltaic performance in terms of strong optical absorption coefficients compared with MAPbI3. Particularly, they also exhibit good structural stability and decrement of lead content. These results demonstrated that mixed-cation mixed-metal perovskites may be potential candidates for high-efficiency light-absorbing materials.

Two Indium Sulfate Tellurites: Centrosymmetric In2(SO4)(TeO3)(OH)2(H2O) and Non-centrosymmetric In3(SO4)(TeO3)2F3(H2O).

Two new indium sulfate tellurites, namely, In2(SO4)(TeO3)(OH)2(H2O) and In3(SO4)(TeO3)2F3(H2O), were synthesized by hydrothermal method in a one-pot reaction. Their pure phase yields have been successfully optimized to 76% and 21%, respectively. In2(SO4)(TeO3)(OH)2(H2O) crystallized in centrosymmetric (CS) space group P21/n, while In3(SO4)(TeO3)2F3(H2O) formed a non-centrosymmetric (NCS) and chiral space group P212121. The CS compound features a 2D layered structure composed of 2D indium oxide layers decorated by sulfate tetrahedra and tellurite groups. The NCS compound displays a 3D network consisting of indium tellurite layers bridged by sulfate tetrahedra. Powder second harmonic generation measurements disclosed that In3(SO4)(TeO3)2F3(H2O) exhibits a weak frequency-doubling efficiency about 11% of the commercial KDP. Its powder laser damage threshold quantity was estimated to be 79.6 MW/cm2, which is about 36 times that of AGS. The two samples present wide optical band gaps of 4.86 and 4.10 eV, respectively, which were determined by Te, In, and O atoms based on density functional theory calculations.

Functionalized magnetic mesoporous silica/poly(m-aminothiophenol) nanocomposite for Hg(II) rapid uptake and high catalytic activity of spent Hg(II) adsorbent.

Currently, magnetic mesoporous silica nanospheres have been employed widely as adsorbents due to their large surface area and easy recovery. Herein, the functionalized magnetic mesoporous silica/organic polymers nanocomposite (MMSP) was fabricated by the grafted poly(m-aminothiophenol) embedded the aminated magnetic mesoporous silica nanocomposite based on Fe3O4 magnetic core, which was shelled by mesoporous silica and further modified by (3-aminopropyl) triethoxysilane. The adsorption properties of as-developed MMSP were systematically explored by altering the experimental parameters. The results indicated that the adsorption capacity and removal percentage of the MMSP could reach 243.83 mg/g and 97.53% within only 10 min at pH 4.0, and the coexisting ions had no significant effect on the selective Hg(II) ions removal from aqueous solutions, meanwhile, the adsorbent recovered by a magnet still exhibited good adsorption performance after recycled 5 times. In addition, by analyzing experimental data, the adsorption process of Hg(II) ions belonged to spontaneous exothermic adsorption, and the possible adsorption mechanisms were proposed based on the pseudo-second-order model and Langmuir model. After adsorption study, the waste material adsorbed Hg(II) was developed as an efficient catalyst for transformation of phenylacetylene to acetophenone with yield of 97.06%. In this study, we designed an efficient and selective material for Hg(II) ions remove and provided a treatment of the post-adsorbed mercury adsorbent by converting the waste into an excellent catalyst, which reduced the economic and environmental impact from conventional adsorption techniques.

Enhanced Photocatalytic Fuel Denitrification over TiO2/α-Fe2O3 Nanocomposites under Visible Light Irradiation.

With increasingly stringent environmental regulations, the removal of nitrogen-containing compounds (NCCs) from gasoline fuel has become a more and more important research subject. In this work, we have successfully synthesized TiO2/α-Fe2O3 heterogeneous photocatalysts with different mass ratios of TiO2 vs. α-Fe2O3. Taking photocatalytic denitrification of typical alkali NCCs, pyridine, in gasoline fuel under visible light irradiation (λ ≥ 420 nm) as the model reaction, the TiO2/α-Fe2O3 hybrids have exhibited enhanced photocatalytic activity compared with pure TiO2 and α-Fe2O3, giving a pyridine removal ratio of ∼100% after irradiation for 240 min. The improved photocatalytic performance can be attributed to the integrative effect of the enhanced light absorption intensity and more efficient separation of photogenerated electron-hole pairs. Importantly, this type of heterogeneous photocatalysts can be easily separate in the reaction medium by an external magnetic field that is very important for industrial purpose. In addition, major reaction intermediates have been identified by the liquid chromatograph-mass spectrometer (HPLC-MS) and a tentative photocatalytic denitrification mechanism has been proposed.

Improving the hydrogen selectivity of graphene oxide membranes by reducing non-selective pores with intergrown ZIF-8 crystals.

