Fabrication of polymer dot pattern containing fluorescent molecules by laser photopolymerization

A simple and easy method for micro-patterning of organic molecules was developed. Fluorescent molecules were added to an ultraviolet (UV) photopolymerization polymer solution, and dot patterns were formed by a photopolymerization process with a conventional nanosecond pulsed UV laser. Since the molecules fixed in the dot pattern showed fluorescence corresponding to the added molecules in all cases, it is suggested that this method is applicable to micro-patterning of various kinds of organic molecules without serious damage to the molecules. Micro-patterning was also achieved using a visible pulsed laser by adding coumarin 6 to the polymer solution.PACS 82.50.Hp; 81.65.Cf; 81.05.Lg     

卟啉基非金属纳米片用于可见光光催化制氢

本文基于密度泛函理论预测了一种用于可见光范围光催化制氢的新型二维非金属纳米材料,该材料可以由HTAP分子脱氢聚合得到,具有良好的结构稳定性,且带隙为2.12 eV,可以实现可见光区域的光捕获. 材料的带边能级位置恰好包裹水的氧化还原电位,有利于实现全光解水. 电子的迁移率略高于空穴的迁移率,有利于光生载流子的分离. 光生电子可以提供足够的驱动力使得析氢反应自发进行.     

Visible light sensitization effect of polyaminobenzoate adsorbed on TiO2 nanocrystal surface

Poly-o-aminobenzoate (POA) was prepared by oxidizing o-aminobenzoic acid with (NH₄)₂S₂O₈ in an acidic solution. POA was adsorbed on TiO₂ nanocrystal surface to obtain a POA-TiO₂ nanocomposite. The polymerization reaction, structure, adsorption reaction on TiO₂ surface, and visible light sensitization effect of the polymer adsorbed on TiO₂ surface were studied by FT-IR and UV-visible spectra, cyclic voltammetry, and measurements of visible light photoelectrochemical and photocatalytic activities. Three kinds of POA with different long conjugate structures can be formed. These polymers have large absorbance in wide visible light region. POA molecules can be adsorbed on TiO₂ surface by anchoring their carboxylate groups to the TiO₂ surface with a multi-bridging chelating mode, which causes formation of the POA-TiO₂ nanocomposite with a high stability. POA adsorbed on the TiO₂ nanocrystal showed high visible light sensitization effect in the photocatalytic reaction.     

Polymer surface patterning by laser scanning

Proposed work develops method of polymer surface patterning, suggested in our laboratory. Surface structures with different symmetry and shape are prepared on PMMA and photoresist (Su-8) surface. For surface modification, periodic laser scanning from confocal microscope was used. For optical response improvement meso tetraphenylporphyrine was added either in the polymer bulk or on the top of pristine polymer by vacuum evaporation method. Applications of vacuum deposition methods allow increasing applicability of the technique and preparation of more complex structure. Parameters of the created structures were studied with the aim to better understand the driving forces of the surface modification. Application of prepared structures in photonics as diffraction grating or light coupling elements is also given.     

Transparent and UV-Reflective Photonic Films and Supraballs Composed of Hollow Silica Nanospheres

For an optically transparent, UV-reflective film, hollow silica nanospheres smaller than the visible wavelength (<λ_vis) are prepared and assembled into colloidal glasses, of which interstices are then backfilled with a polymer. The polymer refractive index is matched with the silica shell to minimize backscattering in the visible range, and the average distance between the hollow silica particles is adjusted by tuning the shell thickness to satisfy the interference resonance condition for a UV selective reflection. The resulting composite film shows a strong UV reflection as expected, but it is translucent in visible light due to non-negligible backscattering, which may be caused by large defects or fluctuation of the particle concentration. In order to avoid such backscattering, another polymer is introduced of which the refractive index is matched with the average refractive index of the hollow nanospheres. This allows an optically transparent film that selectively reflects the UV light. Furthermore, spherical aggregates of hollow silica nanospheres called “supraballs” are prepared and their average refractive index is matched with a solvent by adjusting the mixture ratio of water and ethylene glycol, which yields an optically transparent solution, selectively reflecting UV.     

