Yongsheng Han

Effect of temperature on the preparation and electrocatalytic properties of a spinel NiCo2O4/Ni electrode

Abstract NiCo 2 O 4 spinel oxide was prepared through the hydroxide coprecipitation method. The NiCo 2 O 4 powders were analyzed by TGA, XRD, BET, SEM, and EDS. And the electrocatalytic properties of NiCo 2 O 4 /Ni electrode for oxygen evolution in alkaline solution were evaluated by cyclic voltammetry, roughness factor, Tafel curves and stability testing. The result shows that the preparation temperature can affect the formation, specific surface area, morphologies, and electrocatalytic properties of NiCo 2 O 4 spinel oxide. It is also found that NiCo 2 O 4 /Ni electrode prepared at 300°C has better electrocatalytic properties in oxygen evolution reaction than those prepared at other temperatures.

Biocompatible Protein Nanocontainers for Controlled Drugs Release

We designed a biocompatible carrier for controlled release of hydrophobic drugs. The designed carrier was prepared by sonicating oil in a protein aqueous solution forming a protein nanocontainer composed of an inner gel core and an outer protein shell. Two model drugs were loaded into the designed nanocontainers by dissolving drugs in the oil phase before sonication. The loading capacity was up to 0.9 mg/mL for the amphiphilic drug rifampicin, while it reached to 19 mg/mL for the hydrophobic drug indomethacin. The encapsulated drugs were released at different temperatures. At 37 degrees C, only less than 20% of the drug was released due to the protection by the gel core. Increasing temperature to 40 degrees C led to a completely release of the remaining drug. The drug release showed drastic temperature dependence. The biocompatibility of the protein nanocontainers was evaluated by incubating the nanocontainers in the 3T3 cell and B-LCL cell lines. Both experiments indicated an excellent biocompatibility of the designed nanocontainers.

X-ray study of cation distribution in NiMn1-xFe2-xO4 ferrites

Abstract The spinel ferrite system NiMnxFe2−xO4, with x=0, 0.2, 0.4, 0.6, 0.8 and 1, was prepared by the standard double sintering ceramic method. The cation distribution has been calculated analytically for the first time using X-ray diffraction combined with computer technology. The results show, with increasing manganese ion substitution, that both Ni2+ and Mn3+ ions predominately occupy the octahedral sites. This is consistent with their preference for large octahedral site energy. The concentration of Mn3+ ions in octahedral sites increases while that of Fe3+ ions decreases linearly.

Stability and size dependence of protein microspheres prepared by ultrasonication

Protein microspheres have been prepared by sonicating oil in an aqueous protein solution. Such prepared microspheres can be used in magnetic resonance imaging (MRI), micro-encapsulation, and drug delivery systems. When they are used in the blood circulation, their size and stability become most important. In this paper, the factors affecting the size and size distribution of these microspheres are discussed and a way to control the size of the microspheres is put forward. Small microspheres with size less than 1 µm were selected by gravitational sedimentation. The selected microspheres have a narrow size distribution and can be used in the blood circulation safely. The loading of dye into these microspheres was easily achieved by dissolution of drugs in the oil phase before sonication. The protein microspheres showed excellent protection for the loaded dye, which can be stably carried for several weeks.

A Facile Sonochemical Route for the Fabrication of Magnetic Protein Microcapsules for Targeted Delivery

Protein microcapsules have received considerable attention as effective drug delivery carriers for the treatment of deadly diseases, such as cancer, in the biomedical field. Up to now, extensive efforts have been devoted to fabricate the protein microcapsules and several approaches have been developed. Suslick and co-workers used high-intensity ultrasound to make aqueous suspensions of proteinaceous microcapsules filled with water-insoluble liquids and demonstrated the chemical mechanism of their formation. Lu et al. fabricated protein capsules through protein adsorption at the surface of the organic droplets followed by evaporation of the organic solvent. Balabushevich et al. produced stable polyelectrolyte capsules by the layer-by-layer (LbL) assembling of biodegradable polyelectrolytes, dextran sulfate, and protamine on melamine formaldehyde (MF) microcores followed by core decomposition at low pH. Among the various routes, the sonochemical method has proved to be a simple and effective technique for fabricating protein microcapsules due to the convenient processing and experimental setup, significant saving in time, and excellent products. In addition, the hydrophobic drugs could be directly loaded into protein microcapsules by dissolving drugs in the oil phase before sonication. Magnetic nanoparticles (MNPs), especially iron oxide (Fe3O4) MNPs, also have shown great prospect in biomedical application due to their good biocompatibility, strong superparamagnetism, nontoxicity, and easy preparation proACHTUNGTRENNUNGcess.[20–28] Introducing Fe3O4 MNPs into the biocompatible protein microcapsules are of particular interest, because protein microcapsules functionalized with Fe3O4 MNPs would possess several attractive advantages from a pharmaceutical standpoint:

