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Agarwal H, Alonso JA, Muñoz Á, Choudhary RJ, Srivastava ON, Shaz MA. Evolution from sinusoidal to collinear A-type antiferromagnetic spin-ordered magnetic phase transition in Tb 1-xPr xMnO 3solid solution. J Phys Condens Matter 2021; 33:265802. [PMID: 33906180 DOI: 10.1088/1361-648x/abfc14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/27/2021] [Indexed: 06/12/2023]
Abstract
The present study reports on the structural and magnetic phase transitions in Pr-doped polycrystalline Tb0.6Pr0.4MnO3, using high-resolution neutron powder diffraction (NPD) collected at SINQ spallation source, to emphasize the suppression of the sinusoidal magnetic structure of pure TbMnO3and the evolution to a collinear A-type antiferromagnetic ordering. The phase purity, Jahn-Teller distortion, and one-electron bandwidth for egorbital of Mn3+cation have been calculated for polycrystalline Tb0.6Pr0.4MnO3,in comparison to the parent materials TbMnO3and PrMnO3, through the Rietveld refinement study from x-ray diffraction data at room temperature, which reveals the GdFeO3type orthorhombic structure of Tb0.6Pr0.4MnO3havingPnmaspace group symmetry. The temperature-dependent zero field-cooled and field-cooled dc magnetization study at low temperature down to 5 K reveals a variation in the magnetic phase transition due to the effect of Pr3+substitution at the Tb3+site, which gives the signature of the antiferromagnetic nature of the sample, with a weak ferromagnetic component at low temperature-induced by an external magnetic field. The field-dependent magnetization study at low temperatures gives the weak coercivity having the order of 2 kOe, which is expected due to the canted-spin arrangement or ferromagnetic nature of Terbium ordering. The NPD data for Tb0.6Pr0.4MnO3confirms that the nuclear structure of the synthesized sample maintains its orthorhombic symmetry down to 1.5 K. Also, the magnetic structures have been solved at 50 K, 25 K, and 1.5 K through the NPD study, which shows an A-type antiferromagnetic spin arrangement having the magnetic space groupPn'ma'.
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Affiliation(s)
- Harshit Agarwal
- Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, 221005, India
| | - José Antonio Alonso
- Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049, Madrid, Spain
| | - Ángel Muñoz
- Departamento de Física Aplicada, EPS, Universidad Carlos III, Avenida Universidad 30, E-28911, Leganés-Madrid, Spain
| | - R J Choudhary
- UGC-DAE Consortium of Scientific Research, Indore, 452017, India
| | - O N Srivastava
- Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, 221005, India
| | - M A Shaz
- Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, 221005, India
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2
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Yadav TP, Woellner CF, Sharifi T, Sinha SK, Qu LL, Apte A, Mukhopadhyay NK, Srivastava ON, Vajtai R, Galvão DS, Tiwary CS, Ajayan PM. Extraction of Two-Dimensional Aluminum Alloys from Decagonal Quasicrystals. ACS Nano 2020; 14:7435-7443. [PMID: 32469491 DOI: 10.1021/acsnano.0c03081] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Atomically thin metallic alloys are receiving increased attention due to their prospective applications as interconnects/contacts in two-dimensional (2D) circuits, sensors, and catalysts, among others. In this work, we demonstrate an easily scalable technique for the synthesis of 2D metallic alloys from their 3D quasicrystalline precursors. We have used aluminum (Al)-based single-phase decagonal quasicrystal Al66Co17Cu17 alloy to extract the corresponding 2D alloy structure. The 2D layered Al alloy possesses 2-fold decagonal quasicrystalline symmetry and consists of two- or three-layer-thick sheets with a lateral dimension of microns. These 2D metallic layers were combined with the atomic layers of tungsten disulfide to form the stacked heterostructures, which is demonstrated to be a stable and efficient catalyst for hydrogen evolution reaction.
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Affiliation(s)
- Thakur Prasad Yadav
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | | | - Tiva Sharifi
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Shyam Kanta Sinha
- Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Lu-Lu Qu
- School of Chemistry and Materials Science, Jiangsu Normal University, Xuzhou 221116, People's Republic of China
| | - Amey Apte
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - N K Mukhopadhyay
- Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221 005, India
| | - O N Srivastava
- Department of Physics, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Robert Vajtai
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
| | - Douglas Soares Galvão
- Applied Physics Department and Center of Computational Engineering and Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Chandra Sekhar Tiwary
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
- Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Pulickel M Ajayan
- Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, United States
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Tripathi P, Talat M, Vishwakarma AK, Shaz MA, Kumar P, Gupta BK, Srivastava ON. A Facile Synthesis of Alkaline Electrolyte Based Graphene Sheets, Their Functionalization and Attachment of Some Drugs. J Nanosci Nanotechnol 2019; 19:5633-5643. [PMID: 30961718 DOI: 10.1166/jnn.2019.16543] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
High-quality graphene is highly enviable material due to its seminal role amongst several areas in modern technology including its role as nanocarrier for site selective drug grafting and delivery applications. Here, we report a facile, cost-effective and single-step method to produce high-quality graphene through customised electrochemical exfoliation of graphite anode in alkaline electrolyte medium. The quality of graphene sheets (GS) were investigated by Raman, TEM/HRTEM, AFM, and FTIR techniques. The high quality as well as excellent Π-Π stacking nature of the honeycomb lattice of graphene was confirmed by measuring the quenching capability through photo-luminescence spectroscopy using organic dyes. A plausible mechanism for the graphite exfoliation has been given where evolution of high density of oxygen molecules exerts large force on the graphitic layers leads to exfoliation and consequent synthesis of graphene. Furthermore, to explore the application of the graphene sheets so synthesized, we carried out studies which may make them as suitable carriers for drug delivery. For this, graphene sheets were functionalized with L-cysteine and attached with the drugs Amphotericin-B (AmB) and Tamoxifen citrate (TMX). The conjugation of drugs with L-cysteine functionalized graphene has been confirmed through FTIR and Raman spectroscopic techniques. The drug loading efficiency of FGS for AmB and TMX was 75.00% and 94.31%, respectively. The present formulation of drugs (AmB and TMX) conjugated with graphene is suitable for the targeted drug delivery as it will enhance the efficacy and reduce cytotoxicity associated with drug.
