Ankush Vij

Synthesis and luminescence studies of Ce doped SrS nanostructures

Cerium doped strontium sulfide nanostructures were synthesized by the solid state diffusion method in the presence of sodium thiosulfate. XRD confirmed the single phase rocksalt structure of the synthesized samples and the average grain size using the Debye–Scherrer relation is calculated to be 55 nm. TEM micrographs reveal the agglomerated whisker-like morphology with a diametre of 55–60 nm and length of several nanometres, which is in close agreement with XRD results. The effect of dopant concentration on photoluminescence (PL) intensity has been studied. PL emission for SrS : Ce (0.5 mol%) is at 481 nm with a shoulder at 530 nm at an excitation wavelength of 430 nm, which is attributed to the transitions from the 5d state to the 4f (2f7/2, 2f5/2) states of Ce3+. Ultraviolet and visible (UV–VIS) spectroscopy shows band-to-band absorption at 273 nm (4.54 eV), which is blue shifted in comparison to the band gap of bulk SrS (4.2 eV), which may be due to quantum confinement. The effect of high energy ball milling on the grain size and PL intensity has also been investigated for the first time in the doped SrS system. The PL emission wavelength is blue shifted by 3 nm but the emission intensity decreases unexpectedly as the milling time increases, although there is a reduction in size which is evident from XRD peak broadening of the milled samples. This may be ascribed to surface defects generated by ball milling which act as killing centres, quenching the PL.

Nanostructured Boron Nitride With High Water Dispersibility For Boron Neutron Capture Therapy

Highly water dispersible boron based compounds are innovative and advanced materials which can be used in Boron Neutron Capture Therapy for cancer treatment (BNCT). Present study deals with the synthesis of highly water dispersible nanostructured Boron Nitride (BN). Unique and relatively low temperature synthesis route is the soul of present study. The morphological examinations (Scanning/transmission electron microscopy) of synthesized nanostructures showed that they are in transient phase from two dimensional hexagonal sheets to nanotubes. It is also supported by dual energy band gap of these materials calculated from UV- visible spectrum of the material. The theoretically calculated band gap also supports the same (calculated by virtual nano lab Software). X-ray diffraction (XRD) analysis shows that the synthesized material has deformed structure which is further supported by Raman spectroscopy. The structural aspect of high water disperse ability of BN is also studied. The ultra-high disperse ability which is a result of structural deformation make these nanostructures very useful in BNCT. Cytotoxicity studies on various cell lines (Hela(cervical cancer), human embryonic kidney (HEK-293) and human breast adenocarcinoma (MCF-7)) show that the synthesized nanostructures can be used for BNCT.

120 MeV Ag9+ Ions Induced Ionoluminescence of SrS:Ce

We report the ionoluminescence (IL) of SrS:Ce subjected to different fluences of 120 MeV Ag9+ ion beam. IL spectrum comprises of a main peak at 487 nm with a shoulder at 535 nm, which were identified on the account of transitions from 5d state to 4f (2F5/2, 2F7/2) states of Ce3+ in SrS. The bright ionoluminescent behaviour of SrS:Ce may be exploited in the applications of this material as a scintillation detector for swift heavy ions.We report the ionoluminescence (IL) of SrS:Ce subjected to different fluences of 120 MeV Ag9+ ion beam. IL spectrum comprises of a main peak at 487 nm with a shoulder at 535 nm, which were identified on the account of transitions from 5d state to 4f (2F5/2, 2F7/2) states of Ce3+ in SrS. The bright ionoluminescent behaviour of SrS:Ce may be exploited in the applications of this material as a scintillation detector for swift heavy ions.

Thermoluminescence studies of BaS:Bi nanophosphors exposed to UV radiation

Bismuth-doped barium sulfide nanocrystallities have been prepared and characterized by XRD and TEM. Thermoluminescnce studies of these samples after exposure to UV radiation have been carried out. The thermoluminescence (TL) glow curve of the phosphors has been found to have a simple structure with a single peak at 405 K, while in their bulk counterparts, this peak was reported at 333 K. The kinetic parameters, namely activation energy (E), order of kinetics (b) and frequency factor (s) of BaS:Bi (0.4 mol%) sample has been determined using Chens method. The effect of different dopant concentrations on the TL glow curve was studied and the optimum concentration of Bi found to be 0.4 mole%. The deconvolution of the curve was established using the glow curve deconvolution function suggested by Kitis. The effect of different heating rates and different dose amounts has also been discussed.

Effect of oxygen pressure on the structural and optical properties of ZnO/Si(100) thin films

ZnO thin films (thickness ∼ 400 nm) were prepared at different oxygen content (O2) by radio frequency (rf) sputtering method. Crystal structure and optical properties of these films were investigated by x-ray diffraction (XRD) and UV-VIS-NIR spectrophotometer, respectively. XRD measurement suggests that all films have hexagonal wurtzite structure. The transparency in the visible region of all the film is more than 90%. The optical absorption edge was described using the direct transition model proposed by Tauc and the optical band gap was calculated from the absorption coefficient by Tauc’s extrapolation procedure. The value of optical band gap was decreased with increase in the O2 content; due to Burstein-Moss shift.

