Co-reporter:Gailing Huang;Shulan Ma;Hongliang Kang;Hui Ma;Yongxiang Bai;Yongliang Li
The Journal of Physical Chemistry C May 28, 2009 Volume 113(Issue 21) pp:9157-9163
Publication Date(Web):Publication Date (Web): April 29, 2009
DOI:10.1021/jp900861k
Nanosheets exfoliated from layered inorganic crystals can be regarded as inorganic macromolecules. Herein, coassembly of layered double hydroxide (LDH) nanosheets with carboxymethyl cellulose (CMC) was presented. CHN analysis, XRD, FTIR, TG-DSC and SEM were employed to characterize the coassembly process. The results showed that the colloidal suspension of the exfoliated MgAl−LDH nanosheets in formamide were restacked when in contact with water. Nevertheless, CMC can prevent the colloidal state from flocculation even after all included formamide molecules were removed by water, that is the interaction of CMC molecules and the nanosheets stabilized the dispersion in aqueous media. Drying at 40 °C led the nanosheets and CMC to restack to a layered nanocomposite with a basal spacing of 1.75 nm, indicating a bilayer arrangement of CMC in the interlayer. The thermal degradation temperature of CMC in the composite was raised by about 160 °C.
Co-reporter:Xianjun Niu;Yi-en Du;Yufang Liu;Hongxue Qi;Jing An;Qi Feng
RSC Advances (2011-Present) 2017 vol. 7(Issue 40) pp:24616-24627
Publication Date(Web):2017/05/05
DOI:10.1039/C7RA03707D
Truncated tetragonal bipyramid anatase TiO2 nanocrystals enclosed by {001}, {010} and {101} facets, and tetragonal cuboid anatase TiO2 nanocrystals with co-exposed [111]- and {101} facets were hydrothermally synthesized by using the H+-form of the tetratitanate H2Ti4O9 as the precursor and HF and H2O2 as the capping agent and solvent, respectively. The as-prepared anatase TiO2 nanocrystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and nitrogen adsorption/desorption measurements. The transformation from the layered structure of tetratitanate HTO to anatase TiO2 nanocrystals may experience two types of reactions including in situ topotactic transformation reaction by splitting the Ti–O–Ti bonds of the corner-shared by two TiO6 octahedra along the [010]-direction of the HTO, and the dissolution–recrystallisation reaction along various crystal planes of the zigzag ribbon-like anatase crystal during the hydrothermal reaction process. Furthermore, the photocatalytic activities of the as-prepared anatase nanocrystals were evaluated by the photocatalytic degradation of methylene blue under UV-light irradiation at room temperature in air. Truncated tetragonal bipyramid and cuboid coexistence of anatase TiO2 nanocrystals with a large percentage of co-exposed high-energy {001}, {010} and [111]-facets exhibit high surface photocatalytic activities for the degradation amount of MB per unit surface area of catalyst (mg (MB) per m2 (TiO2 surface area)), which can be explained by the cooperative mechanism of the surface atomic structure and surface electronic structure of the different facets.
Co-reporter:Xianjun Niu;Yi-en Du;Yufang Liu;Hongxue Qi;Jing An;Qi Feng
RSC Advances (2011-Present) 2017 vol. 7(Issue 40) pp:24616-24627
Publication Date(Web):2017/05/05
DOI:10.1039/C7RA03707D
Truncated tetragonal bipyramid anatase TiO2 nanocrystals enclosed by {001}, {010} and {101} facets, and tetragonal cuboid anatase TiO2 nanocrystals with co-exposed [111]- and {101} facets were hydrothermally synthesized by using the H+-form of the tetratitanate H2Ti4O9 as the precursor and HF and H2O2 as the capping agent and solvent, respectively. The as-prepared anatase TiO2 nanocrystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and nitrogen adsorption/desorption measurements. The transformation from the layered structure of tetratitanate HTO to anatase TiO2 nanocrystals may experience two types of reactions including in situ topotactic transformation reaction by splitting the Ti–O–Ti bonds of the corner-shared by two TiO6 octahedra along the [010]-direction of the HTO, and the dissolution–recrystallisation reaction along various crystal planes of the zigzag ribbon-like anatase crystal during the hydrothermal reaction process. Furthermore, the photocatalytic activities of the as-prepared anatase nanocrystals were evaluated by the photocatalytic degradation of methylene blue under UV-light irradiation at room temperature in air. Truncated tetragonal bipyramid and cuboid coexistence of anatase TiO2 nanocrystals with a large percentage of co-exposed high-energy {001}, {010} and [111]-facets exhibit high surface photocatalytic activities for the degradation amount of MB per unit surface area of catalyst (mg (MB) per m2 (TiO2 surface area)), which can be explained by the cooperative mechanism of the surface atomic structure and surface electronic structure of the different facets.
Co-reporter:Dejian Du, Wenbo Yue, Shengtang Liu, Xiaojing Yang
Journal of Alloys and Compounds 2017 Volume 716(Volume 716) pp:
Publication Date(Web):5 September 2017
DOI:10.1016/j.jallcom.2017.05.034
•Amorphous TiO2 nanofilms are fabricated by hydrolysis of tetrabutyl titanate on the surface of graphene.•TiO2 nanofilms are broken in some regions to form crystalline TiO2 nanoparticles after annealing under N2.•TiO2-coated graphene shows superior electrochemical performance compared to pure graphene.•TiO2-coated graphene can be used as flexible anode materials due to the amorphous nature of TiO2 coating.As a novel anode material for lithium-ion batteries, graphene has a higher theoretical capacity than graphite. However, the practical application of graphene suffers from a low coulombic efficiency and poor cycle stability due to the unstable solid electrolyte interphase layer. In this work, ultrathin amorphous TiO2 nanofilm-coated graphene is fabricated by controlled hydrolysis of tetrabutyl titanate on the surface of graphene, and shows superior cycle and rate performance compared to uncoated graphene because amorphous TiO2 nanofilms can prevent the detachment of graphene nanosheets and avoids the formation of thick and unstable solid-electrolyte interphase layers during cycling. Moreover, the electrochemical performance of TiO2-coated graphene can be further improved by controllable calcination of TiO2-coated graphene under a N2 atmosphere. The produced porosity of TiO2 nanofilms after calcination can improve both Li+ and electron transport, leading to the further improved lithium storage performance of graphene. This novel synthesis strategy may be employed in other graphene-based anode materials for high-performance lithium-ion batteries and other electrochemical devices.Download high-res image (318KB)Download full-size image
Co-reporter:Siqi Zhang, Rong Lin, Wenbo Yue, Fangzhou Niu, Jie Ma, Xiaojing Yang
Chemical Engineering Journal 2017 Volume 314(Volume 314) pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.cej.2016.12.123
•Ni3S2 nanoparticles with a diameter of ∼5 nm are well-dispersed inside the pores of CMK-3.•Pure Ni3S2 and ZnS can be controllably prepared by adjusting the dosage of H2SO4.•CMK-3 with enlarged mesopores can be formed after removal of Ni3S2 nanoparticles.•Ni3S2-loaded CMK-3 exhibits superior electrochemical performance compared to pure Ni3S2.Many metal sulfides with high theoretical capacities are potential anode materials for lithium-ion batteries. However, the low electronic conductivity and large volume change of metal sulfides during cycling seriously hamper their practical applications. Herein, we report a novel and scalable strategy to synthesize well-dispersed Ni3S2 (∼5 nm) inside porous carbon (CMK-3) by using mesoporous silica (SBA-15) as the template. CMK-3 offers not only good electronic conductivity but also mesopores to accommodate the volume variation of Ni3S2, leading to outstanding electrochemical performance of Ni3S2-loaded CMK-3. To show the versatility of this novel method, ZnS-loaded CMK-3 is also prepared. However, most ZnS nanoparticles are formed outside the pores of CMK-3 with regard to high loading amount. It is inferred that the intermediate product Zn would melt and migrate to the outer surface of CMK-3 prior to the formation of ZnS. This novel synthesis method may offer an attractive pathway to metal sulfide-loaded porous carbon with high lithium storage capacity.Download high-res image (214KB)Download full-size image
Co-reporter:Dujuan Liang;Xin Peng;Yanan Li;Huiliang Wang
Advanced Materials Interfaces 2017 Volume 4(Issue 20) pp:
Publication Date(Web):2017/10/01
DOI:10.1002/admi.201700740
AbstractA large specific surface area is one of the most attractive features of 2D crystals. However, the surfaces/interfaces of the 2D crystals of delaminated layered double hydroxides (LDHs) cannot be efficiently utilized because they are naturally unstable, and their surfaces cannot be highly exposed using current isolation methods. This study proposes a new strategy in this work to isolate LDH 2D crystals with large surface exposure by forming polymer gels. The gels are synthesized by combining ZnAl-LDH unilamellae with acrylic acid anions (AA−) in delaminating solvent and mixing the solution with acrylamide (AAm) monomers for in situ copolymerization. The results show that the AA− inhibits the dissolution of the unilamellae in formamide and that the polymer chains fix the unilamellae in the gel network. This stabilization effect results from the anchoring bonds of the COO− groups with the LDH layer. It is found that the AA−-containing gels without LDH have adsorptivity toward phosphate, whereas the poly-AAm gel possesses hardly any adsorptivity. The nanocomposite hydrogels show phosphate adsorption amounts close to the theoretical values calculated according to the contents of AA− and LDH. This implies that nearly all the unilamellar LDH surfaces are exposed to phosphate.
