Synthesis and characterization of novel conducting composites of Fe₃O₄ nanoparticles and sulfonated polyanilines

Reddy, Kakarla Raghava,Lee, Kwang-Pill,Iyengar, Anantha Gopalan Wiley Subscription Services, Inc., A Wiley Company 2007 Journal of applied polymer science Vol.104 No.6

<P>Surface charged iron oxide (Fe<SUB>3</SUB>O<SUB>4</SUB>) nanoparticles were used for the synthesis of sulfonated polyaniline (SPAN)-Fe<SUB>3</SUB>O<SUB>4</SUB> nanocomposites (SPAN/Fe<SUB>3</SUB>O<SUB>4</SUB>-NCs). 2,5-diaminobenzenesulfonic acid (DABSA) and 2-aminobenzenesulfonic acid (ABSA) were independently polymerized with aniline to form SPAN. The structure of the composites was characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, conductivity and magnetic properties. TEM reveals that Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles are “glued” with SPAN in the composite. TGA indicates that SPAN/Fe<SUB>3</SUB>O<SUB>4</SUB>-NCs are having better thermal stability. The room temperature conductivity of SPAN/Fe<SUB>3</SUB>O<SUB>4</SUB>-NCs is higher than that of pristine PANI and SPAN. SPAN/Fe<SUB>3</SUB>O<SUB>4</SUB>-NCs exhibits magnetic behavior. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4127–4134, 2007</P>

Synthesis of MWCNTs-core/thiophene polymer-sheath composite nanocables by a cationic surfactant-assisted chemical oxidative polymerization and their structural properties

Reddy, Kakarla Raghava,Jeong, Han Mo,Lee, Youngil,Raghu, Anjanapura Venkataramanaiah Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of polymer science Part A, Polymer chemist Vol.48 No.7

<P>Multi-walled carbon nanotubes (MWCNTs)-core/thiophene polymer-sheath composite nanocables were synthesized by chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) with oxidant (FeCl<SUB>3</SUB>) in the presence of cationic surfactant, deceyltrimethyl ammonium bromide (DTAB). In the polymerization process, DTAB surfactant molecules were adsorbed on the surface of MWCNTs and forms MWCNTs-DTAB soft template. Upon the addition of EDOT and oxidant, the polymerization take place on the surface of MWCNTs and PEDOT is gradually deposited on the surface of MWCNTs. The resulting MWCNTs-PEDOT nanocomposites have the nanocable structure. Nanocomposites were characterized by HRTEM, FE-SEM, XRD, XPS, TGA, FTIR and PL, respectively. The π-π interactions between PEDOT and MWCNTs enhancing the thermal and electrical properties of the nanocomposites with loading of MWCNTs. The temperature dependence conductivity measurements show that the conductivity of the nanocomposite decrease with a decrease of temperature, and conductivity-temperature relationship is well fit by the quasi-one dimensional variable range hopping mode. The mechanism for the formation of composite nanocables was explained on the basis of self- assembly of micelles. The reported self-assembly strategy for the synthesis of PEDOT-coated MWCNTs in micellar medium is a rapid, versatile, potentially scalable, stable, and making it useful for further exploitation in a varies types of applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1477–1484, 2010</P> <B>Graphic Abstract</B> <P>The MWCNTs-thiophene polymer core-sheath composite nanocables were synthesized by chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) with oxidant (FeCl<SUB>3</SUB>) in the presence of cationic surfactant, deceyltrimethyl ammonium bromide (DTAB) that acts as the structure-directing agen. In the polymerization process, DTAB surfactant molecules were adsorbed on the surface of MWCNTs and forms MWCNTs-DTAB soft template. On the addition of EDOT and oxidant, the polymerization takes place on the surface of MWCNTs, and PEDOT is gradually deposited on the surface of MWCNTs. The resulting nanocomposites have the nanocable structure as shown in the scheme. The structural, morphological, thermal, optical, and electrical properties of the synthesized nanocomposites were fully characterized by using various techniques. The mechanism for the formation of composite nanocables was explained on the basis of self-assembly of micelles. The reported self-assembly strategy for the synthesis of PEDOT-coated MWCNTs in micellar medium is a rapid, versatile, potentially scalable, stable, and making it useful for further exploitation in various types of applications. <img src='wiley_img_2010/0887624X-2010-48-7-POLA23883-gra001.gif' alt='wiley_img_2010/0887624X-2010-48-7-POLA23883-gra001'> </P>

