Electronic and magnetic structure investigation of vanadium doped ZnO nanostructure

Bhardwaj, Richa,Singh, Jitendra Pal,Chae, Keun Hwa,Goyal, Navdeep,Gautam, Sanjeev Elsevier 2018 Vacuum Vol.158 No.-

<P><B>Abstract</B></P> <P>In the present work, vanadium doped ZnO nanostructure, Zn<SUB>1-<I>x</I> </SUB>V<SUB> <I>x</I> </SUB>O (x = 0.00, 0.01, 0.02, 0.03) have been synthesized using sol-gel route. Rietveld refined X-ray diffraction confirms the single wurtzite phase for all the prepared samples with crystallite size ranging from 20 to 40 nm. UV-Diffuse reflectance spectroscopy shows the decrease in band gap energy from 3.20 to 3.17 eV on V doping and and Photoluminescence (PL) measurements has a strong visible emission region in the range 500–700 nm. PL broad peak in the visible region is further deconvoluted to study the defect states in the V:ZnO system. V doped ZnO nanostructure shows the room temperature ferromagnetism measured through Vibrating Sample Magnetometer hysteresis curve. The magnetic moment ( <SUB> μ B </SUB> ) is found to vary from 0.012 to 0.018 <SUB> μ B </SUB> per V-atom as x changes from 0.01 to 0.03 in Zn<SUB>1-<I>x</I> </SUB>V<SUB> <I>x</I> </SUB>O matrix. Magnetic structure properties are correlated with electronic transitions at different atomic levels using near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy. NEXAFS spectral features at O<I>K-</I>, V/Zn <SUB> L 3,2 </SUB> <I>-</I> edge reveals the hybridization of V(3<I>d</I>)-O(2<I>p</I>) orbitals and absence of V-metallic clusters in V:ZnO system. These investigations further envisage the existence of +5 state of vanadium in Zn<SUB>1-<I>x</I> </SUB>V<SUB> <I>x</I> </SUB>O nanostructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Zn<SUB>1−<I>x</I> </SUB>V<SUB> <I>x</I> </SUB>O (x = 0.00, 0.01, 0.02, 0.03) synthesis by sol-gel route with crystallite size 20–30 nm. </LI> <LI> PL spectra is deconvoluted that shows the presence of vacancies in the V:ZnO system. </LI> <LI> The hybridized electronic structure of V:ZnO is investigated through NEXAFS. </LI> <LI> Samples show RTFM with magnetic moment varying from 0.012 to 0.018 μ<I>B</I>/V atom for x = 0.01 to 0.03. </LI> <LI> The magnetic structure is discussed through BMP exchange interactions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Role of low energy transition metal ions in interface formation in ZnO thin films and their effect on magnetic properties for spintronic applications

Bhardwaj, Richa,Kaur, Baljeet,Singh, Jitendra Pal,Kumar, Manish,Lee, H.H.,Kumar, Parmod,Meena, R.C.,Asokan, K.,Hwa Chae, Keun,Goyal, Navdeep,Gautam, Sanjeev Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.479 No.-

<P><B>Abstract</B></P> <P>In this study, X-ZnO/ZnO/Si(100) (X = Co, Ni and Cu) bilayer structure is fabricated using low energy ion implantation technique. Five different fluences 1 × 10<SUP>15</SUP>, 5 × 10<SUP>15</SUP>, 1 × 10<SUP>16</SUP>, 2.5 × 10<SUP>16</SUP> and 5 × 10<SUP>16</SUP> ions/cm<SUP>2</SUP> with 100 keV ion-beam energy were selected in order to implant the ions up to the depth of ≈44 nm as calculated through Stopping Range of Ion in Matter and Transport Range of Ions in Matter software. Structural modification was investigated by high resolution X-ray diffraction measurements in ZnO bilayer system. An observed systematic 2<I>θ</I> shift in (002) peak with increasing fluence implies increased density of implanted metal ions in ZnO matrix revealing the substitution of implanted ion at Zn-site. The mechanism of bilayer formation by ion-beam implantation technique has been discussed for metal-ions by investigating their interface properties. Atomic force microscopy reveals the morphological modification after ion implantation. Near-edge X-ray absorption fine-structure (NEXAFS) measurements at metal <I>K</I>- and <I>L</I> <SUB>3,2</SUB>-edges have been used to investigate the nature of implanted ions in terms of their valance state and local electronic environment. Further, O <I>K</I>-edge NEXAFS measurement for Ni-ZnO/ZnO/Si bilayer is highly sensitive to incident beam angles whereas no spectral change is seen for Zn <I>L</I>-edge measurements. The magnetic measurements were performed via vibrating sample magnetometer that showed the films are ferromagnetic at room temperature. The origin of ferromagnetism has been understood through defect mediated bound magnetic polaron model. Further, perpendicular magnetic anisotropy is also observed for Ni-ZnO/ZnO/Si bilayer structure at room temperature, which is correlated with the angle dependent O K-edge NEXAFS measurements. Fabrication of ZnO bilayer via ion implantation and investigation of above properties may prove useful in spin related and optoelectronic applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Observance of RTFM in metal ion-implanted Ni-ZnO/ZnO/Si bilayer </LI> <LI> HRXRD and NEXAFS measurements confirms the wurtzite phase and Zn<SUP>2+</SUP> substitution in ZnO matrix. </LI> <LI> Angle dependent NEXAFS measurements provides the evidence of observed PMA. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>Mechanism of ion beam interaction X (X = Co, Ni and Cu) with ZnO lattice forming X-ZnO/ZnO/Si(100) bilayer structure. Films were implanted using a multi cathode source of negative-ions by cesium sputtering (MC-SNICS) and with the increasing ion flux, X can undergo one of two mechanisms of either substituting the Zn-site or occupy interstitial position in ZnO matrix. Angle dependent O K-edge NEXAFS measurements provides the evidence of perpendicular magnetic anisotropy in ZnO bilayer. </P> <P>[DISPLAY OMISSION]</P>