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Affiliation(s)
- Prashant Tripathi
- Nanoscience Unit, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Mahe Talat
- Nanoscience Unit, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Alok K Vishwakarma
- Nanoscience Unit, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - M A Shaz
- Nanoscience Unit, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Pawan Kumar
- CSIR-National Physical Laboratory, New Delhi 110012, India
| | | | - O N Srivastava
- Nanoscience Unit, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
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Shukla V, Bhatnagar A, Singh S, Soni PK, Verma SK, Yadav TP, Shaz MA, Srivastava ON. A dual borohydride (Li and Na borohydride) catalyst/additive together with intermetallic FeTi for the optimization of the hydrogen sorption characteristics of Mg(NH 2) 2/2LiH. Dalton Trans 2019; 48:11391-11403. [PMID: 31282909 DOI: 10.1039/c9dt02270h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The present study deals with the material tailoring of Mg(NH2)2-2LiH through dual borohydrides: the reactive LiBH4 and the non-reactive NaBH4. Furthermore, a pulverizer, as well as a catalyst FeTi, has been added in order to facilitate hydrogen sorption. Addition of LiBH4 to LiNH2 in a 1 : 3 molar ratio leads to the formation of Li4(BH4)(NH2)3 which also acts as a catalyst. However, the addition of NaBH4 doesn't lead to any compound formation but shows a catalytic effect. The onset dehydrogenation temperature of thermally treated Mg(NH2)2-2LiH/(Li4(BH4)(NH2)3-NaBH4) is 142 °C as against 196 °C for the basic material Mg(NH2)2-2LiH. However, with the FeTi catalyzed Mg(NH2)2-2LiH/(Li4(BH4)(NH2)3-NaBH4, it has been reduced to 120 °C. This is better than other similar amide/hydride composites where it is 149 °C (when the basic material is catalyzed with LiBH4). The FeTi catalyzed Mg(NH2)2-2LiH/(Li4(BH4)(NH2)3-NaBH4 sample shows better de/re-hydrogenation kinetics as it desorbs 3.9 ± 0.04 wt% and absorbs nearly 4.1 ± 0.04 wt% both within 30 min at 170 °C (with the H2 pressure being 0.1 MPa for desorption and 7 MPa for absorption). The eventual hydrogen storage capacity of Mg(NH2)2-2LiH/(Li4(BH4)(NH2)3-NaBH4 together with FeTi has been found to be ∼5.0 wt%. To make the effect of catalysts intelligible, we have put forward in a schematic way the role of Li and Na borohydrides with FeTi for improving the hydrogen sorption properties of Mg(NH2)2-2LiH.
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Affiliation(s)
- Vivek Shukla
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
| | - Ashish Bhatnagar
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
| | - Sweta Singh
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India. and Department of Physics, School of Physical and Material Sciences, Mahatma Gandhi Central University, Bihar 845401, India
| | - Pawan K Soni
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
| | - Satish K Verma
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
| | - T P Yadav
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
| | - M A Shaz
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
| | - O N Srivastava
- Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi-221005, India.
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5
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Singh AK, Srivastava ON, Singh K. Shape and Size-Dependent Magnetic Properties of Fe 3O 4 Nanoparticles Synthesized Using Piperidine. Nanoscale Res Lett 2017; 12:298. [PMID: 28449538 PMCID: PMC5406311 DOI: 10.1186/s11671-017-2039-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 03/29/2017] [Indexed: 05/23/2023]
Abstract
In this article, we proposed a facile one-step synthesis of Fe3O4 nanoparticles of different shapes and sizes by co-precipitation of FeCl2 with piperidine. A careful investigation of TEM micrographs shows that the shape and size of nanoparticles can be tuned by varying the molarity of piperidine. XRD patterns match the standard phase of the spinal structure of Fe3O4 which confirms the formation of Fe3O4 nanoparticles. Transmission electron microscopy reveals that molar concentration of FeCl2 solution plays a significant role in determining the shape and size of Fe3O4 nanoparticles. Changes in the shape and sizes of Fe3O4 nanoparticles which are influenced by the molar concentration of FeCl2 can easily be explained with the help of surface free energy minimization principle. Further, to study the magnetic behavior of synthesized Fe3O4 nanoparticles, magnetization vs. magnetic field (M-H) and magnetization vs. temperature (M-T) measurements were carried out by using Physical Property Measurement System (PPMS). These results show systematic changes in various magnetic parameters like remanent magnetization (Mr), saturation magnetization (Ms), coercivity (Hc), and blocking temperature (T B) with shapes and sizes of Fe3O4. These variations of magnetic properties of different shaped Fe3O4 nanoparticles can be explained with surface effect and finite size effect.
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Affiliation(s)
- Ashwani Kumar Singh
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi, 110067, India
| | - O N Srivastava
- Department of Physics, Banaras Hindu University, Varanasi, 221005, India
| | - Kedar Singh
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.
- Department of Physics, Banaras Hindu University, Varanasi, 221005, India.
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6
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Agarwal H, Yadav TP, Srivastava ON, Shaz MA. Structural analysis of nanocrystalline spinel synthesized by quasicrystalline precursor. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s2053273317090817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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7
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Das R, Talat M, Srivastava ON, Kayastha AM. Covalent immobilization of peanut β-amylase for producing industrial nano-biocatalysts: A comparative study of kinetics, stability and reusability of the immobilized enzyme. Food Chem 2017; 245:488-499. [PMID: 29287400 DOI: 10.1016/j.foodchem.2017.10.092] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 09/28/2017] [Accepted: 10/17/2017] [Indexed: 11/29/2022]
Abstract
Stability of enzymes is an important parameter for their industrial applicability. Here, we report successful immobilization of β-amylase (bamyl) from peanut (Arachis hypogaea) onto Graphene oxide-carbon nanotube composite (GO-CNT), Graphene oxide nanosheets (GO) and Iron oxide nanoparticles (Fe3O4). The Box-Behnken Design of Response Surface Methodology (RSM) was used which optimized parameters affecting immobilization and gave 90%, 88% and 71% immobilization efficiency, respectively, for the above matrices. β-Amylase immobilization onto GO-CNT (bamyl@GO-CNT) and Fe3O4 (bamyl@Fe3O4), resulted into approximately 70% retention of activity at 65 °C after 100 min of exposure. We used atomic force microscopy (AFM), scanning and transmission electron microscopy (SEM and TEM), Fourier transformed infrared (FT-IR) spectroscopy and fluorescence microscopy for characterization of free and enzyme bound nanostructures (NS). Due to the non-toxic nature of immobilization matrices and simple but elegant immobilization procedure, these may have potential utility as industrial biocatalysts for production of maltose.
