Papers by Keyword: Fluorescence

Abstract: Highly bright-fluorescent N (nitrogen), S (sulfur) co-doped graphene quantum dots (GQDs) were synthesized through an modified hydrothermal method. The doped GQDs are smaller than 10 nm in size in average and stable in aqueous solution. Unlike many reports on graphene oxide (GO), the as-synthesized doped GQDs exhibit bright blue photoluminescence (PL) emission and the emission wavelength is excitation-independent. The intriguling results indicate that GQDs may have great potential in the optic and optoelectronic applications.

Abstract: In this paper, the bio-based aliphatic copolyamide (bio-based PA) was synthesized by bio-based diacids and diamines, and Eu (TTA)3phen of Lanthanide complexes was synthesized. Then bio-based polyamide/rare earth composite fibers were prepared by electrospinning method. The structure and properties of the electrospun composite fibers were characterized by fluorescence photometer, x-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The results showed that, with the increase of the content of rare earth, the fluorescent intensity of bio-based polyamide/rare earth composite fibers first increased, and then decreased. When the content of rare earth was 10%wt, the fluorescence property of the electrospun composites was best.

Abstract: A new photochromic diarylethene based on a phenanthrene, which is named 1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-[2-methyl-5-(4-formylphenyl)-3-thienyl] perfluorocyclopentene, was designed and constructed successfully. At the same time, its photochromic properties, kinetics and fluorescence switch were investigated in detail. The results indicated that its photochromic behaviors could be modulated by UV/Vis light, changing from colorless to blue in dichloromethane solution. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. Furthermore, the optical switch experiment illustrated that the diarylethene 1o functioned as a remarkable fluorescent switch.

Abstract: A new unsymmetrical photochromic diarylethene compound, 1-(2-methyl-3-benzofuranyl)-2-[2-methyl-5-(2-methyl-6-pyridyl)-3-thienyl] perfluorocyclopentene (1o), was synthesized and its photochemical, fluorescence properties were investigated systematically both in solution and PMMA amorphous film. The photochromic reaction kinetics results indicated that the cyclization processes of 1o belong to the zeroth order reaction and the cycloreversion process belong to the first order reaction.

Abstract: A new unsymmetrical photochromic diarylethene, 1-[2,4-dimethyl-5-thiazolyl]-2-[2-methyl-5-(3-4-trifluoromethylphenyl)-3-thienyl] perfluorocyclopentene (1o) was synthesized, and its properties, such as photochromism in solution as well as in poly-methylmethacrylate (PMMA) amorphous film, and fluorescence properties were investigated in detail. The results showed the compound exhibited good photochromism in hexane solution and in PMMA amorphous film, the maxima absorption of its closed-ring isomer 1c are 490 nm and 495 nm respectively. The open-ring isomer of the diarylethene 1o exhibited relatively strong fluorescence at 449 nm in hexane solution (2 × 10^-5 mol/L) when excited at 330 nm and at 438 nm in PMMA amorphous film when excited at 280 nm. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light.

Abstract: A new photochromic diarylethene compound 1-(1,2-dimethyl-7-azaindole-3-yl)-2-[2-methyl-5-(4-chlorphenyl)-3-thienyl] perfluorocyclopentene (1o) was synthesized, which properties were systematacially studied. The results showed that its absorption maxima were observed at 583 nm in hexane and at 597 nm in a PMMA film, respectively, upon irradiation with 297 nm UV light. Moreover, the diarylethene showed a remarkable fluorescence switches upon irradiation with UV and visible light.

Abstract: A new unsymmetrical photochromic diarylethene compound, 1-(2-Methyl-3-benzothiophene)-2-(5-(4-ethynyl)-2-methylthiophen-3-yl)Perfluorocyclopentene (1o),was synthesized and its photochemical, fluorescence properties were investigated systematically both in solution and PMMA amorphous film. The results showed that this compound exhibited reversible photochromism, changing from colorless to pink after irradiation with 297 nm UV light both in solution and in PMMA amorphous film. The photochromic reaction kinetics indicated that the cyclization processes of 1 belong to the zeroth order reaction and the cycloreversion process belong to the first order reaction.

Abstract: A novel photochromic diarylethene based on a six-membered pyrimidine moiety 1-(2,4-dimethoxyl-5-pyrimidinyl)-2-[2-methyl-5-(4-n-pentylbenzene)-3-thienyl] perfluorocyclopent-ene has been synthesized. Its properties, including photochromic behavior and fluorescent properties, have been investigated. The compounds exhibited remarkable photochromism, changing from colorless to red after irradiation with UV light both in solution and in PMMA film. The fluorescence had a remarkable initial increase with subsequent dramatic decrease with increasing concentration. The results indicated that the pyrimidine moiety played a very important role during the process of photoisomerization reactions.

Abstract: An asymmetrical photochromic diarylethene 1-(2,4-dimethyl-5-thiazolyl)-2-(2-methyl-5-(2-methyl)-3-thienyl) perfluorocyclopentene (1o) was synthesized and its photochromic properties were investigated. Upon irradiation with 297 nm UV light, 1o exhibited photochromism in solution and in PMMA film. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. Moreover, diarylethene 1o also exhibited obviously fluorescence switches along with the photochromism.

Abstract: A new asymmetry photochromic diarylethene based on a phenanthrene, which is named 1-{2-methyl-[5-(4-methylene-hydroxyl) phenyl]-3-thienyl}-2-[2-methyl-5-(10-phenanthrenyl)-3-thi-enyl] perfluorocyclopentene 1o, was designed and constructed successfully. And its properties have been discussed systematically, including photochromic, HPLC, concentration effect and fluorescent switch. The result indicated that its photochromic behaviors could be modulated by UV/Vis light, changing between colorless and violet in dichloromethane solution, respectively. What’s more, it could also response to various concentrations, with emission maximum density 5 × 10^-5 mol L^-1. In addition, the optical switch experiment illustrated that the diarylethene 1 functioned as a remarkable fluorescent switch, which fluorescent modulation efficiency was 63% in the photostationary state.