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1.
A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2-fluorenesulfonate (2,7-DAFS), was prepared by a three-step
reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence
spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular
charge-transfer (ICT) to π → π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless
single band with a large Stokes shift, whereas that of the acidic form, *(+HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus
pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *(+HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence
occurs. The pKa* was estimated as −1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the
polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence
quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15 ∼ 25 times
greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher
sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant
advantages for a variety of applications. 相似文献
2.
N. A. Nemkovich H. Detert V. Schmitt Yu. V. Kruchenok 《Journal of Applied Spectroscopy》2012,79(3):353-359
Absorption and fluorescence spectra of octupolar centrosymmetric oligophenylenevinylene dyes (E,E)-bis[2-(4-hexyloxyphenyl)ethenyl]-(E,E)-3,6-bis-[2-(4-N,N-dipropylaminophenyl)ethenyl]pyrazine and (E,E,E,E)-2,3,5,6- tetra-[2-(4-hexyloxyphenyl)ethenyl]pyrazine were measured in various solvents. An electro-optical absorption method was used to determine their dipole moments as μ g = 6.1∙10–30 and 3.4∙10–30 C∙m in the equilibrium ground state and the increased values ∆ a μ = 11.9∙10–30 and 8.2∙10–30 C∙m upon excitation into a Franck–Condon state. Quantum-chemical calculations showed that the molecules had non-planar configurations. The π,π-conjugated system was localized on the most planar part of the molecule that was responsible for light absorption in the range 300–450 nm due to a change in the geometry of the molecules in the ground state. Localized excitation of the molecules caused their dipole moments ∆ a μ to change significantly. 相似文献
3.
Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker
separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties.
The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices
such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed
in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform
and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and
methanol. The fluorescence lifetimes are in the range of 1–4 ns for all measured fluorophores. The large Stokes shift (4,000
to 8,000 cm−1) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The
observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by
the diffusion-controlled bimolecular rate (cca 2 × 1010 L mol−1 s−1). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism. 相似文献
4.
Wen-Xian Li Wen-Juan Chai Xiao-Jun Sun Tie Ren Xiao-Yan Shi 《Journal of fluorescence》2010,20(4):873-880
Two novel ternary rare earth complexes of Tb(III) and Dy(III) perchlorates with bis(benzoylmethyl) sulfoxide (L) and benzoic
acid (L′) had been synthesized and characterized by elemental analysis, coordination titration analysis, molar conductivity,
IR, TG-DSC, 1HNMR and UV spectra. The results indicated that the composition of these complexes was REL5L′(ClO4)2·nH2O (RE= Tb(III), Dy(III); L=C6H5COCH2SOCH2COC6H5, L′=C6H5COO; n = 6,8). The fluorescence spectra illustrated that the ternary rare earth complexes presented stronger fluorescence intensities,
longer lifetimes and higher fluorescence quantum efficiencies than the binary rare earth complexes REL5·(ClO4)3·2H2O. After the introduction of the second ligand benzoic acid group, the relative fluorescence emission intensities and fluorescence
lifetimes of the ternary complexes REL5L′(ClO4)2·nH2O (RE= Tb(III), Dy(III)) enhanced more obviously than the binary complexes. This indicated that the presence of both organic
ligands bis(benzoylmethyl) sulfoxide and the second ligand benzoic acid could sensitize fluorescence intensities of rare earth
ions, and the introduction of benzoic acid group was resulted in the enhancement of the fluorescence properties of the ternary
rare earth complexes. The phosphorescence spectra were also discussed. 相似文献
5.
A novel ligand with double sulfinyl groups, bis(benzylsulfinyl)methane, was synthesized by a new method and its two lanthanide
(III) complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis,
IR, TG-DSC, 1HNMR and UV spectra. The results indicated that the composition of these complexes was REL2.5(ClO4)3·3H2O (RE = Tb (III), Dy (III), L = C6H5CH2SOCH2SOCH2C6H5). The FT-IR results revealed that the perchlorate group was bonded with the lanthanide ion by the oxygen atoms, and the coordination
was bidentate. The fluorescent spectra illustrated that both the Tb (III) and Dy (III) complexes displayed characteristic
fluorescence in solid state, especially for the Tb (III) complex, the peak of 5D4 → 7 F5 of the Tb (III) ion in 544 nm was stronger than that of others. It indicated that the Tb (III) complex could emit purer green
fluorescence. By analysis fluorescence and phosphorescence spectra, it was found that the ligand had the advantage to absorb
energy and transfer it to the Tb (III) and Dy (III) ions. The phosphorescence spectra and fluorescence lifetimes of the complexes
were also measured. 相似文献
6.
