Luminescence properties of soluble 2,2′,7,7′‐Tetrakis(2‐(9‐hexyl‐9H‐carbazol‐3‐yl)‐vinyl)‐9,9′‐spirobifluorene‐labeled dendrimers: Photoluminescence and electroluminescence

New light emitting dendrimers were synthesized by reacting 3,5‐bis‐(3,5‐bis‐benzyloxy‐benzyloxy)‐benzoic acid or 3,5‐bis‐[3,5‐bis‐(3,5‐bis‐benzyloxy‐benzyloxy)‐benzyloxy]‐benzoic acid with a carbazolyl vinyl spirobifluorene moiety. A blue‐emitting core dye was encapsulated by multibenzyloxy dendrons, and two dendrimers having different densities of dendrons were prepared. Photoluminescence (PL) studies of the dendrimers demonstrated that at the higher density of benzyloxy dendrons, the featureless vibronic transitions were improved, causing lesser excimer emission. The similarity of the solution and solid emission spectra of the larger dendrimer, 10 , revealed the suppression of molecular aggregation in the solid film, which is attributed to the presence of the bulky benzyloxy dendrons. The electroluminescence spectra of multilayered devices made using 10 predominantly exhibited blue emissions; similar emission was observed in the PL spectra of its thin film. The multilayered devices made using 3 , 9 , and 10 showed luminances of 1021 cd m^?2 at 5 V, 916 cd m^?2 at 6 V, and 851 cd m^?2 at 6.5 V, respectively. The largest dendrimer, 10 , bearing a greater number of benzyloxy dendrons, exhibited a blue‐like emission with CIE 1931 chromaticity coordinates of x = 0.16 and y = 0.13, which is due to the influence of a higher shielding effect. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 501–514, 2008     

Nanostructured Hybrid Systems with Rhodamine 6G

We synthesized hybrid materials by sol-gel process, using: methyltriethoxysilane, tetraetylorthosilicate and vinyltriethoxysilane, in the presence of Rhodamine 6G. It was synthesized as well organic-inorganic hybrids with addition of tetraisopropyl orthotitanate and maleic anhydride UV-VIS spectra of dye show two absorption peaks at 499 nm (dimer) and 530 nm (monomer). Evaluating FTIR spectra of hybrid films, it was observed a band at 1077 cm^?1, characteristic of the asymmetric Si-O-Si stretching vibration in oligomer. Fluorescence spectra show that tetraisopropyl orthotitanate presence in the composites modifies the nature of the inorganic matrix and affects the interaction with the added dye.     

Synergetic activation of carbon dioxide molecule using phenylazomethine dendrimers as a catalyst

Phenylazomethine dendrimers bearing a cobalt porphyrin core act as catalysts for CO₂ reduction in the presence of a strong Lewis acid such as lanthanide trifluoromethanesulfonate (Ln(OTf)₃). We investigated the catalytic activity using electrochemical measurements (cyclic voltammetry) on a glassy carbon electrode in a DMF solution. Dissolving CO₂ gas into the solution, the cyclic voltammograms displayed an irreversible increase of the cathodic current. This result suggests the catalytic reduction of CO₂. The redox potential (–1.3 V versus Fc/Fc⁺) at which the catalytic behavior was observed is 1.1 V higher than that catalyzed by cobalt tetraphenylporphyrin (CoTPP). The generation number (n) dependence of the dendrimer catalysts showed the maximum activity at n = 3. A significant decrease of the activity for the largest dendrimer (n = 4) indicates a steric effect, which prevents transmission of the substrate (CO₂ molecule) and electrons to the catalytic center (cobalt porphyrin core). For more efficient catalysis, a novel open-shell dendrimer having a pocket on one side of the molecule was designed and synthesized. Because the accessibility to the core in the opened shell improved, this dendrimer exhibited the highest catalytic activity. These results suggest that tuning of the local domain around the cobalt porphyrin center would lead to a decisive solution for further activation of the CO₂ molecule. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5229–5236, 2006     

