•Phytic acid-based network in nanoscale was formed on microarc oxidated Mg alloy.•Sealing microdefects improved corrosion resistance of microarc oxidation film.•The as-fabricated composite coatings had long-term corrosion protection.In order to improve the corrosion resistance of magnesium alloys, environmentally friendly anti-corrosive composite coatings were fabricated on AZ31B Mg alloy. Mg alloys were first treated by plasma electrolytic oxidation (PEO) technique and then modified by phytic acid/3-aminopropyltrimethoxysilane (PA/APTMS) hybrid. Besides, the technique parameters were optimized. The composition and structure of the composite coatings were characterized by SEM, EDS, IR and XPS, the corrosion resistance was evaluated by electrochemical tests in 3.5% NaCl solution and the possible corrosion resistance mechanism was proposed as well. The results showed that the composite coating's corrosion resistance was remarkably improved by two or three orders of magnitude, compared with Mg alloy substrate and the single PEO coating. The PA/APTMS hybrid in network structure and the stable covalent bonds within the composite coatings effectively restricted the penetration of a corrosive medium into the Mg alloy surface, representing an excellent corrosion barrier effect.

•A novel PEO coating was prepared in the phosphate electrolyte containing K2ZrF6.•The obtained PEO coating was amorphous and comprised of Fe3O4, FePO4 and ZrO2.•The obtained PEO coating had characteristic of solid acid.•100% phenol could be degraded within 2 min under circumneutral pH.•The acid sites had a vital role in enhancing Fenton-like catalytic activity.Novel amorphous Fe3O4/FePO4/ZrO2 ceramic coatings as solid acid with porous structure were successfully synthesized in the phosphate electrolyte containing K2ZrF6 via plasma electrolytic oxidation (PEO) technique and characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The surface acidic property was investigated by NH3-TPD method. The results showed that the pore size and the intensity of pore interconnection of amorphous Fe3O4/FePO4/ZrO2 ceramic coating with solid acid property, increased with the increase of the K2ZrF6 dosage from 0.5 g to 2.0 g in the phosphate electrolyte. The Fenton-like performance of PEO coating catalysts was investigated by degradation of phenol under circumneutral pH. It was found that phenol removal efficiency decreased with the adding of K2ZrF6 amount from 0.5 g to 2.0 g except no catalytic activity of coating prepared without K2ZrF6, and Fenton-like PEO coating catalyst prepared with 0.5 g K2ZrF6 exhibited a superior catalytic activity which could degrade phenol thoroughly within 2 min under circumneutral pH. The strong acid sites played a dominant role in enhancing the Fenton-like catalytic activity. The excellent catalytic activity of PEO coating prepared in the phosphate electrolyte containing K2ZrF6 endowed it potential application in wastewater treatment.Download high-res image (242KB)Download full-size image

•C-TNTs film is obtained by gas thermal penetration method on TiO2 nanotubes.•Ti4+ is reduced to Ti3+ and the splitting organic products chemisorbed on the film.•The C-TNTs film's largest areal capacitance is up to 38.2 mF/cm2 at 10 mV/s.•The C-TNTs film's highest areal capacitance is 12.1 mF/cm2 at 125 μA/cm2•C-TNTs film keeps good stability and reversibility as supercapacitor electrode.In this work, we develop a novel carbon-modification method to improve the electronic conductivity and the electrochemical performances of TiO2 nanotubes electrodes for binder-free supercapacitor. The carbon modified TiO2 nanotubes (denoted as C-TNTs) is prepared by two-step process of anodic oxidation and gas thermal penetration method on a Ti plate. The structure and composition of C-TNTs was characterized by SEM, XRD, EDS, RAMAN, XPS and XANS, respectively. The electrochemical performances of C-TNTs were evaluated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charging/discharging (GCD) tests. The C-TNTs film presents almost the same morphology as TNTs film and C is successfully deposited on the film in different forms. The largest areal capacitance of C-TNTs film is 38.2 mF/cm2 at the scan rate of 10 mV/s in CV curves, and 12.10 mF/cm2 at the current density of 0.125 mA/cm2 in GCD measurements, 21.1 times than that of TNTs film. The great improvement of the capacitance can be attributed to the increase of conductivity and the pseudocapacitance effect, which corresponds to the C deposition and Ti4+ reduction into Ti3+, and the chemisorbed CO and OH on the film surface, respectively. The galvanostatic charging/discharging cycle test indicates the good stability and reversibility of C-TNTs film as the electrode material in the application of supercapacitor.

