Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced trieonstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conve...Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced trieonstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conveniently monitored by X-ray diffraction, transmission electron microscopy, and N2 sorption isotherms techniques. The results show mesostruetural stability of OMCs is enhanced as the carbon content increases from 36% to 46%, further increasing carbon content deteriorates the mesostructural stability. Increasing aging time from 0.5 h to 5.0 h make the mesostructural stability go through an optimum (2.0 h) and gradually reduce framework shrinkage of the OMCs. Highly OMCs can only be obtained in the acidity range of 0.2-1.2 mol/L HC1, when the acidity is near the isoelectrie point of silica, the resulting OMCs have the best mesostructure stability. Under the optimum condition, the carbon content of 46%, aging time of 2.0 h, and 0.2 mol/L HCl, the resulting OMCs have the best mesostrueture stability and the highest BET surface areas of 2281 m2/g.展开更多
In Elastic Optical Networks(EONs)with flexible bandwidth allocation,the blocking probability is high because of spectral contention.Similar to the functionality of wavelength conversion in Wavelength-Division-Multiple...In Elastic Optical Networks(EONs)with flexible bandwidth allocation,the blocking probability is high because of spectral contention.Similar to the functionality of wavelength conversion in Wavelength-Division-Multiplexing(WDM)networks,waveband conversion has been proposed to solve spectral contention in EONs.In this paper,we discuss the design of node architectures for an EON with waveband conversion.Four node architectures with shared Tuneable Waveband Converters(TWBCs)are proposed,and their blocking performances are evaluated by simulation.Simulation results show that the blocking probability of a node is significantly improved by waveband conversion.The sharing efficiency of waveband converters is also investigated.Simulation results show that at the same blocking rate,the node architecture with converters shared per node can save more than 20% waveband converters compared with that of the one with converters shared per link.展开更多
Block copolymers can yield a diverse array of nanostructures.Their assembly structures are influenced by their inherent structures,and the wide variety of structures that can be prepared especially becomes apparent wh...Block copolymers can yield a diverse array of nanostructures.Their assembly structures are influenced by their inherent structures,and the wide variety of structures that can be prepared especially becomes apparent when one considers the number of routes available to prepare block copolymer assemblies.Some examples include self-assembly,directed assembly,coupling,as well as hierarchical assembly,which can yield assemblies having even higher structural order.These assembly routes can also be complemented by processing techniques such as selective crosslinking and etching,the former technique leading to permanent structures,the latter towards sculpted and the combination of the two towards permanent sculpted structures.The combination of these pathways provides extremely versatile routes towards an exciting variety of architectures.This review will attempt to highlight destinations reached by LIU Guojun and coworkers following these pathways.展开更多
Rare-earth doped titania single-crystalline hollow nanoparticles of 20 nm are constructed via a simple sol-gel process. Amphiphilic ABA tri-block copolymers played a key role in assisting the formation of hollow struc...Rare-earth doped titania single-crystalline hollow nanoparticles of 20 nm are constructed via a simple sol-gel process. Amphiphilic ABA tri-block copolymers played a key role in assisting the formation of hollow structure, for which a hollow nanostructure growth mechanism is proposed. By introducing rare earth into the synthesis process, the as-prepared nanoparticles exhibit near-infrared light absorption properties. Photo-decomposition efficiency of Orange II azo dye can be successfully evaluated when using Yb3+-doped Ti O2 hollow nanoparticles as photocatalysts; it is more than two times higher than the pure Ti O2 hollow nanoparticles. The hollow nanostructured Yb3+-doped Ti O2 samples are exploited as photoanodes in N719- sensitized solar cells and prove able to improve the photoelectric conversion efficiency by measuring the solar cell parameters of dye-sensitized solar cells(DSSCs) under simulative sunlight.展开更多
Thin films of block copolymers (BCPs) are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-de...Thin films of block copolymers (BCPs) are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-defined structural arrangements, many of these are solvent-annealed (i.e. solvent swollen) at moderate temperatures. The use of solvents can be challenging in industry from an environmental point of view as well as having practical/cost issues. However, a simple and environmentally friendly alternative to solvo-thermal annealing for the periodically ordered nanoscale phase separated structures is described herein. Various asymmetric polystyrene-b-poly(ethylene oxide) (PS-b-PEO) thin films were annealed in a compressible fluid, supercritical carbon dioxide (scCO2), to control nanodomain orientation and surface morphologies. For the first time, periodic well defined, hexagonally ordered films with sub-25 nm pitch size were demonstrated using a supercritical fluid (SCF) process at low temperatures and pressures. Predominant swelling of PEO domains in scCO2 induces nanophase separation, scCO2 serves as green alternative to the conventional organic solvents for the phase segregation of BCPs with complete elimination of any residual solvent in the patterned film. The depressurization rate of scCO2 following annealing was found to affect the morphology of the films. The supercritical annealing conditions could be used to define nanoporous analogues of the microphase separated films without additional processing, providing a one-step route to membrane like structures without affecting the ordered surface phase segregated structure. An understanding of the BCP self- assembly mechanism can be realized in terms of the deviation in glass transition temperature, melting point, viscosity, interaction parameter and volume fraction of the constituent blocks in the scCO2 environment.展开更多
基金This work was supported by the National Natural Science Foundation of China (No.20872135).
