Fe-doped tin dioxide nanoparticles SnO2:Fe (x%) with x ranging from 0 to 20 were elaborated by a performed hydrothermal method. A deep structural study on the obtained nanoparticles was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The XRD measurements revealed that the rutile structure of the SnO2 was kept even for high iron concentrations. It is also observed that when iron amount increases the grain size decreases and the band gap is obviously red shifted. HRTEM imaging shows a good crystallinity of the elaborated NPs and confirm the grain size magnitude deduced from XRD measurements. The Raman modes associated to ferric phases are absent in the Fe-doped spectra which is in agreement with the XRD and HRTEM results proving the formation of SnO2:Fe solid phase. The Raman A1g mode seems to be strongly affected by the morphology transformation undergone by SnO2 NPs and by the induced local symmetry break when introducing iron. Forbidden Raman phonon modes were detected and an enhancement of the (110) surface oxygen bridging seems to follow the iron doping. This latter structural feature seems to present a major contribution to the notable enhancement of hydroxyl groups’ adsorption on the Fe-doped SnO2 surface. The variation of the Urbach energy Eu with Fe amount is discussed and is found to be in accordance with the different interpretations. The PL spectra reveals that the UV-violet band of the SnO2 NPs was affected by iron presence and the induced non-systematic variation of this emission was discussed. A decrease in visible emission was noted when introducing iron revealing that Fe doping affects the density of singly charged oxygen vacancies.

Iron-doped tin oxide nanoparticles (Fe-doped SnO2 NPs), with different iron concentrations, were hybridized with reduced graphene oxide (rGO) through a three steps elaboration method to obtain Fe-doped SnO2/rGO nanocomposite. It was observed that the rutile structure of SnO2 is maintained even for high amounts of iron, as revealed by the X-ray diffraction (XRD) patterns that also indicated the reduction of the graphene oxide after the thermal treatment. Transmission electron microscopy (TEM) observations showed a uniform loading of the Fe-doped SnO2 NPs on the rGO sheets. The behavior of the absorbance, Fourier transform Infrared Spectroscopy (FTIR) and X-ray photoelectron emission (XPS) spectra of the as-synthesized Fe-doped SnO2/rGO composite further highlighted the reduction of GO during the preparation of the main heterostructure. The Raman spectroscopy revealed that both the intensity and the broadening of the G and D bands were affected by iron amount, suggesting a high interaction between the two components of the heterostructure. The photocatalytic efficiency of the elaborated nanocomposite was evaluated through the photodegradation of rhodamine B (RhB) under visible irradiation. It was found that the efficiency depended both on Fe concentration and GO amount. The experiments showed that 93% of RhB can be eliminated by the Fe-doped SnO2/rGO nanocomposite during the photocatalytic process. The photo-response of the Fe-doped SnO2/rGO seems to be the result of a synergistic effect between the two components of the main nanocomposite. Actually, in a first step, iron doping allows the photo-generation of electron-hole pairs from SnO2 NPs under visible irradiation, then, the excited electrons are trapped by the rGO sheets, which enhances the charge separation ability and further confirms the utility of such doped SnO2/rGO hybrids for photocatalytic applications. The reusability experiment for the elaborated composite was also carried out and the obtained results reveals a high cycling performance of the Fe-doped SnO2/rGO heterostructure even under sunlight irradiation.

Spinel Co2SnO4 nanoparticles are synthesized by a facile hydrothermal route in alkaline solution using SnCl4 and CoCl2 as precursors. The structure, morphology and chemical composition of the nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The catalytic performance of the Co2SnO4 nanoparticles is thoroughly evaluated for peroxymonosulfate (PMS) activation for removal of rhodamine B (RhB) and pentachlorophenol (PCP) from water. The influence of different process parameters on the RhB degradation efficiency is examined and the catalytic stability is evaluated. Under optimized conditions, the Co2SnO4/PMS system is very efficient with a full degradation of RhB and PCP in less than 10 min at room temperature, as revealed by high performance liquid chromatography (HPLC) analysis. Quenching experiments suggested that sulfate radicals (SO4˙-) are the main active species in the degradation process. Moreover, the Co2SnO4 catalyst is stable without any apparent activity loss after 5 cycling runs.

Water contamination with synthetic dyes and metal ions is an escalating problem, despite the huge research efforts put in the field of water treatment. The paper reports on one-step synthesis of reduced graphene oxide-cobalt oxide nanoparticles (rGO-Co3O4) nanocomposite under mild conditions. The nanocomposite material has been characterized using various analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, UV–visible spectrophotometry and Fourier-transform infrared (FTIR) spectroscopy. The catalytic properties of the nanocomposite were demonstrated for the sodium borohydride-induced 4-nitrophenol reduction to 4-aminophenol. A full reduction has been achieved within less than 1min at room temperature. Further, the nanocomposite was successfully applied for Cr(VI) adsorption with a maximum adsorption capacity of 208.8mg.g−1, which is much higher than that obtained using many other magnetic adsorbents. Finally, the nanocomposite was found to be very efficient for anionic and cationic dye adsorption with complete removal within less than 2min. The performance of the rGO-Co3O4 nanocomposite is quite high as compared to other graphene-based adsorbents. The ferromagnetic properties of the composite allowed effective separation and recyclability of the material by simple application of an external magnet.