•Fenton-like amorphous Fe3O4 and SiO2 composite coating catalyst was prepared.•The coating prepared under 12 A/cm2 and 10 min has the highest removal efficiency.•The total leached iron was below the EU directives (< 2 mg/L).•The composite coating catalyst showed excellent stability and reusability.Plasma electrolytic oxidation (PEO) on Q235 carbon steel has been applied in the silicate electrolyte. The ceramic coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and scanning electron microscopy (SEM). The effects of ceramic coating preparation conditions on the surface morphology, composition, thickness and phenol degradation by Fenton-like reaction were investigated. The results indicated that the ceramic coating with porous structure was comprised of amorphous phases SiO2 and Fe3O4. The average pore diameter and thickness of the ceramic coating increased slightly with the increase of reaction time and current density of PEO. In addition, the ceramic coatings were mainly composed of Si, Fe, Na, P, and O according to the EDS analysis. The phenol degradation experiments indicated that the removal efficiency was reduced with the increase of reaction time, but increased at 30 min. On the contrary, the degradation rate was first enlarged, and then decreased with the increase of current density. The 96% removal efficiency of phenol was achieved after 120 min degradation at the condition of 35 mg/L phenol, 6.0 mmol/L H2O2, pH 4.0 and T = 303 K while 6 cm2 ceramic coating was used as Fenton-like catalyst which was prepared under 12 A/cm2 and 10 min. The total leached Fe was below the EU directives (< 2 mg/L). The leached Fe originated not only from the substrate, but also from ceramic coating. The unique advantages over the nanoparticle and excellent stability endowed it with desirable and promising application in the wastewater treatment.

In this paper, multi-grain-boundary hierarchical dendritic micro–nano structure α-Fe was successfully synthesized in electrolyte containing rare earth (RE) ions by the electric field-induced and electrochemical reduction method. The results show that the size of the dendritic morphology samples decreases from about 10 μm to about 6 μm with increasing RE ion concentration, and plentiful nano-sized particles are generated on their surface due to the adsorption suppression effect of the RE ions, which facilitates a great increase in the BET surface area and the formation of abundant grain boundaries. All of these RE-added dendritic α-Fe exhibit excellently enhanced electromagnetic absorption performance. The minimum reflection loss (RL) value (around −60 dB) of the RE-added samples is twice that of the samples without added RE ions, and the absorption peak moves to higher frequency range as the RE ion concentration is increased. The widest absorption band (in which RL < −20 dB) of the La-added samples grows to 2 GHz. We mainly ascribe the great enhancement of the EMA performance to the unique structural characteristics, such as the great surface area and abundant grain boundaries, which could affect the dielectric loss and magnetic loss of the absorbers. Not only has this work directly confirmed the influence of the interface and grain boundaries on the electromagnetic absorption performance, but it has also provided a new way to control the morphology and microstructure using RE ions.

•CNT is introduced into graphene to prevent restacking by solvothermal reaction.•Ethanol as a low cost and green solvent is used in solvothermal reaction.•Ni(OH)2 nanosheets were chemically precipitated into GS-CNT to increase the capacitance.Ni(OH)2-graphene sheet-carbon nanotube composite was prepared for supercapacitance materials through a simple two-step process involving solvothermal synthesis of graphene sheet-carbon nanotube composite in ethanol and chemical precipitation of Ni(OH)2. According to N2 adsorption/desorption analysis, the Brunauer–Emmett–Teller surface area of graphene sheet-carbon nanotube composite (109.07 m2 g−1) was larger than that of pure graphene sheets (32.06 m2 g−1), indicating that the added carbon nanotubes (15 wt.%) could prevent graphene sheets from restacking in the solvothermal reaction. The results of field emission scanning electron microscopy and transmission electron microscopy showed that Ni(OH)2 nanosheets were uniformly loaded into the three-dimensional interconnected network of graphene sheet-carbon nanotube composite. The microstructure enhanced the rate capability and utilization of Ni(OH)2. The specific capacitance of Ni(OH)2-graphene sheet-carbon nanotube composite was 1170.38 F g−1 at a current density of 0.2 A g−1 in the 6 mol L−1 KOH solution, higher than those provided by pure Ni(OH)2 (953.67 Fg−1) and graphene sheets (178.25 F g−1). After 20 cycles at each current density (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 A g−1), the capacitance of Ni(OH)2-graphene sheet-carbon nanotube composite decreased 26.96% of initial capacitance compared to 74.52% for pure Ni(OH)2.

