Electrodeposited PbO2 thin film on Ti electrode for application in hybrid supercapacitor

PbO₂ thin films were prepared by pulse current technique on Ti substrate from Pb(NO₃)₂ plating solution. The hybrid supercapacitor was designed with PbO₂ thin film as positive electrode and activated carbon (AC) as negative electrode in the 5.3 M H₂SO₄ solution. Its electrochemical properties were determined by cyclic voltammetry (CV), charge–discharge test and electrochemical impedance spectroscopy (EIS). The results revealed that the PbO₂/AC hybrid supercapacitor exhibited large specific capacitance, high-power and stable cycle performance. In the potential range of 0.8–1.8 V, the hybrid supercapacitor can deliver a specific capacitance of 71.5 F g^?1 at a discharge current density of 200 mA g^?1(4 mA cm^?2) when the mass ratio of AC to PbO₂ was three, and after 4500 deep cycles, the specific capacitance remains at 64.4 F g^?1, or 32.2 Wh Kg^?1 in specific energy, and the capacity only fades 10% from its initial value.     

A symmetric carbon/carbon supercapacitor operating at 1.6 V by using a neutral aqueous solution

A high voltage symmetric carbon/carbon supercapacitor was built using a Na₂SO₄ aqueous solution. This system exhibits an excellent cycle life during thousands of cycles up to voltage values as high as 1.6 V. Three-electrode investigations show a particularly high potential window, ΔE = 2 V, for the considered activated carbon in Na₂SO₄. However, in a two-electrode cell, when the voltage is higher than 1.6 V, the potential of the positive electrode is beyond the oxidation potential of water, and AC is oxidized. These results demonstrate the potentialities of Na₂SO₄ for developing high energy density systems.     

Synthesis and evaluation of two novel rhodamine-based fluorescence probes for specific recognition of Fec+ ion

Two low cytotoxic fluorescence probes Rb1 and Rb2 detecting Fe³⁺ were synthesized and evaluated. Rb1 and Rb2 exhibited an excellent selectivity to Fe³⁺, which was not disturbed by Ag⁺, Li⁺, K⁺, Na⁺, NH₄⁺, Fe²⁺, Pb²⁺, Ba²⁺, Cd²⁺, Ni²⁺, Co²⁺, Mn²⁺, Zn²⁺, Mg²⁺, Hg²⁺, Ca²⁺, Cu²⁺, Ce³⁺, AcO^?, Br^?, Cl^?, HPO₄^2?, HSO₃^?, I^?, NO₃^?, S₂O₃^2?, SO₃^2? and SO₄^2? ions. The detection limits were 1.87 × 10^?7 M for Rb1 and 5.60 × 10^?7 M for Rb2, respectively. 1:1 stoichiometry and 1:2 stoichiometry were the most likely recognition mode of Rb1 or Rb2 towards Fe³⁺, and the corresponding OFF–ON fluorescence mechanisms of Rb1 and Rb2 were proposed.     

Conformational and stereoelectronic investigation of chloromethyl methyl sulfide and its sulfinyl and sulfonyl analogs

Three compounds based on polyoxometalate building blocks, [Cu(en)₂]{[Cu(en)₂]₂[Mo^VI₅Mo^V₃V^IV₈O₄₀(PO₄)]} · 4H₂O (1), [Co(en)₂]{[Co(en)₂]₂[HMo^VI₄Mo^V₄V^IV₈O₄₀(PO₄)]} · 5H₂O (2) and [Ni(en)₂]{[Ni(en)₂]₂[Mo^VI₅Mo^V₃V^IV₈O₄₀(VO₄)]} · 2H₂O (3) (en = ethylenediamine), have been synthesized and characterized by elemental analysis, IR, XPS, XRD, TGA and single-crystal X-ray diffraction analysis. The result of structure determination shows that isomorphic compounds 1, 2 and 3 feature a one-dimensional chain built from the reduced tetra-capped pseudo-Keggin polyoxoanion, which is further interconnected by [M(en)₂]²⁺ (M = Cu, Co and Ni) groups via the terminal oxygen atoms of polyoxoanions. The crystal data for these compounds are the following: 1, monoclinic, space group C2/c, a = 26.702(3) Å, b = 13.4539(14) Å, c = 19.5987(19) Å, β = 108.650(2)°, V = 6671.0(12) Å³, Z = 4; 2, monoclinic, space group C2/c, a = 26.244(3) Å, b = 13.5070(17) Å, c = 19.581(3) Å, β = 106.881(2)°, V = 6641.8(15) Å³, Z = 4; 3, monoclinic, space group C2/c, a = 26.2789(15) Å, b = 13.5408(6) Å, c = 19.6312(9) Å, β = 106.2590(10)°, V = 6706.1(6) Å³, Z = 4. Variable-temperature magnetic susceptibility measurements of compounds 1 and 3 reveal the feature of antiferromagnetic exchange in these compounds.     

