环氧树脂基多孔光学增透膜的制备及其性能研究

利用低分子量环氧树脂(DGEBA)在固化后和与之共混的聚氯乙烯(PVC)之间产生的相分离,用丁酮抽提其中的PVC组分,制备了环氧树脂基多孔增透膜。测试结果表明,当mDOEBA／mPVC=30／70、膜厚为110nm时,增透膜的透过率最高,达96％以上。薄膜在水或甲苯中煮沸不发生收缩、脱落,表现良好的粘附力和机械强度。     

Preparation of micrometer-sized, monodisperse "janus" composite polymer particles having temperature-sensitive polymer brushes at half of the surface by seeded atom transfer radical polymerization

Micrometer-sized, monodisperse polystyrene (PS)/poly[methyl methacrylate-(chloromethyl)styrene] [P(MMA-CMS)] composite particles having hemispherical structure were prepared by solvent evaporation from toluene droplets containing dissolved PS and P(MMA-CMS) dispersed in aqueous solution, which had been prepared using the membrane method. The formation of hemispherical ("Janus") morphology by phase separation between the PS and the P(MMA-CMS) was confirmed by both optical and electron microscopy. Atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DM) was subsequently carried out in the presence of hemispherical PS/P(MMA-CMS) composite particles in an aqueous dispersed system. After polymerization, the morphology of the particles changed from spherical to "mushroom" shape as observed by scanning electron microscopy, indicating that DM polymerized inside or on the surface of half [P(MMA-CMS) phase] of the particles. 1H NMR spectra were consistent with chloromethyl functional groups in P(MMA-CMS) operating as ATRP initiators in the DM polymerization.     

Highly selective vapochromic fluorescence of polycarbonate films Doped with an ICT‐Based solvatochromic probe

The vapochromic properties of a fluorescent 3‐[2‐(4‐nitrophenyl) ethenyl]‐1‐(2‐ethylhexyl)‐2‐methylindole (NPEMI‐E) characterized by intramolecular charge transfer (ICT) character, dispersed in polycarbonate (PC) films is reported. NPEMI‐E solvatochromism is investigated by means of experimental and computational methods. Fluorescent PC films containing 0.1 wt % of NPEMI‐E are prepared and exposed to saturated atmospheres of different volatile organic compounds (VOCs). NPEMI‐E/PC films show remarkable and reversible vapochromism when exposed to VOCs with high polarity index and favorable interaction with PC matrix such as CHCl₃. Only minor variations in the emission wavelength are actually recorded for all other classes of VOCs investigated. The hue parameter is also used for the effective extraction of spectral information from digital color images without the need for wavelength discriminators. Overall, the present results support the use of NPEMI‐E/PC films for the cost‐effective detection of CHCl₃ vapors. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1171–1180     

Enhanced ordering in polymer stabilised ferroelectric liquid crystal guest–host composites: evidence by polarised fluorescence spectroscopy

Guest–host polymer stabilised ferroelectric liquid crystal (PSFLC) composite films have been prepared by polymerisation-induced phase separation process. A small quantity (0.1, 0.25 and 0.5 wt %) of anthraquinone dye in PSFLC host matrix was homogeneously dispersed to create molecular ordering in fibrils network of guest–host composite film. Ordered twisted fibril morphology was clearly observed through optical polarising microscope and thus we determined the order parameter from the dichroism measurements with the help of polarised fluorescence spectroscopy, which impacts the significant contribution of dye molecules into the smectic layers of the host polymer stabilised ferroelectric matrix.     

Direct, sensitive and selective detection of free fatty acids by high-performance liquid chromatography with post-column ion-pair extraction and absorbance detection

Free fatty acids (C8-C18) are separated by reversed-phase liquid chromatography and detected using a simple post-column dynamic extraction system in which the acids are extracted as ion pairs with chloroform from the aqueous acetonitrile (gradient: 79-99% acetonitrile) mobile phase after the post-column addition of aqueous Methylene Blue solution. The chloroform phase containing the ion pairs is monitored with an absorbance detector at 651 nm. The detection limits ranged from 26 to 83 ng, depending upon the acid, with coefficients of variation of 1.2-14%. Application of the method to butter and margarine samples permitted detection of free fatty acids down to 35 ppm and in orange juice, down to 0.5 ppm using only an organic solvent extraction without further sample clean-up for isolation of the fatty acids.     

