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1.
In this study, Co3O4/SiO2 nanocomposites have been successfully synthesized by citrate–gel method by utilizing SiO2 matrix for Co3O4 embedment. Spectroscopy analyses confirm the formation of high crystalline Co3O4 nanoparticles; meanwhile, microscopy findings reveal that the Co3O4 nanoparticles are embedded in SiO2 matrix. Electrochemical properties of the Co3O4/SiO2 nanocomposites were carried out using cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) in 5 M KOH electrolyte. The findings show that the charge storage of Co3O4/SiO2 nanocomposites is mainly due to the reversible redox reaction (pseudocapacitance). The highest specific capacitance of 1,143 F g ?1 could be achieved at a scan rate of 2.5 mV s?1 in the potential region between 0 and 0.6 V. Furthermore, high-capacitance retention (>92 %) after 900 continuous charge–discharge tests reveals the excellent stability of the nanocomposites. It is worth noting from the EIS measurements that the nanocomposites have low ESR value of 0.33 Ω. The results manifest that Co3O4/SiO2 nanocomposites are the promising electrode material for supercapacitor application.  相似文献   

2.
The graphite oxide (GO) was prepared from expandable graphite by the pressurized oxidation method, and samples were characterized using XRD, UV–Vis, and TEM. GO is reduced in situ emulsion using hydrazine to achieve reduced graphene oxide/waterborne polyurethane (rGO/WPU) nanocomposites. The effect of rGO content on the stability, fracture morphologies, mechanical performance, thermal degradation, and flame-retardant properties of rGO/WPU composites was investigated by zeta potential analyzer, TEM, SEM, universal testing machine, TG, and Cone Calorimeter. The results of zeta potential, TEM, and SEM analysis indicate that rGO has a good stability and dispersibility in rGO/WPU nanocomposites. The results of mechanical tests showed that the mechanical properties of rGO/WPU nanocomposites increased consistently with increasing rGO content up to 2 mass%, and TG showed that the thermostability of rGO/WPU nanocomposites decreased slightly compared to pure WPU, but carbon residue increased from 0.99 to 1.99 % when the mass fraction of rGO in WPU is 2 %. Cone Calorimeter test indicated that the flame-retardant and smoke suppression properties of rGO/WPU composites showed significant improvement compared to the WPU alone. When the mass fraction of rGO is 1 %, the total smoke release and smoke factor decreased by 25 and 38 %, respectively, compared to those of pure WPU.  相似文献   

3.
In order to facilitate the measurement of thermodynamic quantities at temperatures below 0°C in ethanol/water solvents, the standard potential of the silver-silver chloride electrode in 10, 20, and 40 wt.% ethanol has been determined at 25, 0, ?5, and ?10°C. Electromotive force measurements of cells of the type $$Pt;H_2 (g)|HCl(m) in EtOH/H_2 O|AgCl;Ag$$ were used. The potentials found at 25°C were in good agreement with earlier results. Mean activity coefficients for hydrochloric acid in the three mixed solvents were derived.  相似文献   

4.
In this work, a magnetically separable polypyrrole (PPy) modified Fe3O4/ZnO composite photo-catalyst was synthesized and its photocatalytic activity was tested. The as-prepared Fe3O4/ZnO/PPy nanocomposite was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra. Furthermore, three different photocatalysts including the Fe3O4/ZnO/PPy composite were tested using methyl orange (MO) degradation reaction under UV light irradiation. The relative results demonstrated that the Fe3O4/ZnO/PPy composite has the highest photochemical activity after 4 h photocatalytic experiment. It can be easily separated using an external magnetic field. This kind of composite photocatalysts with easiness of separation can have potential applications in the treatment of water contaminated by organic pollutants.  相似文献   

5.
The reaction of VI2 or TiI3, respectively, with ammonia in the presence of traces of water or oxygen, respectively, leads to [(NH3)5M? O? M(NH3)5]I4 · NH3 with M = V, Ti. Their structures were solved by X-ray single crystal data: Pbca (No. 61), Z = 4, M = V: a = 12.482(4) Å, b = 14.819(6) Å, c = 13.286(5) Å, N(F ? 3σF) = 983, N(variables) = 88, R/Rw = 0.053/0.063, M = Ti: a = 12.628(4) Å, b = 14.970(4) Å, c = 13.359(3) Å, N(F ? 3σF) = 1188, N(variables) = 88, R/Rw = 0.043/0.047. The structures consist of corner sharing octahedra double units [(NH3)5M? O? M(NH3)5]4+ with eclipsed conformation which are stacked together according to the motif of a distorted cubic face centered arrangement for the bridging oxygen atoms. IR spectroscopic investigations of the undeuterated vanadium compound and of 5% deuterated samples hint to N? H … I hydrogen bridge bonds and to remarkable π-bonding between the transition metal and the bridging oxygen atoms.  相似文献   

