AJP	ISSN : 0971 – 3093 Vol  21,  No. 1 , January-March, 2012

 

Vol. 21, No 1 (2012) 1-15

Advances in Metamaterial Research

 

Subal Kar and Madhuja Ghosh

Institute of Radio Physics and Electronics

Beginning in 1968 with the theoretical proposition of Left-handed Material (LHM) possible with simultaneous negative permittivity and permeability, and with the first successful experimental demonstration of negative refractive index realized with plasmonic LHM in 2001; the research in LHM or more popularly in metamaterials in the following years is just phenomenal. In this paper we would begin with a brief review on the fundamental building blocks for two basic types of metamaterials viz.: the plasmonic and transmission line type; followed by our research work on the design and experimental characterization of plasmonic metamaterial successfully done first time in India. Then we would give some snap shots of milestone developments in metamaterial research, especially giving the glimpses of the problems and possibilities of such efforts in terahertz and optical frequency regime. Finally, we would indicate the emerging trends of research in metamaterials in this decade looking forward even to quantum metamaterials.

 Vol. 21, No 1 (2012) 17-24

LIBS: In-Situ monitoring tool for analysis of samples in different phases

 

Rohit Kumar¹, Rahul Agrawal², Ashok Kumar Pathak¹,

Abhimanyu Kumar Singh³ and Awadhesh Kumar Rai¹

¹Department of Physics, University of Allahabad, Allahabad-211002, India

²Centre of Food Technology, University of Allahabad, Allahabad-211002, India

Laser Induced Breakdown Spectroscopy (LIBS) has received much attention due to its versatility for the monitoring of the different types of the materials (samples) in any phase. In the present paper in-situ capability of LIBS has been demonstrated to the samples in two different phases in solid and liquid. We have performed the LIBS analysis on the new age Indian coins (solid samples) of the different years, rice husk (plant sample) and tap water (liquid samples). We have used one of the multivariate analysis named as Principal Component Analysis (PCA) to classify the coins of different years. The PCA analysis gives principal components PC1 (95%), and PC2 (5%), which explains the total variance present in data set. LIBS coupled with PCA has potential of rapid classification/ identification of the samples. The LIBS analysis of rice husk has also been performed and the spectral signatures of essential minerals like Mg, Si, Fe, Na, K, Ca alongwith organic elements C N, H, O are observed. The in-situ analysis of tap water and water with chromium impurity has been demonstrated to detect toxic metals in liquid samples.

Keywords: in-situ, LIBS, coin, liquid, rice husk.

 Vol. 21, No. 1 (2012) 25-32

Direct analysis of trace elements in coal by means of laser-induced breakdown spectroscopy (LIBS)

 

Nasrullah Idris^1,2*, Muliadi Ramli², Mahidin³, Rinda Hedwig⁴, Marincan Pardede⁵,
Maria Margaretta Suliyanti⁶, Koo Hendrik Kurniawan⁷

¹Syiah Kuala University, Faculty of Mathematics and Natural Sciences, Department of Physics,

Jl. Syech Abdurrauf No. 3 Darussalam, 23111 Banda Aceh, Aceh, Indonesia

²Syiah Kuala University, Tsunami Disaster and Mitigation Research Center (TDMRC) , Department of Applied Research,

Jl. Tgk. Abdur Rahman, Gampong Pie, Kecamatan Meuraxa, Banda Aceh, Aceh, Indonesia

³Syiah Kuala University, Faculty of Mathematics and Natural Sciences, Department of Chemistry,

Jl. Syech Abdurrauf No. 3 Darussalam, 23111 Banda Aceh, Aceh, Indonesia

⁴Syiah Kuala University, Faculty of Engineering, Department of Chemical Engineering, Jl. Syech Abd.

Rauf No. 7 Darussalam, Banda Aceh 23111, Aceh, Indonesia

⁵Department of Computer Engineering, Bina Nusantara University, 9 K. H. Syahdan, Jakarta 14810, Indonesia

⁶Department of Electrical Engineering, University of Pelita Harapan, 1100 M. H. Thamrin Boulevard,

Lippo Village, Tangerang 15811, Aceh, Indonesia

⁷Research Center for Physics, Indonesian Institute of Sciences, Kawasan PUSPITEK,

Serpong, Tangerang Selatan 15314, Banten, Indonesia

Trace element inherently presents in coal including heavy metal, therefore the mining and the use of coal posing hazard to environment and to health living things. In this study, heavy metal detection in Aceh coal’s has been made using emerging analytical tool, namely laser-induced breakdown spectroscopy (LIBS) to investigate the capability of this technique in analyzing trace element in complex matrices such as coal. The LIBS system used in this work is composed by a laser system (Nd-YAG Laser (1,064 nm; 500 mJ; 8 ns), and optical detecting system (1,000 mm focal length f/8.6 Czerny-Turner) equipped with intensified charge coupled device (CCD) 1024×256 pixels, 26-mm square (960 x 256 active pixels). The laser beam was focused onto coal sample surface with a focusing lens of +250 mm. The emission from the created plasma was then collected by a fiber optics and sent to the spectrograph. The coal samples were taken from Aceh Jaya and Aceh Barat Regency region. As the results, it was found that several heavy metal can clearly be detected in Aceh coals, such as Mn, As, suggesting Aceh coal contains heavy metal elements and that LIBS technique can potentially be used to analyze the presence of heavy metal in coal samples. In addition, these results also suggest that LIBS technique can be used to study comparatively the content of heavy metal elements in coal samples coming from different geographic origins.