Flexible asymmetric supercapacitor based on MnO2 honeycomb structure

By controlling the electroplating time of solution containing Mn(Ac)₂, the MnO₂ nanosheets were self-assembled to the honeycomb structure and showed an excellent electrochemical performance in 1 mol/L Na₂SO₄ electrolyte. Via pairing with activated carbon as negative electrode, the capacitor could deliver a maximum energy density of 43.84 Wh/kg and a maximum power density of 6.62 kW/kg.     

Study on electrochemical performance of activated carbon in aqueous Li2SO4, Na2SO4 and K2SO4 electrolytes

The electrochemical performances of activated carbon (AC) in 0.5 mol/l Li₂SO₄, Na₂SO₄ and K₂SO₄ aqueous electrolytes were investigated. The cyclic voltammetric results at different scan rates show that the rate behaviors of AC in the three electrolytes improve in the order of Li₂SO₄ < Na₂SO₄ < K₂SO₄. This improvement can be mainly ascribed to the following two reasons: (1) the decreasing equivalent series resistance in the order of Li₂SO₄ > Na₂SO₄ > K₂SO₄, which is the main factor influencing the maximum output power, and (2) the increasing migration speed of hydrated ions in the bulk electrolyte and in the inner pores of AC electrode in the order of Li⁺ < Na⁺ < K⁺. Their cycling behaviors do not show any differences in capacitive fading. The above results provide valuable information to explore new hybrid supercapacitors.     

KOH activated carbon derived from biomass-banana fibers as an efficient negative electrode in high performance asymmetric supercapacitor

Here we demonstrate the fabrication, electrochemical performance and application of an asymmetric supercapacitor(AS) device constructed with β–Ni(OH)_2/MWCNTs as positive electrode and KOH activated honeycomb-like porous carbon(K-PC) derived from banana fibers as negative electrode. Initially,the electrochemical performance of hydrothermally synthesized β–Ni(OH)_2/MWCNTs nanocomposite and K-PC was studied in a three-electrode system using 1 M KOH. These materials exhibited a specific capacitance(Cs) of 1327 F/g and 324 F/g respectively at a scan rate of 10 m V/s. Further, the AS device i.e.,β–Ni(OH)_2/MWCNTs//K-PC in 1 M KOH solution, demonstrated a Cs of 156 F/g at scan rate of 10 m V/s in a broad cell voltage of 0–2.2 V. The device demonstrated a good rate capability by maintaining a Cs of 59 F/g even at high current density(25 A/g). The device also offered high energy density of 63 Wh/kg with maximum power density of 5.2 kW/kg. The AS device exhibited excellent cycle life with 100% capacitance retention at 5000 th cycle at a high current density of 25 A/g. Two AS devices connected in series were employed for powering a pair of LEDs of different colors and also a mini fan.     

