The direct production of macromolecular scale (sub-5 nm) porous nanocrystals with high surface area has been a considerable challenge over the past two decades. Here we report an interfacial site-directed capping agent-free growth method to directly produce porous ultrasmall (sub-5 nm), fully crystalline, macromolecular scale nanocrystals. The porous sub-5 nm Prussian blue nanocrystals exhibit uniform sizes (∼4 ± 1 nm), high surface area (∼855 m² g^-1), fast electron transfer (rate constant of ∼9.73 s^-1), and outstanding sustained catalytic activity (more than 450 days). The nanocrystal-based biointerfaces enable unprecedented sub-nanomolar level recognition of hydrogen peroxide (∼0.5 nM limit of detection). This method also paves the way towards the creation of ultrasmall porous nanocrystals for efficient biocatalysis.

孔彪    Sun Xiaotian    Cordelia Selomulya    Jing Tang    郑耿峰    Wang Yingqing    赵东元    

Chemical Science

2015

The development of non-precious metal catalysts for efficient oxygen reduction is of significance for many advanced electrochemical devices such as fuel cells and metal-air batteries. Herein, we develop a graphene-directed assembly route to synthesize hierarchically nanoporous Co-Nx/C materials with a macro/meso/microporous structure, high specific surface area (i.e. 512 m² g^-1) and excellent conductivity using graphene oxide (GO) supported zeolitic imidazolate framework nanocrystal arrays as a catalyst precursor, followed by the carbonization and acid leaching process. In this route, GO acts as a structure-directing agent to construct ZIF nanocrystal arrays supported on GO nanosheets. During the carbonization process, the resulting reduced graphene oxide functions as a binder and electrical conductor to connect individual ZIF-derived carbon nanoparticles into the macroporous structure and increase the overall conductivity. ZIF nanocrystals themselves are also converted into meso/microporous carbon nanoparticles without using any other template. The hierarchically porous Co-Nx/C materials exhibit high ORR catalytic activity, superior stability and good methanol tolerance under both alkaline and acidic conditions.

Jing Wei    Yaoxin Hu    Wu Zhangxiong    Yan Liang    Sookwan Leong    孔彪    Xinyi Zhang    赵东元     Simon G.    Huanting Wang   

Journal of Materials Chemistry A

2015

Immobilization of highly monodispersed palladium nanoparticles in colloidal mesoporous silica supports has been successfully achieved. The Pd nanoparticles with a uniform small size of ∼1.2 nm can be homogeneously distributed in individual mesopore channels of amino group-functionalized three-dimensional dendritic mesoporous silica nanospheres (3D-dendritic MSNSs) with a Pd content of ∼2.8%. The 3D-dendritic MSNSs-based nanoreactors show high activity in Suzuki-Miyaura cross-coupling reactions of bromobenzene with phenylboronic acid, obtaining a yield over 99% with 0.075 mol % Pd catalyst at room temperature in the dark within 12 h. More importantly, the excellent catalytic performance can be maintained with a negligible decrease lasting at least six cycles. It further reveals that the mesoporous frameworks of the colloidal silica supports can be well-preserved after four catalytic runs; meanwhile, the Pd nanoparticles in the mesopore channels also can remain the sizes of 1.5 ± 0.3 nm without significant transfer and aggregation. The unique mesostructure of the 3D-dendritic MSNSs with mesopore channels of short length and large diameter is supposed to be the key role in immobilization of active and robust heterogeneous catalysts, and it would have more hopeful prospects in catalytic applications.

Dengke Shen    Chen Lei    杨建平    张任远    Yong Wei    Xiaomin Li    李炜    Zhenkun Sun    Zhu Hongwei    Abdullah    Abdullah Al-Enizi    Ahmed Elzatahry    张凡    赵东元    

