Stabilizing Layered Structure in Aqueous Electrolyte via Dynamic Water Intercalation/Deintercalation.

Aqueous lithium-ion batteries (ALIBs) with nonflammable feature attract great attention for large-scale energy storage. However, the layered cathode materials (such as LiCoO2 ) present serious capacity decay in ALIBs. The degradation mechanism of layered cathode materials in ALIBs is still not clear and an effective strategy to improve cycling stability remains a great challenge. In this work, the authors use LiCoO2 as a typical example to investigate its structural degradation in aqueous electrolytes. It is found that H+ insertion accelerated irreversible layered-to-spinel phase transition is the main reason causing structural degradation and fast capacity fading in LiCoO2 . Subsequently, Li-excess Li1+ t Co1- t O2- t with intermediate spin Co3+ is developed to mitigate H+ influence and the adverse phase transition in aqueous electrolyte. It is interesting to discover that reversible water intercalation/deintercalation occurs in the layered structure during charge/discharge, which effectively suppresses the layered-to-spinel phase transition with cycling. Benefiting from the stabilized layered structure, the Li-excess Li1.08 Co0.92 O1.92 shows a significantly improved cycling performance in the neutral aqueous electrolyte with a large specific capacity and excellent rate capability. This work provides a promising structural regulation strategy for the layered cathode materials, enabling their potential application in ALIBs.

Strong Chemical Interaction between Lithium Polysulfides and Flame-Retardant Polyphosphazene for Lithium-Sulfur Batteries with Enhanced Safety and Electrochemical Performance.

The shuttle effect of lithium polysulfides (LiPS) and potential safety hazard caused by the burning of flammable organic electrolytes, sulfur cathode, and lithium anode seriously limit the practical application of lithium-sulfur (Li-S) batteries. Here, a flame-retardant polyphosphazene (PPZ) covalently modified holey graphene/carbonized cellulose paper is reported as a multifunctional interlayer in Li-S batteries. During the discharge/charge process, once the LiPS are generated, the as-obtained flame-retardant interlayer traps them immediately through the nucleophilic substitution reaction between PPZ and LiPS, effectively inhibiting the shuttling effect of LiPS to enhance the cycle stability of Li-S batteries. Meanwhile, this strong chemical interaction increases the diffusion coefficient for lithium ions, accelerating the lithiation reaction with complete inversion. Moreover, the as-obtained interlayer can be used as a fresh 3D current collector to establish a flame-retardant "vice-electrode," which can trap dissolved sulfur and absorb a large amount of electrolyte, prominently bringing down the flammability of the sulfur cathode and electrolyte to improve the safety of Li-S batteries. This work provides a viable strategy for using PPZ-based materials as strong chemical scavengers for LiPS and a flame-retardant interlayer toward next-generation Li-S batteries with enhanced safety and electrochemical performance.

A completely controlled sphere-to-bilayer micellar transition: the molecular mechanism and application on the growth of nanosheets.

The combination of a simple modification of the sample addition method to generate a sort of continuously accumulated external stimulation with only minute increments in amplitude and the introduction of probe molecules (herein aniline) within the micelle allow the direct continuous in situ spectroscopic monitoring of possible micellar transitions. In this way, a sphere-to-ellipsoid and further an ellipsoid-to-bilayer micellar transition of sodium dodecyl sulfate (SDS) induced by camphor sulfuric acid (CSA) is observed to experience four stages in the time sequence: (i) the accumulated protons released from CSA in the hydration layer of the micelle stimulate the rearrangement of SDS micelles; (ii) the micelles transform into ellipsoidal shapes as evidenced by the characteristic chemical shift anisotropy and the corresponding molecular dynamic properties from probe molecules; (iii) further protonation of aniline induces the micelle to turn into lamellar structures; (iv) aniline is freed from the micelle while leaving the SDS bilayers undistorted. Moreover, polyaniline nanosheets incorporating SDS bilayers in sandwich structures, which can display excellent capacitive behavior at relatively high current densities for the fabricated supercapacitors, are prepared from the aniline oriented by the bending energy of the SDS bilayers.

