B. Hannoyer

MOF derived porous carbon–Fe3O4 nanocomposite as a high performance, recyclable environmental superadsorbent

A high surface area carbon composite with Fe3O4 nanoparticles is synthesized by pyrolysis of an iron containing Metal Organic Framework (MOF). The composite can be prepared by annealing the MOF at different temperatures (500 °C and 600 °C), each case exhibiting unique properties in terms of the hydrophobic behaviour and surface area, resulting in specific applicability domains. We highlight the exceptional behaviour of this material as a magnetically separable and recyclable superadsorbent for removal and recovery of environmental pollutants (oil/hydrocarbon and dye/phenol).

From graphite oxide to highly water dispersible functionalized graphene by single step plant extract-induced deoxygenation†

We report a single step facile synthesis of highly water dispersible functionalized graphene nanosheets by plant extract-induced deoxygenation of graphite oxide (GO). The results of various characterizations reveal that the properties of such plant extract-converted graphene nanosheets (PCGN) are comparable to chemically converted graphene nanosheets (CCG). These results open a green route to the emerging graphene-based technologies.

Cu2O/ZnO hetero-nanobrush: hierarchical assembly, field emission and photocatalytic properties

Zinc oxide (ZnO) nanorods are grown hierarchically on cuprous oxide (Cu2O) nanoneedles to form a Cu2O/ZnO hetero-nanobrush assembly. This increases the overall aspect ratio, which helps to enhance the field emission properties of the system. Also, the charge separation and transport are facilitated because of the multiple p–n junctions formed at p-Cu2O/n-ZnO interfaces and quasi-1-D structures of both the materials, respectively. This helps to significantly enhance the photocatalytic properties. As compared to only Cu2O nanoneedles, the Cu2O/ZnO hetero-nanobrush shows excellent improvement in both field emission and photocatalytic applications.

Formation and characterization of the solid solutions (CrxFe1−x)2O3, 0⩽x⩽1

The solid solutions (CrxFe1−x)2O3, 0 ⩽ x ⩽ 1, were prepared by traditional ceramic procedures. The samples were characterized using X-ray diffraction, Mössbauer, Fourier transform infra-red (FT-IR) and optical spectroscopic measurements. In the whole concentration range two phases exist phase F, α-(CrxFe1−x)2O3, which is isostructural with α-Fe2O3 and phase C, which is closely related to Cr2O3. Phase F exists in samples heated up to 900°C, for 0 ⩽ x ≲ 0.95. Phase C exists from x≳0.27 to x=1 for samples heated up to 900°C and from x≳0.65 to x=1 for samples heated up to 1200 °C. For samples heated up to 900 °C, the solubility limits were 27.5 ± 0.5 mol% of Cr2O3 in α-Fe2O3 and 4.0 ± 0.5 mol % of α-Fe2O3 in Cr2O3. For the samples heated at 1200 °C the diffraction peaks for the F and C phases in the two phase region were severely overlapped and thus the solubility limits could not be determined accurately as for previous samples. 57Fe Mössbauer spectra of the samples heated up to 1200 °C showed significant broadening of spectral lines and a gradual decrease of the hyperfine magnetic field with increase of x up to 0.50. For x≳0.7, a paramagnetic doublet with collapsing sextet was observed. The spectra were interpreted in terms of an electronic relaxation effect; however, an agglomeration of iron ions which would contribute to the superparamagnetic effect could not be excluded. The FT-IR spectra showed transition effects in accordance with the X-ray diffraction results. The most intense absorption bands, observed for the samples heated up to 1200 °C, were located at ∼ 460 and 370 nm (22 000 and 27 000cm−1) for x⩾ 0.5, ∼500 and 360 nm for x < 0.3, and might be correlated with the strong enhancement of the pair transitions through antiferromagnetic interactions. The intensification of the 6A1 → 4T1 Fe3+ ions in all spectra and the development of the absorption at 13000 cm−1 due to a metal-metal charge transfer (Cr3+ → Fe3+) transition, might be explained by exchange coupling which has been observed in some spinel compounds.

Magnetite/CdTe magnetic?fluorescent composite nanosystem for magnetic separation and bio-imaging

A new synthesis protocol is described to obtain a CdTe decorated magnetite bifunctional nanosystem via dodecylamine (DDA) as cross linker. High resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDAX), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and fluorescence microscopy are used to characterize the constitution, size, composition and physical properties of these superparamagnetic-fluorescent nanoparticles. These CdTe decorated magnetite nanoparticles were then functionalized with anti-epidermal growth factor receptor (EGFR) antibody to specifically target cells expressing this receptor. The EGFR is a transmembrane glycoprotein and is expressed on tumor cells from different tissue origins including human leukemic cell line Molt-4 cells. The magnetite-CdTe composite nanosystem is shown to perform excellently for specific selection, magnetic separation and fluorescent detection of EGFR positive Molt-4 cells from a mixed population. Flow cytometry and confocal laser scanning microscopy results show that this composite nanosystem has great potential in antibody functionalized magnetic separation and imaging of cells using cell surface receptor antibody.

