Multifunctional Langmuir-Blodgett film of an Amphiphilic Benziminazole Styryl Dye

An amphiphilic benziminazole styryl dye, 2 (4 dihexadecylaminostyryl)benziminazolium TCNQ -(DBTCNQ), was synthesized and successfully transferred onto the substrates by Langmuir Blodgett(LB) technique. H aggregates were formed on the substrates. Its monolayer second order susceptibility[ χ (2) zzz = 109 p/mV) was determined with a polarized laser beam(Nd∶YAG, λ =1.064 μm). The photoelectrochemistry of the dye LB monolayer films was investigated in a traditional three electrode cell. The quantum efficiency of photoelectric conversion is 1.08% under favorable conditions [-200 mV, 0.5 mg/mL methylviologen diiodide(MV 2+ ) in 0.5 mol/L KCl electrolyte solution]. The experimental data indicate that the LB film exhibits multifunctional properties.

Enhancement of modulation depth of an all-optical switch using an azo dye-ethyl red film

The polymethyl methacrylate （PMMA） film doped with an azo dye ethyl-red （ER） film is employed to demonstrate the properties of an all-optical switch by its photoinduced dichroism and birefringence. We show how to enhance remarkably the modulation depth of all-optical switches almost to 100% by using two linear polarization beams： one beam is inclined at 45° with respect to the probing beam and serves as a pumping beam, and the other beam is perpendicular to the probing beam and used as an erasing beam. Furthermore, a maximum-to-minimum output intensity ratio of 2000：1 is achieved in experiment, which is very useful and important for optical storages and image displays.

Synthesis of Azoxy Dyes and Their Copper Complexes and Their Application on Polyvinyl Alcohol (PVA) Polarizing Film

Azoxy dyes and their copper complexes with maximum dichroism in the spectrum range from 550nm to 700nm were synthesized and used to prepare polyvinyl alcohol (PVA) polarizing films. These films showed excellent polarizing ability. In addition, a neutral gray polarizing film was prepared by mixing synthesized dichromatic dyes with other dyes. The obtained polarizable film for gray shade was little pervious to light over the visible radiation wavelength region, ranging from 400nm to 700nm at cross state, and excellent in the polarizing activities and stable to moisture and heat.

Synthesis and Investigation of Phenol Red Dye Doped Polymer Films

The optical properties of the pure polymer film and polymer films doped with Phenol Red dye at different concentrations were investigated. The films were prepared using the casting technique. Poly (methyl-methacrylate) (PMMA) polymer was doped with the Phenol Red dye dissolved in a mixture of chloroform and little quantity of methanol, used as suitable solvent for both the dye and the polymer. The spectral absorption measurements of these films were carried out at different dye concentrations using UV-Vis double-beam spectrophotometer in the wavelength range 300 - 800 nm. The optical parameters of the prepared Phenol Red dye doped polymer films, absorption coefficient (α), extinction coefficient (κ), refractive index (n), optical and electrical conductivities (σopt and σelect), and optical energy band gap (Eg), were determined. The results showed that the Phenol Red dye doped polymer film is a good candidate for photonic applications such as, solar cells, optical sensors, and other photonic devices.

A new inorganic azo dye and its thin film:MoO_4N_4H_6

Thin films of hydrazine molybdenum （MoO4N4H6）, a new inorganic azo dye, were synthesized and deposited on a commercial glass substrate using the chemical bath deposition technique. Subsequently, the optical transmission, reflectivity, absorption, refractive index, and dielectric constant of hydrazine molybdenum were investigated using an ultraviolet-visible spectrophotometer. In addition, the film structure was analyzed by mid-infrared spectroscopy. The spectra of the films were found to be in line with those in the literature. The surface properties of all films were examined using a computer-controlled digital scanning electron microscope with a secondary electron detector. The areas of application and the technological advantages of this material were also considered.

Nanoscaled ZnO films used as enhanced substrates for fluorescence detection of dyes

The ability of nanoscaled ZnO films to enhance fluorescence was studied. We found that the fluorescence intensities of Cy5, rhodamine 6G, and fiuorescein can be enhanced about 10-fold on nanoscaled ZnO films as compared to that on glass substrates. The lifetimes of all samples were measured, and no obvious change in lifetime was observed for dyes on different substrates. The mechanism for the nanoscaled ZnO film enhanced fluorescence appears to be different from that for the metal-fluorophore systems.