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Affiliation(s)
- Ranjana Das
- School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Mahe Talat
- Nanoscience Centre, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - O N Srivastava
- Nanoscience Centre, Department of Physics (Centre of Advanced Studies), Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Arvind M Kayastha
- School of Biotechnology, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
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8
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Shukla V, Bhatnagar A, Soni PK, Vishwakarma AK, Shaz MA, Yadav TP, Srivastava ON. Enhanced hydrogen sorption in a Li–Mg–N–H system by the synergistic role of Li4(NH2)3BH4 and ZrFe2. Phys Chem Chem Phys 2017; 19:9444-9456. [DOI: 10.1039/c6cp08333a] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The present investigation describes the synergistic role of Li4(BH4)(NH2)3 and ZrFe2 in the hydrogen storage behaviour of a Li–Mg–N–H hydride system.
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Affiliation(s)
- Vivek Shukla
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
| | - Ashish Bhatnagar
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
| | - Pawan K. Soni
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
| | - Alok K. Vishwakarma
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
| | - M. A. Shaz
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
| | - T. P. Yadav
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
| | - O. N. Srivastava
- Hydrogen Energy Centre
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
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9
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Kajiwara K, Matsui Y, Yadav TP, Mukhopadhyay NK, Srivastava ON. Quasicrystal as a Catalyst for the Synthesis of Carbon Nanotubes. J Nanosci Nanotechnol 2016; 16:3084-3089. [PMID: 27455765 DOI: 10.1166/jnn.2016.12468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The present report describes the catalytic activity of mechanically activated nano quasicrystalline Al65Cu20Fe15 and related nano crystalline Al50Cu28Fe22 for the synthesis of carbon nanotubes (CNTs). CNTs are synthesized by catalytic decomposition of ethanol through nano quasicrystalline Al65Cu20Fe15 and related crystalline Al50Cu28Fe22 alloys as a catalyst. The synthesized multi-walled CNTs exhibits tube diameter ranging from 5 to 25 nm. The synthesized CNTs are characterized by scanning and transmission electron microscopy. It is found that Al65Cu20Fe15 nanoquasicystal shows better catalytic behaviour as compared to nano-crystalline Al50Cu28Fe22 alloys for decomposition of ethanol during the synthesis of multi-walled CNTs.
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10
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Singh AK, Srivastava ON. One-Step Green Synthesis of Gold Nanoparticles Using Black Cardamom and Effect of pH on Its Synthesis. Nanoscale Res Lett 2015; 10:1055. [PMID: 26334545 PMCID: PMC4559564 DOI: 10.1186/s11671-015-1055-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 08/19/2015] [Indexed: 05/14/2023]
Abstract
In the present article, an effective, one-step, and environmentally benign protocol for the synthesis of gold nanoparticles has been discussed. The black cardamom extract is used as a reducing agent for HAuCl4.3H2O. In order to synthesize gold nanoparticles, an aqueous solution of HAuCl4.3H2O was mixed with an optimized concentration of black cardamom extract where 1,8-cineole is the dominant component. Choosing black cardamom extract as a reducing agent can be justified under the light of the fact that it has a very fast reducing ability. Gold nanoparticles with different shapes and sizes were synthesized by varying the ratio of AuCl4 ions to black cardamom extract. Kinetics of reactions has been evaluated through monitoring of surface plasmon behavior of gold nanoparticles as a function of time. Based on Fourier transform infrared spectroscopy (FTIR) studies, a tentative mechanism of reduction of Au nanoparticles has also been proposed which includes oxidation of 1,8-cineole to 2-oxo-1,8-cineole. Further, a comprehensive study to investigate the effect of pH on the synthesis of Au nanoparticles has been carried out.
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Affiliation(s)
- Ashwani Kumar Singh
- DST Unit on Nanoscience and Technology, Department of Physics, Banaras Hindu University, Varanasi, 221005 India
| | - O. N. Srivastava
- DST Unit on Nanoscience and Technology, Department of Physics, Banaras Hindu University, Varanasi, 221005 India
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12
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Tripathi P, Prakash Patel CR, Dixit A, Singh AP, Kumar P, Shaz MA, Srivastava R, Gupta G, Dhawan SK, Gupta BK, Srivastava ON. High yield synthesis of electrolyte heating assisted electrochemically exfoliated graphene for electromagnetic interference shielding applications. RSC Adv 2015. [DOI: 10.1039/c4ra17230b] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Demonstration of high yield synthesis of graphene by electrolyte heating assisted electrochemically exfoliation method for high performance EMI shielding applications.
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Affiliation(s)
- Prashant Tripathi
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | - Ch. Ravi Prakash Patel
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | - Abhishek Dixit
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | | | - Pawan Kumar
- CSIR-National Physical Laboratory
- New Delhi-110 012
- India
| | - M. A. Shaz
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | | | - Govind Gupta
- CSIR-National Physical Laboratory
- New Delhi-110 012
- India
| | - S. K. Dhawan
- CSIR-National Physical Laboratory
- New Delhi-110 012
- India
| | | | - O. N. Srivastava
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
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13
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Singh S, Tripathi P, Bhatnagar A, Prakash Patel CR, Singh AP, Dhawan SK, Gupta BK, Srivastava ON. A highly porous, light weight 3D sponge like graphene aerogel for electromagnetic interference shielding applications. RSC Adv 2015. [DOI: 10.1039/c5ra19273k] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Facile synthesis of a highly porous, light weight 3D sponge like graphene aerogel derived from graphene oxide for microwave shielding applications.