6.
This study describes the preparation of nanocomposites fabricated from monodispersed iron oxide (Fe3O4) and polypyrrole (PPy) by in situ chemical oxidative polymerization. The monodispersed 4 nm Fe3O4 nanoparticles which served as cores were synthesized using the thermal decomposition of a mixture of Iron (III) acetylacetonate and oleic acid in the presence of high boiling point solvents. The resulting nanoparticles were further dispersed in an aqueous solution with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form micelle/Fe3O4 spherical templates that avoid the aggregation of Fe3O4 nanoparticles during the further preparation of the nanocomposites. The Fe3O4/PPy nanocomposites were then synthesized via in situ chemical oxidative polymerization on the surface of the spherical templates. Both field‐emission scanning electron microscopy (FESEM) and high‐resolution transmission electron microscopy (HRTEM) images indicate that the resulting Fe3O4 nanoparticles are close to spherical dots with a particle size of about 4 nm and a standard deviation of less than 5% (4 ± 0.2 nm). Structural and morphological analysis using FESEM and HRTEM showed that the fabricated Fe3O4/PPy nanocomposites are core (Fe3O4)‐shell (PPy) structures. Morphology of the nanocomposites shows a remarkable change from spherical to tube‐like structures as the content of monodispersed Fe3O4 nanoparticles increases from 9% up to 24 wt %. The conductivities of these Fe3O4/PPy nanocomposites are about six times higher than those of PPy without Fe3O4. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4647–4655, 2007  相似文献   

7.
Polyurethane (PU) have been prepared by using polyether polyol (jagropol oil) and 1,6-hexamethylene diisocyanate (HMDI) as a cross-linker. The organically modified montmorillonite clay (o-MMT) is well dispersed into urethane matrix by in-situ polymerization method. A series of PU/o-MMT nanocomposites have been prepared by varying amounts viz., 1, 3, 5 and 6 wt % of nanoclay. The mechanical properties such as tensile strength, percentage elongation at break and tensile modulus of the composites were experimentally determined. The swelling behavior of the composites has been studied in different organic solvents. It was noticed that the swelling data of the composites significantly depends on the solubility parameters of the solvents. Microcrystalline parameters such as, lattice strain (g in %), average number of unit cells (〈N〉) in direction perpendicular to Bragg plane, surface weighted crystal size (D s) and interplanar distance (d hkl ), were calculated from X-ray patterns. These parameters were computed using Exponential asymmetric column length distribution functions. Morphological features of cryofractured PU/o-MMT composites were also analyzed using scanning electron microscopy (SEM).  相似文献   

8.
A four-stage asymmetric synthesis of (+)-disparlure [(7R,8S)-(+)-cis-methyl-7,8-epoxyoctadecane (V)] has been effected from 8-methylnon-2Z-en-l-ol (I), obtained by the carboalumination of acetylene with tris(5-methylhexyl)aluminum using the Sharpless reaction. The asymmetric epoxidation of (I), (Ar, mol. sieve A, (+)-DET, (iOPr)4Ti, t-BuOOH, ?15°C, 20 h; H2O, 1 h, NaOH, ?7°C, 30 min) gave 8-methyl-2S,3R-epoxynonan-l-ol (II), which was oxidized (kieselguhr-CrO3-Py, 0°C, 2 h; 25°C, 2 h) to 8-methyl-2S,3R-epoxynonan-l-al (III). The coupling of (III) with n-C8H17CH=PPh3 (?78°C, 1 h; 25°C, 15 h) gave 2-methyl-7R,8S-epoxyoctadec-9Z-ene (IV), the hydrogenation (H2/5% Pd-C, 25°C, 5 days) of which led to (V) in admixture with an isomerization product. Compound (V) was isolated by HPLC. Substance, yield, [α] D 25 : (II), 73, ?2.75°; (III), 80, [80.8°; (IV), 50, +37.25°; (V), 50, +0.8°. The IR and PMR spectra of (II–IV), the13C NMR spectra of (II) and (III), and the mass spectrum of (IV) are given.  相似文献   

