The effect of hydroxyl groups and surface area of hematite derived from annealing goethite for phosphate removal

Synthetic goethite and thermally treated goethite at different temperatures were used to remove phosphate from sewage. The effect of annealing temperature on phosphate removal over time was investigated. X-ray diffraction(XRD), transmission electron microscopy (TEM), N2 adsorption and desorption (BET), and infrared emission spectrum (FT-IES) were utilized to characterize the phase, morphology, specific surface area, pore distribution, and the surface groups of samples. The results show that annealed products of goethite at temperatures over 250 °C are hematite with the similar morphology as the original goethite with different hydroxyl groups and surface area. Increasing temperature causes the decrease in hydroxyl groups, consequential increase in surface area at first and then experiences a decrease (14.8–110.4–12.6 m2/g) and the subsequent formation of nanoscale pores. The variation rate of hydroxyl groups and surface area based on FT-IES and BET, respectively, are used to evaluate the effect of annealing temperature on phosphate removal. By using all of the characterization techniques, it is concluded that the changes of phosphate removal basically result from the total variation rate between hydroxyl groups and surface area.

Electrical property and characterization of nano-SnO2/wollastonite composite materials

Nano-tin oxide was deposited on the surface of wollastonite using the mixed solution including stannic chloride pentahydrate precursor and wollastonite by a hydrolysis precipitation process. The antistatic properties of the wollastonite materials under different calcined conditions and composite materials (nano-SnO2/wollastonite, SW) were measured by rubber sheeter and four-point probe (FPP) sheet resistance measurement. Effects of hydrolysis temperature and time, calcination temperature and time, pH value and nano-SnO2 coating amount on the resistivity of SW powders were studied, and the optimum experimental conditions were obtained. The microstructure and surface properties of wollastonite, precipitate and SW were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), specific surface area analyzer (BET), thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier translation infrared spectroscopy (FTIR) respectively. The results showed that the nano-SnO2/wollastonite composite materials under optimum preparation conditions showed better antistatic properties, the resistivity of which was reduced from 1.068 × 104 Ω cm to 2.533 × 103 Ω cm. From TG and XRD analysis, the possible mechanism for coating of SnO2 nanoparticles on the surface of wollastonite was proposed. The infrared spectrum indicated that there were a large number of the hydroxyl groups on the surface of wollastonite. This is beneficial to the heterogeneous nucleation reaction. Through morphology, EDS and XPS analysis, the surface of wollastonite fiber was coated with a layer of 10–15 nm thickness of tin oxide grains the distribution of which was uniform.

Characterization of precursors to methanol synthesis catalysts Cu/ZnO system

The composition of a series of hydroxycarbonate precursors to copper/zinc oxide methanol synthesis catalysts prepared under conditions reported as optimum for catalytic activity has been studied. Techniques employed included thermogravimetry (TG), temperature-programmed decomposition (TPD), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman and FTIR spectroscopies. Evidence was obtained for various structural phases including hydrozincite, copper hydrozincite, aurichalcite, zincian malachite and malachite (the concentrations of which depended upon the exact Cu/Zn ratio used). Significantly, previously reported phases such as gerhardite and rosasite were not identified when catalysts were synthesized at optimum solution pH and temperature values, and after appropriate aging periods. Calcination of the hydroxycarbonate precursors resulted in the formation of catalysts containing an intimate mixture of copper and zinc oxides. Temperature-programmed reduction (TPR) revealed that a number of discrete copper oxide species were present in the catalyst, the precise concentrations of which were determined to be related to the structure of the catalyst precursor. Copper hydrozincite decomposed to give zinc oxide particles decorated by highly dispersed, small copper oxide species. Aurichalcite appeared to result ultimately in the most intimately mixed catalyst structure whereas zincian malachite decomposed to produce larger copper oxide and zinc oxide grains. The reason for the stabilization of small copper oxide and zinc oxide clusters by aurichalcite was investigated by using carefully selected calcination temperatures. It was concluded that the unique formation of an 'anion-modified' oxide resulting from the initial decomposition stage of aurichalcite was responsible for the 'binding' of copper species to zinc moieties.

Confirmation of the assignment of vibrations of goethite: An ATR and IES study of goethite structure

Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM/EDS) and X-ray diffraction (XRD) were used to characterize the morphology of synthetic goethite. The behavior of the hydroxyl/water molecular units of goethite and its thermally treated products were characterized using Fourier transform-infrared emission spectroscopy (FT-IES) and attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy. The results showed that all the expected vibrational bands between 4000 and 650 cm−1 including the resolved bands (3800–2200 cm−1) were confirmed. A band attributed to a new type of hydroxyl unit was found at 3708 cm−1 and assigned to the FeO–H stretching vibration without hydrogen bonding. This hydroxyl unit was retained up to the thermal treatment temperature of 500 °C. On the whole, seven kinds of hydroxyl units, involving three surface hydroxyls, a bulk hydroxyl, a FeO–H without hydrogen bonding, a nonstoichiometric hydroxyl and a reversed hydroxyl were observed, and three kinds of adsorbed water were found in/on goethite.