Theoretical and experimental characterization of amino‐PEG‐phosphonate‐terminated Polyphosphorhydrazone dendrimers: Influence of size and PEG capping on cytotoxicity profiles

The synthesis of new series of PPH (poly(phosphorhydrazone)) dendrimers with amino‐PEG phosphonates or the corresponding amino‐PEG phosphonic acids as terminal groups is presented, from generations 1–3. The size of PEG‐terminated dendrimers is experimentally measured by diffusional NMR, and by means of dynamic light scattering. Classical molecular dynamics and well‐tempered metadynamics simulations are used to assess or confirm the formation of aggregates in some cases. The influence of PEG capping on the cytotoxicity profiles of the dendrimers is evaluated on human peripheral blood mononuclear cells by means of LIVE/DEAD assays, and confirms the importance of PEG capping to ensure low cytotoxicity. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 761–774     

A Transparent Thin Film with Hexagonal Mesostructure Containing Rhodamine 6G

A transparent this film was prepared by depositing the sol-gel mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G(R6G) dye on glass substrates. The film of silica-surfactant-R6G materials, which was identified to possess hexagonally ordered mesostructure,was composed of nanocrystallites about 35 nm in diameter and 1-10μm in thickness. Cleanness of the substrates, concentration of the sol-gel mixture and rate of evaporation of the solvent were the key factors affecting transparency and homogeneity of the film. Moreover,optical change and lack in dye aggregation were observed to the R6G-functionalized MCM-41 thin film in contrast with that in ethanol solution.     

Simultaneous Determination of Fluorescein, Rhodamine 6G and Rhodamine B in Turbid Solution by Polarization Variable-Angle Synchronous Fluorescence Spectrometry

Fluorescencespectron1etry,inpractice,ishardto'beappliedtomulti-componentanalysisduetothespectraloverlapofcomplexn1ixtures.MoredVer,enVironmentalsan1plesandbiologicalsamplesareoftenturbidiand'the'directdetern1intitjodsofsuchsampleswouldsufferfromthesignificantinterferenceofscatteringlight.Synchronousfluorescencespectrol11etryisbecomingpopularconcerningitssimpIicity,selectivityandsensitivityindealingwithcomplexsamples.Onedrawbacktoconventionalconstant-wavelengthsynchronousfluorescencespectromet…     

Luminescent Blooming of Dendronic Carbon Nanotubes through Ion‐Pairing Interactions with an EuIII Complex

A multiwalled carbon nanotube (MWCNT) scaffold was covalently functionalized with a second‐generation polyamidoamine (PAMAM) dendron, presenting four terminal amino groups per grafted aryl moiety. These reactive functions were alkylated to obtain a positively charged polycationic dendron/carbon nanotube system ( d‐MWCNTs?Cl ), which eventually underwent anion exchange reaction with a negatively charged and highly luminescent Eu^III complex ( [EuL₄]?NEt₄ , in which L =(2‐naphtoyltrifluoroacetonate)). This process afforded the target material d‐MWCNTs?[EuL₄] , in which MWCNTs are combined with red‐emitting Eu^III centers through electrostatic interactions with the dendronic branches. Characterization of the novel MWCNT materials was accomplished by means of TGA and TEM, whereas d‐MWCNTs?Cl and d‐MWCNTs? [EuL₄] further underwent XPS, SEM and Raman analyses. These studies demonstrate the integrity of the luminescent [EuL₄]^? center in the luminescent hybrid, the massive load of the cationic binding sites, and the virtually complete anion‐exchange into the final hybrid material. The occurrence of the ion‐pairing interaction with MWCNTs was unambiguously demonstrated through DOSY NMR diffusion studies. Photophysical investigations show that MWCNTs?[EuL₄] is a highly soluble and brightly luminescent red hybrid material in which MWCNTs act as photochemically inert scaffolds with negligible UV/Vis absorption, compared with the grafted Eu complex, and with no quenching activity. The high dispersibility of MWCNTs?[EuL₄] in a polymer matrix makes it a promising luminophore for applications in material science.     

