X-ray Photoelectron Energy Spectrum Research Articles

Self-Assembly of Three-Dimensional Hyperbranched Magnetic Composites and Application in High-Turbidity Water Treatment.

In order to improve dispersibility, polymerization characteristics, chemical stability, and magnetic flocculation performance, magnetic Fe3O4 is often assembled with multifarious polymers to realize a functionalization process. Herein, a typical three-dimensional configuration of hyperbranched amino acid polymer (HAAP) was employed to assemble it with Fe3O4, in which we obtained three-dimensional hyperbranched magnetic amino acid composites (Fe3O4@HAAP). The characterization of the Fe3O4@HAAP composites was analyzed, for instance, their size, morphology, structure, configuration, chemical composition, charged characteristics, and magnetic properties. The magnetic flocculation of kaolin suspensions was conducted under different Fe3O4@HAAP dosages, pHs, and kaolin concentrations. The embedded assembly of HAAP with Fe3O4 was constructed by the N-O bond according to an X-ray photoelectron energy spectrum (XPS) analysis. The characteristic peaks of -OH (3420 cm-1), C=O (1728 cm-1), Fe-O (563 cm-1), and N-H (1622 cm-1) were observed in the Fourier transform infrared spectrometer (FTIR) spectra of Fe3O4@HAAP successfully. In a field emission scanning electron microscope (FE-SEM) observation, Fe3O4@HAAP exhibited a lotus-leaf-like morphological structure. A vibrating sample magnetometer (VSM) showed that Fe3O4@HAAP had a relatively low magnetization (Ms) and magnetic induction (Mr); nevertheless, the ferromagnetic Fe3O4@HAAP could also quickly respond to an external magnetic field. The isoelectric point of Fe3O4@HAAP was at 8.5. Fe3O4@HAAP could not only achieve a 98.5% removal efficiency of kaolin suspensions, but could also overcome the obstacles induced by high-concentration suspensions (4500 NTU), high pHs, and low fields. The results showed that the magnetic flocculation of kaolin with Fe3O4@HAAP was a rapid process with a 91.96% removal efficiency at 0.25 h. In an interaction energy analysis, both the UDLVO and UEDLVO showed electrostatic repulsion between the kaolin particles in the condition of a flocculation distance of <30 nm, and this changed to electrostatic attraction when the separation distance was >30 nm. As Fe3O4@ HAAP was employed, kaolin particles could cross the energy barrier more easily; thus, the fine flocs and particles were destabilized and aggregated further. Rapid magnetic separation was realized under the action of an external magnetic field.

Carbon coated iron oxide (CC-IO) as high performance electrode material for supercapacitor applications

Abstract Transition metal oxides are efficient electrode materials for supercapacitors due to their high theoretical specific capacitance. However their poor electrical conductivity needs to be further improved for fast charging and discharging the supercapacitor. There is an effective approach to overcome this issue by combining the carbon based materials with metal oxides. Addition of carbon based materials into transitional metal oxides will enhance the supercapacitor performance. Herein, carbon coated iron oxide (CC-IO) was synthesized using sucrose as a soluble carbon precursor and annealed at different temperatures (1000 °C to 1300 °C). The structure of the CC-IOs was analysed by X-ray diffraction and Raman spectroscopy. Pore structures and surface chemical compositions of CC-IOs were studied using BET and X-ray photoelectron energy spectrum, respectively. Surface morphology was investigated with scanning and transmission electron microscopy. CC-IO-1300 °C showed the maximum specific capacitance of 727 Fg−1, while CC-IO-1000 °C showed the minimum capacitance of 143 Fg−1 calculated by cyclic voltammetry (CV) at a scan rate of 5 mV/sec. The improvement in the specific capacitance of CC-IOs with increasing temperature is may be due to phase change of iron oxide and improvement in the crystalline nature of carbon coated on the iron oxide surface.

