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Junhua Kong,
Yuefan Wei,
Liping Yang,
Wu Aik Yee,
Yuliang Dong,
Rui Zhou,
Siew Yee Wong,
Lin Ke,
Xiao Wei Sun,
Hejun Du,
Xu Li, Xuehong Lu
The Journal of Physical Chemistry C 04/2013; 117(19):10106-10113. · 4.80 Impact Factor
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Junhua Kong,
Wu Aik Yee,
Yuefan Wei,
Liping Yang,
Jia Ming Ang,
Si Lei Phua,
Siew Yee Wong,
Rui Zhou,
Yuliang Dong,
Xu Li, Xuehong Lu
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ABSTRACT: Silicon (Si) is a promising material for lithium ion battery (LIB) anodes due to its high specific capacity. To overcome its shortcomings such as insulation property and large volume change during the charge-discharge process, a novel hybrid system, Si nanoparticles encapsulated in hollow graphitized carbon nanofibers, is studied. First, electrospun polyacrylonitrile (PAN)-Si hybrid nanofibers were obtained using water as the collector. The loose nanofiber lumps suspended in water have large inter-fiber distance, allowing in situ coating of a thin layer of polydopamine (PDA), the source for graphitized carbon, uniformly throughout the system. The designed morphology and structure were then realized by etching and calcination, and the morphology and structure were subsequently verified by various analytical techniques. Electrochemical measurements show that the resulting hollow hybrid nanofibers (C-PDA-Si NFs) exhibit much better cycling stability and rate capacity than conventional C/Si nanofibers derived by electrospinning of PAN-Si followed by calcination. For instance, the capacity of C-PDA-Si NFs is as high as 72.6% of the theoretical capacity after 50 cycles, and a high capacity of 500 mA h g-1 can be delivered at a current density of 5 A g-1. The significantly improved electrochemical properties of C-PDA-Si NFs are due to the excellent electrical conductivity of the carbonized PDA (C-PDA) shell that compensates for the insulation property of Si, the high electrochemical activity of C-PDA, which has a layered structure and is N-doped, the hollow nature of the nanofibers and small size of Si nanoparticles that ensure smooth insertion-extraction of lithium ions and more complete alloying with them, as well as the buffering effect of the remaining PAN-derived carbon around the Si nanoparticles, which stabilizes the structure.
Nanoscale 03/2013; · 5.91 Impact Factor
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Journal of Materials Chemistry 02/2013; · 5.97 Impact Factor
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Junhua Kong,
Wu Aik Yee,
Yuefan Wei,
Liping Yang,
Jia Ming Ang,
Silei Phua,
Siew Yee Wong,
Rui Zhou,
Yuliang Dong, Xuehong Lu,
Xu Li
Nanoscale 02/2013; · 5.91 Impact Factor
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ABSTRACT: Inspired by the radical scavenging function of melanin-like materials and versatile adhesive ability of mussel-adhesion proteins, dopamine-modified clay (D-clay) was successfully incorporated into polypropylene (PP) using an amine-terminated PP oligomer as the compatibilizer. Although the PP/D-clay nanocomposites exhibit intercalated morphology, the incorporation of D-clay greatly improves the thermo-oxidative stability and UV resistance of PP owing to the strong radical scavenging ability of polydopamine (PDA) and large contact area between PP and the PDA coating on clay mineral. Moreover, the reinforcement effect brought by D-clay is fairly significant at very low clay loadings probably owing to the strong interfacial interactions between the layered silicates and the compatibilizer as well as that between the compatibilizer and the PP matrix. The work demonstrates that D-clay is a type of promising nanofiller for thermoplastics used for outdoor applications since it stabilizes and reinforces the polymers simultaneously.
ACS Applied Materials & Interfaces 01/2013; · 4.53 Impact Factor
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ABSTRACT: Clay-based functional hydrogels were facilely prepared via a bio-inspired approach. Montmorillonite (clay) was exfoliated into single layers in water, and then coated with a thin layer of polydopamine (PDOPA) via in situ polymerization of dopamine under basic aqueous condition. When a small amount of ferric salt was added into aqueous suspensions of the polydopamine-coated clay (D-clay), D-clay and Fe3+ ions could rapidly self assemble into three-dimensional networks through the formation of coordination bonds. Consequently, supramolecular hydrogels were formed at very low D-clay contents. Rheological measurements show that the D-clay/Fe3+ hydrogels exhibit fairly elastic response in low stain range, and have self-healing capability upon removal of applied large stress. More importantly, the hydrogels can be used as adsorbents to effectively remove Rhodamine 6G (Rh6G), a organic pollutant, from water. UV-Vis absorption spectra of the Rh6G-loaded hydrogels show bands related to π-π stacking interactions between the aromatic moieties of PDOPA and Rh6G, confirming the formation of PDOPA/Rh6G complex on the surface of D-clay.
