Search

The synthesis of Ag nanoparticles stabilized Poly(N,N’-methylene bis-acrylamide N-aminoethyl piperazine)(MBA-AEPZ) was reported. The effects of hyperbranched polymer generation number on the size and size distribution of Ag nanoparticles were studied, which were determined from the UV plasmon absorption spectra and transmission electron microscopic (TEM) analysis. These data show that the changes of size (8.7, 9.6 and 10.2 nm) were observed with increase in Poly(MBA-AEPZ) generation number (1, 3 and 5) at the same Ag+:NH2 group ratio (M:D). [ABSTRACT FROM AUTHOR]

Two azopolymers (DACENO2 and DACEOCH3) with a special structure were designed and synthesized. The azopolymer films doped with the lanthanide complex Eu(TTA)3Phen were prepared by a casting method with a mixed solution of the azopolymer and lanthanide complex. UV-vis spectra show that the absorption peaks of the predesigned azopolymers DACENO2 and DACEOCH3 are separated from that of Eu(TTA)3Phen. Under this circumstance, the photo-induced anisotropy of the films could not be destroyed by excitation and emission during fluorescence measurements. Polarized luminescence of both oriented films was observed with polarization ratios of 3.0 for the DACENO2–Eu(TTA)3Phen film and 2.7 for the DACEOCH3–Eu(TTA)3Phen film at 613 nm, respectively. The luminescent properties of the film were found to be affected by the chemical structure of the azopolymer, the extent of the photo-induced alignment and the angle between the orientated direction of the film and the direction of the polarizer. All the results from this work revealed that the polarized luminescence from the azopolymer film doped with a lanthanide complex can be controlled by the extent of photo-induced alignment. [ABSTRACT FROM AUTHOR]

An azobenzene mesogen-substituted polydiacetylene which self-assembles into stacks with bilayered two-dimensional structure is investigated in detail by transmission electron microscopy (TEM) as well as X-ray diffraction (XRD). These stacks with bilayer-structure are found to be organized into highly ordered lamellar crystal structures. The substituted polydiacetylene assemblies form a blue phase at room temperature, however, they undergo a well-known thermochromic transition in response to thermal stimulus. In this work, we establish links between chromatic transitions, molecular organization and the morphology of these assemblies. This thermochromic transition has been subjected to detailed investigation by means of Fourier transform infrared spectroscopy (FTIR), XRD as well as TEM. These results demonstrate that the strong intermolecular interaction (π–π stacking) between azobenzene mesogens is essential for complete recovery of chromatic transitions of PDA1 films following thermal stimulation. [ABSTRACT FROM AUTHOR]

A series of new liquid crystalline copolymers, poly[((S)?2?methyl?1?butyl methacrylate)?co?(6?(4?(4?cyanophenylazo)phenoxy)hexyl methacrylate)], with different contents of chiral units of 17, 36, 54 and 78 mol% were synthesized. The structures and properties of the copolymers were characterized and evaluated using infrared, 1H NMR and UV spectroscopy, differential scanning calorimetry, gel permeation chromatography and circular dichroism (CD). The CD results suggested that absorptions of azobenzene chromophores were observed in films of copolymer containing 17, 36 or 54 mol% chiral units, but not in the film of copolymer containing 78 mol% chiral units. Also, CD values of the copolymeric films decreased with increasing chiral content. After irradiation with linear polarized light at 442 nm, CD values were changed in all the copolymeric films, and the CD values increased with decreasing chiral content in a nonlinear way, while the photoinduced change of chirality of the copolymers increased in a linear way with decreasing chiral content. The results are discussed in terms of interactions between structures and chiroptical properties. Copyright © 2007 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Ag colloidal particles stabilized by poly (N,N′‐methylene bis‐acrylamide N‐aminoethyl piperazine) (MBA‐AEPZ) were prepared. The Ag ion concentration and reaction temperature were studied on the size and size distribution of Ag colloidal particles, which were determined from the ultraviolet (UV) plasmon absorption band and transmission electron microscopic (TEM) analyses. The data show that poly(MBA‐AEPZ) behaves like lower molecular mass stabilizers; some polymers surround the surface of the Ag colloidal particles and the particle size can be controlled by a change in the Ag ion concentration and reaction temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3701–3705, 2007 [ABSTRACT FROM AUTHOR]

A step-index polymer optical fiber (SI POF) with a core of poly(methyl methacrylate) (PMMA) containing Eu(DBM)3Phen has been fabricated by a preform technique. Fluorescence analysis showed that there is not obvious change in the local environment around Eu3+with the increase of Eu(DBM)3Phen doping concentration. Amplified spontaneous emission (ASE) phenomenon of the doped SI POF by end-pumping with an Ar+-laser of 457.9 nm at ambient temperature was observed. The threshold of the pump power for the onset of ASE is found to be 120 mW for the doped SI POF with a length of 50 cm, the length is also found to be the optimal length for maximum ASE power under the input power of 200 mW. The maximum quantum conversion efficiency of the fiber is about 40%. [ABSTRACT FROM AUTHOR]