In this paper, both the leaf-like dendritic CoxFe1−x (x = 0.1, 0.3, 0.5 and 0.7) alloys and novel grain-like dendritic nanostructure Co0.9Fe0.1 alloy and ε-Co were synthesized by an electric field-induced and electrochemical reduction method under over-polarization current. The formation of these two dendritic structures is not only attributed to the electric-field strength and ion concentration gradient, but also related to their crystalline structure. The trunks and branches of leaf-like dendritic bcc CoxFe1−x grow along three of the six equivalent <110> directions. However, for grain-like dendritic hcp ε-Co, their six branches grow along the six equivalent <101> directions, and the trunks are oriented preferably along [0002] direction. The electromagnetic absorption (EMA) performance of leaf-like structure CoxFe1−x alloys are obviously enhanced with Co content increase from −21.7 dB for Co0.1Fe0.9 to −59.1 dB for Co0.5Fe0.5. Meanwhile, the response frequency of maximum reflection loss (RL) shifts to the higher band. In the case of grain-like dendritic Co0.9Fe0.1 alloy, it has the widest frequency band from 5 to 18 GHz with RL < −20 dB due to the mixed phase composition. We ascribe the enhancement of dendritic CoxFe1−x alloys' EMA performance to the different elemental compositions, crystalline structures, surface anisotropy and crystal defects, which contribute to enhancing the effective complementarities between dielectric loss and magnetic loss.

A novel durian-like multi-functional water soluble Fe3O4–Au nanocomposite is fabricated via a facile layer-by-layer technology in which a mercapto-silica shell is utilized as a functional coating on the central Fe3O4 nanoparticle cluster. Then gold nanoparticles are loaded onto the surface of Fe3O4, stabilized by Au–S chemical bonding. The fabricated nanocomposites inherit excellent physical and chemical properties from their building blocks, simultaneously exhibiting superparamagnetic, surface plasmon resonance and surface enhanced Raman scattering (SERS) active properties. Based on the magnetic separability of the inner Fe3O4 nanoparticle clusters and the SERS active properties of the suface gold, a selective detection method for benzidine has been developed for rapid detection and ease of operation with a low detection limit of 0.18 ppm.

In this work, large-scale three-dimensional dendritic α-Fe which possesses two different faces with uniform width of about 3.0 μm and length of about 9.0 μm was directly synthesized using an electric field-induced and electrochemical reduction method in FeSO4 aqueous solution for the first time. This synthesis method shows great advantages including environment-friendliness, extremely low cost and high efficiency. The specific dendritic structure was induced to grow along three of six 〈110〉 crystallographically equivalent directions under a symmetrical electric field. The uniform length of the dendritic α-Fe is subject to Fe2+ concentration gradient. The investigation of the magnetic properties and electromagnetic absorbability indicates that this kind of dendritic α-Fe exhibits both high absorption efficiency with the minimum reflection loss value of −32.3 dB and a broad absorption band up to 12 GHz. The dendritic α-Fe could be an extremely promising electromagnetic absorption material.

To enhance the microwave absorption of Fe3O4 nanocrystals, ZnO nanoshells with a thickness of 2 nm were grown on Fe3O4 nanocrystals by heterogeneous nucleation. After being coated with ZnO nanoshells, the material possesses a far more improved ability for microwave absorption. A minimum reflection loss of −3.31 dB for Fe3O4 nanocrystals alone was improved to a minimum reflection loss of −22.69 dB and with an effective absorption band (RL < −10 dB) covering a frequency range of 10.08–15.97 GHz. The reasons for the enhanced microwave absorption were studied by the use of X-ray absorption near-edge structures at O K-edge, electron spin resonance analysis and microwave electromagnetic parameters mapping. The results indicate that the decoration of the dielectric ZnO shell had varied the dielectric property as well as the oxidization environment and distribution of Fe ions on the surface of the Fe3O4. This well balances the permeability and the permittivity of the nanomaterials and decreases the difficulty of impedance matching the microwave absorber within the free space. This leads to the Fe3O4@ZnO nanohybrids possessing vastly improved microwave absorption as compared to Fe3O4 nanocrystals alone.

Vertically aligned CdTe–ZnO composite nanorods are constructed on the indium tin oxide substrates by layer-by-layer deposition of CdTe quantum dots on ZnO nanorod arrays. The CdTe shell forms an intact interface with the wurtzite ZnO nanorod, and its thickness can be accurately tuned by changing the deposition cycles. Photoluminescent measurements further disclose the band alignment between the CdTe shell and the ZnO core, which makes CdTe–ZnO composite nanorods exhibiting good photoelectron-chemical properties and being a prospective material for removal of phenol from wastewater under visible light irradiation. Impressively, about 75% degradation of 100 mg/L phenol solution and up to 53.2% removal of the total organic carbon are achieved within 150 min using the optimized CdTe–ZnO composite nanorods as photoelectrocatalysts under visible light.