Co-reporter:Pingping Feng;Baiyi Shao;Xinying Wang
European Journal of Inorganic Chemistry 2017 Volume 2017(Issue 41) pp:4861-4865
Publication Date(Web):2017/11/09
DOI:10.1002/ejic.201700825
We report that 2D crystals, prepared by delamination of layered terbium hydroxide (LTbH) intercalated with dodecyl sulfate ions (DS–) in formamide, can be modified by DS– ions and further restacked to a new layer-structured compound. The modification proceeds in situ in formamide through the substitution of DS– for the hydroxyl groups, which coordinate to Tb3+ upon the delamination of the LTbH layer. With the supplementary addition of DS–, the substitution reaction progresses to a large degree of substitution, m > 2 in the chemical formula Tb2(OH)6–mDSm·nH2O. Since the negatively charged SO42– heads of DS– anchor to Tb3+, the alkyl chains protruding outwards convert the 2D crystal from hydrophilic to hydrophobic. The modified 2D crystals aggregate in aqueous media, restacking to the layered rare-earth compound characteristic of m greater than 2. The restacked crystals are ready to delaminate in some organic solvents owning to their structural and hydrophobic features.
Co-reporter:Dejian Du, Wenbo Yue, Xialu Fan, Kun Tang, Xiaojing Yang
Electrochimica Acta 2016 Volume 194() pp:17-25
Publication Date(Web):10 March 2016
DOI:10.1016/j.electacta.2016.02.085
•Ultrathin NiO/NiFe2O4 nanoplates derived from NiFe layered double hydroxides are fabricated on the graphene.•NiO/NiFe2O4 nanoplates on the graphene show superior electrochemical performance compared to pure NiO/NiFe2O4 aggregates.•The effects of the content and the particle size/component of NiO/NiFe2O4 on the electrochemical performances are studied.•Graphene-encapsulated NiO/NiFe2O4 is prepared and shows slightly decreased performance compared to graphene-based composite.As anode materials for lithium-ion batteries, bicomponent metal oxide composites show high reversible capacities; but the morphology and particle size of the composites are hardly controllable, which may reduce their electrochemical properties. In this work, ultrathin NiO/NiFe2O4 nanoplates with a diameter of 5 ∼ 7 nm and a thickness of ∼2 nm are controllably fabricated on the graphene derived from NiFe layered double hydroxides (NiFe-LDHs), and exhibit superior electrochemical performance compared to pure NiO/NiFe2O4 aggregates without graphene. The nanosized NiO and NiFe2O4 plates are separated from each other and the graphene substrate can prevent the aggregation of NiO/NiFe2O4 as well as enhance the electronic conductivity of the composite, which is beneficial to improving the electrochemical performance. Moreover, the effects of the content and the particle size/component of NiO/NiFe2O4 on the electrochemical performances are also studied in order to achieve optimal performance. Ultrathin NiO/NiFe2O4 nanoplates are further encapsulated by graphene nanosheets and show slightly decreased performance compared to those supported by graphene nanosheets. The different electrochemical behaviors of graphene-containing composites may be attributed to the different interactions between graphene nanosheets and NiO/NiFe2O4 nanoplates.
Co-reporter:Hong Wu, Huifeng Li, Genban Sun, Shulan Ma and Xiaojing Yang
Journal of Materials Chemistry A 2015 vol. 3(Issue 21) pp:5457-5466
Publication Date(Web):27 Apr 2015
DOI:10.1039/C5TC00778J
Face-centered cubic α-LiFeO2 and spinel β-LiFe5O8 with uniform size and high dispersion have been successfully assembled on 2D graphene sheets via a facile one-pot strategy under different reaction conditions. The reduction of GO by this method is effective and comparable to conventional methods, which was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The structure of the products can be easily controlled by changing the solvent and reaction temperature. It was shown that the as-formed β-LiFe5O8 and α-LiFeO2 nanocrystals with a diameter of ca. 5 nm and 7 nm, respectively, were densely and uniformly anchored on the graphene sheets, and as a result, the aggregation of the nanoparticles was effectively prevented. The investigation of the microwave absorbability reveals that the α-LiFeO2–GN and β-LiFe5O8–GN nanocomposites exhibit excellent microwave absorbability, which is stronger than that of the corresponding α-LiFeO2 and β-LiFe5O8 nanostructures, respectively.
