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The synergy of CHEF and ICT toward fluorescence ‘turn-on’ probes based on push-pull benzothiazoles for selective detection of Cu2+ in acetonitrile/water mixture
(2021-06-15)
Nootem, Jukkrit
;
Daengngern, Rathawat
;
Sattayanon, Chanchai
;
Wattanathana, Worawat
;
Wannapaiboon, Suttipong
New push-pull schiff base ligands based on benzothiazole (BZ) unit were developed for the selective detection of Cu2+ through fluorescence ‘turn-on’ mechanism. These derivatives with electron withdrawing trifluoromethyl (-CF<inf>3</inf>) and cyano (-CN) substituents (BZ2 and BZ3) demonstrated a prominent fluorescence enhancement upon copper ion binding which could be the results from the synergistic effect between the chelation-enhanced fluorescence (CHEF) and the intramolecular charge transfer (ICT) processes. In addition, these compounds displayed 1:1 binding with Cu2+ with low limits of detection of 0.77 μM and 0.64 μM for BZ2 and BZ3, respectively, in acetonitrile-water (3:1 v/v) media. The electronic and photophysical properties of these BZ ligands and the copper ion complexes were modelled by the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) calculations, respectively. Analysis of X-ray absorption spectra probed at Cu K-edge of Cu2+-BZ mixtures revealed the complex formation of BZ ligands with the targeted Cu2+ and confirmed the non-centrosymetric structures of the complexes as predicted by the DFT calculation. The electron density distributions of the HOMO-LUMOs in the computational results as well as large stokes shifts of the ligand-metal complexes in the experimental data confirmed the strong ICT effect after Cu2+ binding which is a key process promoting fluorescence ‘turn-on’ mechanism.
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Review article: Mechanism of resonant enhancement of gold- and copper-nanowires arrays
(2014-01-01)
Locharoenrat, Kitsakorn
Although second harmonic generations from gold- and copper-nanowires have been the subject of extensive studies, a complete understanding of the mechanism of the enhancement is still missing. The aim of review article is to address these issues by performing systemic studies of mechanism of the resonant enhancements between gold- and copper-nanowires in terms of surface reconstruction and relativistic effect, and implements these types of candidate for the potential applications in optical communications and optical devices. © (2014) Trans Tech Publications, Switzerland.
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Effects of three parameters on graphene synthesis by chemical vapor deposition
(2013-09-02)
Dathbun, Ajjiporn
;
Chaisitsak, Sutichai
A high quality graphene film on a copper foil was successfully grown by a CVD process using ethanol as a carbon source. The effect of growth temperatures (650-850°C), reaction times (5-50 min) and post-CVD cooling process rates (slow-cooling, fast-cooling and fast-cooling under ethanol exposure) on the formation of graphenes was investigated by Raman spectroscopy and scanning electron microscopy (SEM). The graphene film deposited under the optimal conditions showed features of a high quality such as a high I <inf>2D</inf>/I<inf>G</inf> ratio of ∼8, a low I<inf>D</inf>/I<inf>G</inf> ratio of 0.28 and a narrow full width half maximum (FWHM) of Lorentzian-shaped 2D peak of ∼35 cm-1. It was found that the quality of graphene film could be enhanced by optimizing the growth temperature and time, while the number of graphene layer was less sensitive to the cooling rate. However, the fast cooling process under ethanol exposure was found to be a key process for obtaining graphenes with a large domain size. These findings may help to fabricate high-quality graphenes on a copper foil for electronic applications. © 2013 IEEE.
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Copper nanowires on NaCl (110) template
(2013-04-29)
Locharoenrat, Kitsakorn
We studied optical properties of copper nanowires fabricated by a shadow deposition method. We found that the optical absorption spectra of thinner nanowires exhibited stronger anisotropic absorption than thickner nanowires. Absorption maxima are located at lower photon energy when incident field is parallel to the wire axes than they are perpendicular to each other. They also shift to lower energy when the widths of nanowires are increased. © (2013) Trans Tech Publications, Switzerland.
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Biosorption of copper by spent yeast immobilized in sodium alginate beads
(2009-12-01)
Apinthanapong, Muanmai
;
Phensaijai, Mongkol
Spent yeast from the brewing industry was immobilized with sodium alginate and used in a study on biosorption of Cu(II). Kinetic models were developed using pseudo-first and -second order equations and tested for the sorption of Cu(II). The results showed that the sorption of Cu(II) onto immobilized spent yeast in sodium alginate beads could be described by a pseudo-second order model, which had high correlation coefficients (r<inf>2</inf>). The rate constant (k<inf>2</inf>) and the initial sorption rate (h) were calculated. The values of the rate constants were found to decrease from 0.208 to 0.037 g/mg min with an increase in the initial concentration of Cu(II) from 20 to 80 ppm. The initial sorption rate increased from 0.014 to 0.037 mg/g min as the initial concentration of Cu(II) was varied from 20 to 80 ppm. The observed dependence of the sorption rate on the initial concentration of Cu(II) indicated that the removal of Cu(II) was more rapid when the initial concentration of the solution was high.

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