The understanding of the interaction between the building blocks in the hybrids can advance our comprehension of design principles in high-performance microwave absorbing materials. Here, we report a hybrid material consisting of magnetite (Fe3O4) nanocrystals grown on multiwalled carbon nanotube (MWCNT) as a high-performance microwave absorber in the 2–18 GHz band, although Fe3O4 nanocrystals or MWCNTs alone or their physical mixture show little microwave absorption. The hybrid is characterized by transmission electron microscopy, X-ray diffraction, and vector network analysis, X-ray absorption near-edge structures at the C K-edge and Fe L3,2-edge, and electron spin resonance analysis. Microstructural analysis reveals that Fe3O4 nanocrystals are immobilized on the MWCNT surface by a strong interaction. Charges in the MWCNT/Fe3O4 hybrids transfer from the conduction band in Fe3O4 to C 2p-derived states in the MWCNT substrate. Dipole interaction between the magnetic nanocrystals is increased. The synergetic interactions leads to much improved microwave absorption.

Fluorescent detection is an attractive method for the detection of toxic chemicals. However, most chemosensors that are currently utilized in fluorescent detection are based on organic dyes or quantum dots, which suffer from instability, high background noise and interference from organic impurities in solution, which can also be excited by UV radiation. In the present research, we developed a novel NaYF4:Yb,Ho/Au nanocomposite-based chemosensor with high sensitivity (10 ppb) and selectivity over competing analytes for the detection of the insecticide cartap. This nanosensor is excited with a 970-nm laser instead of UV radiation to give an emission peak at 541 nm. In the presence of cartap, the nanocomposites aggregate, resulting in enhanced luminescence resonance energy transfer between the NaYF4:Yb,Ho nanocrystals and the gold nanoparticles, which decreases the emission intensity at 541 nm. The relative luminescence intensity at 541 nm has a linear relationship with the concentration of cartap in the solution. Based on this behavior, the developed nanosensor successfully detected cartap in farm produce and water samples with satisfactory results.Graphical AbstractA novel NaYF4:Yb,Ho/Au nanocomposite-based nanosensor was developed. This sensor can be excited with a 970-nm laser and exhibits a high selectivity over competing analytes for the detection of cartap and high sensitivity (10 ppb), far lower than the maximum level (1 ppm) of cartap in farm produce permitted by the environmental protection agencies (EPAs) of the United States and China.Highlights► A novel NaYF4:Yb,Ho/Au hybrid is fabricated by layer-by-layer assembly. ► Cartap results in luminescence resonance energy transfer between the nanosensors. ► The method exhibits good sensitivity, selectivity and accuracy.

The poor thermal stability of nanoparticle superlattices heavily inhibits their practical applications. In present research, using stable thiolate-capped Au11(SCH2CH2COO−)7([CH3(CH2)7]4N+)7 nanoclusters as the building blocks, novel luminescent Au11 nanocluster superlattices with high thermal stability have been fabricated by self-assembly. The nanocluster superlattices have a blade-like morphology and extend on a micrometre length scale with the largest over 50 μm. Under an excitation at 400 nm, the fabricated Au11 nanocluster superlattices emit a blue luminescence with the emission peak of 473 nm. The native stability of thiolate-capped gold nanoclusters and the steric repulsion induced by the high-density ligands (SCH2CH2COO−)7([CH3(CH2)7]4N+)7 endows the fabricated superlattices with high thermal stability. The differential scanning calorimetry and thermogravimetric analysis indicates that the superlattices undergo irreversible endothermic transitions in the range of room temperature to 200 °C, which starts at 124 °C and reaches a peak at 160 °C. When processed with heat treatment below the transition temperature or stored for six months at room temperature, there is no obvious difference detected in the emission intensity of the fabricated Au11 nanocluster superlattices. Such thermostability gives the fabricated nanocluster superlattices great potential for many applications, especially for optical devices.

