Vol 25 No 8

Asian Journal of Physics Vol. 25 No 8, 2016, 00-00

Enhanced Thermal Conductivity in Nanowire Doped Copper Selenide

Ranu Bhatt^1,*, Anil Bohra¹, Gopika Krishnan^1,
2, Shovit Bhattacharya¹, Ranita Basu¹, A.K. Debnath¹, Ajay Singh¹, D.K. Aswal^1,
3, K.P. Muthe¹, S.K. Gupta¹

¹Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai – 400085

² Indian Institute of Science Educations and Research, Thiruvantahapuram – 695016

³National Physical Laboratory, K.S. Krishnanan Marg, Pusa, New Delhi-110012

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In present work, we have investigated the effect of Cu_2-xSe nanowire (NW) doping (0-15 wt. %) on the structural and thermal transport properties of mechanically alloyed Cu₂Se nanopowder. The synthesis of Cu_2-xSe NW was carried out using the surfactant-free aqueous route. The morphology and composition of the NW was studied using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). The X-ray diffraction (XRD) of the NW shows the formation of cubic Cu_2-xSe phase along with presence of Cu₂SeO₃ as a minority secondary phase. The optical band gap (E_g) of the NW calculated using UV-vis spectra was found to be indirect band gap of 0.51 eV. Chemical composition and binding energy (B.E.) of the samples were studied using X-ray photoelectron spectroscopy (XPS) suggests the formation of copper oxide in addition of copper selenide in the sample. The thermal transport measurement shows drastic enhancement in the thermal conductivity (κ) of the sample with increasing NW content in temperature range of 30- 300º C. This enhancement in κ may be attributed to; (i) the suppression of α-β phase transformation and (ii) percolation path provided by the doped NW’s. © Anita Publications. All rights reserved.

Total Refs : 16

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Asian Journal of Physics Vol. 25 No 8, 2016,00-00

Improved H₂S Sensing Characteristics of Al Modified SnO₂ Thin Films

Deepak. Goyal, Niranjan S. Ramgir^*, C. P. Goyal, A. K. Debnath, K. P. Muthe, S. K. Gupta

Thin Films Devices Section, Technical Physics Division, BARC, Mumbai

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H₂S sensing properties of pure and Al modified SnO₂ thin films prepared by RGTO method have been investigated. Both the sensor films exhibited maximum sensor response at an optimal operating temperature of 200°C. SnO₂ film modified with 5 nm thick Al exhibited higher and selective sensor response of 4.4 as compared to that of 2.1 for pure SnO₂ film towards 20 ppm of H₂S at an operating temperature of 200°C. Al modification enhanced the sensing characteristics due to spillover mechanism. © Anita Publications. All rights reserved.

Keywords: SnO₂, Al sensitizer, Gas sensor, H₂S, Metal oxides, Thin films

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Asian Journal of Physics Vol. 25 No 8, 2016,00-00

H₂S sensing behavior of MOS thin film of titanium oxide

Nagmani¹, T C Jagadale^1*, C L Prajapat¹, N S Ramgir¹, K P Muthe¹ and S C Gadkari¹

¹Technical Physics Division, Bhabha Atomic Research Centre, Mumbai- 400 085, India.

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We report the pulsed laser deposited titanium oxide thin film for H₂S sensing. These films were prepared on STO substrate using laser energy 500 mJ. The surface and bulk electronic structures were revealed using X-ray photo-electron spectroscopy technique, whereas the crystal quality and chemical composition of the film was investigated by X-ray diffraction. These films showed very good selectivity to H₂S with response of about ~ 760% at 250^oC operating temperature with much better response and recovery time. With increase in sensor operating temperature, response to H₂S has improved due to increase in number of active sites on the film surface which facilitates the chemisorptions of ambient oxygen. © Anita Publications. All rights reserved.

Keywords: SnO₂, Al sensitizer, Gas sensor, H₂S, Metal oxides, Thin films

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Asian Journal of Physics Vol. 25 No 8, 2016,00-00

NH₃ sensing properties of doped and co-doped TiO₂-polyaniline nanocomposite films

U V Patil^1,3, Niranjan S Ramgir^2*, R Jaiswal, N Patel, A K Debnath², K P Muthe², S K Gupta² and D C Kothari³

¹Wilson College, Chowpatty, Mumbai-400 007, India

²Technical Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085, India

³Department of Physics, University of Mumbai and National Centre for Nanosciences & Nanotechnology, Santacruz (E), Mumbai- 400 098, India