Co-reporter:Yi-en Du, Dejian Du, Qi Feng, and Xiaojing Yang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 15) pp:7995
Publication Date(Web):March 30, 2015
DOI:10.1021/acsami.5b00227
{010}-Facet-exposed anatase TiO2 crystals exhibit the highest photoreactivity among the exposed facets. To obtain a higher exposure rate of this facet, the work investigated the transformation of the nanosheets with cavities within the layers derived from a rock-salt-structured Li2TiO3 precursor. All the lithium ions were extracted from the precursor by H+/Li+ ion exchange in HCl aqueous solutions, and after tetramethylammonium ions were intercalated, the precursor can delaminated into the nanosheets. The [TiO3]2– nanosheets were hydrothermally treated under different temperatures and pH values. The results showed that the anatase phase was formed in a wider range of pH and temperature, compared with using nanoribbons of [Ti4O9]2– and nanosheets of [Ti1.73O4]1.07–. At low pH, [111]-faceted nanorod-shaped anatase nanocrystals were formed preferentially, and the nanocrystals preferentially grow along the [001] direction with the increase of solution pH, leading to a large percentage of {010} facets on their surface. The photocatalytic activity increases with the increase of exposure rate of {010} facets.Keywords: anatase TiO2; exposure rate; photocatalysis; [111] facets; {010} facets;
Co-reporter:Dujuan Liang, Wenbo Yue, Genban Sun, Dong Zheng, Kenta Ooi, and Xiaojing Yang
Langmuir 2015 Volume 31(Issue 45) pp:12464-12471
Publication Date(Web):October 27, 2015
DOI:10.1021/acs.langmuir.5b03428
Two-dimensional (2D) materials, such as graphene, inorganic oxides, and hydroxides, are one of the most extensively studied classes of materials due to their unilamellar crystallites or nanosheet structures. In this study, instead of using the universal exfoliation method of the bulky crystal precursor, 2D crystals/nanosheets of MgAl-layered double hydroxides (LDHs) were synthesized in formamide. We propose that the obtained crystals are unilamellar according to the XRD, TEM, and AFM observations. The HRTEM and fast Fourier transform images confirm that the crystal structures are the same as those of the exfoliated MgAl-LDH nanosheets. The directly synthesized sheets can stack into a 3D crystal structure, which is the same as that of typical LDHs except for the disordered orientation of the a-/b- crystal axis of each sheet. This result provides not only a novel approach to the preparation of 2D crystals but also insight into the formation mechanism of LDHs.
Co-reporter:Yi-en Du, Qi Feng, Changdong Chen, Yasuhiro Tanaka, and Xiaojing Yang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 18) pp:16007
Publication Date(Web):August 26, 2014
DOI:10.1021/am503914q
The morphology and exposed facet of the anatase-type TiO2 are very important to improve the photocatalytic activity and photovoltaic performance in dye-sensitized solar cells. In this work, we report the synthesis and the photocatalytic and dye-sensitized solar cell performances of anatase-type TiO2 single nanocrystals with exposed {010}- and [111]-facets and with various morphologies by using exfoliated tetratitanate nanoribbons as precursors. The precursor nanoribbons were prepared from the exfoliation of the protonated and, subsequently, tetramethylammonium/H+ ion-exchanged K2Ti4O9. The colloidal suspension containing the nanoribbons was hydrothermally heated with a microwave-assistance at temperatures from 120 to 190 °C after pH was adjusted to 0.5–14. The dependence of the crystalline phases on temperature and pH indicated that anatase single phase can be obtained at pH 3–13 whereas temperatures higher than 160 °C. The [111]-faceted nanorod-shaped anatase nanocrystals were formed preferentially at pH ≤ 3, whereas the {010}-faceted anatase nanocrystals with morphologies of rhombic, cuboid, and spindle were preferentially at pH ≥5. The morphology observation revealed that the nanoribbons were transformed to anatase nanocrystals mainly by the topotactic structural transformation reaction accompanied by an Ostwald ripening reaction, and pH of the reaction solution took a critical role in the crystal morphology change. At pH ≤1, the mixture of anatase, rutile, and brookite were obtained at higher temperature conditions. The photocatalytic activity and photovoltaic performance were enhanced in an order of surface without a specific facet < [111]-faceted surface < {010}-faceted surface.Keywords: anatase TiO2; dye-sensitized solar cell; photocatalysis; [111]-faceted; {010}-faceted
Co-reporter:Dejian Du;Wenbo Yue;Yu Ren
Journal of Materials Science 2014 Volume 49( Issue 23) pp:8031-8039
Publication Date(Web):2014 December
DOI:10.1007/s10853-014-8510-y
Bicomponent CoO/CoFe2O4 composites with tunable particle sizes are prepared using Co–Fe layered double hydroxides (LDHs) or Co–Fe hydroxides as precursors. Moreover, graphene-encapsulated CoO/CoFe2O4 composites (labeled as G-CoO/CoFe2O4) are fabricated by co-assembly of graphene oxide nanosheets and Co–Fe LDHs/hydroxides, and then thermal decomposition of Co–Fe LDHs/hydroxides. Compared to uncoated CoO/CoFe2O4, G-CoO/CoFe2O4 composites exhibit enhanced cycle performances and rate capabilities. The superior performance may be attributed to the graphene encapsulation that prevents the aggregation of CoO/CoFe2O4 particles, buffers the strain from the volume variation of CoO/CoFe2O4, and improves the electronic conductivity of the composite electrode. The electrochemical properties of G-CoO/CoFe2O4 can be further improved by reducing the particle size of CoO/CoFe2O4 due to the enlarged interface between graphene nanosheets and CoO/CoFe2O4 particles.
Co-reporter:Sheng Yang;Wenbo Yue;Jia Zhu;Yu Ren
Advanced Functional Materials 2013 Volume 23( Issue 28) pp:3570-3576
Publication Date(Web):
DOI:10.1002/adfm.201203286
Abstract
Graphene-based metal oxides generally show outstanding electrochemical performance due to the superior properties of graphene. However, the aggregation of active metal oxide nanoparticles on the graphene surface may result in a capacity fading and poor cycle performance. Here, a mesostructured graphene-based SnO2 composite is prepared through in situ growth of SnO2 particles on the graphene surface using cetyltrimethylammonium bromide as the structure-directing agent. This novel mesoporous composite inherits the advantages of graphene nanosheets and mesoporous materials and exhibits higher reversible capacity, better cycle performance, and better rate capability compared to pure mesoporous SnO2 and graphene-based nonporous SnO2. It is concluded that the synergetic effect between graphene and mesostructure benefits the improvement of the electrochemical properties of the hybrid composites. This facile method may offer an attractive alternative approach for preparation of the graphene-based mesoporous composites as high- performance electrodes for lithium-ion batteries.
Co-reporter:Yushuang Zhao, Ji-Guang Li, Mengxi Guo and Xiaojing Yang
Journal of Materials Chemistry A 2013 vol. 1(Issue 22) pp:3584-3592
Publication Date(Web):11 Apr 2013
DOI:10.1039/C3TC30205A
Rare-earth phosphors with tunable optical properties are used in display panels and fluorescent lamps and have potential applications in lasers and bioimaging. This work reported the preparation, structure and photoluminescence of the unilamellar nanosheets containing Tb3+/Eu3+ delaminated from layered rare-earth hydroxides (LRHs). Highly crystallized LTbH and LEuH with monolayered dodecyl sulfate ions vertical to the layer were synthesized by a one-step homogeneous precipitation method for the first time, and were shown to be readily delaminated in formamide. The obtained unilamellar nanosheets exhibited a decrease of the coordination number of the lanthanide ions, to probably 8-fold, when compared with the bulky precursor crystals. This change resulted in different photoluminescence emission peak shapes. Colloidal hybrids were constructed using these nanosheets as building blocks, and the emission colors of the hybrids can be facilely and precisely tuned from green to yellow, orange, and finally to red by controlling the relative contents of the two kinds of nanosheets. This method provides a novel and simple route to prepare color-tunable hybrid materials from 2-dimensional crystals.
Co-reporter:Wenbo Yue, Sheng Yang, Yu Ren, Xiaojing Yang
Electrochimica Acta 2013 Volume 92() pp:412-420
Publication Date(Web):1 March 2013
DOI:10.1016/j.electacta.2013.01.058
Graphene-based metals or metal oxides commonly show outstanding electrochemical performance due to superior properties of graphene. However, it still remains a challenge to directly grow low-valence oxides (e.g. tin monoxide) on graphene surface in term of the oxidizability of graphene oxide, which is normally adopted as a precursor for graphene. Herein, we report a novel strategy for preparation of tin and tin monoxide on graphene nanosheets by selectively using the reducing agent and the precipitant. Moreover, in contrast to free particles formed in solution, nanoscale tin or tin monoxide particles well-dispersed on graphene exhibited enhanced electro-chemical properties, including higher reversible capacities, better cycle performances, and higher rate capabilities. This facile one-step method may provide an attractive alternative approach for preparation of high-performance electrodes consisting of graphene and low-valence compounds.Graphical abstractHighlights► Sn and its oxides (SnO, SnO2) can be controllably synthesized on graphene surface. ► This is the first report of synthesis of graphene-SnO and its electrochemical property. ► Graphene-Sn and graphene-SnO exhibit enhanced electrochemical performances.