文摘Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced trieonstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conveniently monitored by X-ray diffraction, transmission electron microscopy, and N2 sorption isotherms techniques. The results show mesostruetural stability of OMCs is enhanced as the carbon content increases from 36% to 46%, further increasing carbon content deteriorates the mesostructural stability. Increasing aging time from 0.5 h to 5.0 h make the mesostructural stability go through an optimum (2.0 h) and gradually reduce framework shrinkage of the OMCs. Highly OMCs can only be obtained in the acidity range of 0.2-1.2 mol/L HC1, when the acidity is near the isoelectrie point of silica, the resulting OMCs have the best mesostructure stability. Under the optimum condition, the carbon content of 46%, aging time of 2.0 h, and 0.2 mol/L HCl, the resulting OMCs have the best mesostrueture stability and the highest BET surface areas of 2281 m2/g.
基金supported by the National Key Basic Research Program of China (973 Program) under Grants No. 2010CB328201,No.2010CB328202the National Natural Science Foundation of China under Grants No. 60907030,No. 61275071,No. 60736003,No. 60931160439the National High Technical Research and Development Program of China (863 Program)under Grant No. 2011AA01A106
文摘In Elastic Optical Networks(EONs)with flexible bandwidth allocation,the blocking probability is high because of spectral contention.Similar to the functionality of wavelength conversion in Wavelength-Division-Multiplexing(WDM)networks,waveband conversion has been proposed to solve spectral contention in EONs.In this paper,we discuss the design of node architectures for an EON with waveband conversion.Four node architectures with shared Tuneable Waveband Converters(TWBCs)are proposed,and their blocking performances are evaluated by simulation.Simulation results show that the blocking probability of a node is significantly improved by waveband conversion.The sharing efficiency of waveband converters is also investigated.Simulation results show that at the same blocking rate,the node architecture with converters shared per node can save more than 20% waveband converters compared with that of the one with converters shared per link.
基金Guojun Liu wishes to thank NSERC of Canada for a Tier 1 Canada Research Chair and for funding
文摘Block copolymers can yield a diverse array of nanostructures.Their assembly structures are influenced by their inherent structures,and the wide variety of structures that can be prepared especially becomes apparent when one considers the number of routes available to prepare block copolymer assemblies.Some examples include self-assembly,directed assembly,coupling,as well as hierarchical assembly,which can yield assemblies having even higher structural order.These assembly routes can also be complemented by processing techniques such as selective crosslinking and etching,the former technique leading to permanent structures,the latter towards sculpted and the combination of the two towards permanent sculpted structures.The combination of these pathways provides extremely versatile routes towards an exciting variety of architectures.This review will attempt to highlight destinations reached by LIU Guojun and coworkers following these pathways.
基金financially supported by the National Natural Science Foundation of China(21201133,51272186)
文摘Rare-earth doped titania single-crystalline hollow nanoparticles of 20 nm are constructed via a simple sol-gel process. Amphiphilic ABA tri-block copolymers played a key role in assisting the formation of hollow structure, for which a hollow nanostructure growth mechanism is proposed. By introducing rare earth into the synthesis process, the as-prepared nanoparticles exhibit near-infrared light absorption properties. Photo-decomposition efficiency of Orange II azo dye can be successfully evaluated when using Yb3+-doped Ti O2 hollow nanoparticles as photocatalysts; it is more than two times higher than the pure Ti O2 hollow nanoparticles. The hollow nanostructured Yb3+-doped Ti O2 samples are exploited as photoanodes in N719- sensitized solar cells and prove able to improve the photoelectric conversion efficiency by measuring the solar cell parameters of dye-sensitized solar cells(DSSCs) under simulative sunlight.
文摘Thin films of block copolymers (BCPs) are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-defined structural arrangements, many of these are solvent-annealed (i.e. solvent swollen) at moderate temperatures. The use of solvents can be challenging in industry from an environmental point of view as well as having practical/cost issues. However, a simple and environmentally friendly alternative to solvo-thermal annealing for the periodically ordered nanoscale phase separated structures is described herein. Various asymmetric polystyrene-b-poly(ethylene oxide) (PS-b-PEO) thin films were annealed in a compressible fluid, supercritical carbon dioxide (scCO2), to control nanodomain orientation and surface morphologies. For the first time, periodic well defined, hexagonally ordered films with sub-25 nm pitch size were demonstrated using a supercritical fluid (SCF) process at low temperatures and pressures. Predominant swelling of PEO domains in scCO2 induces nanophase separation, scCO2 serves as green alternative to the conventional organic solvents for the phase segregation of BCPs with complete elimination of any residual solvent in the patterned film. The depressurization rate of scCO2 following annealing was found to affect the morphology of the films. The supercritical annealing conditions could be used to define nanoporous analogues of the microphase separated films without additional processing, providing a one-step route to membrane like structures without affecting the ordered surface phase segregated structure. An understanding of the BCP self- assembly mechanism can be realized in terms of the deviation in glass transition temperature, melting point, viscosity, interaction parameter and volume fraction of the constituent blocks in the scCO2 environment.