吖啶橙-罗丹明6G荧光共振能量转移及其罗丹明6G荧光猝灭法测定蛋白质

研究了吖啶橙(AO)与罗丹明6G(R6G)之间能量转移的最佳条件。在pH=7．20的Tirs-HCl缓冲溶液,十二烷基苯磺酸钠介质中,AO-R6G能够发生有效能量转移,使R6G荧光增强。蛋白质的加入使R6G荧光猝灭,以此建立了利用AO-R6G荧光共振能量转移间接测定蛋白质的新方法。牛血清白蛋白、人血清白蛋白工作曲线线性范围分别为1．0～31和1．0—30mg／L;检出限分别为0．32和0．33mg／L;平行6次测定相对标准偏差为1．1％～2．0％;回收率为96．7％～103．2％。此方法的稳定性好,选择性高,用于人血清试样中总蛋白含量的测定,与常用的双缩脲法基本一致。     

Novel Biopolymer Structures Synthesized by Dendronization of 6‐Deoxy‐6‐aminopropargyl cellulose

Propargyl cellulose with regioselective functionalization pattern was synthesized by nucleophilic displacement reaction of 6‐O‐toluenesulfonyl ester of cellulose (degree of substitution, DS 0.58) with propargyl amine. The novel 6‐deoxy‐6‐aminopropargyl cellulose provides an excellent starting material for the selective dendronization of cellulose at position 6 via the copper‐catalyzed Huisgen reaction yielding 6‐deoxy‐6‐amino‐(4‐methyl‐[1,2,3‐triazolo]‐1‐propyl‐polyamido amine) cellulose derivatives of first‐ (DS 0.33) and second (DS 0.25) generation, which are soluble in polar aprotic solvents. The novel biopolymer derivatives were characterized by elemental analysis, FT‐IR spectroscopy, and one‐ and two dimensional NMR spectroscopy, showing no side reactions (cross‐linking) or impurities and no conversion at the secondary positions.

     

钨与溴邻苯三酚红—罗丹明6G协同显色的研究及其应用

本文研究了聚乙二醇辛基苯基醚存在下，在硫酸介质中，钨与溴邻苯三酚红和罗丹明６Ｇ双试剂协同显色反应，反应结果形成红色络合物，最大吸收波长５７８ｎｍ，表观摩尔吸光系数４．４１×１０＾５Ｌ．ｍｏｌ＾－１．ｃｍ＾－１。钨量在０－８μｇ／２５ｍｌ范围内符合比尔定律。     

Effect of pressure on the luminescence of a series of methoxy phenylacetylene dendrimers neat and in dilute solution in solid poly(tert‐butyl methacrylate)

The effect of pressure up to 60 kbar was measured on the luminescence peak location and efficiency for a series of methoxy phenylacetylene dendrimers (MeO). Dendrimers MeO‐3, MeO‐7, MeO‐15, MeO‐31, MeO‐63, and MeO‐127 were studied as neat polymers. MeO‐3, MeO‐15, MeO‐63, and MeO‐127 were also investigated in dilute solutions in poly(tert‐butyl methacrylate). According to measurements of the dilute solutions, there is a charge‐transfer (CT) state that, for the smaller dendrimers, lies well above the π* state; for the larger dendrimers, it is the emitting state at 1 atm. With increasing pressure, the intramolecular CT state is rapidly stabilized, so that at high pressure the emission is from this state for all dendrimers. For the neat polymers, there is an initial redshift that reverses direction at a pressure that is higher for smaller dendrimers. This reversal is attributed to intermolecular CT. There may be changes in the molecular geometry and/or relative orientation of adjacent dendrimers that tend to stabilize the intermolecular CT in the solid state. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2859–2865, 2001     

