Fe, Co, and Ni ultrafine particles (UFP) were prepared by a gas evaporation method in an inert atmosphere. The different preparing conditions of the Fe, Co, and Ni UFP included inert gas pressures and kinds were investigated by means of x-ray diffraction, transmission electron microscopy (TEM), and magnetic measurements with low or high temperatures. The experimental results show that coercivities Hc of the Fe, Co, and Ni UFP, depending on particle sizes, obey a single-domain theory. The maximum Hc was 450, 1000, and 1500 Oe, respectively, for Ni (310 Å), Fe (210 Å), and Co (200 Å) at room temperature. The coercivities came up to high in the low temperatures. The saturation magnetizations Ms of the Fe, Co, and Ni UFP decreased with small particle sizes. A face-centered structure of Co UFP (200–300 Å) was confirmed by x-ray diffraction. Some Fe UFP in the shape of balls (200–400 Å) observed in the TEM may be an amorphous structure.

BiOBr containing surface oxygen vacancies (OVs) was prepared by a simple solvothermal method and combined with graphitic carbon nitride (g‐C3N4) to construct a heterojunction for photocatalytic oxidation of nitric oxide (NO) and reduction of carbon dioxide (CO2). The formation of the heterojunction enhanced the transfer and separation efficiency of photogenerated carriers. Furthermore, the surface OVs sufficiently exposed catalytically active sites, and enabled capture of photoexcited electrons at the surface of the catalyst. Internal recombination of photogenerated charges was also limited, which contributed to generation of more active oxygen for NO oxidation. Heterojunction and OVs worked together to form a spatial conductive network framework, which achieved 63 % NO removal, 96 % selectivity for carbonaceous products (that is, CO and CH4). The stability of the catalyst was confirmed by cycling experiments and X‐ray diffraction and transmission electron microscopy after NO removal.

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We have developed an efficient strategy for synthesizing a strongly coupled Au/Fe3O4/GO hybrid material to improve the catalytic activity, stability, and separation capability of Au nanoparticles (NPs) and Hg(2+). The hybrid material can be synthesized by the direct anchoring of Au and Fe3O4 NPs on the functional groups of GO. This approach affords strong chemical attachments between the NPs and GO, allowing this hybrid material to ultrasensitively detect Hg(2+) in aqueous solutions with a detection limit as low as 0.15 nM. In addition, the deposition of Hg(0) on the surface of Au/Fe3O4/GO could be quickly (within 30 min) and efficiently (>99% elimination efficiency) removed by the simple application of an external magnetic field and then Au/Fe3O4/GO could be subsequently reused at least 15 times, with the elimination efficiency remaining high (>96%).