Zhen-Xing Li

Photon-manipulated drug release from a mesoporous nanocontainer controlled by azobenzene-modified nucleic acid.

Herein a photon-manipulated mesoporous release system was constructed based on azobenzene-modified nucleic acids. In this system, the azobenzene-incorporated DNA double strands were immobilized at the pore mouth of mesoporous silica nanoparticles. The photoisomerization of azobenzene induced dehybridization/hybridization switch of complementary DNA, causing uncapping/capping of pore gates of mesoporous silica. This nanoplatform permits holding of guest molecules within the nanopores under visible light but releases them when light wavelength turns to the UV range. These DNA/mesoporous silica hybrid nanostructures were exploited as carriers for the cancer cell chemotherapy drug doxorubicin (DOX) due to its stimuli-responsive property as well as good biocompatibility via MTT assay. It is found that the drug release behavior is light-wavelength-sensitive. Switching of the light from visible to the UV range uncapped the pores, causing the release of DOX from the mesoporous silica nanospheres and an obvious cytotoxic effect on cancer cells. We envision that this photocontrolled drug release system could find potential applications in cancer therapy.

Homogeneously Dispersed Ceria Nanocatalyst Stabilized with Ordered Mesoporous Alumina

As one of the most important functional rare earth oxides, ceria (CeO2) has been widely applied in catalysis, fuel cells, optical materials, gas sensors, and so forth. In particular, nanostructured ceria plays an active role in catalysis applications because of its reduced dimensions, increased relative surface area, highly active facets, large number of active sites, and changeable valence state. In the past decade, the controlled synthesis of ceria nanocrystals has become one of the essential topics in rare earth materials science, since high selectivity and activity can be achieved by size and morphology design. One of the well-known cases is the role of CeO2 in CO oxidation. In this case, traditional bulk ceria materials had been reported to be inadequate for CO oxidation as a catalyst support. However, as shown by Corma et al. the activity for CO oxidation increased by two orders of magnitude when the particle size of ceria decreased to the nanosize region. Hydrothermal, solvothermal, and thermolysis approaches, all of which are based on solution-phase methods, are widely utilized for nanostructured ceria synthesis. Recent examples showed that sub-10-nm ceria can be synthesized using capping agents. Using oleic acid as the stabilizing agent, Gao and coworkers obtained monodisperse ceria nanocubes with an average size of approximatley 4 nm. However, an obstruction for further application lies in that CeO2 nanoparticles with a size smaller than 5nm tend to aggregate during thermal treatments, forming secondary large particles, and thus, the active sites decrease rapidly owing to reduced surfaces. Therefore, up to now, the synthesis of thermally stable ceria nanoparticles with a uniform small size still remains as a challenge. In the case of catalysis reaction, catalyst deactivations caused by sintering of catalysts at high temperature are very common, which may hinder their further industrial applications. Confinement effect can be a solution to address this tough problem. Materials with different nanostructures, especially those that have pores or hollows, are ideal candidates to provide confined microenvironments. With ordered channels of 2–50nm, mesoporous structured materials are very suitable for this purpose. Current methodologies for the assembly of metal or metal oxide nanoparticles in mesoporous materials include, for example, conventional incipient wetness impregnation, post-grafting, and metal–organic chemical vapor deposition. Somorjai et al. incorporated Pt nanocrystals into SBA-15 silica during hydrothermal synthesis. The Pt particles were observed to be located within surfactant micelles during silica formation, which led to their dispersion throughout the silica structure. Bao and co-workers reported an in situ autoreduction route for the fabrication of monodisperse silver nanoparticles on silica-based materials. Features of the narrow channels in hexagonal mesostructures (for example MCM-41, SBA-15) being utilized, one-dimensional nanomaterials such as nanorods or nanowires can be anticipated. Gold nanowires have been reported in the channels of mesoporous SBA-15 by hydrogen flow reduction, electroless reduction, and seed-mediated growth processes. CeO2 nanoparticles were also embedded into mesoporous SiO2 during the mesostructure formation and then stabilized by this ordered mesostructure. Although many efforts have been devoted to explore the confinement effect of mesoporous materials, almost all of these works are focused on silica-based mesoporous materials except for a few works on carbon-based cases. Despite its obvious virtues, the lack of acid/base sites as well as the chemical inactive inertness of the silica surface limits its use for the purpose of catalysis application. As a promising candidate for a three-way catalyst, CeO2–Al2O3 composites have attracted world-wide attention. The sol–gel process was employed to synthesize the ceria-doped alumina materials reported by Viveros et al. In our previous study, the ordered mesoporous aluminas have proved to possess wide applications in catalysis with the benefits of their large surface areas, high thermal stability, large surface Lewis acid sites, and tunable pore size. They are proposed to be good candidates for the fabrication and stabilization of nanometer-scaled ceria, since the channels can prevent the possible growth and reuniting of nanocrystals. Based on all the advantages mentioned above, herein, using the sol–gel method combined with an evaporation-induced self-assembly process, we explore a new strategy to synthesize uniform ceria nanocatalysts stabilized by ordered mesoporous alumina. Using the sample with 8 mol% Ce (denoted as meso-8CeAl) as an example, evidence for the formation of mesostructures is provided by small-angle X-ray diffraction (XRD) patterns shown in Figure 1a. The sample calcined at 400 8C shows a very strong diffraction peak around 1.08 and one weak peak around 1.78, which, associated with transmission electron microscopy (TEM) observation, can be attributed to p6mm hexagonal symmetry. The mesoscopic ordering is sustained well even after calcination at