9.
以高磺化度的磺化聚芳醚酮砜(SPAEKS)和吡咯(Py)为原料,通过原位聚合的方法制备了含有不同吡咯含量的SPAEKS/PPy复合膜.红外谱图表明SPAEKS聚合物中的磺酸基团与聚吡咯(PPy)中的亚氨基基团之间形成了强烈的相互作用.扫描电镜照片显示PPy能够均匀地分散在SPAEKS聚合物基体中,没有发生团聚现象.通过对复合膜的性能测试发现PPy的引入提高了复合膜的热稳定性,降低了复合膜的吸水率,改善了其水溶胀性.同时膜中水的脱附系数下降,提高了膜的保水能力.SPAEKS/PPy-3复合膜的甲醇渗透系数达到了1.18×10-7cm2/s,明显低于纯SPAEKS膜的8.52×10-7cm2/s,而其质子传导率虽有所降低,但在25℃和80℃仍然分别达到了0.039S/cm和0.061S/cm,能够满足质子交换膜对质子传导率的要求.研究结果表明,聚吡咯与SPAEKS中磺酸基的摩尔比为0.99的复合膜有望在直接甲醇燃料电池中得到应用.  相似文献   

10.
Tracer concentrations of Hf(IV) were extracted by 60% TBP solution in benzene from 5M HClO4, 5M HCl, 6M HNO3 and 8M H2SO4 solutions, and by 1·10?4 M TOPO solution in benzene from 2M HClO4 and 2M HCl solutions in the presence of a variety of organic solvents miscible with the aqueous phase. Whereas for TBP these solvents caused an increase of HF(IV) extraction, an opposite effect was observed for TOPO. The results were discussed from the point of view of various solute-solvent and solvent-solvent interactions.  相似文献   

11.
In this study, novel ternary synthesis of reduced graphene oxide (rGO) sheets via intercalation of Ag nanoparticles (Ag) and polypyrrole (PPy) was obtained for supercapacitor evaluations. The synthesis procedure of nanocomposite is simple, cheap, and ecologically friendly. The nanocomposites were analyzed by Fourier transform infrared-attenuated transmission reflectance (FTIR-ATR) and scanning electron microscopy-energy dispersion X-ray analysis (SEM-EDX). In addition, electrochemical performances of electrode active materials (rGO/Ag/PPy) of the samples were tested by means of galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The highest specific capacitance and energy density of rGO/Ag/PPy nanocomposite were obtained as Csp = 1085.22 F/g and E = 36.92 Wh/kg for [rGO]o/[Py]o = 1/5 at 4 mV/s in 1 M H2SO4 solution. Under the optimized preparation conditions in different initial feed ratios ([rGO]o/[Py]o = 1/1, ½, 1/5, and 1/10) of rGO/Ag/PPy, nanocomposites acquired a high Coulombic efficiency, and a retention of 66% of its initial capacitance for [rGO]o/[Py]o = 1/10 after 1000 cycles. GCD and EIS measurements of rGO/Ag/PPy nanocomposite electrode active material allowed for supercapacitor applications.  相似文献   

12.
A systematic study was performed on the extraction and separation of cadmium from iron halides in pure halo-acid solutions and their mixtures with H2SO4 and H3PO4. As solvents Amberlite LA-2, TBP, nitrobenzene and HDEHP were used. Recommended separation media for the amine are 2M HCl, 1M HBr, 1.12M HCl?2M H2SO4, 0.64M HBr?2M H2SO4, 1.12M HCl?4M H3PO4 0.64M HBr?7M H3PO4 and for TBP the medium 0.64M HBr?4M H3PO4 is the only suitable condition.  相似文献   