Aerobic granulation strategy for bioaugmentation of a sequencing batch reactor (SBR) treating high strength pyridine wastewater.

Aerobic granules were successfully cultivated in a sequencing batch reactor (SBR), using a single bacterial strain Rhizobium sp. NJUST18 as the inoculum. NJUST18 presented as both a good pyridine degrader and an efficient autoaggregator. Stable granules with diameter of 0.5-1 mm, sludge volume index of 25.6 ± 3.6 mL g(-1) and settling velocity of 37.2 ± 2.7 m h(-1), were formed in SBR following 120-day cultivation. These granules exhibited excellent pyridine degradation performance, with maximum volumetric degradation rate (Vmax) varied between 1164.5 mg L(-1) h(-1) and 1867.4 mg L(-1) h(-1). High-throughput sequencing analysis exhibited a large shift in microbial community structure, since the SBR was operated under open condition. Paracoccus and Comamonas were found to be the most predominant species in the aerobic granule system after the system had stabilized. The initially inoculated Rhizobium sp. lost its dominance during aerobic granulation. However, the inoculation of Rhizobium sp. played a key role in the start-up process of this bioaugmentation system. This study demonstrated that, in addition to the hydraulic selection pressure during settling and effluent discharge, the selection of aggregating bacterial inocula is equally important for the formation of the aerobic granule.

Preparation of silver colloids with improved uniformity and stable surface-enhanced Raman scattering.

Silver colloids of uniform shape and size are prepared by a two-step reduction. Small silver particles form initially by the rapid reduction of silver nitrate with sodium citrate at 100°C and then grow at 92°C. The reaction processes and resulting silver colloids are characterized by transmission electron microscopy, ultraviolet-visible absorption spectrophotometry, zeta-potential measurements, and Ag(+) concentration analysis. The surface-enhanced Raman scattering (SERS) activity of the silver colloids is then investigated, using crystal violet (CV) as a SERS probe. The silver colloids exhibit uniform shape and size and stable SERS activity. The average size of the silver particles is 47 nm (14% relative standard deviation), while the average sizes of the silver colloids prepared at 100°C and 92°C are 41 (30%) and 71 nm (33%), respectively.

Nucleation of polyaniline nano-/macrotubes from anilinium composed micelles.

A mechanistic study on the nucleation of polyaniline nanotubes (PANI-NT) through template-free method is explored by in situ solution-state (1)H NMR experiments via a careful analysis of the spectral evolution of the major species in the course of the reaction. Before polymerization, aniline and salicylic acid have assembled into loosely packed micelles due to electrostatic interactions and the proton exchange reaction between aniline and anilinium. A three-stage polymerization with a formation, accumulation of aniline dimers, as well as a generation of phenazine-like oligomers is observed, which can be attributed to the monomer transformation from neutral aniline molecules to anilinium cations and the significantly lowered pH in the reaction. Strong π-π stacking interactions from the phenazine-like oligomers facilitate the intermolecular aggregation which initiates the formation of PANI-NT. At first, such aggregates, locating at the outermost layer of anilinium composed micelles, shield in situ formed protons from releasing into the aqueous bulk but into the micelle instead. Due to the continuously increased charge in the micelle, a sphere-to-rod structural transition occurs which leads the oligomer aggregates to be sheathed at the exterior of the rod. Further consumption of anilinium in the micelle leaves the internal cavity while the fusion between the micelles elongates the length of the tubes. Our work demonstrates that (i) loosely packed anilinium composed micelles, highly mobile monomers within the micelle, and efficient blockage of the proton-releasing to the aqueous bulk are three key factors for the generation of tubular structures; and (ii) dynamic NMR line shape analysis provides a new perspective for resolving the formation profile of nanostructured polymers.

Nano or micro? A mechanism on thermal decomposition of ammonium perchlorate catalyzed by cobalt oxalate.

