Ranjan K. Singh

Bio: Ranjan K. Singh is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Raman spectroscopy & Liquid crystal. The author has an hindex of 20, co-authored 134 publications receiving 1465 citations. Previous affiliations of Ranjan K. Singh include Schiller International University & University of Würzburg.

Crystal → nematic phase transition in the liquid crystalline system 1‐isothiocyanato‐4‐(trans‐4‐propylcyclohexyl) benzene (3CHBT) probed by temperature‐dependent micro‐Raman study and DFT calculations

Abstract: Raman spectra of 3CHBT in unoriented form were recorded at 14 different temperature measurements in the range 25–55 °C, which covers the crystal nematic (N) phase transition, and the Raman signatures of the phase transition were identified. The wavenumber shifts and linewidth changes of Raman marker bands with varying temperature were determined. The assignments of important vibrational modes of 3CHBT were also made using the experimentally observed Raman and infrared spectra, calculated wavenumbers, and potential energy distribution. The DFT calculations using the B3LYP method employing 6-31G functional were performed for geometry optimization and vibrational spectra of monomer and dimer of 3CHBT. The analysis of the vibrational bands, especially the variation of their peak position as a function of temperature in two different spectral regions, 1150–1275 cm−1 and 1950–2300 cm−1, is discussed in detail. Both the linewidth and peak position of the (CH) in-plane bending and ν(NCS) modes, which give Raman signatures of the crystal N phase transition, are discussed in detail. The molecular dynamics of this transition has also been discussed. We propose the co-existence of two types of dimers, one in parallel and the other in antiparallel arrangement, while going to the nematic phase. The structure of the nematic phase in bulk has also been proposed in terms of these dimers. The red shift of the ν(NCS) band and blue shift of almost all other ring modes show increased intermolecular interaction between the aromatic rings and decreased intermolecular interaction between two NCS groups in the nematic phase. Copyright © 2009 John Wiley & Sons, Ltd.

Detection of Malachite Green in Water Using Edge Excited Label Free Fluorescent Probe NCQDs.

Abstract: The fluorescent properties of nitrogen doped carbon quantum dots (NCQDs) prepared through microwave assisted green method has been used as label free fluorescent probe for selective and sensitive detection of malachite green (MG) in water The optical responses revealed that the NCQDs are highly stable and have good fluorescent quantum yield The NCQDs were used to detect the Malchite Green in Mili Q water Reduction in the fluorescence response was monitored in the range 1712–12843 μM of MG dissolved in Mili Q water Linear response was observed in the range, 10–80 μM The calculated value of limit of detection is 516 μM and the sensitivity is (003536 ± 000001) μM−1 The future application of this work is that it can be employed to detect MG in the tap water and other natural sources of water

Surface-enhanced Raman spectroscopy (SERS): progress and trends

Abstract: Surface-enhanced Raman spectroscopy (SERS) combines molecular fingerprint specificity with potential single-molecule sensitivity. Therefore, the SERS technique is an attractive tool for sensing molecules in trace amounts within the field of chemical and biochemical analytics. Since SERS is an ongoing topic, which can be illustrated by the increased annual number of publications within the last few years, this review reflects the progress and trends in SERS research in approximately the last three years. The main reason why the SERS technique has not been established as a routine analytic technique, despite its high specificity and sensitivity, is due to the low reproducibility of the SERS signal. Thus, this review is dominated by the discussion of the various concepts for generating powerful, reproducible, SERS-active surfaces. Furthermore, the limit of sensitivity in SERS is introduced in the context of single-molecule spectroscopy and the calculation of the 'real' enhancement factor. In order to shed more light onto the underlying molecular processes of SERS, the theoretical description of SERS spectra is also a growing research field and will be summarized here. In addition, the recording of SERS spectra is affected by a number of parameters, such as laser power, integration time, and analyte concentration. To benefit from synergies, SERS is combined with other methods, such as scanning probe microscopy and microfluidics, which illustrates the broad applications of this powerful technique.

Solar-driven reforming of lignocellulose to H 2 with a CdS/CdO x photocatalyst

Abstract: This work was supported by the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and the National Foundation for Research, Technology and Development), the OMV Group (to E.R.), the EPSRC (DTA studentships for D.W.W. and T.E.R), the Isaac Newton Trust, the German Research Foundation (to M.F.K.), the World Premier Institute Research Center Initiative (WPI), MEXT, Japan (to K.L.O.) and a Marie Curie Research fellowship (to K.H.L., GAN 701192 - VSHER).

Organic Photoreceptors for Imaging Systems

Abstract: Xerographic photoreceptors charge acceptance and dark discharge photoinduced discharge photogeneration theories photogeneration in organic solids charge transport theories charge transport in polymers and related materials experimental techniques photoreceptor preparation photoreceptors fatigue summary and future requirements.

Assessing Genetic Risks: Implications for Health and Social Policy

Abstract: Ed Lori B Andrews, Jane E Fullarton, Neil A Holtzman, Arno G Motulsky National Academy Press, £28.95, pp 338 ISBN 0-309-04798-6 Genetic screening tends to serve as a flypaper on which our hovering fears of a Brave New World alight and stick. In the future of all-conquering genetic technology, who should be screened for what and by whom? Here is a dense report, compiled by a committee of the great and the good, with hundreds of recommendations for action and inaction. How much …