Tuning the Efficiency of Dendritic Nanocarriers using Conformational Constraints

A series of deoxycholic and cholic acid‐derived oligomers were synthesized and their ability to extract hydrophilic dye molecules of different structure, size, and functional groups into nonpolar media was studied. The structure of the dye and “dendritic effect” in the extraction process was examined using absorption spectroscopy and dynamic light scattering (DLS). The efficiency of structurally preorganized oligomers in the aggregation process was evaluated by 1‐anilinonaphthalene‐8‐sulfonic acid (ANS) fluorescence studies. The possible formation of globular structures for higher‐generation molecules was investigated by molecular modeling studies and the results were correlated with the anomaly observed in the extraction process with this molecule. The ability of these molecules for selective extraction of specific dyes from blended colors is also reported.     

Fabrication of color-tunable luminescent silica nanotubes loaded with functional dyes using a sol-gel cocondensation method

Luminescent silica nanotubes SNT-2 (loaded with coumarion laser dye 2) and SNT-3 (loaded with anthracene laser dye 3) were prepared by sol-gel cocondensation of functional dyes and TEOS in a cholesterol-based organogel system. The emission colors of silica nanotubes were tuned by using different functional dyes. Interestingly, there is a great difference in PL spectrum of silica nanotubes loaded with functional dyes between ethanol and the solid state. In ethanol, a green light emission of SNT-2 and a bluish green light emission of SNT-3 were observed at 486 and 465 nm, respectively, because of the anchoring state between the dye and the tube, whereas in the solid state, strong blue light emissions of SNT-2 and SNT-3 were observed at 482 and 483 nm, respectively, because of the intense emission of the silica nanotube (SNT) itself rather than that of 2 and 3.     

Synthesis of 5,7-dihydroxy-4,8-dimethylchromen-2-one and its azo derivatives

5,7-Dihydroxy-4,8-dimethylchromen-2-one was synthesized based on methyl phloroglucinol and its spectral and physicochemical characteristics were obtained. Reactions of the newly synthesized coumarin with different diazonium salts were studied, conditions allowing selective obtaining the corresponding monoor bisazo compounds were found. The synthesized azo compounds dye nylon in the yellow-brown colors under standard coloration conditions, providing high stability of obtained colors upon exposure to physicochemical conditions.     

Photo‐ and pH‐Tunable Multicolor Fluorescent Nanoparticle‐Based Spiropyran‐ and BODIPY‐Conjugated Polymer with Graphene Oxide

We report a stimuli‐responsive fluorescent nanomaterial, based on graphene oxide coupled with a polymer conjugated with photochromic spiropyran (SP) dye and hydrophobic boron dipyrromethane (BODIPY) dye, for application in triggered target multicolor bioimaging. Graphene oxide (GO) was reduced by catechol‐conjugated polymers under mildly alkaline conditions, which enabled to formation of functionalized multicolor graphene nanoparticles that can be induced by irradiation with UV light and by changing the pH from acidic to neutral. Investigation of these nanoparticles by using AFM, fluorescence emission, and in vitro cell and in vivo imaging revealed that they show different tunable colors in bioimaging applications and, more specifically, in cancer‐cell detection. The stability, biocompatibility, and quenching efficacy of this nanocomposite open a different perspective for cell imaging in different independent colors, sequentially and simultaneously.     

DNA-catalyzed transfer of a reporter group

Herein we describe a novel DNA-catalyzed transfer of a reporter group from a donating to an accepting oligo-peptide nucleic acid (PNA), generating high catalytic turnover numbers in a DNA-sequence specific manner. The demonstrated transfer of the Dabcyl group was designed to switch on emission of a fluorescein dye while switching off emission of a rhodamine dye. This setup allows the highly sensitive and selective detection of DNA-sequences in real time.     

Use of Aggregation‐Induced Emission for Selective Detection of Phase Transformation during Evaporative Crystallization of Hexaphenylsilole

Crystallization of organic molecules is quite complicated because the crystallization process is governed by weak intermolecular interactions. By exploiting aggregation‐induced emission (AIE), we attempted to realize the selective detection of phase transformation during the evaporative crystallization of hexaphenylsilole (HPS), which shows different fluorescent colors in the amorphous and crystalline phases. No fluorescence emission was observed in the HPS solution immediately after dropping on the glass substrate due to the non‐radiative deactivation induced by intramolecular rotational or vibrational motion, suggesting that HPS exists as a monomer in solution. As time elapsed after dropping, green emission first appeared, which changed to blue after solvent evaporation, because of phase transformation from the amorphous state to the crystalline state. This phenomenon supports not only the two‐step nucleation model involving an intermediate such as a liquid‐like cluster prior to nucleation but also the real‐time detection of Ostwald's rule of stages during evaporative crystallization.     

The synthesis and spectral properties of a stimuli-responsive D–π–A charge transfer dye based on indole donor and 2-cyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran acceptor moieties

A particular chromogenic and fluorophoric dye chemosensor was designed and synthesized, which was based on the stimuli-responsive D–π–A charge transfer system. Indole moiety as a donor unit and furan moiety as an acceptor unit were used. This prepared dye sensor showed the selective fluoride ion sensing effects in UV–vis absorption and fluorescence emission properties. Clear absorption changes and highly selective fluorescence quenching effects with fluoride ion were determined. Experimental data and images were collected and supported to provide a better understanding of this particular dye sensor.     