13.
The determination of the urinary vitamin D3 metabolites might prove helpful in the assessment of the vitamin D status. We developed a method for the determination of trace vitamin D3 metabolites, 25-hydroxyvitamin D3 [25(OH)D3] and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3], in urine using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with derivatization using an ESI-enhancing reagent, 4-(4′-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD), and its isotope-coded analogue, 2H4-DAPTAD (d-DAPTAD). The urine samples were treated with β-glucuronidase, purified with an Oasis® hydrophilic–lipophilic balanced (HLB) cartridge, and then subjected to the derivatization. The DAPTAD derivatization enabled the highly sensitive detection (detection limit, 0.25 fmol on the column), and the use of d-DAPTAD significantly improved the assay precision [the intra- (n?=?5) and inter-assay (n?=?3) relative standard deviations did not exceed 9.5 %]. The method was successfully applied to urine sample analyses and detected the increases of the urinary 25(OH)D3 and 24,25(OH)2D3 levels due to vitamin D3 administration. Graphical Abstract
Scheme of procedure for urinary vitamin D3 metabolite analysis based on LC/MS/MS with ESI-enhancing and isotope-coded derivatization.  相似文献   

14.
This work describes the preparation and characterization of polypyrrole (PPy)/iron oxide nanocomposites fabricated from monodispersed iron oxide nanoparticles in the crystalline form of magnetite (Fe3O4) and PPy by in situ chemical oxidative polymerization. Two spherical nanoparticles of magnetite, such as 4 and 8 nm, served as cores were first dispersed in an aqueous solution with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form micelle/magnetite spherical templates that avoid the aggregation of magnetite nanoparticles during the further preparation of nanocomposites. The PPy/magnetite nanocomposites were then synthesized on the surface of the spherical templates. Structural and morphological analysis showed that the fabricated PPy/magnetite nanocomposites are core (magnetite)‐shell (PPy) structures. Morphology of the PPy/magnetite nanocomposites containing monodispersed 4‐nm magnetite nanoparticles shows a remarkable change from spherical to tube‐like structures as the content of nanoparticles increases from 12 to 24 wt %. Conductivities of these PPy/magnetite nanocomposites show significant enhancements when compared with those of PPy without magnetite nanoparticles, in particular the conductivities of 36 wt % PPy/magnetite nanocomposites with 4‐nm magnetite nanoparticles are about six times in magnitude higher than those of PPy without magnetite nanocomposites. These results suggest that the tube‐like structures of 36 wt % PPy/magnetite nanocomposites may be served as conducting network to enhance the conductivity of nanocomposites. The magnetic properties of 24 and 36 wt % PPy/magnetitenanocomposites show ferromagnetic behavior and supermagnetism, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1291–1300, 2008  相似文献   

15.
Organic–inorganic hybrid nanocomposites composed of conductive polypyrrole (PPy) and surface modified silica (SiO2) were successfully prepared through an in situ chemical oxidative polymerization in supercritical carbon dioxide (scCO2). SiO2 nanoparticles were surface modified using 3‐methacryloxypropyltrimethoxysilane (MPTMS) in order to disperse well in the medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the SiO2 nanoparticles were encapsulated into the polymer. UV‐visible spectra of the diluted colloidal dispersions of PPy/SiO2 hybrid nanocomposites were similar to those of PPy system. Fourier transform infrared spectroscopy (FT‐IR) suggested the strong interaction between PPy and SiO2. Surface characterizations of nanocomposites were described by X‐ray photoelectron spectroscopy (XPS). The nanocomposites synthesized in scCO2 have been shown to possess higher electrical conductivity and thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

16.
Four titanium silanolates Ti(OSiR2R′)4 (1, R = Ph, R′ = tBu; 2, R = R′ = Ph; 3, R = R′ = iPr; 4, R = Me, R′ = tBu) were synthesised starting from Ti(OiPr)4 and the corresponding silanol, and their thermally induced decomposition was studied. Colourless single crystals of Ti(OSiPh Bu) CHCl C7H8 ( CHCl C7H8) were obtained from a mixture of chloroform and toluene (1:1) at ?20 °C. The compound crystallizes in the space group R3 c with Z = 18. The metal atom shows an almost ideal tetrahedral coordination, as is demonstrated by the O? Ti? O angles of 108.4(1)–111.1(1)°. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

17.
Decomposition yields of tetracycline hydrochloride /TC.HCl/ and chlorotetracycline hydrochloride /ClTC?HCl/ in methanol solution saturated with Ar or N2O were determined. Rate constants of the reaction es with some antibiotics were obtained: $$\begin{gathered} k/e_s^ - + ClTC \cdot HCl/ = 2 \cdot 49 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} ; \hfill \\ k/e_s^ - + TC \cdot HCl/ = 2 \cdot 86 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} \cdot \hfill \\ \end{gathered} $$ On the basis of the diffence between decomposition yields: ΔG=G?TC.HCl?G?ClTC.HCl′ 7-C?Cl group decomposition yield and the rate constant $$k/e_s^ - + Cl - C - 7/ = 7 \cdot 94 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} $$ were determined. It was demonstrated by1H NMR that the radical formed by degradation of 7-C?Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride /TC.HCl/.  相似文献   