ACS Applied Materials and Interfaces

2015

Augmenting fluorescence intensity is of vital importance to the development of chemical and biochemical sensing, imaging and miniature light sources. Here we report an unprecedented fluorescence enhancement with a novel architecture of multilayer three-dimensional colloidal photonic crystals self-Assembled from polystyrene spheres. The new technique uses a double heterostructure, which comprises a top and a bottom layer with a periodicity overlapping the excitation wavelength (E) of the emitters, and a middle layer with a periodicity matching the fluorescence wavelength (F) and a thickness that supports constructive interference for the excitation wavelength. This E-F-E double heterostructure displays direction-dependent light trapping for both excitation and fluorescence, coupling the modes of photonic crystal with multiple-beam interference. The E-F-E double heterostructure renders an additional 5-fold enhancement to the extraordinary FL amplification of Rhodamine B in monolithic E CPhCs, and 4.3-fold acceleration of emission dynamics. Such a self-Assembled double heterostructue CPhCs may find significant applications in illumination, laser, chemical/biochemical sensing, and solar energy harvesting. We further demonstrate the multi-functionality of the E-F-E double heterostructure CPhCs in Hg (II) sensing.

Eftekhari Ehsan    Li Xiang    Kim Tak H.    Gan Zongsong    Cole Ivan S.    赵东元     Kielpinski    顾敏    Qin Li   

Scientific Reports

2015

Core-shell magnetic mesoporous silica microspheres (Magn-MSMs) with tunable large mesopores in the shell are highly desired in biocatalysis, magnetic bioseparation, and enrichment. In this study, a shearing assisted interface coassembly in n-hexane/water biliquid systems is developed to synthesize uniform Magn-MSMs with magnetic core and mesoporous silica shell for an efficient size-selective biocatalysis. The synthesis features the rational control over the electrostatic interaction among cationic surfactant molecules, silicate oligomers, and FeO@RF microspheres (RF: resorcinol formaldehyde) in the presence of shearing-regulated solubilization of n-hexane in surfactant micelles. Through this multicomponent interface coassembly, surfactant-silica mesostructured composite has been uniformly deposited on the FeO@RF microspheres, and core-shell Magn-MSMs are obtained after removing the surfactant and n-hexane. The obtained Magn-MSMs possess excellent water dispersibility, uniform diameter (600 nm), large and tunable perpendicular mesopores (5.0-9.0 nm), high surface area (498-623 m/g), large pore volume (0.91-0.98 cm/g), and high magnetization (34.5-37.1 emu/g). By utilization of their large and open mesopores, Magn-MSMs with a pore size of about 9.0 nm have been demonstrated to be able to immobilize a large bioenzyme (trypsin with size of 4.0 nm) with a high loading capacity of ∼97 μg/mg via chemically binding. Magn-MSMs with immobilized trypsin exhibit an excellent convenient and size selective enzymolysis of low molecular proteins in the mixture of proteins of different sizes and a good recycling performance by using the magnetic separability of the microspheres.

Yue Qin    Li Jialuo    Luo Wei    Zhang Yu    Ahmed Elzatahry    Xiqing Wang    Chun Wang    Wei Li    程晓维    Alghamdi Abdulaziz    Abdullah    邓勇辉    赵东元    

Journal of the American Chemical Society

2015

Rational design and controllable synthesis of TiO based materials with unique microstructure, high reactivity, and excellent electrochemical performance for lithium ion batteries are crucially desired. In this paper, we developed a versatile route to synthesize hollow TiO/graphitic carbon (H-TiO/GC) spheres with superior electrochemical performance. The as-prepared mesoporous H-TiO/GC hollow spheres present a high specific surface area (298 m g), a high pore volume (0.31 cm g), a large pore size (∼5 nm), well-defined hollow structure (monodispersed size of 600 nm and inner diameter of ∼400 nm, shell thickness of 100 nm), and small nanocrystals of anatase TiO (∼8 nm) conformably encapsulated in ultrathin graphitic carbon layers. As a result, the H-TiO/GC hollow spheres achieve excellent electrochemical reactivity and stability as an anode material for lithium ion batteries. A high specific capacity of 137 mAh g can be achieved up to 1000 cycles at a current density of 1 A g (5 C). We believe that the mesoporous H-TiO/GC hollow spheres are expected to be applied as a high-performance electrode material for next generation lithium ion batteries.

