Polymeric Dye Research Articles

The employment of a removable chitosan-derivatized polymeric sensitizer in the photooxidation of polyhydroxylated water-pollutants.

The known O2((1)∆g)-sensitizer system Chitosan bounded Rose Bengal (CH-RB), with Rose Bengal (RB) immobilized by irreversible covalent bonding to the polymer Chitosan (CH), soluble in aquous acidic medium, was employed in the photodegradation of three tri-hydroxy benzene water-contaminants (THBs). The system sensitizes the O2((1)∆g)-mediated photodegradation of THBs by a process kinetically favored, as compared to that employing free RB dissolved in the same solvent. Additionally the free xanthene dye, degradable by O2((1)∆g) through self-sensitization upon prolonged light-exposure, is considerably protected when bonded to CH-polymer. The polymeric sensitizer, totally insoluble in neutral medium, can be removed from the solution after the photodegradative cycle by precipitation through a simple pH change. This fact constitutes an interesting aspect in the context of photoremediation of confined polluted waters. In other words, the sensitizing system could be useful for avoiding to dissolve dyestuffs in the polluted waters, in order to act as conventional sunlight-absorbing dye-sensitizers. In parallel the interaction CH-O2((1)∆g) in acidic solution was evaluated. The polymer quenches the oxidative species with a rate constant 2.4 × 10(8) M(-1) s(-1) being the process mostly attributable to a physical interaction. This fact promotes the photoprotection of the bonded dye in the CH-RB polymer.

Coupled π-conjugated chromophores: Squaraine dye dimers as two connected pendulums

Intense absorption ability in the near infrared (NIR) region is mandatory for many technologies and applications. The design thereof is however quite complex since only a few dye classes show these properties. Polymeric squaraine dyes have them however they are mostly hardly soluble. Herein four dimeric soluble and easy to prepare squaraine dye dimers are reported with absorption maxima between 679 and 805 nm. The synthesis, characterisation, the determination of the physicochemical properties and the in silico study of the calculated molecular geometry, the molecular orbitals, and the calculated total charge density surface were compared. The coupling of the two chromophores is concluded as a matter of the distance in-between, the π-electron system of the bridge, the spatial orientation thereof, and the spatial orientation of the electronic transition moment. The closer the two chromophores were and the less out-of-plane elements the bridge has, the smaller the optical band gap is.

Enhanced photodynamic therapy and effective elimination of cancer stem cells using surfactant-polymer nanoparticles.

Photodynamic therapy is a potentially curative treatment for various types of cancer. It involves energy transfer from an excited photosensitizer to surrounding oxygen molecules to produce cytotoxic singlet oxygen species, a process termed as type II reaction. The efficiency of photodynamic therapy is greatly reduced because of the reduced levels of oxygen, often found in tumor microenvironments that also house cancer stem cells, a subpopulation of tumor cells that are characterized by enhanced tumorigenicity and resistance to conventional therapies. We show here that encapsulation of a photosensitizer, methylene blue, in alginate-Aerosol OT nanoparticles leads to an increased production of reactive oxygen species (ROS) under both normoxic and hypoxic conditions. ROS generation was found to depend on the interaction of the cationic photosensitizer with the anionic alginate polymer. Dye-polymer interaction was characterized by formation of methylene blue dimers, potentially enabling electron transfer and a type I photochemical reaction that is less sensitive to environmental oxygen concentration. We also find that nanoparticle encapsulated methylene blue has the capacity to eliminate cancer stem cells under hypoxic conditions, an important goal of current cancer therapy.

Design of a New Energy‐Harvesting Electrochromic Window Based on an Organic Polymeric Dye, a Cobalt Couple, and PProDOT‐Me2

A new design for an energy‐harvesting electrochromic window (EH‐ECW) based on the fusion of two technologies, organic electrochromic windows and dye‐sensitized solar cells (DSSCs), is presented. Unlike other power‐generating smart windows, such as photoelectrochromic devices that are passive and only contain two states (i.e., a closed‐circuit colored state and an open‐circuit bleaching state), EH‐ECW allows active tuning of the transmittance by varying the applied potential and it functions as a photovoltaic cell based on a DSSC. The resulting device demonstrates a fast switching rate of 1 s in both the bleaching and coloring processes through the use of an electrochromic polymer as a counter electrode layer. To increase the transmittance of the device, a cobalt redox couple and a light‐colored, yet efficient, organic dye are used. The organic dye contains a polymeric structure that contributes to the high cyclic stability. The device exhibits a power conversion efficiency (PCE) of 4.5% (100 mW cm‐2) under AM 1.5 irradiation, a change in transmittance of 34% upon applied potential, and shows only 3% degradation in the PCE after 5000 cycles.

