Yong-Mei Hao

Effective removal of Cu (II) ions from aqueous solution by amino-functionalized magnetic nanoparticles.

A novel magnetic nano-adsorbent (MNP-NH(2)) has been developed by the covalent binding of 1,6-hexadiamine on the surface of Fe(3)O(4) nanoparticles for removal of Cu(2+) ions from aqueous solution. Various factors affecting the uptake behavior such as contact time, temperature, pH, salinity, amount of MNP-NH(2) and initial concentration of Cu(2+) were investigated. The kinetics was evaluated utilizing the Lagergren pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models. The equilibrium data were analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich isotherms. The adsorption was relatively fast and the equilibrium was established within 5 min, and its kinetics followed the pseudo-second-order mechanism, evidencing chemical sorption as the rate-limiting step of sorption mechanism. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities was 25.77 mg g(-1) at pH 6, and 298 K. Thermodynamic parameters showed that the adsorption process was spontaneous, endothermic and chemical in nature. The successive adsorption-desorption studies indicated that the MNP-NH(2) sorbent kept its adsorption and desorption efficiencies constant over 15 cycles. Importantly, MNP-NH(2) was able to remove 98% of Cu(2+) from polluted river and tap water.

Studies on a high encapsulation of colchicine by a niosome system

To prepare niosomes which have high encapsulation capacity for soluble drugs, starting from Span 60 and cholesterol, an improved method, evaporation-sonication method, was proposed. The corresponding niosomes show a good stability at least 40 days. Colchicine was chosen as a model drug for examining the capsulation capacity of these niosomes. To obtain the highest encapsulation efficiency, several factors including the structure of surfactant, level of lipid, content of drug and cholesterol were investigated and optimized. The inner cause was also discussed. The results indicate that the Span 60 is the most ideal surfactant among four kinds of Span. Furthermore, the release studies of colchicine and 5-fluorouracil (5-FU) in vitro from niosomes exhibited a prolonged release profile as studied over a period of 24 h. The results demonstrated that niosomes prepared in this way not only have high encapsulation capacity but also is expected that side effects of drugs may be reduced. It still suggests that this method may be used extensively in the field of encapsulation soluble drugs.

Entrapment and release difference resulting from hydrogen bonding interactions in niosome.

In this study the influence of hydrogen bonding interaction between niosomal membrane and solutes on the drug loading and release was investigated. Salicylic acid (SA) and p-hydroxyl benzoic acid (p-BA) were selected as models. Niosomes were prepared with 1:1 molar ratios of various surfactants and cholesterol by film hydration technique, and the corresponding formulation variables were optimized to achieve the maximum entrapment efficiencies (EE%). The EE% of different formulations followed the trend Span 60>Span 40>Span 20>Span 80. Additionally, it was also found that the EE% of p-BA was much higher than that of SA. This difference may be due to the formation of hydrogen bond between p-BA and niosomal membrane, and the corresponding interaction diagram has been proposed and confirmed indirectly by UV spectroscopy method. The quantitative analysis of hydrogen binding interaction between solutes and niosome has been finished firstly, and the corresponding entrapment equilibrium constant K has been calculated as well. Moreover, in vitro the release of both drugs from niosomes was examined in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), respectively. The results indicated that the release of p-BA in SIF was much slower than that in SGF, and the release rate of SA in SGF is apparently slower than that in SIF. The possible mechanism was given as well.

Local valence and physical properties of double perovskite Nd2NiMnO6

A polycrystalline double perovskite Nd2NiMnO6 (NNM) has been synthesized through the solid-state reaction method. Powder x-ray diffraction data can be indexed by the space group P21/n. Double magnetization transition temperatures at 105.12 K and 193.04 K are observed from temperature-dependent magnetization curve and can be ascribed to Ni3+–O–Mn3+ and Ni2+–O–Mn4+ superexchange interactions, respectively. The effective magnetic moment, Curie constant C and paramagnetic Curie–Weiss temperature θ are calculated to be 6.023μB/f.u., 4.529(4) emu K mol−1 Oe−1 and 191.1(9) K, respectively. Mixed valence of Mn ion is further evidenced by x-ray photoelectron spectra and the mole ratio of Mn3+/Mn4+ is determined to be 19.53 : 81.47. The dielectric relaxor behaviour is found in NNM and follows the Vogel–Fulcher relationship with Ea = 0.0264 eV, Tf = 283.2 K and f0 = 4.66 × 108 Hz. The delocalized carriers in the semiconducting sample may explain the origin of dielectric relaxation.

Cooperative effects of a combined substitution on the magnetic properties of Nd2−xYxFe17−ySiy intermetallic compounds (0⩽x⩽1.5,0⩽y⩽3.0)

The effects of a combined substitution of Nd by Y and Fe by Si in Nd2−xYxFe17−ySiy compounds (0⩽x⩽1.5,0⩽y⩽3.0) on structural and magnetic properties have been investigated by means of x-ray diffraction, neutron diffraction, and magnetic measurements. The investigated samples crystallize in Th2Zn17-type structure with only small amounts of alpha-Fe. The unit cell volume decreases with increasing Y content or Si content. Neutron diffraction analysis indicates that substitution of Y for Nd induces a decrease of Si occupancy in 18h sites and increases in 9d sites and 18f sites. With the substitution of Y for Nd, the average site bond lengths in 6c, 9d, 18f, and 18h sites all decrease, but the distances of all Fe-Fe pairs do not change negatively. The TC of Nd2−xYxFe17−ySiy increases significantly with increasing Si substitution (y⩽3.0), but it changes slightly with increasing Y substitution. Similar to the case of Si substitution, the Ms also first increases and then decreases with increasing Y substitution. ...

Structure of Gd(5-x)HoxSi4 Solid Solutions

A new systematic study of the formation and structure of solid solutions Gd (5-x)HoxSi4 (x = 1.0-5.0) has been performed. By X-ray powder diffraction method, it was found that these compounds all crystallize in orthorhombic structure with space group Pnma and the cell parameters a, b, c and the volume of unit cell are correlated with the holmium content.

Fabrication of Spark Plasma Sintering on Pb(Mg1/3Nb2/3)O3–PbTiO3 Ceramics Layers Prepared by Tape Casting and TGG Method

The spark plasma sintering technique was used to fabricate ceramics from Pb(Mg1/3Nb2/3)O3– PbTiO3 ceramic layers which were prepared by tape casting and TGG method used BaTiO3 templates as seeds. During heat treatment, epitaxial grain growth occurred on the BaTiO3 surfaces and formed <001> textured lead magnesium niobate-lead titanate, Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (PMN-32.5PT) ceramics. The phase compositions and microstructure were investigated. The results indicated that this method was an alternative sintering technology to synthesize dense lead-based relaxor ferroelectric ceramics.