Photoelectric organic nano-thin films prepared from diarylethene

A photoactive nano-film was prepared from a diarylethene derivative, 1,2-bis[6-(3,4-ethylenedioxythienyl)-2-methyl-1-benzothiophen-3-yl]perfluorocyclopentene (BTFTT) and 3,4-ethylenedioxythiophene (EDOT), by electrochemical anodic polymerization. The conductive polymer films prepared from a copolymer of BTFTT and EDOT, a homopolymer of PBTFTT and PEDOT, showed characteristic redox properties pertinent to their monomers and homopolymers as determined by cyclic voltammetry (CV). The growth of organic films was estimated by an alpha-step and UV–visible spectral change. The film growth (thickness) was linearly correlated to the cycle numbers in CV for the electropolymerization. The electrodeposited organic nano-film showed a reversible photocurrent switching effect in a liquid electrolyte solution containing redox couple (Q/H₂Q) by the alternative UV irradiation (0.1 W/cm⁻²). Maximum photocurrent switching efficiency as well as fast response were obtained from the polymer film synthesized from a solution containing equivalent molar concentration of EDOT and BTFTT (1:1).     

Polyethylene welding by pulsed visible laser irradiation

Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as “through transmission visible laser welding”. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part.In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.     

Micro-patterning of multiple organic molecules by laser implantation

Micrometer pixelated arrays comprised of different functional organic molecules were formed on a polymer film using a laser implantation and transfer dry processing technique. The spatial distribution of the implanted organic molecules and the extended pattern that they formed could be controlled with high resolution as determined using fluorescence microscopy. The individual molecular implant pixels had a diameter of less than 4 m. This method of molecular manipulation is both precise and reproducible and could therefore be used in many applications such as molecular devices, molecular sensors, non-linear optical devices, drug delivery and opto-electronic displays. PACS 81.05.Lg; 81.16.Mk; 81.65.Cf     

Successive preparation of decorated zinc oxide organic sol by pulsed laser ablation and their luminescence characteristics

Nano-ZnO organic sols which were modified in situ were successively produced through focused pulsed laser ablation of ZnO target in interface of solid and flowing liquid which contained modification agents or polymer. It is found that the ZnO ethanol sol decorated by Q (8-hydroxylquinoline) radiates intense green light under ultraviolet radiation and has a broad emission band centered at 555 nm in the emission fluorescence spectrum. The influence of factors including different modification agents and their added methods, laser fluence, aging time after preparation, compositions of flowing liquid and their velocity on luminescence characteristics of nano-ZnO organic sol was characterized by TEM, UV-vis and fluorescence spectrum.     

Controlling the reversible wetting capability of smart photochromic-polymer surfaces by micro patterning

We demonstrate the wetting behavior control of polymer surfaces doped with photochromic molecules by modifying the surface patterning features introduced by soft molding lithography. Such surfaces enhance their hydrophilicity upon UV irradiation due to conversion of the non-polar spiropyran dopant molecules to their polar merocyanine isomers. The process is reversed upon visible light irradiation. By changing the topological parameters of the introduced pattern, one achieves surface tuning from hydrophobic to hydrophilic situations. The difference for the contact angles between UV- and green-irradiated surfaces may become significantly higher than for the flat surfaces, for the specific patterning parameters analyzed. PACS 42.62.-b; 68.08.Bc; 83.50.Uv; 42.70.Jk; 42.70.Gi     

Preparation of poly-o-phenylenediamine/TiO2/fly-ash cenospheres and its photo-degradation property on antibiotics