Enhanced nonlinearity by H-bonded polymer–dye complex in liquid crystal for holographic gratings

We have studied a new heterogeneous liquid-crystalline material where H-bonded polymer–azo-dye complexes are used as dopants to the liquid crystal (LC) bulk at a very low concentration. Double enhancement of the holographic gratings’ diffraction efficiency occurred in the complex-doped LC compared to dye-doped LC. The grating formation/relaxation processes in complex-doped LC showed anomalies that were explained by the presence of polymer with H bonds. The gratings appeared to be formed due to a change of both the absorption coefficient and refractive index. Using such complexes as dopants gives perspectives for tuning and control of the LC properties, and for possible optical applications.

Environmentally friendly coloration of cotton by the UV ‐induced photografting of α‐bromoacrylamido dyes

Conventional wet dyeing based on dye diffusion and adsorption in water requires large amounts of salt, time, and energy. α-Bromoacrylamido dyes are photografted onto cotton at room temperature as an environmentally friendly coloration process. Dye-originated radicals are produced by the photoscission of the carbon–sulfur and carbon–bromine bonds of the dyes and subsequently abstract hydrogen atoms to generate cellulose radicals which can initiate graft copolymerisation. About 88% of the dyes are polymerised, and the degree of polymerisation is estimated to be 12.7 or more, which was substantiated by mass and elemental analyses. The colour yield of the photografted cotton is seven times higher than that of conventional dyeing. Furthermore, good colour fastness properties are attributed to the water-insoluble polymeric dyes formed.

Dual-Emissive Difluoroboron Naphthyl-Phenyl β-Diketonate Polylactide Materials: Effects of Heavy Atom Placement and Polymer Molecular Weight

Luminescent materials are important for imaging and sensing. Aromatic difluoroboron β-diketonate complexes (BF2bdks) are classic fluorescent molecules that have been explored as photochemical reagents, two-photon dyes, and oxygen sensors. A series of BF2bdks with naphthyl and phenyl groups was synthesized, and photophysical properties were investigated in both methylene chloride and poly(lactic acid) (PLA). Polymer molecular weight and dye attachment site along with bromide heavy atom placement were varied to tune optical properties of dye–PLA materials. Systems without heavy atoms have long phosphorescence lifetimes, which is useful for lifetime-based oxygen sensing. Bromine substitution on the naphthyl ring resulted in intense, clearly distinguishable fluorescence and phosphorescence peaks important for ratiometric oxygen sensing and imaging.

Effect of chemical parameters on the interaction between cationic dyes and poly(acrylic acid)

Abstract Being polymers and electrolytes, polyelectrolytes are widely used in many applications. In perspective of dye removal from textile effluents, they have been used in coagulation–flocculation and to a lesser extent in polyelectrolyte enhanced ultrafiltration. To optimize the abovementioned process we need to study in detail the interaction of dye with polyelectrolyte in conditions near the industry reality. In this context we investigate herein the effect of chemicals additives, NaCl, surfactant, pH on the behavior of two model cationic dyes, methylene blue (MB) and toluidine blue (TB), with polyacrylic acid polymer (PAA). Using spectrophotometric method it was found that the poly(acrylic acid) induced metachromasy in the dyes resulting by the blue shift of the absorbance confirming the formation of dye polymer complexes. The stoichiometry of MB–PAA and TB–PAA complexes determined by the ratio method was found to be 2:1. The stability constant of the complexes at 298 K was found to be 5332 for MB–PAA and 4358 dm3 mol−1 for TB–PAA and the amount of additives inducing total destabilization of the complex were determined.

Synthesis and Calculation of Some Linear Optical Properties and the Oscillator Strength Parameters of a New Azo Dye Polymer Compound

Synthesis and Calculation of Some Linear Optical Properties and the Oscillator Strength Parameters of a New Azo Dye Polymer Compound

Photoresistance and photo induced current hysteresis in bulk heterojunction systems P3HT–PCBM–polymethine dye

