Assembled and isolated Bi5O7I nanowires were fast prepared through an aqueous strategy without further complex treatment. Powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV-vis diffuse reflectance spectroscopy (DRS) were used to characterize the obtained samples and reveal the evolution process of Bi5O7I nanomaterials. The formation of a hierarchical BiOI precursor and fast substitution of I− with OH− facilitated the evolution of assembled Bi5O7I architectures, while isolated Bi5O7I nanowires were obtained by shortening the existence time of BiOI crystals on the basis of assembled Bi5O7I nanowires. HRTEM results revealed similar crystalline orientations of nanowires along the [010] direction for the assembled and isolated Bi5O7I nanowire samples. And the nanowires in an assembled sample also exhibited a superlattice-like structure with a periodicity of 0.84 nm. On comparison to the BiOI precursor, the Bi5O7I nanowires with different assembly-styles all displayed good photocatalytic activities on the degradation of rhodamine B (RhB) dye and colorless bisphenol-A (BPA) under visible-light irradiation. The photocatalytic efficiency reached 96% in 3 h for RhB and 90% in 4 h for BPA in the degradation system at pH = 7. The assembled nanowire samples showed even better photocatalytic activities on the degradation of model organic pollutants relative to the isolated nanowire samples. Band structures and trapping experiments were studied to reveal the degradation mechanism over Bi5O7I nanowire samples. It was proposed that a valid separation of photogenerated electrons and holes and appropriate valence and conduction band positions of Bi5O7I nanowires led to good visible-light-induced catalytic properties.

Three-dimensional (3D) Co3O4 nanoclusters were fabricated with the assistance of tetrasodium ethylene diamine tetraacetic acid (EDTANa4) through a one-pot wet-chemical reaction, featuring self-limiting assembly of building blocks and controlled regrowth process. The molar ratio of Co2+ and EDTANa4 plays a key role in building initial clusters as blocks, and the amount of NaOH effects the regrowth process. A possible formation mechanism for the Co3O4 nanoclusters was proposed based on the characterization results of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The designed hierarchical Co3O4 nanoclusters exhibit a high specific capacitance of 221 F g−1 at a current density of 2 A g−1 in 2 mol L−1 KOH electrolyte.Download high-res image (116KB)Download full-size image

•Flowerlike Co3O4 nanostructures were prepared with the assistance of Na3Cit·2H2O.•The [Co2(LH-1)2]4−complex acts as soft-template and reactant source.•Co3O4 nanostructures were obtained through [Co2(CitH−1)2]4− → Co(OH)2 → Co3O4 process.•The synthesized flowerlike Co3O4 nanostructures have good catalytic activity.Flowerlike hierarchical Co3O4 nanostructures were prepared by wet-chemical method with the assistance of trisodium citrate (Na3Cit·2H2O) under mild conditions. The phase, structure, morphology and properties of the Co3O4 nanostructures were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and UV–visible spectrophotometer. Substitution-oxidation ([Co2(CitH−1)2]4− → Co(OH)2 → Co3O4) process was proposed for the possible evolution mechanism based on the results. Appropriate Na3Cit played an important role for the formation of flowerlike Co(OH)2 intermediates and Co3O4 nanostructures. The obtained flowerlike hierarchical Co3O4 nanostructures exhibited remarkable enhanced visible-light photocatalytic degradations of rhodamine B (RhB) and catalytic decomposition of ammonium perchlorate (AP).Download high-res image (201KB)Download full-size image

An aqueous reduction method was reported for the synthesis of bismuth nanowires (Bi NWs) 5–10 nm in diameter and several micrometers in length under the guidance of PVP molecules. The reactions were performed at 80 °C by reducing bismuth chloride with sodium hypophosphite first in acid and then under neutral circumstances. The key to successful preparation of the Bi NWs is regulation of the reduction speed by control of the pH value. The morphology evolution of the samples was also found to have a strong dependence on the reaction parameters, including the introduction amount and molecular weight of PVP molecules. A solid–solution–solid (SSS) mechanism was proposed for the nucleation and growth of Bi NWs in our strategy. The as-prepared Bi NWs exhibit excellent visible-light photocatalytic activities for the degradation of the organic pollutant Rhodamine B (RhB) and colorless bisphenol A (BPA). The good recyclability of the Bi NWs on RhB photodegradation demonstrates the possibility of their practical applications.