Ion induced controlled modifications in structural and optical properties of indium oxide thin films – studies with 25‐keV Co− and N+ beam implantations

Two sets of indium oxide thin films (~150 nm) grown on quartz substrates using thermal evaporation technique were processed separately with 25‐keV Co^? and N⁺ ions with several fluences ranging from 1.0 × 10¹⁵ to 1.0 × 10¹⁶ ions/cm². The pristine and the ion implanted films were characterized by Rutherford backscattering spectroscopy (RBS), X‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–Vis spectrometry. The RBS spectra reveal signature of only cobalt and nitrogen in accordance to their fluences confirming absence of any contamination arising due to ion implantation. An increase in the average crystallite size (from 13.7 to 15.3 nm) of Co^? ions implanted films was confirmed by XRD. On the other hand, the films implanted with N⁺ ions showed a decrease in the average crystallite size from 20.1 to 13.7 nm. The XRD results were further verified by SEM micrographs. As seen in AFM images, the RMS surface roughness of the samples processed by both ion beams was found to decrease a bit (29.4 to 22.2 nm in Co^? implanted samples and 24.2 to 23.3 nm in N⁺ implanted samples) with increasing fluence. The Tauc's plot deduced from UV–visible spectroscopy showed that the band gap decreases from 3.54 to 3.27 eV in Co^? implanted films and increases from 3.38 to 3.58 eV for films implanted with N⁺ ions. The experimental results suggest that the modifications in structural and optical properties of indium oxide films can be controlled by optimizing the implantation conditions. Copyright © 2017 John Wiley & Sons, Ltd.     

50 keV H+ ion beam irradiation of Al doped ZnO thin films: Studies of radiation stability for device applications

Thin films of Al doped ZnO (Al:ZnO) were deposited on two substrates (Si and glass) at room temperature and 300°C using DC magnetron sputtering. These films were bombarded with 50 keV H⁺ beam at several fluences. The pristine and ion beam irradiated films were analysed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV‐Vis spectroscopy. The X‐ray diffraction analysis, Hall measurements, Raman and UV‐Vis spectroscopy confirm that the structural and transport properties of Al:ZnO films do not change substantially with beam irradiation at chosen fluences. However, in comparison to film deposited at room temperature, the Al:ZnO thin film deposited at 300°C shows increased transmittance (from 70% to approximately 90%) with ion beam irradiation at highest fluence. The studies of surface morphology by scanning electron microscopy reveal that the ion irradiation yields smoothening of the films, which also increases with ion fluences. The films deposited at elevated temperature are smoother than those deposited at room temperature. In the paper, we discuss the interaction of 50 keV H⁺ ions with Al:ZnO films in terms of radiation stability in devices.     

A new combination of cyclohexylhydrazine and IBX for oxidative generation of cyclohexyl free radical and related synthesis of parvaquone

The present paper demonstrates a single-step and straightforward synthesis of parvaquone through intermediacy of cyclohexyl radical generated from novel combination of cyclohexylhydrazine and o-iodoxybenzoic acid and subsequently trapped by 2-hydroxy-1,4-naphthoquinone. Formation of cyclohexyl free radical using this new combination was reaffirmed by cyclohexylation of readily available 2-amino-1,4-naphthoquinone.     

Microwave-enhanced rhodium-catalyzed conjugate-addition of aryl boronic acids to unprotected maleimides

Various boronic acids were treated with a rhodium (I) catalyst enabling their 1,4-conjugate addition to unprotected maleimide. The scope of the reaction was explored to include both electron-rich and electron poor boronic acids. These reactions were also performed in the microwave resulting in reduced reaction times and improved efficiencies. Additionally, substrates that were recalcitrant under conventional conditions were successfully reacted under microwave conditions. The reaction worked satisfactorily with boronic acids having a free OH or NH group.     

Medium energy,heavy and inert ion irradiation of metallic thin films: studies of surface nano‐structuring and metal burrowing

In context to the ion induced surface nanostructuring of metals and their burrowing in the substrates, we report the influence of Xe and Kr ion‐irradiation on Pt:Si and Ag:Si thin films of ~5‐nm thickness. For the irradiation of thin films, several ion energies (275 and 350 keV of Kr; 450 and 700 keV of Xe) were chosen to maintain a constant ratio of the nuclear energy loss to the electronic energy loss (S_n/S_e) in Pt and Ag films (five in present studies). The ion‐fluence was varied from 1.0 × 10¹⁵ to 1.0 × 10¹⁷ ions/cm². The irradiated films were characterized using Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images show ion beam induced systematic surface nano‐structuring of thin films. The surface nano‐structures evolve with the ion fluence. The RBS spectra show fluence dependent burrowing of Pt and Ag in Si upon the irradiation of both ion beams. At highest fluence, the depth of metal burrowing in Si for all irradiation conditions remains almost constant confirming the synergistic effect of energy losses by the ion beams. The RBS analysis also shows quite large sputtering of thin films bombarded with ion beams. The sputtering yield varied from 54% to 62% by irradiating the thin films with Xe and Kr ions of chosen energies at highest ion fluence. In the paper, we present the experimental results and discuss the ion induced surface nano‐structuring of Pt and Ag and their burrowing in Si. Copyright © 2016 John Wiley & Sons, Ltd.     