Organic dyes can be used as a polar dipole component to create strong local electrical field and promote exciton dissociation in polymer bulk heterojunction (BHJ) solar cells. Some polymethine dyes are characterized with strong IR absorption and therefore can significantly improve light energy harvesting characteristics in such devices due to extension of the absorption spectrum of the photoconducting layer to the IR region. In a view of these opportunities, photovoltaic properties of BHJ systems constituted with poly-3-hexylthiophene (P3HT) as an electron donor, 6,6-phenyl-C61-butyric acid methyl ester (PCBM) fullerene-type electron acceptor, and cation polymethine or merocyanine dyes were studied depending on the dye concentration and under different light excitation conditions. A new physical effect of photoinduced current hysteresis was observed in dye containing BHJ solar cells, when the dye concentration was in the range of 16–60%. The photocurrent hysteresis is detected only when simultaneously polythiophene and dye molecules are excited with light (white light excitation), while no current hysteresis can be seen in the dark or under selective excitation of the polymer component (490nm) or dye component (740nm) of the BHJ system. In addition, significant reduction of the photocurrent collected from the dye-containing devices under illumination with white light in comparison to a selective excitation of the polymer component only is observed.Therefore, the phenomenon can be described as an illumination induced photoresistance of the composite BHJ layer. It can be explained based on energy diagram consideration as a generation of transition dipole moments at polymethine dye molecules located close to the heterojunction and thus opposing donor–acceptor charge transfer events.

Performance of dye-sensitized solar cells based on various sensitizers applied on TiO2-Nb2O5 core/shell photoanode structure

The present investigation described the performance of dye-sensitized solar cells (DSSCs) based on various sensitizers applied on TiO2-Nb2O5 core/shell photoanode film. The novel photoanodes were prepared using composite of TiO2 nanoparticles (TNPs) and TiO2 nanorods (TNRs) as core (TNPRs) layer with Nb2O5 shell coating. As well, tantalum pentoxide (Ta2O5), a blocking layer applied over the core/shell film. The DSSCs were fabricated based on various sensitizers namely zinc phthalocyanine, indoline, indigo carmine, zinc porphyrin, N719, coumarin NKX-2700, polymer dye, quantum dots (QDs), perylene and squaraine. The I–V characteristics of the DSSCs, photocurrent density (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoconversion efficiency (PCE) were determined under illumination of AM 1.5 G. Electrochemical impedance spectroscopy (EIS) analysis is carried out to study the charge transport and life-time of charge carriers at photoanode/dye/electrolyte interface of the DSSCs. The I–V and EIS results explicated that the core/shell with blocking layers were able to alleviate the electron transport and suppressed charge recombination at photoanode/dye/electrolyte interface of the DSSCs. Concerning the sensitizers, PCE of the DSSCs exemplify the order N719 > zinc porphyrin > coumarin NKX-2700 > indoline > squaraine > QDs > zinc phthalocyanine > perylene > polymer dye > indigo carmine dye. The results of the present work demonstrated that among the sensitizers studied, N719 showed the highest PCE and fill factor. Besides, the metal-free organic sensitizers (coumarin NKX-2700 and indoline) exhibited comparable PCE as compared to N719.

Oxygen-Sensitive Phosphorescent Nanomaterials Produced from High-Density Polyethylene Films by Local Solvent-Crazing

Discrete solid-state phosphorescent oxygen sensors produced by local solvent-crazing of high density polyethylene films are described. The simple spotting of dye solution followed by tensile drawing of the polymer substrate provides uniform nanostructures with good spatial control, effective encapsulation of dye molecules, and quenchability by O2. The dye-polymer composite sensors prepared using toluene as a solvent and stabilized by annealing at high temperature, show moderate optical signals, near-optimal sensitivity to O2 (RSD at 21 KPa 1.9%), and reproducible phosphorescence lifetime readings. Calibration experiments performed over 0-25 kPa O2 and 10-30 °C temperatures ranges reveal linear Stern-Volmer plots and temperature dependences and minimal effect of humidity on sensor calibration. The high degree of lateral and in-depth homogeneity of these O2-sensitive materials was confirmed by high-resolution atomic force and wide-field optical microscopy, including 2D and 3D phosphorescence lifetime imaging.

The effect of pump depletion on reversible photodegradation

We model the effect of pump depletion on reversible photodegradation using the extended domain model [Anderson and Kuzyk, arXiv:1309.5176v1, 2013] and the Beer–Lambert law. We find that neglecting pump absorption in the analysis of the linear optical transmittance leads to an underestimate of the degree and rate of photodegradation. The model is used to accurately measure the molecular absorbance cross sections of the three species involved in photodegradation of disperse orange 11 dye in (poly)methyl-methacralate polymer (DO11/PMMA). Finally we find that the processing history of a dye-doped polymer affects reversible photodegradation, with polymerized monomer solutions of DO11 being more photostable than those prepared from solvent evaporated dye-polymer solutions.