ZnS–In2S3–Ag2S solid solution coupled with TiO2-xSx nanotubes film catalyst has been successfully prepared by a two-step process of anodization and solvothermal methods for the first time. The as-prepared photo-catalysts are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Visible diffuse reflectance spectra (UV–Vis DRS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. The results show that the ZnS–In2S3–Ag2S solid solution are deposited on the surface of TiO2NTs nanotubes under the solvothermal conditions, by which S atoms are incorporated into the lattice of TiO2 through substituting the sites of oxygen atoms. Such ZnS–In2S3–Ag2S@TiO2-xSx nanotubes composite presents the enhanced absorption in visible region and the efficient transfer of photoelectron between the solid solution and TiO2-xSx nanotubes, which determines the excellent photocatalytic activity for the photocatalytic hydrogen evolution from aqueous solutions containing the sacrificial reagents of Na2S and Na2SO3 under 500 W Xe lamp irradiation.Highlights► ZnS-In2S3-Ag2S coupled with TiO2-xSx nanotubes has been successfully prepared. ► ZnS-In2S3-Ag2S enables TiO2NTs to form TiO2-xSxnanotubes by solvothermal treatment. ► Ag doping suppresses the oxidation of solid solution on the surface of TiO2NTs. ► ZnS-In2S3-Ag2S@TiO2NTs shows an excellent photocatalytic hydrogen evolution activity.

Electrochemical impedance spectroscopy and transient waveform analysis were used in the current paper to study the effects of frequency on the growth process of plasma electrolytic oxidation (PEO) coating, which was prepared on Ti6Al4V using single-pulse power supply. The results showed that the voltage range of the anodic spark stage was not affected by frequency, and the structures of the coatings prepared at the same termination voltage were very similar. The voltage range of the micro arc stage increased with frequency, and the damage of the microdischarges to the coating decreased with frequency. Results also confirm that the PEO process can be monitored via transient waveform analysis.Highlights► Frequency effects on PEO process are studied by EIS and transient waveform analysis. ► The voltage range of anodic spark stage is not affected by frequency. ► Coating structure is close at the same termination voltage in anodic spark stage. ► The voltage range of micro arc stage decreases with frequency. ► PEO process can be monitored by transient waveform method.

Plasma electrolytic oxidation (PEO) was studied using electrochemical impedance spectroscopy (EIS) and transient waveform analysis. First, EIS measurements on coatings prepared under constant current density were conducted in the working electrolyte. The EIS analysis showed that the coating structure changed with the termination voltage. Second, the pulse waveform of the power supply was recorded during the PEO process. It showed that a charging process occurred across the breakdown coating at the beginning of the pulse. The present study analysed this charging process in detail.Highlights► Growth process of PEO coating is analysed by EIS and transient waveform methods. ► Variation of coating structure during the growth is well reflected by EIS results. ► Transient analysis procedure is applied to PEO process for the first time. ► Structure character of the breakdown coating is obtained by transient method.

A facile and template-free layer-by-layer assembly-based method can be employed to synthesize structurally and morphologically controllable Mo-doped TiO2 films which demonstrate promising photoactivity.

A series of Mo-doped TiO2 films are prepared on quartz substrate by the layer-by-layer assembly method. The films are characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scan electron microscopy (SEM), UV-vis spectrophotometry and fluorescence spectrophotometry. The results show that TiO2 phase transformation from anatase to rutile is promoted with higher dopant concentration. The surface oxygen vacancies (SOVs) of Mo-doped TiO2 films bind photoinduced electrons to further give rise to new photoluminescence (PL) signals, and the intensities of PL signals are in proportion to SOVs content of the films. The photocatalytic activity of TiO2 film is evaluated by measuring H2 evolution from water and the effects of SOVs of Mo-doped TiO2 films on photocatalytic processes are investigated along with their inherent relationships.

Rare earth complex Tb(PCAD)3Phen was synthesized by introducing 3-pyridylacetic acid (PCAD) and phenanthroline (1,10-Phen) as the ligands and characterized by UV, fluorescent, IR spectra and X-ray diffraction (XRD) as well as elemental analysis. The complex exhibited ligand-sensitized green emission, and it has higher sensitized luminescent efficiency and longer lifetime. In device ITO/PVK/Tb(PCAD)3Phen/Al, Tb3+ may be excited by intramolecular energy transfer from ligand as observed by electroluminescence. The main emitting peak at 545 nm can be attributed to the transition of 5D4 → 7F5 of Tb3+ ion and this process results in the enhancement of green emission from electroluminescence device. The effect and mechanism of the ligands (PCAD and 1,10-Phen) on the luminescence properties of terbium complex were discussed. The present study may be important and helpful for the development of green color rare earth display applications.

