Yuhua Shen

Tunable surface plasmon resonance of Au@Ag2S core–shell nanostructures containing voids

A novel rodlike core–shell nanostructure containing voids between shell and core has been effectively synthesized by the Kirkendall effect. The Au@Ag2S nanoparticles exhibit preferable optical properties due to integrating the absorption behaviors of the Au cores and the Ag2S shells and existence of voids. When Ag is coated on the surface of Au nanorods, the SPR absorption of the Au nanorods shows a blue shift. While Ag is transformed to Ag2S, the SPR absorption of the Au nanorods shifts to high wavenumber. Different shells could adjust and control the SPR absorption of Au nanorods. Moreover, the voids endow the nanostructured materials with other new functions such as catalysis, drug delivery and so on.

Layer-by-layer assembly of chitosan/tungstosilicate acid-Ag nanocomplex with electrocatalytic properties

Tungstosilicate acid (TSA)-Ag nanocomplex were synthesized based on the reduction of silver nitrate by UV-irradiated tungstosilicate acid solution. The nanocomposite films consisting of TSA-Ag composite nanoparticles and chitosan (CTS) were fabricated by layer-by-layer self-assembly technique. The coverage degree of TSA-Ag composite nanoparticles on the surface of the film increased with the number of the bilayers. TSA-Ag composite nanoparticles grew in a direction normal to the surface of the film. Large overlap existed between adjacent layers of TSA-Ag and CTS. The composite thin film exhibited linear, uniform and regular layer-by-layer growth. The multiplayer films exhibited good electrocatalytic activity for dioxygen reduction.

Complex calcium carbonate aggregates: controlled crystallization and assemblyvia an additive-modified positive-microemulsion-route

The controlled fabrication of various kinds of complex calcium carbonate aggregates through the cooperative interactions between positive-microemulsion and soluble-additives has been systematically investigated. The polymorphs and morphologies of the products were well controlled by the existence of positive-microemulsion and the co-effect of glycine or magnesium ions. Hollow spherical aggregates of CaCO3 consisting of monodispersed spherical nanoparticles (∼50 nm) were obtained by fine control over the thermodynamic/kinetic balance in glycin/microemulsion. Furthermore, the controlled assembly process was captured. The cooperative interactions between microemulsion and Mg2+ ions were first used to mimic the mineralization of CaCO3, obtaining novel hierarchical aragonite crystals, such as novel spindle-shaped aragonite, wafer sheet-shaped aragonite and so on. The formation of these specific CaCO3 aggregates with different crystalline phases could be ascribed to the assembly of calcium carbonate precursor (spherical or sheet-like nano-particles) with the aid of a dual template. The results imply that the specific biomimetic synthesis strategy in a dual template solution can provide a useful pathway to produce inorganic or inorganic/organic hybrid materials with a unique morphology and specific textures.

Preparation of Al2O3-supported nano-Cu2O catalysts for the oxidative treatment of industrial wastewater

Cuprous oxide (Cu2O) nanoparticles supported on Al2O3 prepared using two different methods (hereafter referred to as catalyst I and II, respectively) were characterized by XRD and TEM. The catalytic activities of catalyst I and II during the treatment of industrial wastewater were then investigated. Specifically, the progress of the catalytic oxidation of industrial wastewater was observed by monitoring the time-dependent change in the chemical oxygen demand (COD) of industrial wastewater when the catalysts were applied. The results indicated that the catalytic activity of catalyst II was greater than that of catalyst I. Furthermore, under optimal conditions the COD removal efficiency was 94.59%. Finally, the mechanism by which the oxidative degradation of the industrial wastewater occurred could be explained based on a hydroxyl radical mechanism.

Biomimetic Synthesis of Calcium Bilirubinate in Different Inverse Microemulsions

Three inverse microemulsions, such as Triton X‐100/n‐hexyl alcohol/cyclohexane/water, containing tyrosine (Tyr) or tryptophan (Trp) were selected as the template to induce nucleation and growth of calcium bilirubinate (CaBR) crystal. CaBRs were characterized by Fourier transform infrared spectra (FTIR), Ultraviolet‐visible spectra (UV‐vis), transmission electron microscopy (TEM), powder X‐ray diffraction (XRD), and Zeta potential, respectively. The experimental results showed that the different CaBR nanocrystals were successfully synthesized in inverse microemulsions. Surfactants and amino acids (AAs) played important roles in the formation of CaBR nanocrystals. AAs affected microstructure, morphology, agglomeration and crystallizability of CaBR. The possible growth mechanism of CaBR nanocrystals was studied in different microemulsions.