Na4Mn9O18 as a positive electrode material for an aqueous electrolyte sodium-ion energy storage device

Here we demonstrate Na₄Mn₉O₁₈ as a sodium intercalation positive electrode material for an aqueous electrolyte energy storage device. A simple solid-state synthesis route was used to produce this material, which was then tested electrochemically in a 1 M Na₂SO₄ electrolyte against an activated carbon counter electrode using cyclic voltammetry and galvanostatic cycling. Optimized Na₄Mn₉O₁₈ was documented as having a specific capacity of 45 mAh/g through a voltage range of 0.5 V, or an equivalent specific capacitance of over 300 F/g. With the proper negative:positive electrode mass ratio, energy storage cells capable of being charged to at least 1.7 V without significant water electrolysis are documented. Cycling data and rate studies indicate promising performance for this unexplored low-cost positive electrode material.     

Design,synthesis and biological evaluation of quinazolin-4(3H)-one Schiff base conjugates as potential antiamoebic agents

In an effort to develop novel antiamoebic scaffolds having better efficacy than the standard drug metronidazole (IC₅₀ = 1.80 μM) used against Entamoeba histolytica, quinazolin-4(3H)-one Schiff base conjugates were synthesized and evaluated against HM1: IMSS strain of E. histolytica. Out of the thirteen compounds (S2-S14), six compounds (S2, S3, S4, S5, S6 and S11) were found to be better inhibitors than metronidazole and showed low cytotoxicity on HeLa cells, a cervical cancer cell line. The structure of intermediate compound S1 was confirmed by crystal structure studies.     

Synthesis and characterization of a tetranuclear copper(Ⅱ) complex with a chiral Schiff base ligand

The title complex l-[Cu^Ⅱ₄（Hvap）₂（vap）₂（MeOH）₂]（CIO₄）₂ 1 has been synthesized and characterized by EA. IR,TGA,solid-state CD spectra and X-ray single-crystal analyses（l-H₂vap’.a Schiff base ligand derived from the condensation of o-vanillin and l-2-amino-3-phenyl-l-propanol）.Complex 1 crystallizes in monoclinic system,chiral space group P2₁ with a =10.4257（18）.b = 21.695（4）,c = 15.721（3）A,β= 94.443（3）.V= 3545.1（11） ³,Z=2,Cu₄C₇₀H₇₈N₄O₂₂Cl₂.Mr= 1652.42,D_c= 1.548 g/cm³, F（000）= 1704 andμ（MoKα） = 1.338 mm^-1.The final R = 0.0682 and wR = 0.1420 for 6170 observed reflections with I > 2σ（I） and R = 0.1775 and wR = 0.1830 for all data.The structure of complex 1 contains a boat-shaped(Cu₄O₄} motif.The solid-state CD spectra confirm the chiral nature of complex 1.     

Enhanced supercapacitive behaviors of birnessite

The birnessite type manganese dioxide electrode was prepared by the electrochemical stimulation as we recently described. It showed 190 F g⁻¹ in a Na₂SO₄ aqueous solution between −0.1 and 0.9 V versus Ag/AgCl at 1 A g⁻¹. The specific capacitance of birnessite was decreased by the manganese dissolution when the reduction and oxidation were repeated. By adding small amounts of Na₂HPO₄ or NaHCO₃ into the electrolyte, the capacitance increased to 200–230 F g⁻¹ and the manganese dissolution was successfully suppressed. Thanks to the additives, the birnessite demonstrated the much improved cycleability over >1800 cycles.     

Preface

The anisotropic rototranslational scattering spectra of nitrogen gas at high frequency up to 700 cm⁻¹ for several temperatures and from low densities are analyzed in terms of new site–site (M3SV) intermolecular potential and interaction-induced pair polarizability models, using quantum spectral shapes computations. Our theoretical calculations take into account multipole contributions from the mean value and anisotropy of the dipole–dipole polarizability tensor α, two independent components of the dipole–octopole polarizability tensor E and dipole–dipole–quadrupole hyperpolarizability tensor B. The high-frequency wings are discussed in terms of the collision-induced rotational Rayleigh effect and estimates for the dipole–octopole polarizability |E₄| are obtained and checked with recent ab initio theoretical value. Good comparison is found in the frequency range 0–400 cm⁻¹ between the theoretical and experimental spectra. When an exponential contribution [exp(−ν/ν₀)] with ν₀ = 425 cm⁻¹ is considered to model very short-range light scattering mechanisms at room temperature, good agreement is found over the whole frequency range.     

