Eun-Mi Lee

Hemicyanine-based colorimetric chemosensors: Different recognition mechanisms for CN− sensing

Simple hemicyanine dyes were synthesized by a classical condensation reaction. The structures of these dyes were characterized by (1)H NMR spectroscopy, elemental analysis, and FAB-Mass spectrometry. The sensing behavior of the hemicyanines towards a selection of anions was investigated by UV-vis absorption spectroscopy. These structurally simple dyes displayed a rapid response and high selectivity for cyanide ion over other common anions in the DMSO/H(2)O solution. Different sensing mechanism of the dyes to cyanide ion were confirmed by (1)H NMR studies, together with theoretical calculations based on DFT and PPP-MO methods. These dyes show no colorimetric response for other anions investigated.

Squarylium-based chromogenic anion sensors

A squarylium (SQ) dye was synthesized by the reaction between squaric acid and 2,3,3-trimethylindolenine and its anion sensing properties were investigated using absorption and emission spectroscopy. This chemosensor exhibited high selectivity for CN(-) as compared with F(-), CH(3)CO(2)(-), Br(-), H(2)PO(4)(-), Cl(-), and NO(3)(-) in acetonitrile, which was attributed to the formation of a 1:1 squarylium:CN(-) coordination complex, the formation of which was supported by the calculated geometry of the complex.

Switching properties of fluorescent photochromic poly(methyl methacrylate) with spironaphthoxazine and D-π-A type pyran-based fluorescent dye

Fluorescent photochromic poly(methyl methacrylate) (PMMA) with spironaphthoxazine (SPO) and D-π-A type pyran-base fluorescent dye as a fluorophore was synthesized by typical free radical copolymerization. The poly(MMA-co-SPO-co-fluorophore) in both solution and solid film exhibited excellent photoregulated fluorescence switching behavior and reversible modulation of fluorescence intensity using alternating irradiation with UV and visible light. The poly(MMA-co-SPO-co-fluorophore) also showed viscosity and conductivity switching behaviors along with photoresponse.

Properties and characteristics of squarylium-based chemosensors for Hg2+

A chemosensor based on symmetrical squarylium (SQ) dye, 2,4-bis((3,3-dimethylindolin-2-ylidene)methyl)cyclobutane-1,3-bis(olate), was synthesised and its cation-sensing properties in acetonitrile were investigated by UV–vis spectroscopy. Upon the addition of Hg2+, the solution of SQ dye showed clear colour change. The absorption studies also indicate a higher affinity of Hg2+ towards the formation of 2:1 complexes, which is in good agreement with the experimental results. The selective detection of Hg2+ of the symmetrical-SQ unit gave rise to a significant absorption decrease at λmax 650 in acetonitrile solution.

Luminescence switching of CdTe quantum dots in presence of water-soluble spironaphthoxazine

The typical reaction of spironaphthoxazine is the conversion between the non-polar spiro form and polar merocyanine form. Quantum dots (QDs) have unique optical properties and several advantages over conventional organic dyes. In this work, the CdTe QDs containing a water-soluble spironaphthoxazine was used as the optical probe photoisomerization between spiro and merocyanine. The initial bright fluorescence of CdTe QDs was effectively quenched by water-soluble spironaphthoxazine using UV irradiation. Reversible modulation of fluorescence intensity of CdTe QDs was achieved using alternating irradiation with UV and visible light. The possible mechanism is discussed.

Fluorescence quenching of carbazole by 2-chloro-3,5-dinitrobenzotrifluoride-ethylamines intermolecular charge-transfer complex

The interaction between carbazole and 2-chloro-3,5-dinitrobenzotrifluoride-ethylamines, (mono-, di-, and triethylamine) charge-transfer complex in DMSO was studied using fluorescence spectroscopy. The positive deviation from linearity has been observed in the Stern-Volmer plots. The experimental results showed that the fluorescence of carbazole was quenched by 2-chloro-3,5-dinitrobenzotrifluoride-ethylamines charge-transfer complex through a combined quenching procedure. The Stern-Volmer quenching constants, K(SV), have been determined and found to be greater quenching efficiency of ethylamine. Carbazole/2-chloro-3,5-dinitrobenzotrifluoride loaded PMMA film was exposed to ethylamine vapor, where the resulting absorption and emission changing properties were clearly monitored.

Temperature-modulated quenching and photoregulated optical switching of poly(N-isopropylacrylamide)/spironaphthoxazine/Rhodamine B hybrid in water.

Temperature and photo-responsive poly(N-isopropylacrylamide) (PNIPAM)/spironaphthoxazine (WSPO)/Rhodamine B (RhoB) hybrid was studied in this paper. Aqueous PNIPAM/WSPO/RhoB hybrid showed phase transition and fluorescent decrease by rising temperature. And also color and fluorescent change of aqueous PNIPAM/WSPO/RhoB hybrid were showed upon UV/vis light.

Optical properties of photo- and thermo-responsive aqueous CdTe quantum dots/spironaphthoxazine/poly(N-isopropylacrylamide) hybrid

Temperature and photo-responsive aqueous CdTe quantum dots (QDs)/spironaphthoxazine (WSPO)/poly(N-isopropylacrylamide) (PNIPAM) hybrid was studied in this paper. Phase transition and fluorescent decrease were observed in aqueous QDs/WSPO/PNIPAM hybrid by rising temperature, and color and fluorescent switching were also observed upon irradiation of UV/Vis light.

Ionic comonomer effect of poly(N-isopropylacrylamide) copolymer containing D-π-A type pyran-based fluorescent dye

Temperature and pH responsive poly(N-isopropylacrylamide) (poly(NIPAM)) copolymer containing D-π-A type pyran-based fluorescent dye (fluorophore) and basic comonomer, N-[3-(dimethylamino)propyl]-methacrylamide (DMAPAM) was prepared by free radical polymerization. With increase of pH values, aqueous poly(NIPAM-co-DMAPAM-co-fluorophore) solution showed decrease of a lower critical solution temperature (LCST) and increase of fluorescence intensity, due to a change in the ionization state. And also hydrodynamic radius of poly(NIPAM-co-DMAPAM-co-fluorophore) changed correspondingly to changes of temperature and pH values.

pH Triggered Dye Chemosensor: Design, Synthesis and Optical Switching Properties

A novel dye chemosensor based on indole as a donor unit and quinaldium as an acceptor unit have caused promising optical changes when used as a reversible, pH-induced, molecular switching in the presence of alkali/acid stimulus. The dye chemosensor also exhibited marked fluorescence quenching in the presence of alkali addition, which are based on intramolecular charge transfer (ICT) system.The level of energy potential and the electron flowing of this dye chemosensor such as HOMO and LUMO values were calculated by computational calculation approaches.