Strong covalent interaction Fe2O3/nitrogen-doped porous carbon fiber hybrids as free-standing anodes for lithium-ion batteries

A simple and novel method that combines the electrospinning technology with nonaqueous sol–gel method is developed to incorporate Fe2O3 nanoparticles into ZIF-8-derived nitrogen-doped highly porous carbon fibers (NPCFs). The size of Fe2O3 nanoparticles is about 5 nm. The interfacial interaction between Fe2O3 and NPCFs is investigated by thermogravimetric analysis, Raman spectrum and X-ray photoelectron energy spectrum. We found that Fe2O3 nanoparticles are anchored strongly in the NPCFs through the Fe–O–C covalent bond. The impact of the Fe2O3 content in the composites on electrochemical performance is also studied. When served as the flexible and free-standing anode of lithium-ion batteries (LIBs), the Fe2O3/NPCFs-66.9% exhibits superior electrochemical performance with the high discharge capacity of 1351 mA h g−1 at 50 mA g−1, remarkable rate capability (337 mA h g−1 even at 5000 mA g−1), and stable cycling performance (1106 mA h g−1 after 100 cycles at 100 mA g−1). The excellent anodic property can be ascribed to the ultra-small size of Fe2O3 nanoparticles, and the one-dimensional (1D) structure combined with the excellent electrical conductivity of NPCFs matrix. Moreover, the robust interfacial interaction Fe–O–C bond can restrain the aggregation of Fe2O3 nanoparticles and accommodate the volume change. This can effectively maintain the integrity of the whole electrode during the long-term cycles. The results show that the composite may be considered as a promising anode material for advanced LIBs.

Fe3O4@Carbon Nanosheets for All-Solid-State Supercapacitor Electrodes.

Fe3O4@carbon nanosheet composites were synthesized using ammonium ferric citrate as the Fe3O4/carbon precursor and graphene oxide as the structure-directing agent under a hydrothermal process. The surface chemical compositions, pore structures, and morphology of the composite were analyzed and characterized by nitrogen adsorption isotherms, TG analysis, FT-IR, X-ray photoelectron energy spectrum, transmission electron microscopy, and scanning electron microscopy. The composites showed excellent specific capacitance of 586 F/g, 340 F/g at 0.5 A/g and 10 A/g. The all-solid-state asymmetric supercapacitor device assembled using carbon nanosheets in situ embedded Fe3O4 composite and porous carbon showed a largest energy density of 18.3 Wh/kg at power density of 351 W/kg in KOH/PVA gel electrolyte. The synergism of high special surface to volume ratio, mesoporous structure, graphene-based conduction paths, and Fe3O4 nanoparticles provided a high surface area of ion-accessibility, high electric conductivity, and the utmost utilization of Fe3O4 and resulted in excellent specific capacitance, outstanding rate capability and cycling life as all-solid-state supercapacitor electrodes.

Gelatin-Based Microporous Carbon Nanosheets as High Performance Supercapacitor Electrodes

Microporous carbons nanosheets with controllable thicknesses were synthesized using gelatin biomass as both carbon and nitrogen precursors and graphene oxide (GO) without any auxiliary reagent. The pore structures, surface chemical compositions, and morphology of the microporous carbon material were analyzed and characterized by nitrogen adsorption isotherms, thermogravimetric analysis, Fourier transform infrared spectrum, X-ray photoelectron energy spectrum, and transmission electron microscope and scanning electron microscope images. The carbon nanosheets showed average thicknesses from 10 ± 4 to 30 ± 8 nm with tuning mass ratios of gelatin to GO from 20/1 to 100/1. The microporous carbon nanosheets exhibited high specific capacitance and excellent rate capability with a capacitance retention of 76% at 20 A/g in a 6 mol/L KOH aqueous electrolyte because of the shorter diffusion distance, large surface area, and excellent electrical conductivity.

Increased work function in PEDOT:PSS film under ultraviolet irradiation

An increase of work function (0.3 eV) is achieved by irradiating poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film in vacuum with 254-nm ultraviolet (UV) light. The mechanism for such an improvement is investigated by photoelectron yield spectroscopy, X-ray photo electron energy spectrum, and field emission technique. Surface oxidation and composition change are found as the reasons for work function increase. The UV-treated PEDOT:PSS film is used as the hole injection layer in a hole-only device. Hole injection is improved by UV-treated PEDOT:PSS film without baring the enlargement of film resistance. Our result demonstrates that UV treatment is more suitable for modifying the injection barrier than UV ozone exposure.

