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04/2011; , ISBN: 978-953-307-217-3
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ChemPhysChem 02/2011; 12(2):278-81. · 3.41 Impact Factor
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ABSTRACT: Carbon nanomaterials have advanced rapidly over the last two decades and are among the most promising materials that have already changed and will keep on changing human life. Development of synthetic methodologies for these materials, therefore, has been one of the most important subjects of carbon nanoscience and nanotechnology, and forms the basis for investigating the physicochemical properties and applications of carbon nanomaterials. In this Research News article, several synthetic strategies, including solvothermal reduction, solvothermal pyrolysis, hydrothermal carbonization, and soft-chemical exfoliation are specifically discussed and highlighted, which have been developed for the synthesis of novel carbon nanomaterials over the last decade.
Advanced Materials 05/2010; 22(17):1963-6. · 13.88 Impact Factor
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ABSTRACT: High yield production of graphene oxide and graphene sheets with an ultralarge size (up to approximately 200 microm) was realized using a modified solution-phase method.
Chemical Communications 04/2010; 46(15):2611-3. · 6.17 Impact Factor
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ABSTRACT: Helical conformation exists universally at different length scales. We present a new model to explain the energetics of a helical structure with ordered mesopores and successfully predict their equilibrium state. The formation of the helical structure, which is composed of twisted and hexagonally arrayed one-dimensional pore channels, should be understood at the macromorphology level through the competition between surface free energy reduction and torsion strain energy increase. Our model is established by first reverting a helical rod with experimentally defined parameters to a conjectured straight rod without intrinsic pore channel twisting, and then quantitatively calculating the variation of two competitive energies as a function of twist angle in the torsion process starting from the reverted straight rod. Through our model, a free energy curve is achieved, so that the equilibrium state and the helical structural parameters can be predicted, which are in good agreement with experimental results for helical rods synthesized by different surfactant templates. Moreover, our model can be successfully applied to explain the pitch-radius relationships in previous observations. Our achievement provides unique and fundamental understandings for the spontaneous mesoscopic helix formation, which are different from the microscopic helical structures such as DNA chains.
The Journal of Physical Chemistry B 12/2009; 113(50):16178-83. · 3.70 Impact Factor
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ABSTRACT: The synthesis of ultrasmall, well-dispersed, hollow siliceous spheres (HSSs) by using a block copolymer as the template and tetraethoxysilane as a silica source under acidic conditions is reported. After removing the surfactant core of as-synthesized, spherical, silica-coated block-copolymer micelles, HSSs with a uniform particle size of 24.7 nm, a cavity diameter of 11.7 nm, and a wall thickness of 6.5 nm are obtained. It is shown that by surface functionalization of HSSs with methyl groups during synthesis, HSSs can be further dispersed in solvents such as water or ethanol to form a stable sol. Moreover, the hollow cavities are accessible for further loading of functional components. In addition, it is demonstrated that HSSs possess superior endocytosis properties for HeLa cells compared to those of conventional mesoporous silica nanoparticles. A feasible and designable strategy for synthesizing novel well-dispersed hollow structures with ultrasmall diameters instead of conventional ordered mesostructures is provided. It is expected that HSSs may find broad applications in bionanotechnology, such as drug carriers, cell imaging, and targeted therapy.
Small 11/2009; 6(2):276-82. · 8.35 Impact Factor
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Pei Yuan, Xufeng Zhou,
Hongning Wang,
Nian Liu,
Yifan Hu,
Graeme J Auchterlonie,
John Drennan,
Xiangdong Yao,
Gao Qing Max Lu,
Jin Zou,
Chengzhong Yu
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ABSTRACT: The packing structures of macroporous ordered siliceous foams (MOSFs) are systematically investigated by using a 3D electron tomography technique and the nanostructural characteristics for layered MOSFs are resolved. MOSF materials adopt an ordered 2D hexagonal arrangement in single-layered areas, regular honeycomb patterns in double-layered samples, and polyhedric cells similar to a Weaire-Phelan structure in multilayered areas, all following the principle of minimizing surface area, which is well understood in soap foams at the macroscopic scale. In surfactant-templated materials, liquid-crystal templating is generally applied, but here it is revealed that the surface-area-minimization principle can also be applied, which facilitates the design and synthesis of novel macroporous materials using surfactant molecules as templates.