A nanometre-scale non-periodic structural variation in high temperature superconducting ceramics and the implications for properties

Non-periodic structural variation has been found in the high Tc cuprates, YBa2Cu3O7-x and Hg0.67Pb0.33Ba2Ca2Cu 3O8+δ, by image analysis of high resolution transmission electron microscope (HRTEM) images. We use two methods for analysis of the HRTEM images. The first method is a means for measuring the bending of lattice fringes at twin planes. The second method is a low-pass filter technique which enhances information contained by diffuse-scattered electrons and reveals what appears to be an interference effect between domains of differing lattice parameter in the top and bottom of the thin foil. We believe that these methods of image analysis could be usefully applied to the many thousands of HRTEM images that have been collected by other workers in the high temperature superconductor field. This work provides direct structural evidence for phase separation in high Tc cuprates, and gives support to recent stripes models that have been proposed to explain various angle resolved photoelectron spectroscopy and nuclear magnetic resonance data. We believe that the structural variation is a response to an opening of an electronic solubility gap where holes are not uniformly distributed in the material but are confined to metallic stripes. Optimum doping may occur as a consequence of the diffuse boundaries between stripes which arise from spinodal decomposition. Theoretical ideas about the high Tc cuprates which treat the cuprates as homogeneous may need to be modified in order to take account of this type of structural variation.

Formation of polyaniline/Pt nanoparticle composite films and their electrocatalytic properties

Polyaniline (PANI) thin films modified with platinum nanoparticles have been prepared by several methods, characterised and assessed in terms of electrocatalytic properties. These composite materials have been prepared by the in situ reduction of a platinum salt (K2PtCl4) by PANI, in a variety of solvents, resulting in the formation of platinum nanoparticles and clusters of different sizes. The further deposition of platinum clusters at spin cast thin films of PANI/Pt composites from a neutral aqueous solution of K2PtCl4 has also been demonstrated. Thin-film electrodes prepared from these materials have been investigated for their electrocatalytic activity by studying hydrazine oxidation and dichromate reduction. The properties of the composite materials have been determined using UV–visible spectroscopy, atomic force microscopy and transmission electron microscopy. The nature of the material formed is strongly dependent on the solvent used to dissolve PANI, the method of preparation of the PANI/Pt solution and the composition of the spin cast thin film before subsequent deposition of platinum from the aqueous solution of K2PtCl4.

Synthesis and spectroscopic characterization of magnesium oxalate nano-crystals

Synthesis of MgC2O4⋅2H2O nano particles was carried out by thermal double decomposition of solutions of oxalic acid dihydrate (C2H2O4⋅2H2O) and Mg(OAc)2⋅4H2O employing CATA-2R microwave reactor. Structural elucidation was carried out by employing X-ray diffraction (XRD), particle size and shape were studied by transmission electron microscopy (TEM) and nature of bonding was investigated by optical absorption and near-infrared (NIR) spectral studies. The powder resulting from this method is pure and possesses distorted rhombic octahedral structure. The synthesized nano rod is 80 nm in diameter and 549 nm in length.

Degradation of simazine from aqueous solutions by diatomite-supported nanosized zero-valent iron composite materials

A novel composite material based on deposition of nanosized zero-valent iron (nZVI) particles on acid-leached diatomite was synthesised for the removal of a chlorinated contaminant in water. The nZVI /diatomite composites were characterized by X-ray diffraction, scanning electron microscopy, elemental analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. Compared with the pure nZVI particles, better dispersion of nZVI particles on the surface or inside the pores of diatom shells was observed. The herbicide simazine was selected as the model chlorinated contaminant and the removal efficiency by nZVI /diatomite composite was compared with that of the pristine nZVI and commercial iron powder. It was found that the diatomite supported nZVI composite material prepared by centrifugation exhibits relatively better efficient activity in decomposition of simazine than commercial Fe, lab synthesized nZVI and composite material prepared via rotary evaporation, and the optimum experimental conditions were obtained based on a series of batch experiments. This study on immobilizing nZVI particles onto diatomite opens a new avenue for the practical application of nZVI and the diatomite-supported nanosized zero-valent iron composite materials have potential applications in environmental remediation.

A vibrational spectroscopic study of a hydrated hydroxy-phosphate mineral fluellite, Al2(PO4)F2(OH)·7H2O

Raman and infrared spectra of two well-defined fluellite samples, Al2(PO4)F2(OH)�7H2O, from the Krásno near Horní Slavkov (Czech Republic) and Kapunda, South Australia (Australia) were studied and tentatively interpreted. Observed bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, aluminum oxide/hydroxide/fluoride octahedra, water molecules and hydroxyl ions. Approximate O–H���O hydrogen bond lengths were inferred from the Raman and infrared spectra.

