近红外聚乙烯醇荧光高分子材料的制备及性能

以一种方酸菁染料、水溶性石墨烯和聚乙烯醇为原料,设计合成了在近红外区具有强荧光(660~665 nm)特性及良好的光热稳定性的方酸菁/聚乙烯醇二元和方酸菁/石墨烯/聚乙烯醇三元高分子材料;与在水中相比,方酸菁染料在聚乙烯醇中的最大紫外-可见吸收和荧光波长红移,荧光强度和光稳定性大幅提高;石墨烯的存在增强了材料的光稳定性。     

溶胶-凝胶法制备薄膜型TiO2光催化剂

用TiCl4作原料,通过溶胶-凝胶法在单晶硅基片上制备了TiO2纳米薄膜,并用XRD,AES,XPS以及紫外反射光谱等手段,对TiO2薄膜的结构进行了研究.结果发现,TiO2薄膜以锐钛矿型晶相存在.TiO2薄膜层与硅衬底间无明显的界面扩散反应.掺杂的Pd在还原前的薄膜中以氧化态存在,还原后则以高分散的金属态存在.掺杂的Pt在还原前后均以金属态存在,但还原后产生颗粒聚集.掺杂Pd的TiO2薄膜经还原后,其紫外吸收强度明显提高,主吸收峰发生红移.     

Controlled synthesis of highly dispersed TiO2 nanoparticles using SBA-15 as hard template

Highly dispersed TiO2 nanoparticles were successfully synthesized by a wet impregnation method using SBA-15 as hard template for confining the growth of TiO2 nanocrystals, and then calcined at 550 degrees C in muffle furnace for 2 h. The as-synthesized samples were characterized with Fourier transform infrared spectra (FTIR), Raman spectroscopy, diffuse reflectance UV-visible spectroscopy (UV-vis), powder X-ray diffraction (XRD), small-angle X-ray diffraction (SAXRD), nitrogen adsorption, transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was found that SBA-15 contained abundant silanol groups after removal of triblock copolymers by ethanol extraction and could easily adsorb a great number of titanium alkoxide via chemisorption. After subsequent hydrolysis of the anchored Ti complexes and calcination of the amorphous TiO2, anatase TiO2 nanocrystals with spherical shape and uniform particle diameter of about 6 nm were formed. A blue shift was observed in UV-vis absorption spectra due to the quantum size effect of TiO2 nanoparticles. Moreover, the as-prepared TiO2 nanoparticles showed a high PL intensity due to an increase in the recombination rate of photogenerated electrons and holes under UV light irradiation.     

Fe~(3+)掺杂的TiO_2纳米复合粒子的合成及表征

利用酸催化的溶胶-凝胶法合成了一系列不同Fe~(3+)掺杂量的TiO_2纳米复合 料子。用XRD,TEM,UV-vis等技术进行了表征。结果表明：在所研究的掺杂量范围 内(x_B = 0.0005 ～0.1000),未发现有铁氧化物的晶相生成;Fe~(3+)的掺杂可以 实现TiO_2由锐钛矿(anatase)结构向金红石(rutile)结构的低温转化,随着Fe~ (3+)掺杂量的增大,对光的吸收发生红移,吸收强度增大。掺杂适量的Fe~(3+)可 以使TiO_2纳米微粒的光催化活性得以提高。     

Enhanced photocatalytic activity of zeolite-encapsulated TiO2 clusters by complexation with organic additives and N-doping.