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Ammonia sensing properties of nanocomposite (NC) films of conducting polyaniline (PANI) intercalated with TiO₂, doped and co-doped with TiO₂ nanoparticles have been studied. The response characteristics of NC films towards different gases namely NH₃, CO, CO₂, and C₂H₅OH were examined at room temperature. Both pure PANI and NC films exhibited a selective response towards NH₃. It was observed that NC film exhibits better sensor response and response kinetics as compared to pristine PANI films. PANI intercalated with TiO₂ (PANI-TiO₂) NC film shows fourfold increase (76%) in response towards 50 ppm NH₃ as compared to threefold increase (65%) shown by pristine PANI sensor film. The PANI intercalated nitrogen doped TiO₂ (PANI-N4-TiO₂) NC film shows fivefold increase (80%) in response to 50 ppm ammonia. The response and recovery times of PANI-TiO₂ NC film are 6 and 370 s, respectively, while for PANI-N4-TiO₂ NC films were 2 and 670 s, respectively. These values are better than that exhibited by pristine PANI sensor film (6 and 960 s). The enhanced response kinetics is mainly attributed to the structural modification with high porosity and surface area of NC sensor film.© Anita Publications. All rights reserved.

Keywords: Conducting PANI, nanoparticles, nanocomposite (NC), Ammonia, Gas sensors

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Asian Journal of Physics Vol. 25 No 8, 2016, 977-983

Tailoring thermal conductivity in SnSe by AgSbTe₂ addition

Shovit Bhattacharya¹*, Mandira Majumder^{1, 2}, Ranu Bhatt¹, Sudhindra Rayaprol³, Ranita Basu¹, Anil Bohra¹, Ajay Singh¹ and D K Aswal¹

¹Technical Physics Division, B.A.R.C., Trombay, Mumbai- 400 085

²Department of Applied Physics, Indian School of Mines, Dhanbad- 826 004

³UGC-DAE CSR, Mumbai Center, R-5 Shed, BARC, Trombay, Mumbai-400 085

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Lead free materials have gained considerable interest in the field of Thermoelectrics due to environmental issues. SnTe is an interesting alternative to the well established PbTe as an efficient thermoelectric material, owing to similar electronic and structural similarity. Conversely, the biggest challenge in SnTe is the intrinsically high carrier concentration due to substantial Sn vacancies, which is extremely unlikely to be overcome by chemical substitutions. In this perspective, composites of (SnTe)_1-x(AgSbTe₂)_x [x = 0, 0.25, 0.5, 0.75 and 1] were prepared in order to tailor its thermal conductivity. In this paper we report the suppression of the thermal conductivity as a function of increasing concentration of AgSbTe₂ in the composite. © Anita Publications. All rights reserved.

Keywords: Thermoelectric material, thermal conductivity.

Total Refs: 8

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Asian Journal of Physics Vol. 25 No 8, 2016, 993-998

H₂S sensing properties of ZnO microcrystals having almond morphology

Savita Dange^1*, S N Dange², N S Ramgir³ and P S More¹

¹Department of Physics, The Institute of Science, M.C.Road, Fort, Mumbai-400 032, India

²Department of Physics, Jai Hind College, ‘A’ Road , Churchgate, Mumbai-400 020, India

³Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India

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Gas sensing properties of zinc oxide microcrystals having almond like morphology have been investigated towards H₂S gas. Uniform thin film of almond like microcrystals of zinc oxide was synthesised by using chemical bath deposition method at room temperature. The almond microcrystals show average tip size of about 100 nm and length of about 1.5 μm. The ZnO film was tested for H₂S gas having 50 ppm concentration for temperatures upto 300°C. The film showed highest percentage response at 250°C and fast response and recovery time at 300°C. The structural and optical properties of the ZnO film were characterized by X-ray diffraction (XRD), UV-Vis and Scanning electron microscopy (SEM). © Anita Publications. All rights reserved.

Keywords: Zinc oxide, Almond morphology, Micro crystals, H₂S gas sensor, Response time.