Eu(DBM)3 phen-doped poly(methyl methacryate) (PMMA) with different doping concentration were prepared. The highest doping concentration sample (10000 ppm) was examined by near-field scanning optical microscopy (NSOM) with a resolution of 50 nm; and the result showed that there were no aggregates larger than 50 nm in the doped polymer. This result was further confirmed by optical properties of the doping material. Concentration quenching was not detected by metastable-state lifetime measurements, indicating that no aggregates existed. According to the fluorescence spectra analysis, the relative intensity ratio (R) of 5D0 → 7F2 to → 5D0 → 7F1 transition was not shown to be significantly changed with the increasing of Eu3+ content. The analysis reflected that the local structure and asymmetry in the vicinity of europium ions were not changed, and that the Eu3+ ions in PMMA were homogeneously dispersed. [ABSTRACT FROM AUTHOR]

Examines the radiative properties of Eu(DBM)[sub3]Phen-doped poly(methyl methacrylate). Significance of rare-earth ions containing polymers; Chemical structure of Eu(DBM)[sub3]Phen; Fluorescence emission spectra of Eu(DBM)[sub3]Phen-doped poly(methyl methacrylate).

One-dimensional silver nanorods and nanodisks have been successfully synthesised through a facile method of the polymer template-assisted synthesis. The sample was characterised by a variety of techniques, such as transmission electron microscopy (TEM), scan electron microscopy (SEM) and a UV–vis spectrometer. The as-obtained nanorods and nanodisks are single crystalline with an average size of about 150 nm up to 500 nm. During the whole process, the capping stabiliser (PDMAEMA-b-PVP) and pH played important roles in the growth of the nanorods and nanodisks. A possible growth mechanism was proposed. [ABSTRACT FROM AUTHOR]

Herein, photo-controlled inclusion and exclusion reaction of azobenzene-containing polydiacetylene vesicles with α-cyclodextrin were used to act as driving force to induce chromatic transition of PDA vesicles, which provided a novel model system that combines photochemistry and host–guest chemistry for a photo-stimulus-responsive vesicle. [ABSTRACT FROM AUTHOR]

The stability of the scattering loop is fundamental for coherent random lasing in a dynamic scattering system. In this work, fluorescence of DPP (N, N-di [3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide) is scattered to produce RL and we realize the transition from incoherent RL to coherent RL by controlling the Brownian motion of the scatterers (dimer aggregates of DPP) and the stability of scattering loop. To produce coherent random lasers, the loop needs to maintain a stable state within the loop-stable time, which can be determined through controlled Brownian motion of scatterers in the scattering system. The result shows that the loop-stable time is within 5.83 × 10−5 s to 1.61 × 10−4 s based on the transition from coherent to incoherent random lasing. The time range could be tuned by finely controlling the viscosity of the solution. This work not only develops a method to predict the loop-stable time, but also develops the study between Brownian motion and random lasers, which opens the road to a variety of novel interdisciplinary investigations involving modern statistical mechanics and disordered photonics. [ABSTRACT FROM AUTHOR]

We have reported the realization of a plasmonic random fiber laser based on the localized surface plasmonic resonance of gold nanoparticles (NPs) in the liquid core optical fiber. The liquid core material contains a dispersive solution of gold NPs and laser dye pyrromethene 597 in toluene. It was experimentally proved that the fluorescence quenching of the dye is restrained in the optical fiber, which is considered one of the main sources of loss in the traditional laser system. Meanwhile, the random lasing can be more easily obtained in the random laser system with more overlap between the plasmonic resonance of the gold NPs and the photoluminescence spectrum of the dye molecules. [ABSTRACT FROM AUTHOR]

Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss POF materials, POF photosensitivity, techniques and issues of fabricating POF gratings, as well as various types of POF gratings. [ABSTRACT FROM AUTHOR]

A ternary system composed of Tb(DBM)3Phen (TbDP), Eu(DBM)3Phen (EuDP), and poly(N-vinylcarbazole) (PVK) was prepared with good thermal stability and the photoluminescence (PL) was studied. By comparing their emissions, it was found that energy transfer exists from PVK to lanthanide complexes in the ternary system. It also was found that the lifetime of 5D0 of Eu3+ in the ternary system is longer than that of the binary system of EuDP and PVK, but the lifetime of 5D4 of Tb3+ in the ternary system is shorter than that of the binary system of TbDP and PVK, showing evidence of energy transfer from TbDP to EuDP. Temperature-dependent PL spectra of the ternary system from 9 to 300 K further showed there is a change in energy transfer efficiencies from Tb3+ ions to Eu3+ ions at different temperature ranges, which not only is more evidence of energy transfer but also can be used as a temperature detector or a thermal-sensitive probe of a optical fiber sensor. [ABSTRACT FROM AUTHOR]