The growth behaviour of plasma electrolytic oxidation (PEO) coating on Ti6Al4V was studied by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test, focusing on effects of the electrolyte additive – calcium hypophosphite. The EIS analysis of the outer layer of the PEO coating provided insight into the structure of the coating, which was confirmed by SEM results. The EIS analysis of the inner layer of the PEO coating provided information matching well with the results of the potentiodynamic polarization test.

Anchored visible-light-absorbing TiO2 films have been synthesized by the layer-by-layer method on a quartz slide substrate as a new class of visible light-sensitive photocatalyst. UV-vis, XRD and XPS spectra show that W and Mn enter the TiO2 lattices and partially substitute for Ti, and that W appears to have a solubility limit into the anatase structure. The Mn and W dopants cause new electronic states above the valence-band edge of pure TiO2, and the new electronic states may be directly related to the visible-light absorption of doped TiO2 films. A constant H2 generation rate is obtained for long periods of time for all the investigated TiO2 films, and the H2 production rates for titania films doped with 0.74 at% W (relative to Ti) are 4.1 and 3.3 times higher than that of non-doped TiO2 under UV and visible light, respectively, as the dopant atoms not only restrict the band gap to the visible region, but also facilitate the detrapping of charge carriers to the surface of the catalyst.

The composition of electrolyte plays a key role in the structure and properties of the synthesized ceramic coating by microarc oxidation (MAO) process. In the present study, F− ion, the smallest size among the negative ions, is chosen as the additive. The effects of F− ion on the structure and properties of the formed ceramic coating have been investigated in detail. Inspection of the scanning electron microscopy (SEM) and X-ray diffraction (XRD) suggests that the addition of fluoride during MAO process can decrease the porosity of the surface and enhance the density of the coating. These structure features lead to the corrosion resistances and tribological properties greatly improved. Based on the experimental results and the characteristics of MAO process, the influence mechanism of F− is proposed.

Effects of charging current on the potentiodynamic polarization curve that is obtained to determine the Tafel slopes and corrosion current density are reported in this paper. The potentiodynamic polarization curves are obtained at different scan rates for Ti6Al4V in naturally aerated 3.5% NaCl solution. The results show that the potential where the external current density equals to zero does not equal to the open circuit potential. The extent of the distortion of the polarization curve can be reflected the difference between the two potentials. Some significant errors are introduced into the values of the corrosion current density and Tafel slopes due to this distortion. In addition, severe distortion of the polarization curve can lead to misunderstanding of the electrode process. A new method is adopted to eliminate this distortion, and the potential-dependent of charging current density can also be obtained.

A procedure based on solid phase extraction (SPE) has been developed for the simultaneous pre-concentration of herbicide mefenacet (MN) and its three photolysis degradation products. Three metabolites studied were hydroxylbenzothiazole (HBT), N-methylaniline (N-MA) and 2-benzothiazoloxyacetic acid (2-BAA). A trimethylsilylation derivatization method was applied for the analysis of HBT and 2-BAA which were derivatized to be corresponding derivatives D-1 and D-2, respectively, and a rapid resolution liquid chromatography-electrospray ionization mass spectrometry (RRLC-ESI-MS) system was used for the separation, identification and quantification of these four analytes. In the SPE pre-concentration step, three types of cartridges and four kinds of eluents were investigated. The mean recoveries of these four analytes were between 78.6% and 101.2% and relative standard deviations were between 3.2% and 9.2%. The limits of detection (LODs) obtained were 0.02 ng l−1 for MN and N-MA and 0.1 ng l−1 for HBT and 2-BAA which were less than the maximum residue limits (MRLs) in drinking water established by European legislation (0.1 μg l−1). The proposed method was applied to evaluate the presence and evolution with time of herbicide mefenacet and its degradation products in samples of Songhuajiang River of Heilongjiang province, China. The analyses, conducted from April to July of 2008, pointed to the presence of MN, 2-BAA, HBT and N-MA at maximum levels 1.0, 0.08, 0.1 and 0.3 μg l−1.