Application of prodigiosin as a colorant for polyolefines

Serratia marcescens strain 9986 is a producer of prodigiosin used as a dye of polyolefines (polyethylene, ultratene). The biosynthesis of pigment was closely connected with controlled growth parameters. A prodigiosin yield 0.2 - 0.4 mg per l of culture medium in the batch culture under aerobic conditions was obtained. Prodigiosin was extracted from crude biomass treated by 0.1% of sodium dodecyl sulfate (SDS). This novel elaborated stage is necessary for thermostability a dye in polymer. The consumption of prodigiosin preparation is more economical in the technology of the coloration of polyolefines. The elaborated method has been manufactured for dyeing polyethylene by biological pigment-articles of the common use corresponding to the technological standard.

Applications of Conductive Polymers to Electrochemical Sensors and Energy Conversion Electrodes

ABSTRACT: The electrical conductive polymers (ECPs) reported at my research group are introduced in thisreview, which works are started from the late Professor Su-Moon Park’s pioneering research forpolyaniline at the University of New Mexico. The electrochemical and spectroelectrochemicalproperties and their applications to sensor and energy conversion systems are briefly described. Atfirst, the growth and degradation mechanism of polyaniline describes and we extend to polypyrrole,polyazulene, polydiaminonaphthalenes, and polyterthiophene derivatives. In addition, the prepara-tion of monomer precursors having functional groups is briefly described that can give us manyexceptional applications for several chemical reactions. We describe the application of these ECPsfor the fabrication of chemical sensors, biosensors, biofuel cells, and solar cells.Keywords: Electrical conductive polymer, Polymer metal complex, Electrochemical sensors, Poly-mer dye solar cells, Biofuel cells Received January 9, 2014 : Accepted Febuary 3, 2014

Effects of multi anchoring groups of catecholamine polymer dyes on the electrical characteristics of metal free dye-sensitized solar cells: A comparison study

Poly epinephrine and poly dopamine were synthesized through a new manner in an alkaline solution containing tris(hydroxymethyl)aminomethane (THAM) buffer with pH=8.5 under nitrogen atmosphere to make the dyes with very strong adhesion and efficient electron injection by direct dye-to-TiO2 charge transfer. These dyes were used for fabrication of metal free dye sensitized solar cells. Photovoltaic characteristics were obtained for cells made by utilization of two dyes and it was established that the poly epinephrine dye exhibited larger current density and energy conversion efficiency than the poly dopamine dye. This is attributed to the strong attachment of the poly epinephrine dye to the surface of the TiO2 nanoparticles due to the presence of three anchoring OH groups on the back bone of the polymer. Under simulated AM 1.5G solar light (100mWcm−2), a poly epinephrine-sensitized cell exhibited a short circuit current density of 3.63mAcm−2, and overall power conversion efficiency of 0.41%, which is almost 60% larger than that of the poly dopamine dye-sensitized cell (0.26%). UV–Vis absorption spectra of the dyes were recorded and it was shown that absorption by poly epinephrine has extended over a broad range of wavelengths from UV up to mid-range of visible region and has a peak centered at 420nm. However the range of absorption wavelengths for poly dopamine is limited to the initial part of visible region and the peak wavelength occurs at 257nm. Moreover, optical band gaps of the dyes were obtained from wavelengths of the absorption edges of the respecting UV–Vis absorption spectra (2.25 and 3.32eV for poly epinephrine and poly dopamine respectively). HOMO and LUMO energy levels of the dyes were estimated from cyclic voltammograms. Electrochemical impedance spectroscopy was applied to study of the electrical properties of the cells including poly epinephrine and poly dopamine dyes.

