Papers by Keyword: Fluorescence

Abstract: A new unsymmetrical photochromic diarylethene [1-(1,2-dimethyl-cyano-3-pyrrole)-2-(2-methyl-5-thienyl-3-thienyl] perfluorocyclopentene (1o) has been synthesized, and its photochromic reactivity, fluorescent were also investigated. The results showed this compound exhibited reversible photochromism, undergoing reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light in solution,Diarylethene 1 changed the color from colorless to purple upon irradiation with 297 nm UV light, in which absorption maxima were observed at 585 nm in hexane.

Abstract: A novel unsymmetrical isomeric photochromic diarylethene based on phenanthrene unit, {1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-{2-methyl-5-[4-(2-(1,3-dioxolane)) phenyl]-3-thienyl}} perfluorocyclopentene (1o), was designed and synthesized. Its properties were investigated in detail, including photochromic, kinetics and fluorescent. The results showed that the compound exhibited excellent photochromism, changing from colorless to violet after irradiation with UV light in 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 fluorescence intensity of the photochromic diarylethene 1o declined dramatically.

Abstract: Four novel cross-linked network conjugated poly (methacrylic acid) functionalized poly (9-aminofluorene) films were prepared by a precursor polymer approach, i.e., poly { poly [ N - (9H-fluoren-9-yl) methacrylamide ] } (P1), poly { poly [ N - (9H-fluoren-9-yl) methacrylamide-co-methacrylic acid ] } (P3), poly { poly [ N - (9H-fluoren-9-yl) methacrylamide] -co-9-aminofluorene } (P2) and poly { poly [ N - (9H-fluoren-9-yl) methacrylamide-co-methacrylic acid ] -co-9-aminofluorene } (P4). As-prepared polymer films had good redox activity and structure stability in concentrated sulfuric acid. Fluorescence spectra indicated that the soluble cross-linked polymers were good blue light emitters and in solid state they were blue-green light emitters.

Abstract: Eu (BA)3phen/PVP fluorescent nanofibers has been successfully fabricated based on PVP and europium complexes Eu (BA)3phen (BA = benzoic acid, phen = phenanthroline) via electrospinning technology. The as-prepared samples were characterized by field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and fluorescence spectroscopy (FS). The as-prepared Eu (BA)3phen/PVP nanofibers possess good fibrous morphology, smooth surface and narrow size distribution. The average diameter of nanofibers was about 250 nm. Under the excitation of 274-nm ultraviolet light, Eu (BA)3phen/PVP nanofibers exhibit red emissions of predominant peaks at 592 and 616nm, which are respectively attributed to the 5D0 →7F1 and 5D0→7F2 energy levels transitions of Eu3+ ions. The optimum mass percentage of Eu (BA)3phen to PVP is 15%. The fluorescent nanofibers are expected to apply in the fields of lasers, displays, amplifiers for optical communication, and medical imaging, etc.

Abstract: A novel gadolinium diethylenetriamine-N, N-bis (2-acetamide benzoic acid)-N, N-bisacetic acid complex has been synthesized and characterized by elemental analysis, infrared spectrum, ultraviolet spectroscopy and thermal analysis. The interaction between Gd³⁺ and aminopolycarboxlicacid ligand was investigated by fluorescence titration. The binding constant of this complex is calculated to be 1.2018×10⁴ L·mol^-1, and binding stoichiometry is 1:1. Fluorescence spectra was also used to study the interaction between Gd (III) complex and bovine serum album (BSA). The results showed that Gd (III) complex can effectively quench the intrinsic fluorescence of BSA via static quenching. According to Stern-Volmer equation and Linewerver-Burk equation, the binding constant is calculated to be 3.7491×10⁴ L·mol^-1 and binding site is about 1.0.