18.
Polypyrrole/iron oxide (PPy/γ-Fe2O3) nanocomposites were synthesized by in situ oxidative polymerization of pyrrole in the presence of surface modified γ-Fe2O3 in supercritical carbon dioxide (scCO2). The structural properties of nanocomposite particles thus obtained were characterized by FT-IR, thermal analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that ca. 50 nm γ-Fe2O3 nanoparticles were well dispersed in PPy powder in TEM pictures. X-ray photoelectron spectroscopy (XPS) analysis also support that all γ-Fe2O3 nanoparticles are encapsulated by PPy. Magnetic property of the nanocomposites was measured by SQUID, which indicated that the nanocomposites are superparamagnetic. The effects of different loadings of γ-Fe2O3 on the polymerization were also investigated.  相似文献   

19.
A variety of fluoroalkyl end-capped oligomers, such as fluoroalkyl end-capped acrylic acid oligomer [RF-(ACA) n -RF], acryloylmorpholine oligomer [RF-(ACMO) n -RF], 2-acrylamido-2-methylpropanesulfonic acid oligomer [RF-(AMPS) n -RF], 2-(methacryloyloxy)ethanesulfonic acid oligomer [RF-(MES) n -RF], and N,N-dimethylacrylamide oligomer [RF-(DMAA) n -RF], were applied to the autoreduction of gold ions to give the corresponding oligomers/gold nanocomposites, of whose sharp plasmon absorption bands are observed around 535 nm. In these fluorinated oligomers, RF-(ACA) n -RF oligomer and RF-(ACMO) n -RF were effective for the one-pot preparation of the gold nanoparticles under very mild conditions; although the other fluorinated oligomers and the corresponding non-fluorinated–(ACMO) n -oligomer were unable to afford the gold nanoparticles. RF-(ACA) n -RF/SiO2 nanocomposites and RF-(ACMO) n -RF/SiO2 nanocomposites, which were prepared by the sol–gel reactions of tetraethoxysilane in the presence of silica nanoparticles and the corresponding oligomers under alkaline conditions, were also applied to the encapsulation of gold nanoparticles into these fluorinated nanocomposite cores through the autoreduction of gold ions at room temperature. Interestingly, these fluorinated oligomers/silica nanocomposite-encapsulated gold nanocomposites before and after calcination at 800 °C were found to exhibit the same plasmon absorption band around 525 nm. RF-(MES) n -RF oligomer and RF-(AMPS) n -RF oligomer are not suitable for the autoreduction of gold ions; however, RF-(MES)n-RF[or RF-(AMPS) n -RF]/polyaniline [PAn] nanocomposites, which were prepared by the polymerization of aniline initiated by ammonium persulfate in the presence of the corresponding oligomer, enabled the formation of gold nanoparticles through the oxidation of PAn in the composites at room temperature. The reversible conformational change of PAn in the nanocomposites from the polyemeraldine salt to the oxidized pernigraniline base was observed during such oxidation process. Graphical abstract
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20.
Tetraammine Lithium Cations Stabilizing Phenylsubstituted Zintl-Anions: The Compound [Li(NH3)4]2[Sn2Ph4] Ruby-red, brittle single crystals of [Li(NH3)4]2[Sn2Ph4] were synthesized by the reaction of diphenyltin dichloride and metallic lithium in liquid ammonia at ?35°C. The structure was determined from X-ray singlecrystal diffractometer data: Space group, P1 , Z = 1, a = 9.462(2) Å, b = 9.727(2) Å, c = 11.232(2) Å, α = 66.22(3)°, β = 85.78(3)°, γ = 61.83(3)°, R1 (F ? 4σF) = 5.13%, wR2 (F02 ? 4σF) = 10.5%, N(F ? 4σF) = 779, N(Var.) = 163. The compound contains to Sb2Ph4 isosteric centres [Sn2Ph4]2? as anions which are connected to rods by lithium cations in distorted tetrahedral coordination by ammonia. These rods are arranged parallel to one another in the b,c-plane, but stacked along [100].  相似文献   

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