Faceted crystals with exposed highly reactive planes have attracted intensive investigations for applications. Herein, we demonstrate a general synthetic method to prepare mesocrystal Co3O4 with predominantly exposed ...Faceted crystals with exposed highly reactive planes have attracted intensive investigations for applications. Herein, we demonstrate a general synthetic method to prepare mesocrystal Co3O4 with predominantly exposed {111} reactive facets by the in situ thermal decomposition from Co（OH）2 nanoplatelets. The mesocrystal feature was identified by field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N2 isotherm analyses. When applied as anode material in lithium-ion batteries, mesocrystal Co3O4 nanoplatelets delivered a high specific capacity and an outstanding high rate performance. The superior electrochemical performance should be ascribed to the predominantly exposed {111} active facets and highly accessible surfaces. This synthetic strategy could be extended to prepare other mesocrystal functional nanomaterials.展开更多
A novel method was developed to deposit a large crystal diamond with good facets up to 1000 μm on a tungsten substrate using a microwave plasma enhanced chemical vapor deposition （MPCVD）. This method consists of tw...A novel method was developed to deposit a large crystal diamond with good facets up to 1000 μm on a tungsten substrate using a microwave plasma enhanced chemical vapor deposition （MPCVD）. This method consists of two steps, namely single-crystal nucleation and growth. Prior to the fabrication of the well-faceted, large crystal diamond, an investigation was made into the nucleation and growth of the diamond which were affected by the O2 concentration and substrate temperature. Deposited diamond crystals were characterized by scanning electron microscopy and micro-Raman spectroscopy. The results showed that the conditions of single-crystal nucleation were appropriate when the ratio of H2/CH4/O2 was about 200/7.0/2.0, while the sub- strate temperature Ts of 1000℃ to 1050℃ was the appropriate range for single-crystal diamond growth. Under the optimum parameters, a well-faeeted large crystal diamond was obtained.展开更多
By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime des...By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force,, both crystals （in the steady-state） transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer （LL） mode while for the apex-bulged polygonal and the deridritic crystals, it first adopts the LL mode and then transits into the multi-layer （ML） mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced.展开更多
A large diamond crystal up to 500 μm in diameter with a smooth （100） facet at its top has been synthesized on Mo substrate through microwave plasma chemical vapor deposition （MPCVD）. Its morphology and quality we...A large diamond crystal up to 500 μm in diameter with a smooth （100） facet at its top has been synthesized on Mo substrate through microwave plasma chemical vapor deposition （MPCVD）. Its morphology and quality were characterized by scanning electron microscopy （SEM）, and the growth mechanism was roughly illustrated from both macroscopic and microscopic viewpoints. It was found that morphological instabilities are a major factor resulting in synthesis of large diamond crystals, moreover, high microwave power density （MPD）, high CH4 concentrations, high pressure, high substrate surface temperature and the addition of a small amount of O2 were also necessary for the synthesis of large diamond crystals.展开更多
In this work, we report enhanced electroactivity of Co304 nanocrystals （nanocubes, NCs and truncated nano-octahedra, TNO） on the exposed {111} facets as compared to the {001} facets in relation to the surface densit...In this work, we report enhanced electroactivity of Co304 nanocrystals （nanocubes, NCs and truncated nano-octahedra, TNO） on the exposed {111} facets as compared to the {001} facets in relation to the surface density and the activity of the octahedral Com species. Transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were em- ployed to characterize the crystal facets and materials properties. The enhanced electroactivity of {111 } crystal facets was evaluated by cyclic voltammetry and amperometric titration. Our results indicate that the {111 } facets in TNO has a better electroactivity for enzymeless glucose sensing with a decent glucose sensitivity of 32.54 μA （mmol/L）-1 cm-2.展开更多
Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl4 with ascorbic acid （AA） in the presence of poly（diallyldimethylammon...Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl4 with ascorbic acid （AA） in the presence of poly（diallyldimethylammonium chloride） at room temperature. By using electron microscopy, the surfaces of the hexagram shaped Au particle were found to be {541} planes, which contain high-density steps and kinks. In addition, it was found that hexagonal shield-like and other kind of particles present in the product were analogues of the hexagram shaped Au particles structure, in that they had the same surface structure. In order to confirm the surface structure of all the prepared particles, surface structure sensitive underpotential deposition of Pb was carried out, and the cyclic voltammetric profile was in accordance with the proposed {541} surface. Finally, structure-property relationships of the Au hexagrams were experimentally analyzed by employing the electrocatalytic oxidation of AA as a probe reaction. The electrocatalytic reactions of gold cubes with low-index {100} facets and gold trioctahedra with {221} facets were studied as references. The experimental results showed that the hexagram shaped Au particles and their analogues with exposed {541} facets have the highest catalytic activity among the three kinds of gold particles, owing to the high density of kink atoms. This study should motivate us to further explore methods for the preparation of other well-defined polyhedral metal nanocrystals enclosed by high index surfaces.展开更多
Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too ...Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.展开更多
Controllable growth of anatase TiO_(2)crystals with exposed high reactive crystal facets has aroused great attention in the fields of science and technology due to their unique structure-dependent properties.Recently,...Controllable growth of anatase TiO_(2)crystals with exposed high reactive crystal facets has aroused great attention in the fields of science and technology due to their unique structure-dependent properties.Recently,much effort has been paid to synthesize anatase TiO_(2)crystals with exposed high reactive{001}facets.Herein,we review the recent progress in synthesizing{001}facets dominated anatase TiO_(2)crystals with different morphologies by various synthetic methods.Furthermore,our review is mainly focused on the formation/etching mechanisms of{001}facets dominated anatase TiO_(2)crystals based on our and other studies.The extensive application potentials of the anatase TiO_(2)crystals with exposed{001}facets have been summarized in this review such as photocatalysis,photoelectrocatalysis,solar energy conversion,lithium ion battery,and hydrogen generation Based on the current studies,we give some perspectives on the research topic.We believe that this comprehensive review on anatase TiO_(2)crystals with high reactive{001}facets can further promote the relative research in this field.展开更多
文摘Faceted crystals with exposed highly reactive planes have attracted intensive investigations for applications. Herein, we demonstrate a general synthetic method to prepare mesocrystal Co3O4 with predominantly exposed {111} reactive facets by the in situ thermal decomposition from Co（OH）2 nanoplatelets. The mesocrystal feature was identified by field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N2 isotherm analyses. When applied as anode material in lithium-ion batteries, mesocrystal Co3O4 nanoplatelets delivered a high specific capacity and an outstanding high rate performance. The superior electrochemical performance should be ascribed to the predominantly exposed {111} active facets and highly accessible surfaces. This synthetic strategy could be extended to prepare other mesocrystal functional nanomaterials.
基金supported by the Natural Science Foundation of Hubei Province of China(2008CDB255)the Educational Commission of Hubei Province of China(No.Q20081505)the Key Laboratory for Green Chemical Process of the Ministry of Education of China (No.RGCT200801)
文摘A novel method was developed to deposit a large crystal diamond with good facets up to 1000 μm on a tungsten substrate using a microwave plasma enhanced chemical vapor deposition （MPCVD）. This method consists of two steps, namely single-crystal nucleation and growth. Prior to the fabrication of the well-faceted, large crystal diamond, an investigation was made into the nucleation and growth of the diamond which were affected by the O2 concentration and substrate temperature. Deposited diamond crystals were characterized by scanning electron microscopy and micro-Raman spectroscopy. The results showed that the conditions of single-crystal nucleation were appropriate when the ratio of H2/CH4/O2 was about 200/7.0/2.0, while the sub- strate temperature Ts of 1000℃ to 1050℃ was the appropriate range for single-crystal diamond growth. Under the optimum parameters, a well-faeeted large crystal diamond was obtained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.54175378,51474176,and 51274167)the Natural Science Foundation o Shaanxi Province,China(Grant No.2014JM7261)the Doctoral Foundation Program of Ministry of China(Grant No.20136102120021)
文摘By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force,, both crystals （in the steady-state） transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer （LL） mode while for the apex-bulged polygonal and the deridritic crystals, it first adopts the LL mode and then transits into the multi-layer （ML） mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced.