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Affiliation(s)
- Sweta Singh
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | - Prashant Tripathi
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | - Ashish Bhatnagar
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | - Ch. Ravi Prakash Patel
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
| | | | - S. K. Dhawan
- CSIR – National Physical Laboratory
- New Delhi-110 012
- India
| | | | - O. N. Srivastava
- Nanoscience Centre
- Department of Physics (Centre of Advanced Studies)
- Banaras Hindu University
- Varanasi-221005
- India
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14
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Singh AK, Tripathi YB, Pandey N, Singh DP, Tripathi D, Srivastava ON. Enhanced antilipopolysaccharide (LPS) induced changes in macrophage functions by Rubia cordifolia (RC) embedded with Au nanoparticles. Free Radic Biol Med 2013; 65:217-223. [PMID: 23774043 DOI: 10.1016/j.freeradbiomed.2013.06.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 06/04/2013] [Indexed: 11/16/2022]
Abstract
In this paper, we have shown that gold nanoparticles (Au (NPs)) embedded in Rubia cordifolia (RC) matrix (RC-Au (NPs)) exhibit a high therapeutic value relating to its anti-inflammatory characteristics. It was prepared by utilizing the reducing properties of RC to convert HAuCl4 into Au (NPs). In order to compare its effectiveness, with respect to Au (NPs), the latter was synthesized separately by reducing HAuCl4 with lemon extract. These Au (NPs) along with RC-Au (NPs) were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), and UV-visible spectroscopy. The enhancement in anti-inflammatory characteristics was assessed as its inhibitory potential for lipopolysaccharide (LPS)-induced nitric oxide (NO) release, by rat peritoneal macrophages. The RC-Au (NPs) significantly enhanced its potential to inhibit NO release, which was reported in terms of inhibitory concentration for 50% inhibition (IC50=11.98 ng/ml), as compared to either RC extract (IC50=47 × 10(3)ng/ml) or to Au (NPs) (IC50=587.50 ng/ml).
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Affiliation(s)
| | - Yamini B Tripathi
- Department of Medicinal Chemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Nidhi Pandey
- Department of Medicinal Chemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - D P Singh
- Department of Physics, University of Santiago, Chile
| | - Deepshikha Tripathi
- R and D Centre, Prof SN Tripathi Memorial Foundation, Gandhi Nagar, Naria, Varanasi 221005, India
| | - O N Srivastava
- Department of Physics, Banaras Hindu University, Varanasi, India 2210055.
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15
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Bhatnagar A, Pandey SK, Shahi RR, Hudson MSL, Shaz MA, Srivastava ON. Synthesis, characterization and hydrogen sorption studies of mixed sodium-potassium alanate. Crystal Research and Technology 2013. [DOI: 10.1002/crat.201300119] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Ashish Bhatnagar
- Hydrogen storage mission mode MNRE project unit, Hydrogen Energy Centre; Department of Physics, Banaras Hindu University; Varanasi-221005; India
| | - Sunita K. Pandey
- Hydrogen storage mission mode MNRE project unit, Hydrogen Energy Centre; Department of Physics, Banaras Hindu University; Varanasi-221005; India
| | - Rohit R. Shahi
- Hydrogen storage mission mode MNRE project unit, Hydrogen Energy Centre; Department of Physics, Banaras Hindu University; Varanasi-221005; India
| | - M. Sterlin Leo Hudson
- Hydrogen storage mission mode MNRE project unit, Hydrogen Energy Centre; Department of Physics, Banaras Hindu University; Varanasi-221005; India
| | - M. A. Shaz
- Hydrogen storage mission mode MNRE project unit, Hydrogen Energy Centre; Department of Physics, Banaras Hindu University; Varanasi-221005; India
| | - O. N. Srivastava
- Hydrogen storage mission mode MNRE project unit, Hydrogen Energy Centre; Department of Physics, Banaras Hindu University; Varanasi-221005; India
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16
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Pandey SK, Bhatnagar A, Shahi RR, Hudson MSL, Singh MK, Srivastava ON. Effect of TiO2 nanoparticles on the hydrogen sorption characteristics of magnesium hydride. J Nanosci Nanotechnol 2013; 13:5493-5499. [PMID: 23882784 DOI: 10.1166/jnn.2013.7516] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The present paper explores the enhancement in hydrogen sorption behavior of MgH2 with TiO2 nanoparticles. The catalytic effect of TiO2 nanoparticles with different sizes (7, 25, 50, 100 and 250 nm) were used for improving the sorption characteristics of MgH2. The MgH2 catalyzed with 50 nm of TiO2 exhibited the optimum catalytic effect for hydrogen sorption behavior. The desorption temperature of MgH2 catalyzed through 50 nm TiO2 was found to be 310 degrees C. This is 80 degrees C lower as compared to MgH2 having a desorption temperature of 390 degrees C. It was noticed that the dehydrogenated MgH2 catalyzed with 50 nm TiO2 reabsorbed 5.1 wt% of H2 within 6 minutes at temperature and pressure of 250 degrees C and 50 atm, respectively. The 50 nm TiO2 catalyst lowered the absorption activation energy of MgH2 from - 92 to - 52.7 kJ mol(-1).
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Affiliation(s)
- Sunita K Pandey
- Hydrogen Storage Mission Mode MNRE Project Unit, Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi 221005, India
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17
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Singh J, Kumar P, Hui KS, Hui KN, Ramam K, Tiwari RS, Srivastava ON. Synthesis, band-gap tuning, structural and optical investigations of Mg doped ZnO nanowires. CrystEngComm 2012. [DOI: 10.1039/c2ce06650e] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Kumar P, Singh J, Parashar V, Singh K, Tiwari RS, Srivastava ON, Ramam K, Pandey AC. Investigations on structural, optical and second harmonic generation in solvothermally synthesized pure and Cr-doped ZnO nanoparticles. CrystEngComm 2012. [DOI: 10.1039/c1ce06127e] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Tiwari RS, Singh D, Shahi RR, Srivastava ON. Effect of Ti addition on the hydrogen storage properties of nanoquasicrystal-glass composites in (Zr 69.5Al 7.5Cu 12Ni 11) 100−xTi xalloys. Acta Crystallogr A 2011. [DOI: 10.1107/s0108767311084273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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20
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Shaz MA, Shahi RR, Srivastava ON. Hydrogen storage characteristics of melt spun Ti 45Zr 38Ni 17nano-quasicrystalline alloys. Acta Crystallogr A 2011. [DOI: 10.1107/s0108767311089550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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21
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Yadav TP, Mukhopadhyay NK, Srivastava ON. Structural transformation in Al-Fe-Cu-Mn one-dimensional quasicrystals. Acta Crystallogr A 2011. [DOI: 10.1107/s010876731108425x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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22
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Yadav TP, Shaz MA, Tiwari RS, Srivastava ON. Investigation of transition from decagonal to vacancy ordered phase on replacement of Co by Cu in Al70Co15–
x
Cu
x
Ni15. Z KRIST-CRYST MATER 2009. [DOI: 10.1524/zkri.218.1.12.20774] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The alloy with composition Al70Co15Ni15 forms one of the important quasicrystalline phase exhibiting formation of decagonal variants [1, 2]. In the present investigation, copper has been substituted in place of cobalt i.e. the phases corresponding to Al70Co15–
x
Cu
x
Ni15, have been investigated. It is found that when copper concentration reaches to a value of 10 atomic percent with the composition corresponding to Al70Co5Cu10Ni15, the decagonal phase starts yielding to give rise to vacancy ordered phase. When all cobalt is replaced by copper i.e. when the composition corresponds to Al70Cu15Ni15, the decagonal phase disappears and the only phase observed is the vacancy ordered phase. It can thus be said that copper substitution brings in decagonal to vacancy ordered (VOP) phase transition. It has also been observed that gradual increase in concentration of Cu in Al70Co15–
x
Cu
x
Ni15 leads to cellular to dendritic transition in morphology.