Enhanced fluorescence from arrays of nanoholes in a gold film

Arrays of sub-wavelength holes (nanoholes) in gold films were used as a substrate for enhanced fluorescence spectroscopy. Seven arrays of nanoholes with distinct periodicities (distances between the holes) were fabricated. The arrays were then spin-coated with polystyrene films containing different concentrations of the fluorescent dye oxazine 720. The dye was excited via resonant extraordinary transmission of the laser source through the nanoholes. Enhanced fluorescence was observed when the geometric characteristics of the arrays allowed for an enhancement in the transmitted excitation. This enhancement occurred via surface plasmon excitation by the laser and a consequential increase in the local electromagnetic field in a sub-wavelength region at the metal-film interface. It was demonstrated that the sensitivity of the fluorescence measurement (change in signal vs change in dye concentration in the polymer film) is significantly larger at the surface plasmon resonance conditions than that obtained from equivalent films on glass substrates. Enhancement factors for the fluorescence emission were calculated for each array, with a maximum enhancement of close to 2 orders of magnitude as compared to the emission of films on glass. The results presented here indicate that arrays of nanoholes are interesting substrates for the development of fluorescence sensors based on surface plasmon resonance, as they provide a platform that allows both spatial confinement and enhancement of excitation light. Moreover, the collinear characteristics of the present optical setup, due to the resonant extraordinary transmission through the nanohole arrays, are more conducive to miniaturization and chip integration than more traditional experimental geometries.     

Chiral supramolecular assemblies of a squaraine dye in solution and thin films: concentration-, temperature-, and solvent-induced chirality inversion

We prepared novel cholesterol-appended squaraine dye 1 and model squaraine dye 2 and investigated their aggregation behavior in solution and thin films using photophysical, chiroptical, and microscopic techniques. Investigations on the dependence of aggregation on solvent composition (good/poor, CHCl3/CH3CN) demonstrated that squaraine dye 1 forms two novel H-type chiral supramolecular assemblies with opposite chirality at different good/poor solvent compositions. Model compound 2 formed J-type achiral assemblies under similar conditions. The supramolecular assembly of 1 observed at lower fractions of the poor solvent could be assigned to the thermodynamically stable form, while a kinetically controlled assembly is formed at higher fractions of the poor solvent. This assignment is evidenced by temperature- and concentration-dependent experiments. With increasing temperature, the chirality of the kinetically controlled aggregate was lost and, on cooling, the aggregate with the opposite chirality was formed. On further heating and cooling the aggregates thus formed resulted in no significant changes in chirality, that is they are thermodynamically stable. Similarly, at lower concentrations, the thermodynamically stable form exists, but at higher concentration aggregation was found to proceed with kinetic control. Based on these observations it can be assumed that formation of the kinetically controlled assembly might be largely dependent on the presence of the nonpolar cholesterol moiety as well as the amount of poor solvent present. However, under solvent-free conditions, structurally different aggregates were observed when drop cast from solutions containing monomer, whereas a left-handed CD signal corresponding to the thermodynamically controlled assemblies was observed from pre-aggregated solutions.     

Swelling the micelle core surrounding single-walled carbon nanotubes with water-immiscible organic solvents

Solvatochromic shifts in the absorbance and fluorescence spectra are observed when surfactant-stabilized aqueous single-walled carbon nanotube (SWNT) suspensions are mixed with immiscible organic solvents. When aqueous surfactant-suspended SWNTs are mixed with o-dichlorobenzene, the spectra closely match the peaks for SWNTs dispersed in only pure o-dichlorobenzene. These spectral changes suggest that the hydrophobic region of the micelle surrounding SWNTs swells with the organic solvent when mixed. The solvatochromic shifts of the aqueous SWNT suspensions are reversible once the solvent evaporates. However, some surfactant-solvent systems show permanent changes to the fluorescence emission intensity after exposure to the organic solvent. The intensity of some large diameter SWNT (n, m) types increase by more than 175%. These differences are attributed to surfactant reorganization, which can improve nanotube coverage, resulting in decreased exposure to quenching mechanisms from the aqueous phase.     