Density-Dependent Emission Colors from a Conformation-Switching Chromophore in Polyurethanes

Achieving full-color emission from a single chromophore is not only highly desirable from practical considerations, but also greatly challenging for fundamental research. Herein, we demonstrated the density-dependent emission colors from a single boron-containing chromophore, from which multi-color fluorescent polyurethanes were prepared as well. Originating from its switchable molecular conformations, the emission color of the chromophore was found to be governed by the packing density and strongly influenced by hydrogen bonding interactions. The chromophore was incorporated into polyurethanes to achieve full-color emitting materials; the emission color was only dependent on the chromophore density and could be tuned via synthetic approach by controlling the compositions. The emission colors could also be modulated by physical approaches, including by swelling/deswelling process, compression under high pressure, and even blending the fluorescent polyurethane with non-emitting ones.     

Optical mercury sensing using a benzothiazolium hemicyanine dye

[structure: see text] The selectivity and sensitivity of a benzothiazolium hemicyanine dye toward mercury(II) in aqueous solutions are described. Mercury ions coordinate to the dye forming a 1:1 complex. This interaction induces a color change in the dye at micromolar concentrations of mercury. Furthermore, the color change and quenching of the dye emission are selective for mercury when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II).     

Three-point recognition and selective fluorescence sensing of L-DOPA

[reaction: see text] A phenylboronic acid derivative of a well-known dye (Lucifer yellow) recognizes L-DOPA through a combination of reversible esterification, charge transfer, and electrostatic interactions. The selective recognition event is signaled by a drop in the emission intensity of the fluorescent chemosensor.     

Narrowing of spontaneous emission and lasing in lyotropic and thermotropic liquid crystals

The narrowing of spontaneous emission and lasing are reported for the first time for a dye-doped lyotropic liquid crystal consisting of a methylbenzylamine solution of polybenzylglutamate (PBLG). Lasing was also studied in twisted nematics based on cholesterol derivatives. PBLG produces a cholesteric liquid crystal (CLC) with selective reflection in the visible region at PBLG concentrations above 55%. A comparison is made of the narrowing of spontaneous emission and lasing in lyotropic vs. thermotropic liquid crystals. In both cases lasing occurs where the selective reflection band overlaps the dye emission band. Thermotropic liquid crystals show a much lower lasing threshold than lyotropic systems. The lasing mechanism and the role of disorder in both systems are discussed.     

Narrowing of spontaneous emission and lasing in lyotropic and thermotropic liquid crystals

The narrowing of spontaneous emission and lasing are reported for the first time for a dye-doped lyotropic liquid crystal consisting of a methylbenzylamine solution of polybenzylglutamate (PBLG). Lasing was also studied in twisted nematics based on cholesterol derivatives. PBLG produces a cholesteric liquid crystal (CLC) with selective reflection in the visible region at PBLG concentrations above 55%. A comparison is made of the narrowing of spontaneous emission and lasing in lyotropic vs. thermotropic liquid crystals. In both cases lasing occurs where the selective reflection band overlaps the dye emission band. Thermotropic liquid crystals show a much lower lasing threshold than lyotropic systems. The lasing mechanism and the role of disorder in both systems are discussed.     

Emission of Au nanoparticles with and without rhodamine 6G dye

We have observed Stokes and anti-Stokes emission of Au nanoparticles suspended in methanol and rhodamine 6G dye solution. Photoluminescence of Au nanoparticles is a three-step process involving single-photon or three-photon excitation of electron-hole pairs, relaxation of excited electrons and holes, and emission from electron-hole recombination, possibly enhanced by surface plasmons. In the presence of dye, the excitation of anti-Stokes emission of gold involves two-photon absorption in rhodamine 6G molecules followed by the energy transfer to Au nanoparticles with simultaneous absorption of one pumping photon by Au. This mechanism significantly enhances anti-Stokes emission of gold nanoparticles in the presence of dye.     

Tuning the optical properties of hyperbranched polymers through the modification of the end groups

Dye‐capped, hyperbranched, conjugated polymers were prepared by the modification of the peripheral bromo end groups of the hyperbranched polymer core with a palladium‐catalyzed Suzuki–Miyaura cross‐coupling reaction. The dye‐modified, hyperbranched polymers had high molecular weights and displayed good solubility in common organic solvents such as tetrahydrofuran, toluene, and chloroform. The structure of the dye‐modified, hyperbranched polymers was characterized by ¹H and ¹³C NMR and elemental analysis. The thermal properties of five kinds of hyperbranched polymers were investigated with thermogravimetric analysis and differential scanning calorimetry. The optical properties of the dye‐capped, hyperbranched polymers were investigated with ultraviolet‐absorption and fluorescence spectroscopy. The hyperbranched structure could effectively reduce the aggregation of the peripheral dyes. The emission colors of the hyperbranched polymers could be easily tuned by end‐group modification. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 111–124, 2007     