UV Sensitive Indium Gallium Zinc Oxide MOS- FET Fabricated by RF Magnetron Sputtering Method

Transparent indium gallium zinc oxide (IGZO) thin film was fabricated on SiO2/Si substrate by radio-frequency magnetron sputtering method. The IGZO thin film was characterized by X-ray diffraction, UV-VIS spectrometer, X-ray photoelectron energy spectrum to determine its optical, structural properties and binding energy information. The IGZO thin film was employed to construct metal-oxide-semiconductor field effect transistors (MOS-FET), which showed an on/off current of about 103. When the device was illuminated by UV light, the drain-to-source current was increased by 15 folders at -5 V gate voltages. The result indicates that the IGZO MOS-FET is sensitive to UV light.

Magnetite/graphene nanosheet composites: interfacial interaction and its impact on the durable high-rate performance in lithium-ion batteries

We explore in-depth the interfacial interaction between Fe3O4 nanoparticles and graphene nanosheets as well as its impact on the electrochemical performance of Fe3O4/graphene anode materials for lithium-ion batteries. Fe3O4/graphene hybrid materials are prepared by direct pyrolysis of Fe(NO3)3·9H2O on graphene sheets. The interfacial interaction between Fe3O4 and graphene nanosheets is investigated in detail by thermogravimetric and differential scanning calorimetry analysis, Raman spectrum, X-ray photoelectron energy spectrum and Fourier transform infrared spectroscopy. It was found that Fe3O4 nanoparticles disperse homogeneously on graphene sheets, and form strong covalent bond interactions (Fe–O–C bond) with graphene basal plane. The strong covalent links ensure the high specific capacity and long-period cyclic stability of Fe3O4/graphene hybrid electrodes for lithium-ion batteries at high current density. The capacity keeps as high as 796 mAhg−1 after 200 cycles without any fading in comparison with the first reversible capacity at the current density of 500 mAg−1 (ca. 0.6 C). At 1 Ag−1 (ca. 1.3 C), the reversible capacity attains ca. 550 mAhg−1 and 97% of initial capacity is maintained after 300 cycles. This work reveals an important factor affecting the high-rate and cyclic stability of metal oxide anode, and provides an effective way to the design of new anode materials for lithium-ion batteries.

A highly effective method for synthesizing hybrid Pt–CdSe nanocomposite

Hybrid Pt–CdSe nanocomposite was fabricated by a two-step chemical route. Cadmium selenide (CdSe) quantum rods (QRs) were prepared by a one-pot approach with tunable size. After ligand exchange, CdSe QRs were loaded with monodisperse 1.9 nm Pt nanopaticles in aqueous solution. Transmission electron microscopy (TEM) revealed the morphology of the Pt–CdSe nanostructure, and the decreased photoluminescence (PL) intensity demonstrated that electron and hole separation can be enhanced after loading Pt on CdSe QRs. X-ray photoelectron energy spectrum (XPS) was applied to confirm the existence of Pt and detect the Pt mass concentration of 3%.

Study on the long‐term thermal‐oxidative aging behavior of polyamide 6

AbstractThe long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Study on the High Efficiency Antioxidant of Polyoxymethylene

This article reports on the properties and uses of antioxidant F/B, a type of high efficiency antioxidant for polyoxymethylene (POM), consisting of the hindered phenolic main antioxidant, the secondary thermostabilizer phosphite ester, and lactone compound. Our experimental studies focused on the thermostabilization effect of antioxidant F/B on POM, which was measured by isothermal weight loss analysis at 220°C, isothermal weight loss rate analysis at 222°C, balance torque analysis, nonisothermal gravity analysis (TGA), oxidation induction time (OIT) analysis, and multiple processing and long-term aging analysis as compared to the commonly used antioxidant Irganox245 of POM. The results showed that the thermal stability of POM can be improved remarkably by using antioxidant F/B. The aging mechanism of POM under heat and oxygen was studied by the measurements of polarized light microscopy (PLM), differential scanning calorimetry (DSC), and X-ray photoelectron energy spectrum (XPS), which showed very slight changes of spherulites dimension, crystallinity, and the surface atom concentration after 15 days of aging at 140°C. Furthermore, the small amount of degradation of POM only occurred in the amorphous region of POM. These experiments demonstrated that lower amounts of antioxidant F/B can reach the same level of thermal stabilization of POM as is achieved with higher amounts of Irganox245, and can replace Irganox245 for use in the production of POM, which can further improve the thermal stabilization and reduce the production cost of POM.