基金supported by National Natural Science Foundation of China(No.11175137)
文摘A large diamond crystal up to 500 μm in diameter with a smooth （100） facet at its top has been synthesized on Mo substrate through microwave plasma chemical vapor deposition （MPCVD）. Its morphology and quality were characterized by scanning electron microscopy （SEM）, and the growth mechanism was roughly illustrated from both macroscopic and microscopic viewpoints. It was found that morphological instabilities are a major factor resulting in synthesis of large diamond crystals, moreover, high microwave power density （MPD）, high CH4 concentrations, high pressure, high substrate surface temperature and the addition of a small amount of O2 were also necessary for the synthesis of large diamond crystals.
基金financial support from the University of Queenslandthe support of the Centre for Microscopy and Microanalysis at the University of Queensland through their facilities,and the scientific and technical assistance
文摘In this work, we report enhanced electroactivity of Co304 nanocrystals （nanocubes, NCs and truncated nano-octahedra, TNO） on the exposed {111} facets as compared to the {001} facets in relation to the surface density and the activity of the octahedral Com species. Transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were em- ployed to characterize the crystal facets and materials properties. The enhanced electroactivity of {111 } crystal facets was evaluated by cyclic voltammetry and amperometric titration. Our results indicate that the {111 } facets in TNO has a better electroactivity for enzymeless glucose sensing with a decent glucose sensitivity of 32.54 μA （mmol/L）-1 cm-2.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 20725310, 21021061, and 21073145）, the National Basic Research Program of China （Grant No. 2007CB815303 and 2009CB939804） and Program for New Century Excellent Talents in Fujian Province Universities.
文摘Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl4 with ascorbic acid （AA） in the presence of poly（diallyldimethylammonium chloride） at room temperature. By using electron microscopy, the surfaces of the hexagram shaped Au particle were found to be {541} planes, which contain high-density steps and kinks. In addition, it was found that hexagonal shield-like and other kind of particles present in the product were analogues of the hexagram shaped Au particles structure, in that they had the same surface structure. In order to confirm the surface structure of all the prepared particles, surface structure sensitive underpotential deposition of Pb was carried out, and the cyclic voltammetric profile was in accordance with the proposed {541} surface. Finally, structure-property relationships of the Au hexagrams were experimentally analyzed by employing the electrocatalytic oxidation of AA as a probe reaction. The electrocatalytic reactions of gold cubes with low-index {100} facets and gold trioctahedra with {221} facets were studied as references. The experimental results showed that the hexagram shaped Au particles and their analogues with exposed {541} facets have the highest catalytic activity among the three kinds of gold particles, owing to the high density of kink atoms. This study should motivate us to further explore methods for the preparation of other well-defined polyhedral metal nanocrystals enclosed by high index surfaces.
基金Financial support from the following projects and organisa- tions are acknowledged： the China One Thousand Talent Scheme, the National Natural Science Foundation of China （NNSFC） under its Major Research Scheme of Meso-scale Mechanism and Control in Multi-phase Reaction Processes （project reference： 91434126）, the Natural Science Foundation of Guangdong Province （project reference： 2014A030313228）, the UK Engineering and Physical Sciences Research Council （EPSRC） for the projects of Shape （EP/C009541） and StereoVision （EP/E045707）, and the Technology Strategy Board （TSB） for the project of High Value Manufacturing CGM （TP/BD059E）.
文摘Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.
基金supported by Australian Research Council(ARC)Discovery Project
文摘Controllable growth of anatase TiO_(2)crystals with exposed high reactive crystal facets has aroused great attention in the fields of science and technology due to their unique structure-dependent properties.Recently,much effort has been paid to synthesize anatase TiO_(2)crystals with exposed high reactive{001}facets.Herein,we review the recent progress in synthesizing{001}facets dominated anatase TiO_(2)crystals with different morphologies by various synthetic methods.Furthermore,our review is mainly focused on the formation/etching mechanisms of{001}facets dominated anatase TiO_(2)crystals based on our and other studies.The extensive application potentials of the anatase TiO_(2)crystals with exposed{001}facets have been summarized in this review such as photocatalysis,photoelectrocatalysis,solar energy conversion,lithium ion battery,and hydrogen generation Based on the current studies,we give some perspectives on the research topic.We believe that this comprehensive review on anatase TiO_(2)crystals with high reactive{001}facets can further promote the relative research in this field.