Langmuir 01/2013; · 4.19 Impact Factor
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ABSTRACT: Azulene-containing conjugated polymers with near-infrared absorption up to 1.5 μm and beyond are achieved by treating with trifluoroacetic acid (TFA). Density functional theory calculations reveal that the near-infrared absorption arises from a strong intramolecular charge transfer transition on the polymer backbone, and the near-infrared absorption can be tuned by the degree of protonation. Furthermore, TFA treated polymers show a ten-fold enhancement in electrochromic contrast and significantly improved switching stability, suggesting that these polymers are promising candidates for fabrication of the first generation organic near-infrared devices.
Macromolecular Rapid Communications 12/2012; · 4.60 Impact Factor
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ABSTRACT: In this work, monodisperse polydopamine (PDA) spheres with tunable diameters have been synthesized through a facile and low cost method using a deionized water and alcohol mixed solvent. The PDA spheres possess surface functional groups (-OH, -NH(2) ), exhibiting an extraordinary versatile active nature. It is demonstrated that the PDA spheres could serve as an active template for the convenient synthesis of various nanostructures, e.g., MnO(2) hollow spheres or PDA/Fe(3) O(4) and PDA/Ag core/shell nanostructures. No surface modification or special treatment is required for the synthesis of these nanostructures, which makes the fabrication process simple and very convenient. The novel application of PDA/Fe(3) O(4) spheres as fillers in nanocomposites for high-performance capacitors is demonstrated, indicating a promising practicality. The PDA spheres provide a new general platform not only for the facile assembly of nanostructures but also a green synthetic template for practical applications.
Small 11/2012; · 8.35 Impact Factor
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ABSTRACT: Thin carbonized polydopamine (C-PDA) coatings are found to have similar structures and electrical conductivities to those of multilayered graphene doped with heteroatoms. Greatly enhanced electrochemical properties are achieved with C-PDA-coated SnO(2) nanoparticles where the coating functions as a mechanical buffer layer and conducting bridge.
Chemical Communications 09/2012; 48(83):10316-8. · 6.17 Impact Factor
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ABSTRACT: Dopamine-modified clay (D-clay) was successfully dispersed into polyether polyurethane (PU) by solvent blending. It is found that the incorporation of D-clay into PU gives rise to significant improvements in mechanical properties, including initial modulus, tensile strength, and ultimate elongation, at a very low clay loading. The large reinforcement could be attributed to the hydrogen bonds between the hard segments of PU and stiff D-clay layers that lead to more effective interfacial stress transfer between the polymer and D-clay. Besides, the interactions between D-clay and PU are also stronger than those between Cloisite 30B organoclay and the PU chains. Consequently, at a similar clay loading, the PU/D-clay nanocomposite has much higher storage modulus than the PU/organoclay nanocomposite at elevated temperatures.
ACS Applied Materials & Interfaces 08/2012; 4(9):4571-8. · 4.53 Impact Factor
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ABSTRACT: Electrochromic (EC) materials and polymer electrolytes are the most important components in an electrochromic device (ECD). On page 4071, X. Lu, J. Ma, P. S. Lee, and co-workers review the recent advancements on nanostructured inorganic and conjugated polymer-based organic-inorganic hybrid EC materials. The review also highlights the progress on polymer electrolytes for electrochromic devices as platforms for practical applications.
Advanced Materials 08/2012; 24(30):4070. · 13.88 Impact Factor
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ABSTRACT: Polydopamine-coated graphene oxide (DGO) films exhibit electrical conductivities of 11000 S m-1 and 30000 S m-1 upon vacuum annealing at 130 ºC and 180 ºC, respectively. Conductive poly(vinyl alcohol)/graphene and epoxy/graphene nanocomposites show low percolation thresholds due to the excellent dispersibility of the DGO sheets and their effective in situ reduction.