In the literature it was found that titanium oxide clusters of a few metal atoms encapsulated inside the micropores of zeolite Y exhibit large blue shifts in the Ti-O ligand-to-metal charge-transfer band as compared to non-encapsulated bulk titanium dioxide particles. This blue shift of the Ti-O absorption band is believed to have a negative effect on the photocatalytic activity of zeolite-encapsulated TiO2. We report here on circumventing this problem and increasing visible-light absorption by means of a red shift of the absorption band caused by addition of some organic molecular modifiers containing acidic OH groups that can strongly bind with titanol groups TiOH. In the studied series of zeolite-encapsulated TiO2 samples, the red shift of the optical spectrum follows the order: catechol > 4-aminobenzoic acid > benzoic acid. Also N-doping of zeolite-encapsulated TiO2 clusters by thermal treatment with urea leads to a red shift of the TiO2 absorption band that depends on the annealing and hydration conditions. By comparison to the degradation of phenol in aqueous solution, we have demonstrated that these changes in the absorption spectrum on addition of the organic modifier are also reflected in the photocatalytic activity of the samples; a greater increase in photocatalytic activity (about 30%) was observed for the additive catechol.     

Squaraine Rotaxane as a Reversible Optical Chloride Sensor

A mechanically interlocked squaraine rotaxane is comprised of a deep‐red fluorescent squaraine dye inside a tetralactam macrocycle. NMR studies show that Cl^? binding to the rotaxane induces macrocycle translocation away from the central squaraine station, a process that is completely reversed when the Cl^? is removed from the solution. Steady‐state fluorescence and excited‐state lifetime measurements show that this reversible machine‐like motion modulates several technically useful optical properties, including a three‐fold increase in deep‐red fluorescence emission that is observable to the naked eye. The excited states were characterized quantitatively by time‐correlated single photon counting, femtosecond transient absorption spectroscopy, and nanosecond laser flash photolysis. Cl^? binding to the rotaxane increases the squaraine excited singlet state lifetime from 1.5 to 3.1 ns, and decreases the excited triplet state lifetime from >200 to 44 μs. Apparently, the surrounding macrocycle quenches the excited singlet state of the encapsulated squaraine dye and stabilizes the excited triplet state. Prototype dipsticks were prepared by adsorbing the lipophilic rotaxane onto the ends of narrow, C18‐coated, reverse‐phase silica gel plates. The fluorescence intensity of a dipstick increased eighteen‐fold upon dipping in an aqueous solution of tetrabutylammonium chloride (300 mM ) and was subsequently reversed by washing with pure water. It is possible to develop the dipsticks for colorimetric determination of Cl^? levels by the naked eye. After dipping into aqueous tetrabutylammonium chloride, a dipstick’s color slowly fades at a rate that depends on the amount of Cl^? in the aqueous solution. The fading process is due primarily to hydrolytic bleaching of the squaraine chromophore within the rotaxane. That is, association of Cl^? to immobilized rotaxane induces macrocycle translocation and exposure of the electrophilic C₄O₂ core of the squaraine station, which is in turn attacked by the ambient moisture to produce a bleached product.     

PHOTODESTRUCTION OF BACTERIORHODOPSIN

Abstract— Suspensions of purple membrane fragments showed obvious signs of degradation after illumination with intense pulses of light from 10 ns frequency doubled Nd: YAG laser at 532 nm with intensity densities in excess of 1 MW/cm². Using controlled illumination, a small fraction of the bacteriorhodopsin protein molecules were randomly destroyed in samples with a low salt concentration (12.5 m M ) and pH = 7.9. Calculations using information from the changes in the optical absorbance spectrum and transient changes in the optical absorbance spectrum during the photocycle support a model where one protein molecule of the bacteriorhodopsin trimer is photodestroyed, the other two protein molecules switch to a blue state . In the blue state , the protein molecules have a red shifted absorption, with a peak near 600 nm. The blue state molecules show transient absorption changes at 656 nm that are similar to the native bacteriorhodopsin, except the O state is missing or altered. Additionally, the changes in curvature of the purple membrane fragments that occur during the photocycle of intact protein molecules are severely depressed. The addition of salts to the photodestroyed suspension can change the blue state molecules back to a state with an absorption maximum at 568 nm. The salt ions probably shield the other members of the trimer from the photodestroyed protein. In these reconstituted samples, the O state is observed at 656 nm; however, the membrane bending is not observed.     