Duality via halfspaces

This note shows that half spaces play a very special role in the development of duality. In addition to the minimum norm duality, the duality in linear programming, and Wolfe's and Johri's formulations in nonlinear programming can all be derived via half spaces by following an identical five step procedure.     

Stabilization of betatron tune in Indus-2 storage ring

Indus-2 is a synchrotron radiation source that is operational at RRCAT, Indore, India. It is essentially pertinent in any synchrotron radiation facility to store the electron beam without beam loss. During the day to day operation of Indus-2 storage ring, difficulty was being faced in accumulating higher beam current. After examination, it was found that the working point was shifting from its desired value during accumulation. For smooth beam accumulation, a fixed desired tune in both horizontal and vertical plane plays a significant role in avoiding beam loss via the resonance process. This required a betatron tune feedback system to be put in the storage ring. After putting ON this feedback, the beam accumulation was smooth. The details of this feedback and its working principle are described in this paper.     

Modification in the transport and morphological properties of solid polymer electrolyte system by low-energy ion irradiation

The poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) systems consisting of NaBr as a dopant salt are prepared. The stable PEO:NaBr system with 3 wt% of NaBr was subjected to low-energy ion beam irradiation to bring in morphological modification. The irradiated samples are studied using complex impedance spectra to evaluate electrical conductivity and relaxation process in the system. The studies show an increase in conductivity by one order magnitude in the irradiated systems. The dielectric loss tangent (tanδ) curves show a single peak due to strong coupling of ion transport with segmental motion. The resultant relaxation time τ exhibits a continuous decrease indicating increase in segmental dynamics as a result of increased amorphous content in the system. The temperature-dependent studies also indicate that the irradiated systems are more disordered/amorphous compared to pure systems. This fact is further supported by XRD, by observing an increase in peak width associated with reduction in peak intensity. The Raman spectra also support the change in morphology of the system by the appearance of disordered-longitudinal acoustic mode band.     

An automated method for in vitro anticancer drug efficacy monitoring based on cell viability measurement using a portable photodiode array chip

An integrated circuit (IC) bipolar semiconductor photodiode array (PDA) microchip system coupled with light emitting diodes (LEDs) was used for rapid, automated cell viability measurements and high-throughput drug efficacy monitoring. Using the absorption property of trypan blue dye against the red light emitted by LEDs, we determined the effect of three anticancer drugs, viz., camptothecin (CAM), sodium salicylate (Na-Sal) and naringenin (Nar) on the cell viability of human promyelocytic leukemia cells (HL-60) and human embryonic kidney cells (HEK-293). Cell viabilities were measured based on the relative reduction in the photo responses of the photodiodes, covered with known concentration of trypan blue-stained cells. The developed method offers greater sensitivity and hence an excellent estimation of cell viability, but without all the hassle of conventional methods. Flow cytometric measurement and confocal microscopy were applied as complementary techniques for further validation of the results. The work presented here has important implications with regard to high-throughput measurement of optimal concentrations of different drugs against different cell lines in vitro.     

Synthesis of bis-indole carboxamides as G-quadruplex stabilizing and inducing ligands

The design and synthesis of a series of bis‐indole carboxamides with varying amine containing side chains as G‐quadruplex DNA stabilising small molecules are reported. Their interactions with quadruplexes have been evaluated by means of Förster resonance energy transfer (FRET) melting analysis, UV/Vis spectroscopy, circular dichroism spectroscopy and molecular modelling studies. FRET analysis indicates that these ligands exhibit significant selectivity for quadruplex over duplex DNA, and the position of the carboxamide side chains is of paramount importance in G‐quadruplex stabilisation. UV/Vis titration studies reveal that bis‐indole ligands bind tightly to quadruplexes and show a three‐ to fivefold preference for c‐kit2 over h‐telo quadruplex DNA. CD studies revealed that bis‐indole carboxamide with a central pyridine ring induces the formation of a single, antiparallel, conformation of the h‐telo quadruplex in the presence and absence of added salt. The chirality of h‐telo quadruplex was transferred to the achiral ligand (induced CD) and the formation of a preferred atropisomer was observed.