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A simple and eco-friendly approach was used to prepare α-Fe2O3@graphene oxide (α-Fe2O3@GO) nanocomposites with different iron oxide content in lower temperature. The nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption techniques. The results show that α-Fe2O3 nanoparticles with particle sizes of 60–100 nm are uniformly anchored on the surface of GO nanosheets at lower hydrothermal reaction. The specific surface area of α-Fe2O3@GO (114.57 m2/g) was about threefold larger than that of pure iron oxide (33.37 m2/g). Moreover, α-Fe2O3@GO nanocomposites with optimal mass ratio (8:1) between iron oxide and GO, which exhibited enhanced response to 100 ppm ethanol (14.82) in comparison with pure α-Fe2O3 (3.48) at 260 °C. The improved sensitive performance is in contact with larger surface area and incremental active sites in interface owing to introducing GO. The results reveal that GO is crucial to improve gas sensing performance.

ZnSnO3 hollow microspheres were synthesized by a simple one-pot template-free and general in-situ precipitation method combined with subsequent dehydration treatment. The prepared ZnSnO3 hollow microspheres were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the thermogravimetric-differential scanning calorimetry analysis (TG-DSC). The results showed that ZnSnO3 hollow microspheres with diameter ranging from 1.3 to 1.6 μm were constructed by small nanoparticles with diameter of about 70 nm. The investigation on the evolution formation revealed that the orientation and morphology of the products were carefully controlled by adjusting the amount of the addition of NaOH and the growth time, and a possible formation mechanism of the hollow structure was proposed. Moreover, the as-fabricated sensors based on the ZnSnO3 hollow microspheres showed superior gas-sensing properties for the detection of ethanol than ZnSnO3 solid spheres and can detect ethanol in the real life.

Fe3O4-TiO2 heterostructures were synthesized through co-precipitation method based on TiO2 nanobelts. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometry (VSM) were used to characterize the heterostructure nanocomposites. The results of XRD proved that the TiO2 nanobelt was anatase which was the most suitable crystal form for photocatalysis. SEM and TEM analysis indicated that Fe3O4 nanoparticles were adhere to TiO2 nanobelts which have one-dimensional structure with 100–200 nm in width. The VSM measurements showed that the photocatalyst can be easily recovered by an extemal magnetic field. X-ray photoelectron spectroscopy (XPS) of Ag@Fe3O4-TiO2 nanocomposites studies confirm that Ag is in Ag0 state. Finally, the photodegradation of rhodamine B (RhB) by the obtained magnetic photocatalyst was investigated via UV–vis absorption spectra. The photocatalytic activity of the composites was observed to be lower compared to bare TiO2 due to the higher degree of recombination reactions after combined with Fe3O4 nanoparticles. After coated the composite of 15% Fe3O4-TiO2 with Ag, the new nanocomposite of Ag@Fe3O4-TiO2 can be easily recovered after photocatalysis by an extemal magnetic field and showed enhanced photocatalytic activity. The mechanisms for the exhibited enhanced photocatalytic effect of Ag nanoparticle decorated Fe3O4-TiO2 nanocomposites with surface heterostructures are discussed.

The nanocomposites of g-C3N4 supported by Fe3O4 nanoparticles (Fe3O4/g-C3N4) have been fabricated through a simple hydrothermal route in a water–ethanol system. The nanocomposites were characterized by X-ray diffraction, and transmission electron microscopy, Fourier transform infrared, and thermogravimetric analysis, respectively. The results showed that g-C3N4 nanosheets were decorated randomly by Fe3O4 nanoparticles with average diameters of 7 nm. The photocatalytic activities were evaluated in terms of the efficiencies of photodecomposition of Rhodamine B in aqueous solution under visible light illumination. The as-synthesized Fe3O4/g-C3N4 nanocomposites showed unprecedented photodecomposition efficiency compared with pure g-C3N4 under visible-light. The Fe3O4/g-C3N4 nanocomposites with improved photocatalytic activities would have a great potential in removing organic dyes from polluted water.

A kind of novel ZnSnO3/SnO2 hollow urchin nanostructure was synthesized by a facile, eco-friendly two-step liquid-phase process. The structure, morphology, and composition of samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. The results revealed that many tiny needle-like SnO2 nanowires with the average diameter of 5 nm uniformly grew on the surface of the ZnSnO3 hollow microspheres and the ZnSnO3/SnO2 hollow urchin nanostructures with different SnO2 content also were successfully prepared. In order to comprehend the evolution process of the ZnSnO3/SnO2 hollow urchin nanostructures, the possible growth mechanism of samples was illustrated via several experiments in different reaction conditions. Moreover, the gas-sensing performance of as-prepared samples was investigated. The results showed that ZnSnO3/SnO2 hollow urchin nanostructures with high response to various concentration levels of acetone enhanced selectivity, satisfying repeatability, and good long-term stability for acetone detection. Specially, the 10 wt% ZnSnO3/SnO2 hollow urchin nanostructure exhibited the best gas sensitivity (17.03 for 50 ppm acetone) may be a reliable biomarker for the diabetes patients, which could be ascribed to its large specific surface area, complete pore permeability, and increase of chemisorbed oxygen due to the doping of SnO2.