Composites of hydrophilic polymers and organic nanocrystals enable enhanced robustness

We describe a new family of composite materials, polymer/organic nanocrystal (ONC) hybrids. These were prepared from soluble ONCs based on perylene diimides (PDI) and water‐soluble polymers (sodium alginate and polyvinyl alcohol). Polymer/ONC films were characterized by optical spectroscopy, electron microscopy, and tensile strength studies. The films show enhanced chemical and mechanical stability due to synergy between the constituents. The hybrid films are stable in both water and organic solvents, unlike the individual components. The ONCs we employed possess nonlinear optical activity (second harmonic generation, SHG); they showed improved photostability (stable SHG under laser light) in the hybrids. Tensile strength enhancement (as high as twofold in the film having just 2.4% ONCs by weight) was observed as revealed by mechanical measurements. Hybrids with aligned ONCs were also prepared using simple extrusion via syringe needle followed by gelation. Employing ONCs in polymeric hybrid materials enables facile fabrication in aqueous media, synergy, chemical, mechanical, and photostability as well as useful photofunction (SHG), introducing a versatile class of composite materials.     

苝二酰亚胺/聚噻吩复合膜的光电性能研究

在有机光电材料领域,光稳定性好、光谱吸收范围宽、光电转换效率高的材料是研究工作者不断追求的目标．近年来,导电聚合物研究的不断进展使得开发低成本太阳电池成为可能．共轭导电高分子材料由于在一定程度上同时具有聚合物的柔韧性和可加工性、以及无机半导体特性或金属导电性,因而具有巨大的潜在商业应用价值．     

Fabrication of micro-lens arrays built in photosensitive hybrid films by UV-cured imprinting technique

Photosensitive TiO₂-contained organic–inorganic hybrid films were prepared by combining a low-temperature sol–gel process with a spin-coating technique. Optical properties and photochemical activities of the as-prepared hybrid sol–gel films were characterized by prism coupling technique, thermal gravimetric analysis, UV–Visible spectroscopy, and Fourier transform infrared spectroscopy. Advantages for fabrication of micro-lens arrays based on the as-prepared photosensitive hybrid films were demonstrated by a direct-contact lithography technique and a reflow technique, followed by an UV-cured imprinting technique. Results indicate that the as-prepared photosensitive hybrid materials have great applicability for the fabrication of photonic components. Micro-sphere lens arrays and micro-ellipsoid lens arrays with the diameter from 20 to 100 μm and built in the as-prepared hybrid films were obtained. Morphological and surface profile properties of the as-fabricated micro-lens arrays were characterized by scanning electron microscopy and surface profiler, respectively. Results indicate that the fabrication process of the micro-lens arrays is a simple, cost-effective and mass production process, and the as-prepared photosensitive hybrid materials have great potential applications for the fabrication of the micro-optical elements.     

Nanostructured oligo(p-phenylene vinylene)/silicate hybrid films: one-step fabrication and energy transfer studies

Novel hybrid materials containing silicate and charged oligo(p-phenylene vinylene) (OPV) amphiphiles were fabricated in one step by spin casting using evaporation-induced self assembly. The conjugated segments were substituted with trimethylammonium bromide groups at both termini, and tetraethyl orthosilicate served as the silicate precursor. X-ray diffraction scans of the hybrid films revealed Bragg diffraction peaks with d-spacings of 2.76 and 1.37 nm, indicating the presence of order in the hybrid structure. Optical properties of the hybrid films were characterized by UV-vis absorption and fluorescence spectra, and molecular orientation was characterized by IR spectroscopy. A rhodamine B derivative containing a triethoxysilane group was covalently incorporated into the silicate network of the films during the sol-gel reaction. Relative to disordered polymer films with identical organic composition, the ordered hybrid films revealed significantly enhanced emission from rhodamine B and also fluorescence quenching from OPV segments. These results indicate that the ordered and nanostructured environment leads to highly efficient energy transfer among organic components in these hybrid films.     