NiCo_2O_4 decorated PANI–CNTs composites as supercapacitive electrode materials

Hierarchical Ni Co_2O_4/PANI/CNTs hybrid composites were designed and fabricated having a layer of Ni Co_2O_4 on the surface of PANI encapsulated CNTs with different morphologies. Physicochemical attributes of the synthesized composites were examined by FTIR, UV–visible and X-ray diffraction(XRD)techniques. Morphological aspects were evaluated by field-emission scanning microscopy(FESEM),electron diffraction spectroscopy(EDS), high resolution transmission electron microscopy(HRTEM) and selected area electron diffraction(SAED) studies. Electrochemical measurements revealed an improved specific capacitance of 2250 F/g at a scan rate of 5 m V/s and 2000 F/g at a current density of 1 A/g with good rate capability using a three-electrode system. These enhanced features are achieved from the well designed nanostructure and the synergistic contributions of individual components in the electrode material.     

Electrochemical characterization on cobalt sulfide for electrochemical supercapacitors

High capacitance at a high charge–discharge current density of 50 mA/cm² for a new type of electrochemical supercapacitor cobalt sulfide (CoS_x) have been studied for the first time. The CoS_x was prepared by a very simply chemical precipitation method. The electrochemical capacitance performance of this compound was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests with a three-electrode system. The results show that CoS_x has excellent electrochemical capacitive characteristic with potential range −0.3 ∼ 0.35 V (versus SCE) in 6 M KOH solution. Charge–discharge behaviors have been observed with the highest specific capacitance values of 475 F/g at the current density of 5 mA/cm², even at the high current density of 50 mA/cm², CoS_x also shows the high specific capacitance values of 369 F/g.     

High-throughput investigation and characterization of strontium-phosphonatoethanesulfonates

Using the polyfunctional ligand 2-phosphonethanesulfonic acid (H₃L) a high-throughput (HT) study was started for the systematic investigation of the system SrCl₂/H₃L/NaOH/H₂O. The HT experiment comprising 48 individual reactions were performed to systematically investigate the influence of pH of the starting mixture as well as the molar ratio Sr²⁺:H₃L. Two new compounds SrH(O₃P–C₂H₄–SO₃) (1) and Sr₃(O₃P–C₂H₄–SO₃)₂(H₂O)₂ (2) were obtained and structurally characterized by single-crystal X-ray diffraction. The reaction products synthesized under hydrothermal conditions always contain traces of SrSO₄, which are due to the decomposition of small amounts of the ligand. While compound 2 could only be obtained under hydrothermal conditions, the synthesis of 1 could be accomplished under milder reaction conditions and a reaction scale-up could be performed. Compound 1 crystallizes in a monoclinic system with space group C2/c (no. 15), a = 534.73(11) pm, b = 1648.7(3) pm, c = 825.43(17) pm, β = 105.34(3)°, V = 701.8(2)–10⁶ pm³, Z = 4, R1 = 0.0268, and wR₂ = 0.0642 for I > 2σ(I). Compound 2 crystallizes in a triclinic system with space group P-1 (no. 2), a = 700.97(14) pm, b = 1008.5(2) pm, c = 1274.8(3) pm, α = 97.63(3)°, β = 92.03(3)°, γ = 92.03(3)°, V = 843.7(3)–10⁶ pm³, Z = 2, R1 = 0.0360, and wR₂ = 0.0896 for I > 2σ(I). In the structure of compound 1 the phosphorous and sulfur atoms cannot be distinguished due to identical crystallographic positions. Thus, an averaged structure was obtained which is built up by edge-sharing SrO₈ polyhedra that form infinite M–O–M chains. Compound 2 contains corner-, edge-, and face-sharing SrO₈ polyhedra which form inorganic M–O–M layers. These M–O–M chains (1) and layers (2) are connected to a three-dimensional network by the –CH₂CH₂– group of the ligand, respectively. Additional characterization by thermogravimetric analysis and IR-spectroscopy for compound 1 is also presented.     