Abstract: The major hurdles faced by therapeutic biomolecules to reach clinical use are non-specificity, unnecessary side effects, sensitivity to environmental factors and poor cellular uptake. Several nanoparticle systems have been developed to overcome these issues but there are still some bottlenecks such as nanoparticle toxicity, bioavailability and inability to track the biomolecules post-delivery. Here we report the use of multi-functional lanthanide-based fluorescent upconversion nanoparticles as a safe delivery vector for peptides as well as for fluorescent tracking of delivery or for in-vitro/in-vivo imaging. The UCNs are excited by a NIR light source and emit in the Visible region. Since NIR light is used for excitation, the nanoparticles could be used for deep tissue imaging. Highly monodisperse uniformly sized, sub-100 nm, biocompatible upconversion nanoparticles were synthesized with a mesoporous silica coating. Amanitin, a peptide toxin was used as a model peptide and was loaded onto the mesoporous silica coated UCNs. The peptide loaded UCNs were delivered to B16F0 melanoma cells and significant cell death was achieved within 24 hours. The unloaded UCNs however had negligible toxicity. The UCNs were also used for imaging the cells with very good signal-to-noise ratio and almost nil background autofluorescence. The fluorescence from the UCNs was non-blinking, highly stable and could be used for long-term tracking.

Abstract: It is found that the fluorescence of curcumin is greatly enhanced by La³⁺ in the prescence of sodium dodecyl benzene sulfonate (SDBS). Based on this, a sensitive fluorimetric method for the determination of curcumin in aqueous solution is proposed. In the HOAc-NaOAc buffer, the fluorescence intensity of curcumin is proportional to the concentration of curcumin in the range of 0.0074-7.4μg·mL^-1 and the detection limit is 3.66ng·mL^-1. The actual samples are satisfactorily determined.

Abstract: We demonstrated a model to realize the growth of indium-silver alloy nanocrystals in borosilicate glass by sol-gel method. The presence of spherical indium-silver alloy nanoparticles with 5 nm average grain size and finely dispersed form in borosilicate glass was confirmed by transmission electron microscopy imaging. Reduction of indium-silver ions to indium-silver alloy neutral nanoparticles was revealed through X-ray powder diffraction and X-ray photoelectron spectra. Remarkably, Indium-silver alloy nanocrystal-borosilicate glass exhibited fluorescence at around 423 nm.

Abstract: It is a facile and efficient way to produce grapheme quantum dots (GQDs) through photo-Fenton reaction. However, the fluorescence of the as-generated GQDs is weak. Here, bright yellow-green fluorescent graphene quantum dots (GQDs) were prepared by post-oxidation of the GQDs with H₂O₂. The fluorescence quantum yields of the post-oxidized GQDs (O-GQDs) increased from 0.08% to 3.3% and the maximum emission wavelength shifted from 450 to 510 nm. The O-GQDs exhibit excitation-independent and pH-dependent photoluminescence behaviors. The increase of the photoluminescence intensity is attributed to the more carbonyl and carboxyl groups after the post-oxidation. The post-oxidation treatment offers a simple pathway to enhance the fluorescence of GQDs.

Abstract: A new coumarin derivative 8-Dimethylaminomethyl-7-hydroxy-chromen-2-one (C₁₂H₁₃NO₃, M = 219.23) were prepared and characterized by single-crystal X-ray diffraction. The compound crystallized in methyl alcohol system. The crystal belongs to the Monoclinic system, space group P2₁/C, with a = 10.228(2) Å, b = 8.9260(18) Å, c = 12.064(2) Å, α = 90°, β = 91.85(3)°, γ = 90°, M = 219. 23, V = 1100.8(4) ų, Z = 4, Dc = 1.323 g/cm³, μ=0.096 mm^-1, F(000) = 464, R = 0.0594 and wR = 0.1611. A total of 2136 unique reflections were collected, of which 2020 with I > 2(I) were observed. The quantum chemistry calculation study on the title compound has been performed by quantum chemical method in SVWN5/6-31G^** level. Additionally, IR, ¹HNMR spectra, thermal analysis and the fluorescent properties are discussed .