In JoVE (1)

Other Publications (8)

Articles by Kaixi Wang in JoVE

 JoVE Bioengineering

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

1Department of Biomedical Engineering, Washington University in St. Louis, 2Department of Biology, Washington University in St. Louis, 3Department of Orthopaedic Surgery, Washington University in St. Louis, 4Department of Materials Science and Mechanical Engineering, Washington University in St. Louis

JoVE 55437

Other articles by Kaixi Wang on PubMed

The Complete Mitochondrial Genome of Channa Maculata (Perciformes: Channidae)

Mitochondrial DNA. Aug, 2013  |  Pubmed ID: 23379357

This paper reports the complete mitochondrial genome (mitogenome) sequence of Channa maculate (Taiwan snakehead). The mitogenome of Taiwan snakehead was determined to be 16,558 bp in length. It contains 13 typical vertebrate protein-coding genes, 22 tRNA genes, 2 rRNA genes, 1 OL (putative light-strand origin of replication), and 1 putative control region (D-loop). This is the first report on the complete mitogenome sequence of Channa maculata.

Controlled Fabrication of PANI/CNF Hybrid Films: Molecular Interaction Induced Various Micromorphologies and Electrochemical Properties

Journal of Colloid and Interface Science. Dec, 2013  |  Pubmed ID: 24041549

In this paper, a facile and efficient method is reported to prepare polyaniline/carbon nanofiber (PANI/CNF) hybrid films by in situ chemical polymerization of aniline. The various morphologies and microstructures of PANI/CNF hybrid films can be controlled by adjusting the concentration of aniline and different acids as the protonation reagent, and the formation mechanism is illustrated in this study. The surface morphologies and chemical structure of the PANI/CNF hybrid films are characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), water contact angle (CA), FT-IR, Raman, and UV-vis spectrophotometers. The different morphology of uniformly coated, twist-tangled, and needle-like PANI built on CNF films are obtained by using HCl, H2SO4, and HClO4 as protonation reagent and the obtained hybrid films are labeled as PANI/CNF-f1, PANI/CNF-f2, and PANI/CNF-f3, respectively. We demonstrated that the different protonation reagent has the determined effect on the surface properties of the obtained hybrid films that can transfer from hydrophilic to hydrophobic. Besides, the various morphologies of PANI play an important role in their electrochemical properties. PANI/CNF-f3 exhibits higher specific capacitance and better stability than that of the PANI/CNF-f1 and PANI/CNF-f2. Considering its unique needle-like structure, this work is a proof of concept that micro-structure and morphology can determine the macro-properties. And this study supplies a facile method to fabricate PANI/CNF hybrid films that can be used as electrode materials in supercapacitors.

Fabrication of Free-standing Hierarchical Carbon Nanofiber/graphene Oxide/polyaniline Films for Supercapacitors

ACS Applied Materials & Interfaces. Jan, 2014  |  Pubmed ID: 24325301

A hierarchical high-performance electrode with nanoacanthine-style polyaniline (PANI) deposited onto a carbon nanofiber/graphene oxide (CNF/GO) template was successfully prepared via an in situ polymerization process. The morphology analysis shows that introducing one-dimensional (1D) CNF could significantly decrease/inhibit the staking of laminated GO to form an open-porous CNF/GO architecture. Followed with in situ facial deposition of PANI, the as-synthesized PANI modified CNF/GO exhibits three-dimensional (3D) hierarchical layered nanoarchitecture, which favors the diffusion of the electrolyte ions into the inner region of active materials. The hierarchical free-standing electrodes were directly fabricated into sandwich structured supercapacitors using 1 M H2SO4 as the electrolyte showing a significant specific capacitance of 450.2 F/g at the voltage scan rate of 10 mV/s. The electrochemical properties of the hierarchical structure can be further improved by a reduction procedure of GO before the deposition of PANI.

One-step Carbonization Synthesis of Hollow Carbon Nanococoons with Multimodal Pores and Their Enhanced Electrochemical Performance for Supercapacitors

ACS Applied Materials & Interfaces. Feb, 2014  |  Pubmed ID: 24433086

Hollow carbon capsules with multimodal pores are highly promising for developing novel electrode materials for high-performance electrochemical devices due to their more active sites for ion and electron transfer. However, at present, most of the previous efforts are focused on the multistep process for the synthesis of hollow carbon nanostructures with individual pores. Herein, hollow carbon nanococoons (HCNCs) with non-spherical cavity and multimodal hierarchical pores have been facilely synthesized via a one-step carbonization of a Fe2O3/carbon precursor core/shell nanospindle at 850 °C. We interestingly found that during the carbonization, Fe2O3 was automatically "escaped" from the inside nanospindle, leading to the formation of new HCNCs. Most importantly, the spindle-shaped cavity of the obtained HCNCs with high conductivity can offer a multimodal ion diffusion pathway, which can facilitate the reaction kinetics in a supercapacitor. As a result, the HCNCs-based supacapacitor exhibits the capacitance of 220.0 F g(-1) at a given scan rate of 5 mV s(-1), 3.5 times higher than that of hollow carbon spheres, high stability with 98% of the initial capacity maintained even after 1000 cycles, and high rate capability. This work provides a new and facile avenue for enhancing performance of a HCNCs-based supercapacitor by using the non-spherical hollow structures with multimodal pores.