Novel electrically conductive and ferromagnetic composites of poly(aniline-co-aminonaphthalenesulfonic acid) with iron oxide nanoparticles: Synthesis and characterization

Reddy, Kakarla Raghava,Lee, Kwang-Pill,Gopalan, Anantha Iyengar Wiley 2007 Journal of Applied Polymer Science Vol.106 No.2

<P>Nanocomposites of iron oxide (Fe<SUB>3</SUB>O<SUB>4</SUB>) with a sulfonated polyaniline, poly(aniline-co-aminonaphthalenesulfonic acid) [SPAN(ANSA)], were synthesized through chemical oxidative copolymerization of aniline and 5-amino-2-naphthalenesulfonic acid/1-amino-5-naphthalenesulfonic acid in the presence of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles. The nanocomposites [Fe<SUB>3</SUB>O<SUB>4</SUB>/SPAN(ANSA)-NCs] were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, UV–visible spectroscopy, thermogravimetric analysis (TGA), superconductor quantum interference device (SQUID), and electrical conductivity measurements. The TEM images reveal that nanocrystalline Fe<SUB>3</SUB>O<SUB>4</SUB> particles were homogeneously incorporated within the polymer matrix with the sizes in the range of 10–15 nm. XRD pattern reveals that pure Fe<SUB>3</SUB>O<SUB>4</SUB> particles are having spinel structure, and nanocomposites are more crystalline in comparison to pristine polymers. Differential thermogravimetric (DTG) curves obtained through TGA informs that polymer chains in the composites have better thermal stability than that of the pristine copolymers. FTIR spectra provide information on the structure of the composites. The conductivity of the nanocomposites (∼ 0.5 S cm<SUP>−1</SUP>) is higher than that of pristine PANI (∼ 10<SUP>−3</SUP> S cm<SUP>−1</SUP>). The charge transport behavior of the composites is explained through temperature difference of conductivity. The temperature dependence of conductivity fits with the quasi-1D variable range hopping (quasi-1D VRH) model. SQUID analysis reveals that the composites show ferromagnetic behavior at room temperature. The maximum saturation magnetization of the composite is 9.7 emu g<SUP>−1</SUP>. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007</P>

Synthesis and properties of magnetite/poly (aniline-co-8-amino-2-naphthalenesulfonic acid) (SPAN) nanocomposites

Reddy, Kakarla Raghava,Lee, Kwang-Pill,Gopalan, Anantha Iyengar,Showkat, Ali Md JOHN WILEY & SONS LTD 2007 POLYMERS FOR ADVANCED TECHNOLOGIES Vol.18 No.1

<P>Composites were prepared by incorporating magnetite (Fe<SUB>3</SUB>O<SUB>4</SUB>) nanoparticles into the matrix of a sulfonated polyaniline (SPAN) [poly(aniline-co-8-amino-2-naphthalenesulfonic acid) PANSA] through chemical oxidative polymerization of a mixture of aniline and 8-amino-2-naphthalenesulfonic acid in the presence of magnetite nanoparticles. The composite, magnetite/SPAN(PANSA) was characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), elemental analysis (EA), Fourier transform infrared (FT-IR) spectra, UV-vis spectroscopy, thermogravimetric analysis (TGA), conductivity and magnetic properties measurements. TEM image shows that magnetite nanoparticles were finely distributed into the SPAN matrix. XRD pattern of the nanocomposite reveals the presence of additional crystalline order through the appearance of a sharp peak at ∼43° and 71°. Conductivity of the nanocomposite (0.23 S/cm) is much higher than pristine copolymer (1.97 × 10<SUP>−2</SUP> S/cm). The results of FT-IR and UV-visible spectroscopy reveal the presence of molecular level interactions between SO<EM><SUB>3</SUB><SUP>−</SUP></EM> groups in SPAN and magnetite nanoparticles in the composite. Copyright © 2006 John Wiley & Sons, Ltd.</P>