Hao Liu    李炜    Dengke Shen    赵东元     汪国秀   

Journal of the American Chemical Society

2015

Prussian blue (PB), the oldest synthetic coordination compound, is a classic and fascinating transition metal coordination material. Prussian blue is based on a three-dimensional (3-D) cubic polymeric porous network consisting of alternating ferric and ferrous ions, which provides facile assembly as well as precise interaction with active sites at functional interfaces. A fundamental understanding of the assembly mechanism of PB hetero-interfaces is essential to enable the full potential applications of PB crystals, including chemical sensing, catalysis, gas storage, drug delivery and electronic displays. Developing controlled assembly methods towards functionally integrated hetero-interfaces with adjustable sizes and morphology of PB crystals is necessary. A key point in the functional interface and device integration of PB nanocrystals is the fabrication of hetero-interfaces in a well-defined and oriented fashion on given substrates. This review will bring together these key aspects of the hetero-interfaces of PB nanocrystals, ranging from structure and properties, interfacial assembly strategies, to integrated hetero-structures for diverse sensing.

孔彪    Cordelia Selomulya    郑耿峰    赵东元    

Chemical Society Reviews

2015

Mesoporous silica synthesized from the cocondensation of tetraethoxysilane and silylated carbon dots containing an amide group has been adopted as the carrier for the in situ growth of TiO through an impregnation-hydrothermal crystallization process. Benefitting from initial complexation between the titania precursor and carbon dot, highly dispersed anatase TiO nanoparticles can be formed inside the mesoporous channel. The hybrid material possesses an ordered hexagonal mesostructure with p6mm symmetry, a high specific surface area (446.27 m g), large pore volume (0.57 cm g), uniform pore size (5.11 nm), and a wide absorption band between λ=300 and 550 nm. TiO nanocrystals are anchored to the carbon dot through Ti-O-N and Ti-O-C bonds, as revealed by X-ray photoelectron spectroscopy. Moreover, the nitrogen doping of TiO is also verified by the formation of the Ti-N bond. This composite shows excellent adsorption capabilities for 2,4-dichlorophenol and acid orange 7, with an electron-deficient aromatic ring, through electron donor-acceptor interactions between the carbon dot and organic compounds instead of the hydrophobic effect, as analyzed by the contact angle analysis. The composite can be photocatalytically recycled through visible-light irradiation after adsorption. The narrowed band gap, as a result of nitrogen doping, and the photosensitization effect of carbon dots are revealed to be coresponsible for the visible-light activity of TiO. The adsorption capacity does not suffer any clear losses after being recycled three times.

Cheng Chen    Tan Xianjun    卢德力    王灵芝    Sen Tapas    雷菊英    El-Toni Ahmed Mohamed    张金龙    张凡    赵东元    

Chemistry - A European Journal

2015

Abstract Transition metal oxides are regarded as promising anode materials for lithium-ion batteries because of their high theoretical capacities compared with commercial graphite. Unfortunately, the implementation of such novel anodes is hampered by their large volume changes during the Li insertion and extraction process and their low electric conductivities. Herein, we report a specifically designed anode architecture to overcome such problems, that is, mesoporous peapod-like CoO@carbon nanotube arrays, which are constructed through a controllable nanocasting process. CoO nanoparticles are confined exclusively in the intratubular pores of the nanotube arrays. The pores between the nanotubes are open, and thus render the CoO nanoparticles accessible for effective electrolyte diffusion. Moreover, the carbon nanotubes act as a conductive network. As a result, the peapod-like CoO@carbon nanotube electrode shows a high specific capacity, excellent rate capacity, and very good cycling performance.

顾栋    李炜    Fei Wang    Bongard Hans    Spliethoff Bernd    Schmidt Wolfgang    Weidenthaler Claudia    夏永姚    赵东元     Ferdi Schüth   

Angewandte Chemie - International Edition

2015

Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiOmicrospheres with a diameter of ∼800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiOspheres have a large accessible surface area (112 m/g), a large pore volume (0.164 cm/g), and highly single-crystal-like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiOmicrospheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.

刘勇    车仁超    陈刚    Jianwei Fan    Zhenkun Sun    吴张雄    Minghong Wang    Bin Li    Jing Wei    Yong Wei    Wang    Guozhen Guan    Elzatahry Ahmed A.    Bagabas Abdulaziz    Abdullah Al-Enizi    Deng Yonghui    彭慧胜    赵东元    

Science Advances

2015