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23
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Abstract
In the present work, aligned TiO2 nanotubes have been synthesized by a simple method of electrochemical anodization of high purity, well cleaned, etched and ultrasonicated Ti-sheet (Purity approximately 99.99%) in a fluoride mediated electrolytic media consisting of a solution of 0.14 M NaF and a solution of 0.5 M/1.0 M H3PO4. Studies on the effects of anodization voltage, time and electrolyte concentration on the formation of TiO2 nanotubes have been carried out. The TiO2 nanotube arrays have been synthesized at applied anodization voltages of approximately 10 V and approximately 20 V. The anodization was carried out for 1 hour and 2 hours at each applied voltage. Structural/microstructural characterizations of TiO2 nanotubes have been carried out through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM images of TiO, nanotubes showed interesting features relating to morphology, the pore size (diameter of the tubes) and the lengths of the tube. TEM investigations revealed that the as synthesized nanotubes are amorphous in nature and on electron beam annealing, these transformed to crystalline phases (rutile and brookite). The optical characterizations through UV-Visible spectroscopy exhibited that the band gap are approximately 3.03 eV and approximately 2.87 eV for tubes synthesized at applied anodization voltages of approximately 10 V and approximately 20 V respectively. A tentative mechanism for the growth of TiO2 nanotube has been put forward.
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Affiliation(s)
- P K Dubey
- Department of Physics, Banaras Hindu University, Varanasi 221005, India
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24
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Yadav TP, Mukhopadhyay NK, Shaz MA, Tiwari RS, Srivastava ON. Formation of nano-quasicrystalline decagonal phase in the Al70Cu10Co5Ni15 system by high energy ball milling. J Nanosci Nanotechnol 2009; 9:5527-5532. [PMID: 19928257 DOI: 10.1166/jnn.2009.1130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A nano decagonal quasicrystalline phase in the Al70Cu10Co5Ni15 alloy has been synthesized by mechanical alloying of a mixture of elemental powders followed by annealing. A high-energy ball milling of the elemental mixture of Al, Cu, Co and Ni leads to the formation of B2 type quaternary intermetallic alloys. The X-ray diffraction and transmission electron microscopy techniques have been employed for characterization of the samples. It was observed that the dissolution of the individual elements into an alloy led to the formation of a nano B2 phase. This phase was found to be quite stable against milling and no other crystalline or amorphous phases could be detected. Milled powder after annealing at 700 degrees C for 60 h was found to transform to nano-decagonal phase. Attempts have been made to understand the evolution of the complex intermetallic nano phases and their relative stability during milling.
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Affiliation(s)
- T P Yadav
- Department of Physics, Banaras Hindu University, Varanasi 221005, India
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25
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Awasthi S, Awasthi K, Kumar R, Srivastava ON. Functionalization effects on the electrical properties of multi-walled carbon nanotube-polyacrylamide composites. J Nanosci Nanotechnol 2009; 9:5455-5460. [PMID: 19928243 DOI: 10.1166/jnn.2009.1160] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Multi-walled carbon nanotubes (MWNTs)-polyacrylamide (PAM) composites have been prepared using as purified, with ball milling and functionalized MWNTs by solution cast technique and characterized through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A comparative study has been made on the electrical property of these MWNTs-PAM composites with different MWNTs loadings. It has been shown that the ball milling and functionalization of MWNTs improves the dispersion of MWNTs into the polymer matrix. As the MWNTs loading increases from 0 to 40 wt% electrical conductivity of composite film increases by approximately 7 orders of magnitude whereas the electrical conductivity of functionalized composite film increases only approximately 4 orders of magnitude with respect to the pure PAM film. A model based on power law percolation for the electronic behavior of above composite has been developed and shows good agreement with the experimental data.
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26
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Yadav R, Dobal P, Shripathi T, Katiyar RS, Srivastava ON. Effect of Growth Temperature on Bamboo-shaped Carbon-Nitrogen (C-N) Nanotubes Synthesized Using Ferrocene Acetonitrile Precursor. Nanoscale Res Lett 2008; 4:197-203. [PMID: 20596277 PMCID: PMC2894332 DOI: 10.1007/s11671-008-9225-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 11/24/2008] [Indexed: 05/06/2023]
Abstract
This investigation deals with the effect of growth temperature on the microstructure, nitrogen content, and crystallinity of C-N nanotubes. The X-ray photoelectron spectroscopic (XPS) study reveals that the atomic percentage of nitrogen content in nanotubes decreases with an increase in growth temperature. Transmission electron microscopic investigations indicate that the bamboo compartment distance increases with an increase in growth temperature. The diameter of the nanotubes also increases with increasing growth temperature. Raman modes sharpen while the normalized intensity of the defect mode decreases almost linearly with increasing growth temperature. These changes are attributed to the reduction of defect concentration due to an increase in crystal planar domain sizes in graphite sheets with increasing temperature. Both XPS and Raman spectral observations indicate that the C-N nanotubes grown at lower temperatures possess higher degree of disorder and higher N incorporation.