Photopolymerisation kinetics and electro-optical properties in mixtures of dichroic dye-doped nematic liquid crystal and photocurable polymer

This work reports the effect of dye on the photopolymerisation and electro-optical properties of polymer dispersed liquid crystal (PDLC) composite films. Dichroic PDLC (DPDLC) films based on a photocurable polymer and nematic liquid crystal (LC) with an azo dichroic dye were prepared by photopolymerisation-induced phase separation method. Polarising optical microscopy has been used for monitoring the phase separation kinetics and two-phase morphology evolution in the DPDLC system. LC domains with radial structures during initial period of phase separation adopted a resultant morphology of bipolar configuration over the course of polymerisation. The phase separation and morphology of LC domains was found to be dependent on the amount of dye used. Moreover, the addition of small amount of dye reduced the switching voltage, and enhanced the contrast ratio with improved switching time in the PDLC films. It was shown that, under the application of an electric field, the molecular orientation and absorbance of dichroic dye can be controlled in DPDLC to induce non-linearity and colour contrast without the use of polarisers.     

High dispersion and fluorescence of anthracene doped in polyphenylsiloxane films

Phenylsilsesquioxane-diphenylsiloxane glass thick films doped with anthracene were prepared from homogeneous coating sols obtained from two different approaches. One approach consisted in incorporating the dye during the glass preparation (which implies the incorporation of the dye in an aqueous media). The doped-glass was further dissolved in the solvents mixture composed of cyclohexane and acetone. The other approach which is non-aqueous consisted simply in dissolving directly the preformed non-doped polyphenylsiloxane glass in the dye solutions. The stability of the organic-inorganic hybrid glass matrix in most organic solvents makes possible the incorporation of the dye without problems of miscibility and dispersion in the hybrid matrix. The coating was performed at room temperature using spin-coating technique prior to further heat-treatment. Crack-free and homogeneous films of high optical quality were obtained. The optical properties of the doped films based on their absorption and emission spectra were discussed owing the incorporation route of the dye. The results showed that the non-aqueous approach used to incorporate the dye minimizes the dye aggregation. This property associated to the preparation route permits to obtain optically active hybrid films loaded with high concentrations of anthracene (in the order of 10⁻² M) which enhance the fluorescence of the doped films. The hybrid doped-films obtained represent therefore a tremendous potential for applications in the field of optics and photonics including the development of new nonlinear optical materials. Bouzid Menaa and Masahide Takahashi both the author contributed equally.     

混合溶剂对可录型光盘中吲哚类菁染料薄膜性能的影响

本文采用紫外可见光谱、FT-IR及AFM等手段,研究了混合溶剂对光盘记录介质吲哚类菁染料薄膜光学性能、稳定性和表面结构的影响.发现在不同混合溶剂下涂出的相同膜厚的染料薄膜,其光学性能和表面形貌都有很大的差异.不同的混合溶剂都存在一个最佳混合体积比,染料在此体积比下旋涂出膜的光学性能和表面形貌均优于单一溶剂下涂出的膜.对比不同混合溶剂涂出的膜的光学性质及AFM的观测结果,发现二丙酮醇与氯仿在等体积比混合、四氟丙醇与氯仿在7:3体积下混合时效果最好,易得到反射率高,表面较平整的染料薄膜.     

PET suppression of acridinedione dyes by urea derivatives in water and methanol

Spectroscopic investigations involving the interaction of acridinedione dyes with urea and its derivatives in water and methanol were carried out by absorption, steady-state fluorescence, and time-resolved fluorescence measurements. The hydrogen-bonding properties of urea and derivatives in aqueous solutions are found to be distinctly different from those observed in methanol. Urea, which can serve both as a hydrogen bond donor as well as an acceptor and has a unique hydrogen-bonding feature, helps in studying urea interaction with fluorophores in aqueous solutions, micelles, and alcohol. In our studies, we have used acridinedione dyes as the probe. We report that the hydrophobic interaction of urea with dye predominates by weakening of the hydrogen-bonding interaction of the solvent and urea derivatives with increase in the hydrophobicity of urea derivatives. In methanol, the hydrogen bonding between solvent and urea derivatives predominating over the hydrophobicity of the urea derivatives is observed. The presence of alkyl group substitution in the N-H moiety with a function of increasing concentration resulting in the creation of a more favorable hydrophobic environment to the dye molecule to reside in the hydrophobic shell phase rather than in the bulk aqueous phase is illustrated. The hydrophobic interaction of dye with urea in aqueous solution predominates because of the weakening of the hydrogen bonding of the solvent and urea derivatives, and the photoinduced electron transfer (PET) process is used as a marker to identify the hydrophobic interaction illustrated in our studies.     

