Vikash Chandra Petwal

Optical properties and ionic conductivity studies of an 8 MeV electron beam irradiated poly(vinylidene fluoride-co-hexafluoropropylene)/LiClO4 electrolyte film for opto-electronic applications

The influence of 8 MeV energy electron beam (EB) irradiation on optical properties and ionic conductivity of PVDF–HFP/LiClO4 (90 : 10 PHL10) electrolyte film with 40, 80 and 120 kGy doses. The FT-IR results show that CO bond stretching at 1654 cm−1 is due to the degradation of polymer chains and the CH2 bond wagging intensity at 1405 cm−1 corresponds to C–H bond scissioning in the 120 kGy dose irradiated film. 1H and 13C NMR spectroscopy was performed and the 13C NMR spectra confirm the effect of EB irradiation of the PHL10 polymer electrolyte by sharpening and splitting the spectral lines with increasing EB dose and revealing a new spectral line at 162.80 ppm with a 120 kGy EB dose. The size and shape of the porous morphology was drastically changed, becoming deeply porous with a visible inner hollow shaped structure, suggesting increased amorphous character upon irradiation. The absorption band of the unirradiated film observed at 202 nm in the ultraviolet region is shifted to 274 nm after irradiation due to inter band transition of electrons from the valence band to the conduction band and the optical band gap decreasing from 3.49 eV in the unirradiated film to 2.64 eV with a 120 kGy EB dose. Segmental motion in the polymer matrix leads to a decrease in the local viscosity by increasing the mobility of ions upon irradiation. Nyquist plots show semicircles at high frequency due to Li-ion migration through the porous surface of the electrolyte film. A maximum ionic conductivity of 8.28 × 10−4 S cm−1 was obtained with a 120 kGy EB dose and the observed cyclic voltammetry of the irradiated polymer electrolyte suggests it is electrochemically stable.

Enhanced red luminescence and improved crystallinity in NaEu(WO4)2 phosphors: an electron beam irradiation study

A sodium Europium Double Tungstate (NaEuW) red phosphor was synthesized by a facile hydrothermal method and characterized by powder XRD, FTIR, UV-DRS, FESEM and photoluminescent measurements. The influence of different doses of high energy electron beam (EB) irradiation on the structural, morphology and fluorescence properties of NaEuW crystallizing in the I41/a space group was investigated for the first time in comparison with non-irradiated NaEuW. Different doses of high energy EB irradiation resulted in a systematic shift in the diffraction peaks towards lower 2θ, indicating unit cell volume expansion. Interestingly, phase purity was retained even at a higher EB dose, signifying the structural stability of the NaEuW red phosphor. An insight into the FESEM micrographs shows improved crystallinity and agglomeration upon EB irradiation. The resultant NaEuW phosphor emits bright red color under UV excitation of wavelength 396 nm and the intensity was significantly varied for different doses of EB irradiation. At an optimum dose of 20 KGy, a very high color purity was obtained from the calculated CIE-X and Y of the CIE chromaticity diagram of the irradiated NaEuW samples. Additionally, the CIE-X and CIE-Y coordinates of the irradiated material are observed to be closer to the commercially available red phosphor Y2O3S:Eu3+. Hence, this work could present a potentially new strategy to improve the fluorescence properties of phase pure NaEuW via EB irradiation.

A novel approach for tailoring structural, morphological, photoluminescence and nonlinear optical features in spray coated Cu:ZnO nanostructures via e-beam

In this article, we present the investigations on modification of structural, morphological, and optical properties of spray coated Cu doped ZnO (CZO) thin films by electron beam. Glancing angle X-ray diffraction reveal polycrystalline nature of the CZO films and indexed to hexagonal wurtzite structure. Notable reduction in FWHM values upon e-beam treatment is attributed to the irradiation induced reorientation of grains. The Gaussian deconvolution at ambient temperature photoluminescence (RTPL) spectra demonstrates broad visible bands for all the spectra which is caused by presence of various structural and native defects like oxygen, zinc, zinc interstitials and antisite oxygen defects. The increase of the electron beam dosage from 0 kGy to 20 kGy results in the decrement of the PL intensity endorsing the fact that e-beam irradiation can act as a luminescent activators which can effectively regulates the luminescence behavior of CZO thin films. The Raman spectra of CZO show a successive reduction in the intensity of Raman peaks especially for the dominant peak around ∼439 cm−1 upon e-beam treatment. Increase in localized defect states results in decreasing energy band gap magnitudes for the nanostructures. The third order nonlinear optical properties of the films have been studied using Z-scan and laser stimulated third harmonic generation technique (LITHG). Enhancement of third harmonic frequency conversion efficiency of CZO nanostructures is caused by electron beam induced photoexcitation and relaxation processes. The transition properties of saturable absorption (SA) and reverse saturable absorption (RSA) mechanism upon e-beam irradiation for the CZO films can be used for production of optical limiters, all-optical logic gates, optical triggers, mode storage and fast optical switchers etc.

Electron beam irradiation revealed genetic differences in radio-sensitivity and generated mutants in groundnut (Arachis hypogaea L.)

Electron beam accelerators are being used for many industrial applications including food and agriculture. A 10MeV linear accelerator facility was standardized for low dose application 0.1-1 kGy) in pulse mode using unscanned scattered beam for irradiation of groundnut seeds for mutation breeding. Using this facility, 50% growth reduction (GR50) dose was standardized in five groundnut genotypes. There were significant differences for radio-sensitivity among these genotypes. Seed mutagenesis of two groundnut genotypes, TG 26 and TG 68 with electron beam has generated one large seeded and four high yielding mutants in preliminary field trials.

A study on the microstructural parameters of 550 keV electron irradiated Lexan polymer films

Lexan polymer films irradiated with 550 keV Electron Beam (EB) were characterized using Wide Angle Xray Scattering (WAXS) data to study the microstructural parameters. The crystal imperfection parameters like crystal size , lattice strain (g in %) and enthalpy (α☆) have been determined by Line Profile Analysis (LPA) using Fourier method of Warren.