基于粒子辅助水滴模板法制备仿生复眼结构的研究

将微粒“皮克林乳化效应”(Pickering emulsions)和水滴模板法(breath figure method)有机结合,探索通过建立粒子辅助的水滴模板法,实现纳米粒子在蜂窝状多孔膜内壁的自组装复合,构建微纳复合的多级仿生结构.并进一步利用聚二甲基硅氧烷(PDMS)复制转移技术,获得类似于复眼结构的多级微纳复合界面仿生结构.     

Synthesis and characterization of solution-processable core-cyanated perylene-3,4;9,10-bis(dicarboximide) derivatives

Core-cyanated perylene-3,4;9,10-bis(carboxyimide) derivatives N-functionalized with tethered anthracenes (PDI3A-CN(2), PDI4A-CN(2)) and the corresponding solution-processable cycloadduct precursors (PDI3A-CA-CN(2), PDI4A-CA-CN(2)) were synthesized and their optical, electrochemical, and thermal properties characterized. These derivatives exhibit HOMO-LUMO energy gaps of ～2.1-2.3 eV and first reduction potentials between -50 and -150 mV versus SCE. The PDI3A-CN(2) and PDI4A-CN(2) cycloadducts are soluble in common organic solvents (>50 mg/mL), and the corresponding spin-coated films are converted to PDI3A-CN(2) and PDI4A-CN(2) films upon thermal annealing.     

Cationic liposomes in double emulsions for controlled release

In this paper, we report a facile way to fabricate biomimetic high performance optical hybrid films with excellent antireflective and antifogging properties by one-step spin-coating the mixture of mesoporous SiO(2) particles and SiO(2) sol. The production process of the films is easy, low-cost, and time-efficient. Mesoporous SiO(2) particles containing surfactants disperse in SiO(2) sol stably without any chemical modification, which decrease the effective refractive index and increase the transmittance of the films. In addition, such films possess superhydrophilic properties and exhibit high performance antifogging properties. Due to the good film forming performance of SiO(2) sol, mesoporous SiO(2) particles are embedded in the films and impart the films high mechanical stability and durability. The surface morphology of the films can maintain well after repeated friction, and the performances of antireflective and antifogging also do not change as well.     

石墨烯的制备、表征及其在透明导电膜中的应用

近年来,石墨烯因其优异的电学和光学等特性,越来越受到人们的广泛关注。研究人员应用多种方法来合成石墨烯并且探讨其潜在的应用价值。本文首先简要介绍了石墨烯的结构及其基本的物理性质,并简单回顾了石墨烯的合成方法和表征手段。在此基础上,讨论了石墨烯/银复合薄膜在透明导电膜中的应用,并详细介绍了我们在该领域的研究成果。用化学气相沉积法（CVD）和多羟基法分别制备了双层石墨烯及银纳米线,成功合成了石墨烯/银复合薄膜,结果表明复合薄膜的方块电阻可降低至26 Ω·□-1,展示了其在光电器件上广泛的应用前景。     

One‐Step Electrodeposition to Layer‐by‐Layer Graphene–Conducting‐Polymer Hybrid Films

One‐step fabrication of graphene–polyaniline (graphene–PANI) hybrid film was facilely achieved by cyclic voltammetric electrolysis of a bath containing both graphene oxide (GO) and aniline, where graphene is obtained by electrochemical reduction of GO and PANI is simultaneously obtained by aniline electropolymerization. As there is no strong attraction between aniline and GO under the electrodeposition conditions, the independent depositions of PANI and reduced GO nanosheets at their greatly differed potentials led to alternate layered graphene–PANI films, with the topmost layer being PANI particles or graphene sheets just by changing the initial scan directions. The two kinds of graphene–PANI hybrid films present excellent but different electrical and electrochemical behaviors.     

