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Niranjanmurthi, Lingappan,Choi, Byung Chun,Park, Jong Myung,Lim, Kwon Taek American Scientific Publishers 2012 Journal of nanoscience and nanotechnology Vol.12 No.1
<P>Composite materials of multi-walled carbon nanotubes (MWNTs) and a conducting polymer, poly(3-thiophene boronic acid) (PTBA) were prepared by in-situ oxidative polymerization of TBA in the presence of MWNTs and potassium dichromate. The MWNTs which were previously surface functionalized with acid chloride groups were reacted with TBA using a simple 'chemical grafting' technique. It was observed that the nanotubes were dispersed uniformly in the pi-conjugated polymer matrix and entrapped by the polymer. The conductivity of the composites was higher than that of the pure polymer from a conventional four-probe technique, which indicates that the fabrication of MWNTs into the polymer matrix significantly improves the conductivity of the polymer due to the intrinsic properties of MWNTs.</P>
Lingappan, Niranjanmurthi,Van, Ngoc Huynh,Lee, Suok,Kang, Dae Joon Elsevier 2015 Journal of Power Sources Vol.280 No.-
<P><B>Abstract</B></P> <P>We report the design and synthesis of three dimensional flower-like molybdenum disulphide (<I>f</I>-MoS<SUB>2</SUB>) hierarchical structures, on reduced graphene oxide (RGO)/oxidized multi-walled carbon nanotube (o-MWCNT) backbone (<I>f</I>-MoS<SUB>2</SUB>/RGO/o-MWCNT), through one-pot hydrothermal method. Control experiments reveal that the homogenously distributed o-MWCNTs on RGO play an essential role for the formation of such morphology. As an anode for lithium ion batteries, the <I>f</I>-MoS<SUB>2</SUB>/RGO/o-MWCNT hybrid delivers a high reversible capacity of 1275 mAh g<SUP>−1</SUP> at the current density of 100 mA g<SUP>−1</SUP>, superior rate capability and excellent long cycle life, with capacity retention of 93% after 100 cycles. The outstanding electrochemical performance can be attributed to the large surface area, short diffusion length and continuous electron transport pathway, as a consequence of the intimate contact between <I>f</I>-MoS<SUB>2</SUB>, graphene, and o-MWCNTs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flower-like MoS<SUB>2</SUB> grown on RGO/o-MWCNT backbone <I>via</I> hydrothermal process. </LI> <LI> Flower-like structure with the average size ranging between 1.1∼1.3 μm formed. </LI> <LI> Formation and growth mechanism of the structures were investigated in detail. </LI> <LI> The as-prepared hybrid used as an anode for lithium-ion batteries. </LI> <LI> It exhibited enhanced electrochemical performance due to the rationally designed structure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lingappan, Niranjanmurthi,Kang, Dae Joon Elsevier 2016 ELECTROCHIMICA ACTA Vol.193 No.-
<P><B>Abstract</B></P> <P>We demonstrate an efficient and large-scale synthesis approach of a novel heterostructure comprised of molybdenum disulfide (MoS<SUB>2</SUB>) and nitrogen-doped reduced graphene oxide (n-RGO) hydrogel (MoS<SUB>2</SUB>/n-RGO) <I>via</I> two-step hydrothermal process. Due to the strong molybdenumnitrogen (MoN) bond, the n-RGO sheets are well interconnected to the MoS<SUB>2</SUB> sheets and restacking of the two components is minimized. The hybrid possesses an open-pore structure, large surface area, and high nitrogen content. As an anode for lithium-ion batteries, the MoS<SUB>2</SUB>/n-RGO manifests a high specific capacity of 1140mA h g<SUP>1</SUP> at the current density of 100mAg<SUP>1</SUP>, which is higher than that of the MoS<SUB>2</SUB>/non-doped RGO (MoS<SUB>2</SUB>/RGO) counterpart. A remarkable rate capability and excellent electrochemical stability (94% retention after 130 cycles) is also achieved. Furthermore, the MoS<SUB>2</SUB>/n-RGO hybrid delivers a maximum energy density of 890 Wh kg<SUP>1</SUP> with the power density of 130Wkg<SUP>1</SUP>. The superior electrochemical performance can be attributed to the durability and improved charge kinetics of the MoS<SUB>2</SUB>/n-RGO heterostructure owing to the nitrogen-doping effect. This study sheds light on the importance of a nitrogen-doped architecture in the creation of novel functional materials that can act as advanced electrodes for lithium-ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB>/n-RGO hybrid was synthesized by two-step hydrothermal process. </LI> <LI> The structure and morphology were investigated in detail. </LI> <LI> Hybrid manifests excellent electrochemical properties. </LI> <LI> It also exhibits high energy and power densities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Noncovalent grafting of poly(3-octylthiophene) at the edges of the graphene nanosheets.
