Hierarchical Spherical Structure Research Articles

Copper-doped bismuth oxychloride nanosheets assembled into sphere-like morphology for improved photocatalytic inactivation of drug-resistant bacteria

The devastating microbiological contamination as well as emerging drug-resistant bacteria has posed severe threats to the ecosystem and public health, which propels the continuous exploitation of safe yet efficient disinfection products and technology. Here, copper doping engineered bismuth oxychloride (Cu-BiOCl) nanocomposite with a hierarchical spherical structure was successfully prepared. It was found that due to the exposure of abundant active sites for the adsorption of both bacteria cells and molecular oxygen in the structure, the obtained Cu-BiOCl with nanosheets assembled into sphere-like morphology exhibited remarkable photocatalytic antibacterial effects. In particular, compared to the pure BiOCl, composite Cu-BiOCl possessed improved antibacterial effects against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Methicillin-resistant Staphylococcus aureus (MRSA). The combination of physicochemical characterizations and theoretical calculations has revealed that copper doping significantly promoted the light absorbance, inhibited the recombination of electron-hole pairs, and enhanced molecular oxygen adsorption, which resulted in more generation of active species including reactive oxygen species (ROS) and h+ to achieve superior photocatalytic bacterial inactivation. Finally, transcriptome analysis on MRSA pinpointed photocatalytic inactivation induced by Cu-BiOCl may retard largely the development of drug-resistance. Therefore, the built spherical Cu-BiOCl nanocomposite has provided an ecofriendly, economical and robust strategy for the efficient removal of drug-resistant bacteria with promising potentials for environmental and healthcare utilizations.

In situ composite NiCoO2 sphere of nanosheets on wood chip for supercapacitor

The low electrical conductivity of nickel–cobalt layered oxides and single Ni, Co metal oxides led to the low rate capability and poor cycling stability, which thus limits the commercial application in practical supercapacitor. Here, NiCoO2/WCC composite electrode materials were prepared by employing wood chips carbon (WCC) with the high specific surface area and low cost as the conductive layer, where hierarchical spherical structure of laminar NiCoO2 interspersed as homogeneous and was oriented and constructed on the surface of carbon by hydrothermal and calcination. The strategy provided abundant frameworks and active sites for the in situ growth of NiCoO2, which prevented the aggregation of spherical structures to a certain extent; furthermore, the layered spherical structure exposed more active sites, which thus enhanced the electrochemical performance of the capacitor. The NiCoO2/WCC electrode (RNi:Co = 1) possessed a high specific capacitance of 1053.6 F g−1 at 0.5 A g−1 due to the synergistic effect between the bimetallic oxide and WCC, and the specific capacitance of the electrode remained 906 F g−1 even at a high current density of 10 A g−1 by the lamellar structure with more electrochemical sites. In addition, the asymmetric supercapacitor based on the NiCoO2/WCC cathode and the WCC anode delivers a high specific capacitance of 134.4 F g−1 at 1 A g−1, a high specific energy of 36.6 Wh kg−1 at 1 A g−1, and good cycling performance (~ 94.3% retention after 5000 cycles), where the above properties were superior to existing and similar electrode materials.

Oxygen Vacancies Enhance Lithium‐Ion Storage Properties of TiO2 Hierarchical Spheres

AbstractTitanium dioxide (TiO2) is a promising electrode material for reversible lithium storage. However, the poor electronic conductivity, sluggish diffusivity, and intrinsic kinetics limit hinder its fast lithium storage capability. Here we present that the oxygen‐deficient TiO2 hierarchical spheres can address the issues for high capacity, long‐term lithium‐ion battery anode. First‐principles calculations show that introducing oxygen vacancies to anatase TiO2 can reduce the bandgap, thus improving the electronic conductivity and further the lithium storage properties of TiO2. By annealing TiO2/H2Ti5O11⋅3H2O hierarchical spheres precursor in nitrogen, accompanying with the phase transfer process, the growth of TiO2 crystallites is restricted due to the generation of residual carbon species, resulting in a well maintained hierarchical spherical structure. Rich oxygen vacancies are generated in the oxygen‐deficient environment and evidenced by EPR, XPS, and UV‐Vis spectra, which enable the TiO2 hierarchical spheres reduced bandgap. The oxygen vacancies in the as‐obtained TiO2 hierarchical spheres together with the high structural integrity of the hierarchical spheres gives rise to superior lithium storage properties including a high specific capacity of 282 mAh g−1 at 200 mA g−1, and long‐term cycling stability with a capacity retention of 85.2 % at 4 A g−1 over 10000 cycles.