Effect of Supercritical CO(2) on Fabrication of Free-standing Hierarchical Graphene Oxide/carbon Nanofiber/polypyrrole Film and Its Electrochemical Property

Physical Chemistry Chemical Physics : PCCP. Apr, 2014  |  Pubmed ID: 24623108

In this paper, supercritical carbon dioxide (SC CO2) was first reported to help prepare unique flexible free-standing graphene oxide/nanofiber (GC) films. A novel hierarchical superior electrode material with polypyrrole (PPy) deposited on GO/CNF-SC (GC-SC) films was prepared via an in situ polymerization process. Our experimental results indicate that SC CO2 can not only enlarge the space between GO sheets but also improve the conductivity of the films. The electrochemical measurements show that the as-obtained PPy-coated GC-SC products display remarkably higher capacitive properties than pristine GC/PPy products as electrode materials. Excellent rate performance and stable capacitance retention (89% after 5000 cycles) were observed during the continuous charge-discharge cycles, which verify that SC CO2 provides a convenient route to the scalable production of hierarchical GO/CNF/PPy films for potential application in supercapacitors.

Beyond Yolk-shell Nanoparticles: Fe3O4@Fe3C Core@shell Nanoparticles As Yolks and Carbon Nanospindles As Shells for Efficient Lithium Ion Storage

ACS Nano. Mar, 2015  |  Pubmed ID: 25716070

To well address the problems of large volume change and dissolution of Fe3O4 nanomaterials during Li(+) intercalation/extraction, herein we demonstrate a one-step in situ nanospace-confined pyrolysis strategy for robust yolk-shell nanospindles with very sufficient internal void space (VSIVS) for high-rate and long-term lithium ion batteries (LIBs), in which an Fe3O4@Fe3C core@shell nanoparticle is well confined in the compartment of a hollow carbon nanospindle. This particular structure can not only introduce VSIVS to accommodate volume change of Fe3O4 but also afford a dual shell of Fe3C and carbon to restrict Fe3O4 dissolution, thus providing dual roles for greatly improving the capacity retention. As a consequence, Fe3O4@Fe3C-C yolk-shell nanospindles deliver a high reversible capacity of 1128.3 mAh g(-1) at even 500 mA g(-1), excellent high rate capacity (604.8 mAh g(-1) at 2000 mA g(-1)), and prolonged cycling life (maintaining 1120.2 mAh g(-1) at 500 mA g(-1) for 100 cycles) for LIBs, which are much better than those of Fe3O4@C core@shell nanospindles and Fe3O4 nanoparticles. The present Fe3O4@Fe3C-C yolk-shell nanospindles are the most efficient Fe3O4-based anode materials ever reported for LIBs.

Thermoresponsive Photonic Crystal: Synergistic Effect of Poly(N-isopropylacrylamide)-co-acrylic Acid and Morpho Butterfly Wing

ACS Applied Materials & Interfaces. Apr, 2015  |  Pubmed ID: 25859786

In this work, we report a simple method to fabricate smart polymers engineered with hierarchical photonic structures of Morpho butterfly wing to present high performance that are capable of color tunability over temperature. The materials were assembled by combining functional temperature responsivity of poly(N-isopropylacrylamide)-co-acrylic acid (PNIPAm-co-AAc) with the biological photonic crystal (PC) structure of Morpho butterfly wing, and then the synergistic effect between the functional polymer and the natural PC structure was created. Their cooperativity is instantiated in the phase transition of PNIPAm-co-AAc (varying with the change of temperature) that can alter the nanostructure of PCs, which further leads to the reversible spectrum response property of the modified hierarchical photonic structures. The cost-effective biomimetic technique presented here highlights the bright prospect of fabrication of more stimuli-responsive functional materials via coassembling smart polymers and biohierarchical structures, and it will be an important platform for the development of nanosmart biomaterials.

Fabrication of Two-Dimensional Lateral Heterostructures of WS2 /WO3 ⋅H2 O Through Selective Oxidation of Monolayer WS2

Angewandte Chemie (International Ed. in English). Dec, 2015  |  Pubmed ID: 26494434

Two-dimensional (2D) lateral heterostructures have emerged as a hot topic in the fast evolving field of advanced functional materials , but their fabrication is challenging. The layer-structured WS2 was theoretically demonstrated to be inert to oxidation except for the monolayer, which can be selectively oxidized owing to the simultaneous interaction of oxygen with both sides. Combined with the theoretical calculations, a new method was developed for the successful construction of 2D lateral heterostructures of WS2 /WO3 ⋅H2 O in an ambient environment, based on a simple liquid-phase solution exfoliation. These lateral heterostructures of WS2 /WO3 ⋅H2 O have interesting properties, as indicated by enhanced photocatalytic activity toward the degradation of methyl orange (MO).

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