MnO2 multilayer nanosheet clusters evolved from monolayer nanosheets and their predominant electrochemical properties

MnO₂ multilayer nanosheet clusters were prepared via electrochemical deposition route, which shows simpleness and high efficiency. The growth process of MnO₂ multilayer nanosheet clusters was investigated in this paper. The deposited MnO₂ films were characterized by XRD, SEM, TEM, and XPS. In addition, it was also electrochemically characterized by cyclic voltammetry in 1.0 M Na₂SO₄ electrolyte. The MnO₂ multilayer nanosheet clusters show a big specific capacitance, and it can be achieved about 521.5 F g^?1 at 5 mV s^?1. These materials also have a high electrochemical stability.     

Anthroneamine based chromofluorogenic probes for Hg2+ detection in aqueous solution

Anthroneamine derivatives 1–3 (H₂O:DMSO; 9:1, HEPES buffer, pH 7.0 ± 0.1) undergo highly selective fluorescence quenching with Hg²⁺. The observed linear fluorescence intensity change allows the quantitative detection of Hg²⁺ between 200 nM/40 ppb—12 μM/2.4 ppm even in the presence of interfering metal ions viz. Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Cr³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Pb²⁺. Probes 1–3 and their Hg²⁺ complexes also show the broad pH resistance for their practical applicability.     

Synthesis of an antimetastatic tetrasaccharide β-D-Gal-(1→4)-β-d-GlcpNAc-(1→6)-α-D-Manp-(1→6)-β-D-Manp-OMe

An antimetastatic tetrasaccharide T₁,β-D-Gal-（1→4）-β-D-GlcpNAc-（1→6）-α-D-Manp-（1→6）-β-D-Manp-OMe,was synthesized with two approaches.The first approach was a conventional method employing thioglycoside and Koenigs-Knorr glycosylation reaction in 24%overall yield.The second one was a novel route through the azidoiodo-glycosylation strategy by using 2-iodo-2-deoxylactosyl azide as the donor in 36%overall yield.     

Controlled synthesis of MnSn(OH)6/graphene nanocomposites and their electrochemical properties as capacitive materials

We report the synthesis of novel MnSn(OH)₆/graphene nanocomposites produced by a co-precipitation method and their potential application for electrochemical energy storage. The hydroxide decorated graphene nanocomposites display better performance over pure MnSn(OH)₆ nanoparticles because the graphene sheets act as conductive bridges improving the ionic and electronic transport. The crystallinity of MnSn(OH)₆ nanoparticles deposited on the surface of graphene sheets also impacts the capacitive properties as electrodes. The maximum capacitance of 31.2 F/g (59.4 F/g based on the mass of MnSn(OH)₆ nanoparticles) was achieved for the sample with a low degree of crystallinity. No significant degradation of capacitance occurred after 500 cycles at a current density of 1.5 A/g in 1 M Na₂SO₄ aqueous solution, indicating an excellent electrochemical stability. The results serve as an example demonstrating the potential of integrating highly conductive graphene networks into binary metal hydroxide in improving the performance of active electrode materials for electrochemical energy storage applications.     

Synthesis and crystal structure of a new water-soluble sulfur-containing palladacyclic diaqua complex

A new water-soluble sulfur-containing palladacyclic diaqua complex [(SC)Pd^II(H₂O)₂]₂(SO₄) {[1]₂(SO₄), SC = C₆H₄-2-(CH₂S^tBu)} was synthesized from a reaction of Ag₂SO₄ with a water-insoluble palladacyclic dichloro complex [(SC)Pd^II(μ-Cl)]₂ (2) in water. Water-solubility of [1]₂(SO₄) at pH 7 at 25 °C is 9.4 mg/mL. NH₄PF₆ was added to the solution of [1]₂(SO₄) in water to give [1](PF₆). The structures of [1](PF₆) and 2 were unequivocally determined by X-ray analysis.