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.

Surface enhanced Raman scattering investigation of two novel piperazine carbodithioic acids adsorbed on Ag and ZnO nanoparticles

Abstract: In this work piperazine-1-carbodithioic acid (PZCDT) and piperazine-1,4-dicarbodithioic acid (PZbCDT) were synthesized. These analytes PZCDT and PZbCDT have chair conformations, which is expected to give specific surface-enhanced Raman scattering (SERS) effects on individual bands. SERS, UV-Visible, TEM and DFT methods have proved that the dithiocarbamate moiety is a potential and suitable functional group for silver and ZnO nanoparticles (AgNPs and ZnONPs). The enhancement mechanism and enhancement factors in both SERS@AgNPs and SERS@ZnONPs are also discussed. Two new strong bands appear at 1630, 1286 cm−1 with very large intensity in SERS@AgNPs, which signifies the conversion of the C–N bond of the dithiocarbamate moiety into CN bonds. The SERS signatures that are observed are quite different in SERS@AgNPs and SERS@ZnONPs.

Surface enhanced Raman scattering based reaction monitoring of in vitro decyclization of creatinine → creatine

Abstract: Creatinine → creatine decyclization is an important reaction wherein we obtain a beneficial compound from a toxic substance. Decyclization of creatinine at basic pH has been monitored in vitro by time series surface enhanced Raman scattering (SERS) using a silver island film. NH2 scissoring, CN and CO stretching modes of creatinine serve as Raman markers for monitoring the decyclization reaction. Transition state calculations using DFT have revealed the path of the formation of creatine by the cleavage of the endocyclic CN bond of creatinine. The Raman signatures of ring opening are clearly observed after 120 min at pH 8, and further increasing the pH increases the reaction rate even more, as the signatures are observed after 60 and 30 min at pH 10 and 12, respectively; however, the reversibility of the reaction is more prominent at higher pH. Therefore, pH 8 is the most favorable among the three pH values for the decyclization reaction to be stable at room temperature. The proper understanding of this reaction where a toxic substance is converted to a beneficial compound is expected to open the scope for further extensive research.

Detection of in Vitro Metabolite Formation of Leflunomide: A Fluorescence Dynamics and Electronic Structure Study.

Abstract: The metabolic transformation of antirheumatic fluorescent drug leflunomide into its active metabolite teriflunomide through isoxazole ring opening has been monitored in vitro using steady state and time domain fluorescence spectroscopy and density functional theory. During metabolic reaction, absorption of leflunomide split into two bands resembling absorption spectra of teriflunomide. The fluorescence spectra reveal slow conversion of leflunomide to E and Z forms of teriflunomide in aqueous medium, which becomes faster at basic pH. The E form, which is more potent as a drug, becomes more stable with an increase in the basicity of the medium. Both molecules are associated with charge transfer due to twisting in the lowest singlet excited state. Excited state charge transfer followed by proton transfer was also observed in the Z form during the ring opening of leflunomide. Quantum yield and radiative decay rates have been observed to decrease for the metabolite because of an increase in nonradiative decay ...

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 …