K. Hareesh

Reduction of graphene oxide by 100 MeV Au ion irradiation and its application as H2O2 sensor

Graphene oxide (GO) synthesized from a modified Hummers method was reduced (referred, rGO) by using 100 MeV Au ion species and its response to the sense H2O2 was investigated. The changes in the atomic composition and structural properties of rGO after irradiation were studied using x-ray diffraction, Fourier transform infrared spectroscopy and x-ray photo-electron spectroscopy. These results suggested that the removal of the oxygen-containing functional groups and the improvement of the electrochemical performance of reduced graphene oxide (rGO) after ion irradiation. Raman spectroscopic results revealed the increase in the disorder parameter (I D/I G) after Au ion irradiation and also the formation of a large number of small sp2 domains due to the electronic energy loss of ion beam. The resultant rGO was investigated for H2O2 sensing using electrochemical techniques and it showed a good response.

Bio-green synthesis of Ag–GO, Au–GO and Ag–Au–GO nanocomposites using Azadirachta indica: its application in SERS and cell viability

Silver-graphene oxide, Gold–graphene oxide, Silver–Gold–graphene oxide nanocomposites were synthesized from Neem leaves (Azadirachta indica) extract using a bio-green one-pot method. The synthesized bio-green nanocomposites were characterized by UV–visible spectroscopy, x-ray diffractogram, transmission electron microscopy, x-ray photoelectron spectroscopy and Raman spectroscopy. The results indicated the decoration of ~10 nm of silver, ~20 nm of gold and ~15 nm of silver–gold nanoparticles on a graphene oxide sheet. The synthesized nanocomposites showed enhancement in surface enhanced Raman spectroscopy with alizarin and also enhancement in cell viability of Chang liver cell lines which may be due to a synergetic effect of nanoparticles and graphene oxide.

High-field emission performance of a NiFe2O4/rGO/CNT tertiary nanocomposite

Herein, we report the field emission properties of NiFe2O4/reduced graphene oxide/carbon nanotubes (NGC) and compared them with the field emission properties of NiFe2O4/carbon nanotubes (NC) and NiFe2O4/reduced graphene oxide (NG). The NGC nanocomposite showed a very low turn-on field of ∼0.4 V μm−1 and a high emission current density of ∼8.228 mA cm−2 at a low applied electric field of 1.6 V μm−1. In addition, it exhibited extremely good emission current stability at a preset value of ∼20 μA. The observed very low turn on field of the NGC nanocomposite is due to its lower value of effective work function (1.92 eV), and the results suggest the potential of the synthesized emitter for practical applications in vacuum micro-electronics/nano-electronics.

Ultra high stable supercapacitance performance of conducting polymer coated MnO2 nanorods/rGO nanocomposites

A ternary nanocomposite that consists of MnO2 nanorods and reduced graphene oxide sheets supported on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) polymer has been developed for supercapacitor applications. X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, the Brunauer–Emmett–Teller method and X-ray photoelectron spectroscopic analysis confirmed the formation of a ternary nanocomposite of PEDOT:PSS/MnO2 nanorods/rGO. Electrochemical investigation of these materials in acetonitrile containing lithium per chlorate demonstrated an enhanced specific capacitance of 633 F g−1 at a current density of 0.5 A g−1 and 100% stability up to 5000 charging–discharging cycles at 1 A g−1. The enhanced capacitance and working stability of the PEDOT:PSS/MnO2 nanorods/rGO nanocomposite along with the simplicity in making the active materials make this system a promising candidate for the commercial development of supercapacitors.

Structural, morphological, thermal and dosimetric properties of CaF2:Dy nanophosphor for 100 keV Cu− ion irradiation

We report the structural, morphological and thermal properties of CaF2:Dy nanophosphor synthesized by chemical co-precipitation method. 100 keV, negative Copper ion irradiation was used for the study of Thermoluminescence dosimetric properties. The X-ray diffraction shows a cubic structure having crystalline size around 45 to 50 nm. TEM analysis showed that the size of nanoparticles is in the range of 90 to 110 nm and TGA-DSC analysis of thermal effect showed the weight loss on CaF2:Dy nanophosphor. Finally, a thermoluminescence dosimetric property indicates good glow curve behavior with an extensive linear response.