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141.
Debaki Ghosh Souradeep Basu Monisha Singha Joyee Das Prabuddha Bhattacharya Amit Basak 《Tetrahedron letters》2017,58(21):2014-2018
Three crescent shaped heterocycle-fused phenanthrene based systems 1–3 have been synthesized starting from benzene (or substituted benzene) 1,2-bis-propargyl alcohols. Bis-alkylation with propargylic bromides provided the key intermediate, the bis-propargyl bis-ethers. In spite of the possibility of many competing reactions, the latter underwent facile double Garratt-Braverman cyclization to provide compounds 1–3 in near quantitative yield, in a striking reaction involving the formation of four C–C bonds in a single step. Compounds 1–3 showed binding interaction with DNA, predominantly, via groove binding along with partial intercalation (combilexins). Molecular docking study supported the proposed binding modes. 相似文献
142.
Xu Tang Juan Han Yun Wang Liang Ni Longhua Li Lei Wang Wenli Zhang 《Tetrahedron》2017,73(10):1367-1373
A new on-off fluorescent probe 1 for Cu2+ based on Schiff base compound was designed and synthesized by one-step reaction. The single probe 1 exhibited strong green fluorescence emission. A fluorescence quenching effect and faint color change were observed as soon as the Cu2+ was added to the probe system in H2O/EtOH (v/v = 8:2, HEPES buffer, 0.05 M, pH = 7.4) solution. Other common metal cations did not cause the changes in the fluorescence and color of the probe 1. The optical properties were studied by the fluorescence emission and UV–Vis spectra. Meanwhile, the geometry optimizations of probe 1 and the [1-Cu2+] coordination complexes were also carried out by DFT using the Gaussian 09 program, in which the B3LYP function was used. Based on experimental measurement and theoretical analysis, we can know that the combination ratio of the probe and Cu2+ is 2:1 and the limit of detection (LOD) is as low as 5.3 × 10?9 M Besides, the probe 1 was also used to analyze the Cu2+ in living cells. 相似文献
143.
144.
Biphenyl derivative N-allyl-N′-(4′-nitro[1,1′-biphenyl]-4-yl)thiourea (BP1) was synthesized as a functional fluorescent sensor for protons and their photophysical properties were studied. The influence of environment protonation on photophysical properties of the biphenyls in solutions was investigated using UV absorption, steady-state and time-resolved fluorescence spectroscopy. Semi-empirical and DFT calculations and optimization of the molecular structure of the biphenyl derivatives in vacuum, in polar solvents and in a proton-rich environment were conducted using the HyperChem, Amsol and Gaussian3 software package. Fluorescence quenching with addition of acidic acid was observed and the Stern-Volmer quenching rate constant was about 3.0×109 M−1 s−1. Intermolecular hydrogen bonds formations by the protons with the sulphur being substituted to the biphenyls generate charge movement and strong increase (×5) of the dipole moment of the fluorophore. 相似文献
145.
A. Morozov T. Heindl J. Wieser R. Krücken A. Ulrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):51-57
Continuous and pulsed 12 keV electron beams were used to excite nitrogen
within a gas cell at pressures ranging from 10 to 1400 hPa. The pressure
dependence of the ratio of photon fluxes for emission from vibrational
levels v'=0 and 1 of the C 3Π u state has been studied. The
results confirm the presence of a collisional excitation mechanism
populating v'=0, 1 in addition to electron impact excitation. Rate constants
of (1.27 ±0.04)×10-11 cm3s-1 [ v'=0] and
(2.68 ±0.08)×10-11 cm3s-1 [ v'=1] were measured for
C 3Π u quenching by ground state nitrogen. For electron beam
conditions relative excitation efficiencies of 1:0.59:0.22 for
vibrational levels 0, 1 and 2 were calculated. The recorded flux ratios are
compared with the predictions given by a vibrational relaxation model. 相似文献
146.
Chris D. Geddes Peter Douglas Christopher P. Moore Trevor J. Wear Peter L. Egerton 《Journal of fluorescence》1999,9(3):163-171
Fourteen thin-film optical sensors in which halide-sensitive fluorophores are immobilized in a thin copolymer film (50 m, dry) have been developed and characterized. The sensor films use rhodamine, 6-methoxyquinoline, and harmane dyes which have been functionalized and bound to a hydrophilic copolymer. The sensor films are reversibly capable of determining aqueous bromide and iodide with 4 and 2% accuracy, respectively, at concentrations of around 10–3 mol dm–3, and are more sensitive than previous plastic sensor fabrications. The 90% response time to molar iodide is 30–60 s. A combination of sensor films allows the simultaneous determination of both I– and Br– in a mixed-halide solution. The interference of several ions, including pseudo-halides, on the sensor films has been studied. 相似文献
147.
The effect of a dispersed phase in reducing the concentration polarization in a membrane tube has been studied. The presence of a dispersed phase seems to have an effect in controlling the size of eddy formation and the rate of energy dissipation in the fluid medium. The role of eddy length and the energy dissipation rate on the mass transfer coefficient is discussed. Theoretical results obtained for the mass transfer coefficient and for the concentration polarization in the case of gelatin ultrafiltration are compared with the existing experimental results. The theoretical predictions seem to be in good agreement with the experimentally observed results. 相似文献
148.
以NH4Cl作助溶剂,碳还原硫酸钙的方法合成了CaS:Ce。在紫外光激发下,CaS:Ce中存在着Ce^3+的^2D-^2F5/2(500nm)和^2D-^2F7/2(550nm)跃迁发射,但在蓝色光激发下,只有波峰为532nm半宽度为92nm的宽带发射。当Ce^3+的浓度为0.075mol%时,^2D-^2F5/2跃迁发射强度与^2D-^2F7/2跃迁发射强度相等,而532nm发射猝灭。 相似文献
149.
以二乙氨基乙基交联葡聚糖凝胶为基质的铝荧光传感层 总被引:1,自引:0,他引:1
本文基于Al^3+离子对电价键固定在二乙氨基乙基交联葡聚糖凝胶上的水杨基荧光 酮的可逆荧光淬灭作用,研制了测定Al^3+离子浓度的荧光传感层。 相似文献
150.