Polyamido amine dendrimers functionalized with poly(phenylenevinylene) dendrons at their periphery

A series of polyamido amine (PAMAM) dendrimers (Generations 2, 3, 4, and 6) fully functionalized at their periphery with first‐ and second‐generation poly (phenylenevinylene) (PPV) dendrons have been efficiently prepared. MALDI‐TOF mass spectrometry proved to be particularly useful for the characterization of the new hybrid dendrimers as well as for the estimation of the average number of PPV dendrons attached to the surface. The optical absorption and emission properties of these systems were studied. The materials display extremely high molar extinction coefficients and emit blue light with only slightly lower fluorescence quantum yields than the corresponding free dendrons. Self‐quenching interactions between PPV units were not observed in THF. However, the luminescence properties underwent a dramatic change when toluene was used as the solvent. The lower polarity of toluene caused shrinkage of the PAMAM structure and brought the PPV chromophores closer together, leading to self‐quenching interactions and excimer formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6409–6419, 2009     

A Chemiluminescence Reaction Between Hydroxyl Radical and Rhodamine 6G and its Applications

Abstract

A novel chemiluminescence (CL) reaction between hydroxyl radical and ascorbic acid is described in this paper. Hydroxyl radical generated on line by the reaction between Fe³⁺ solution and H₂O₂ solution in HCl medium could oxidize rhodamine 6G to produce weak chemiluminescence. It was found that ascorbic acid could enhance the chemiluminescence and the excited rhodamine 6G was the emitter of the chemiluminescence reaction. The possible mechanism of the CL system was also discussed. Ascorbic acid can be determined in the range of 2.0×10^?6?8.0×10^?4 mg/ml with a detection limit of 1×10^?6 mg/ml (3σ). A complete analysis could be done in 1 minute with the relative standard deviation of 3.1% for 5.0×10^?5 mg/ml (n=11). In order to study the chemiluminescence reaction further, the application to the determination of ascorbic acid in food using the chemiluminescence reaction combined with flow injection is investigated.     

Photoresponsive nanocarriers based on PAMAM dendrimers with a o‐nitrobenzyl shell

Gn (n = 3, 4, and 5) poly(amidoamine) (PAMAM) dendrimers were synthesized and peripherally modified with photocleavable o‐nitrobenzyl (NB) groups by reacting o‐nitrobenzaldehyde with the terminal amine groups of PAMAM dendrimers, followed by reducing the imine to amine groups with NaBH₄. The NB‐modified dendrimers, Gn‐NB (n = 3, 4, and 5), were characterized by nuclear magnetic resonance and fourier transform infrared spectroscopy. The results showed that the NB groups were successfully attached on the periphery of the dendrimers with near 100% grafting efficiency. Such a photosensitive NB shell could be cut off on irradiation with 365 nm ultraviolet (UV) light. The encapsulation and release of guest molecules, that is, salicylic acid (SA) and adriamycin (ADR), by Gn‐NB were explored. The encapsulation capability of these dendrimers was found to increase as the guest molecular size was decreased and have dependence on the generation of dendrimers as well. For both of SA and ADR, the average encapsulation numbers per dendrimer decreased in the order of G4‐NB > G5‐NB > G3‐NB, indicating that the fourth generation dendrimer was a better container for the guest molecules. The rate of SA release was found to be greater with UV irradiation than that without, suggesting that the NB‐shelled PAMMAM dendrimers could function as a molecular container/box with photoresponsive characteristics. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 551–557, 2010     

银表面罗丹明6G的电化学表面增强拉曼光谱研究

罗丹明6G（Rhodamine 6G,R6G）是单分子表面增强拉曼光谱（SM-SERS）研究中最常用的探针分子之一,对R6G分子在表面吸附行为的研究有助于了解R6G分子和表面的相互作用. 本文应用电化学和电化学表面增强拉曼光谱技术,研究不同电位下R6G的银电极表面的吸附行为. 结果表明,随着电位负移罗丹明6G在银表面上从垂直吸附转为倾斜吸附,该变化和碱性条件下吸附于金纳米粒子上R6G的吸附构象一致. 这说明,在部分单分子实验中所发现的R6G反常光谱其来源是单个R6G分子在表面吸附取向变化. 本研究对后续详细分析SM-SERS研究中单分子SERS谱峰变化的机制有一定的参考价值.     