Co-reporter:Yi He, Qi Feng, Siqi Zhang, Qingli Zou, Xianling Wu, and Xiaojing Yang
ACS Sustainable Chemistry & Engineering 2013 Volume 1(Issue 6) pp:570
Publication Date(Web):April 3, 2013
DOI:10.1021/sc400056w
The lithium resource is becoming increasingly scarce due to the increasing use of lithium ion secondary batteries. To obtain LiMnO2, however, using a hydrothermal method, a high concentration of LiOH is required, namely, Li/Mn molar ratios in raw materials that are usually larger than 13. In this letter, we present a new strategy for drastically lowering the Li dosage based on the fact that the LiOH solubility is high in water but sparingly soluble in ethanol. Well-crystallized LiMnO2 nanocrystals can be produced in miscible solvents with a Li/Mn molar ratio as low as 1.05. The results strongly suggest that a high Li+ concentration in the water phase would be beneficial for manganese oxides to form a layered structure, while the reactivity of Li+ accelerates its reaction with Mn2O3.Keywords: Li/Mn molar ratio; Lithium dosage; o-LiMnO2; Solvothermal synthesis
Co-reporter:Yahong Sun;Nankai Chu;Qingyang Gu;Guohua Pan;Genban Sun;Shulan Ma
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 1) pp:32-38
Publication Date(Web):
DOI:10.1002/ejic.201201048
Abstract
The organic sensitizer terephthalic acid and its anion terephthalate (TA) were introduced into the galleries of europium-doped layered yttrium hydroxide (LYH:Eu). In contrast to using water as solvent, the use of formamide resulted in the introduction of more organic guests and markedly enhanced the Eu3+ luminescence. Formamide prevented water from entering the system, leading to an excess of terephthalic acid molecules, and more efficient coordination of the TA guest with the Eu3+ in the layers of the composite, all of which may have contributed to the enhanced Eu3+ luminescence.
Co-reporter:Shulan Ma;Juan Wang;Li Du;Cuihong Fan;Yahong Sun;Genban Sun
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 8) pp:1363-1370
Publication Date(Web):
DOI:10.1002/ejic.201200847
Abstract
Co-assembly of inorganic LDH nanosheets with an organic azacrown ether carboxylic acid derivative was studied by a flocculation method. The homogeneous structure seen in the wet state changed markedly after drying: a staging structure transformed into a homogeneous one after increased assembly times. The experimental observations, changeover from homogeneous to staging and unequal charges of organic and inorganic guests in gallery, might suggest the Daumas–Hérold model applicable in LDH system. The composites with staging could function as powerful water adsorption materials with facile reversibility.
Co-reporter:Yi He, Fengmei Yuan, Hui Ma, Xuedong Bai, Xiaojing Yang
Journal of Alloys and Compounds 2013 Volume 569() pp:67-75
Publication Date(Web):25 August 2013
DOI:10.1016/j.jallcom.2013.03.187
•Layered LiMn1−xAlxO2 was synthesized by a facile hydrothermal treatment.•With increasing x, the ZMn values in LiMn1−xAlxO2 were larger than 3.•The Al3+ concentration played an important role in morphology of the products.•The electrochemical property of LiMn1−xAlxO2 was improved comparing with LiMnO2.Orthorhombic LiMn1–xAlxO2 nanocrystals (Pmmn (59), origin choice 2) with different morphologies were successfully synthesized using Mn2O3 and Al2O3 as Mn- and Al-sources in a 3.5 M LiOH aqueous solution hydrothermally treated at 150 °C. Although Al3+ ions introduced into the starting hydrothermal solution was in a large amount from 0 to 0.33 of Al/Mn molar ratio, noted as Al/Mn(HT) where HT refers to hydrothermal treatment; the ratio was as low as 0.05 in the phase-pure LiMn1–xAlxO2 crystals, noted as Al/Mn(SS) where SS refers to solid solution, while a Al/Mn(HT) ratio higher than 0.5 resulted in the formation of orthorhombic LiAlO2 phase. With an increase of Al/Mn(SS), the average oxidation number was higher than 3 and gradually increased, leading to a monotonous shrinkage of the unit cell along a-axis (the zigzag direction of the metal-oxygen octahedron layers). Furthermore, Al3+ also influenced on the morphology of the crystals: (1) cuboid shaped crystals as (Al/Mn(SS) < 0.02), with the ascendant growth in the direction vertical to the layer; and (2) cubic-like crystals as Al/Mn(SS) > 0.02 can be obtained. Galvanostatic measurement exhibited that the capacity of the electrode composed of Li0.93Mn0.96Al0.04O2 can reach a discharge capacity of 175 mAh/g at a current density of 0.1C and the capacity retention could be 82.9% after 25th cycling, showing that Al3+ can stabilize the layered structure by retarding its transforming to spinel one.
Co-reporter:Wenbo Yue, Sheng Yang, Yunling Liu, Xiaojing Yang
Materials Research Bulletin 2013 48(4) pp: 1575-1580
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.12.046
Co-reporter:Yahong Sun, Guohua Pan, Qingyang Gu, Xinxin Li, Genban Sun, Shulan Ma, Xiaojing Yang
Materials Research Bulletin 2013 48(11) pp: 4460-4468
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.07.053
Co-reporter:Tingting Chen, Fang Deng, Jia Zhu, Caifeng Chen, Genban Sun, Shulan Ma and Xiaojing Yang
Journal of Materials Chemistry A 2012 vol. 22(Issue 30) pp:15190-15197
Publication Date(Web):13 Jun 2012
DOI:10.1039/C2JM31171B
Hexagonal close-packed Ni (h-Ni) nanocrystals and face-centered cubic Ni (c-Ni) nanoflowers with uniform size and high dispersion have been successfully assembled on graphene nanosheets (GN) via a facile one-step solution-phase strategy under different reaction conditions, where the reduction process of graphite oxide (GO) sheets into GN was accompanied by the generation of Ni nanocrystals. The reduction of GO by this method is effective, which was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy and is comparable to conventional methods. The phase and morphology of nickel can be easily tuned by varying the reaction temperature and solvent. It was shown that the as-formed h-Ni nanocrystals with a diameter as small as 3 nm are grown densely and uniformly on the graphene sheets, and as a result the aggregation of the h-Ni nanocrystals was effectively prevented. In addition, c-Ni nanospheres assembled by c-Ni nanocrystals with a size of 15 nm were also uniformly deposited on the graphene sheets. The investigation of the microwave absorbability reveals that the three Ni/GN nanocomposites exhibit excellent microwave absorbability, which is stronger than the corresponding Ni nanostructures.