Standing wave enhancement of red absorbance and photocurrent in dye-sensitized titanium dioxide photoelectrodes coupled to photonic crystals

The light harvesting efficiency of dye-sensitized photoelectrodes was enhanced by coupling a TiO(2) photonic crystal layer to a conventional film of TiO(2) nanoparticles. In addition to acting as a dielectric mirror, the inverse opal photonic crystal caused a significant change in dye absorbance which depended on the position of the stop band. Absorbance was suppressed at wavelengths shorter than the stop band maximum and was enhanced at longer wavelengths. This effect arises from the slow group velocity of light in the vicinity of the stop band, and the consequent localization of light intensity in the voids (to the blue) or in the dye-sensitized TiO(2) (to the red) portions of the photonic crystal. By coupling a photonic crystal to a film of TiO(2) nanoparticles, the short circuit photocurrent efficiency across the visible spectrum (400-750 nm) could be increased by about 26%, relative to an ordinary dye-sensitized nanocrystalline TiO(2) photoelectrode.     

卟啉/TiO2界面的相互作用研究

采用吸收光谱、荧光光谱和瞬态光伏技术研究了卟啉/TiO2体系的吸收光特性、荧光特性和光伏特性, 并研究了卟啉和TiO2之间的界面相互作用. 研究结果表明, 卟啉环在与钬原子结合前后与TiO2之间的作用不同, TiO2的粒径也影响界面的相互作用. 卟啉与粒径为10 nm的TiO2作用后, 能级发生了简并, 同时带隙发生了红移. 卟啉与粒径为56 nm的TiO2相互作用后只有特征吸收峰发生红移, 带隙和峰的数量几乎未发生变化. 这说明在粒径为10 nm的TiO2与卟啉的大π键之间出现了离域的相互作用, 这也被荧光光谱和瞬态光伏曲线所证实.     

水热法合成多孔Ag_2S敏化二氧化钛催化剂及其可见光催化活性(英文)

Porous Ag2S sensitized TiO2 catalysts were synthesized by the hydrothermal process.The crystallization and porous structure of the Ag2S/TiO2 composite photocatalysts were investigated by X-ray diffraction,scanning electron microscopy with energy dispersive X-ray analysis,UV-Vis diffuse reflectance spectroscopy,and N2 adsorption.The Ag2S/TiO2 composites were mainly composed of anatase TiO2 and acanthite Ag2S.The absorption edge wavelengths of TiO2 and the Ag2S/TiO2 composite prepared with 3 mmol Na2S.5H2O were 400 and 800 nm,respectively,that is,the absorption edge of the composite had a pronounced red shift.The photocatalytic activity under visible light was investigated by the degradation of methylene blue with a UV-Vis spectrophotometer.The photocatalytic activities under visible light of the Ag2S/TiO2 photocatalysts were much higher than that of TiO2.     

Halide coordination to zinc porphyrin sensitizers anchored to nanocrystalline TiO2

The coordination of halide ions to 5-(3,5-dicarboxyphenyl)-10,15,20-tri- p-tolylporphinatozinc(II) anchored to mesoporous nanocrystalline (anatase) TiO 2 thin films (TiO 2/ZnP) immersed in propylene carbonate was quantified. The addition of tetrabutylammonium halide salts to the external propylene carbonate electrolyte resulted in a red shift in the absorption spectrum with the maintenance of five isosbestic points. The absorption spectra were within experimental error the same for ZnP and ZnP-X (-) compared to TiO 2/ZnP and TiO 2/ZnP-X (-): A SoretZnP = 427 nm (epsilon = 574 000 M (-1) cm (-1)), A SoretZnP-Cl (-) = 435 nm (epsilon = 905 000 +/- 12 000 M (-1) cm (-1)), A SoretZnP-Br (-) = 436 nm (epsilon = 776 000 +/- 30 000 M (-1) cm (-1)), and A SoretZnP-I (-) = 437 nm (epsilon = 620 000 +/- 56 000 M (-1) cm (-1)). Titration studies with the halides revealed sharp isosbestic points consistent with formation of a 1:1 halide/porphyrin adduct. Equilibrium constants for ZnP were found to be 1670 M (-1) for Cl (-), 96 M (-1) for Br (-), and 5.5 M (-1) for I (-), and the corresponding values for TiO 2/ZnP were significantly smaller, 780 M (-1), 70 M (-1) and 3.4 M (-1). A quasi-reversible wave was observed by cyclic voltammetry of TiO 2/ZnP, E 1/2(ZnP (+/0)) = +790 mV vs Ag/AgCl, that was shifted 160 mV after addition of excess chloride, E 1/2(ZnP-Cl (0/-)) = +630 mV. In regenerative solar cells with quinone/hydroquinone redox mediators, TiO 2/ZnP and TiO 2/ZnP-X (-), where X is Cl, Br, or I, were found to convert light into electrical power. The photocurrent action spectrum demonstrated that energy conversion was initiated by light absorption of ZnP and/or the halide adduct.     