Lingappan, Niranjanmurthi,Kim, Do Hoon,Gal, Yeong-Soon,Hong, Seong-Soo,Lim, Kwon Taek American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.11
<P>Noncovalent functionalization of graphene was carried out via in-situ oxidative polymerization of poly(3-octylthiophene) (P3OT). First, graphene sheets were prepared by a modified Hummer's method and subsequently reduced with hydrazine monohydrate. The structure and morphology of the composites were investigated by using FTIR, XPS, EDX, TGA, HRTEM, FESEM and XRD measuments. The results obtained from spectroscopic studies confirm the reduction of graphite oxide to graphene. UV-Vis and photoluminescence spectroscopies were also used to prove the doping function of the graphene in the composites. Dispersion stability indicates the good mixing between graphene and the polymer due to pi-pi interaction between two components. Scanning electron microscopy results suggest that the graphene sheets were well dispersed in the polymer matrix. The UV-Vis spectra of graphene/P3OT composites show a red shift by a few nanometers, while the emission spectra show a small blue shift. However, the nanocomposites retained the photoluminescence property of as synthesized P3OT.</P>
Preparation and characterization of graphene/poly(diphenylamine) composites.
Lingappan, Niranjanmurthi,Jeong, Yeon Tae,Gal, Yeong-Soon,Lim, Kwon Taek American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.5
<P>Nanocomposites of graphene nanosheets and poly(diphenylamine) (graphene-PDPA) were synthesized via the in-situ oxidative polymerization of diphenylamine in a sulphuric acid medium. First, graphite oxide (GO) was prepared by oxidation of natural graphite using the modified Hummer's method and subsequently reduced using hydrazine monohydrate. The as-prepared graphene sheets were noncovalently grafted with PDPA using ammonium peroxydisulphate as an oxidant. During the polymerization, graphene sheets were homogeneously dispersed in the PDPA matrix. The formation of the hybrid material was confirmed by FTIR, XPS, TGA, HRTEM, FESEM and XRD measurements. XPS analysis revealed the removal of oxygen functionality from the GO surface after reduction and the bonding structure of the reduced hybrids. In addition, the nanocomposites showed better thermal properties due to the intrinsic property of the graphene sheets.</P>
Water soluble graphene oxide/poly(1-vinylimidazole) composites: synthesis and characterization.
Lingappan, Niranjanmurthi,Kim, Do Hoon,Park, Jong Myung,Lim, Kwon Taek American Scientific Publishers 2014 Journal of nanoscience and nanotechnology Vol.14 No.8
<P>Modified graphene oxide/poly(1-vinylimidazole) (mGO/PVIm) composites were prepared via surface-initiated free radical graft polymerization. First, the hydroxyl-enriched GO sheets were functionalized with 3-methacryloxypropyltrimethoxysilane to introduce active-vinyl groups on the GO surfaces. Subsequently, 1-vinylimidazole was chemically grafted and polymerized in the presence of mGO. The chemical structures and morphology of the covalently bonded composites were characterized using FTIR, XPS, TGA, HRTEM, FESEM and XRD measurements. The mGO/PVIm composites exhibit a stable dispersion in water and show high storage stability (>10 days). Furthermore, the morphological analysis showed that mGO was homogeneously dispersed in the polymer matrix.</P>