Rongmei Liu

Dendrite-like Co3O4 nanostructure and its applications in sensors, supercapacitors and catalysis

Dendrite-like Co(3)O(4) nanostructure, made up of many nanorods with diameters of 15-20 nm and lengths of 2-3 μm, has been successfully prepared by calcining the corresponding nanostructured Co-8-hydroxyquinoline coordination precursor in air. The Co(3)O(4) nanostructure was evaluated as an electrochemical sensor for H(2)O(2) detection and the results reveal that it has good linear dependence and high sensitivity to H(2)O(2) concentration changes. As an electrode material of a supercapacitor, it was found that the nanostructured Co(3)O(4) electrode exhibits high specific capacitance and long cycle life. The Co(3)O(4) nanostructure also has good catalytic properties and is steadily active for CO oxidation, giving 100% CO conversion at low temperatures. The multifunctional Co(3)O(4) nanostructure would be a promising functional nanomaterial applied in multi industrialized fields.

Synthesis of copper(II) coordination polymers and conversion into CuO nanostructures with good photocatalytic, antibacterial and lithium ion battery performances

Two different nanostructured copper–isonicotinic acid (INA) coordination polymers, Cu(C6H4NO2)2(H2O)4 and [Cu(C6H4NO2)(OH)]H2O have been successfully synthesized under hydrothermal conditions on a large scale without the assistance of surfactants or template. Cu(C6H4NO2)2(H2O)4 has the morphology of 2-dimensional (2D) butterfly-like nanosheet structures, while [Cu(C6H4NO2)(OH)]H2O consists of one-dimensional (1D) nanorods. A possible formation mechanism of the obtained coordination polymer nanostructures is proposed with provision of the crystal structure. After heat treatment, hierarchical CuO butterfly-sheet-like nanostructures and CuO nanotubes were obtained. The photocatalytic and antibacterial studies indicate that the as-obtained CuO samples have great photocatalytic activities for the degradation of Rhodamine B and good bacteriostatic activities. In addition, the electrochemical measurements show that CuO samples exhibit high reversible discharge capacities and stable cyclic performances.

Metal Ions Induce Growth and Magnetism Alternation of α‐Fe2O3 Crystals Bound by High‐Index Facets

In this study, quasi-cubic and hexagonal bipyramid α-Fe(2)O(3) polyhedrons with high-index facets exposed were controllably synthesized by applying metal ions Zn(2+) or Cu(2+) as structure-directing agents. The growth of the α-Fe(2)O(3) nanostructures with high-index facets were induced by metal ions without the addition of any other surfactants. The quasi-cubic form controlled by Zn(2+) looks like a cube but has an angle of approximately 86° bound by (012), (10-2), and (1-12) facets, whereas the hexagonal bipyramid form controlled by Cu(2+) has a sixfold axis bound by {012} facets. Magnetic measurements confirm that these two kinds of nanocrystals display shape- and surface-dependent magnetic behaviors. The hexagonal bipyramid iron oxide nanocrystals show a lower Morin transition temperature of 240 K and might be spin-canted ferromagnetically controlled at room temperature, and the ferromagnetism disappears at low temperature. The quasi-cubic nanocrystals have a splitting between FC curve and ZFC curve from the highest experimental temperature and no Morin transformation occurs; this indicates that they would be defect ferromagnetically controlled at low temperature. The reported metal-ion-directing technique could provide a universal method for shape- and surface-controlled synthesis of nanocrystals with high-index facets exposed.

Al3+-controlled synthesis and magnetic property of α-Fe2O3 nanoplates

Hexagonal α-Fe2O3 nanoplates were prepared through a hydrothermal method with the addition of Al3+ ions. The added Al3+ ions not only act as a structure-directing agent for controlled growth of α-Fe2O3 nanoplates, but may also be the reason for magnetism alteration of α-Fe2O3.

Fabrication of Zn2SnO4/SnO2 hollow spheres and their application in dye-sensitized solar cells

Uniform Zn2SnO4/SnO2 hollow spheres were successfully synthesized and hybridized by calcining ZnSn(OH)6 solid spheres in air, and showed a very good efficiency of 4.52% as an electrode material for DSSCs. The in situ hybridization of Zn2SnO4 and SnO2 in Zn2SnO4/SnO2 hollow spheres is beneficial for electron transport and light scattering, and leads to the high efficiency of the Zn2SnO4/SnO2 composite in DSSCs.

Biomolecule‐Assisted Construction of Cadmium Sulfide Hollow Spheres with Structure‐Dependent Photocatalytic Activity

In this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure-dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution-reprecipitation mechanism. Their visible-light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible-light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure.

Nickel ions inducing growth of high-index faceted α-Fe2O3 and their facet-controlled magnetic properties

In this study, single-crystalline α-Fe2O3 polyhedrons with high-indexed facets exposed were controllably synthesized through a simple hydrothermal route with Ni2+ ions as the structure-directing agent. The polyhedral crystals are quasi-cubic with an angle of approximately 86° and bound by (012), (10–2) and (1–12) facets. With insufficient Ni2+ ions added, only concave α-Fe2O3 crystals can be got while only irregular α-Fe2O3 crystals were obtained without the addition of Ni2+ ions. The growth process of α-Fe2O3 quasi-cubes was investigated and possible growth mechanism was proposed. Magnetic measurements confirm that the α-Fe2O3 nanocrystals with different morphologies display shape and surface-dependent magnetic behaviors. As the morphology of α-Fe2O3 crystals change from irregular particles to concave cube and then quasi-cubes with the increase of added Ni2+ amounts, the magnetism of the obtained α-Fe2O3 alters from spin-canted ferromagnetism, coexistent spin-canted and defect magnetism and then defect magnetism at room temperature.

Green synthesis of fluorescent carbon quantum dots and carbon spheres from pericarp

An economical idea was developed to synthesize fluorescent carbon quantum dots (CQDs) directly from the refluxing extraction of orange pericarp via a hydrothermal technique. Hydrothermal temperatures and times were adjusted to control the particle sizes and the quantum yields of the obtained CQDs. The as-prepared carbon quantum dots showed narrow particle size distribution, good water solubility, and acceptable fluorescence lifetimes. Due to their high stability, these obtained carbon quantum dots have great application potential in nano-biotechnology. Furthermore, carbon spheres with uniform morphology and size can be easily obtained as the reaction byproducts of this green synthesis process.