Suthari Prashanthi P. Hemant Kumar Li Wang Arun Kumar Perepogu Prakriti Ranjan Bangal 《Journal of fluorescence》2010,20(2):571-580
Steady state and time resolved fluorescence quenching behaviors of meso-Tetrakis (pentafluorophenyl) porphyrin (H2F20TPP) in presence of different aliphatic and aromatic amines have been executed in homogeneous dichloromethane (DCM) solution.
At room temperature in DCM, free base (H2F20TPP) shows fluorescence with two distinct peaks at 640 and 711 nm and natural lifetime τ
f = 9.8 ns which are very similar to that of meso-tetraphenyl porphyrin (TPP). Unlike TPP, addition of both aliphatic and aromatic
amines to a solution containing H2F20TPP results in an efficient decrease in fluorescence intensity without altering the shape and peak position of fluorescence
emission. Upon addition of amines there was no change in optical absorption spectra of H2F20TPP. The fluorescence quenching rate constants ranged from 1 × 109 to 4 × 109 s−1, which are one order below to the diffusion control limit, and temperature dependent quenching rate constants yield the activation
energies which are found to be order of 0.1 eV. Femto second transient absorption studies reveal the existence of amine cation
radical and porphyrin anion radicals with very short decay time (15 ps). The fluorescence quenching reaction follows Stern–Volmer
kinetics. Steady state and time-resolved data are interpreted within general kinetic scheme of Marcus semi-classical model
which attributes bimolecular electron transfer process between amines and the lowest excited singlet state of H2F20TPP. Calculated internal reorganization energies are found to be in between 0.04 and 0.22 ev. Variation of electron transfer
rate as function of free energy change (∆G0) points the ET reactions in the present systems are in Marcus normal region. This is the first example of reductive fluorescence
quenching of free base neutral porphyrins in homogeneous organic solvent ever known. 相似文献
7.
Bañuelos J López Arbeloa F Arbeloa T Salleres S Vilas JL Amat-Guerri F Liras M López Arbeloa I 《Journal of fluorescence》2008,18(5):899-907
The structural, electronic and photophysical properties of three new asymmetric, highly fluorescent difluoroborondipyrromethene
(BODIPY) dyes, bearing an amino or an acetamido group at position 3 of the chromophoric core, have been studied in different
apolar, polar and polar/protic solvents. The presence of the 3-amido group extents the delocalization of the π-system, leading to bathochromic shifts in the absorption and fluorescence bands, as predicted by quantum mechanic calculations.
The 3-amino dye shows photophysical properties highly dependent on the solvent polarity and acidity, and is characterized
by a hypsochromic shift of its absorption band, with regard to the corresponding acetylated dye, as well as a low fluorescence
quantum yield in acid media with proton concentration lower than 4 × 10−4 M. In media with higher proton concentration, the BF2 bridge group of the 3-amino dye is removed, yielding the corresponding non-fluorescent dipyrromethene precursor. These results
suggest that the 3-amino dye could be used as a fluorescence probe for the study of the acidity of different environments. 相似文献
8.
The electronic absorption, and emission spectra as well as fluorescence quantum yield of 3-(benzothiazol-2-yl)-7-hydroxycoumarin (BTHC) were measured in different solvents and are affected by solvent polarity (Δf). The deprotonation of BTHC by triethylamine is a reversible process. BTHC is relatively photostable, the quantum yield of photodecomposition (φc) was found to be 2×10−4 and 2.7×10−4 in EtOH and DMF, respectively. The fluorescence lifetimes of BTHC were measured in the absence and in the presence of molecular oxygen and were found to be 2.82 and 2.78 ns, respectively. BTHC acts as good laser dye upon pumping with nitrogen laser (λex=337.1 nm) in ethanol and gives laser emission with maxima at 508 and 522 nm. 相似文献
9.