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Affiliation(s)
- RamManohar Yadav
- Department of Physics, Banaras Hindu University, Varanasi, 221005, India
- Department of Physics, VSSD College, Kanpur, 208002, India
| | | | - T Shripathi
- UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore, 452017, India
| | - RS Katiyar
- Department of Physics, University of Puerto Rico, San Juan, PR, USA
| | - ON Srivastava
- Department of Physics, Banaras Hindu University, Varanasi, 221005, India
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27
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Abstract
The perovskite manganites with generic formula RE(1-x)AE(x)MnO(3) (RE = rare earth, AE = Ca, Sr, Ba and Pb) have drawn considerable attention, especially following the discovery of colossal magnetoresistance (CMR). The most fundamental property of these materials is strong correlation between structure, transport and magnetic properties. They exhibit extraordinary large magnetoresistance named CMR in the vicinity of the insulator-metal/paramagnetic-ferromagnetic transition at relatively large applied magnetic fields. However, for applied aspects, occurrence of significant CMR at low applied magnetic fields would be required. This review consists of two sections: in the first section we have extensively reviewed the salient features, e.g. structure, phase diagram, double-exchange mechanism, Jahn-Teller effect, different types of ordering and phase separation of CMR manganites. The second is devoted to an overview of experimental results on CMR and related magnetotransport characteristics at low magnetic fields for various doped manganites having natural grain boundaries such as polycrystalline, nanocrystalline bulk and films, manganite-based composites and intrinsically layered manganites, and artificial grain boundaries such as bicrystal, step-edge and laser-patterned junctions. Some other potential magnetoresistive materials, e.g. pyrochlores, chalcogenides, ruthenates, diluted magnetic semiconductors, magnetic tunnel junctions, nanocontacts etc, are also briefly dealt with. The review concludes with an overview of grain-boundary-induced low field magnetotransport behavior and prospects for possible applications.
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Affiliation(s)
- P K Siwach
- Physics Department, Banaras Hindu University, Varanasi-221 005, India
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28
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Mishra PR, Awasthi K, Srivastava ON. Formation and microstructural characterization of coaxial carbon cylinders consisting of aligned carbon nanotube stacks. J Nanosci Nanotechnol 2007; 7:1815-9. [PMID: 17654946 DOI: 10.1166/jnn.2007.722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The macroscopic coaxial carbon cylinders (dia. approximately 0.5 cm with varying lengths approximately 2-5 cm) consisting of aligned carbon nanotube (CNT) stacks have been prepared by spray pyrolysis of benzene-ferrocene solution in argon atmosphere at approximately 850 degrees C-900 degrees C temperature. The coaxial carbon cylinders of CNT stacks have been formed directly inside the quartz tube. We attempted to prepare superimposed multi carbon cylinder configurations, each consisting of ordered and aligned CNTs stacked over each other. For this, we have terminated the spray of precursor after run of about 25 minutes, for a short interval (approximately 5 min), and then the solution was sprayed again over the already deposited hot CNT stack. Gross structural characterization of CNTs was done through X-ray diffraction technique (XRD). Microstructural characterizations of as prepared coaxial carbon cylinders with CNT stacks were done by scanning electron microscopic (SEM) techniques. SEM studies show that the CNTs are well aligned along the periphery of the cross section of coaxial carbon cylinder, each consisting of CNTs of the type described in the above. Comparisons have been made between the present macroscopic coaxial carbon cylinders with CNT stacks studied earlier by several other workers. Plausible explanation for the synthesis of CNT stacks will be put forward.
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Affiliation(s)
- P R Mishra
- Physics Department, Banaras Hindu University, Varanasi 221005, India
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29
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Singh J, Tiwari RS, Srivastava ON. Synthesis of zinc oxide nanotetrapods and nanorods by thermal evaporation without catalysis. J Nanosci Nanotechnol 2007; 7:1783-6. [PMID: 17654939 DOI: 10.1166/jnn.2007.715] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
ZnO nanotetrapods and nanorods have been synthesized by a simple thermal evaporation of Zn powder (300 mesh, 99.99% purity) under simultaneous flow of oxygen and argon gases in two-zone furnace in two different temperature regions. These ZnO nanostructures have hexagonal structure, which grow along the [001] direction in the form of nanotetrapods (diameter approximately 60-150 nm, length approximately 1-4 microm) and nanorods (diameter approximately 30-60 nm, length approximately 2-5 microm). The morphologies of these ZnO nanostructures have been investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been found that growth parameters like temperature, gas flow rate etc., control the diameter of the nanotetrapods and nanorods. These novel structures of ZnO nanorods and nanotetrapods may be attractive for optical and other nanodevices.
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Affiliation(s)
- Jai Singh
- Department of Physics, Banaras Hindu University, Varanasi 221005, India
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30
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Yadav TP, Mukhopadhyay NK, Tiwari RS, Srivastava ON. Synthesis of nanocrystalline (Co, Ni)Al2O4 spinel powder by mechanical milling of quasicrystalline materials. J Nanosci Nanotechnol 2007; 7:575-9. [PMID: 17450798 DOI: 10.1166/jnn.2007.128] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
In the present study, attempts have been made to synthesize the nano-crystalline (Co, Ni)Al2O4 spinel powders by ball milling and subsequent annealing. An alloy of Al70Co15Ni15, exhibiting the formation of a complex intermetallic compound known as decagonal quasicrystal is selected as the starting material for mechanical milling. It is interesting to note that this alloy is close to the stoichiometry of aluminum and transition metal atoms required to form the aluminate spinel. The milling was carried out in an attritor mill at 400 rpm for 40 hours with ball to powder ratio of 20 : 1 in hexane medium. Subsequent to this annealing was performed in an air ambience for 10, 20, and 40 h at 600 degrees C in side the furnace in order to oxidize the decagonal phase and finally to form the spinel structure. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of nano-sized decagonal phase after milling and then (Co, Ni)Al2O4 spinel type phase after annealing. The XRD studies reveal the lattice parameter to be 8.075 angstroms and the lattice strain as 0.6%. The XRD and TEM explorations of spinel phase indicate the average grain size to be approximately 40 nm.
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Affiliation(s)
- T P Yadav
- Department of Physics, Banaras Hindu University, Varanasi 221005, India
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31
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Abstract
This paper deals with the investigations on the nucleation and growth of Zinc Oxide (ZnO) nanostructures in a catalyst free synthesis. The ZnO nanostructures have been formed by evaporation of Zn (99.99%) in O2 and Ar atmosphere in single zone furnace under two temperature regions, region A (approximately 1173-1073 K) and region B (approximately 873-773 K). Through application of XRD and TEM techniques, it has been shown that first ZnO is formed which changes to ZnOx through creation of oxygen vacancies. The ZnOx acts as self-catalyst and leads to formation of various nanostructures. Those observed in the present investigation are nanotetrapods (1 D, diameter approximately 70-450 nm, length approximately 2-4.5 approximatelym) nanorods (1 D, diameter approximately 45-95 nm, length approximately 2.5-4.5 microm), nanoflowers(2D, central core diameter approximately 90-185 nm, length of petals/nanorod approximately 1.0-3.5 microm) and nanoparticles (3D, size approximately 0.85-2.5 microm). These nanostructures have been revealed by SEM explorations. Attempts have been made to explain the formation of the various nanostructures in terms of the creation and distribution of the ZnOx, the temperature as well as oxygenation conditions.