Polymerization of branched thiophene monomers and optoelectronic properties of materials

Bithiophene monomers ( 5HBTh and 5HBThO ) were prepared by the Suzuki coupling reaction of 3‐thienylboronic acid with 2‐bromo‐5‐hexylthiophene and 2‐bromo‐5‐hexylthiophene‐1,1‐dioxide. The oxidation polymerization mediated by vanadium catalyst gave poly(5HBTh) and oligo(5HBThO) . 5HBThO bearing thiophene‐1,1‐dioxide had an absorption maximum at longer wavelength region than 5HBTh due to the intramolecular charge transfer interaction, while peak maxima blue shifted and their difference became small after the polymerization. Terthiophene monomers ( 5″HTTh , 3,5″DHTTh , and 4,5″DHTTh ) were subsequently prepared by the mono‐bromination of 5HBTh followed by the Suzuki coupling reaction with boronic acid derivatives. The vanadium‐catalyzed oxidation polymerization of 5″HTTh and 4,5″DHTTh afforded soluble polymers and the absorption maximum wavelengths red shifted after the polymerization in contrast to bithiophene monomers and 3,5″DHTTh . The absorption and emission spectra of poly(5″DHTTh) red shifted when compared with those of poly(4,5″DHTTh) . Thus the presence and position of n‐hexyl chain influenced the monomer polymerizability and optoelectronic properties of branched polythiophenes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3034–3044, 2009     

A Spectroscopic Study of the Effects of Various Solvents and Sol-Gel Hosts on the Chemical and Photochemical Properties of Thionin and Nile Blue A

Tetraethyl orthosilicate (TEOS)-based gels were doped with two optically active organic indicators, thionin and nile blue A. Before trapping in a sol-gel host, thionin and nile blue A were both evaluated for solvent and protonation effects on their spectral properties. Only extreme pH values provided by HCl, NaOH, and NH₄OH produced new absorption and/or fluorescence bands. Introduction of nile blue A into alkaline environments (0.1N NaOH, NH₄OH) results in the appearance of a broad absorption band centered near 520 nm whereas highly acidic environments (1N HCl) show a reduction of the 635 nm absorption peak accompanied by an absorption band located near 460 nm. A marked decrease is observed in the optical density of thionin in 1N HCl solution which results in a reduction in the fluorescence intensity. The absorption and fluorescence spectra also reveal a decrease in a pH 11 solution of NH₄OH as compared to neutral conditions. Both dyes formed dimers when the sol-gel host, initially synthesized with TEOS, was organically modified with methyltrimethoxysilane (MTMS). However, thionin dimers were present in all silica-based sol-gel compositions, as evidenced by the absorption and fluorescence spectra. Substitution of MTMS for some of the TEOS in the gel matrix resulted in blue shifts in the absorption and fluorescence spectra of nile blue A. The absorption peak shifted 50 nm to 596 nm whereas the fluorescence shifted around 40 nm to 635 nm. These blue shifts resulted from the reduced polarity of the silica-based xerogel. Thionin also exhibited shifts in its absorption and fluorescence spectra with organic modification by MTMS. The absorption shifted approximately 3 nm to 595 nm while the fluorescence maximum decreased 7 nm to 630 nm. The blue shifts in the spectra of thionin with additions of MTMS were attributed to surface sites that altered the molecular structure of the adsorbed thionin molecules.     