Enhanced strength and electrical conductivity of Al–0.3Ce alloy simultaneously with Ti(C,N) nanoparticle addition

Ti(C,N) nanoparticles were added to an Al–0.3Ce alloy by ultrasonic treatment. Further annealing at 570 °C for 4 h afforded the ultimate tensile strength of 79 MPa and electrical conductivity of 64.0% IACS for the Al–0.3Ce alloy with 1.5 vol% Ti(C,N) addition. Both performance parameters were improved by 23.4% and 0.6% IACS, respectively, compared with those of casting refining pure aluminum (64 MPa and 63.4% IACS). This could be explained by the following reasons. The addition of Ti(C,N) nanoparticles could significantly refine the grain of Al–0.3Ce alloy. Notably, most of the coarse strip-shaped second phases distributed at the grain boundaries in Al–0.3Ce were also transformed into spherical microparticles distributed in the grains, with micro–nano hierarchical structures comprising orientated nanosized strip phases with lengths of ~ 400 nm and widths of ~ 100 nm. Moreover, a fine micro–nano hierarchical spherical structure could be obtained after annealing at 570 °C for 4 h. The numbers of micro–nano hierarchical spherical structures also increased due to the precipitation of pseudosolution Ce from the aluminum matrix during the annealing treatment.

A polymer-assisted strategy for hierarchical SnS@N-doped carbon microspheres with enhanced lithium storage performance

Two-dimensional metal dichalcogenides show a promising potential in energy storage due to their high specific capacity. Different from the bulk SnS prepared by conventional solvothermal method, our strategy to prepare the three-dimensional (3D) hierarchical SnS@N-doped carbon (SnS@NC) microspheres assembled from ultrathin nanosheets is realized by the polymer-assisted solvothermal method. The key factor of SnS@NC microspheres is the use of polyvinylpyrrolidone, which not only acts as surfactant to obtain the hierarchical spherical structure but also is used as heteroatom sources to realize the N-doped carbon layer coating. Compared with the bulk SnS, the enhanced electrochemical performance of SnS@NC electrode can be attributed to its 3D hierarchical structure and composition advantages, including enhanced Li+ diffusion kinetics, faster charge transfer, enough void space to accommodate the volume variation, higher electronic conductivity, and more active sites.

Facile synthesis of alkaline-earth metal manganites for the efficient degradation of phenolic compounds via catalytic ozonation and evaluation of the reaction mechanism

In this paper, we demonstrate the facile and general synthesis of alkaline-earth metal manganites, denoted as A(Mg, Ca, Ba)MnxOy, for efficient degradation of high-concentration phenolic compounds via catalytic ozonation. The representative CaMnxOy oxides show a hierarchical spherical structure constructed by crystalline nanorods and numerous macropores. They possess mixed Mn4+/Mn3+ chemical valences and abundant surface hydroxyl (OH) groups. The ozone (O3) decomposition rate on the CaMnxOy catalysts is greatly accelerated and follows the first-order law. These catalysts are promising for the degradation of phenolic compounds via catalytic ozonation, exhibiting rapid pseudofirst-order degradation kinetics, a high total organic carbon (TOC) removal efficiency and an excellent stability. Under optimized conditions (a low O3 dosage of 1.5 mg/min and a catalyst dosage of 7.5 g/L), for the treatment of concentrated phenol (50–240 mg/L), the CaMnxOy catalysts show 100% degradation and 50–70% mineralization within 1.0 h. The Ca2+ ions are essential to create redox Mn4+/Mn3+ couples and to significantly reduce manganese leaching. High surface ratios of Mn4+/Mn3+ and OH/lattice oxygen (Olat) are beneficial for enhancing the catalytic performance. Superoxide anion free radicals (O2–) and singlet oxygen (1O2) are the predominant reactive species for the oxidation degradation. The O2– reaction pathway is proposed. Specifically, the surface OH sites activate O3, displaying highly enhanced decomposition rates. The generated O2– and 1O2 play a role in oxidation. The redox Mn4+/Mn3+ and the Olat/oxygen vacancy (Olat/Ovac) couples play important roles in electron transfer. The proposed mechanism is supported by active site probing, radical scavenging, spectroscopic studies, and the results in the degradation of substituted phenols.