Sasirekha V Vanelle P Terme T Meenakshi C Umadevi M Ramakrishnan V 《Journal of fluorescence》2007,17(5):528-539
Optical absorption and fluorescence emission spectra of 2,3-bis(chloromethyl)-1,4-anthraquinone (DCMAQ) in single solvents
namely, carbon tetrachloride, acetonitrile, chloroform, propan-2-ol and its binary mixtures [carbon tetrachloride/chloroform,
chloroform/acetonitrile, chloroform/propan-2-ol] have been investigated. The preferential solvation of DCMAQ in above mixtures
has been studied by monitoring the absorption and fluorescence spectra of DCMAQ. The spectral features indicate that DCMAQ
is preferentially solvated by CHCl3 in the above mixtures. This can be elucidated from the local mole fraction, non-linearity in transition energy plot, preferential
solvation index (δ
s2) and (f
2/f
1) values. Molecular recognition properties of p-tert-butylcalix[4]arene (tBC) to DCMAQ via hydrogen bonding and π–π interaction were sensed successfully on the basis of
absorption and fluorescence emission spectroscopies, by which the stoichiometry ratio and the binding constant of the tBC–DCMAQ
complex were determined. 相似文献
10.
N. A. Borisevich A. P. Lugovskii V. A. Povedailo E. E. Tselesh D. L. Yakovlev 《Journal of Applied Spectroscopy》2010,77(3):343-348
Conformations of He-jet-cooled trimethyl[(3-indole)ethoxy]silane (TIES) have been studied using a laser spectroscopy technique
in combination with quantum-chemical computations. Six probable conformers of the molecule were computed, of which only two
conformations were observed. Based on an analysis of fluorescence excitation spectra, fluorescence spectra, shapes of rotational
band contours at the electronic S0–S1 transition of TIES, and theoretical computations, the above conformers were assigned to steric structures. Twisted structures
have the lowest energy due to intramolecular hydrogen bonds C - H ?O < CSi C - H \cdots O <_C^{Si} between hydrogen atoms of methyl groups and an oxygen atom and C–H···π between H and the π-electron cloud of the indole ring. 相似文献
11.
The synthesis and functionalization of carbon nanoparticles with PEG200 and mercaptosuccinic acid, rendering fluorescent carbon dots, is described. Fluorescent carbon dots (maximum excitation and
emission at 320 and 430 nm, respectively) with average dimension 267 nm were obtained. The lifetime decay of the functionalized
carbon dots is complex and a three component decay time model originated a good fit with the following lifetimes: τ
1 = 2.71 ns; τ
2 = 7.36 ns; τ
3 = 0.38 ns. The fluorescence intensity of the carbon dots is affected by the solvent, pH (apparent pK
a of 7.4 ± 0.2) and iodide (Stern-Volmer constant of 78 ± 2 M−1). 相似文献
12.
In this paper, we reported the syntheses and investigation of the modes of binding to DNA of the two new ethidium derivatives
containing benzoyl and phenylacetyl groups of both amines at 3-and 8- positions. The interactions between calf thymus DNA
(ct-DNA) and the two derivatives, 3,8-dibenzoylamino-5-ethyl-6-phenylphenantridinium cloride (E2) and 3,8-diphenylacetylamino-5-ethyl-6-phenylphenantridinium chloride (E3), were investigated by fluorescence quenching spectra and UV-vis absorption spectra. The Stern-Volmer quenching constants,
binding constants, binding sites and the corresponding thermodynamic parameters ΔH, ΔS and ΔG were calculated at different
temperatures. The results indicated the formation of E2 and E3-DNA complexes and van der Waals interactions as the predominant intermolecular forces in stabilizing for each complex. In
addition, increasing nucleophilicity of the functional groups at 3- and 8- positions exhibited the respectable increment the
DNA binding affinities of derivatives. The results of absorption, ionic strength and iodide ion quenching suggested that the
interaction mode of E2 and E3 with ct-DNA was intercalative binding. The limit of detection (LOD) of ct-DNA were 7.49 × 10−8 (n = 4) and 4.18 × 10−8 mol/l (n = 7) in presence of E2 and E3, respectively. 相似文献
13.
