Applications of the Static Quenching of Rhodamine B by Carbon Nanotubes

We report here on the interaction of the fluorescent dye rhodamine B (RB) with single‐walled carbon nanotubes (SWCNTs). We observe that SWCNTs statically quench the fluorescence of RB by forming a stable ground state complex. Careful spectroscopic analysis indicates that the complex formation is efficient mainly with certain chiral forms. We propose three different applications utilizing this quenching mechanism and the associated complexation. Firstly, the quenching efficiency can be utilized as a measure for the characterization and quantification of nanotube dispersions. Secondly, we demonstrate that the specific complexation of RB can be deployed to enrich certain chiral forms in suspension. Finally, we show that RB can be effectively used to visualize nanotubes deposited on substrates.     

A thermodynamic investigation on the binding of phenothiazinium dyes azure A and azure B to double stranded RNA polynucleotides

The thermodynamics of the reactions of the two phenothiazinium dyes azure A and azure B with the three double stranded ribonucleic acids, poly(A).poly(U), poly(C).poly(G), poly(I).poly(C) were investigated using DSC and ITC. The bound dyes stabilized the RNAs against thermal strand separation. The binding of azure A to the RNAs was predominantly enthalpy dominated while the binding of azure B was favoured by both negative enthalpy and favourable entropy changes. Although electrostatic interaction had a significant role in the binding, non-polyelectrolytic forces dominated the binding process. The negative values of heat capacity changes for the binding suggested a substantial hydrophobic contribution to the binding process. The overall binding affinity of both the dyes to the RNAs varied in the order, poly(A).poly(U) > poly(C).poly(G) > poly(I).poly(C).     

2(3)-四-(2-异丙基-5-甲基苯氧基)钛氧酞菁的合成及其近红外发光特性

通过分步合成的方法,在钛氧酞菁的外围引入了四个苯氧基团,合成了一种2(3)-四-(2-异丙基-5-甲基苯氧基)钛氧酞菁.通过质谱、核磁、元素分析、紫外可见吸收光谱、近红外光荧光谱和循环伏安法对其结构和性质进行了表征,并利用旋涂加真空热蒸发的方法制得了该材料的电致发光器件(ITO/PVK:TiOPc/BCP/LiF/Al).结果表明,四取代的钛氧酞菁固态的近红外光荧光峰值在1080nm左右;其近红外电致发光的峰值波长落在1050nm左右.在PVK掺杂的器件中,钛氧酞菁的质量分数为30%时有较强的发光强度.     

Diffusion of nonionic azo dyes in nylon-6

Diffusion of 2,4-dinitroaniline and three nonionic azo dyes in Nylon-6 film was studied by analysis of the concentration-distance curves (profiles) of penetrants in the polymer. Actual diffusivities D_(c) of penetrants in polymer, diffusion coefficients as a function of the concentration C_f of penetrant in polymer, were calculated from the profile. It was found that D_(c) is almost constant or decreases gradually with decreasing C_f in the range of high-medium C_f but decreases appreciably with decreasing C_f at low C_f. The change in D_(c) with C_f was explained in terms of the dual-mode sorption-diffusion model. The penetrants diffuse in the polymer as two distinct species, i.e., a dissolved species and an adsorbed species. The former is the penetrant taken up by the polymer by a partition mechanism (dissolved species) and the latter is that taken up by Langmuir sorption (adsorbed species). The actual diffusivity D_P(c) of the dissolved species decreases with decreasing C_f. While the actual diffusivity D_L(c) of the adsorbed species normally increases gradually with decreasing C_f. D_P(c) is usually larger than D_L(c). © 1993 John Wiley & Sons, Inc.     

Near-IR Luminescent Rare Earth Ion–Sensitizer Complexes

Rare earth ions, with relatively long luminescence lifetimes, have significant advantages for application in fields as varied as diagnostics and optical amplification. In diagnostics the long luminescence lifetimes allow for extremely sensitive time-gated detection, where the difference in temporal behavior of scatter and background fluorescence and the long-lived rare earth luminescence is utilized. In optical amplification the long excited-state lifetime makes it easier to obtain population inversion, a requirement for effective stimulated emission. Unfortunately the absorption cross section of rare earth ion transitions is extremely low. However, via sensitized excitation by means of a suitable organic molecule, efficient excitation is obtained. It is shown that excitation in the visible part of the spectrum can be used to excite rare earth ions which luminesce in the near-IR, such as ytterbium, neodymium, and erbium, via a fluorescein-derivative as sensitizer. The advantages of this approach are manifold. Low-cost light sources are available for the visible part of the spectrum, and interferences from the matrix (scatter, absorption) are minimal. Detection in the near-IR is almost interference-free. For optical amplification the wavelength regions around 1300 and 1550 nm, which can be covered with the neodymium and erbium complexes, respectively, are the most important for applications in optical telecommunication.     

Spectral-Luminescent Properties of Cationic Indotricarbocyanine Dyes in Cancerous Cells and Solutions

The spectral-luminescent properties of symmetrical indotricarbocyanine dyes with the same cation and different anions (Br^–, BF₄ ^–) in cancerous HeLa cells, an isotonic solution of NaCl, and organic solvents have been investigated. It is shown that when these dyes are present in cells in nontoxic concentrations, they are in a monomeric state, they are localized in the region with a low dielectric permeability, bonded to biological macromolecules, and do not make contact with an aqueous medium. It has been established for the first time that the molecules of the polymeric dyes are present in cells predominantly in the form of contact ion pairs, and in a dye with the Br^– anion the presence of free cations or solvately separated ionic pairs is revealed. It is shown that the shift of the ion equilibrium toward contact ion pairs for the dyes in the cells (as compared to the low-polarity organic solvents) can be due to the fairly high concentration of salts in the biosystem.     

介电微球对oxazine溶液荧光的调制

研究了染料恶嗪（oxazine 1)溶液中掺有高折射率玻璃微球时，微球表面附近染料荧光的荧光光谱特性，发现微球外表面附近染料分子的荧光光谱也会象球内情况一样形成结构共振，用Mie散射理论和微腔理论对此实验现象进行了分析，实验与理论计算结果符合得较好。     

Influence of the Aggregation of Homo-N-Mer Cyanine Dyes on the Nucleic Acids Detection Sensitivity

Novel benzothiazolopyridinium homo-n-mer cyanine dyes are proposed for nucleic acid fluorescent detection. Dependence of the sensitivity of detection in solution from the dye molecules/DNA base pairs ratio was studied. It was shown that the presence of the dye excess could significantly decrease the detection limit. We believe this could be explained by the formation of the dye aggregates on DNA surface.     

Crown ether styryl dyes

The stoichiometry of complexation of crown ether styryl dyes with Mg²⁺, Ca²⁺, and Ba²⁺ ions and the dependence of the stability constants of these complexes on the length of theN-sulfoalkyl substituent were investigated. Introduction of a terminal sulfo group into theN-ethyl substituent had but a small effect on the stability constant for the complexes with 1 : I stoichiometry. Increase in the length of theN-substituent by one or two methylene groups resulted in a jumpwise rise of this constant. The effect observed was attributed to the formation of the intramolecular ion pair. The dimerization constant for Mg²⁺ complexes increased dramatically when passing from the sulfopropylN-substituent to the sulfobutyl one. The increase in the constant results from the decrease in steric strains in the dimeric complex.For Part 16, see Ref. ITranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 605–613, March, 1996.