Dispersion and Interaction of Charged Fluorescent Dyes in Protein-Polymer Surfactant-based Non-Aqueous Liquid

Viscous, non-aqueous liquid comprising stoichiometric conjugates of polymer surfactant-bovine serum albumin (PSpBSA) is used as a host matrix for the dispersion of chemically distinct hydrophilic dyes. Using a combination of bright field polarized optical microscopy and fluorescence spectroscopy, we investigate the dispersion of dry and powdered cationic (Rhodamine 6G; Rh6G) and anionic (Fluorescein; FL) dyes in the PSpBSA liquid at room temperature. As the dyes disperse and dissolve in the PSpBSA liquid, it results in a pronounced increase in emission intensity of the former. Interestingly, a shift from 571 to 582 nm is observed in the emission maxima of Rh6G as it disperses in the PSpBSA solvent. Whilst no such red shift is found for the Rh6G dispersion in the aqueous solutions of either native BSA or polymer-surfactant conjugated BSA, a similar shift occurs when Rh6G is dispersed in neat polymer-surfactant (PS), suggesting the interaction of the dye with the PS chains. In the case of anionic FL, no shift is observed in its emission maximum as it disperses in the PSpBSA liquid. Furthermore, within 120 minutes of FL dispersion in the PSpBSA liquid, we observe a ≈26 % decrease in the tryptophan emission intensity (λ_exc.=285 nm; λ_emi.=330 nm) of BSA, which could be attributed to both static and dynamic quenching. Our findings provide a proof of concept of an alternative non-aqueous solvent matrix which can dissolve and disperse charged fluorescent dyes, provide suitable binding sites, and show substantial photoluminescence. Thus, it can be envisaged for utilization as an alternative solvent medium for lasing dyes and related applications.     

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.     

Optimization of FLEC-SPME for field passive sampling of VOCs emitted from solid building materials

The FLEC^®-SPME sampler, described in a previous paper, consists of an emission cell coupled with solid phase microextraction (SPME) for passive sampling of VOCs emitted from building materials. It represents an interesting alternative to standard dynamic sampling protocol as it is easier to implement. If standard dynamic sampling determines emission rates, passive FLEC^®-SPME aims to the determination of the concentration in air at the material surface. That could be assumed provided that material/air equilibrium is reached. Thus, VOCs emission kinetics were studied for 3 different materials (pine wood panel, carpet and PVC floor) to determine equilibrium times. Then, the relevance of the method has been assessed using new materials through a 3-day emission test. Qualitative results were compared to those obtained from the standard method to check the ability of FLEC^®-SPME to detect the most toxic compounds, named “VOCs of interest” and listed in the French regulation. Minor differences were observed, so this methodology seems promising, especially for field studies aiming in the identification of VOCs sources in buildings. Moreover, the concentration at the material surface combined to emission modeling could be used to predict indoor VOCs concentrations helping in indoor air quality diagnostic.     

Two-step resonance energy transfer between dyes in layered silicate films

Single- and two-step fluorescence resonance energy transfer (FRET) was investigated between laser dyes rhodamine 123 (R123), rhodamine 610 (R610), and oxazine 4 (Ox4). The dye molecules played the role of molecular antennas and energy donors (ED, R123), energy acceptors (EA, Ox4), or both (R610). The dye cations were embedded in the films based on layered silicate laponite (Lap) with the thickness of several μm. Optically homogeneous films were prepared directly from dye/Lap colloids. Dye concentration in the films was high enough for FRET to occur but sufficiently low to prevent the formation of large amounts of molecular aggregates. The films were characterized by absorption and fluorescence spectroscopies, and their optical properties were compared with colloid precursors and dye aqueous solutions. The phenomenon of FRET was confirmed by means of steady-state and time-resolved fluorescence spectroscopies. Significant quenching of ED emission in favor of the luminescence from EA molecules was observed. FRET led to the decrease in the lifetimes of excited states of ED molecules. Molecular orientation of dye molecules was determined by polarized absorption and fluorescence spectroscopies. Almost parallel orientation with respect to silicate surface (～30°) was determined for all fluorescent species of the dyes. Theoretical model on relationship between anisotropy and molecular orientation of the fluorophores fits well with measured data. The analysis of anisotropy measurements confirmed the significant role of FRET in the phenomenon of light depolarization.     