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Affiliation(s)
- Jai Singh
- Department of Physics, Banaras Hindu University, Varanasi-221005, India
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32
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Singh DP, Yadav RM, Srivastava ON. Synthesis of Nanostructured Silicon Carbide Films Through Spray Pyrolysis of Ball-Milled Silicon. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/cvde.200504213] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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33
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Abstract
Carbon nanotubes play a fundamental role in the rapidly developing field of nanoscience and nanotechnology because of their unique properties and high potential for applications. In this article, the different synthesis methods of carbon nanotubes (both multi-walled and single-walled) are reviewed. From the industrial point of view, the chemical vapor deposition method has shown advantages over laser vaporization and electric arc discharge methods. This article also presents recent work in the controlled synthesis of carbon nanotubes with ordered architectures. Special carbon nanotube configurations, such as nanocoils, nanohorns, bamboo-shaped and carbon cylinder made up from carbon nanotubes are also discussed.
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Affiliation(s)
- Kalpana Awasthi
- Physics Department, Banaras Hindu University, Varanasi, India
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34
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Yadav RM, Shripathi T, Srivastava A, Srivastava ON. Effect of ferrocene concentration on the synthesis of bamboo-shaped carbon-nitrogen nanotube bundles. J Nanosci Nanotechnol 2005; 5:820-4. [PMID: 16010946 DOI: 10.1166/jnn.2005.102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We have investigated the effect of ferrocene concentration on the synthesis of carbon-nitrogen (C-N) nanotubes. The bamboo-shaped carbon-nitrogen nanotubes were synthesized by spray pyrolysis of Fe(C5H5)2 and CH3CN solution using argon as a carrier gas at the optimum temperature of approximately 900 degrees C. The effect of ferrocene concentration on the length and concentration of nitrogen in nanotubes was studied. Micro-structural features of the nanotubes were monitored employing scanning and transmission electron microscopic techniques. SEM studies reveal that with decreasing ferrocene concentration from 25 mg ml(-1) to 5 mg ml(-1), the length of the nanotubes vary from 80 microm to 430 microm. A feasible growth model has been described and discussed. X-ray photoelectron spectroscopic studies have confirmed the formation of nitrogen-doped carbon nanotubes. These studies reveal that the nitrogen concentration in the nanotubes decreases with the increase of ferrocene concentration. The present synthesis route also provides means of producing carbon nanotubes with different concentrations of nitrogen.
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Affiliation(s)
- Ram Manohar Yadav
- Department of Physics, Banaras Hindu University, Varanasi 221005, India
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35
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Yadav RM, Srivastava A, Srivastava ON. Synthesis of bamboo-shaped carbon-nitrogen nanotubes using acetonitrile-ferrocene precursor. J Nanosci Nanotechnol 2004; 4:719-21. [PMID: 15570951 DOI: 10.1166/jnn.2004.105] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We report the formation of bamboo-shaped carbon-nitrogen nanotubes by employing a simple, one-step and economically viable spray pyrolysis technique using new precursor; acetonitrile and ferrocene solution. By varying the concentration of ferrocene with respect to acetonitrile, it has been found that the optimum concentration of ferrocene in acetonitrile is 5 mg/ml. The special feature of the as-synthesized bamboo-shaped carbon-nitrogen nanotubes bundles is that they are produced in a high yield (1.25 gms/run). They also have long linear extents (approximately 430 microm) and are very clean. The average composition of carbon-nitrogen nanotubes comes out to be C26N.
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36
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Srivastava A, Srivastava ON, Talapatra S, Vajtai R, Ajayan PM. Carbon nanotube filters. Nat Mater 2004; 3:610-614. [PMID: 15286755 DOI: 10.1038/nmat1192] [Citation(s) in RCA: 211] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2004] [Accepted: 06/29/2004] [Indexed: 05/24/2023]
Abstract
Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus ( approximately 25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.
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Affiliation(s)
- A Srivastava
- Department of Physics, Banaras Hindu University, Varanasi, India-221005
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37
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Shekhar C, Giri R, Tiwari RS, Srivastava ON. On the synthesis and characterization of La doped MgB2 superconductor. Cryst Res Technol 2004. [DOI: 10.1002/crat.200310244] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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38
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Singh DP, Singh AK, Srivastava ON. Formation and size dependence of germanium nanoparticles at different helium pressures. J Nanosci Nanotechnol 2003; 3:545-548. [PMID: 15002138 DOI: 10.1166/jnn.2003.223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report the formation of germanium nanoparticles and threadlike nanostructures by the process of thermal vapor deposition. Germanium was thermally evaporated and condensed on graphite substrates under varied ambient helium pressures of 100, 200, 300, and 400 torr. The deposited films were characterized through transmission electron microscopy. These investigations revealed the occurrence of germanium particles. The size of these particles varied inversely with ambient pressure. Whereas for an ambient pressure of 100 torr the average particle size was approximately 0.3-0.5 micron, for 400 torr the average size was approximately 30-60 nm. At high He pressure (e.g., approximately 400 torr), the nanoparticles that formed when annealed for 30 min at 200 degrees C in vacuum adopted threadlike nanostructures. A qualitative explanation has been put forward for the formation of germanium particles and variation of size of these particles with helium pressure in terms of condensation, collision, and coalescence.
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Affiliation(s)
- D P Singh
- Department of Physics, Banaras Hindu University, Varanasi 221 005, India
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39
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Misra DK, Tiwari RS, Srivastava ON. Amorphous to icosahedral phase transformation in rapidly quenched Al–Cu–V and Al–Cu–Ti alloys. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/pssa.200306695] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Awasthi K, Singh AK, Srivastava ON. Formation of carbon nanotubes without iron inclusion and their alignment through ferrocene and ferrocene-ethylene pyrolysis. J Nanosci Nanotechnol 2003; 3:540-544. [PMID: 15002137 DOI: 10.1166/jnn.2003.237] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
So far carbon nanotubes grown from the method most common method at present, that is, pyrolysis of ferrocene, invariably contains Fe inclusion. In addition, they are generally grown in random configurations. In the present investigations CNTs without Fe inclusion and in aligned configurations have been prepared by the pyrolysis of ferrocene (C10H10Fe) as well as pyrolysis of ferrocene in the presence of ethylene (C2H4). This has been achieved through optimization of growth parameters, for example, heating rate of ferrocene, pyrolysis temperature, and flow rates of carrier gas argon (Ar) and ethylene (C2H4). The as-synthesized samples have been characterized by transmission and scanning electron microscopic techniques. The optimum results relating to synthesis of carbon nanotubes without Fe inclusion and in aligned configurations have been obtained at 1000 degrees C pyrolysis temperature under flow rates of Ar of approximately 1000 sccm and of C2H4 of approximately 100 sccm. These carbon nanotubes have been found to have an outer diameter between approximately 20 and 60 nm and lengths between approximately 15 and 20 microns.
