The density of states and quantum capacitance of pure and doped Nb₂N and Nb₄N₃ single-layer and multi-layer bulk structures are investigated using density functional theory calculations. The calculated value of quantum capacitance is quite high for pristine Nb₂N and decent for Nb₄N₃ structures. However for cobalt-doped unpolarized structures, significant increase in quantum capacitance at Fermi level is observed in the case of Nb₄N₃ as compared to minor increase in case of Nb₂N. These results show that pristine and doped Nb₂N and Nb₄N₃ can be preferred over graphene as the electrode material for supercapacitors. The spin and temperature dependences of quantum capacitance for these structures are also investigated.

The flower-like ZnO nanorods have been successfully synthesized by a surfactant-assisted hydrothermal method. The nanostructures formed by ZnO nanorods were synthesized and deposited without seeding in glass flask by a hexamethylenetetramine (HMTA)-assisted hydrothermal method at low temperature with NaOH as surfactant and catalyst. The synthesized ZnO flowers comprise of several spike structures that have hexagonal cross section and taper toward the end. The structures are investigated using X-ray diffraction, scanning electron microscope and transmission microscope. The optical properties are studied with UV-VIS, FTIR, and Raman spectroscopy. The process of synthesis is simple and highly reproducible. The synthesized flower-like structures are suitable for use as sensors applications.

The parametric drift wave instabilities in a magnetically confined plasma such as electron cyclotron resonance (ECR) ion source, have been observed by Fourier transform of beam current oscillations using a spectrum analyzer. The beam current oscillations are found to have frequencies in the range from few tens of Hz to few hundreds of kHz and are tunable over a wide range by varying the ECR parameters. These oscillations are attributed to drift waves and found to have sub-structural frequencies symmetrically on either side. They exist for every ion beam extracted from the ECR ion source. These observations made with oxygen plasma have been validated with xenon plasma and theoretically justified as drift waves by the local slab model for magnetically confined plasmas. Such drift waves may be used as a diagnostic tool to improve the performance of ECR ion source.

Background: Tin oxide nanoparticles also show good photocatalytic efficiency due to wide bandgap and high recombination rates of photo-generated electron-hole pairs. Being non-toxic and chemically stable, the tin oxide nanoparticles are used as dynamic photo-catalyst for the degradation. Tin oxide nanocrystals suitable for charge storage devices are synthesized using the coprecipitation technique.Objectives: Synthesis of Tin oxide nanocrystals by using the co-precipitation method for photocatalytic activity under sunlight that can be used for photo-degradation. The method of synthesis and characterization are also discussed.Materials and Methods: The nanocrystals are prepared by co-precipitation method using stannic chloride and sodium carbonate. Sodium carbonate is added under constant stirring drop by drop for 90 minutes. The solution is settled for 4 hours. The precipitates are first washed using de-ionized water and then with ethyl alcohol. The dried powder of nanocrystals is then calcinated at 500°C for one hour in a muffle furnace. The structural, morphological, optical, and electrical characterization of these synthesized crystals is done using (XRD), (FESEM), (TEM), (UV-Visible), (FT-Raman), Zeta potential, and dielectric constant measurements.Results and Discussion: The sizes of synthesized nanocrystals vary from 25 nm to 100 nm and are found to be optically transparent. The dielectric constant of nanocrystals is measured in the frequency range of 100Hz-1MHz and it can be seen that it declines from ~2000 at a frequency of 100Hz to ~30 at 1MHz. However, this decline in dielectric constant with frequency can be explained well on the basis of strong space charge polarization and rotational direction polarization processes in nanostructures. In the high-frequency regions, these processes cannot follow the electrical field frequency variations that result in the rapid decrease of dielectric constant.Photocatalytic Activity:: The photocatalytic activity of the particles under sunlight is also investigated, which shows that the crystals show degradation of the methylene blue dye under sunlight irradiation.Theoretical investigations with DFT: The bandgap of the particles was also calculated from the UV-VIS spectra, which was found to be ~3.6 eV and this experimentally observed value of bandgap matches with that calculated theoretically from Density Functional Theory (DFT) using Local Density Approximation (LDA).Conclusion: The method of synthesis reported in the present paper is scalable and can be used for the commercial synthesis of SnO2 nano-crystals for electrodes and energy storage devices.