Nanoscale 06/2012; · 5.91 Impact Factor
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ABSTRACT: Electrochromic (EC) materials and polymer electrolytes are the most imperative and active components in an electrochromic device (ECD). EC materials are able to reversibly change their light absorption properties in a certain wavelength range via redox reactions stimulated by low direct current (dc) potentials of the order of a fraction of volts to a few volts. The redox switching may result in a change in color of the EC materials owing to the generation of new or changes in absorption band in visible region, infrared or even microwave region. In ECDs the electrochromic layers need to be incorporated with supportive components such as electrical contacts and ion conducting electrolytes. The electrolytes play an indispensable role as the prime ionic conduction medium between the electrodes of the EC materials. The expected applications of the electrochromism in numerous fields such as reflective-type display and smart windows/mirrors make these materials of prime importance. In this article we have reviewed several examples from our research work as well as from other researchers' work, describing the recent advancements on the materials that exhibit visible electrochromism and polymer electrolytes for electrochromic devices. The first part of the review is centered on nanostructured inorganic and conjugated polymer-based organic-inorganic hybrid EC materials. The emphasis has been to correlate the structures, morphologies and interfacial interactions of the EC materials to their electronic and ionic properties that influence the EC properties with unique advantages. The second part illustrates the perspectives of polymer electrolytes in electrochromic applications with emphasis on poly (ethylene oxide) (PEO), poly (methyl methacrylate) (PMMA) and polyvinylidene difluoride (PVDF) based polymer electrolytes. The requirements and approaches to optimize the formulation of electrolytes for feasible electrochromic devices have been delineated.
Advanced Materials 05/2012; 24(30):4071-96. · 13.88 Impact Factor
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ABSTRACT: This article reports the synthesis and characterization of a quantum-confined luminescent dot with size 2–3nm using well-defined
m-octa(bromophenyl) silsesquioxane (m-OBPS) as core. The highly regioselective bromination of octaphenylsilsesquioxane (OPS), which is an electron-deficient nanometer-sized
molecule, has been synthesized using combined catalyst of iodine and zinc chloride at room temperature in dichloromethane
solvent. Based on m-OBPS, a hybrid luminescent dot with well-defined structure was synthesized. UV absorption and PL spectra of this light-emitting
dot remain same in dilute solution, condensed state, and solid solution. Furthermore, time-resolved PL study indicates that
the exciton decay time of the light-emitting dot remains similar regardless in dilute solution, condensed state, or blended
with other polymers, suggesting that the charge carriers are well confined within the individual light-emitting dot due to
the unique star-like structure and shielding alkyl chain layer. The light-emitting nano-particles can be considered as isolated
chromophores as both inter- and intra- molecular aggregation are prohibited.
KeywordsPOSS-Luminescent-Regioselective-Hybrid-Nanoparticle-Quantum dots-Solar cells
Journal of Nanoparticle Research 04/2012; 12(8):2787-2798. · 3.29 Impact Factor
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ABSTRACT: Highly conductive graphene sheets were prepared by coating graphene oxide with polydopamine (PDA) followed by reduction with hydrazine. Polyacrylonitrile/graphene nanocomposites prepared via solution blending exhibit high electrical conductivities at very low graphene loadings owing to the good exfoliation and relatively planar conformation of the PDA-coated graphene in the polymer matrix.
RSC Advances. 01/2012; 2(6):2208-2210.
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ABSTRACT: In this work, the effects of single-walled carbon nanotubes (SWCNT) surface chemistry on the polymorphism behaviors of electrospun poly(vinylidene difluoride) (PVDF) nanofibers collected under high extensional force and subsequently treated with supercritical carbon dioxide (SCCO2) are investigated via X-ray diffraction, infrared and Raman spectroscopy. It is found that the SWCNTs with hydroxyl groups (h-SWCNTs) interact with PVDF chains more intensively than the ones with ester groups, and the interaction in couple with the high extensional force promotes the formation of β-form extended-chain crystallites (ECCs). With the SCCO2 treatment, the growth of the β-form ECCs is further promoted in the PVDF/h-SWCNT nanofibers owing to the synergistic effect of the strong confinement effect of h-SWCNT for stabilizing the nuclei of the β-form ECCs and the high pressure applied.
