Xiaoming Ma

Adsorption of heavy metal ions using hierarchical CaCO3-maltose meso/macroporous hybrid materials: Adsorption isotherms and kinetic studies

Highly ordered hierarchical calcium carbonate is an important phase and has technological interest in the development of functional materials. The work describes hierarchical CaCO(3)-maltose meso/macroporous hybrid materials were synthesized using a simple gas-diffusion method. The uniform hexagonal-shaped CaCO(3)-maltose hybrid materials are formed by the hierarchical assembly of nanoparticles. The pore structure analysis indicates that the sample possesses the macroporous structure of mesoporous framework. The distinguishing features of the hierarchical CaCO(3)-maltose materials in water treatment involve not only high removal capacities, but also decontamination of trace metal ions. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The maximum removal capacity of the CaCO(3)-maltose hybrid materials for Pb(2+), Cd(2+), Cu(2+), Co(2+), Mn(2+) and Ni(2+) ions was 3242.48, 487.80, 628.93, 393.70, 558.66 and 769.23 mg/g, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The adsorption and precipitation transformation mechanism can be considered due to hierarchical meso/macroporous structure, rich organic ligands of the CaCO(3)-maltose hybrid materials and the larger solubility product of CaCO(3).

Facile synthesis of mesoporous CdS nanospheres and their application in photocatalytic degradation and adsorption of organic dyes

CdS nanospheres with an average diameter of 40 nm, mesopores of 11.2 nm and a large specific surface area of 89.66 m2 g−1 are fabricated successfully via a facile method under mild conditions. The as-prepared CdS nanospheres exhibit good performance in the photocatalytic degradation and adsorption activity for organic dyes.

Efficient biosorption of lead(II) and cadmium(II) ions from aqueous solutions by functionalized cell with intracellular CaCO3 mineral scaffolds

The functionalized Saccharomyces cerevisiae cell with biogenic intracellular CaCO3 mineral scaffold, synthesized via a simple and environmentally friendly approach, was efficient for removing lead (II) and cadmium (II) ions from aqueous solutions. The CaCO3 mineral scaffold could promote the uptake of the heavy metal ions and increase the biosorption capabilities of the adsorbent. Compared with the Freundlich isotherm, Langmuir model more fitted the equilibrium data. The maximum removal capacity of functionalized cells for Pb(II) and Cd(II) was 116.69 and 42.63mgg(-1), respectively. Further investigation showed that the adsorbent had high removal efficiency for trace amount of heavy metal ions. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicated that pseudo-second-order kinetic equation and intra-particle diffusion model could better describe the adsorption kinetics. The heavy metal ions might be removed by functionalized cells via membrane transport of metal ions and precipitation transformation.

Facile one-pot synthesis and photocatalytic properties of hierarchically structural BiVO4 with different morphologies

Hierarchically structured m-BiVO4 crystals with twin-ball-like, cauliflower-like, pinwheel-like, columnar and spherical morphologies were synthesized by a facile one-pot method in the presence of soluble starch. The physicochemical properties of the material were characterized by means of XRD, SEM, HRTEM/SAED, UV-vis absorption and N2 adsorption techniques. The oriented aggregation mechanism may rationally explain the formation of the hierarchical structure. The assistance of the starch and the pH value of the precursor solution play pivotal roles in the formation of the hierarchical structures with different morphologies because the existing forms of bismuth and starch vary with the pH value of the precursor solution. The photocatalytic activities of the as-prepared BiVO4 samples were evaluated for the photodegradation of Rhodamine B (RhB) in aqueous solution under simulated sunlight irradiation. The highest photocatalytic activity of BiVO4 obtained at pH = 4 may result from several factors, such as the moderate BET surface area, the highest crystallinity, the lowest bandgap and the most exposed (040) face.

Shape-controlled synthesis of protein-conjugated silver sulfide nanocrystals and study on the inhibition of tumor cell viability

Stable protein-conjugated silver sulfide nanoparticles, nanorods and nanowires have been prepared by an aqueous chemistry method and the study results showed they had potential applications for tumor treatment.