Surface-enhanced spectroscopy of Langmuir—Blodgett films of N-octyl,N′-isobutyl-3,4:9,10-perylene-bis(dicarboximide)

The infrared, resonant Raman and surface-enhanced resonant Raman spectra of N-octyl, N′-isobutyl-3,4:9,10-perylene-bis(dicarboximide) (PBDC) were obtained and the aggregation of PBDC molecules was studied using surface-enhanced fluorescence. Langmuir—Blodgett (LB) films of the neat dye as well as mixed layers with arachidic acid, were prepared and transferred to glass slides and surface-enhanced active surfaces for spectroscopic characterization. A strong red shifted excimer emission was characteristic of LB layers of the neat material and of the thin solid films formed by dipping a glass slide into a solution containing the dye and a volatile solvent. However, using mixed LB monolayers of PBDC and arachidic acid, the surface-enhanced fluorescence of the monomer was observed. The surface-enhanced scattering was measured for both neat and mixed LB layers.     

Characterization of a novel water-soluble 3,4,9,10-perylenetetracarboxylic diimide in solution and in self-assembled zirconium phosphonate thin films

The properties of N,N'-bis(2-phosphonoethyl)-3,4,9,10-perylenetetracarboxylic diimide (PPDI), a water-soluble perylene dye, have been studied in solution and in thin films. Absorption spectra showed that PPDI exists in the monomeric form in water/ethanol (1:1) and water/dimethyl sulfoxide (DMSO) (3:7) mixtures, but forms dimers in water and higher aggregates in ethanol. The PPDI monomer is highly fluorescent, in contrast to the dimers and aggregates, which are nonfluorescent. The monomer/dimer equilibrium was conveniently followed in a water/ethanol (7:3) mixture by varying the dye concentration. An equilibrium constant of K = 1.25 x 10(5) M(-1) was estimated for the dimerization process in this solvent mixture. The addition of cetyl trimethylammonium bromide (CTAB), a cationic surfactant, to aqueous solutions of PPDI resulted in the dissociation of the dimers, showing that the dye was incorporated into the micellar phase. Self-assembled thin films of PPDI were grown on both silica gel particles and flat surfaces, using zirconium phosphonate chemistry. The growth of multilayered films on flat surfaces was monitored by ellipsometry (silicon substrates) and UV/Vis spectroscopy (quartz slides), and was linear with the number of deposition cycles. No fluorescence was detected from the PPDI films, and the absorption spectra of the films were quite similar to the spectrum of the compound in ethanol, indicating that the dye molecules were stacked in the films. Mixed monolayers containing PPDI and N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) on quartz were also prepared. Monolayers obtained by codeposition from solutions containing both PPDI and PNDI were richer in PPDI, even when the solution contained a large excess of the naphthalene derivative, showing that pi-stacking of PPDI is an important driving force in the formation of the films.     

A chromoreactand for optical sensing of amphetamines

A bisazo dye is presented that undergoes a reversible chemical reaction with amphetamine in thin layers of plasticised PVC and changes its colour from blue to red. The sensitivity of the dye in the polymer layer covers the range from 0.3 to 30 mmol L(-1) amphetamine with a limit of detection of 0.1 mmol L(-1). The maximum signal changes are observed at 630 nm making the dye compatible with cheap light sources and detectors.     

Bireactive calamitic liquid crystals derived from fluorene ester linkage

New thermotropic liquid crystalline monomer esters, containing fluorene in their mesogenic core with luminescent properties, were synthesized and characterized. The monomers studied exhibited a broad mesomorphic range and a nematic phase was identified by differential scanning calorimetry and polarized optical microscopy. Absorption and photoluminescence spectra studied in solution indicated that these compounds possess good optical stability. Linearly polarized light emission was observed in oriented thin films prepared by an in-situ photopolymerization technique. The preparation of oriented thin films shows a preferential emission direction necessary for application in linearly polarized blue light-emitting diodes.