Two novel Cd(II) coordination frameworks based on a semirigid asymmetric ligand L and aromatic multi-carboxylate ligands, {[Cd2L(btc)(H2O)2]·5H2O}n (1) and [Cd2L2(bdc)]n (2) (L = (4-((2-(pyridine-2-yl)-1H-imidazol-1-yl)methyl)benzoic acid, H3btc = 1,3,5-benzenetricarboxylic acid, H2bdc = 1,3-benzenedicarboxylic acid), have been hydrothermally synthesized, and structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography. Due to various coordination modes and conformations of the semirigid asymmetric ligand, and carboxylate containing co-ligands, therefore, the two complexes exhibit structural and dimensional diversity. Complex 1 exhibits a novel 2D (3, 5)-connected network structure with (3·52)(32·53·64·7) topology. Complex 2 exhibits a novel 3D CdSO4 topology, which is formed from different dinuclear cadmium units. In addition, the photoluminescence properties of the free ligand L, and complexes 1 and 2 were studied in the solid state at room temperature.Two novel Cd(II) coordination frameworks based on a semirigid asymmetric ligand4-((2-(pyridine-2-yl)-1H-imidazol-1-yl)methyl)benzoic acid have been prepared by hydrothermal reaction. Complex 1 exhibits a novel (3, 5)-connected 2D network structure. Complex 2 exhibits a novel 3D CdSO4 topology, which is formed from different dinuclear cadmium unit. In addition, complexes 1 and 2 both exhibit luminescent properties at room temperature.

The aim of this work was to investigate the effects of calcination/acid-activation on the composition, structure, and photocatalytic (PC) reduction property of an anodic oxidation TiO2/Ti film catalyst. The surface morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction. The catalytic property of the film catalysts was evaluated through the removal rate of potassium chromate during the PC reduction process. The results showed that the film catalysts were composed of anatase and rutile TiO2 with a micro-porous surface structure. The calcination treatment increased the content of TiO2 in the film, changed the relative ratio of anatase and rutile TiO2, and decreased the size of the micro pores of the film catalysts. The removal rate of potassium chromate was related to the technique parameters of calcination/acid-activation treatment. When the anodic oxidation TiO2/Ti film catalyst was calcined at 873 K for 30 min and then acid-activated in the concentrated H2SO4 for 60 min, it presented the highest catalytic property, with the removal rate of potassium chromate of 96.3% during the PC reduction process under the experimental conditions.

•Amorphous Fe3O4/SiO2 ceramic coating decorated with sulfur was prepared.•S decorated ceramic coatings had characteristic of strong solid acid.•99% phenol could be degraded by this coating within 8 min under circumneutral pH.•The strong acid sites played a dominant factor in enhancing its catalytic activity.In this study, solid acid amorphous Fe3O4/SiO2 ceramic coating decorated with sulfur on Q235 carbon steel as Fenton-like catalyst for phenol degradation was successfully prepared by plasma electrolytic oxidation (PEO) in silicate electrolyte containing Na2S2O8 as sulfur source. The surface morphology and phase composition were characterized by SEM, EDS, XRD and XPS analyses. NH3-TPD was used to evaluate surface acidity of PEO coating. The results indicated that sulfur decorated amorphous Fe3O4/SiO2 ceramic coatings with porous structure and higher acid strength had the similar pore size and the surface became more and more uneven with the increase of Na2S2O8 in the silicate electrolyte. The Fenton-like catalytic activity of sulfur decorated PEO coatings was also evaluated. In contrast to negligible catalytic activity of sulfur undecorated PEO coating, catalytic activity of sulfur decorated PEO coating was excellent and PEO coating prepared with 3.0 g Na2S2O8 had the highest catalytic activity which could degrade 99% of phenol within 8 min under circumneutral pH. The outstanding performance of sulfur decorated PEO coating was attributed to strong acidic microenvironment and more Fe2+ on the surface. The strong acid sites played a key factor in determining catalytic activity of catalyst. In conclusion, rapid phenol removal under circumneutral pH and easier separation endowed it potential application in wastewater treatment. In addition, this strategy of preparing immobilized solid acid coating could provide guidance for designing Fenton-like catalyst with excellent catalytic activity and easier separation.Download high-res image (232KB)Download full-size image

In this work, large-scale three-dimensional dendritic α-Fe which possesses two different faces with uniform width of about 3.0 μm and length of about 9.0 μm was directly synthesized using an electric field-induced and electrochemical reduction method in FeSO4 aqueous solution for the first time. This synthesis method shows great advantages including environment-friendliness, extremely low cost and high efficiency. The specific dendritic structure was induced to grow along three of six 〈110〉 crystallographically equivalent directions under a symmetrical electric field. The uniform length of the dendritic α-Fe is subject to Fe2+ concentration gradient. The investigation of the magnetic properties and electromagnetic absorbability indicates that this kind of dendritic α-Fe exhibits both high absorption efficiency with the minimum reflection loss value of −32.3 dB and a broad absorption band up to 12 GHz. The dendritic α-Fe could be an extremely promising electromagnetic absorption material.