Keywords: LIBS, trace element, heavy metal, coal, geographic origin, Aceh coal.

 Vol. 21, No. 1 (2012) 33-40

Study of ionospheric modulations due to solar flares over Ahmedabad

 

Som Sharma1, H Chandra¹, N Y Pandya², Hari Om Vats¹ and Rajmal Jain¹

¹Physical Research Laboratory, Navrangpura, Ahmedabad – 380 009, India

Earth’s ionosphere responds quickly to the enhanced X-rays and ultraviolet (UV) radiation emitted from the Sun during solar flares. Regular radio soundings of the ionosphere over Ahmedabad (23°N, 72.4°E) using KEL digital Ionosonde for the period 1997-2000 are used to study the influences of the excess X-ray emission during solar flares. Based on the X-ray spectral characteristics of the flares we have examined the variation in the minimum frequency of reflection, fmin, which is an indicator of the excess ionization/absorption in D-region of ionosphere. The studies of the excess absorption, due to the solar flares, in the D-region of ionosphere over Ahmedabad are made for a number of solar flare events during 1997-2000. Correlation study between fmin and X-ray flux during solar flares shows good correlation. An empirical relation has been established between fmin and D-region electron density using different Solar flares events over Ahmedabad and changes in electron density estimated for several solar flare events. Ionospheric E region showed 27% increase in electron density as compared to control day during solar flare event on 12 May 1997 over Ahmedabad.

Keywords: Solar flares; Ionospheric absorption; D-region.

 Vol. 21, No. 1 (2012) 41-50

Dielectric and AC conductivity behavior of barium and strontium modified BFN ceramics by impedance spectroscopy for device applications

 

N K Singh¹, Pritam Kumar¹, D Kumar¹ and S Sharma²

¹University Department of Physics, V K S University, Ara-802 301, India

Recently a new wave of interest has risen on relaxor ferroelectrics with complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline samples of Ba(Fe0.5Nb0.5)O3 (BFN), 0.93Ba(Fe0.5Nb0.5)O3-0.07BaTiO3 (BFN-BT) and 0.93Ba(Fe0.5Nb0.5)O3-0.07SrTiO3 (BFN-ST) were prepared by a high temperature solid-state reaction technique. Studies of structural and microstructural characterizations were performed by X-ray diffraction (XRD) and Scanning electron microscope (SEM) techniques. X-ray studies reveal that the materials have monoclinic structure at room temperature. Dielectric properties were measured over a wide range of temperature (30- 420°C) and frequency (100- 1MHz). The frequency-dependent electrical data are also analyzed in the framework of conductivity and impedance formalisms. Relaxation phenomena of non-Debye type have been observed in the above ceramics, as confirmed by the Cole–Cole plots.

Keywords: Perovskite oxides; dielectric constant; electrical properties; tangent loss; X-ray diffraction; scanning electron micrographs.

 Vol. 21, No. 1 (2012) 51-58

Influence of substrate temperature on the performance of copper phthalocyanine based organic thin film transistors

 

N Padma*, P Veerender, Shaswati Sen and SK Gupta

Thin Films and Devices Section, Technical Physics Division,

Bhabha Atomic Research Centre,

The effect of substrate temperature maintained during deposition of copper phthalocyanine film that is used as active layer, on the performance of organic field effect transistors was studied. Mobility and drain current modulation (Ion/Ioff) was found to increase with increase in substrate temperature upto 150°C but reduced for deposition temperature of 225°C. The results have been understood in terms of change in crystallinity and morphology of the films. Subthreshold swing, which indicates efficient turn on of the device, is minimum for films deposited at temperatures of 100-150°C. Hysteresis in transfer characteristics and hence threshold voltage shift was maximum for the film deposited at 225°C. This is attributed to large gaps between the widely scattered nanowires formed at this temperature, through which moisture and oxygen from ambient could diffuse into the film upto the interface causing charge trapping.