Synthesis of metal (Fe or Pd)/alloy (Fe–Pd)-nanoparticles-embedded multiwall carbon nanotube/sulfonated polyaniline composites by γ irradiation

Reddy, Kakarla Raghava,Lee, Kwang-Pill,Gopalan, Anantha Iyengar,Kim, Min Seok,Showkat, Ali Md,Nho, Young Chang Wiley Subscription Services, Inc., A Wiley Company 2006 Journal of polymer science Part A, Polymer chemist Vol.44 No.10

<P>Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5-diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe–Pd alloy nanoparticles were embedded into the MWCNT–SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with γ radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of γ radiation. The existence of metallic/alloy particles in the MWCNT–SPAN matrix was further ascertained through characterization by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe–Pd nanoparticles of various sizes in the MWCNT–SPAN matrices. There were changes in the electronic properties of the MWCNT–SPAN–M composites due to the interaction between the metal nanoparticles and MWCNT–SPAN. Metal-nanoparticle-loaded MWCNT–SPAN composites (MWCNT–SPAN–M; M = Fe, Pd, or Fe–Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT–SPAN–M composites was approximately 1.5 S cm<SUP>−1</SUP>, which was much higher than that of SPAN (2.46 × 10<SUP>−4</SUP> S cm<SUP>−1</SUP>). Metal/alloy-nanoparticle-embedded, MWCNT-based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355–3364, 2006</P> <B>Graphic Abstract</B> <P>Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) loaded with metal (M = Fe, Pd, or Fe–Pd alloy) nanoparticles were synthesized by γ irradiation. The synthesis consisted of two steps: the preparation of the composite of SPAN with MWCNTs and the loading of the metal nanoparticles into the MWCNT–SPAN composite matrix via the reduction of higher valence metal ions by γ irradiation. The MWCNT–SPAN–M nanocomposites exhibited improved thermal stability and conductivity over pristine SPAN. The presence of metal/alloy nanoparticles induced quantum size effects in the electronic properties of the composites. <img src='wiley_img/0887624X-2006-44-10-POLA21451-gra001.gif' alt='wiley_img/0887624X-2006-44-10-POLA21451-gra001'> </P>

Mn-doped ZrO₂ nanoparticles prepared by a template-free method for electrochemical energy storage and abatement of dye degradation

Reddy, Chandragiri Venkata,Reddy, I. Neelakanta,Akkinepally, Bhargav,Harish, V.V.N.,Reddy, Kakarla Raghava,Jaesool, Shim Elsevier 2019 CERAMICS INTERNATIONAL Vol.45 No.12

<P><B>Abstract</B></P> <P>A template-free technique was used to prepare pure and Mn-doped ZrO<SUB>2</SUB> photocatalyst samples in this study. The effect of doping on the structural, optical, photocatalytic, and supercapacitor properties were investigated. X-ray diffraction analysis revealed that the prepared samples had a tetragonal crystal structure. The optical band gap was narrowed due to the incorporation of Mn ions. The photocatalytic activity of methyl orange organic dye degradation with the Mn-doped ZrO<SUB>2</SUB> sample was examined under visible-light irradiation. The doped sample showed 83% of dye degradation after 100 min of irradiation. Cyclic voltammetry was used to study the supercapacitor properties, and the doped samples exhibited capacitance seven times greater than that of the pure sample.</P>

Template-free synthesis of tetragonal Co-doped ZrO₂ nanoparticles for applications in electrochemical energy storage and water treatment

Reddy, Ch Venkata,Reddy, I. Neelakanta,Reddy, Kakarla Raghava,Jaesool, Shim,Yoo, Kisoo Elsevier 2019 ELECTROCHIMICA ACTA Vol.317 No.-