Co-reporter:Wenbo Yue, Zhenzhen Lin, Shuhua Jiang and Xiaojing Yang
Journal of Materials Chemistry A 2012 vol. 22(Issue 32) pp:16318-16323
Publication Date(Web):22 Jun 2012
DOI:10.1039/C2JM30805C
Graphene-encapsulated mesoporous metal oxides (e.g. Co3O4, Cr2O3 and NiO) as novel anode materials for lithium-ion batteries were simply synthesized by adjusting the pH of mesoporous metal oxides and graphene oxide suspensions to set values (e.g. 5–6 for metal oxides, 7–8 for graphene oxide) and mixing the two suspensions in the presence of reducing agents. These composites synthesized by this facile method exhibited superior electrochemical performance, including remarkably high capacity, high rate capability and excellent cycle performance. The improved performance may be attributed to the high dispersion of mesoporous particles separated by graphene nanosheets and the high electrical conductivity of graphene.
Co-reporter:Yushuang Zhao, Ji-Guang Li, Fang Fang, Nankai Chu, Hui Ma and Xiaojing Yang
Dalton Transactions 2012 vol. 41(Issue 39) pp:12175-12184
Publication Date(Web):13 Aug 2012
DOI:10.1039/C2DT31249B
Highly crystalline Eu3+-incorporated MgAl layered double hydroxides (LDHs) were synthesized by the homogeneous precipitation method. For the crystals as-prepared, after their calcination from 200–1000 °C, and, further, after restoration in a Na2CO3 solution, the structural and luminescent changes were investigated for the first time. Eu3+ ions with a coordination number of, probably, 8, were incorporated into the hydrotalcite layer, which led to a basal spacing (dbasal) increase, microstrain formation, and crystalline morphology imperfections, while retaining the original lattice symmetry, Rm. In the deconstruction process due to calcination, the Eu3+ ions restrained the formation of the spinel phase from the layered double oxide (LDO), but did not significantly change the memory effect, by which LDOs can convert to LDHs during the hydration process. For the reversible phase transformation between LDH and LDO, the morphology observation revealed that, in addition to the formation of pores on the surface, nano-slabs were formed, especially for the restored crystals. A layered phase with a dbasal of 5.8 Å, due to bridging bidentate carbonates with the hydrotalcite layer, was formed in the calcination process at low temperature (300 °C) before the formation of LDO, but could not be restored to a large spacing. Typical 5D0 → 7FJ (J = 0–4) transitions of Eu3+ at 579, 593, 615, 653, and 698 nm were observed in the photoluminescence spectra and the intensity of the dominating 615 nm band decreased with the LDH deconstruction and the formation of free water, and then increased with the formation of LDOs in the calcination process, and vice versa in the reconstruction process. The Eu3+ ions had a probable 9- or 10-coordination mode in addition to the probable 8-coordination mode as the spinel phase appeared.
Co-reporter:Yanru Zhang, Hongwei Tan, Jing-xiang Zhao, Xinxin Li, Hui Ma, Xiaoduan Chen and Xiaojing Yang
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 25) pp:9067-9075
Publication Date(Web):23 Apr 2012
DOI:10.1039/C2CP40674H
The intercalation the of 4,4′-oxybis(benzoic acid) anion (OBA2−) into MgAl-layered double hydroxide (LDH) was carried out in formamide, and the structural change of the nanocomposites from homogenous to staging was investigated through in situ XRD, FT-IR, TG-DSC, SEM and molecular dynamics (MD) simulations. In both formamide and water, the nanocomposites had a homogenous structure with a basal spacing of ∼1.7 nm, showing the configuration of OBA2− was vertical to the LDH layers; however, with a decrease in water content after drying, the structure changed to a staging with a basal spacing of 2.62 nm. This resulted from the 1.72 nm phase and another one of 0.85 nm, which was produced by the configuration of OBA2− horizontal to the LDH layers. MD simulations revealed that the LDH layers distorted surrounding OBA2−, and the deformation became more severe with decreasing water content in the interlayer, leading to the staging formation. The simulated XRD pattern confirmed that the staging observed in the experimental pattern was of the Daumas–Hérold type.
Co-reporter:Nankai Chu, Yahong Sun, Yushuang Zhao, Xinxin Li, Genban Sun, Shulan Ma and Xiaojing Yang
Dalton Transactions 2012 vol. 41(Issue 24) pp:7409-7414
Publication Date(Web):24 Apr 2012
DOI:10.1039/C2DT30678F
Two organic sensitisers 4-biphenylcarboxylate (BPC) and terephthalate (TA) were intercalated into the gallery of layered europium hydroxide (LEuH). PL spectra tests indicated that BPC markedly enhanced the red luminescence of Eu3+ due to efficient energy transfer between BPC and Eu3+, forming a contrast to intercalated TA and the starting NO3− anions in the gallery. The energy level matching of the organic guests and Eu3+ was also discussed to explain the energy transfer from sensitiser to Eu3+.
Co-reporter:Sheng Yang, Wenbo Yue, Dazhen Huang, Caifeng Chen, Hao Lin and Xiaojing Yang
RSC Advances 2012 vol. 2(Issue 23) pp:8827-8832
Publication Date(Web):26 Jul 2012
DOI:10.1039/C2RA20746J
This work reports a green and facile approach to the synthesis of graphene nanosheets through the zinc reduction of a graphene oxide precursor in alkaline media. Compared to the chemical reduction of GO by using hydrazine or its derivations, the present route is operationally easy and environmentally friendly. Moreover, the reduction degree of GO in the present condition is much higher than that in either Zn or alkaline solutions alone, indicating a cooperative mechanism, and the as-prepared graphene exhibits a good stability in solution. This simple method shows promising applications in the bulk-quantity production of graphene and graphene-based materials.
Co-reporter:Hongliang Kang;Matteo Leoni;Hongmei He;Gailing Huang
European Journal of Inorganic Chemistry 2012 Volume 2012( Issue 24) pp:3859-3865
Publication Date(Web):
DOI:10.1002/ejic.201200174
Abstract
An LiAl–layered double hydroxide (LiAl–LDH) was synthesized by autoclaving an aqueous solution of LiCl and AlCl3 with urea at 100–160 °C. Chemical and structural analyses show the resulting powder to be pure and well-crystallized LiAl2(OH)6(CO3)0.5·yH2O (1 < y < 2). X-ray powder diffraction reveals an apparent monoclinic C2/m symmetry and the presence of disorder in the arrangement of the layers. A detailed study of the reaction is also proposed, demonstrating that the LiAl–LDH does not form by homogeneous precipitation, but is the result of a one-pot imbibition of the Al(OH)3 gel precursor by Li2CO3, favored by an increase in the pH.
Co-reporter:Zhenzhen Lin, Wenbo Yue, Dazhen Huang, Jiyun Hu, Xiaoying Zhang, Zhong-Yong Yuan and Xiaojing Yang
RSC Advances 2012 vol. 2(Issue 5) pp:1794-1797
Publication Date(Web):22 Dec 2011
DOI:10.1039/C1RA00503K
Porous electrodes commonly exhibit much higher charge–discharge capacities than normal electrodes due to their large surface areas. Some factors such as pore size (pore diameter) and wall thickness also influence the electrochemical behavior of porous electrodes in lithium-ion batteries (e.g. the rate of Li-ion intercalation). Here we investigated how the pore length influenced the charge–discharge capacities by using mesoporous Co3O4 with various particle sizes synthesised via controlling the particle size of SBA-15 templates. The capacity and rate capability of porous Co3O4 were increased with reduction in particle size.