C3N4-digested 3D construction of hierarchical metallic phase MoS2 nanostructures

Metallic MoS2 with a controllable hierarchical spherical structure has been achieved via a hydrothermal strategy by using the carbon nitride nanospheres as a self-sacrificed template.

Microwave-assisted synthesis of honeycomblike hierarchical spherical Zn-doped Ni-MOF as a high-performance battery-type supercapacitor electrode material

A Zn-doped Ni-based metal−organic framework (Ni-MOF) material with honeycomblike hierarchical spherical structure is synthesized by a microwave-assisted method using HCl as the modulator for the first time. By adjusting the amount of the Zn ions doped, an optimal Zn doped Ni-MOF electrode material is obtained, which possesses a superior electrochemical performance: specific capacity of 237.4 mA h g-1 and 122.3 mA h g-1 at 1 A/g and 20 A/g, respectively. This is one of the highest performances reported so far for MOFs. The excellent electrochemical properties are ascribed to the unique crystal structure and special morphology of the Zn-doped Ni-MOF material. This work shows that the microwave-assisted synthesis is a rapid and efficient method for preparation of Ni-MOF supercapacitor electrode material.

Microwave synthesis of a novel magnetic imprinted TiO2 photocatalyst with excellent transparency for selective photodegradation of enrofloxacin hydrochloride residues solution

Abstract Magnetic imprinted TiO 2 photocatalyst (MITP) with excellent transparency was prepared via a microwave heating method based on enrofloxacin hydrochloride (ENRH) as the template molecule, methyl methacrylate (MMA) as the functional monomer, and TiO 2 @SiO 2 @Fe 3 O 4 (TSF) as the matrix material. TSF was synthesized by a mild sol–gel method. The results indicated that MITP possessed hierarchical spherical structure, good monodispersity, superior magnetic properties (Ms = 11.59 emu/g), the average diameter was approximately 410 nm, and the surface-imprinted layer was composed of the imprinted polymer and poly (methyl methacrylate). Moreover, MITP was proved to exhibit an excellent photochemical stability and a higher photocatalytic efficiency than other photocatalysts, the apparent rate constant ( k ) for degradation of ENRH with MITP in 90 min under the visible light irradiation was 1.08 min −1 . The coefficient of selectivity ( k selectivity ) of MITP relative to TSF and magnetic non-imprinted TiO 2 photocatalyst (MNITP) was 2.14 and 2.08, respectively, indicating that MITP also possessed the strong ability to selective recognition and photodegradation of ENRH in the binary antibiotic residues solution containing ENRH and tetracycline (TC). In addition, the mechanism and intermediate products of selective photodegradation of the binary antibiotic residues solution with MITP were further discussed.

Characterization of calcium carbonate crystals in pigeon yolk sacs with different incubation times

Calcium carbonate crystals are known to form in the yolk sacs of fertile pigeon eggs at late stages of incubation. The composition and structure of these crystals were investigated, the crystallization environment was inspected, and the physical chemistry constants of the yolk fluid were determined through the incubation period. Polarized light microscopy was used to observe the generation and distribution of calcium carbonate crystals in the yolk sac. In addition, X-ray diffraction was employed to analyze the composition and crystal phase of the yolk sac. A decalcification and deproteination method was established to analyze the ultrastructure and composition of the crystals, as well as the internal relationship between inorganic and organic phases of the crystals. Additionally, scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, and Fourier transform infrared spectroscopy were used to evaluate the characteristics of the crystals. Our results demonstrated that the calcium carbonate crystals were mainly composed of vaterite and calcite, with vaterite being the major component. Vaterite, a type of biomaterial generated by an organic template control, presented as a concentric hierarchical spherical structure. The organic nature of the biomaterial prevented vaterite from transforming into calcite, which is more thermodynamically stable than vaterite. Additionally, the configuration, size, and aggregation of vaterite were also mediated by the organic template. This bio-vaterite was found during the incubation period and is valuable in calcium transport during embryonic development.