Enhancement of Photocurrent Generation of a Novel Stilbazolium Dye Dimer in LB Monolayer Films

A novel dye dimer, bis-{[1-(N-hexadecyl-4-pyridinium)-2-(4-N, N-dimethylamino- phenyl)] ethenyl}methane diiodide (C16BP) was synthesized, and the photoelectrochemistry of the dye Langmuir-Blodgett monolayer modified ITO electrode was investigated. For comparison, the photoelectrochemistry of the monomer (E)-N-hexadecyl-4-[2-(4-N, N-dimethylaminophenyl) ethenyl] pyridinium iodide (C16P) was also measured. The results show that the photocurrent generation property of the dimer is enhanced. The photocurrent generation quantum yield is 0.38% for C16BP, while that for C16P is 0.23%.

Fabrication and Fluorescence Study of Sensitizing Dye/TiO_2 Films

Fluorescence spectra of the sensitizing dye/ TiO2 bilayer films were studied. Charge-transfer complexes were formed in the above bilayer.

Influences of annealing temperature on properties of Fe^2+:ZnSe thin films deposited by electron beam evaporation and their applications to Q-switched fiber laser

Fe^2+:ZnSe thin films are prepared on sapphire substrate at room temperature by electron beam evaporation and then annealed in vacuum(about 1×10^-4 Pa)at different temperatures.The influences of thermal annealing on the structural and optical properties of these films such as grain size and optical transmittance are investigated.The x-ray diffraction patterns show that the Fe2+:ZnSe thin film is preferred to be oriented along the(111)plane at different annealing temperatures.After the film is annealed,the full-width-at-half-maximum(FWHM)of the x-ray diffraction peak profile(111)of the film decreases and its crystal quality is improved.Scanning electron microscope images show that the films are more dense after being annealed.Finally,the sample is used as a saturable absorber in ZBLAN fiber laser.The annealed Fe^2+:ZnSe thin films can be used to realize stable Q-switching modulation on ZBLAN fiber laser.The results demonstrate that the Fe2+:ZnSe thin film is a promising material for generating the high-power pulses of mid-infrared Q-switched fiber lasers.

Fluorescent-Dye Doped Thin-Film Sensors for the Detection of Alcohol Vapors

Fluorescence sensors based on a trifluoroacetophone compound doped in ethyl cellulose (EC) thin films have been developed for the detection of methanol, ethanol, and 2-propanol (isopropanol, PriOH) vapors. Thin-film sensors are prepared with 4-dibutylamino-4’-(trifluoroacetyl)stilbene (Chromoionophore IX or CIX) as the fluorescent dye and its solution in EC was spin-coated onto glass slides. The luminescence intensity of the dye (555 nm) is quenched when exposed to alcohol vapor. Tested in the range of ca. 0 - 1.5?× 104 ppm (wt) for MeOH and EtOH, and ca. 0 - 2.3 × 104 ppm for PriOH, the sensors gave detection limits of 9, 13, 21 ppm and quantification limits of 32, 43, and 70 ppm, respectively. To enhance the sensitivity of the sensors, TiO2 particles have been added to the films to induce Mie scattering, which increases the incident light interaction with the sensing films. The sensors in this work have been designed to work in a multianalyte platform for the simultaneous detection of multiple gas analytes.

Preparation of Latex Film with Macropores and Their Applications in Pigment Dyeing

Aiming at improving the permeability of the pigment dyed fabrics,two kinds of hydrophilic polymers(polyvinyl pyrrolidone(PVP),and polyethylene glycol(PEG)were fed into the styrene-butyl acrylate(St-BuA)copolymer latex binder respectively to prepare films with macropores.The effects of the post-added polymers on the latex film formation process and film structures were studied and the performance of the dyed fabrics was evaluated.It was found that the drying process could still be divided into three stages even after the addition of PVP and PEG.And the water evaporation rate during the first and last stage remained the same as usual.However,after the addition of PVP,the onset of the second stage was delayed to high volume fraction,and PVP formed into spherical dispersion phase with 300 nm in diameter.It provided a great deal of interface between the latex polymer and the PVP phase,which led to an increase in the water evaporation rate during the second stage.A different case was found after the feeding of PEG.Firstly,the first stage ended at low volume fraction and a decreased evaporation rate was observed in the second stage.Secondly,the PEG dispersion appeared as finger-like structure in the transmission electron microscopy(TEM)images with 9μm in length.After rinsing,pores were found only in the films formerly containing PVP or PEG,and the shapes and the sizes were closely correlated with the initial morphologies of the PVP or PEG domains.However,the shade of color,the abrasion fastness,and the permeability of the dyed fabric were independent of the type of the post-added hydrophilic polymer.