A series of poly-o-phenylenediamine/TiO₂/fly-ash cenospheres(POPD/TiO₂/fly-ash cenospheres) composites have been prepared from o-phenylenediamine and TiO₂/fly-ash cenospheres under various polymerization conditions. The properties of the samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), specific surface area (BET), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV-vis diffuse reflectance spectrum (UV-vis DRS). Photocatalytic activity was studied by degradation of antibiotics waste water under visible light. The results indicate that the photo-induced method is viable for preparing modified photocatalysts, and the modified photocatalysts have good absorption in visible light range. The photocatalysts of POPD/TiO₂/fly-ash cenospheres which have good performance are prepared at pH 3 and 4, and the polymerized time around 40 min. When the photocatalysts are prepared under the conditions of pH 3 and polymerized time 40 min, the degradation rate of roxithromycin waste water could reach near 60%, and it indicates that the way of POPD modified TiO₂/fly-ash cenospheres to degrade the antibiotics waste water is viable.     

Hollow polycarbonate fiber for Er:YAG laser light delivery

We developed hollow fibers with polycarbonate (PC) capillaries for use as a supporting tube. The PC capillaries were prepared by using a glass-drawing technique. Hollow PC fibers are safer and more flexible than hollow glass fibers because no fragments are released when the fibers are broken in various applications. Inner coating layers of silver and cyclic olefin polymer (COP) enhanced the reflection rate at the Er:YAG laser light wavelength. Using these fibers, we attained low loss for Er:YAG laser light transmission. By adjusting the drawing temperature in the fabrication of the PC capillaries, we created a smooth inner surface and uniform PC capillaries. We also demonstrated low-loss properties for visible pilot beams.     

Angle dependent laser nanopatterning of poly(ethylene terephthalate) surfaces

Interference effects can lead to the formation of ripple structures at laser-irradiated poly(ethylene terephthalate) surfaces. Poly(ethylene terephthalate) surface was irradiated with linearly polarized light of a pulsed 157 nm laser. In a certain range of irradiation parameters, the irradiation resulted in the formation of coherent ripples patterns. The dimension of the pattern depends on the angle of the laser beam incidence. The surface morphology of the nano-patterned poly(ethylene terephthalate) was analyzed by atomic force microscopy and focused ion beam-scanning electron microscopy. Oxygen concentration in the modified polymer surface was studied by angular resolved X-ray induced photo-electron spectroscopy. Gold nano-layers were consecutively sputtered onto the laser irradiated poly(ethylene terephthalate) surfaces. The morphology of the sputtered gold nano-layers was investigated with atomic force microscopy too. We found that the morphology of the gold nano-layers changes and depends on the surface pattern of the laser irradiated poly(ethylene terephthalate). Formation of gold “nano-hills” is observed at the ridges of the ripple structures. The amount of oxygen together with the morphology of prepared polymer pattern may be the dominant factors controlling the gold layer growth. The present results are compared with those obtained earlier on PET irradiated with krypton fluoride laser.     

共轭聚合物单分子构象和能量转移特性研究

利用基于宽场显微光学系统的单分子散焦成像技术测量了不同构象poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole](PFO-DBT)共轭聚合物单分子的光物理与动力学特性.通过分析共轭聚合物单分子的荧光轨迹和对应的发射偶极取向变化识别共轭聚合物单分子发光单元,发现延伸构象下的单分子呈现多发色团发光特性,而折叠构象下的单分子保持高效链间能量转移,呈现单个发色团发光特性.共轭聚合物单分子构象对能量转移效率的影响可用于研究基于共轭聚合物的光电器件和分子器件.     