Rational Design of Fluorescent Bioimaging Probes by Controlling the Aggregation Behavior of Squaraines: A Special Effect of Ionic Liquid Pendants

We herein present an effective strategy to create water‐soluble fluorescent bioimaging dyes by introducing the imidazolium‐based ionic liquid (IL) pendants into a fluorescent skeleton. A new type of water‐soluble imidazolium‐anchored squaraine dye was synthesized accordingly. The relationship between the aggregate of squaraines and their fluorescent cell imaging application was elucidated in detail. Firstly, the aggregation behavior of squaraines in water solutions could be suppressed by varying the alkyl chain attached to the imidazolium unit. Secondly, the capability of cellular uptake and staining of dyes was also dramatically enhanced upon increasing the length of the paraffinic chain. These squaraine dyes displayed an excellent photostability that could permit real‐time fluorescence bioimaging experiments to be monitored over a long time period with constant sample irradiation. Additionally, we designed for the first time an Fe^II‐ion probe on the basis of an attack of the hydroxyl radical to the four‐membered ring of squaraine. The results demonstrated that the imidazolium‐anchored squaraines could perform “naked‐eye” detection of the Fe²⁺ ion over a wide range of other interfering metals in aqueous media. More surprisingly, this process showed a fluorescence “turn‐off” and “‐on” response through the regeneration of squaraines in cells.     

活性炭负载Cu离子掺杂纳米TiO2颗粒的制备及光催化性能

采用溶胶-凝胶法在活性炭(AC)表面负载掺杂Cu离子的TiO2纳米颗粒, 制备负载型掺杂Cu2+-TiO2/AC复合光催化剂, 采用XRD, ESR, FS, UV-Vis和BET等手段对其进行了表征, 通过罗丹明B的光催化降解试验, 分析活性炭载体的比表面积和Cu离子掺杂量对负载型掺杂催化剂光催化活性的影响. 结果表明, Cu以+2价存在, Ti以少量的+3价存在; TiO2纳米颗粒具有量子尺寸效应, 吸光阈值显著蓝移, 并使光谱相应范围向可见光区拓展; 另外, 适量Cu离子的掺杂降低了负载型TiO2/AC的荧光强度. 负载和高温处理没有改变活性炭载体的微观结构. 以AC3为载体和质量分数为3%的Cu离子掺杂所制备的3%Cu2+-TiO2/AC3催化剂的活性最高, 并且该催化剂便于回收, 在重复使用中也表现出很高的光催化活性.     

大豆蛋白改性TiO_2的制备及其可见光催化性能

采用溶胶-凝胶法制备了系列大豆蛋白改性TiO_2复合催化剂.通过元素分析、粒度分析、X射线衍射(XRD)、场发射扫描电镜(FESEM)、紫外-可见漫反射光谱(UV-Vis)、电化学等方法对所制备的样品进行了表征,以亚甲基蓝为目标降解物,研究了大豆蛋白改性TiO_2的可见光催化性能.结果表明,大豆蛋白改性可以一步实现C、N、H多种非金属元素共掺杂;相比纯TiO_2,改性后复合催化剂的比表面积增大;所有样品均为锐钛矿相;煅烧温度为400℃时,复合催化剂的可见光吸收发生明显红移,其禁带宽度较纯TiO_2窄化了0.32 e V;大豆蛋白改性后,复合材料的光电流密度增大;在可见光照射下,光催化反应2 h时,大豆蛋白改性TiO_2的亚甲基蓝降解效率最高可达79.4%.     