Co-reporter:Shulan Ma, Li Du, Juan Wang, Nankai Chu, Yahong Sun, Genban Sun, Xiaojing Yang and Kenta Ooi
Dalton Transactions 2011 vol. 40(Issue 38) pp:9835-9843
Publication Date(Web):23 Aug 2011
DOI:10.1039/C1DT10982K
The structural control involving staging formation was studied in the nanocomposites of macrocyclic tetraazacrown ether carboxylic acid derivative (TECA) and layered double hydroxide (LDH) obtained by an osmotic swelling/restoration process. After NO3-type MgAl–LDH was osmotically swollen in formamide, TECA was added, leading to a restoration of the LDH sheets and formation of TECA–LDH nanocomposites. In the wet state, the structure of the composites was homogenous, and the basal spacings of ∼2.0 or 1.8 nm were not changed by the water-washing process that removed formamide and caused the replacement of NO3− by CO32−. However, in the drying process, both the orientation of TECA in the interlayer and the formed staging structure varied with the TECA content. The TECA orientation changed from horizontal to tilted/twisted and finally to vertical with interlayer TECA density. The staging structure occurred for samples with both TECA and small inorganic guests coexisting in the interlayer. Third-staging, second-staging, and homogenous structures were observed at TECA/LDH weight ratios of low (0.125 and 0.25), medium (0.5) and large (1 and 2) values, respectively. The decrease of negative charge of TECA ions from −4 to −1 led to the co-existence of small ions (NO3−) with TECA in the gallery and the formation of a NO3−-containing staging structure, even at a high TECA/LDH ratio of 2. The study of the influence of CO32− on the composite structure indicates that a TECA/CO32− ion exchange progressed reversibly and the staging structure formed is thermodynamically stable, depending mainly on the chemical composition of the interlayer guests. The staging formation could be explained by the Daumas–Hérold model, which differs markedly from the Rüdorff model previously proposed for the LDH system. The treatment in formamide of the composite such as T2L+Na2CO3 with staging structure shows that the transformation process is reversible, and these kinds of composites may be used as an adsorbent for some harmful organic solvents.
Co-reporter:Yumei Li, Zhenzhen Lin, Yongliang Li, Caifeng Chen, Yi He, Xiaojing Yang
Materials Research Bulletin 2011 46(12) pp: 2450-2455
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.08.030
Co-reporter:Yumei Li, Yoji Makita, Zhenzhen Lin, Shuangmei Lin, Noriyuki Nagaoka, Xiaojing Yang
Solid State Ionics 2011 Volume 196(Issue 1) pp:34-40
Publication Date(Web):11 August 2011
DOI:10.1016/j.ssi.2011.06.005
By a facile LiNO3 flux method, lithium manganese oxide composites (xLi4Mn5O12∙ yLi2MnO3) were synthesized using a hierarchical organization precursor of manganese dioxide. Li4Mn5O12 and Li2MnO3 have spinel and rocksalt structures, respectively. The lithiation and structural transformation from the precursor to the composites occurred topotactically from exterior toward interior in the precursor particle with the increase of reaction time, and the composites had core-shell spinel@rocksalt structures in addition to the original hierarchical core-shell organization. The electrochemical measurements at 50 °C after 50 cycles confirmed that a typical spinel@rocksalt cathode had higher capacity retention (87.1%) than that with the composition close to the stoichiometric spinel (64.6%), indicating the Li2MnO3 shell can improve cycling stability for the composite electrode at elevated temperature.Highlights► Lithium manganates are prepared by a LiNO3 flux method. ► Manganate composites have core-shell structures. ► Spinel@rocksalt composite shows improved capacity retention at 50 °C. ► Li2MnO3 on the surface of Li4Mn5O12 may reduce dissolution of Mn during cycling.
Co-reporter:Gailing Huang, Shulan Ma, Xinhua Zhao, Xiaojing Yang and Kenta Ooi
Chemistry of Materials 2010 Volume 22(Issue 5) pp:1870
Publication Date(Web):January 11, 2010
DOI:10.1021/cm903405s
Water-soluble tetrasodium p-sulfonatothiacalix[4]arene (TCAS) was intercalated into MgAl-LDH using an osmotic swelling/restoration reaction of the LDH in formamide. The restoration process was investigated in detail. The arrangement of TCAS in the interlayer can be controlled through adjusting the area per unit charge (Scharge) of TCAS. When Scharge (TCAS) < Scharge (LDH), monolayer (basal spacing, dbasal, 1.30 nm) and alternating “up-down” antiparallel (dbasal, 1.54 and 1.45 nm) arrangements were obtained. When Scharge of TCAS was increased by forming an Ag+ complex, bilayer arrangement (dbasal, 2.12 nm) of TCAS(Ag) was formed. This swelling/restoration reaction took place, and the composites retained the morphology of the LDH precursor. The thermal stability of TCAS in the composites was remarkably enhanced, and the “up-down” antiparallel arrangement of TCAS had the highest increase of thermal stability.
Co-reporter:Hongmei He, Hongliang Kang, Shulan Ma, Yongxiang Bai, Xiaojing Yang
Journal of Colloid and Interface Science 2010 Volume 343(Issue 1) pp:225-231
Publication Date(Web):1 March 2010
DOI:10.1016/j.jcis.2009.11.004
The selective adsorption of phosphate ions was investigated on CO32-, Cl−, and NO3--type ZnAl layered double hydroxides (LDHs) and the calcined CO32--type LDH at 200, 400, 600 and 800 °C, respectively. The calcined LDHs and NO3--type LDH showed high selectivity toward phosphate ions, while the Cl−-type LDH shows selectivity toward both SO42- and phosphate ions. The NO3--type LDH selectively adsorbed phosphate ions mainly through ion exchange. The calcined samples possibly proceed through ligand complexation or electrostatic attraction between phosphate ions and hydrated ZnO formed after calcination, although the structural memory effect was observed for the samples calcined below 600 °C with the formation of CO32--type LDH. Adsorption/desorption behaviors indicated that the calcined samples had good stability and reusability.A high selectivity toward phosphate and reusability were exhibited by the calcined ZnAl–CO3 LDHs at different temperatures.
Co-reporter:Shulan Ma;Cuihong Fan;Gailing Huang;Yumei Li;Kenta Ooi
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 14) pp:2079-2083
Publication Date(Web):
DOI:10.1002/ejic.201000010
Abstract
A carbonate shortage phenomenon (CO32–/Al < 0.5) was found in MgAl layered double hydroxides (LDHs) withMg/Al < 2 synthesized by the homogeneous precipitation (urea hydrolysis) method. To explain the phenomenon, a “gibbsite-layer based substitution–filling” model containing octahedral vacancies with formula [Mgy□0.5–y][MgxAl1–x](OH)3(CO32–)y–x/2·mH2O is proposed on the basis of the detailed composition analysis and ordered distribution of Mg and Al in the layer.