Two kinds of nanometer-size silver-coated polydiacetylene (PDA) composite vesicles were prepared by simple and effective approaches. Silver nanoparticles were coated onto the outer and inner surface (I) or only on the outer surface of PDA vesicles (II), respectively. UV-vis spectra and transmission electron microscopy (TEM) were used to confirm the formation of PDA/Ag nanocomposite vesicles. Nonlinear optical (NLO) properties of these PDA/Ag nanocomposite vesicles had been measured by the Z-scan technique. The value of n2 for pure PDA vesicles was 1.2 × 10[?]14 cm2 W[?]1. However, for PDA/Ag nanocomposite vesicles (on the outer surface) it was 7.3 × 10[?]14 cm2 W[?]1. Nearly seven times enhancement was observed as a result of local field enhancement under the surface plasmon resonance of silver nanoparticles at the interface. NLO properties of these PDA/Ag nanocomposite vesicles can be modulated by varying the size, shape and coverage of Ag nanoparticles and these PDA/Ag nanocomposite vesicles are expected to be good candidates for new optical and nonlinear devices. [ABSTRACT FROM AUTHOR]

Abstract  The quantitative structure-property relationship (QSPR) study was performed between descriptors representing the molecular structures and refractive indices for a set of 35 π-conjugated polymers. A seven-descriptor correlation was developed for the prediction of refractive indices with R = 0.936 and s = 0.028 by stepwise multilinear regression analysis. The average relative error for the calculation of refractive indices was 1.022%. The stability of the proposed model was validated using leave-one-out cross-validation and randomization experiments. Since the model requires only molecular descriptors derived solely from the repeating unit structures of conjugated polymers, it has better predictive capability comparing with the existing group-contribution methods. Figure Plot of the calculated, the cross-validated vs. experimental n 2500 of conjugated polymers

1,7-Dibromo-substituted perylene bisimides have been obtained in yields of at least 60%in regioisomerically pure form by treating the commonly used dibromoperylene-3,4,9,10- tetracarboxylic dianhydride with 2-(diethylamino)ethylamine or 2-(dimethylamino)ethylamine and then separating the 1,7-isomer from the regioisomeric mixtures by conventional column chromatography and without recrystallization. The individual regioisomers were fully characterized by 1H NMR spectroscopy and HRMS. The signals of the protons located in the aromatic region and neighboring the imide nitrogen atom were utilized to confirm the chemical structures of the isomers. The 1,7-dibromo isomer obtained with 2-(dimethylamino)ethylamine in such a convenient and efficient way was further used to prepare 1,7-disubstituted perylene bisimide derivatives by saponification, amidation, and then bay-position substitution reactions. These compounds exhibited a significant redshift and broadening of their absorption and emission in optical spectroscopy analysis. [ABSTRACT FROM AUTHOR]

We demonstrate the realization of a coherent random fiber laser (RFL) in the extremely weakly scattering regime, which contains a dispersive solution of polyhedral oligomeric silsesquioxanes nanoparticles (NPs) and laser dye pyrromethene 597 in carbon disulfide that was injected into a hollow optical fiber. Multiple scattering of polyhedral oligomeric silsesquioxanes NPs greatly enhanced by the waveguide confinement effect was experimentally verified to account for coherent lasing observed in our RFL system. This Letter extends the NPs-based RFLs from the incoherent regime to the coherent regime. [ABSTRACT FROM AUTHOR]

The luminescence of Nd(DBM) 3 (H 2 O) 2 -, Nd(DBM) 3 Phen-, and Nd(DBM) 3 (TOPO) 2 -doped polymethyl methacrylate (PMMA) was investigated under excitation at 17,100 cm -1 ( 4 I 9/2 ? 4 G 7/2 ). The 4 F 3/2 ? 4 I 11/2 transition of the Nd(DBM) 3 (TPPO) 2 -doped PMMA showed the strongest intensity. In order to predict the radiative properties of Nd(DBM) 3 (TOPO) 2 -doped PMMA, its absorption spectrum was measured and Judd-Ofelt parameters (O 2 , O 4 , O 6 ) were calculated. The values of the radiative lifetime and the emission cross-section of 4 F 3/2 ? 4 I 11/2 transition are comparable with those shown by glasses used in solid state laser applications. It can be concluded that Nd(DBM) 3 (TOPO) 2 -doped PMMA is an efficient luminescent material. [ABSTRACT FROM AUTHOR]

In this article, the normalized excitation spectra corresponding to 616 and 470 nm fluorescence and normalized fluorescence spectrum excited by 335 nm of Eu doped polymer fiber of different concentration are analyzed and compared to indicate the possibility of Eu2+ and Eu3+ ions'' coexistence. And the spectra analysis shows fractal clusters'' existence in higher concentration. At the same time, the clusters'' existence was proved by near-field results of scanning near-field optical microscopy. [Copyright &y& Elsevier]

Using near-field scanning optical microscopy (NSOM), we explore the chromatic dispersion and absorption characteristics of fractal clusters in Eu doped polymer fiber. We present the near-field transmitted light intensity of fiber slice. The near-field light intensity of dots with clusters and without clusters is analyzed and compared and the agreement is obtained between experiment and theory which is based on the effective-medium approximation (EMA) and the differential effective-medium approximation (DEMA) of fractal clusters, respectively. [Copyright &y& Elsevier]