Micrometer-sized cobalt oxalates with different morphologies have been prepared in the presence of surfactants. The effect of catalysts morphology on the thermal decomposition of ammonium perchlorate (AP) was evaluated by differential thermal analysis (DSC). Remarkably, contrary to the well-accepted concepts, no direct relationship between the morphologies of catalysts and their activities has been observed. Based on the structural and morphological variation of the catalysts during the reaction, a catalytic mechanism on thermal decomposition of ammonium perchlorate catalyzed by cobalt oxalate is proposed. We believe that it is the "self-crushing and self-distributed" occurred within the reaction that really works for the improvement of the overall catalytic activities. In this process, both catalysts and reactants have been crashed and distributed uniformly in an automatic way. This work provides an in-depth insight into the thermal decomposition mechanism of AP as catalyzed by oxalates.

Synthesis, vibrational spectral and nonlinear optical studies of N-(4-hydroxy-phenyl)-2-hydroxybenzaldehyde-imine: a combined experimental and theoretical investigation.

The study of imine-bridged organics has been the one hot spot of photo-responsive material sciences in recent years. Herein we make a study of the synthesis, characteristics and potential application of N-(4-hydroxy-phenyl)-2-hydroxy-benzaldehyde-imine (HPHBI), C13H11NO2. The studied compound was synthesized in one step by the condensation reaction of salicylaldehyde and 4-aminophenol in methanol solution, and characterized by single crystal X-ray diffraction, FT-IR and FT-Raman techniques with theoretical calculations at B3LYP/6-31G(d) level. The molecule adopts trans configuration about central CN bond with intramolecular hydrogen bonding, and the adjacent molecules form wave-shaped structure linked by strong intermolecular hydrogen bonding mechanism along b axis. The vibrational spectra have been precisely assigned with the aid of theoretical frequencies. Furthermore, the thermodynamic properties have been obtained by the theoretical vibrational analysis for HPHBI. The total linear polarizability and first-order hyperpolarizabilities calculated on the studied compound respectively present 25.378 Å3 and 1.655×10(-29) cm5/esu, which indicates the compound has relatively good nonlinear optical property.

[Preparation and spectral characterisation of TiO2/polyaniline nanocomposites with 2D lamellar morphology].

Nanostructured polyanilines (PANIs) are selected quite often as the matrix for the synthesis of inorganic/conductive polymer composites due to their excellent optical, electrical and magnetic properties. Herein both 2D lamellar PANI and the cor responding composite loading TiO2 species were successfully prepared from a microemulsion system, as composed by dodecyl benzenesulfonic acid (DBSA) and water. The composite was achieved through a simultaneous polymerization of aniline in the presence of ammonium persulfate and hydrolysis of tetrabutyl titanate. Scanning electron microscopy (SEM) images indicate clearly that 2D PANI lamella are formed through organization of small PANI sheets. The inter-lamellar distance of PANI and that of TiO2/polyaniline composite, as derived from X-ray diffraction (XRD), is about 3.4 nm (nearly twice the length of one DBS molecule), suggesting that PANI and double-layered DBSA species are arranged in an alternated way. FTIR spectrum displays that PANI chains exhibit quinonoid and benzenoid strutures while both Raman and X-ray photoelectron spectroscopy (XPS) indicate that rutile TiO2 is produced upon hydrolyzation of tetrabutyl titanate in the microemulsion system. Moreover, UV-Vis spectrum suggests that the electronic absorption behaviour of PANI species is influenced upon loading TiO2.

[Spectroscopic analysis studies of organo-attapulgite/nylon 6 composites].

The surface organic modification of attapulgite with silane coupling reagent was studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Qrgano-attapulgite/nylon 6 composites with different content of attapulgite were prepared by means of melt blending, and the crystal structure and morphology were investigated. The results show that the surface content of Si, N and C of the modified attapulgite increased. Combined with the FTIR results, it was confirmed that an organic coating layer was formed on the surface of attapulgite. The adding of attapulgite does not change the crystal structure of nylon 6, but changes the crystallite size of nylon 6. The modified attapulgite was well dispersed in nylon 6 and the silane coupling coating on the attapilgite enhanced the interfacial adhesion.

A nanostructured graphene/polyaniline hybrid material for supercapacitors.