Co-reporter:Shulan Ma, Cuihong Fan, Li Du, Gailing Huang, Xiaojing Yang, Weiping Tang, Yoji Makita and Kenta Ooi
Chemistry of Materials 2009 Volume 21(Issue 15) pp:3602
Publication Date(Web):July 7, 2009
DOI:10.1021/cm9007393
A carboxyethyl substituted azacrown ether derivative (CSAE) was intercalated as a second host into a parent host of well-crystallized crystal of Mg−Al layered double hydroxide (MgAl-LDH) by a CSAE/NO3− ion-exchange reaction. The influence of intercalation temperature on the structures and compositions of CSAE−LDH nanocomposites was investigated. The composites obtained at the temperatures below 70 °C had almost the same CASE contents and layered structures with a basal spacing of about 1.6 nm, corresponding to the vertical orientation of CSAE plane to the LDH layer. The chemical analysis showed that a considerable amount of CO32− (with CO32−/CSAE molar ratio of 1.4) was incorporated in the interlayer of LDH. The CSAE content decreased while CO32− content increased with an increase of the intercalation temperature in the region above 70 °C. At 100 °C, a second staging phase of 2.33 nm appeared, attributed to the ordered stacking of the 1.6 nm phase and a 0.77 nm phase produced by the CO32−/CSAE exchange. At higher temperatures, a new phase with a basal spacing of 1.18 nm appeared, which corresponds to the tilt/twisted orientation of CSAE anions in the interlayer. The other second staging phase of 2.08 nm appeared obviously at 150 °C, due to the regular stacking of the 1.18 and 0.77 nm phases. The adsorptive properties for transition metal ions were studied using the 70 and 150 °C reacted composites. The 70 °C reacted one showed higher adsorptivity toward transition metal ions; the adsorptive capacity increased in the sequence of Cu2+ > Ni2+ > Co2+ > Zn2+, and distribution coefficient for Cu2+ was markedly higher than those for the other ions. However, the 150 °C reacted one showed little adsorptivity toward these ions. The adsorption for transition metal ions was accompanied by the intercalation of nearly equivalent amount of nitrate ions. This shows that the interlayer CSAE ions in the 1.6 nm phase act as a second host, but those in the 1.18 nm phase do not.
Co-reporter:Gailing Huang, Shulan Ma, Xinhua Zhao, Xiaojing Yang and Kenta Ooi
Chemical Communications 2009 (Issue 3) pp:331-333
Publication Date(Web):25 Nov 2008
DOI:10.1039/B816996A
Utilizing the osmotic swelling of LDH in formamide, for the first time, the bulky thiacalix[4]arene anion is introduced, leading to the recovery of LDH layers, and the hexagonal prism morphology of the precursor is well retained.
Co-reporter:Yufeng Chen, Xinhua Zhao, Hui Ma, Shulan Ma, Gailing Huang, Yoji Makita, Xuedong Bai, Xiaojing Yang
Journal of Solid State Chemistry 2008 Volume 181(Issue 7) pp:1684-1694
Publication Date(Web):July 2008
DOI:10.1016/j.jssc.2008.06.014
The crystals of an H-form niobate of HCa2Nb3O10·xH2O (x=0.5) being tetragonal symmetry (space group P4/mbm) with unit cell parameters a=5.4521(6) and c=14.414(2) Å were exfoliated into nanosheets with the triple-layered perovskite structure. The colloid suspension of the nanosheets was put into dialysis membrane tubing and allowed self-assembly in a dilute KCl solution. By this method, a novel layered K-form niobate KCa2Nb3O10·xH2O (x=1.3, typically) with bilayer hydrates in the interlayer was produced. The Rieveld refinement and transmission electron microscope (TEM)/selected-area electron diffraction (SAED) observation indicated that the orientations of the a-/b-axis of each nanosheet as well as the c-axis are uniform, and the self-assembled compound had the same symmetry, tetragonal (P4/mbm) with a=5.453(2) and c=16.876(5) Å, as the H-form precursor; the exfoliation/self-assembly process does not markedly affect the two-dimensional lattice of the layer. The large basal spacing resulted from the interlayer K+ ions solvated by two layers of water molecules. The interlayer bilayers-water was gradually changed to monolayer when the temperatures higher than 100 °C, and all the water molecules lost when over 600 °C. Accompanying the dehydration, the crystal structure transformed from tetragonal to orthorhombic symmetry. Water molecules may take an important role for the layer layered compound to adjust the unit cell to tetragonal symmetry.The structure of layered perovskite niobate KCa2Nb3O10·xH2O (x =1.3) having a bilayers-hydrates interlayer, obtained via the exfoliation of an H-form precursor and the self-assembly of Ca2Nb3O10- nanosheets, was first discussed in detail and determined to be tetragonal symmetry (P4/mbm). The dehydration resulted in the structural transformation to orthorhombic structure.
Co-reporter:Gailing Huang, Shulan Ma, Xinhua Zhao, Xiaojing Yang and Kenta Ooi
Chemical Communications 2009(Issue 3) pp:NaN333-333
Publication Date(Web):2008/11/25
DOI:10.1039/B816996A
Utilizing the osmotic swelling of LDH in formamide, for the first time, the bulky thiacalix[4]arene anion is introduced, leading to the recovery of LDH layers, and the hexagonal prism morphology of the precursor is well retained.
Co-reporter:Yanru Zhang, Hongwei Tan, Jing-xiang Zhao, Xinxin Li, Hui Ma, Xiaoduan Chen and Xiaojing Yang
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 25) pp:NaN9075-9075
Publication Date(Web):2012/04/23
DOI:10.1039/C2CP40674H
The intercalation the of 4,4′-oxybis(benzoic acid) anion (OBA2−) into MgAl-layered double hydroxide (LDH) was carried out in formamide, and the structural change of the nanocomposites from homogenous to staging was investigated through in situ XRD, FT-IR, TG-DSC, SEM and molecular dynamics (MD) simulations. In both formamide and water, the nanocomposites had a homogenous structure with a basal spacing of ∼1.7 nm, showing the configuration of OBA2− was vertical to the LDH layers; however, with a decrease in water content after drying, the structure changed to a staging with a basal spacing of 2.62 nm. This resulted from the 1.72 nm phase and another one of 0.85 nm, which was produced by the configuration of OBA2− horizontal to the LDH layers. MD simulations revealed that the LDH layers distorted surrounding OBA2−, and the deformation became more severe with decreasing water content in the interlayer, leading to the staging formation. The simulated XRD pattern confirmed that the staging observed in the experimental pattern was of the Daumas–Hérold type.
Co-reporter:Yushuang Zhao, Ji-Guang Li, Fang Fang, Nankai Chu, Hui Ma and Xiaojing Yang
Dalton Transactions 2012 - vol. 41(Issue 39) pp:NaN12184-12184
Publication Date(Web):2012/08/13
DOI:10.1039/C2DT31249B
Highly crystalline Eu3+-incorporated MgAl layered double hydroxides (LDHs) were synthesized by the homogeneous precipitation method. For the crystals as-prepared, after their calcination from 200–1000 °C, and, further, after restoration in a Na2CO3 solution, the structural and luminescent changes were investigated for the first time. Eu3+ ions with a coordination number of, probably, 8, were incorporated into the hydrotalcite layer, which led to a basal spacing (dbasal) increase, microstrain formation, and crystalline morphology imperfections, while retaining the original lattice symmetry, Rm. In the deconstruction process due to calcination, the Eu3+ ions restrained the formation of the spinel phase from the layered double oxide (LDO), but did not significantly change the memory effect, by which LDOs can convert to LDHs during the hydration process. For the reversible phase transformation between LDH and LDO, the morphology observation revealed that, in addition to the formation of pores on the surface, nano-slabs were formed, especially for the restored crystals. A layered phase with a dbasal of 5.8 Å, due to bridging bidentate carbonates with the hydrotalcite layer, was formed in the calcination process at low temperature (300 °C) before the formation of LDO, but could not be restored to a large spacing. Typical 5D0 → 7FJ (J = 0–4) transitions of Eu3+ at 579, 593, 615, 653, and 698 nm were observed in the photoluminescence spectra and the intensity of the dominating 615 nm band decreased with the LDH deconstruction and the formation of free water, and then increased with the formation of LDOs in the calcination process, and vice versa in the reconstruction process. The Eu3+ ions had a probable 9- or 10-coordination mode in addition to the probable 8-coordination mode as the spinel phase appeared.