CHARACTERIZATION AND LUMINESCENCE PROPERTIES OF THE DYE-DOPED POLYMER LANGMUIR-BLODGETT FILMS

1,1,4,4-Tetraphenyl-1,3-butadiene (TPB) was successfully introduced into the polymer multilayer films by means of Langmuir-Blodgett (LB) technique. Results of UV-VIS spectra and X-ray diffraction showed that the uniform films had a layer structure similar to the superlattice of organic multiple quantum wells. The electroluminescence (EL) devices fabricated from the doped polymer LB films emitted blue light. Compared with the casting films, the photoluminescence (PL) and EL spectra showed that the exciton energy shifts to higher and the half-width of the emission peak becomes narrower due to exciton confinement effect.

Light scattering of nanocrystalline TiO_2 film used in dye-sensitized solar cells

This paper studies the light scattering and adsorption of nanocrystalline TiO2 porous films used in dye-sensitized solar cells composed of anatase and/or rutile particles by using an optical four-flux radiative transfer model. These light properties are difficult to measure directly on the functioning solar cells and they can not be calculated easily from the first-principle computational or quantitative theoretical evaluations. These simulation results indicate that the light scattering of 1 25 nm TiO2 particles is negligible, but it is effective in the range of 80 and 180 nm. A suitable mixture of small particles （10 nm radius）, which are resulted in a large effective surface, and of larger particles （150 nm radius）, which are effective light scatterers, have the potential to enhance solar absorption significantly. The futile crystals have a larger refractive index and thus the light harvest of the mixtures of such larger rutile and relatively small anatase particles is improved in comparison with that of pure anatase films. The light absorption of the 10μm double-layered films is also examined. A maximal light absorption of double-layered film is gotten when the thickness of the first layer of 10 urn-sized anatase particles is comparable to that of the second larger rutile layer.

Sensitizing Mechanism and Adsorption Properties of Dye-sensitized TiO_2 Thin Films

The dye-sensitized TiO2 complex films were prepared by the dye coat onto TiO2 surfaces, and the sensitizing mechanism and adsorption properties of the dye-sensitized TiO2 complex films were investigated. The influence of the application conditions of dye adsorbed on TiO2 films on the amount of dye adsorption was discussed. Experimental results show that the concentration, the temperature of dye solutions and the dipping time of TiO2 films in the dye solutions have a significant influence on the amount of dye adsorption. Cell test indicates that the conversion efficiency of light to electricity increases with the amount of dye adsorption.

Dye-sensitized solid-state solar cells fabricated by screen-printed TiO_2 thin film with addition of polystyrene balls

The screen-printed nanoporous TiO2 thin film was employed to fabricate dye-sensitized solid-state solar cells using CuI as hole-transport materials. The solar cell based on nanoporous TiO2 thin film with large pores formed by the addition of polystyrene balls with diameter of 200 nm to the TiO2 paste exhibits photovoltaic performance enhancement, which is attributed to the good contact of CuI with surface of dye-sensitized thin film due to easy penetration of CuI in the film with large pores.

Applicative Study(Part I):The Excellent Conditions to Remove in Batch Direct Textile Dyes(Direct Red,Direct Blue and Direct Yellow)from Aqueous Solutions by Adsorption Processes on Low-Cost Chitosan Films under Different Conditions