Small 02/2009; 5(3):377-82. · 8.35 Impact Factor
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ABSTRACT: Organosiliceous multilamellar vesicles (MLVs) have been prepared with a high yield (>90%) and at mild conditions, through a single-templating approach by using Pluronic P85 as a structure directing agent and 1,2-bis(triethoxysilyl)ethane (BTEE) as an organosilica source. The obtained vesicles have diameters of 100−200 nm and possess sponge-like walls with the mesopore size centered at 6 nm. The number of layers can be adjusted from 7 to 1 by changing the synthesis pH value from 4.8 to 5.2. The specific surface area and pore volume of organosilica MLVs are as large as 695 m2/g and 2.10 cm3/g, respectively. Moreover, a transformation from the hexagonal mesostructure obtained at pH 4.2 to multilamellar (pH 4.8−5.2) and unilamellar vesicles (pH 5.5) is observed. The organosilica MLVs with controlled wall thickness, hierarchical porosity, and interconnected sponge-like walls are promising candidates for applications in nanoreactors, selective sorption, and controlled release.
08/2008;
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ABSTRACT: We studied the synthesis of siliceous structures by using a nonionic block copolymer (Pluronic P123) and perfluorooctanoic acid (PFOA) as cotemplates in an acid-catalyzed sol-gel process. Different siliceous structures were obtained through systematically varying the molar ratio (R) of PFOA/P123, and the resultant materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen sorption analysis, and Fourier-transform infrared spectroscopy. The results are consistent and reveal a structure transition from a highly ordered 2D hexagonal (HEX) mesostructure with a rodlike morphology to multilamellar vesicles (MLVs) with sharp edges when R is increased. The fact that the MLVs are initiated from the end of hexagonally mesostructured rods provides key evidence in such a novel structure transition. Our finding indicates that, at least in our observations, the MLVs are developed gradually from HEX structures, rather than by a direct cooperative self-assembly mechanism. It is suggested that PFOA molecules with rigid fluorocarbon chains closely interact with PEO. This interaction model may well explain (1) the "wall-thicken" effect in HEX mesostructures by enlarging the hydrophilic PEO moiety (R = 0-1.4), (2) the subsequent HEX to multilamellar structure transition by modifying the hydrophilic/hydrophobic volume ratio (R = 1.4-2.8), and (3) the formation of MLVs with sharp edges by increasing the bending energy. This model provides insight into the fabrication of novel porous materials by the use of block copolymers and fluorinated surfactant mixed templates.
Langmuir 06/2008; 24(9):5038-43. · 4.19 Impact Factor
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Pei Yuan,
Nian Liu,
Lingzhi Zhao, Xufeng Zhou,
Liang Zhou,
Graeme J Auchterlonie,
Xiangdong Yao,
John Drennan,
Gao Qing Max Lu,
Jin Zou,
Chengzhong Yu
Angewandte Chemie International Edition 01/2008; 47(35):6670-3. · 13.45 Impact Factor
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ABSTRACT: We report the synthesis of raspberry-like hierarchical siliceous hollow spheres (HSHS) via a one-pot, one template approach. The siliceous species and block copolymer molecules self-assemble simultaneously into composite spherical micelles and vesicles in solution. The colloidal interaction between spheres with different sizes gives rise to the final HSHS structure with a raspberry morphology.
Journal of the American Chemical Society 12/2007; 129(47):14576-7. · 9.91 Impact Factor
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ABSTRACT: We report the synthesis and characterization of a novel mesoporous material with a face-centered cubic (fcc) symmetry and intrinsic bimodal pores. Moreover, an icosahedral (ICO) mesostructure with both meso- and macroscale 5-fold symmetry is observed. We propose a hard-sphere packing (HSP) mechanism for the formation of mesoporous materials by assuming preformed robust surfactant/silicate composite micelles being hard spheres. In comparison to the conventional liquid crystal templating (LCT) or cooperative self-assembly (CSA) mechanism, our contribution provides an important advancement of knowledge in the study of mesostructured materials.