We report the intergrowth of ZIF-8 crystals on ultrathin graphene oxide (GO) membranes, which helps to reduce the non-selective pores of pristine GO membranes leading to gas selectivities as high as 406, 155, and 335 for H2/CO2, H2/N2, and H2/CH4 mixtures, respectively.

Hydrothermal synthesis, crystal structure and photoluminescence of two homochiral zinc(II) coordination polymers.

Metal-organic frameworks (MOFs) have potentially useful applications and an intriguing variety of architectures and topologies. Two homochiral coordination polymers have been synthesized by the hydrothermal method, namely poly[(µ-N-benzyl-L-phenylalaninato-κ(4)O,O':O,N)(µ-formato-κ(2)O:O')zinc(II)], [Zn(C16H16NO2)(HCOO)]n, (1), and poly[(µ-N-benzyl-L-leucinato-κ(4)O,O':O,N)(µ-formato-κ(2)O:O')zinc(II)], [Zn(C13H18NO2)(HCOO)]n, (2), and studied by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy and fluorescence spectroscopy. Compounds (1) and (2) each have a two-dimensional layer structure, with the benzyl or isobutyl groups of the ligands directed towards the interlayer interface. Photoluminescence investigations show that both (1) and (2) display a strong emission in the blue region.

Synthesis, crystal structures and characterizations of two homochiral coordination polymers based on a chiral reduced Schiff base ligand.

Two homochiral coordination polymers based on a chiral reduced Schiff base ligand, namely poly[(µ5-4-{[(NR,1S)-(1-carboxylato-2-phenylethyl)amino]methyl}benzoato)zinc(II)], [Zn(C17H15NO4)]n, (1), and poly[(µ5-4-{[(NR,1S)-(1-carboxylato-2-phenylethyl)amino]methyl}benzoato)cobalt(II)], [Co(C17H15NO4)]n, (2), have been obtained by hydrothermal methods and studied by single-crystal X-ray diffraction, elemental analyses, powder X-ray diffraction, thermogravimetric analysis, IR spectroscopy and fluorescence spectroscopy. Compounds (1) and (2) are isostructural and crystallize in the P2(1)2(1)2(1) space group. Both display a three-dimensional network structure with a one-dimensional channel, with the benzyl group of the ligand directed towards the channel. An investigation of photoluminescence properties shows that compound (1) displays a strong emission in the purple region.

catena-Poly[bis{mu-dihydrogen [(5-carboxypentylimino)dimethylene]diphosphonato-kappa2O:O'}cadmium(II)].

The title compound, [Cd(C(8)H(18)NO(8)P(2))(2)](n), synthesized by hydrothermal methods, exhibits a layered structure in which the Cd(II) ion, occupying a centre of symmetry, is coordinated by six O atoms from four phosphonate ligands. The crosslinkage of CdO(6) octahedra by bridging phosphonate ligands results in a cadmium(II) phosphonate layer. Within the layer, there exists a 16-membered ring incorporating four -Cd-O-P-O- linkages. The uncoordinated carboxyl group of the ligand is oriented so that it penetrates the adjacent layer, taking part in hydrogen bonding to two uncoordinated phosphonate O atoms to form a CO(2)H/HO(2)P motif.

cis-Dichloridobis(1,10-phenanthroline)cobalt(II) dimethyl-formamide solvate.

In the title complex, [CoCl(2)(C(12)H(8)N(2))(2)]·C(3)H(7)NO, which has twofold rotation symmetry, the Co(II) cation is coordinated by two 1,10-phenanthroline (phen) mol-ecules and two chloride ligands in a distorted octa-hedral geometry. In the crystal structure, a cavity is created by six complex mol-ecules connected by C-H⋯π inter-actions and non-classical C-H⋯Cl hydrogen bonds. The cavities are occupied by the disordered dimethyl-formamide solvent mol-ecule. The C and N atoms of the C-N bond in the solvent mol-ecule also lie on a crystallographic twofold rotation axis; the remaining atoms of the solvent are statistically disordered (ratio 0.5:0.5) about this axis.

Diaqua-bis(5-carb-oxy-2-methyl-1H-imidazole-4-carboxyl-ato-κN,O)manganese(II).

The title complex, [Mn(C(6)H(5)N(2)O(4))(2)(H(2)O)(2)], was obtained by hydro-thermal synthesis. The Mn(II) atom, which lies on an inversion centre, displays a slightly distorted octa-hedral geometry. In the crystal packing, complex mol-ecules are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds to form a three-dimensional supramolecular structure. The title complex is isostructural with the corresponding cadmium(II) complex [Nie, Wen, Wu, Liu & Liu (2007 ▶). Acta Cryst. E63, m753-m755].