Ionic Liquid-Based Route to Spherical NaYF4 Nanoclusters with the Assistance of Microwave Radiation and Their Multicolor Upconversion Luminescence

An ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate)-based route was introduced into the synthesis of novel spherical NaYF(4) nanoclusters with the assistance of a microwave-accelerated reaction system. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDS) and upconversion (UC) luminescence spectroscopy were used to characterize the obtained products. Interestingly, these spherical NaYF(4) nanoclusters with diameters ranging from 200 to 430 nm are formed by the self-assembly of small nanoparticles. The diameters of the nanoclusters could be easily tuned just by changing the amounts of the precursors. By conducting the control experiments with different ILs or precursors, it is proven that the ILs have played key roles, such as the solvents for the reaction, the absorbents of microwave irradiation, and the major fluorine sources for the formation of the NaYF(4) nanocrystals. The UC luminescence properties of the Ln(3+) codoped NaYF(4) were measured, and the results indicate that the nanoclusters obtained in BmimBF(4) exhibit excellent UC properties. Since this IL-based and microwave-accelerated procedure is efficient and environmentally benign, we believe that this method may have some potential applications in the synthesis of other nanomaterials.

Colour modification action of an upconversion photonic crystal

Colour modification of the upconversion emission has been successfully achieved in a novel upconversion photonic crystal.

Hierarchical γ-Al2O3 monoliths with highly ordered 2D hexagonal mesopores in macroporous walls

Hierarchical gamma-Al2O3 monoliths with interconnected macroporous architecture and highly ordered 2D hexagonal mesostructure have been synthesized by using nonionic triblock copolymer and polyurethane foam as co-templates.

Facile Synthesis of Macrocellular Mesoporous Foamlike Ce–Sn Mixed Oxides with a Nanocrystalline Framework by Using Triblock Copolymer as the Single Template

Macrocellular mesoporous foamlike cerium-tin mixed oxide materials with well-defined porous structure and nanocrystalline frameworks are synthesized through a simple one-step self-assembly process using an amphiphilic triblock copolymer as the single template. The macrocellular pores are synthesized without the addition of any swelling agent or hazardous acids. The final mixed oxide possesses a hierarchically porous structure including macrocellular foam with ultralarge cell size, closed windows, and mesopores on the walls. This indicates that the porous structure can be notably stabilized and improved by the incorporation of Sn in the CeO(2). The materials are expected to be good candidates in catalysis, since the hierarchical porosity enables high surface areas and hence more chemically active sites associated with the mesopores, combined with the high efficiency of mass transport from the macrocellular foam. The catalytic characteristics are discussed in relation to the architectures of the materials, and it is revealed that the macrocellular/mesoporous materials would be an efficient catalyst for CO oxidation.

Controllable Assembly of Hierarchical Macroporous–Mesoporous LnFeO3 and Their Catalytic Performance in the CO + NO Reaction

A new synthesis strategy to prepare hierarchical macroporous-mesoporous materials employing poly(ethylene oxide)-poly(phenylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) as a single template and an acid adjusting agent was reported. There is a hierarchical structure including macropores with a size of 50-100 nm and mesopores in the macroporous walls with a size of 3-5 nm. The macroporous walls are composed of rare earth orthoferrite nanoparticles with a size of 5-10 nm. These hierarchically porous materials show high catalytic activities for the CO + NO reaction, and NO can be fully converted to N2 at temperatures as low as 350 °C, indicating their potential in the catalytic conversion of automotive exhaust gas and other catalysis-related fields. This synthesis strategy is a facile method for the preparation of hierarchical porous materials and may give us a guideline for the synthesis of functional materials with further catalytic applications.