可溶性镍酞菁的光谱特性研究

利用UV-Vis吸收光谱、荧光光谱及半经验ZINDO/S方法,研究了4种可溶性镍酞菁(FPcNi、MePcNi、iBPcNi、iPPcNi)的电子吸收光谱和荧光光谱.研究结果表明:随着取代基的供电子能力增加,酞菁的最大吸收波长(λ_max)和发射波长(λ_em)发生红移,摩尔消光系数变小;随着溶液浓度增大,酞菁聚集体浓度增大,λ_max发生蓝移,但浓度对λ_em影响较小,同时荧光相对强度随浓度增大,出现最大值;随着溶剂配合能力的增加,λ_max、λ_em都发生红移.     

TiO2-双亲共聚物复合纳米粒子的合成与紫外光敏特性

用偶联剂乙烯基三乙氧基硅烷改性纳米粒子TiO₂, 应用超声技术将TiO₂ 纳米粒子分散在甲醇介质中, 然后用苯乙烯(ST)原位聚合包封, 再用丙烯酰胺或乙烯基吡咯烷酮(VP)共聚, 两步原位分散聚合得到了有机聚合物为壳、TiO₂为核的有机/无机复合粒子. 用红外光谱、紫外-可见光谱、透射电子显微镜等检测手段进行表征. 结果显示: 由于双亲共聚物对TiO₂纳米粒子的敏化作用, 紫外-可见光谱图上两种纳米复合粒子的最大吸收峰均有明显红移, 并且吸收光谱的范围扩大了, 其中尤以TiO₂/(PST-co-PVP)为甚. 意味着光敏化活性的提高, 特别是在可见光谱的范围内. 这种情形对宽带隙半导体材料如TiO₂纳米粒子的光催化特性是有利的, 表明这类材料的应用空间得到了拓展.     

Isomerism in jet-cooled 1-cyanonaphthalene complexes

The effect of complexation on the first electronic transition of 1-cyanonaphthalene has been studied for complexes with aprotic polar solvents (acetonitrile, diethylether) or olefins (2-methyl-2-butene, 2,3-dimethyl-2-butene). In both cases, isomerism has been evidenced. With polar solvents, two strong absorption bands appear in the 0 ₀ ⁰ region, one being shifted to the red and the other one to the blue side of the bare cyanonaphthalene transition. These two bands have been assigned to two isomeric forms involving specific interactions between the solvent and the cyanonaphthalene molecule. These isomers have been shown to interconvert at higher vibronic energies. With the 2,3-dimethyl-2-butene a broad absorption band leading to a red shifted fluorescence has been observed and assigned to an exciplex. With the 2-methyl-2-butene, one observes the superposition of narrow and broad bands in the excitation spectrum. These two systems have been assigned to two isomeric forms, one of them crossing to an exciplex in the excited state. At higher vibronic energy, emission from the two conformers is observed.     

Synthesis and characterization of Nano titania particles embedded in mesoporous silica with both high photocatalytic activity and adsorption capability

TiO(2)-xSiO(2) composites with a high specific surface area (up to 645 m(2)/g), large pore volume, and narrow distribution with average pore sizes ranging from 15 to 20 A have been synthesized by the sol-gel method. The results of characterization by XRD, BET, TEM, FTIR, and DRUV reveal that these TiO(2)-xSiO(2) composites exhibit a core/shell structure of a nano titania/Ti-O-Si species modified titania embedded in mesoporous silica. As compared to pure anatase, the embedding of nano titania particles into the mesoporous silica matrix results in a substantial blue shift of absorption edge from 3.2 to 3.54 eV and higher UV absorption intensity, which are attributed to the formation of the Ti-O-Si species modified titania in the interface between titania and silica. The as-synthesized TiO(2)-xSiO(2) composites exhibit both much higher absorption capability of organic pollutants and better photocatalytic activity for the photooxidation of benzene than pure titania. The better photocatalytic activity of as-synthesized TiO(2)-xSiO(2) composites than pure titania is attributed to their high surface area, higher UV absorption intensity, and easy diffusion of absorbed pollutants on the absorption sites to photogenerated oxidizing radicals on the photoactive sites.