Biosequestration, Transformation, and Volatilization of Mercury by Lysinibacillus fusiformis Isolated from Industrial Effluent

( Gupta Saurabh ),( Richa Goyal ),( Jashan Nirwan ),( Swaranjit Singh Cameotra ),( Nagaraja Tejoprakash ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.5

In the present study, an efficient mercury-tolerant bacterial strain (RS-5) was isolated from heavy-metalcontaminated industrial effluent. Under shake flask conditions, 97% of the supplemented mercuric chloride was sequestered by the biomass of RS-5 grown in a tryptone soy broth. The sequestered mercuric ions were transformed inside the bacterial cells, as an XRD analysis of the biomass confirmed the formation of mercurous chloride, which is only feasible following the reaction of the elemental mercury and the residual mercuric chloride present within the cells. Besides the sequestration and intracellular transformation, a significant fraction of the mercury (63%) was also volatilized. The 16S rRNA gene sequence of RS-5 revealed its phylogenetic relationship with the family Bacillaceae, and a 98% homology with Lysinibacillus fusiformis, a Gram-positive bacterium with swollen sporangia. This is the first observation of the sequestration and volatilization of mercuric ions by Lysinibacillus sp.

Quercetin Protects Against Acute Immobilization Stress-Induced Behaviors and Biochemical Alterations in Mice

Anil Kumar,Richa Goyal 한국식품영양과학회 2008 Journal of medicinal food Vol.11 No.3

Oxidative stress is a major contributor to the alterations of various pathological conditions, including neurodegenerative and neuropsychiatric problems. Antioxidative flavonoids, ubiquitously included in vegetables, fruits, and teas, are expected to prevent degenerative diseases. Recently, flavonoids have been characterized as neuroprotectants in the treatment of various neurological disorders. The present study was designed to investigate protective effects of quercetin, a bioflavonoid, against acute immobilization-induced behavioral and biochemical alterations in mice. Mice were immobilized for a period of 6 hours. Quercetin (20 and 40 mg/kg, i.p.) was administered 30 minutes before subjecting the animals to acute stress. Behavioral tests (mirror chamber, actophotometer, and tail flick test) and biochemical analysis (malondialdehyde, reduced glutathione, catalase, nitrite, and protein levels) were subsequently performed. Acute immobilization stress for a period of 6 hours caused severe anxiety, analgesia, and impaired motor activity in mice. Biochemical analyses revealed an increase in malondialdehyde and nitrite levels as well as partial depletion of reduced glutathione and catalase activity in immobilization-stressed brain. Behavioral and biochemical parameters were significantly altered as compared to naive mice. Pretreatment with quercetin (20 and 40 mg/kg, i.p.) significantly reversed immobilized stress-induced anxiety and analgesia and reduced locomotor activity. Biochemically, quercetin treatment attenuated malondialdehyde accumulation and nitrite activity and restored the depleted reduced glutathione and catalase activity. Neuroprotective effects of quercetin were significantly improved as compared to control (immobilized stressed) animals. Results suggest that neuroprotective properties of quercetin can be used in the treatment and management of stress and related disorders.