Colloidal-Sized Metal–Organic Frameworks: Synthesis and Applications

Colloidal metal-organic frameworks (CMOFs), nanoporous colloidal-sized crystals that are uniform in both size and polyhedral shape, are crystals composed of metal ions and organic bridging ligands, which can be used as building blocks for self-assembly in organic and aqueous liquids. They stand in contrast to conventional metal-organic frameworks (MOFs), which scientists normally study in the form of bulk crystalline powders. However, powder MOFs generally have random crystal size and shape and therefore do not possess either a definite mutual arrangement with adjacent particles or uniformity. CMOFs do have this quality, which can be important in vital uptake and release kinetics. In this Account, we present the diverse methods of synthesis, pore chemistry control, surface modification, and assembly techniques of CMOFs. In addition, we survey recent achievements and future applications in this emerging field. There is potential for a paradigm shift, away from using just bulk crystalline powders, towards using particles whose size and shape are regulated. The concept of colloidal MOFs takes into account that nanoporous MOFs, conventionally prepared in the form of bulk crystalline powders with random crystal size, shape, and orientation, may also form colloidal-sized objects with uniform size and morphology. Furthermore, the traditional MOF functions that depend on porosity present additional control over those MOF functions that depend on pore interactions. They also can enable controlled spatial arrangements between neighboring particles. To begin, we discuss progress regarding synthesis of MOF nano- and microcrystals whose crystal size and shape are well regulated. Next, we review the methods to modify the surfaces with dye molecules and polymers. Dyes are useful when seeking to observe nonluminescent CMOFs in situ by optical microscopy, while polymers are useful to tune their interparticle interactions. Third, we discuss criteria to assess the stability of CMOFs for various applications. In another section of this Account, we give examples of supracrystal assembly in liquid, on substrates, at interfaces, and under external electric fields. We end this Account with discussion of possible future developments, both conceptual and technological.

Mechanistic study of cationic dye interactions with clay‐polymer dispersions via metachromatic effect, aggregation, and surface charge

ABSTRACTInteractions for a series of aqueous dispersions of a clay, Laponite, and nonionic difunctional triblock copolymer, Pluronic L62, with two cationic dyes, crystal violet and brilliant green, are studied using UV–vis spectroscopy, dynamic light scattering (DLS), and electrophoretic mobility (EPM) to better understand the adsorption mechanisms. Different concentrations for clay, 0.1–2.0 g/L, mixed with polymer, 0.125–0.5 g/L to produce an organoclay, were tested with a fixed dye concentration, 2.0 × 10−5 mol/L. The aggregation states of the cationic dyes interacting with the clay–polymer dispersions were characterized by UV–vis absorbance. The dyes changed aggregation states from monomer to dimer and higher aggregate states upon addition to varying Laponite–polymer dispersion concentrations. DLS was used to understand the adsorbed polymer and dye interactions on the clay particle showing longer relaxation times for the largest aggregates observed from UV–vis absorbance. The EPM was used to characterize the surface charge of the clay relative to the polymer–dye interactions, which showed that the surface charge approached zero as the dyes interacted with clay–polymer dispersions. The most significant changes occurred with a reduction in light scattering intensity and longer relaxation decay at 0.1 g/L Laponite and 0.5 g/L Pluronic L62 concentrations in the presence of cationic dyes. The study of the clay–polymer–dye interactions help to better understand and design chemical templates for removal of contaminates in waste‐water treatment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40141.

Influence of an electric field on photodegradation and self-healing in disperse orange 11 dye-doped PMMA thin films

The influence of an applied electric field on reversible photodegradation of disperse orange 11 (DO11) doped into PMMA is measured using digital imaging and conductivity measurements. Correlations between optical imaging, which measures photodegradation and recovery, and photoconductivity enables an association to be made between the damaged fragments and their contribution to current, thus establishing that damaged fragments are charged species, or polarizable. Hence, the decay and recovery process should be controllable with the applications of an electric field. Indeed, we find that the dye polymer system is highly sensitive to an applied electric field, which drastically affects the decay and recovery dynamics. We demonstrate accelerated recovery when one field polarity is applied during burning, and the opposite polarity is applied during recovery. This work suggests that the damage threshold can be increased through electric field conditioning; and, the results are qualitatively consistent with the domain model of Ramini[3, 4]. The observed behavior will provide useful input into better understanding the nature of the domains in the domain model, making it possible to design more robust materials using common polymers and molecular dopants.

Synthesis of cationic polymeric adsorbent and dye removal isotherm, kinetic and thermodynamic

Poly(quaternary ammonium salt) (PQAS) as a cationic polymeric adsorbent was synthesized and characterized by FTIR. Isotherm, kinetic and thermodynamic of dye removal from single and binary systems was investigated. Acid Blue 25 (AB25) and Acid Red 18 (AR18) were used. The effect of operational parameters (adsorbent dose, pH, dye concentration and salt) on dye removal was studied. The dye removal followed the Langmuir isotherm and pseudo-first order kinetics. The adsorbent maximum dye adsorption capacity (Q0) was 2000 and 1667mg/g for AB25 and AR18, respectively. The thermodynamic data showed that dye adsorption was spontaneous, endothermic, and a physisorption reaction.