Sorption mechanisms of cadmium onto nano-hydroxyapatite: Comparative uptake studies and correlative solubility analysis

Hydroxyapatite (HAP) nanorod was synthesized by using ordered bicontinuous microemulsion, and was characterized by X-ray diffraction spectrum, scanning electron microscopy and high-resolution transmission electron microscopy. The solubility was investigated using ion chromatogram measurement, and was sensitively dependent on the value of pH. The capabilities to capture cadmium ions of HAP nanorods and micro-particles from aqueous salt solution were studied, and besides, X-ray diffractometry was used in order to characterize the mechanisms of cadmium uptake. As Cd2+ adsorption occurred, it has undergone the coprecipitation of Cd2P2O7 crystal to give multiple solids composed of HAP and Cd2P2O7 crystallites, which affected the dissolution of hydroxyapatite. During Cd2+ sorption process, solubility variations of the sediments showed a more complex pattern than previously reported. Contribution of surface mechanisms, in association with precipitation of cadmium phosphate phases, could explain this behavior.

Biogenic synthesis of calcium oxalate crystal by reaction of calcium ions with spinach lixivium

In this paper, we report a biogenic synthesis protocol for preparation of calcium oxalate (CaC2O4, CaOx) crystal at room temperature by a simple protein-mediated reaction of aqueous Ca2+ ions with the C2O4(2-) ions spontaneously released from spinach. The aggregation of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) with a rod-like morphology was mainly formed in the spinach root lixivium, and the proportion of COM crystal in the aggregation increased with the concentration of Ca2+ ions increasing, however, spindle-shaped crystal was mainly obtained in the spinach leaf lixivium and the content of COM in the product was higher than that obtained in the root lixivium with the similar concentration of Ca2+ ions. COM phase disappeared and only COD crystal with morphology of tetragonal bipyramidal prisms presented in the product when the leaf lixivium was replaced by the leaf broth. The biomolecules such as proteins with molecular weight of 31kDa liberated from the spinach root are negative-charged, which played important roles for the control of CaOx crystal growth in the root lixivium corresponding to the changes of protein secondary structures after reaction with Ca2+ ions. This research was potentially important for unraveling the biomineralization mechanism of CaOx crystal.

Biomimetic synthesis of the arachidic acid/Ag x Cd y S nanocomposite films

AgxCdyS nanoparticles were obtained in arachidic acid (AA) monolayer containing Ag+ and Cd2+ under H2S flow. The AA/AgxCdyS monolayers were deposited onto solid substrate to prepare LB films. The UV-vis spectrum showed that the LB film exhibited notable quantum-size effect. The small-angle X-ray diffraction revealed periodic structure of the LB films. The molar ratio of Ag to Cd in AA/AgxCdyS film was ca. 1 : 5 as measured by the XPS. TEM and FTIR spectroscopy showed that the head-groups of arachidic acid molecules controlled formation of AgxCdyS nanoparticles in the monolayer.

Synthesis and characterization of PbS nanorods in W/O microemulsion system

PbS nanorods have been successfully synthesized in water-in-oil (W/O) microemulsion containing non-ionic surfactant OP, n-pentanol, cyclohexane, and aqueous solution. The effects of the molar ratio of water to surfactant (ω0), the concentration of reactants and the ageing time on the morphologies of PbS nanoparticles were investigated. The microstructures, morphologies and properties of the synthesized products were characterized by means of X-ray diffraction, transmission electron microscopy, and ultraviolet-visible (UV-VIS) absorption spectroscopy, respectively. The results showed that the synthesized rod-like products are composed of cubic phase PbS. These nanorods have an average diameter of about 100 nm, and an average length of about 500 nm. In the UV-VIS absorption spectrum, the absorption edge of PbS nanorods exhibit a blue shift compared with that of bulk PbS, indicating the quantum confinement effect of PbS nano-particles