Browsing by Author "Epperla, Chandra Prakash"

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A fully-aqueous red-fluorescent probe for selective optical sensing of Hg2+ and its application in living cells
(2016-07)
Pola, Murali Krishna
;
Raju, Mandapati V. Ramakrishnam
;
Lin, Chein-Ming
;
Putikam, Raghunath
;
Lin, Ming-Chang
A new red-fluorescent mercury ion sensor material is designed and synthesized, which is composed of at weezer-shaped hydrophilic probe containing bifurcated soft-base atoms N and S coupled with 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) unit. By virtue of the strong electron-accepting nature of TCF unit (as a push pull chromophore), this designed sensor material can selectively detect Hg2+ over various tested metal ions in a 100% aqueous medium via naked-eye and photoluminescence (PL) observations. Theoretical and time-resolved photoluminescence measurements further confirmed the selectivity and reversibility of the probe towards Hg2+ via intramolocular charge transfer mechanism in this sensor material. Moreover, the living cell tests by confocal fluorescence images of this sensor material towards Hg2+ were also investigated. Finally, distinguished absorption changes and fluorescence quenching spectral appearances allowed us to present the selective optical indicator of Hg2+ via TCF moiety for the first time. (C) 2016 Elsevier Ltd. All rights reserved.
Carbon structure in nanodiamonds elucidated from Raman spectroscopy
(2017-09-01)
Korepanov, Vitaly I.
;
Hamaguchi, Hiro-o
;
Osawa, Eiji
;
Ermolenkov, Vladimir
;
Lednev, Igor K.
Despite their name, nanodiamonds (ND) are comprised of a complex interplay of different carbon phases. The diamond core is surrounded by the shell consisting mostly of disordered sp(3) carbon and graphene-like carbon (GLC). The complex structure makes the characterization of nanodiamonds (ND) a difficult challenge. Recent development of many varieties of NDs for different applications demands quick and reliable characterization of the content of various carbon fragments, as well as the estimation of the diamond core size. In this work, we apply Raman spectroscopy to study the structure of nanodiamonds from different origins, including those produced by detonation (DND), high pressure high temperature synthesis (HPHT), and pulsed laser irradiation (LND). The relative content of GLC, disordered and surface carbon can be easily determined from Raman spectra. In particular, we show how the content of different structure fragments is changed upon de-agglutination, surface oxidation and ion irradiation. We also compare the different ND production methods in terms of the structural uniformity of the nanoparticles. Raman spectroscopy provides unique quantitative tool for ND characterization; we believe that the present data will be useful for understanding the structure of diamond nanoparticles, and will provide the background for obtaining the NDs with desired properties. (C) 2017 Elsevier Ltd. All rights reserved.