A free-standing and thermostable polymer/plastic crystal electrolyte for all-solid-state lithium batteries

All-solid-state lithium batteries using flexible solid electrolytes instead of combustible organic liquid electrolytes are the ultimate solution to address the safety problem of commercialized lithium ion batteries. In this study, a free-standing and thermostable polymer/plastic crystal composite electrolyte (PPCE) based on polymerized trimethylolpropane trimethacrylate (TMPTMA)-1, 6-hexanediol diacrylate (HDDA) matrix, and plastic crystal electrolyte was prepared for all-solid-state lithium batteries. The polymerized TMPTMA-HDDA-based matrix of a porous network structure coupled with plastic crystal electrolyte (PCE) in the pores reveals good compatibility. The as-synthesized PPCE possesses excellent flexible performance, thermostability, and high conductivity, showing that PPCE can reach 8.53 × 10^?4 S cm^?1 with 7.5 wt% monomers (PPCE-7.5%) at 25 °C under a stability electrochemical window above 5.2 V. The assembled lithium batteries Li|PPCE|LiFePO₄ exhibit high capacity and highly cycling stability at room temperature, indicating great potential of all-solid-state lithium batteries.     

Charged particles detection: The graft-and-dye method

Charged particles travelling through an organic medium leave a trail of highly concentrated active, stable chemical radicals. These functions are able to initiate copolymerization reactions of unsaturated molecules. Such a reagent is made to reach the trail; polymerization occurs. If the new polymer formed either absorbs or emits light the track of the charged particle is made visible. This technique and results are discussed: the efficiency of those detectors has been increased, they do not exhibit any critical dip angle for the registration of particle tracks, they may offer a way to reveal tracks originating in the detector itself.     

Preparation of visible light responsive N doped TiO2 via a reduction-nitridation procedure by nonthermal plasma treatment

A visible light responsive N-doped TiO₂ was prepared via a reduction-nitridation procedure by nonthermal plasma treatment. X-ray diffraction, N₂ adsorption, UV-vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared TiO₂ samples. The plasma treatment did not change the phase composition and particle sizes of TiO₂ samples, but extended its absorption edges to the visible light region. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activities of TiO₂ prepared by reduction-nitridation procedure were much higher than that of samples prepared by simple nitridation treatment. The enhanced activity was ascribed to the substitutional N-doping and appropriate concentration of oxygen vacancies. TOHN10 prepared by reduction-nitridation procedure exhibited excellent photocatalytic stability. A possible mechanism for the photocatalysis was proposed.     

Influence of urea on polyvinyl alcohol molecular superstructure formation

Whiskers up to 1 cm in length were grown in polyvinyl alcohol (PVA) and urea solution. Raman and IR spectra discover an interaction between PVA and urea molecules. Optical and electronic microscopy data show that urea influences on PVA molecular superstructure formation. PVA whiskers prepared in urea solution can be used for organic semiconductors production which properties are determined by arrangement of polymer macromolecules.     

基于TiO_2纳米粒子薄膜的低阈值随机激光器的动力学研究

本文利用共轭聚合物(MEH-PPV)覆盖TiO_2纳米粒子薄膜制作随机激光器。随机TiO_2纳米粒子薄膜的激光辐射阈值比平面MEH-PPV薄膜的放大自发辐射阈值缩小了9倍。这是由于TiO_2纳米粒子诱导的多重散射造成的。进一步的飞秒荧光上转换实验表明,随机激光器中,光在增益介质里的停留时间有所增加,这直接证实了光在随机激光器结构中的多重散射引起光的传播路径增加。因此,这会促进更多的光发生辐射,从而降低随机激光器的阈值。     

Reversible light-induced capacitance switching of azobenzene ether/PMMA blends

Fully reversible light-induced switching of the capacitance with changes larger than 50% has been achieved by using photo-active thin polymer films. The films consist of PMMA polymer blended with high concentrations of branched azobenzene ether dye molecules. Polymer thin sheet capacitors can be easily produced by spin coating and drop casting in various thicknesses ranging from 100 nm to 8 μm, respectively. Reversible capacitance switching is induced by illumination with UV and visible light, respectively. The capacitance change is correlated to the trans to cis isomerization of the azobenzene ether molecules and the alignment of the molecular dipoles in the film. Switching times depend on chromophore concentration, film thickness and light intensity used. The influence of wavelength of the light, of the temperature as well as of an electrical field applied during illumination on the capacitance change is addressed.