Shengmei Song

Synthesis and spectral characteristics of two novel intramolecular charge transfer fluorescent dyes

The synthesis and absorption/fluorescence properties of two novel intramolecular charge transfer (ICT) compounds of (fluorene-2-yl)-(9-ethylcarbazole-3-yl) ketene and 1-phenyl-3-(fluorenone-2-yl)-5-(9-ethylcarbazole-3-yl)-2-pyrazoline were reported. The primary structure of the target compounds was characterized by IR and (1)H NMR. The systems contained a fluorenone or a propenon group as an electron acceptor (A) and an N-ethylcarbazole and a pyrazoline group as electron donors (D). From the emissive properties it was concluded that the electronic coupling between D and A was sufficient to allow charge transfer in these molecules. The ICT maximal emission displayed a large wavelength shift and Stokes shifts increased in response to the increase of the solvent polarity. The highly solvatochromic properties made the two compounds of great interest as new classes of fluorescent probes, electroluminescent and electrofax materials.

Carbon-based dots co-doped with nitrogen and sulfur for Cr(VI) sensing and bioimaging

Less toxic elements nitrogen and sulfur co-doped carbon-based dots (NSCDs) have been prepared by microwave-assisted pyrolysis of citric acid and N-acetyl-L-cysteine as the carbon source and N,S-dopant, respectively. The structure and optical properties of NSCDs are characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, elemental analysis, Fourier transform infrared spectroscopy, UV-vis absorption, and photoluminescence spectroscopy. The mechanism for the formation of NSCDs is also discussed. The as-prepared NSCDs show small size distribution and excellent dispersibility. Their strong blue fluorescence is observed when the excitation wavelength is between 260 nm and 380 nm. Moreover, they exhibit high tolerance to various external conditions including external cations, pH values, and continuous UV excitation. More strikingly, as the emission of NSCDs is efficiently quenched by Cr(VI), the as-prepared NSCDs are employed as a highly sensitive and selective probe for Cr(VI) detection. The linear range is 0.5–125 μM Cr(VI) with the detection limit 20 nM. The as-synthesized NSCDs have been successfully applied for Cr(VI) sensing and cell imaging.

Studies on the interaction between vanillin and β -Amyloid protein via fluorescence spectroscopy and atomic force microscopy

Abstractβ-Amyloid(Aβ) plaques and intracellular neurofibrillary lesions in the brain are markers of Alzheimer’s disease(AD). The ability to safely decrease Aβ concentrations is potentially important as a preventive strategy for AD. The interactions between vanillin and Aβ polypeptide were investigated via fluorescence spectroscopy and atomic force microscopy(AFM). The results of fluorescence and synchronous spectroscopies illustrate that the intrinsic fluorescence of tyrosine(Tyr) residues in Aβ1-42 aggregates can be quenched strongly upon the formation of vanillin-Aβ1-42 complex. Thioflavine T(ThT)-induced fluorescence changes indicated that Aβ1-42 aggregates could be disaggregated by vanillin, and the AFM images of Aβ1-42 enunciated the depolymerization of Aβ1-42 aggregates by vanillin in a dose-dependent manner. Vanillin may be a potential pharmacological agent for the treatment of AD.