A. Li L. Sun Z. Zheng Q. Lü W. Wu W. Liu Y. Yang T. Lü 《Applied physics. B, Lasers and optics》2008,90(1):29-34
The results of the spectroscopic analysis of transition strengths for Er3+ ions in a series of Hf:Er:LiNbO3 crystals with variable Hf content and fixed Er content are reported. Unpolarized UV-VIS-NIR absorption spectra, upconversion
fluorescence spectra excited at 800 nm, and microsecond time-resolved spectra excited at 400 nm and 800 nm by 800 nm femtosecond
laser were measured at room temperature. The HfO2 incorporation has influence on Er3+ radiative lifetimes, and fluorescence branching ratios. For Hf(4 mol %):Er(1 mol %):LiNbO3, Ω2=2.63×10-20 cm2, Ω4=2.86×10-20 cm2, and Ω6=0.72×10-20 cm2. Ω2<Ω4 is contrary to the Er3+ general trend of Ω2>Ω4>Ω6 when the Hf content is below its threshold concentration. In addition, the sum of Ω increases with the Hf content when the
HfO2 content below 6 mol % is unfamiliar. The upconversion mechanism is discussed in this work.
PACS 71.20.Eh; 77.84.Dy; 42.62.Fi; 42.65.Ky 相似文献
14.
A ligand with two carbonyl groups and one sulfinyl group has been synthesized by a new method and its several lanthanide (III)
complexes were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR,
TG-DSC, 1H NMR and UV spectra. The results indicated that the composition of these complexes is REL5(ClO4)3·3H2O (RE = La(III), Pr(III), Eu(III), Tb(III), Yb(III), L = C6H5COCH2SOCH2COC6H5). The fluorescent spectra illustrate that both the Tb (III) and Eu (III) complexes display characteristic metal-centered
fluorescence in solid state, indicating the ligand favors energy transfer to the excitation state energy level of them. However,
the Tb (III) complex displays more effective luminescence than the Eu (III) complex, which is attributed to especial effectively
in transferring energy from the average triplet energy level of the ligands (T) onto the excited state (5D4) of Tb (III) than that (5D0) of Eu (III), showing a good antenna effect for Tb(III) luminescence. The phosphorescence spectra and the relationship between
fluorescence lifetimes and fluorescence intensities were also discussed. 相似文献
15.
The structure and optical properties of triphenylamine-rhodanine dye 2-(5-(4-(diphenylamine)benzylidene)-4-oxo-2-thioxothiazolidine-3-yl)
acetic acid, which is used as a sensitizer for nanocrystalline TiO2 solar cells, are studied based on the density functional theory. The nature of the absorption of this dye in the visible
and near UV regions is discussed within the time-dependent density functional theory (TDDFT). The calculations of the vertical
excitation energies of the dye molecule taking into account the effect of solvent reveal a strong positive solvatochromic
effect compared to the calculations in the vacuum approximation. The IR absorption bands of this dye in the region of 600–1850
cm−1 are completely interpreted. 相似文献
16.
A fluorescent assay of Hg2+ in neutral aqueous solution was developed using N-[p-(dimethylamino)benzamido]-N′-phenylthiourea (1). 1’s fluorogenic chemodosimetric behaviors towards various metal ions were studied and a high sensitivity
as well as selectivity was achieved for Hg2+. It was because of a strongly fluorescent 1,3,4-oxadiazoles which was produced by the Hg2+ promoted desulfurization reaction. The spectra of ESI mass and IR provided evidences for this reaction. According to fluorescence
titration, a good linear relationship ranging from 1.0 × 10−7 to 2.0 × 10−5 mol l−1 was obtained with the limit of detection as 3.1 × 10−8 mol l−1.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
Two new ligands derived from phloroglucinol 2-{[(4-methoxy benzoyl ) oxy ] } methyl benzoic acid[L1] and 2-{[(4-methyl benzoyl
)oxy] methyl} benzoic acid[L2] were synthesized. The solid complex Eu(III)-L2 has been synthesised and characterized by elemental
analysis ,UV and IR spectra. The reaction of Eu(III) with the two synthesized ligands has been investigated in I = 0.1 mol dm-3 p-toluene sulfonate by cyclic voltammetry and square wave voltammetry. The reaction of Eu (III)–L1 and Eu (III)–L2 binary
complexes with nucleotide 5′-AMP , 5′-ADP ,5′-ATP , 5′- GMP , 5′-IMP , and 5′-CMP has been investigated using UV, fluorescence
and electrochemical methods. The experimental conditions were selected such that self-association of the nucleotides and their
complexes was negligibly small, that is, the monomeric complexes were studied. The interaction of the Eu(III)–L1 or L 2 solid
complexes with calf-thymus DNA has been investigated by fluorescence and electrochemical methods including cyclic voltammetery(CV)
,differential pulse polarography (DPP) and square wave voltammetry (SWV) on a glassy carbon electrode. The fluorescence intensity
of Eu(III)-L2 complex was enhanced with the addition of DNA. Under optimal conditions in phosphate buffer pH 7.0 at 25 °C
the linear range is 3–20 μM for calf thymus DNA (CT–DNA) and the corresponding determination limit is 1.8 μM. 相似文献
18.
