Sanjeev K. Sharma

Y-doped zinc oxide (YZO) nanoflowers, microstructural analysis and test their antibacterial activity.

Self-assembled 3D flower-like yttrium-doped zinc oxide (YZO) microstructures composed of nanorods were prepared by hydrothermal-precipitation, and tested their antibacterial activity. The morphological, structural, and compositional properties of YZO nanoflowers were characterized by various techniques, which confirmed a well-crystallized wurtzite hexagonal phase. X-ray photoelectron spectroscopy (XPS) of YZO nanopowder showed the 3d core level spectra of yttrium (Y), which formed by two components at about 158.2 eV (3d5/2) and 160.4 eV (3d3/2). The antibacterial activity of YZO nanoflowers were investigated using both gram-positive and gram-negative microorganisms. Enhancement in antibacterial activity was observed by the incorporation of yttrium (Y: 2 at.%) of nanorod-based-flowers because of increased surface area. The prepared YZO nanocomposite showed potential as an antibacterial agent with applications in controlling the spread of infections and also the ability of fast antibacterial activity which can hinder the re-emergence of infection.

Highly stable blue-emission in semipolar (11-22) InGaN/GaN multi-quantum well light-emitting diode

We demonstrate highly stable blue-emission on the semipolar (11-22) InGaN/GaN multi-quantum well light-emitting diode (LED) that has been prepared by the direct lateral-overgrowth method. The LED clearly displays bright blue-emission (λ ∼ 441 nm) with the reduced quantum-confined Stark effect. The variation of the emission-wavelength takes place only at the small injection-current range (<10 mA), and the net variation is less than 1.3 nm for wide driving-current ranges (5–100 mA). After the stabilization of light emission, the optical power is linearly increased with increasing the driving-current (1–1.8 mW). Additionally, the LED exhibits the stable light-polarization characteristics.

ZnO decorated with organic nanoparticles based sensor for the ratiometric selective determination of mercury ions

ZnO nanoparticles decorated with organic receptor 1 (R1) have been prepared and the resultant compound (N1) was investigated for its metal recognition ability. N1 was found to be selective for mercury ions (Hg2+) in a DMSO/water mixture in a ratio of 7 : 3 and possessed no interference from any of the potential interferent metal ions. The crystal size and morphology of ZnO is characterized using various spectroscopic and diffraction techniques like scanning electron microscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), etc. Surface decoration of the ZnO with receptor 1 is confirmed using NMR spectroscopy. On successive additions of Hg2+ ions, the fluoresence intensity of the compound was quenched at 427 nm with enhancement of the peak at 482 nm, which led to ratiometric sensor development for the recognition of mercury ions having a detection limit of 0.19 nM. The prepared receptor was also tested for real sample application by preparing a known concentration of Hg2+ solution and it was found to respond well with an accuracy more than 90%.

Some Results of Remote Sensing of Atmospheric Refractivity Near the Ground Using Laser Beam Scintillations

An experimental set-up developed for the measurement of path-averaged atmospheric refractive index structure parameter (C2n) is described followed by a brief summary of the theory involved in the generation and amplification of refractive index inhomogeneities. The results of the experiments conducted in the surface layer using a Helium-Neon laser source over an optical path length of 61.5 m at a height of 1.1 m above uniform surface are presented. The observed C2n ranges from 0.97 × 10−12 to 1.3 × 10−14 m−2/3. The diurnal variation of C2n shows rapid increase during morning hours, peaking around noon and slow decrease during evening hours. The observed relationship between the variations of C2n and temperature is explained and further studies to support and extend the present findings are indicated.

An Optical Scintillometer for Simultaneous Measurements of Atmospheric C2n and Winds

Laser scintillations produced due to the inhomogeneities present in the atmosphere can be used for measuring refractive index structure parameter (Cn 2) as well as wind velocity. The present paper deals with the description of an optical scintillometer developed at the Indian Institute of Tropical Meteorology (IITM), Pune, India for simultaneous measurements of path-averaged Cn 2 and crosswinds. Different evaluation techniques and their relative merits for wind estimation from optical scintillometer observations are discussed. The results show good agreement between the scintillometer evaluated winds and the winds measured simultaneously by using propeller anemometer at the same location. In addition, this paper explains the effect of Cn 2 and wind fluctuations along the pathlength on the derived wind information from scintillometer observations.