A flexible graphene/polyaniline hybrid material as a supercapacitor electrode was synthesized by an in situ polymerization-reduction/dedoping-redoping process. This product was first prepared in an ethylene glycol medium, then treated with hot sodium hydroxide solution to obtain the reduced graphene oxide/polyaniline hybrid material. Sodium hydroxide also acted as a dedoping reagent for polyaniline in the composite. After redoping in an acidic solution, the thin, uniform and flexible conducting graphene/polyaniline product was obtained with unchanged morphology. The chemical structure of the materials was characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. The composite material showed better electrochemical performances than the pure individual components. A high specific capacitance of 1126 F g(-1) was obtained with a retention life of 84% after 1000 cycles for supercapacitors. The energy density and power density were also better than those of pure component materials.

[Preparation of microencapsulated red phosphorus and its flame-retardant application in PP composites].

In the present study, the melamine-formaldehyde prepolymer (MFP) was first synthesized at pH 8-8.5 under about 80 degrees C with melamine, formaldehyde, triethanolamine and methanol as the starting materials. Subsequently, the microencapsulated red phosphorus (MRP) was successfully prepared by in-situ polymerization at pH 5.5 under 65 degrees C, using MFP and red phosphorus (RP) powders as raw materials, and potassium persulphate (KPS) as catalyst. The obtained products were detected by differential scan calorimetry (DSC), scanning electron microscope (SEM), Fourier transform infrared (FTIR) and X-ray photo-electron spectroscopy (XPS). It was found that KPS is useful in enhancing the reaction activity of MFP, which can make RP be well encapsulated by melamine-formaldehyde resin (MF) and reduce the reaction time. The DSC, SEM and XPS results show that it won't get well-encapsulated MRP only under acidic condition and without any KPS. When a proper quantity of KPS is employed, the RP particles can be almost completely-encapsulated by MF and the peak temperature of oxidation reaction for MRP is 480 degrees C, which is much higher than that of RP, extending the applications for MRP. The FTIR spectrum demonstrates that the coating material on the surface of RP accurately is MF, in agreement with the reference. Polyproplene (PP) composites with different formulations were prepared by melt extrusion. It was shown that the flame-retardant efficiencies are very low when the PP composites only contain MRP or MH. However, the flame-retardant property can obviously improve if MRP and MH are both used in the PP composites. When PP : MRP: MH = 100 (phr) : 15 (phr) : 50 (phr), the limited oxygen index of the MRP/MH/PP composite is 26%, and vertical firing ranks UL-94 V-0. In addition, the possible flame-retardant mechanism of the PP composites has also been discussed, and further verified by FTIR and Raman spectroscopy.

Effect of graphene oxide on the properties of its composite with polyaniline.

Graphene oxide, a single layer of graphite oxide (GO), has been used to prepare graphene oxide/polyaniline (PANI) composite with improved electrochemical performance as supercapacitor electrode by in situ polymerization using a mild oxidant. The composites are synthesized under different mass ratios, using graphite as start material with two sizes: 12 500 and 500 mesh. The result shows that the morphology of the prepared composites is influenced dramatically by the different mass ratios. The composites are proposed to be combined through electrostatic interaction (doping process), hydrogen bonding, and pi-pi stacking interaction. The highest initial specific capacitances of 746 F g(-1) (12 500 mesh) and 627 F g(-1) (500 mesh) corresponding to the mass ratios 1:200 and 1:50 (graphene oxide/aniline) are obtained, compared to PANI of 216 F g(-1) at 200 mA g(-1) by charge-discharge analysis between 0.0 and 0.4 V. The improved capacitance retention of 73% (12 500 mesh) and 64% (500 mesh) after 500 cycles is obtained for the mass ratios 1:23 and 1:19 compared to PANI of 20%. The enhanced specific capacitance and cycling life implies a synergistic effect between two components. This study is of significance for developing new doped PANI materials for supercapacitors.

4,4'-[(2,7-Dibromo-fluorene-9,9-di-yl)dimethyl-ene]dipyridinium bis-(perchlorate).