It was first found that 4-(2-pyridylazo)-resorcinol (PAR) can combine with lysozyme forming a polymolecular complex, with
the molar ratio of 1:12 (lysozyme/PAR) in the medium of acetate buffer (pH 6.0). The fluorescence spectra suggested that PAR
molecules may produce self-aggregation, and it was suggested that there are interactions between lysozyme and PAR possibly
mainly on the cooperation of hydrophobic, electrostatic actions and chelate bond. The coordination complex of lysozyme-PAR
can cause an enhanced resonance light scattering (RLS) signal with the scattering peak located at 521 nm. The increment of
RLS intensity was linear with the concentration of lysozyme over the range from 1 ng mL-1 to 30.0 μg mL-1, with the limit of detection of 0.3 ng mL−1 (3σ, n = 5). Effect of experimental conditions, including temperature, pH, concentration of PAR, and the ionic strength on RLS were
also tested. The proposed RLS method was successfully applied to analyze lysozyme in hen egg white, human saliva and tear
samples without any special pretreatment. Compared with other methods, the proposed procedure is of high sensitivity and selectivity. 相似文献
19.
Xiao-Jun Sun Wen-Xian Li Wen-Juan Chai Tie Ren Xiao-Yan Shi 《Journal of fluorescence》2010,20(2):453-461
Two novel ternary rare-earth complexes SmL5·L’·(ClO4)2·7H2O and EuL5·L’·(ClO4)2·6H2O (the first ligand L = C6H5COCH2SOCH2COC6H5, the second ligand L’ = C6H4OHCOO−) were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DSC,
1HNMR and UV spectra. The detailed luminescence studies on the rare-earth complexes showed that the ternary rare-earth complexes
presented stronger fluorescence intensities, longer lifetimes, and higher fluorescence quantum efficiencies than the binary
rare-earth materials. After the introduction of the second ligand salicylic acid group, the relative emission intensities
and fluorescence lifetimes of the ternary complexes LnL5·L’·(ClO4)2·nH2O (Ln = Sm, Eu; n = 7, 6) enhanced more obviously than the binary complexes LnL5·(ClO4)3·2H2O. This indicated that the presence of both organic ligand bis(benzoylmethyl) sulfoxide and the second ligand salicylic acid
could sensitize fluorescence intensities of rare-earth ions, and the introduction of salicylic acid group was a benefit for
the fluorescence properties of the ternary rare-earth complexes. The fluorescence spectra, fluorescence lifetime and phosphorescence
spectra were also discussed. 相似文献
20.
Wen-Xian Li Yu-Shan Zheng Xiao-Jun Sun Xiao-Yan Shi Wen-Juan Chai Tie Ren 《Journal of fluorescence》2010,20(1):235-241
A ligand with double sulfinyl groups, naphthyl-naphthalinesulphonylpropyl sulfoxide(dinaphthyl disulfoxide, L), was synthesized
by a new method and its several lanthanide (III) complexes were synthesized and characterized by element analysis, molar conductivity,
coordination titration analysis, IR, TG-DTA, 1HNMR and UV spectra. The composition of these complexes, were RE2(ClO4)6·(L)5·nH2O (RE = La, Nd, Eu, Tb, Yb, n = 2 ∼ 6, L = C10H7SOC3H6SOC10H7). The fluorescent spectra illustrated that the Eu (III) complex had an excellent luminescence. It was supposed that the ligand
was benefited for transferring the energy from ligand to the excitation state energy level (5D0) of Eu (III). The Tb (III) complex displayed weak luminescence, which attributed to low energy transferring efficiency between
the average triplet state energy level of ligand and the excited state (5D4) of Tb (III). So the Eu (III) complex displayed a good antenna effect for luminescence. The phosphorescence spectra and the
relationship between fluorescence lifetime and fluorescence intensity were also discussed. 相似文献