Journal of the American Chemical Society 08/2007; 129(29):9044-8. · 9.91 Impact Factor
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Angewandte Chemie International Edition 02/2007; 46(45):8579-82. · 13.45 Impact Factor
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ABSTRACT: We report a new approach to produce macroporous ( approximately 110 nm in diameter) ordered siliceous foams (MOSF) by using block copolymers as templates in the absence of any organic cosolvent. The fine three-dimensional honeycomb structure of MOSF was determined by electron tomography. A formation mechanism of MOSF that spans from the atomic to macroscopic scale is proposed, which involves the cooperative self-assembly of unilamellar vesicles followed by the supra-assembly of vesicles. The fusion of soft vesicles finally leads to MOSF with well-ordered and defined honeycomb structures.
Journal of the American Chemical Society 01/2007; 128(50):15992-3. · 9.91 Impact Factor
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ABSTRACT: We report the synthesis of novel polysilsesquioxane hybrid crystals prepared from two precursors with hexylene- and octylene-bridged groups. Both crystals are composed of bimolecular rings (18- and 22-membered, respectively) formed by one-step condensation of two hydrolyzed monomers. The hydrogen bonds between silanol groups and the weak van der Waal's interactions between alkyl chains link the large rings as building blocks together into self-assembled, three-dimensional molecular crystalline structures. The precise control of the sol-gel process is considered to be the crucial factor in fabricating flexible long alkyl chains into an ordered stacking. These contributions extend the understanding of the sol-gel chemistry of polysilsesquioxanes.
Chemistry 12/2006; 12(33):8484-90. · 5.93 Impact Factor
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ABSTRACT: The investigation on the formation mechanism of helical structures and the synthesis of helical materials is attractive for scientists in different fields. Here we report the synthesis of helical mesoporous materials with chiral channels in the presence of achiral surfactants. More importantly, we suggest a simple and purely interfacial interaction mechanism to explain the spontaneous formation of helical mesostructures. Unlike the proposed model for the formation of helical molecular chains or surpramolecular packing based on the geometrically motivated model or the entropically driven model, the origin of the helical mesostructured materials may be attributed to a morphological transformation accompanied by a reduction in surface free energy. After the helical morphology is formed, the increase in bending energy together with the derivation from a perfect hexagonal mesostructure may limit the curvature of helices. Our model may be general and important in the designed synthesis of helical mesoporous materials.
Journal of the American Chemical Society 09/2006; 128(32):10460-6. · 9.91 Impact Factor
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ABSTRACT: Based on a previous study of protein digestion inside the nanoreactor channels of the mesoporous molecular sieve silicate SBA-15 (Chem. Eur. J. 2005, 11: 5391), we have developed a highly efficient enrichment and subsequent tryptic digestion of proteins in SBA-15 for matrix-assisted laser desorption/ionization mass spectrometry with time-of-flight/time-of-flight analyzer (MALDI-TOF/TOF) peptide mapping. The performance of the method is exemplified with myoglobin and cytochrome c. First, protein adsorption isotherms for two standard proteins with a range of initial concentration of proteins were investigated at room temperature. The results revealed that the kinetic adsorption rate of a protein within SBA-15 was independent of initial protein concentration, and a 15-min protein enrichment within SBA-15 could be enough for protein identification in biological samples. It was noticed that no washing steps were needed to avoid protein loss due to desorption from the mesochannels into solution. Second, protein digestion inside the channels of SBA-15 was also optimized. After adsorption of proteins into SBA-15 in 15 min, the trypsin solution (pH 8) was directly added to the SBA-15 beads with immobilized proteins by centrifugation, and then the digestion was performed for 15 min at 37 degrees C. It was observed that a higher peptide sequence covering of 98% for myoglobin was obtained by MALDI-TOF/TOF analysis, compared to in-solution digestion. So the protein digestion inside SBA-15 was proved to be significantly faster and yielded a better sequence coverage. The new procedure allows for rapid protein enrichment and digestion inside SBA-15, and has great potential for protein analysis.
Rapid Communications in Mass Spectrometry 02/2006; 20(20):3139-44. · 2.79 Impact Factor
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Angewandte Chemie International Edition 12/2004; 43(44):5980-4. · 13.45 Impact Factor
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ABSTRACT: A p6m to Ia3d mesophase evolution is achieved by simply adjusting the acidity and/or anion species in the presence of block copolymers; the unusual anion sequence that affects the phase behavior of block copolymer templated mesostructured solids is revealed to be SO(4)(2-)(HSO(4)(-)) > NO(3)(-) > Br(-) > Cl(-).
Chemical Communications 10/2004; · 6.17 Impact Factor
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