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Affiliation(s)
- Kalpana Awasthi
- Department of Physics, Banaras Hindu University, Varanasi, India
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Giri R, Verma GD, Tiwari RS, Srivastava ON. Influence of simultaneous doping of Tl and Bi on microstructure and critical current density of HgBa2Ca2Cu3O8+δ. Cryst Res Technol 2003. [DOI: 10.1002/crat.200310092] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Misra DK, Tiwari RS, Srivastava ON. Formation of a new F.C.C.τ2 phase in rapidly quenched Al55Cu35V10 alloy. Cryst Res Technol 2003. [DOI: 10.1002/crat.200310091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Yadav RM, Singh AK, Srivastava ON. Synthesis and characterization of Cu nanotubes and nanothreads by electrical arc evaporation. J Nanosci Nanotechnol 2003; 3:223-225. [PMID: 14503405 DOI: 10.1166/jnn.2003.196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report the formation and characterization of copper nanostructures, nanotubules and nanothreads, which were obtained by electrical arc evaporation of Cu electrodes under varied conditions of He ambience. Electrical arc evaporation was done with approximately 10 V and (approximately 50-100 A) DC current. The current was used in a pulse mode. The evaporated material was condensed on a formvar-coated Cu grid mounted on a liquid N2-cooled specimen holder. Transmission electron microscopy was employed to characterize the condensed materials. These investigations revealed that the condensed materials consisted of the mentioned nanostructures. Nanotubes and nanothreads are formed for a He pressure in the chamber corresponding to approximately 140 and approximately 500 torr, respectively. Extensive electron microscopic investigations showed that the diameter of the nanotubes varied from approximately 5 nm to approximately 50 nm and their length from 2 microns to 3 microns.
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Affiliation(s)
- Ram Manohar Yadav
- Department of Physics, Banaras Hindu University, Varanasi 221005, India
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Awasthi K, Singh AK, Srivastava ON. Synthesis and characterization of lanthanum carbide nanotubes. J Nanosci Nanotechnol 2002; 2:67-71. [PMID: 12908323 DOI: 10.1166/jnn.2002.078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Lanthanum carbide nanotubes have been synthesized by d.c. arc evaporation (approximately 20-30 V, approximately 200 Amp) of lanthanum metal (90 wt.%)-loaded graphite rod in a helium atmosphere (665 mbar). To explore the possibility of formation of lanthanum carbide nanotubes, the experiments were carried out with lanthanum metal in different concentrations (i.e., 30, 50, 70, and 90 wt.%) in the graphite rod. The as-synthesized samples were characterized by transmission electron microscopy and X-ray diffractometry. Lanthanum carbide nanotubes (LCNTs) with a diameter of approximately 65 to 95 nm and a length of approximately 0.2 to 1.5 microns were obtained in this study.
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Affiliation(s)
- Kalpana Awasthi
- Department of Physics, Banaras Hindu University, Varanasi-221005, India
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Khare V, Tiwari RS, Srivastava ON. On the curious structural phases in Al-deficient (Al62Cu23Cr15) and Al-rich (Al68Cu17Cr15) quasicrystalline alloys. Cryst Res Technol 1997. [DOI: 10.1002/crat.2170320408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Den Boer JA, van Megen HJ, Fleischhacker WW, Louwerens JW, Slaap BR, Westenberg HG, Burrows GD, Srivastava ON. Differential effects of the D1-DA receptor antagonist SCH39166 on positive and negative symptoms of schizophrenia. Psychopharmacology (Berl) 1995; 121:317-22. [PMID: 8584612 DOI: 10.1007/bf02246069] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In the present open study the effects of the D1-dopamine antagonist SCH 39166 on positive and negative symptoms of schizophrenia (DSM-IIIR) were investigated. SCH 39166 was given orally according to a fixed dosage schedule (day 1: 25 mg b.i.d; day 4: 50 mg b.i.d.; day 7: 100 mg b.i.d.; day 18: 200 mg b.i.d.; day 21: 225 mg b.i.d.). Seven patients completed 2 weeks, and five patients completed the study. The reason for premature withdrawal was lack of efficacy or refusal to take SCH 39166. In none of the patients a reduction of the BPRS or CGI score was found. As measured with the PANSS, a significant reduction was observed in the score of the negative subscale, whereas the positive symptoms scale and general psychopathology score remained unaffected. Akathisia, rigidity and hypokinesia were reported occasionally, although only mild in severity. The results of the present study do not support the hypothesis that D1-dopamine antagonists are clinically effective antipsychotics in schizophrenia, considering the fact that SCH 39166 had no effect on positive symptoms. The present study provides circumstantial evidence for an effect of SCH 39166 on negative symptoms.
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Affiliation(s)
- J A Den Boer
- Department of Psychiatry, University Hospital, Utrecht, The Netherlands
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Mandal P, Tiwari RS, Srivastava ON. Occurrence of a quasicrystalline phase in the Ti-Fe(Ni)-Si system. Phys Rev B Condens Matter 1993; 47:11774-11779. [PMID: 10005346 DOI: 10.1103/physrevb.47.11774] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Mandal P, Mandal RK, Tiwari RS, Srivastava ON. Commensurate ordering in rapidly solidified Ti-Fe-Si alloys. Phys Rev B Condens Matter 1992; 45:7521-7524. [PMID: 10000548 DOI: 10.1103/physrevb.45.7521] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Mandal P, Tiwari RS, Srivastava ON. bcc metastable phase coexisting with the icosahedral phase in rapidly quenched Fe28Ti68Si4 alloys. Phys Rev B Condens Matter 1991; 44:11683-11688. [PMID: 9999301 DOI: 10.1103/physrevb.44.11683] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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