Total Refs : 15

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Actuators B: Chemical, 143(2009)164-170
13. Z.T.Liu, T.X.Fan, D. Zhang, X.L.Gong and J.Q.Xu, “ Hierarchically Porous ZnO with High Sensitivity and Selectivity to H2S Derived from

Biotemplates,” Sensors and Actuators B:Chemical, Vol.136, No.2, 2009, pp. 499-509.
14. R.B. Slimane, F.S. Lau, R.J. Dihu, M. Khinkis, Production of hydrogen by superadiabaticdecomposition of hydrogen sulfide, in: Proceedings of the

2002 US DOEHydrogen Program Review, NREL/CP-610-32405, 2013.
15. P.P.Sahay, R.K.Nath, Sensors and Actuators B 134 (2008) 654-659

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Asian Journal of Physics Vol. 25 No 8, 2016 1029-1036

A comparative study of the influence of vanadium pentoxide layer

on the ITO surface of organic light emitting diode

D Saikia* and R Sarma**

Thin Film Laboratory, Department of Physics, J. B. College, Jorhat, Assam, India

Pin code: 785001, Telephone: 8011468483, Fax:(0376)2300605

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In this paper the influence of vanadium pent oxide (V₂O₅) layer on the Tin-doped indium oxide (ITO) surface of organic light emitting diode has been reported. Here hole injection is directly affected by the different thicknesses of V₂O₅films on ITO surface. The ITO/V₂O₅(15 nm) bilayer anode shows better device performance compared to the bare ITO anode and that of the other thicknesses of V2O5 films. Enhanced device performance is due to the better transmittance property and lower surface resistivity of ITO/V₂O₅(15nm) bilayer anode combination. In this work N, N’-bis (3- methyl phenyl) - N, N’ (phenyl) -benzidine (TPD) is used as a hole transport layer and Tris (8-hydroxy quinolinato) aluminium (Alq3) as emitting layer. Our results indicate that the ITO/V₂O₅(15nm) bilayer anode is a better choice to enhanced the hole injection in OLED devices. Here we obtained maximum value of current and power efficiency as 5.6 Cd/A and 2.83 lm/W respectively. © Anita Publications. All rights reserved.

Keywords: Optoelectronics, Vanadium Pent oxide (V₂O₅), Indium tin oxide (ITO) and Figure of merit (FOM).

Total Refs : 23

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Prospect of molecular clocks
Masatoshi Kajita
National Institute of Information and Communications Technology
Koganei, Tokyo 184-8795, JAPAN
While uncertainties of some of the atomic transition frequencies have been reduced to the level of 10–8, the molecular transition frequencies are currently difficult to be measured with the uncertainty below 10–15. This is mainly because of the complicated energy levels of the molecules having the vibrational-rotational states. This paper lists some molecular transition frequencies, which can be measured with the uncertainties lower than 10–16. © Anita Publications. All rights reserved.

Asian Journal of Physics Vol. 25 No 8, 2016 00-00

Hydrothermally Grown SnO₂ -RGO nanocomposites for H₂ Gas Sensing Application

Bhagyashri Bhangare¹, Shweta Jagtap¹, Niranjan Ramgir², Dinesh Aswal², S.K.Gupta², Suresh Gosavi^1*

¹ Department of Physics, Centre for Advanced Studies in Material Science and Solid State Physics,

Savitribai Phule Pune University, Ganeshkhind, Pune-411007, India.

² Technical Physics Division, Bhabha Atomic Research Centre (BARC), Mumbai -400085, India

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The present paper describes the hydrothermal synthesis and characterization of reduced graphene oxide and tin oxide (SnO₂/RGO) based nanocomposites. This route have gain more attention due to the eco-friendly i.e reducing agent free reduction of graphene oxide (GO). The SnO₂/RGO nanocomposite was further used for hydrogen gas sensing application. The resultant gas sensor exhibits linear sensor response over the detectable range of 50-5000 ppm. In the present work, SnO₂/RGO nanocomposite shows higher sensor response (R_air/R_gas) of about 275 towards 5000 ppm along with quick response time of 5 s and complete recovery within 250 s. The results obtained from experimental measurements were combined with second order reaction equation and pseudo second order reaction equation in order to describe the interaction of hydrogen molecules with the surface of the sensing material. © Anita Publications. All rights reserved.

References

1. “ A novel sensing mechanism for resistive gas sensors based on layered reduced graphene oxide thin films at room temperature”, Yong Zhou, Yadong Jiang, Tao Xie, Huiling Tai, Guangzhong Xie, Sensors and Actuators B 203 (2014) 135–142.

2. “Clean and highly ordered graphene synthesized in the gas phase”, Albert Dato, Zonghoon Lee, Ki-Joon Jeon, Rolf Erni, Velimir Radmilovic,Thomas J. Richardsonc and Michael Frenklachd, Chem. Commun., 2009, 6095–6097.