<P><B>Abstract</B></P> <P>Template-free synthesis of pure and Co-doped ZrO<SUB>2</SUB> tetragonal structured nanoparticles was achieved by the hydrothermal method and their photocatalytic, photoelectrocatalytic, and electrochemical energy storage supercapacitive properties were investigated for the first time. XRD revealed tetragonal crystal structure, while BET surface analysis suggested that Co-doped ZrO<SUB>2</SUB> has higher surface area (186.4 m<SUP>2</SUP>g<SUP>−1</SUP>) than that of the undoped sample (99.5 m<SUP>2</SUP>g<SUP>−1</SUP>). The band gap value was reduced from 4.95 to 2.12 eV due to incorporation of cobalt. Under visible-light illumination, photocatalytic and photoelectrocatalytic activities for methyl orange (MO) dye degradation were evaluated. The working electrodes have been prepared with 85 wt% active material (pure and doped ZrO<SUB>2</SUB>), 10 wt% active carbon black, and 5 wt% polyvinylidene difluoride (PVDF) in order to perform the supercapacitive properties. The Co-doped ZrO<SUB>2</SUB> material exhibited 93.7% and 27.4% MO dye degradation within 100 min with the highest specific capacitance value of 2151.2 Fg<SUP>-1</SUP>.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Self-assembly directed synthesis of poly(ortho-toluidine)-metal(gold and palladium) composite nanospheres.

Reddy, Kakarla Raghava,Lee, Kwang-Pill,Gopalan, Anantha Iyenger American Scientific Publishers 2007 Journal of nanoscience and nanotechnology Vol.7 No.9

<P>Poly(ortho-toluidine) (POT)-gold (Au) and palladium (Pd) composite nanospheres were successfully synthesized by the reaction of o-toluidine with the corresponding metal (Au or Pd) colloidal solution through self-assembly process in the presence of dodecylbenzenesulfonic acid (DBSA), which acts as both a dopant and surfactant, and ammonium peroxydisulfate as an oxidizing agent. The composites (POT-DBSA/Au or Pd) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, UV-Visible (UV-Vis) spectroscopy, and electrical conductivity measurements. TEM images of the nanocomposites reveal that metal (Au or Pd) nanoparticles were well dispersed on POT spheres. TGA and XRD results show that the composites exhibit high thermal stability and are more crystalline compared with pristine POT. It was found that the electrical conductivity of the POT-DBSA/Au or Pd composites is 2 orders of magnitude higher than that of pristine polymer. Also, the POT-DBSA/Pd composite exhibits magnetic property. The formation mechanism of the POT-DBSA/Au or Pd composite nanosphere is discussed.</P>

Graphite Oxides as Effective Fire Retardants of Epoxy Resin

이유락,김순철,이형일,정한모,Anjanapura V. Raghu,Kakarla Raghava Reddy,김병규 한국고분자학회 2011 Macromolecular Research Vol.19 No.1

Graphite oxides (GOs) at various oxidation states were examined as fire retardants of epoxy resin. Excessive oxidation is detrimental to the fire retardant effect of GO because it generated a weak GO with reduced intumescent ability. GO manifested optimum fire retardant properties when it was properly oxidized due to the effective intumescence, demonstrating that intumescent GO needs to be strong enough to effectively push the epoxy resin matrix apart to cause efficient intumescence and generate a solid remnant char that acts as an efficient barrier. The fire retardant effect of GO was also reduced when a dispersion of GO in the epoxy resin was enhanced by sonication. This shows that the fine dispersion and disordering of layered structure of GO by the intercalation of epoxy molecules into the gallery of GO also reduced the intumescent ability, and the fire retardant effects of GO.

Nanoarchitectured Graphene-Organic Frameworks (GOFs): Synthetic Strategies, Properties, and Applications

Haque, Enamul,Yamauchi, Yusuke,Malgras, Victor,Reddy, Kakarla Raghava,Yi, Jin Woo,Hossain, Md. Shahriar A.,Kim, Jeonghun Wiley (John WileySons) 2018 Chemistry - An Asian Journal Vol.13 No.23