Ferritization of copper ions in the Cu–Fe–O system

Abstract Ferrite ceramics were prepared utilizing solid state reactions between CuO and Fe 3 O 4 or α-Fe 2 O 3 . The samples were analyzed with X-ray diffraction, 57 Fe Mossbauer and FT-IR spectroscopies. For the solid state reaction between CuO and Fe 3 O 4 , the initial atomic ratios of Cu:Fe varied between 1:299 and 1:2. With an increase in the amount of CuO in the initial reaction mixture, there was a corresponding increase in cuprospinel (cubic CuFe 2 O 4 ) in the final products of the synthesis. For the initial molar ratio of Cu:Fe=1:2, cuprospinel phase (0.85) and CuFeO 2 phase (0.15) were found by XRD, as the result of solid state reaction between CuO and Fe 3 O 4 . In this sample, a small amount of CuO was also detected. For the solid state reaction between CuO and α-Fe 2 O 3 , the initial molar ratio of 1:1 was used. The samples prepared at a maximum temperature of 800°C, contained similar fractions of tetragonal and cubic CuFe 2 O 4 phases, and also minor phases of CuO and α-Fe 2 O 3 as found by XRD. In the samples prepared at between 1000 and 1350°C, the cubic CuFe 2 O 4 phase was found together with small amounts of CuFeO 2 and CuO. Mossbauer spectra showed hyperfine field distributions and on the basis of these spectra, calculated parameters, the possible presence of Cu + and Fe 2+ ions in the samples was discussed. For the samples prepared at 1350°C the FT-IR spectrum suggested a significant increase in Fe 2+ ions, whereas the Mossbauer spectrum and calculated parameters were similar to those for the compound Cu 0.7 Fe 2.3 O 4 .

Atmospheric corrosion of nickel in various outdoor environments

As part of a field exposure program in the north-west of France on atmospheric corrosion of metal and alloys, this study presents the results of the behaviour of nickel panels exposed in industrial, urban and rural atmospheres. Mass measurements were investigated during the exposure and adherent corrosion layers were followed by means of several methods of analysis: Fourier transform infrared reflection–absorption spectroscopy, X-ray diffraction and scanning electron microscopy with X-ray microanalysis. In order to determine all the chemical species formed in the corrosion layers, corrosion products released from the surface by rainfall were also studied by collecting the streaming water from the nickel surfaces. Anionic and cationic quantities in the streaming water were determined respectively with ionic chromatography and polarography. The nickel attack appears as a pitting corrosion process accompanied by the formation of soluble corrosion products in dry exposure periods, these being regularly dissolved by rainfall events. Pits are associated with the formation of nickel salts, mainly sulphates and chlorides with small amounts of nitrate, and surrounded by carbonate species. The corrosion rate increases from rural to industrial areas.

Simultaneous copper runoff and copper surface analysis in an outdoor area

Simultaneous copper runoff and copper surface analysis has been performed during a field exposure in a French industrial area. Corrosion layer composition was studied with fourier transform infrared reflection-absorption spectroscopy, x-ray diffraction and scanning electron microscopy with energy-dispensive scattering analysis, revealing cuprite, basic copper sulphates (brochantite and posjnakite) and copper sulphate pentahydrate (CuSO 4 .5H 2 O) as the main corrosion products after 3 months of exposure. In order to determine the soluble corrosion compounds carried with rain, the water streaming over a copper coupon was collected and analysed by means of ionic chromatography and potentiometric stripping analysis. Significant sulphate and copper concentrations were detected in water and interpreted as resulting from the dissolution of copper sulphate compounds.

Caracterisation d'oxydes de cuivre par spectrometrie d'absorption X

Abstract The devolopment of new physical methods as photoelectron spectroscopy (ESCA), X-ray emission and absorption spectroscopies is needful to characterize the chemical bonding in materials like Cu 0.5 Fe 2.5 O 4 and CuMn 2 O 4 . The K-absorption edges of copper in oxides CuMO 2 and CuM 2 O 4 have been studied with a view to further analytical applications.

Thermal behaviour of gamma manganese dioxide: I. Structural evolution

Abstract The crystallographic structure of γ-MnO 2 is an important factor of its electrochemical reactivity in primary battery cathods. In order to characterize two industrial samples (EMD and CMD), the structural evolution induced by static thermal treatment in air up to 450°C has been studied using FTIR spectroscopy in diffuse reflectance and EXAFS spectroscopy. Diffuse reflectance FTIR spectra, which can not be correlated to transmittance spectra, show that γ-MnO 2 samples are progressively transformed into β-MnO 2 with increasing temperature, but that increasing treatment duration at 450°C of up to 60 days does not allow to complete it. EXAFS spectroscopy allows to describe quantitatively the short-range order in such poorly crystallized compounds, and give precise informations on the breadth of the “tunnels” of the structure, which plays a significant part in proton insertion.