In the crystal of the title compound, C(25)H(20)Br(2)N(2) (2+)·2ClO(4) (-), inter-molecular N-H⋯O and C-H⋯O hydrogen bonds, along with C-H⋯π inter-actions, stabilize the crystal structure.

Vibrational spectroscopic study of o-, m- and p-hydroxybenzylideneaminoantipyrines.

Three structurally similar antipyrine derivatives of o-hydroxybenzylideneaminoantipyrine (o-HBAP), m-hydroxybenzylideneaminoantipyrine (m-HBAP) and p-hydroxybenzylideneaminoantipyrine (p-HBAP) were characterized by FT-IR, FT-Raman experimental techniques and density functional theoretical (DFT) calculations. The comparisons between the calculated and experimental results covering molecular structures, assignments of fundamental vibrational modes and thermodynamic properties were investigated. The optimized molecular geometries agree well with the corresponding experimental values by comparing with the XRD data. The comparisons and assignments of the vibrational frequencies indicate that the experimental spectra also coincide satisfactorily with those of theoretically simulated spectrograms except the hydrogen-bond coupling infrared vibrations, and compounds can be distinguished by the IR and Raman spectra due to the differences of the hydroxyl-substituted positions and molecular packing, and the strong Raman scattering activities of the compounds are tightly relative to the molecular conjugative moieties linked through the Schiff base imines. The thermodynamic functions and their correlations with temperatures were also obtained from the theoretical harmonic frequencies.

Hydrogen-bond-directed supramolecular arrays in 4,4'-bipyridinium tetrachloroterephthalate dihydrate and bis(1,10-phenanthrolinium) tetrachloroterephthalate tetrachloroterephthalic acid trihydrate.

The title compounds, C10H10N(2)(2+).C8Cl4O(4)(2-).2H2O, (I), and 2C12H9N2+.C8Cl4O(4)(2-).C8H2Cl4O4.3H2O, (II), both crystallize as charge-transfer organic salts with the dianionic or neutral acid components lying on inversion centres. The acid and base subunits in (I) arrange alternately to generate a linear tape motif via N-H...O hydrogen bonds; these tapes are further combined into a three-dimensional architecture through multiple O-H...O and C-H...O interactions involving solvent water molecules. In contrast, the neutral and anionic acid components in (II) are linked to form a zigzag chain by means of O-H...O hydrogen bonds between acid groups, with dangling 1,10-phenanthrolinium units connected to these chains by carboxylate-pyridinium interactions with R(2)(2)(7) hydrogen-bond notation. Adjacent chains are further extended to result in a two-dimensional corrugated layer network via pi-pi interactions. Inter-ion Cl...O interactions are also found in both (I) and (II).

Molecular mechanism for formation of polyaniline lamella from a lyotropic liquid crystal: an NMR study.

Polyaniline (PANI) microlamellas with an average interlamellar distance of 2.6 nm were prepared from a nematic lyotropic liquid crystal system composed by sodium dodecyl sulfate (SDS) aqueous solution. To reveal the formation mechanism of these lamellas, a series of NMR studies have been performed. At first, variable-temperature (VT) 13C NMR experiments have suggested that, prior to polymerization, anilines are predominantly located in the vicinity of the SDS polar head region with a limited mobility at low temperature, whereas they become more mobile and penetrate into the SDS hydrophobic domain at elevated temperature. Subsequent in situ 13C NMR measurements at 310 K have indicated that the overall polymerization can be taken place in two stages. In the beginning, the reaction sites are within the SDS micelles, resulting in the formation of oligomeric PANI species with benzenoid and quinoid structures. Interestingly, these oligomeric species fall off from the micellar hydrophobic domains and reorganize into layered structures with the support of SDS. In the second stage, further polymerization can be continued within the interlayers. This paper provides a good example in studying the roles of surfactants at the nucleation stage qualitatively during the synthesis of morphology-specific polymers with the application of NMR techniques, a period difficult to be examined by other approaches currently.

Experimental and theoretical studies on 4-(2,4-dichlorobenzylideneamino)antipyrine and 4-(2,6-dichlorobenzylideneamino)antipyrine.