壳聚糖-CdS复合膜制备及其对吡啶的传感特性

利用壳聚糖（CS）易于成膜的特点，模拟生物矿化，在有机物调制下通过异相成核生长制备了CS/CdS纳米颗粒复合膜.研究了成膜条件对膜的水热稳定性和发光性能的影响，以及CS/CdS纳米颗粒复合膜对水体中吡啶的响应特性.扫描电镜分析表明CS/CdS纳米颗粒复合膜均匀性好， CdS以物理掺杂方式均匀分布于CS薄膜中， CdS颗粒尺寸在70 nm左右.但薄膜荧光光谱位置和形状表明实际发光的CdS簇集体直径小于20 nm.由此推测电镜观察到的CdS颗粒可能是由许多CdS小颗粒聚集而成，小颗粒之间因有机物的存在而相互隔离. CS/CdS纳米颗粒复合膜的荧光发射对水体中吡啶的存在十分敏感，微量吡啶的存在会引起薄膜荧光发射急剧增强.除铜和碘离子外，水体系中其他常见离子对薄膜荧光发射没有显著影响，预期CS/CdS纳米颗粒复合薄膜有可能发展成为一种重要的水体系吡啶测定专用传感薄膜材料.     

Superhydrophobic thermoplastic polyurethane films with transparent/fluorescent performance

In this paper, we report a simple and versatile route for the fabrication of superhydrophobic thermoplastic polyurethane (TPU) films. The approach is based on octadecanamide (ODAA)-directed assembly of nanosilica/TPU/ODAA hybrid with a well-defined sheetlike microstructure. The superhydrophobic hybrid film shows a transparent property, and its water contact angle reaches as high as 163.5° without any further low surface energy treatment. In addition, the superhydrophobic TPU hybrid film with fluorescent properties is achieved by smartly introducing CdTe quantum dots, which will extend potential application of the film to optoelectronic areas. The resulting fluorescent surface produced in this system is stable and has a water contact angle of 172.3°. This assembly method to control surface structures represents an intriguing and valuable route to tune the surface properties of organic-inorganic hybrid films.     

Efficient light harvesting and energy transfer in organic-inorganic hybrid multichromophoric materials

Thin films of silica hybrid materials consisting of two to three covalently bound organic chromophores at different ratios were conveniently synthesized and fabricated. The photophysical properties of these materials have been studied. The fluorescence spectra reveal complete fluorescence resonance energy transfer (FRET) from donor to acceptor, and the light-harvesting ability of these hybrid materials increases with increasing the molar fraction of donor chromophore. In a three-chromophore system, the energy is transferred from 300 to 530 nm successfully. Time-resolved fluorescence experiments are employed to elucidate the average rates and efficiencies (84-97%) of energy transfer in these organic/inorganic hybrid systems. The hybrid materials have been shown to provide antenna effect to facilitate energy transfer and light harvesting.     

Highly Soluble Porphyrin (TPP)-Perylene Diimide (PDI) Dyad and Triad:Synthesis and Spectroscopic Studies

Novel porphyrin‐perylene diimide dyad (TPP‐PDI) and porphyrin‐perylene diimide‐porphyrin triad (TPP‐PDI‐TPP) were synthesized and characterized. Their structure and properties were studied by UV, FL, ¹H NMR, MS, elemental analysis, etc. The variation of fluorescence feature and UV spectra of TPP‐PDI‐TPP triad were investigated at different concentration of CF₃COOH in THF. The incorporation of CF₃COOH leads to the closure of the efficient charge transfer decay. After protonation of porphyrin units, the fluorescence intensity of TPP‐PDI‐TPP triad increased greatly. The fluorescence intensity of TPP‐PDI‐TPP triad restored after addition of triethylamine into the solution. Thus, TPP‐PDI‐TPP triad was a proton‐type fluorescence switch based on acid‐base control. Moreover, different from porphyrin‐perylene type molecular switches reported before, this TPP‐PDI‐TPP triad has wonderful solubility in organic solvents.     

