Seonmyeong Noh

Surfactant-Templated Synthesis of Polypyrrole Nanocages as Redox Mediators for Efficient Energy Storage

Preparation of conducting-polymer hollow nanoparticles with different diameters was accomplished by surfactant templating. An anionic surfactant, namely sodium dodecylbenzenesulfonate, formed vesicles to template with the pyrrole monomer. Subsequent chemical oxidative polymerization of the monomer yielded spherical polypyrrole (PPy) nanoparticles with hollow interiors. The diameter of the hollow nanoparticles was easily controlled by adjusting the concentration of the surfactant. Subsequently, the size-dependent electrochemical properties of the nanoparticles, including redox properties and charge/discharge behavior, were examined. By virtue of the structural advantages, the specific capacitance (max. 326 F g−1) of PPy hollow nanoparticles was approximately twice as large as that of solid PPy nanospheres. The hollow PPy nanostructure can easily be used as a conductive substrate for the preparation of metal/polymer nanohybrids through chemical and electrochemical deposition. Two different pseudocapacitive metal-oxide clusters were readily deposited on the inner and outer surfaces of the hollow nanoparticles, which resulted in an increase in the specific capacitance to 390 F g−1. In addition, the hollow nanoparticles acted as a nanocage to prevent metal ion leaching during charge/discharge, thus allowing an excellent capacitance retention of ca. 86%, even following 10,000 cycles.

Nanoparticle-Mediated Physical Exfoliation of Aqueous-Phase Graphene for Fabrication of Three-Dimensionally Structured Hybrid Electrodes

Monodispersed polypyrrole (PPy) nanospheres were physically incorporated as guest species into stacked graphene layers without significant property degradation, thereby facilitating the formation of unique three-dimensional hybrid nanoarchitecture. The electrochemical properties of the graphene/particulate PPy (GPPy) nanohybrids were dependent on the sizes and contents of the PPy nanospheres. The nanohybrids exhibited optimum electrochemical performance in terms of redox activity, charge-transfer resistance, and specific capacitance at an 8:1 PPy/graphite (graphene precursor) weight ratio. The packing density of the alternately stacked nanohybrid structure varied with the nanosphere content, indicating the potential for high volumetric capacitance. The nanohybrids also exhibited good long-term cycling stability because of a structural synergy effect. Finally, fabricated nanohybrid-based flexible all–solid state capacitor cells exhibited good electrochemical performance in an acidic electrolyte with a maximum energy density of 8.4 Wh kg−1 or 1.9 Wh L−1 at a maximum power density of 3.2 kW kg−1 or 0.7 kW L−1; these performances were based on the mass or packing density of the electrode materials.

Carboxylic Acid-Functionalized Conducting-Polymer Nanotubes as Highly Sensitive Nerve-Agent Chemiresistors.

Organophosphates are powerful inhibitors of acetylcholinesterase, which is critical to nerve function. Despite continuous research for detecting the highly toxic organophosphates, a new and improved methodology is still needed. Herein we demonstrate simple-to-fabricate chemiresistive gas sensors using conducting-polymer polypyrrole (PPy) nanotube transducers, which are chemically specific and capable of recognizing sub-ppb concentrations (ca. 0.5 ppb) of dimethyl methylphosphonate (DMMP), a simulant of nerve agent sarin. Interestingly, the introduction of carboxylic groups on the surface of PPy nanotube transistors resulted in enhanced sensitivity to DMMP via intermolecular hydrogen bonding. Furthermore, it was found that the sensitivity of the nanotube transducer depended on the degree of the carboxylic group introduced. Finally, a sensor array composed of 5 different transducers including the carboxylated nanotubes exhibited excellent selectivity to DMMP in 16 vapor species.

Physical exfoliation of graphene and molybdenum disulfide sheets using conductive polyaniline: an efficient route for synthesizing unique, random-layered 3D ternary electrode materials

Vertically random-layered three-dimensional ternary nanohybrids were synthesized by combining graphene, molybdenum disulfide (MoS2), and polyaniline (PANI) via a simple physical exfoliation process. During this process, PANI penetrates the interlayers of bulk MoS2 without the requirement for any additional chemical treatment, effectively dispersing MoS2 layers in the liquid phase. In addition, graphene, with several functional groups on its surface, and PANI convert the semiconducting trigonal prismatic phase of MoS2 to a metallic octahedrally coordinated phase, thereby enhancing the electrical conductivity. Moreover, the obtained nanohybrid has an open porous structure that facilitates electrolyte-mediated ion and charge transfer, which increases the effective surface area for electrochemical reactions and charge storage. The effect of different graphene, MoS2, and PANI contents on the electrical/electrochemical properties of the nanohybrids was investigated, and the optimal composition for the use of the nanohybrid as an electrode material was determined. Notably, the nanohybrid with a nominal graphene/MoS2/PANI weight ratio of 1 : 1 : 80 exhibited excellent electrochemical properties, exemplified by the prominent redox reaction, low charge transfer resistance, and high specific capacitance. Flexible all-solid-state capacitor cells employing the nanohybrid achieved a maximum capacitance of 162 F g−1, good flexibility, and good long-term cycling stability in two different electrolytes, i.e., acidic and neutral solution.

Corrigendum: Surfactant-Templated Synthesis of Polypyrrole Nanocages as Redox Mediators for Efficient Energy Storage.

Scientific Reports 5: Article number: 1409710.1038/srep14097; published online: September162015; updated: March212016 This Article contains an error in the order of the Figures. Figure 6 and Figure 7 were published as Figure 7 and Figure 6 respectively. The correct Figures 6 and 7 appear below as Figs 1 and ​and22 respectively. The Figure legends are correct. Figure 1 Figure 2