 Vol. 21, No.1 (2012) 59-70

Density functional theory studies on molecular structure of
4-methoxy-4-methyl-2-pentanone

 

A Jayaprakash ^*1, V Arjunan² and S Mohan³ 

¹Department of Physics, Rajiv Gandhi College of Engineering and Technology, Puducherry – 607 402

²Department of Chemistry, Kanchi Mamunivar Centre for Post-Graduate Studies, Puducherry – 605 008

The most stable geometry of 4-methoxy-4-methyl-2-pentanone has been obtained from the potential energy surface scan. Vibrational and electronic properties are computed from the stable geometry obtained using DFT/B3LYP methods and correlated with the experimental data. The electronic exchange interaction and charge delocalisation of the molecule have been determined by natural bond orbital (NBO) analysis. Molecular electrostatic surface potential (MESP), total electron density distribution and frontier molecular orbitals (FMO’s) are constructed at B3LYP/6-311++G** level. Furthermore, a detailed vibrational assignment and analysis of the title compound has been carried out by using FTIR and FT-Raman spectral data. The observed and the calculated frequencies are found in good agreement with each other.

Keywords: 4-methoxy-4-methyl-2-pentanone; FTIR; FT-Raman; DFT; MESP; NBO. 

Total Refs : 29

 Vol. 21, No. 1 (2012) 71-82

Quantum chemical studies on the molecular structural, thermodynamic and vibrational properties of 2,3-dimethyl-1,3-butadiene

 

A comparative study on the optimised geometrical parameters, infrared and Raman intensities, thermodynamic properties and vibrational frequencies of 2,3-dimethyl-1,3-butadiene (DMBD) obtained by quantum mechanical methods with the experimental FTIR and FT-Raman data are presented in this work. The FTIR and FT-Raman spectra of DMBD have been recorded in the region 3700-400 cm-1 and 3700-100 cm-1, respectively. A detailed assignment and analysis of the fundamental vibrational modes of the molecule were carried out. The observed fundamental modes have been compared with the harmonic vibrational frequencies calculated from the optimised geometry of the molecule using DFT/B3LYP method by utilising 6-311++G** and cc-pVTZ basis sets. Molecular electrostatic potential, total electron density distribution and frontier orbital energy levels are constructed to realise the electronic properties. The temperature dependence of the thermodynamic parameters were also determined by B3LYP method.

Keywords: 2,3-Dimethyl-1,3-butadiene, B3LYP, HOMO, LUMO, MESP.

Total Refs :  34

 

 Vol. 21, No. 1 (2012) 83-94

Vibrational spectroscopic and DFT studies of cis– and trans-1,3-pentadiene

 

Theoretical quantum chemical and experimental spectroscopic studies of cis- and trans-1,3-pentadiene have been carried out by using DFT/B3LYP methods, FTIR and FT-Raman spectral techniques. The geometry of the compounds have been optimized by B3LYP method with 6-311++G** and cc-pVTZ basis sets. The geometrical parameters obtained at B3LYP levels have been compared with the experimental values. Molecular electrostatic potential surface, total electron density distribution and frontier molecular orbitals are constructed at B3LYP/6-311++G** level to understand the electronic properties. The charge density distribution and site of chemical reactivity of the molecules have been obtained by mapping electron density isosurface with electrostatic potential surfaces. The HOMO and LUMO energies and their energy gap were measured by time-dependent DFT approach.

FT-IR and FT-Raman spectra of trans-1,2-dimethoxy ethylene have been experimentally reported in the region 3400-400 cm–1 and 3400-100 cm–1, respectively. The optimised geometric parameters, electronic and thermodynamic properties, normal mode frequencies and corresponding vibrational assignments of trans-1,2-dimethoxy ethylene (C4H8O2) have been theoretically examined by means of hybrid density functional theory (DFT) B3LYP method together with 6-311G and 6-311++G** basis sets. Besides, reliable vibrational assignments have made on the basis of computed potential energy distribution (PED). The scaled vibrational frequencies are found to coincide with the experimentally observed values with acceptable deviation. Comparison between the experimental and theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational frequencies. Molecular electrostatic potential, total density distribution and frontier orbital energy levels are simulated to understand the electronic properties. The B3LYP method has also been used to calculate the thermodynamic parameters at various temperatures.

The vibrational frequencies of the molecule 3,4-dichlorobenzophenone (DclBP) have been obtained from the FT-IR and Raman spectral data. The frequencies are also theoretically evaluated based on the density functional theory (DFT) using the standard B3LYP/6-311+G(d, p) method and basis set combination. On the basis of potential energy distribution calculated with MOLVIB program, the assignments for the various frequencies are attempted. To obtain closer agreement between theoretical and experimental values, a scaling factor adjustment is also carried out. The final analysis and assignments of the various vibrational modes are reported. The values of the electric dipole moment (m) and the first-order hyperpolarizability (b) of the investigated molecule were computed using ab initio quantum chemical calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The first electronic transition energy is evaluated. The theoretical FT-IR and Raman spectra for the title molecule have also been constructed. NBO analysis useful to understand the intramolecular hyperconjugative interactions is carried out. Mulliken’s net charges have been calculated and compared with atomic natural charges.