UV‐photodimerization in uracil‐substituted dendrimers for high density data storage

Two series of uracil‐functionalized dendritic macromolecules based on poly (amidoamine) PAMAM and 2,2‐bis(hydroxymethylpropionic acid) bis‐MPA backbones were prepared and their photoinduced (2π+2π) cycloaddition reactions upon exposure to UV light at 257 nm examined. Dendrimers up to 4th generation were synthesized and investigated as potential materials for high capacity optical data storage with their dimerization efficiency compared to uracil as a reference compound. This allows the impact of increasing the generation number of the dendrimers, both the number of chromophores, as well as the different steric environments, on the performance of each series of dendrimers to be investigated. The (uracil)₁₂‐[G‐2]‐bis‐MPA and (uracil)₈‐[G‐1]‐PAMAM were observed to have high dimerization efficiency in solution with different behavior being observed for the PAMAM and bis‐MPA dendrimers. The dendrimers with the best dimerization efficiency in solution were then examined in the solid state as thin films cast on quartz plates, and their film qualities along with their photodimerization performance studied. High quality films with a transmission response of up to 70% in 55 s. when irradiated at 257 nm with an intensity of 70 mW/cm² could be obtained suggesting future use as recording media for optical data storage. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4401–4412, 2007     

Facile synthesis of dendrimers combining aza‐Michael addition with Thiol‐yne click chemistry

We report a highly efficient approach to prepare dendrimers by taking advantage of the orthogonal characteristic of aza‐Michael addition and thiol‐yne reactions. A fifth generation dendrimer was synthesized within five steps without protection/activation procedures. The reactions proceed under benign conditions without byproducts, and the target products can be easily purified via extraction or precipitation without chromatography. The structure of each generation dendrimer was characterized using NMR spectroscopy, size exclusion chromatography, and mass spectrometry. The obtained dendrimers can have peripheral amine or alkyne groups. We demonstrated that these groups can be used for selective and specific conjugation with various functional groups. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Vinyl‐terminated liquid‐crystalline dendrimers based on dendritic polyols and their siloxane‐based elastomers

A new series of side‐chain liquid‐crystalline dendrimers (LCDs) by grafting vinyl‐terminated phenyl benzoate‐based promesogens to a novel polypropyleneimine‐derived dendritic polyols are reported. Polarized optical microscopy and X‐ray diffraction studies show that both the compounds display a smectic‐A (SmA) mesophase. The second‐generation dendrimer bearing eight‐branched promesogens exhibits a more stable SmA mesophase with a wide mesomorphic temperature range. It is demonstrated that “promoting groups” in the structure of LCD for the enhancement of mesomorphic stability are unnecessary in the case of strong anisotropic interactions. In contrast to conventional LCDs, these two compounds possess reactive vinyl terminals that endow them with the potential for the preparation of polymeric materials. For the first time, a type of thermoset elastomers is explored from LCDs via hydrosilylation crosslinking reaction of vinyl terminals and siloxane crosslinker. Two‐dimensional X‐ray diffraction study indicates that the lamellar structures of original dendrimers are reserved in the elastomer networks. Stress–strain curves reveal that these elastomers exhibit excellent elasticity under successive uniaxial compression. The combination of anisotropic structures of rigid units and elasticity of flexible networks in this novel series of elastomers makes them promising candidates for the application in artificial muscles or cartilages. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013