Palladium nanoparticles with high energy facets as a key factor in dissociating O2 in the solvent-free selective oxidation of alcohols

Palladium (Pd) nanocatalysts with high energy facets {110} supported on flower-like hydroxyapatite (F-HAP) were successfully prepared. Based on the experimental data and theoretical calculations, it was found that the O2 dissociation on Pd {110} facets could be key to the performance of Pd nanoparticles in the solvent-free selective oxidation of alcohols.

Observation of Rotated-Oriented Attachment during the Growth of Ag2S Nanorods under Mediation of Protein

In this study, protein-conjugated Ag2S nanorods were prepared in aqueous solution, and high-resolution transmission electron microscopy (HRTEM) was used to track the whole process of the nanorod growth. Our results showed that the final products were formed via two-step oriented attachment, that is, particle-particle and rod-rod oriented. More interestingly, before oriented attachment, the nanoparticles or nanorods attached without sharing the same lattice plane; they could then rotate to a perfect array and fuse together by eliminating the two high energy surfaces. On the basis of the calculation of surface energy, two-step attachments and rotations were brought forward, and the role of protein in the forming process of nanorods was discussed.

An unusual temperature gradient crystallization process: facile synthesis of hierarchical ZnO porous hollow spheres with controllable shell numbers

In this study, three types of hierarchical ZnO porous hollow spheres consisting of ZnO nanoparticles with controllable shell numbers were synthesized through different temperature gradient processes using a simplified hard template method. Compared with the traditional hard template method, we facilitated the experiment by the fabrication of zinc precursor-carbon microsphere composites during the formation of carbon microspheres. The shell numbers of the spheres could be controlled by varying the temperature gradient rate during the calcination procedure. Importantly, a different formation mechanism is proposed in this experiment. That is, the synthesis of hierarchical multi-shelled porous hollow spheres might be based on not only the inside-out Ostwald ripening process but also on an unusual temperature gradient crystallization mechanism. Further investigation also revealed that the samples exhibited a varied photocatalysis performance with the efficiency decreasing from the hierarchical triple-shelled porous hollow spheres to the single-shelled spheres progressively. What is more, these hierarchical hollow materials have a good recycle performance, which will be a great potential material in real applications. Our present work not only provides a method, but also, more importantly, provides a theoretical guide to fabricate the multi-shelled porous hollow materials with hierarchical structures, which can be used in many industrial applications.

Facile preparation of hydroxyapatite with a three dimensional architecture and potential application in water treatment

Hydroxyapatite with a flower-like three dimensional architecture was successfully prepared through a facile transformation process of hedgehog-like aragonite precursors. Based on the time-dependent experiments, a possible mechanism was proposed. In addition, the hydroxyapatite assemblies exhibit unique selective adsorption activity for heavy metals.

Fabrication and potential applications of CaCO3–lentinan hybrid materials with hierarchical composite pore structure obtained by self-assembly of nanoparticles

Chemically designed, hierarchical composite pore materials, with two or more different sized pores arranged regularly and high specific surface area, have attracted considerable attention because of possessing improved functions and applications in chemistry, pharmaceutics, environmental protection and so on. In this study, two biogenic materials, calcium carbonate (CaCO3), the most widely studied biomineral, and lentinan, showing prominent antitumor activity, are incorporated into the biomineralization process to produce CaCO3–lentinan microspheres with hierarchical composite pore structure by the hierarchical assembly of nanoparticles. The pore structure analysis indicated that a wormhole mesoporous structure was present in the framework of the CaCO3–lentinan microspheres and a microporous structure was present in the core part of the mesoporous walls, rendering an unusual hierarchical composite pore structure of CaCO3. The results revealed that the hierarchical composite pore structure could obviously reduce the release rate and prolong the release time of the anticancer drug, which led to minimization of poisonous side effects and decreased bodily injuries due to the stepwise release of the drug from mesoporous pores to micropores. The component CaCO3 with pH-sensitivity could controllably release DOX at the acidic tumour site, which minimizes the spread of toxic drugs around the normal tissues while maximizing tumor-directed drug delivery. In particular, the CaCO3–lentinan microspheres have ideal biocompatibility and biodegradability which are of critical importance for the clinical application. Further investigation also revealed the desirable properties of the CaCO3–lentinan microspheres for the removal of Congo red (CR) pollutant from waste water, with the maximum removal capacity of 213.2 mg g−1, which will be a great potential material in real applications.