Non-hydrothermal synthesis and optical limiting properties of one-dimensional Se/C, Te/C and Se-Te/C core-shell nanostructures

Sridharan, K.,Ollakkan, M.S.,Philip, R.,Park, T.J. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.63 No.-

A single step, nontoxic, non-hydrothermal, low temperature and reproducible method for the preparation of carbon-coated selenium and tellurium nanowires (Se/C and Te/C, respectively), and selenium-telluride (Se-Te/C) nanorods, is presented. Sodium dodecyl sulfate is used as the surfactant, and glucose is employed as the reducing and carbonizing agent. Uncoated nanowires of trigonal Se and Te without the carbon shell are obtained as products, at lower glucose concentrations, whereas at higher glucose concentrations carbon-coated nanowires of trigonal Se and Te are formed. Structural, morphological and compositional properties of the prepared products are examined using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy, respectively. The formation of amorphous carbon shell and the model depicting the growth of core-shell nanowires and nanorods are discussed on the basis of the experimental results. Nonlinear optical transmission of the samples is studied at 532nm using the open-aperture Z-scan technique employing 5ns laser pulses. Results show that the samples are efficient optical limiters, and that a three-to-four-fold enhancement in the value of the effective two-photon absorption coefficient (β) can be achieved by coating the nanowires and nanorods with carbon.

Anomalous growth of multi-phased and multi-dimensional Manganese oxide-Metal (Fe, Co and Ni) oxide nanostructures: Synthesis and optical limiting properties

Sridharan, K.,Roy, N.,Philip, R.,Park, T.J. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.611 No.-

A single step approach toward the hydrothermal synthesis of Manganese oxide-Metal (Fe, Co and Ni) oxide nanocomposites (Mn-O, Fe-MnO, Co-MnO and Ni-MnO) is demonstrated. The composites are prepared using precursors such as potassium permanganate, urea and metal chlorides which are abundant in nature, making this a cost effective and environmentally benignant synthetic route. An anomalous growth was observed in the prepared composites, which had a minimum of two major phases with two different morphologies such as nanowires, nanorods, nanoplates and nanosheets. Growth mechanism of the composite nanostructures is predicted from morphological characterizations. Linear optical studies reveal the broad band visible light absorbance of the composites. Open aperture z-scan experiments are conducted at 532nm using 5ns laser pulses to study the optical limiting properties of the composites. The anomaly observed in the growth, demonstrates the possibility of fabricating multi-phased composites with multi-dimensional nanostructures, which can be employed in the cost effective design and development of optical limiters and sensors based on manganese and other transition metal oxides.

Nonlinear Optical Investigations in Nine-Atom Silver Quantum Clusters and Graphitic Carbon Nitride Nanosheets

Sridharan, Kishore,Sreekanth, P.,Park, Tae Joo,Philip, Reji American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.28

<P>Absorption saturation due to surface plasmon resonance affects the optical limiting efficiency of metal nanoparticles (NPs) by raising the limiting threshold to higher laser fluences. It has been shown that in gold, compared to the larger NPs, smaller quantum clusters (QCs) exhibit better optical limiting with lower limiting thresholds due to the absence of absorption saturation. Here we report optical limiting properties of two novel materials, namely, nine-atom silver (Ag<SUB>9</SUB>) QCs and graphitic carbon nitride (GCN) nanosheets. The relatively large nonlinear absorption of Ag<SUB>9</SUB> QCs compared to Ag NPs is revealed from open-aperture Z-scan measurements carried out using 532 nm, 5 ns laser pulses. Optical nonlinearity in the QCs arises mostly from free carrier absorption and a relatively weak saturable absorption. The superior limiting efficiency of Ag<SUB>9</SUB> QCs is complemented by excellent chemical stability, which makes silver quantum clusters ideal candidates for optical limiting applications. The two-dimensional sheet-like structure of GCN is ideal for grafting metals and semiconductors, and we show that even though the nonlinearity of pristine GCN is low it can be improved substantially by grafting lightly with Ag<SUB>9</SUB> QCs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-28/acs.jpcc.5b02372/production/images/medium/jp-2015-023727_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b02372'>ACS Electronic Supporting Info</A></P>

Fabrication of flexible SWCNT thin films through electrohydrodynamic atomization technique and investigation of their electrical properties

Sridharan, S.,Choi, K.H. North-Holland 2014 Materials letters Vol.115 No.-

In this article, we report the application of a non-vacuum based direct printing technique of electrohydrodynamic atomization (EHDA) for the deposition of single-walled carbon nanotube (SWCNT) thin films of 90nm thickness onto flexible polyethersulfone (PES) substrates. The optimization of EHDA process to achieve a stable cone jet for the uniform deposition of SWCNT thin films is discussed in detail. The physico-chemical characterization of SWCNT thin films has been carried out using X-ray diffraction, UV-vis spectroscopy and Fourier-transform infra red spectroscopy techniques. The field emission scanning electron microscope studies revealed the surface morphology of SWCNT thin films. Further, the electrical study of the SWCNT thin films exhibited a linear ohmic behavior at room temperature as well as at elevated temperatures.