Monoclinic β-MoO3 nanosheets produced by atmospheric microplasma : application to lithium-ion batteries

Porous high surface area thin films of nanosheet-shaped monoclinic MoO 3 were deposited onto platinized Si substrates using patch antenna-based atmospheric microplasma processing. The films were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and electrochemical analysis. The electrochemical analysis shows original redox peaks and high charge capacity, and also indicates a reversible electrochemical behaviour particularly beneficial for applications in Li-ion batteries. SEM shows that the films are highly porous and consist of nanosheets 50-100 nm thick with surface dimensions in the micrometre range. HRTEM reveals that the MoO3 nanosheets consist of the monoclinic beta phase of MoO3. These intricate nanoarchitectures made of monoclinic MoO3 nanosheets have not been studied previously in the context of applications in Li-ion batteries and show superior structural and morphological features that enable effective insertion of Li ions.

Low-temperature assembly of ordered carbon nanotip arrays in low-frequency, high-density inductively coupled plasmas

High-density inductively coupled plasma (ICP)-assisted self-assembly of the ordered arrays of various carbon nanostructures (NS) for the electron field emission applications is reported. Carbon-based nano-particles, nanotips, and pyramid-like structures, with the controllable shape, ordering, and areal density are grown under remarkably low process temperatures (260-350 °C) and pressures (below 0.1 Torr), on the same Ni-based catalyst layers, in a DC bias-controlled floating temperature regime. A high degree of positional and directional ordering, elevated sp2 content, and a well-structured graphitic morphology are achieved without the use of pre-patterned or externally heated substrates.

Visible-light-induced selective photocatalytic oxidation of benzylamine into imine over supported Ag/AgI photocatalysts

Titanate nanotubes (TNT) supported AgI nanoparticles were prepared by a two-step method: the deposition of Ag2O on titanate nanotubes from AgNO3 solution and the subsequent I-adsorption process from NaI solution. It is found that the supported AgI samples exhibited excellent photoactivity for the selective oxidation of benzylamine to the corresponding imine under visible light illumination and the photocatalyst can be used for many times without apparent activity loss. X-ray diffraction studies, transmission electron microscopy, diffuse reflectance UV-Vis spectroscopy and nitrogen adsorption measurements were used for the characterization of the as-prepared and recycled AgI samples. It is found that under visible light irradiation, AgI partially decomposed to produce Ag/AgI nanostructure and thus stabilized. The photoactivity of supported Ag/AgI for the selective oxidation of benzylamine was studied in terms of the light intensity, wavelength, temperature and substituent. It is proposed that the formation of plasmonic Ag nanoparticles should be responsible for the high activity and selectivity.

Synthesis, characterization and activity of an immobilized photocatalyst : natural porous diatomite supported titania nanoparticles

Diatomite, a porous non-metal mineral, was used as support to prepare TiO2/diatomite composites by a modified sol–gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 _C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti–O–Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO2/diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation. The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir–Hinshelwood model. The preferable removal efficiency was observed in composites by 750 _C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10.

Graphene-type sheets of Nb1-xWxS2 : synthesis and in situ functionalization

Enlightened by the discovery of graphenes, a variety of inorganic analogues have been synthesized and characterized in recent years. Solvated Nb1-xWxS2 analogues of graphene-type sheets were prepared by lithiation and exfoliation of multistacked Nb1-xWxS2 coin roll nanowires (CRNWs), followed by in situ functionalization with gold nanoparticles to synthesize gold-loaded Nb1-xWxS2/Au nanocomposites. The Nb1-xWxS2 nanosheets and the corresponding Nb1-xWxS2/Au nanocomposites were characterized by high resolution electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM), dynamic light scattering (DLS) and scanning force microscopy (AFM). The graphene-type sheets are stable in water and other solvents and can be functionalized similarly as chalcogen-terminated surfaces (e.g. with Au nanoparticles).

N,N'-Carbonyldiimidazole-mediated functionalization of superparamagnetic nanoparticles as vaccine carrier

Particulates with specific sizes and characteristics can induce potent immune responses by promoting antigen uptake of appropriate immuno-stimulatory cell types. Magnetite (Fe3O4) nanoparticles have shown many potential bioapplications due to their biocompatibility and special characteristics. Here, superparamagnetic Fe3O4 nanoparticles (SPIONs) with high magnetization value (70emug-1) were stabilized with trisodium citrate and successfully conjugated with a model antigen (ovalbumin, OVA) via N,N'-carbonyldiimidazole (CDI) mediated reaction, to achieve a maximum conjugation capacity at approximately 13μgμm-2. It was shown that different mechanisms governed the interactions between the OVA molecules and magnetite nanoparticles at different pH conditions. We evaluated as-synthesized SPION against commercially available magnetite nanoparticles. The cytotoxicity of these nanoparticles was investigated using mammalian cells. The reported CDI-mediated reaction can be considered as a potential approach in conjugating biomolecules onto magnetite or other biodegradable nanoparticles for vaccine delivery.