Vol 27 No 5

Asian Journal of Physics Vol. 27 No 5, (2018), 257-263

Raman spectroscopy of interlayer vibrational modes in AB-stacked and twisted multilayer graphenes

Miao-Ling Lin^{1, 2} and Ping-Heng Tan^{1, 2,*}

¹State Key Laboratory of Superlattices and Microstructures,

Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China

²CAS Center of Excellence in Topological Quantum Computation, and College of Materials Science

and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China

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The interlayer coupling in multilayer graphenes (MLGs) can be tuned by various stacking configurations, such as common AB-stacking, ABC-stacking and even the twisted multilayer graphene (tMLG). The interlayer shear and breathing coupling can be probed by the interlayer shear (C) modes and layer breathing (LB) modes. Here we first revealed the interlayer shear coupling in MLG by the C modes. In tMLG, the C and LB modes are detected by resonant Raman spectroscopy. The shear interlayer coupling at the interface are 20% of the coupling in the AB-stacked layers, whereas the LB coupling at the interface is similar to that between the AB-stacked layers. This is because that the periodicity mismatch between two twisted layers mostly affects shear interactions. The different couplings for C and LB modes at the interface of tMLG provides a way to identify the layer number of the constituents and the total layer number of tMLG, respectively, which open the doors to identifying the stacking configurations of MLG grown by chemical vapor depositions. © Anita Publications. All rights reserved.

Keywords: Shear modes; Layer breathing modes; interlayer coupling; multilayer graphene; twisted multilayer graphene

Total Refs: 32

Asian Journal of Physics Vol. 27 No 5, (2018), 265-276

Binary cosolvent effect on hydrogen bonding network of bulk water

Deepak Tomar¹ and Kailash Chandra Jena^1,2,*

¹Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140 001, India

²Center for Biomedical Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India

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The binary mixtures of water with alcohol are ubiquitous for various fundamental biological processes and many industrial applications. Hydrogen bonding structure of bulk water determines the properties of the binary alcohol-water mixtures. However, it still remains a puzzle how alcohols interact and change the hydrogen bonding network of the bulk water in the binary aqueous solutions. In the current study, we are investigating the molecular level changes in the hydrogen bonding network of water molecules induced by hydrophobic and hydrophilic cosolvents. In order to probe the hydrophobic and hydrophilic induced impacts, we have selected methanol–water and D₂O–water binary solutions. We have employed attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to probe the molecular vibrational dynamics within the aqueous solutions. Red-shift in the OH-stretch region has been observed with the increase in mole fraction of methanol which is an indication of formation of stronger hydrogen bonding environment in the methanol-water binary solutions. However, blue-shifts have been observed in the OH-stretch region with the increase in D₂O mole fraction in the D₂O–water binary solutions. The blue shifts have been attributed to the formation of weaker hydrogen bonding network of the bulk water molecules in the binary solutions.© Anita Publications. All rights reserved. © Anita Publications. All rights reserved.

Keywords: ATR-FTIR spectroscopy; Hydrogen bonding; Binary mixture; Hydrophobic hydration

Total Refs : 63

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Asian Journal of Physics Vol. 27 No 5, (2018), 279-285

Exploring Superconductivity in Graphene based Materials

Ankur Pandya¹ and Prafulla K Jha²

¹Institute of Technology, Nirma University, Ahmedabad-382481, India.

²Department of Physics, Faculty of Science,TheM.S.University of Baroda, Vadodara-390002, India.

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This article reviews the fundamental theoretical predictions and the possibility of empirical occurrence of superconductivity in graphene based materials. Graphene being a monoatomic thick carbon allotrope, has unusual two-dimensional Dirac-like electronic excitations. The graphene based superconductors may provide the breakthrough in the development of high T_c superconductivity as electrically, intrinsic graphene has the highest carrier mobility of known materials with massless Dirac electrons.Tunnelling and confinement of electrons result into elusive behavioural patterns. Hence, the manifestation of superconductivity in graphene based materials, the possible solutions utilizing theoretical and experimental aspects are presented. © Anita Publications. All rights reserved.

Keywords: Nanostructures, Graphene; Superconductivity

Total Refs : 76

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Asian Journal of Physics Vol. 27 No 5, (2018), 287-310

Vibrational spectroscopic, quantum chemical and molecular docking studies on

diethyl 2, 4-dimethylpyrrole-3, 5-dicarboxylate

R Premkumar¹, Shamima Hussain², S Christopher Jeyaseelan¹, T Mathavan¹, A Milton Franklin Benial¹, M A Palafox³ and V K Rastogi⁴

¹PG and Research Department of Physics, N M S S V N College, Madurai-625 019, India.

²UGC-DAE CSR, Kalpakkam Node, Kokilamedu - 603 104, India.

³DepartamentodeQuímica-FísicaI,FacultaddeCienciasQuímicas,UniversidadComplutense, Madrid 28040, Spain

⁴Indian Spectroscopy Society, KC 68/1, Old Kavinagar, Ghaziabad-201 002, India.

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Potential energy surface scan was performed and the most stable molecular structure of the Diethyl 2, 4-dimethylpyrrole-3, 5-dicarboxylate (EMPC) molecule was predicted. The most stable molecular structure of the molecule was optimized using DFT/B3LYP method with cc-pVTZ basis set. The structural parameters and vibrational wavenumbers were calculated for the optimized molecular structure. The FT-IR and FT-Raman spectra of the molecule were recorded in the solid state. The experimental and theoretical results were compared and vibrational bands are assigned. UV-Visible spectrum of the molecule was simulated and validated with the experimental results. The electronic properties like HOMO and LUMO energies were obtained by TD-DFT calculations. The stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been studied using natural bond orbital (NBO) analysis, which confirms the bioactivity of the EMPC molecule. The molecular electrostatic potential surface was simulated and Fukui function calculations were also carried out to investigate the reactive nature of the EMPC molecule. The molecular docking analysis reveals that the better inhibitory nature of the EMPC molecule against the histone deacetylases 6 (HDAC-6) enzyme which overexpressed in oral squamous cell carcinoma (OSCC). The title molecule may act as a potential inhibitor against OSCC. These results pave the way for the development of drug designing in the treatment of OSCC. © Anita Publications. All rights reserved.

Keywords: Diethyl 2, 4-dimethylpyrrole-3, 5-dicarboxylate; Vibrational spectroscopy; Density functional theory, Bio-activity; Molecular docking; oral squamous cell carcinoma.

Total Refs : 71

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Asian Journal of Physics Vol. 27 No 5, (2018), 311-316

Structural and magnetic characterization of zinc ferrite nanoparticles

Rintu Mary Sebastian^a* and E M Mohammed^b

^aDepartment of physics, Morning Star Home Science College, Angamaly

^bResearch Department of Physics, Maharaja’s College, Ernakulam, Kerala, India

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Nanosized zinc ferrite (ZnFe₂O₄) was synthesized by Sol – Gel technique using ethylene glycol as the reducing agent. The present investigation aims to study the structural as well as magnetic properties of the prepared sample. The specimen was characterized using FTIR, XRD, SEM, EDAX and VSM. The single phase spinel structure of the sample was tested using XRD and FTIR. The particle size and strain were calculated from Hall – Williamson plot. The H – M plot of the Sol – Gel synthesized nano zinc ferrite showed very low value of coercivity and almost zero value of retentivity indicating that it is superparamagnetic. The superparamagnetic nature of the samples makes it suitable for various biomedical applications. © Anita Publications. All rights reserved.

Keywords: Zinc ferrite, FTIR, EDAX, Spinel structure

Total Refs : 10

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ASIAN JOURNAL OF PHYSICS