Multicolor fluorescence of a styrylquinoline dye tuned by metal cations

A styrylquinoline dye with a dipicolylamine (DPA) moiety (1) has been synthesized. The dye 1 in acetonitrile demonstrates multicolor fluorescence upon addition of different metal cations. Compound 1 shows a green fluorescence without cations. Coordination of 1 with Cd(2+) shows a blue emission, while with Hg(2+) and Pb(2+) exhibits yellow and orange emissions, respectively. The different fluorescence spectra are due to the change in intramolecular charge transfer (ICT) properties of 1 upon coordination with different cations. The DPA and quinoline moieties of 1 behave as the electron donor and acceptor units, respectively, and both units act as the coordination site for metal cations. Cd(2+) coordinates with the DPA unit. This reduces the donor ability of the unit and decreases the energy level of HOMO. This results in an increase in HOMO-LUMO gap and blue shifts the emission. Hg(2+) or Pb(2+) coordinate with both DPA and quinoline units. The coordination with the quinoline unit decreases the energy level of LUMO. This results in a decrease in HOMO-LUMO gap and red shifts the emission. Addition of two different metal cations successfully creates intermediate colors; in particular, the addition of Cd(2+) and Pb(2+) at once creates a bright white fluorescence.     

Ion sensing coupled to resonance energy transfer: a highly selective and sensitive ratiometric fluorescent chemosensor for Ag(I) by a modular approach

We report a novel dimeric boradiazaindacene dye which can be converted in one step to an efficient resonance energy transfer (RET) dyad. In addition, if this modification is done with appropriate ligands, RET can be coupled to ion sensing. The utility of this approach is demonstrated in a highly selective, emission ratiometric chemosensor for Ag(I).     

分散染料染色法制备的彩色聚(苯乙烯-丙烯酸)纳米球

在低于聚合物纳米球玻璃化转变温度(110.69 ℃)的条件下,用两种分散染料对聚(苯乙烯-丙烯酸)[P(St-co-AA)]纳米球染色,研究了染色温度(75~95 ℃)和染料用量(1%~5%)对纳米球上染料吸附量的影响。 结果表明,染色温度越高,分散染料用量越大,所得到聚合物纳米球的颜色越深越鲜艳。 分子结构中氨基和羟基数量多的分散蓝2BLN在纳米球上的吸附量低于相同染料用量时分散红FB的吸附量。 经过染色后纳米球的表面变得很粗糙,粒径增加23 nm。 用彩色纳米球对经过阳离子化处理的棉织物进行染色,利用很少量的彩色纳米球,就可以使织物获得较深且鲜艳的颜色。     

Effect of sunset yellow dye on morphological,optical, dielectric,thermal and mechanical properties of KDP crystal

Herein, we describe the growth and morphology of well-defined dyed crystals of KH₂PO₄ (potassium dihydrogen orthophosphate; KDP) containing organic azo (sunset yellow; SSY) dye in the {1 0 1} & {0 0 1} pyramidal growth sectors. An understanding on selective dye inclusion in various growth sector of host crystal is proposed, which will help in designing novel tailor-made dyed photonic crystals. The structural analysis and the identification of various functional groups present in as grown KDP crystals were carried out using powder XRD, FTIR and Raman studies. Solid state transmittance spectra for dyed KDP crystals displayed three absorption peaks at 230 nm, 311 nm and 477 nm, which were blue shifted for SSY dye in KDP crystal relative to neutral aqueous solution of SSY dye. These blue shifts in the absorption maxima confirm the successful incorporation of sunset yellow dye into the pyramidal growth sectors of dyed KDP crystals. The band around 409 nm in the photoluminescence emission spectrum indicates a violet emission. SSY dye doped KDP crystals showed enhanced dielectric properties and thermal stability as compared to pure KDP crystal. The mechanical strength of the KDP crystals estimated using Vickers microhardness test was found to decrease with the increase in SSY dye doping.     

Color-Change Photoswitching of an Alkynylpyrene Excimer Dye

We describe a photoswitchable DNA-based dimeric dye that visibly changes fluorescence from green to blue upon UV irradiation. A novel bis-alkyne-dependent [2+2+2] cycloaddition is proposed as a mechanism for the color change in air. The photoinduced structural switching results in spatial separation of stacked pyrene units, thereby causing selective loss of the excimer emission. We demonstrate and suggest several applications for this novel photoswitch.     

聚合物电致发光材料及其发光颜色调节的研究进展

聚合物电致发光材料已成为功能材料研究领域的一个热点.与无机材料和有机小分子材料相比,聚合物发光材料具有来源广泛、易加工成型、通过分子结构设计可调节发光颜色等优点,成为制备大面积、低成本、全色柔性显示器件的首选材料.本文介绍了聚合物发光材料的发光机理及调节发光颜色的常用方法,综述了聚对苯乙炔类、聚对苯类、聚芴类等多种共轭聚合物发光材料的合成及发光颜色调节的研究现状,并对聚合物发光材料的发展趋势以及聚合物电致发光器件的制备进行了评述和展望.