Polymer 01/2012; 53(22):5097. · 3.44 Impact Factor
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ABSTRACT: A carbon/SnO(2)/carbon core/shell/shell hybrid nanofibrous mat was successfully prepared via single-spinneret electrospinning followed by carbonization and hydrothermal treatment. The morphology and structure of carbon/SnO(2)/carbon hybrid nanofibers were characterized by field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, wide-angle X-ray diffraction and X-ray photoelectron spectroscopy, and their electrochemical properties were studied as an anode in lithium ion batteries (LIBs). It is shown that the designed hybrid nanofibrous mat exhibits excellent electrochemical properties, including high reversible capacity with high columbic efficiency and impressive rate capacity. The greatly enhanced electrochemical performance is mainly due to the morphological stability and reduced diffusion resistance, which are induced by both the carbon core and deposited carbon skin. Furthermore, the embedded and de-aggregated SnO(2) nanoparticles in the carbon phase, which are less than 10 nm in size, provide large numbers of reaction sites for lithium ions and ensure complete alloying with them.
Nanoscale 11/2011; 4(2):525-30. · 5.91 Impact Factor
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ABSTRACT: A facile biomimetic method was developed to enhance the interfacial interaction in polymer-layered silicate nanocomposites. By mimicking mussel adhesive proteins, a monolayer of polydopamine was constructed on clay surface by a controllable coating method. The modified clay (D-clay) was incorporated into an epoxy resin, it is found that the strong interfacial interactions brought by the polydopamine benefits not only the dispersion of the D-clay in the epoxy but also the effective interfacial stress transfer, leading to greatly improved thermomechanical properties at very low inorganic loadings. Rheological and infrared spectroscopic studies show that the interfacial interactions between the D-clay and epoxy are dominated by the hydrogen bonds between the catechol-enriched polydopamine and the epoxy.
ACS Applied Materials & Interfaces 07/2011; 3(8):3026-32. · 4.53 Impact Factor
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ABSTRACT: Solid polymer electrolytes with excellent ionic conductivity (above 10(-4) S cm(-1)), which result in high optical modulation for solid electrochromic (EC) devices are presented. The combination of a polar host matrix poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and a solid plasticized of a low molecular weight poly(ethylene oxide) (PEO) (M(w)≤ 20,000) blended polymer electrolyte serves to enhance both the dissolution of lithium salt and the ionic transport. Calorimetric measurement shows a reduced crystallization due to a better intermixing of the polymers with small molecular weight PEO. Vibrational spectroscopy identifies the presence of free ions and ion pairs in the electrolytes with PEO of M(w)≤ 8000. The ionic dissolution is improved using PEO as a plasticizer when compared to liquid propylene carbonate, evidently shown in the transference number analysis. Ionic transport follows the Arrhenius equation with a low activation energy (0.16-0.2 eV), leading to high ionic conductivities. Solid electrochromic devices fabricated with the blended P(VDF-TrFE)/PEO electrolytes and polyaniline show good spectroelectrochemical performance in the visible (300-800 nm) and near-infrared (0.9-2.4 μm) regions with a modulation up to 60% and fast switching speed of below 20 seconds. The successful introduction of the solid polymer electrolytes with its best harnessed qualities helps to expedite the application of various electrochemical devices.
Physical Chemistry Chemical Physics 06/2011; 13(29):13319-26. · 3.57 Impact Factor
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ABSTRACT: The electrodes with the hierarchical nanoarchitectures could offer a huge increase in energy storage capacity. However, the ability to achieve such hierarchical architectures on a multiple scale still has remained a great challenge. In this paper, we report a scalable self-assembly strategy to create bioinspired hierarchical structures composed of functionalized graphene sheets to work as anodes of lithium-ion batteries. The resulting electrodes with novel multilevel architectures simultaneously optimize ion transport and capacity, leading to a high performance of reversible capacity of up to 1600 mAh/g, and 1150 mAh/g after 50 cycles. Importantly, the process to fabricate such hierarchical structures is facile, low-cost, green, and scalable, providing a universal approach for the rational design and engineering of electrode materials with enhanced performance, and it may have utility in various applications, including biological scaffold, catalysis, and sensors.
ACS Nano 05/2011; 5(5):3831-8. · 10.77 Impact Factor
