S.S. Dahiwale

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.

Surface chemical bonds, surface-enhanced Raman scattering, and dielectric constant of SiO2 nanospheres in-situ decorated with Ag-nanoparticles by electron-irradiation

Nanostructures of dielectric materials decorated with metal nanoparticles are of great scientific interest; however, the involved synthesis methods are complicated and require multistep chemical processing, including functionalization of the dielectric surfaces. In the present work, without chemical processes, silver nanoparticles of average sizes in the range of 11 to 15 nm were in-situ synthesized and decorated on SiO2 nanospheres in a single step process by irradiating a solution (AgNO3–polyvinylpyrrolidone (PVP)–SiO2 nanospheres) with 6 MeV electrons at 1.5 × 1015 e−/cm2, 3.0 × 1015 e−/cm2, and 4.5 × 1015 e−/cm2 fluences. The electron irradiated solutions were characterized with different surface and other techniques. The results revealed that the SiO2 nanospheres were uniformly decorated with Ag nanoparticles, and the prominent chemical bonds involved were Ag–O, Si–O–Ag, and Si–Ag. Moreover, the sizes and the decoration density of Ag nanoparticles could be tailored by varying electron fluence. The Su...

Synthesis and characterization of CaF2:Dy nanophosphor for dosimetric application

In this work, nanoparticles (NPs) of dysprosium doped calcium fluoride (CaF2:Dy) 1 mol % has been prepared using simple chemical co-precipitation method and its thermoluminescence (TL) dosimetric properties were studied. The synthesized nanoparticle sample was characterized by X-ray diffraction (XRD) and the particle size of face centered cubic phase NPs was found around 30 nm. The shape, morphology and size were also observed by scanning electron microscopy (SEM). From gamma irradiated CaF2:Dy TL curves, it was observed that the total areas of all the glow peak intensities are dramatically changed with increase in annealing temperature. Further, TL glow curve of the CaF2:Dy at 183 °C annealed at 400 °C, showed very sharp linear response in the dose range from 1 Gy to 750 Gy. This linear response of CaF2:Dy nanophosphor as a function of gamma dose is very useful from radiation dosimetric point of view.

A Study on the Optimization of the SiN x :H Film for Crystalline Silicon Sloar Cells

The Hydrogenated silicon nitride (SiNx:H) using plasma enhanced chemical vapor deposition is widely used in photovoltaic industry as an antireflection coating and passivation layer. In the high temperature firing process, the film should not change the properties for its use as high quality surface layer in crystalline silicon solar cells. Initially PECVD- film trends were investigated by varying the deposition parameters (temperature, electrode gap, RF power, gas flow rate etc.) to optimize the process parameter conditions. Then by varying gas ratios (), the hydrogenated silicon nitride films were analyzed for its optical, electrical, chemical and surface passivation properties. The films of refractive indices 1.90~2.20 were obtained. The film deposited with the gas ratio of 3.6 (Refractive index

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.

Studies on matrix interferences during uranium analysis by extractive liquid scintillation technique

The efficiency of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) in reducing the influence of salinity and extraction of iron and calcium into the organic phase along with uranium was studied. DTPA has been observed to be more suitable complexing agent compared to EDTA. Iron and calcium were found to be separated quantitatively with more than 95% recovery for uranium, facilitating its rapid and interference free analysis in the presence of DTPA. Uranium recovery under high salinity conditions was also observed to be in the range 89.7–98.6% in the presence of DTPA.

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.

Thermoluminescence response of K2Ca2(SO4)3 nanophosphor Co-doped with Eu and Ce for gamma ray dosimetry

K2Ca2(SO4)3 nanophosphors co-doped with Eu and Ce were synthesized by the chemical co-precipitation method. These samples were further annealed at 700 °C structural reformation. The structural and morphological characteristics were studied using XRD and TEM techniques. The particle size calculated from XRD spectra was around 35 nm. The as synthesized sample shows cubic structure annealed at 700 °C. The as synthesized and annealed sample of K2Ca2(SO4)3: EuCe were irradiated with Co60 gamma rays for the doses from 2Gy to 1kGy. The TL characteristic sample of co-doped were studied for the dosimetric application by gamma radiation. The TL spectrum of annealed sample has single peaked at 160 °C. The Eu doped sample has a high TL sensitivity than Ce doped sample. But after co-doping with Eu and Ce, TL intensity observed to be decreased. The decrees in TL peak intensity of the phosphor on co-doping of Eu and Ce gives an insight into the emission mechanism of the phosphor which involves energy transfer from Eu to...

Lithium diffusion in polyether ether ketone and polyimide stimulated by in situ electron irradiation and studied by the neutron depth profiling method

Diffusion of lithium from a LiCl aqueous solution into polyether ether ketone (PEEK) and polyimide (PI) assisted by in situ irradiation with 6.5 MeV electrons was studied by the neutron depth profiling method. The number of the Li atoms was found to be roughly proportional to the diffusion time. Regardless of the diffusion time, the measured depth profiles in PEEK exhibit a nearly exponential form, indicating achievement of a steady-state phase of a diffusion–reaction process specified in the text. The form of the profiles in PI is more complex and it depends strongly on the diffusion time. For the longer diffusion time, the profile consists of near-surface bell-shaped part due to Fickian-like diffusion and deeper exponential part.

Design and development of the 6–18 MeV electron beam system for medical and other applications

ABSTRACT A system for the electron and photon therapy has been designed and developed at SAMEER, IITB, Mumbai. All the components of the system such as the 270° beam bending electromagnet, trim coils, magnet chamber, electron scattering foil, slits, applicators, etc., were designed and fabricated indigenously. The electrons of 6, 8, 9, 12, 15 and 18 MeV energies were provided by a linear accelerator, indigenously designed and made at SAMEER, IITB campus, Mumbai. The electron beam from the LINAC enters the magnet chamber horizontally, and after deflection and focusing in the 270° bending magnet, comes out of the exit port, and travels a straight path vertically down. After passing through the beryllium and tantalum scattering foils, the electron beam gets scattered and turns into a solid cone shape such that the diameter increases with the travel distance. The simulation results indicate that at the exit port of the 270° beam bending magnet, the electron beam has a divergence angle of ≤ 3 mrad and diameter ∼2–3 mm, and remains constant over 6–18 MeV. Normally, 6–18 MeV electrons are used for the electron therapy of skin and malignant cancer near the skin surface. On a plane at a distance of 100 cm from the scattering foils, the size of the electron beam could be varied from 10 cm × 10 cm to 25 cm × 25 cm using suitable applicators and slits. Different types of applicators were therefore designed and fabricated to provide required beam profile and dose of electrons to a patient. The 6 MeV cyclic electron accelerator called Race-Track Microtron of S. P. Pune University, Pune, was extensively used for studying the performances of the scattering foils, electron beam uniformity and radiation dose measurement. Different types of thermoluminescent dosimetry dosimeters were developed to measure dose in the range of 1–10kGy.