Nanocrystalline highly Fe-doped SnO2 thin films were prepared using a new simple sol-gel method with iron amounts of 5, 10, 15 and 20%. The obtained gel offers a long durability and high quality allowing to reach a sub-5 nm nanocrystalline size with a good crystallinity. The films were structurally characterized through X-ray diffraction (XRD) that confirms the formation of rutile SnO2. High Resolution Transmission Electron Microscopy (HRTEM) images reveals the good crystallinity of the nanoparticles. Raman spectroscopy shows that the SnO2 rutile structure is maintained even for high iron concentration. The variation of the PL intensity with Fe concentration reveals that iron influences the distribution of oxygen vacancies in tin oxide. The optical transmittance results indicate a redshift of the SnO2 band gap when iron concentration increases. The above optical results lead us to assume the presence of a compensation phenomenon between oxygen vacancies and introduced holes following Fe doping. From current-voltage measurements, an inversion of the conduction type from n to p is strongly predicted to follow the iron addition. Electrical characterizations of SnO2: Fe/p-Si and SnO2: Fe/n-Si heterojunctions seem to be in accordance with this deduction. The quantum tunneling mechanism is expected to be important at high Fe doping level, which was confirmed by current-voltage measurements at different temperatures. Both optical and electrical properties of the elaborated films present a particularity for the same iron concentration and adopt similar tendencies with Fe amount, which strongly correlate the experimental observations. In order to evaluate the applicability of the elaborated films, we proceed to the fabrication of the SnO2: Fe/SnO2 homojunction for which we note a good rectifying behavior. (C) 2017 Elsevier B.V. All rights reserved.

Nickel oxide nanoparticles were grafted on reduced graphene oxide via simultaneous reduction of graphene oxide and nickel salt in a single step reaction. The synthesized material (rGO/NiO) was found to be efficient visible light active photocatalyst for the reduction of nitroaromatic derivatives to their corresponding amino compounds. Hydrazine monohydrate provided necessary protons and electrons for the targeted reaction. After completion of the reaction, the photocatalyst could readily be recovered by simple external magnet and could be reused for six runs without any significant loss of its activity. More importantly, the photocatalyst did not show any leaching during the reaction as confirmed by ICP-AES analysis of the recovered catalyst. (C) 2017 Elsevier B.V. All rights reserved.

Highly iron-doped tin dioxide nanoparticles (Sn1-xFexO2 NPs), with x varying from 0 to 0.2, were prepared by simple hydrothermal method. X-ray diffraction (XRD) patterns indicate that Sn1-xFexO2 NPs crystallize in the tetragonal rutile-like structure. High-resolution transmission electron microscopy (HRTEM) observations did not show any modification of the SnO2 lattice parameters with Fe addition. Mossbauer spectroscopy indicated Sn4+ substitution by Fe3+ and Fe' ions. It was found that iron addition induced high tunable band gap of SnO2 NPs. Photoluminescence (PL) spectra evidenced an improvement of SnO2 crystallinity after Fe introduction. All the results are consistent with the fact that Fe is strongly soluble in SnO2 host. Finally, the photocatalytic efficiency of Sn1-xFexO2 NPs was examined for the degradation of rhodamine B in aqueous solution under visible light irradiation. We show that Fe4+ and Fe3+ ions play a key role in the improvement of the photocatalytic efficiency. (C) 2016 Elsevier Ltd. All rights reserved.

Ag@AgCl/Zn2SnO4 (ZTO) nanocomposites were successfully prepared by a hydrothermal method.

A facile and efficient one-step hydrothermal approach for the synthesis of Zn2SnO4 nanoparticles/reduced graphene oxide (ZTO/rGO) nanocomposites using zinc acetate, tin chloride and graphene oxide (GO) as precursors, and sodium hydroxide as reducing agent has been developed. This approach allows simultaneous reduction of GO and growth of spinel ZTO nanoparticles (NPs) on the rGO sheets. The morphology and microstructure characterizations of ZTO/rGO nanocomposites revealed that this method leads to close interfacial contact of ZTO NPs and rGO and efficient dispersion of ZTO NPs on the surface of rGO sheets. The photocatalytic activity of the ZTO/rGO nanocomposite was investigated for the reduction of rhodamine B under visible light irradiation. Compared to pure ZTO NPs, ZTO/rGO nanocomposite exhibited superior photocatalytic activity with a full degradation of rhodamine B within 15min. The enhanced photocatalytic performance of ZTO/rGO was mainly attributed to excellent electron trapping and effective adsorption properties of rGO.

Na doped ZnO nanocrystals (NCs) were successfully produced by sol-gel process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HRTEM), Raman scattering, UV-vis diffuse reflectance spectroscopy and photoluminescence (PL). XRD analysis indicated that all the prepared samples present pure hexagonal wurtzite structure without any Na related phases. The lattice distortion, calculated using Williamson hall equation, induces stress and a reduction of NCs size from 71.4 to 24.5 nm. TEM images showed NCs with hexagonal shape and a rather uniform size distribution. The selected area electron diffraction (SAED) patterns confirmed the high crystal quality along the (101) direction and is consistent with the hexagonal wurtzite structure of ZnO. The Raman spectra are dominated by E-2(high) mode of ZnO. High Na doping shows the occurrence of anomalous local vibrational Raman modes close to 270 and 513 cm(-1) that are related to intrinsic host lattice defects and distortion, respectively. Optical band gap was found to vary with Na content. Photoluminescence (PL) spectra indicate the presence of a high density of defects in ZnO NCs which are mainly oxygen vacancies. Finally, the obtained NCs were used as a photocatalyst to degrade Rhodamine B (RhB) in solution, under solar irradiation. Na doping enhances the photocatalytic activity of ZnO NCs till an optimum concentration of 0.5% where a full degradation was observed after 120 min of sun light irradiation. Furthermore, this sample presents a good cycling stability and reusability. Based on scavangers test, it was found that both superoxide and hydroxyl oxidizing radicals are mainly actives. (C) 2016 Elsevier B.V. All rights reserved.