Structural and magnetic properties of Fe doped CeO2 thin films

Pure and Ce0.95Fe0.05O2 thin films have been fabricated on LaAlO3 (100) substrate using pulsed laser deposition techniques at 200mTorr oxygen partial pressure and then characterized by various techniques viz. X-ray diffraction, atomic force microscopy, NEXAFS, and dc- magnetization measurements to explore the structural and magnetic properties of pure and Fe doped CeO2 thin films. The XRD patterns indicate that pure and Ce0.95Fe0.05O2 films have single phase polycrystalline behavior. The surface roughness measured using AFM microscopy found to decrease with Fe doping and revealed that both the films are nanocrystalline. The electronic structure measured at Fe L3,2 edge infer that Fe-ions in mixed valence states (Fe3+ and Fe2+) in Fe doped CeO2film. DC-magnetization measurements showed that pure and Fe doped CeO2 films have ferromagnetic ordering at room temperature.Pure and Ce0.95Fe0.05O2 thin films have been fabricated on LaAlO3 (100) substrate using pulsed laser deposition techniques at 200mTorr oxygen partial pressure and then characterized by various techniques viz. X-ray diffraction, atomic force microscopy, NEXAFS, and dc- magnetization measurements to explore the structural and magnetic properties of pure and Fe doped CeO2 thin films. The XRD patterns indicate that pure and Ce0.95Fe0.05O2 films have single phase polycrystalline behavior. The surface roughness measured using AFM microscopy found to decrease with Fe doping and revealed that both the films are nanocrystalline. The electronic structure measured at Fe L3,2 edge infer that Fe-ions in mixed valence states (Fe3+ and Fe2+) in Fe doped CeO2film. DC-magnetization measurements showed that pure and Fe doped CeO2 films have ferromagnetic ordering at room temperature.

Near-edge X-ray absorption fine structure spectroscopy and structural properties of Ni-doped CeO2 nanoparticles

ABSTRACT Ni-doped CeO2 nanoparticles were prepared by using the co-precipitation method. The prepared nanoparticles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The XRD results infer that Ni-doped CeO2 nanoparticles have single phase nature similar to that of pure CeO2 nanoparticles. We have calculated lattice parameters using Powder-X software, particle size using Scherer’s formula and strain using the Williamson-Hall method for all the synthesized samples. We have observed a systematic decrease in the lattice parameters, particle size and strain with an increase in Ni doping in CeO2. The FE-SEM micrographs also confirm that Ni-doped CeO2 have nanocrystalline behavior and particles are spherical shaped. From the Raman spectra, it is observed that the intensity of classical CeO2 vibration modes first increases then decreases with Ni doping. The NEXAFS spectra measured at Ce M4,5 and Ni L3,2 edges clearly indicate that Ce ions are in the +4 valence state and Ni ions are in the +2 valence state.

Effect of annealing on the structure of chemically synthesized SnO2 nanoparticles

Tin oxide (SnO2) nanoparticles have been synthesized by co-precipitation method. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) and Raman spectroscopy. XRD analysis confirmed the single phase formation of SnO2 nanoparticles. The Raman shifts showed the typical feature of the tetragonal phase of the as-synthesized SnO2 nanoparticles. At low annealing temperature, a strong distortion of the crystalline structure and high degree of agglomeration was observed. It is concluded that the crystallinity of SnO2 nanoparticles improves with the increase in annealing temperature.

Structural and spectroscopic study of mechanically synthesized SnO2 nanostructures

We report the single step synthesis of SnO2 nanostructures using high energy mechanical attrition method. X-ray diffraction (XRD) pattern reveals the single phase rutile structure with appreciable broadening of diffraction peaks, which is a signature of nanostructure formation. The average crystallite size of SnO2 nanostructures has been calculated to be ~15 nm. The micro-Raman study reveals the shifting of A1g Raman mode towards lower wave number, which is correlated with the nanostructure formation.

TL Kinetics Study of LiF nanophosphors for High Exposures of Gamma-rays

We report the thermoluminescence (TL) kinetics study of LiF nanophosphors synthesized by chemical co-precipitation at 8.00 pH and exposed to high gamma dose. XRD and TEM studies confirm the formation of single phase LiF nanophosphors. TL properties of LiF phosphors irradiated with gamma rays at different doses of 100 Gy – 70 KGy shows a major peak around 395 K in addition to other low intensity peaks. The major peak in the TL glow curve is almost resolved from other peaks, which has been analyzed using Chen’s peak shape method to determine the TL kinetic parameters. TL intensity almost increases linearly with gamma dose, however TL glow curve shift slightly to lower temperature values as a function of gamma exposure.