A NON-MARKOVIAN EVOLUTION MODEL OF HIV POPULATION WITH BUNCHING BEHAVIOUR

Sridharan, V.,Jayshree, P.R. 한국전산응용수학회 1998 Journal of applied mathematics & informatics Vol.5 No.3

In this paper we propose a model of HIv population through method of phases with non-Markovian evolution of immi-gration. The analysis leads to an explicit differnetial equations for the generating functions of the total population size. The detection process of antibodies (against the antigen of virus) is analysed and an explicit expression for the correlation functions are provided. A measure of bunching is also introduced for some particular choice of parameters.

Superior Photostability and Photocatalytic Activity of ZnO Nanoparticles Coated with Ultrathin TiO₂ Layers through Atomic‐Layer Deposition

Sridharan, Kishore,Jang, Eunyong,Park, Young Min,Park, Tae Joo WILEY‐VCH Verlag 2015 Chemistry Vol.21 No.52

<P><B>Abstract</B></P><P>Atomic‐layer deposition (ALD) is a thin‐film growth technology that allows for conformal growth of thin films with atomic‐level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO<SUB>2</SUB> layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO<SUB>2</SUB> layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO<SUB>2</SUB> nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO<SUB>2</SUB> coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO<SUB>2</SUB> coatings (≈0.75–1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO<SUB>2</SUB>, and the photocatalytic activity to that of pure ZnO.</P>

A NUMERICAL METHOD FOR SOLVING THE FREDHOLM INTEGRAL EQUATION OF THE SECOND KIND

Sridharan, V.,Jayashree, P.R. 한국전산응용수학회 1998 Journal of applied mathematics & informatics Vol.5 No.2

The numerical method is used to solve the Fredholm integral equation of the second kind with weak singular kernels using the Toeplitz matrices. The solution has a computing time requir-ment of O(N2) where 2N+1 is the number of discretization points used. Also the error estimate is computed. Some numerical Exam-ples are computed using the Mathcad package.

Computational Analysis of Human Chemokine Receptor Type 6

Sridharan, Sindhiya,Saifullah, Ayesha Zainab,Nagarajan, Santhosh Kumar,Madhavan, Thirumurthy The Basic Science Institute Chosun University 2018 조선자연과학논문집 Vol.11 No.2

CXCR6 is a major target in drug design as it is a determinant receptor in many diseases like AIDS, Type I Diabetes, some cancer types, atherosclerosis, tumor formation, liver disease and steatohepatitis. In this study, we propose the active site residues of CXCR6 molecule. We employed homology modelling and molecular docking approach to generate the 3D structure for CXCR6 and to explore its interaction between the antagonists and agonists. 3D models were generated using 14 different templates having high sequence identity with CXCR6. Surflex docking studies using pyridine and pyrimidine derivatives enabled the analysis of the binding site and finding of the important residues involved in binding. 3D structure of CXCL16, a natural ligand for CXCR6, was modelled using PHYRE and protein - protein docking was performed using ClusPro. The residues which were found to be crucial in interaction with the ligand are THR110, PHE113, TYR114, GLN160, GLN195, CYS251 and SER255. This study can be used as a guide for therapeutic studies of human CXCR6.

Experimental Investigation of Drilling Characteristics of Jute Fiber Reinforced Graphene Filled Epoxy Nanocomposites

Sridharan Veerapuram,Muthukrishnan Nambi,Raja Thimmarayan 한국고분자학회 2018 폴리머 Vol.42 No.4

Natural fiber reinforced composite has been the topic of recent studies and is preferred in various fields of engineering for the specific properties and bio-friendly nature. Surface modification of the natural fibers has been recommended to achieve good bonding. The performance of fiber reinforced polymer composites has been enhanced by the addition of nanofillers. The present work investigates the effect of surface modification of fibers by alkali treatment and the surface roughness and drilling forces in jute fiber reinforced nano-phased epoxy composite are also studied by changing the content of graphene. Graphene has enhanced the quality of hole in nanocomposites.

Rule of Law Indicators in Context: An Empirical Evaluation of GTZ Legal Advisory in Beijing

Vishnu Sridharan (사) 이준국제법연구원 2009 Journal of East Asia and International Law Vol.2 No.2

Much has been written about the general ability (or lack thereof) of international development organizations to effectively monitor and evaluate the impact of their Rule of Law projects on the ground. However, less research has focused on particular development organizations’methods of project evaluation, the politics behind them and their strengths and weaknesses. This paper offers such an analysis of the evaluation methods of GTZ Legal Advisory in Beijing. After describing the work of GTZ in general and its Legal Advisory in particular, the paper offers a detailed evaluation of the tools that it uses to gauge the impact of its projects on the ground. What is gained from such a particularized analysis is a deeper understanding of both the donor politics and organizational tradeoffs inherent in monitoring and evaluation decisions, two factors often given insufficient attention in more theoretical discussions.