3. “Sensing behavior of SnO₂/reduced graphene oxide nanocomposites toward NO₂” , Giovanni Neri, Salvatore Gianluca Leonardi, Mariangela Latino, Nicola Donato, Seunghwan Baek, Donato E. Conte, Patrícia A. Russo, Nicola Pinna, Sensors and Actuators B 179 (2013) 61– 68.

4. “Sensing behavior of SnO2/reduced graphene oxide nanocomposites toward NO2”, Giovanni Neri,Salvatore Gianluca Leonardi, Mariangela Latino, Nicola Donato, Seunghwan Baek, Donato E. Conte, Patrícia A. Russo, Nicola Pinna, Sensors and Actuators B 179 (2013) 61– 68.

5. “Chemical vapor deposition repairof graphene oxide: a to highly-conductive graphene monolayers”, Lopez V, Sundaram RS, Gomez-Navarro C, Olea D, Burghard M, Gomez-Herrero J, et al. Adv Mater 2009;21(46):46836.

6. “Catalytic hydrogen sensing using microheated platinum nanoparticle-loaded graphene aerogel”, Anna Harley-Trochimczyk, Jiyoung Chang, Qin Zhou, Jeffrey Dong, Thang Pham, Marcus A. Worsley, Roya Maboudian, Alex Zettl, Sensors and Actuators B 206 (2015) 399–406.

7. “Nanostructured Pt decorated graphene and multi walled carbon nanotube based room temperature hydrogen gas sensor”, Adarsh Kaniyoor, R. Imran Jafri, T. Arockiadoss and S. Ramaprabhu, Nanoscale, 2009, 1, 382–386.

8. “Hydrogen sensor based on a graphene – palladium nanocomposite”, Ulrich Lange, Thomas Hirsch, Vladimir M. Mirsky, Otto S. Wolfbeis, Electrochimica Acta 56 (2011) 3707–3712.

9. “Pd-WO₃/reduced graphene oxide hierarchical nanostructures as efficient hydrogen gas sensors”, Ali Esfandiar , Azam Irajizad , Omid Akhavan ,Shahnaz Ghasemi , Mohammad Reza Gholami, International journal of hydrogen energy 39(2014) 8169-8179.

10. “Hydrogen sensor based on graphene/ZnO nanocomposite”, Kanika Anand, Onkar Singh, Manmeet Pal Singh, Jasmeet Kaur, Ravi Chand Singh, Sensors and Actuators B 195 (2014) 409–415.

11. “A novel nanoporous Pd–graphene hybrid synthesized by a facile and rapid process for hydrogen detection”, Duy-Thach Phan, Gwiy-Sang Chung, Sensors and Actuators B 210 (2015) 661–668.

12. “Enhancing NO₂ gas sensing performances at room temperature based on reduced graphene oxide-ZnO nanoparticles hybrids”, Sen Liu, Bo Yu, Hao Zhang, Teng Fei, Tong Zhang, Sensors and Actuators B 202 (2014) 272–278.

13. “Palladium-Decorated Hydrogen-Gas Sensors Using Periodically Aligned Graphene Nanoribbons”, Yusin Pak, Sang-Mook Kim, Huisu Jeong, Chang Goo Kang,Jung Su Park, Hui Song, Ryeri Lee, NoSoung Myoung, Byoung Hun Lee, Sunae Seo, Jin Tae Kim, and Gun-Young Jung, ACS Appl. Mater. Interfaces 2014, 6, 13293−13298.

14. “Room temperature hydrogen gas sensing properties of Pt sputtered F-MWCNTs/SnO₂ network”, Shivani Dhall, Neena Jaggi, Sensors and Actuators B 210 (2015) 742–747.

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Asian Journal of Physics Vol. 25 No 8, 2016 00-00

Direct Synthesis of Calcium Nanospheres as Nanocarriers by Hydrothermal Method

Sneha M^a and Meenakshi Sundaram N^b

^aDepartment of Biomedical Engineering, PSG College of Technology,

Coimbatore 641004, Tamil Nadu, India

^bDepartment of Physics, Government Arts College (Autonomous), Salem-7, Tamil Nadu, India

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Calcium is an essential mineral for all living organisms especially for cell physiology. It also plays an important role in building stronger and denser bones. In this work, a simple, environmentally friendly method was employed for the preparation of hollow calcium nanospheres under hydrothermal conditions. Kapok fibers were used as templates and the synthesized nanomaterials are promising for applications such as daily dietary calcium intake for osteoporosis patients, drug delivery and other biomedical fields. © Anita Publications. All rights reserved.

Keywords: Calcium, nanospheres, hydrothermal, drug delivery

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ASIAN JOURNAL OF PHYSICS