Co-reporter:Wenbo Yue, Zhenzhen Lin, Shuhua Jiang and Xiaojing Yang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 32) pp:NaN16323-16323
Publication Date(Web):2012/06/22
DOI:10.1039/C2JM30805C
Graphene-encapsulated mesoporous metal oxides (e.g. Co3O4, Cr2O3 and NiO) as novel anode materials for lithium-ion batteries were simply synthesized by adjusting the pH of mesoporous metal oxides and graphene oxide suspensions to set values (e.g. 5–6 for metal oxides, 7–8 for graphene oxide) and mixing the two suspensions in the presence of reducing agents. These composites synthesized by this facile method exhibited superior electrochemical performance, including remarkably high capacity, high rate capability and excellent cycle performance. The improved performance may be attributed to the high dispersion of mesoporous particles separated by graphene nanosheets and the high electrical conductivity of graphene.
Co-reporter:Tingting Chen, Fang Deng, Jia Zhu, Caifeng Chen, Genban Sun, Shulan Ma and Xiaojing Yang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 30) pp:NaN15197-15197
Publication Date(Web):2012/06/13
DOI:10.1039/C2JM31171B
Hexagonal close-packed Ni (h-Ni) nanocrystals and face-centered cubic Ni (c-Ni) nanoflowers with uniform size and high dispersion have been successfully assembled on graphene nanosheets (GN) via a facile one-step solution-phase strategy under different reaction conditions, where the reduction process of graphite oxide (GO) sheets into GN was accompanied by the generation of Ni nanocrystals. The reduction of GO by this method is effective, which was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy and is comparable to conventional methods. The phase and morphology of nickel can be easily tuned by varying the reaction temperature and solvent. It was shown that the as-formed h-Ni nanocrystals with a diameter as small as 3 nm are grown densely and uniformly on the graphene sheets, and as a result the aggregation of the h-Ni nanocrystals was effectively prevented. In addition, c-Ni nanospheres assembled by c-Ni nanocrystals with a size of 15 nm were also uniformly deposited on the graphene sheets. The investigation of the microwave absorbability reveals that the three Ni/GN nanocomposites exhibit excellent microwave absorbability, which is stronger than the corresponding Ni nanostructures.
Co-reporter:Shulan Ma, Li Du, Juan Wang, Nankai Chu, Yahong Sun, Genban Sun, Xiaojing Yang and Kenta Ooi
Dalton Transactions 2011 - vol. 40(Issue 38) pp:NaN9843-9843
Publication Date(Web):2011/08/23
DOI:10.1039/C1DT10982K
The structural control involving staging formation was studied in the nanocomposites of macrocyclic tetraazacrown ether carboxylic acid derivative (TECA) and layered double hydroxide (LDH) obtained by an osmotic swelling/restoration process. After NO3-type MgAl–LDH was osmotically swollen in formamide, TECA was added, leading to a restoration of the LDH sheets and formation of TECA–LDH nanocomposites. In the wet state, the structure of the composites was homogenous, and the basal spacings of ∼2.0 or 1.8 nm were not changed by the water-washing process that removed formamide and caused the replacement of NO3− by CO32−. However, in the drying process, both the orientation of TECA in the interlayer and the formed staging structure varied with the TECA content. The TECA orientation changed from horizontal to tilted/twisted and finally to vertical with interlayer TECA density. The staging structure occurred for samples with both TECA and small inorganic guests coexisting in the interlayer. Third-staging, second-staging, and homogenous structures were observed at TECA/LDH weight ratios of low (0.125 and 0.25), medium (0.5) and large (1 and 2) values, respectively. The decrease of negative charge of TECA ions from −4 to −1 led to the co-existence of small ions (NO3−) with TECA in the gallery and the formation of a NO3−-containing staging structure, even at a high TECA/LDH ratio of 2. The study of the influence of CO32− on the composite structure indicates that a TECA/CO32− ion exchange progressed reversibly and the staging structure formed is thermodynamically stable, depending mainly on the chemical composition of the interlayer guests. The staging formation could be explained by the Daumas–Hérold model, which differs markedly from the Rüdorff model previously proposed for the LDH system. The treatment in formamide of the composite such as T2L+Na2CO3 with staging structure shows that the transformation process is reversible, and these kinds of composites may be used as an adsorbent for some harmful organic solvents.
Co-reporter:Nankai Chu, Yahong Sun, Yushuang Zhao, Xinxin Li, Genban Sun, Shulan Ma and Xiaojing Yang
Dalton Transactions 2012 - vol. 41(Issue 24) pp:NaN7414-7414
Publication Date(Web):2012/04/24
DOI:10.1039/C2DT30678F
Two organic sensitisers 4-biphenylcarboxylate (BPC) and terephthalate (TA) were intercalated into the gallery of layered europium hydroxide (LEuH). PL spectra tests indicated that BPC markedly enhanced the red luminescence of Eu3+ due to efficient energy transfer between BPC and Eu3+, forming a contrast to intercalated TA and the starting NO3− anions in the gallery. The energy level matching of the organic guests and Eu3+ was also discussed to explain the energy transfer from sensitiser to Eu3+.
Co-reporter:Hong Wu, Huifeng Li, Genban Sun, Shulan Ma and Xiaojing Yang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 21) pp:NaN5466-5466
Publication Date(Web):2015/04/27
DOI:10.1039/C5TC00778J
Face-centered cubic α-LiFeO2 and spinel β-LiFe5O8 with uniform size and high dispersion have been successfully assembled on 2D graphene sheets via a facile one-pot strategy under different reaction conditions. The reduction of GO by this method is effective and comparable to conventional methods, which was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The structure of the products can be easily controlled by changing the solvent and reaction temperature. It was shown that the as-formed β-LiFe5O8 and α-LiFeO2 nanocrystals with a diameter of ca. 5 nm and 7 nm, respectively, were densely and uniformly anchored on the graphene sheets, and as a result, the aggregation of the nanoparticles was effectively prevented. The investigation of the microwave absorbability reveals that the α-LiFeO2–GN and β-LiFe5O8–GN nanocomposites exhibit excellent microwave absorbability, which is stronger than that of the corresponding α-LiFeO2 and β-LiFe5O8 nanostructures, respectively.
Co-reporter:Yushuang Zhao, Ji-Guang Li, Mengxi Guo and Xiaojing Yang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 22) pp:NaN3592-3592
Publication Date(Web):2013/04/11
DOI:10.1039/C3TC30205A
Rare-earth phosphors with tunable optical properties are used in display panels and fluorescent lamps and have potential applications in lasers and bioimaging. This work reported the preparation, structure and photoluminescence of the unilamellar nanosheets containing Tb3+/Eu3+ delaminated from layered rare-earth hydroxides (LRHs). Highly crystallized LTbH and LEuH with monolayered dodecyl sulfate ions vertical to the layer were synthesized by a one-step homogeneous precipitation method for the first time, and were shown to be readily delaminated in formamide. The obtained unilamellar nanosheets exhibited a decrease of the coordination number of the lanthanide ions, to probably 8-fold, when compared with the bulky precursor crystals. This change resulted in different photoluminescence emission peak shapes. Colloidal hybrids were constructed using these nanosheets as building blocks, and the emission colors of the hybrids can be facilely and precisely tuned from green to yellow, orange, and finally to red by controlling the relative contents of the two kinds of nanosheets. This method provides a novel and simple route to prepare color-tunable hybrid materials from 2-dimensional crystals.