Vapochromic behavior of polycarbonate films doped with a luminescent molecular rotor

We report on vapochromic films suitable for detecting volatile organic compounds (VOCs), based on polycarbonate (PC) doped with 4‐(triphenylamino)phthalonitrile (TPAP), a fluorescent molecular rotor sensitive to solvent polarity and viscosity. PC films of variable thickness (from 20 up to 80 µm) and containing small amounts of TPAP (0.05 wt%) were prepared and exposed to a saturated atmosphere of different VOCs. TPAP/PC films showed a gradual decrease and red‐shift of the emission during the exposure to solvents with high polarity index and favorable interaction with the polymer matrix such as THF, CHCl₃, and acetonitrile. In the case of the most interacting solvents (THF and CHCl₃), TPAP/PC films also showed a fluorescence increase at longer exposure times, as a consequence of an irreversible, solvent‐induced crystallization process of the polymeric matrix. The vapochromism of TPAP/PC films is rationalized on the basis of alterations of the rotor intramolecular motion upon solvent uptake by PC and polarity effects of the microenvironment. Interestingly, the fluorescence response of the TPAP/PC films shows a non‐trivial, tuneable dependence on film thickness during the second solvent‐exposure stage. The latter effect is attributed to a variable extent of the crystallization process occurring in the PC films. This observation promptly suggests, in turn, an effective procedure to modulate the spectroscopic response in such functionalized polymeric materials through the precise control of the film thickness. Copyright © 2015 John Wiley & Sons, Ltd.     

Polyoxometallates as inorganic templates for electrocatalytic network films of ultra-thin conducting polymers and platinum nanoparticles

We develop a concept of fabrication of the multilayer network films on electrodes by exploring the ability of a Keggin-type polyoxometallate, phosphododecamolybdate (PMo(12)O(40)(3-)), to form stable anionic monolayers (templates) on carbon and metals including platinum. By repeated alternate treatments in the solution of PMo(12)O(40)(3-) (or in the colloidal suspension of polyoxometallate-protected Pt-nanoparticles) and in the solution of monomer (e.g. anilinium) cations, the amount of the material can be increased systematically (layer-by-layer) to form stable three-dimensional assemblies on electrode (e.g. glassy carbon) surfaces. In the resulting hybrid (organic-inorganic) films, the layers of negatively charged polyoxometallate, or polyoxometallate-protected (stabilized) Pt-nanoparticles, are linked or electrostatically attracted by ultra-thin layers of such positively charged conducting polymers as polyaniline (PANI), polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene), PEDOT. Consequently, the attractive physicochemical properties of polymers and reactivity of polyoxometallate or noble metal particles are combined. The films are functionalized and show electrocatalytic properties towards reduction of nitrite, bromate, hydrogen peroxide or oxygen. They are of importance to the chemical and biochemical sensing as well as to the biochemical and medical applications.     

Photoinduced Electron and Energy Transfer in Dyads of Porphyrin Dimer and Perylene Tetracarboxylic Diimide

Two compounds containing a porphyrin dimer and a perylene tetracarboxylic diimide (PDI) linked by phenyl ( 1 ) or ethylene groups ( 2 ) are prepared. The photophysical properties of these two compounds are investigated by steady state electronic absorption and fluorescence spectra and lifetime measurements. The ground state absorption spectra reveal intense interactions between the porphyrin units within the porphyrin dimer, but no interactions between the porphyirn dimer and PDI. The fluorescence spectra suggest efficient energy transfer from PDI to porphyrin accompanied by less efficient electron transfer from porphyrin to PDI. The energy transfer is not affected by the dimeric structure of porphyrin or the linkage between the porphyrin dimer and PDI. However, the electron transfer from porphyrin to PDI is significantly affected by either the linkage between the donor and the acceptor or the polarity of the solvents. The dimeric structure of the porphyrin units in these compounds significantly promotes electron transfer in nonpolar, but not in polar solvents.     