A novel durian-like multi-functional water soluble Fe3O4–Au nanocomposite is fabricated via a facile layer-by-layer technology in which a mercapto-silica shell is utilized as a functional coating on the central Fe3O4 nanoparticle cluster. Then gold nanoparticles are loaded onto the surface of Fe3O4, stabilized by Au–S chemical bonding. The fabricated nanocomposites inherit excellent physical and chemical properties from their building blocks, simultaneously exhibiting superparamagnetic, surface plasmon resonance and surface enhanced Raman scattering (SERS) active properties. Based on the magnetic separability of the inner Fe3O4 nanoparticle clusters and the SERS active properties of the suface gold, a selective detection method for benzidine has been developed for rapid detection and ease of operation with a low detection limit of 0.18 ppm.

Anchored visible-light-absorbing TiO2 films have been synthesized by the layer-by-layer method on a quartz slide substrate as a new class of visible light-sensitive photocatalyst. UV-vis, XRD and XPS spectra show that W and Mn enter the TiO2 lattices and partially substitute for Ti, and that W appears to have a solubility limit into the anatase structure. The Mn and W dopants cause new electronic states above the valence-band edge of pure TiO2, and the new electronic states may be directly related to the visible-light absorption of doped TiO2 films. A constant H2 generation rate is obtained for long periods of time for all the investigated TiO2 films, and the H2 production rates for titania films doped with 0.74 at% W (relative to Ti) are 4.1 and 3.3 times higher than that of non-doped TiO2 under UV and visible light, respectively, as the dopant atoms not only restrict the band gap to the visible region, but also facilitate the detrapping of charge carriers to the surface of the catalyst.

The poor thermal stability of nanoparticle superlattices heavily inhibits their practical applications. In present research, using stable thiolate-capped Au11(SCH2CH2COO−)7([CH3(CH2)7]4N+)7 nanoclusters as the building blocks, novel luminescent Au11 nanocluster superlattices with high thermal stability have been fabricated by self-assembly. The nanocluster superlattices have a blade-like morphology and extend on a micrometre length scale with the largest over 50 μm. Under an excitation at 400 nm, the fabricated Au11 nanocluster superlattices emit a blue luminescence with the emission peak of 473 nm. The native stability of thiolate-capped gold nanoclusters and the steric repulsion induced by the high-density ligands (SCH2CH2COO−)7([CH3(CH2)7]4N+)7 endows the fabricated superlattices with high thermal stability. The differential scanning calorimetry and thermogravimetric analysis indicates that the superlattices undergo irreversible endothermic transitions in the range of room temperature to 200 °C, which starts at 124 °C and reaches a peak at 160 °C. When processed with heat treatment below the transition temperature or stored for six months at room temperature, there is no obvious difference detected in the emission intensity of the fabricated Au11 nanocluster superlattices. Such thermostability gives the fabricated nanocluster superlattices great potential for many applications, especially for optical devices.

A facile and template-free layer-by-layer assembly-based method can be employed to synthesize structurally and morphologically controllable Mo-doped TiO2 films which demonstrate promising photoactivity.

In this paper, both the leaf-like dendritic CoxFe1−x (x = 0.1, 0.3, 0.5 and 0.7) alloys and novel grain-like dendritic nanostructure Co0.9Fe0.1 alloy and ε-Co were synthesized by an electric field-induced and electrochemical reduction method under over-polarization current. The formation of these two dendritic structures is not only attributed to the electric-field strength and ion concentration gradient, but also related to their crystalline structure. The trunks and branches of leaf-like dendritic bcc CoxFe1−x grow along three of the six equivalent <110> directions. However, for grain-like dendritic hcp ε-Co, their six branches grow along the six equivalent <101> directions, and the trunks are oriented preferably along [0002] direction. The electromagnetic absorption (EMA) performance of leaf-like structure CoxFe1−x alloys are obviously enhanced with Co content increase from −21.7 dB for Co0.1Fe0.9 to −59.1 dB for Co0.5Fe0.5. Meanwhile, the response frequency of maximum reflection loss (RL) shifts to the higher band. In the case of grain-like dendritic Co0.9Fe0.1 alloy, it has the widest frequency band from 5 to 18 GHz with RL < −20 dB due to the mixed phase composition. We ascribe the enhancement of dendritic CoxFe1−x alloys' EMA performance to the different elemental compositions, crystalline structures, surface anisotropy and crystal defects, which contribute to enhancing the effective complementarities between dielectric loss and magnetic loss.