In recent years the development of chitosan (CH) based materials as useful adsorbent polymeric matrices is an expanding field in the area of adsorption science. Even though CH has been successfully used for dye removal from aqueous solutions due to its low cost, no considerations have been made about, for example, the effect of changing the pH of chitosan hydrogelor about the dehydrating effect of Ethanol (EtOH) treatment of chitosan film on the dyes removal from water. Consequently in our laboratory we carried out a study focusing the attention, mainly, on the potential use of CH films under different conditions, such as reducing the intrinsic pH, increasing the hydrophobic character by means of ethanol treatment and neutralization of CH films to improve their absorption power. Textile anionic dyes named Direct Red 83:1, Direct Yellow 86 and Direct Blue 78 have been studied with the aim of reducing the contact time of CH film in waste water improving the bleaching efficiency. Neutralized acid CH film and longtime dehydrated one result to be the better films in dye removal from water. Also the reduction of the CH solution acidity during the film preparation determines the decreasing of the contact time improving the results. The effect of initial dye concentration has been examined and the amount of dye adsorption in function of time t, qt (mg/cm2), for each analyzed film has been evaluated comparing the long term effect with the decoloration rate. A linear form of pseudo-first-order Lagergren model has been used and described. The best condition for removing all examined dyes from various dye solutions appears to be the dehydration of a novel projected CH film obtained by means of the film immersion in EtOH for 4 days. Also CH films prepared by well-known literature procedure and neutralized with NaOH treatment appear having an excellent behavior, however the film treatment requires a large quantity of water and time.

Sensitizing Mechanism and Adsorption Properties of Dye-sensitized TiO2 Thin Films

The dye-sensitized TiO2 complex films were prepared by the dye coat onto TiO2 surfaces, and the sensitizing mechanism and adsorption properties of the dye-sensitized TiO2 complex films were investigated. The influence of the application conditions of dye adsorbed on TiO2 films on the amount of dye adsorption was discussed. Experimental results show that the concentration, the temperature of dye solutions and the dipping time of TiO2 films in the dye solutions have a significant influence on the amount of dye adsorption. Cell test indicates that the conversion efficiency of light to electricity increases with the amount of dye adsorption.

Photoelectrocatalytic activity of immobilized Yb doped WO3 photocatalyst for degradation of methyl orange dye

Pure WOand Yb:WOthin films have been synthesized by spray pyrolysis technique. Effect of Yb doping concentration on photoelectrochemical, structural, morphological and optical properties of thin films are studied. X-ray diffraction analysis shows that all thin films are polycrystalline nature and exhibit monoclinic crystal structure. The 3 at% Yb:WOfilm shows superior photoelectrochemical（PEC） performance than that of pure WOfilm and it shows maximum photocurrent density（Iph= 1090 μA/cm） having onset potentials around +0.3 V/SCE in 0.01 M HClO. The photoelectrocatalytic process is more effective than that of the photocatalytic process for degradation of methyl orange（MO） dye. Yb doping in WOphotocatalyst is greatly effective to degrade MO dye. The enhancement in photoelectrocatalytic activity is mainly due to the suppressing the recombination rate of photogenerated electron-hole pairs. The mineralization of MO dye in aqueous solution is studied by measuring chemical oxygen demand（COD） values.

Anisotropy in Third-Order Nonlinear Optical Susceptibility of a Squarylium Dye in a Nematic Liquid Crystal

A squarylium dye is dissolved in 4-cyano-4＇-pentylbiphenyl （SCB） and oriented by sandwiching mixtures between two pieces of rubbed glass plates. The optical absorption spectra of the oriented squarylium dye-5CB layers exhibit high anisotropy. The third-order nonlinear optical responses and susceptibilities X^（3）e of squarylium dye in 5CB are measured with light polarizations parallel and perpendicular to the orientational direction by the resonant femtosecond degenerate four-wave mixing （DFWM） technique. Temporal profiles of the DFWM signal of the oriented squarylium dye-5CB layers with light polarizations parallel and perpendicular to the orientational direction are measured with a time resolution of 0.3ps （FWHM）, and are found to consist of two components, i.e., the coherent instantaneous nonlinear response and slow response due to the formation of excited molecules. A high anisotropic ratio of x^（3）e, 10.8 ：k 1.2, is observed for the oriented layers.

Fast Optical Switching Using Oriented Cyanine Dye-Doped Nematic Liquid Crystal

A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical properties of the oriented NK-125-SCB layers are measured by the resonant femtosecond degenerate four-wave mixing （DFWM） technique at 760 nm. The third-order nonlinear optical susceptibility of one of the present samples is 5.5×10^-8 esu. The slow DFWM response of the NK-125-SCB layers due to a population grating is accelerated by the increasing laser power because of amplified spontaneous emission （ASE）. On the other hand, we do not observe a similar phenomenon for NK-125- polyethylene glycol （PEG-400）. Oriented NK-125 molecules in nematic liquid crystals must have very high ASE efficiency. Hence the population grating in a DFWM signal disappears within about 4 ps. It is expected that NK-125-SCB can be used as a material for very fast all-optical switching.