Optimisation of Sol-Gel-Derived Silica Films for Optical Oxygen Sensing

Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function of dip-speed and water: precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen quenching in particular concentration ranges and environments.     

Self-organization of a sulfonamido-porphyrin in Langmuir monolayers and Langmuir-Blodgett films

Langmuir monolayers (LM) and Langmuir-Blodgett (LB) films of pure lipophilic meso-tetra(4-dodecylaminosulfophenyl)porphyrin (PC12) and mixed with the anionic surfactant sodium hexadecylsulfate (SHS) were studied. The molecular packing and structure of PC12 and PC12-4SHS with variable surface pressure were investigated by surface pressure-area measurements, steady-state absorption, fluorescence emission and anisotropy, as well as by fluorescence lifetime imaging microscopy (FLIM). At low surface pressure, the porphyrin molecules are organized with the rings tilted on the water surface whereas at high surface pressure the porphyrin rings achieve a more perpendicular arrangement. Using the FLIM images a gradual change of aggregates into large "islands" is observed. Different patterns are observed in the pure PC12 multilayer films (n = 3 and 5) with ordered patches superimposed which are not observed in the PC12-4SHS multilayer LB films.     

Difference in the Photophysical Properties of a Perylenetetracarboxylic Diimide Dimer and a Hexamer Linked by the Same Hexaphenylbenzene Group

A perylenetetracarboxylic diimide hexamer (6PDI) and a dimer (2PDI) linked with the same hexaphenylbenzene group were prepared, and the structures were fully characterized by ¹H NMR spectroscopy, mass spectrometry, and elemental analysis. Due to the similar molecular structure of these two compounds, similar interactions between/among the PDI subunits as well as similar photophysical properties are expected. However, the stationary UV/Vis absorption spectra reveal that the interactions among/between the PDI subunits in 6PDI are significantly stronger than those in 2PDI. This can be attributed to blocked rotation along the long axis of the PDI subunits in 6PDI due to steric hindrance of the two neighboring PDI subunits. The stronger interactions among the PDI subunits in 6PDI lead to long‐wavelength emission, which can be assigned to “excimer‐like” excited states. A similar conclusion can also be deduced from the fluorescence quantum yields and the fluorescence lifetimes. Electrochemical studies revealed that interactions between/among the PDI subunits in both 2PDI and 6PDI are still in the range of weak interactions. Ultrafast transient anisotropy decay dynamics revealed that excitation delocalization between the PDI subunits within 2PDI and 6PDI is quick and efficient. More interestingly, delocalization is faster in 6PDI than in 2PDI, probably because of the stronger interactions among the PDI subunits in the former.     

Assembly of Graphene Nanosheets and SiO2 Nanoparticles Towards Transparent,Antireflective, Conductive,and Superhydrophilic Multifunctional Hybrid Films

A new approach for the fabrication of transparent, antireflective, conductive and superhydrophilic multifunctional hybrid films through the layer‐by‐layer (LbL) assembly of reduced graphene oxide (RGO) nanosheets and SiO₂ nanoparticles is reported. The RGO nanosheets, SiO₂ nanoparticles and films were characterized by means of transmission electron microscopy, UV/Vis absorption spectrophotometry, Raman spectroscopy, atomic force microscopy, contact angle/interface system, and a four‐point probe. It was found that the graphene/SiO₂ hybrid films exhibited a significant increase in transmittance as compared with RGO films. The optical, electronic and wetting properties of hybrid films could be manipulated by rational design of the film structure and variation of the cycle number of the LbL assembly. The obtained transparent, conductive, and superhydrophilic graphene/SiO₂ hybrid films showed excellent antireflective, antistatic, and antifogging behaviors. The remarkable performance could be attributed to the combination of electrical conductivity of RGO nanosheets and superhydrophilic antireflective surface derived from SiO₂ nanoparticles.