Two antipyrine derivates, with the same formula C(18)H(15)Cl(2)N(3)O, are structurally similar Schiff bases derived from the condensation of 2,4-dichlorobenzaldehyde or 2,6-dichlorobenzaldehyde and 4-aminoantipyrine in methanol solutions. The compounds were characterized by elemental analysis, FT-IR, FT-Raman and UV-vis techniques. Density functional calculations were performed to further optimize and characterize them. The calculated results indicate that the theoretical values show good agreements with experimental ones. They are similar in their IR spectra and different in their Raman spectra. The detailed vibrational and UV-vis absorption spectra of the compounds have been ascribed to their corresponding molecular structures and electrons orbital transitions. The statistical thermodynamic functions and their correlations with temperatures of the title compounds have been obtained from their theoretical vibrations of the optimized structures. The nonlinear optical and UV-vis properties indicate that the compounds are the promising photoelectronic materials.

Experimental and theoretical studies on vibrational spectra of 4-(2-furanylmethyleneamino)antipyrine, 4-benzylideneaminoantipyrine and 4-cinnamilideneaminoantipyrine.

This work deals with the IR and Raman spectroscopy of 4-(2-furanylmethyleneamino) antipyrine (FAP), 4-benzylideneaminoantipyrine (BAP) and 4-cinnamilideneaminoantipyrine (CAP) by means of experimental and quantum chemical calculations. The equilibrium geometries, harmonic frequencies, infrared intensities and Raman scattering activities were calculated by density functional B3LYP method with the 6-31G(d) basis set. The comparisons between the calculated and experimental results covering molecular structures, assignments of fundamental vibrational modes and thermodynamic properties were investigated. The optimized molecular geometries have been compared with the experimental data obtained from XRD data, which indicates that the theoretical results agree well with the corresponding experimental values. For the three compounds, comparisons and assignments of the vibrational frequencies indicate that the calculated frequencies are close to the experimental data, and the IR spectra are comparable with some slight differences, whereas the Raman spectra are different clearly and the strongest Raman scattering actives are relative tightly to the molecular conjugative moieties linked through their Schiff base imines. The thermodynamic properties (heat capacities, entropies and enthalpy changes) and their correlations with temperatures were also obtained from the harmonic frequencies of the optimized structures.

[Study on the preparation and spectral characteristics of Bi2S3 nanoribbons].

In the present study, bismuth sulfide (Bi2S3) nanoribbons were prepared by the hydrothermal method using bismuth nitrate (Bi(NO3)3 x 5H2O), thioacetamide (C2H5NS) and nitrilotriacetic acid (C6H9NO6) as raw materials at 180 degrees C for 12 h. The reaction time was largely reduced and the route has been unreported. The constituent, structure and morphology of the products were characterized by XRD, XPS and TEM, respectively. The powder X-ray diffraction (XRD) pattern shows that the Bi2S3 crystals belong to the orthorhombic phase (JCPDS:17-320) with calculated lattice constants a = 1.1106 nm, b = 1.0993 nm and c = 0.3892 nm, which are consistent with the reported values (a = 1.1149 nm, b = 1.1304 nm and c = 0.3981 nm). Transmission electron microscopic (TEM) studies reveal that the appearance of as-prepared Bi2S3 is nanoribbon-like with the typical width of about 100 nm; and the high-resolution transmission electron microscope (HRTEM) image shows that the crystal grows along the y axis. The quantification of X-ray photoelectron spectra (XPS) analysis peaks gives an atomic ratio of 2 : 3 for Bi : S, which is consistent with the given formula of Bi2S3. Furthermore, the Raman and UV-Vis spectra of the product were also studied. Compared with bulk Bi2S3 (236 cm(-1)), the Raman absorption band of the Bi2S3 nanoribbons (195 cm(-1)) red-shifts 41 cm(-1), which is because of the surface effect of nanomaterials. Furthermore, the product has absorption at the wavelength of about 450 nm in the UV-Vis region. The direct bang gap energy (Eg) was estimated to be about 1.58 eV(Eg of the bulk Bi2S3 is 1.3 eV), which indicates that the product has potential application in the optical and electrical areas.