Cation distribution in NixMn1−xFe2O4 ferrites

Abstract The cation distribution in the spinel ferrite system Ni x Mn 1− x Fe 2 O 4 (with x =0, 0.25, 0.5, 0.75 and 1) has been calculated analytically for the first time in the closed form as a function of thermodynamic parameters by making reasonable assumption. The manganese and nickel site occupancies show a nearly linear composition dependence. Trivalent iron occupancies reflect the transition from octahedral to tetrahedral sites. The calculated results are consistent with those from X-ray diffraction (XRD).

A switch from classic crystallization to non-classic crystallization by controlling the diffusion of chemicals

Here we report a study on controlling the shape of particles by regulating the diffusion of chemicals. To change the diffusion rate of the reactive ions, we used a designed three-cell reactor in which the reactive ions were separated by porous membranes. We studied the reduction of hexachloroplatinate ions by sodium borohydride as an example. The experimental results show that control of the chemical diffusion led to the platinum product changing from cubic particles to dendritic particles. Further analysis indicates that the cubic particles were formed by the classic crystallization process via layer-wise deposition, while the dendritic particles were formed by the non-classic crystallization process through cluster aggregation. The control over the chemical diffusion prolongs the nucleation period and produces nuclei continuously, facilitating the aggregation of nuclei, which leads to the crystallization switching from the classic model to the non-classic model. The obtained results in this paper suggest that control over the chemical diffusion is a green and promising process to manipulate the structures of materials.

The Effect of Sintering Temperature on Porous Silica Composite Strength

The effect of sintering temperature on porous silica composite strength was studied by discussing three factors, namely crystal phase, glassy phase and porosity. The fired products of clay and silica are composed of crystalline phase and glassy phase. The crystalline phases consist of alpha-quartz and mullite and the glassy phase contains a disordered silica network. With the increase of sintering temperature up to 1360°C, the crystalline silica decreased gradually. The disappearing silica dissolved into the glass and became a part of glass network and resulted in the enhancement of glass strength. This change in glass played an important role in the improvement of sample strength. At the same time, the increase of sintering temperature promoted the densification of samples and reduced the porosity of products, which also contribute to the increase of sample strength. When the sintering temperature is up to 1390°C, the silica in glass tended to convert to cristobalite with the expansion of glassy phase. This expansion weakened the connection of atoms in glass network and brought some closed pores into products, which led to the decrease of sample strength.

Preparation of protein microcapsules with narrow size distribution by sonochemical method

Protein microcapsules with narrow size distribution have been prepared by sonochemical method which is a simple, fast, environmental friendly and cost-effective method. The prepared microcapsules are composed of a water-insoluble core and an outer protein shell. The hydrophobic drugs could be encapsulated into protein microcapsules directly via sonochemical method by dissolving drugs in the nontoxic and edible vegetable oil before ultrasonication, which is a potential solution for drug resistance by hiding cytotoxic drugs in the carrier and allows for the delivery of high doses in relatively small volume. The size and size distribution of protein microcapsules are very important for their practical application. In this paper, the factors affecting the size and size distribution of protein microcapsules are investigated in detail. Moreover, confocal laser scanning microscopy and transmission electron microscopy confirmed that the protein microcapsules with narrow size distribution were obtained.

Reversibly Switching Silver Hierarchical Structures via Reaction Kinetics

Here we report a study on controllable synthesis of hierarchical silver structures via regulating reaction kinetics. Silver particles with various morphologies are synthesized by a solution-based reduction approach at the addition of amino acids. The amino acid is used to coordinate with silver ions to slow down the reduction of silver ions. With the increase of glycine concentration, the morphologies of silver particles switch from dendrites, to flowers and to compacted spheres, which is attributed to the decrease of reaction rate as a result of the coordination. Three more amino acids are examined and confirms the role of reaction kinetic in shaping silver particles. Furthermore, by increasing the concentration of the reductant, the silver morphologies change from compact spheres to loose flowers as a result of the increase of reaction rate. Therefore the silver hierarchical structure can be reversibly switched by reaction kinetics. The silver particles synthesized are tested for surface enhanced Raman scattering (SERS) property and the dendritic particles present a remarkable SERS activity. This study shows that reaction kinetics is a powerful tool to tune hierarchical structures of silver particles, which is expected to be transferable to other material systems.