Preparation of Porous Polymer Networks of <Emphasis Type="Italic">N</Emphasis>-Vinylpyrrolidone with Triethylene Glycol Dimethacrylate and Determination of Their Specific Surface Area Using Rose Bengal Dye

Porous polymer networks of N-vinylpyrrolidone with triethylene glycol dimethacrylate were prepared by three-dimensional radical copolymerization using template approach based on incorporation of macromolecular nanoobjects with porogen function. The adsorption of Rose Bengal dye from aqueous solutions onto the copolymers prepared and its desorption were studied by electronic absorption spectroscopy. The specific surface area of the porous polymer networks was estimated from the Rose Bengal adsorption data. The porous polymer networks adsorb riboflavin from aqueous solution. The riboflavin desorption is characterized by complex pattern due to washout from pores of different size.     

Dye Binding Characteristics of N,N′‐Methylene‐bis‐acrylamide (NNMBA)‐Crosslinked Polyacrylamide‐Supported Amine and its Photooxidizing Ability

The dye binding characteristics of 8 mol% NNMBA‐crosslinked polyacrylamide‐supported amine is investigated with Rose Bengal (RB), Methyl Orange (MO), Methylene Blue (MB) and Methyl Red (MR). The influence of the concentration of dye solution on dye binding, time course of dye binding and characterization were explored. It is observed that binding is higher in the case of Rose Bengal and dye binding depends on the polarity, as well as the size of the dye molecule. The photooxidation property of polymer bound RB was investigated towards the oxidation of benzoin to benzil. RB bound polymer acts as an efficient heterogenous photooxidizing agent.     

Effect of molecular interactions on the photophysics of Rose Bengal in polyelectrolyte solutions and self-assembled thin films

Solutions and layer-by-layer self-assembled thin films containing Rose Bengal and poly(diallyldimethylammonium chloride) are studied with the aim of understanding the interactions controlling their structures and the photophysics of the dye in both media. A detailed spectroscopic and theoretical analysis shows that hydrophobic interactions among dye molecules contribute to the coiling of the polyelectrolyte chain in solution at low polyelectrolyte/dye ( P/ D) ratios, whereas extensive aggregation of the dye takes place even at ratios as high as 10(4) (expressed in monomeric units). A polyelectrolyte elongated form prevails in self-assembled thin films, providing an environment that reduces hydrophobic interactions and lowers the aggregation tendency. Self-assembled films with a roughly estimated overall dye concentration around 1 M at a P/ D ratio in the order of seven are fluorescent and photogenerate singlet molecular oxygen. This contrasts with the behavior of polyelectrolyte solutions, which are almost nonfluorescent and do not evidence triplet state generation at the same P/ D ratio.     

Site-directed photochemical disruption of the actin cytoskeleton by actin-binding Rose Bengal-conjugates

The in situ light-induced, non-enzymatic digestion of cytoskeletal actin by a xanthene dye conjugated to heavy meromyosin, anti-actin antibodies and/or anti-myosin antibodies is reported. The dye Rose Bengal was conjugated to either anti-actin antibodies, anti-myosin antibodies or heavy meromyosin. Under our experimental conditions, visible light induced the non-enzymatic breakdown of cytoskeletal actin when mammalian tissue culture cells were probed either with Rose Bengal-conjugated anti-actin and/or anti-myosin antibodies. Similar results were obtained when tissue culture cells were probed with Rose Bengal-conjugated heavy meromyosin before irradiation with visible light. The in situ photochemical reaction depended on the presence of actin-binding Rose Bengal-conjugates.     

Metal-free visible-light-promoted intermolecular [2+2]-cycloaddition of 3-ylideneoxindoles

The Rose Bengal sensitized intermolecular [2 + 2]-cycloaddition of 3-ylideneoxindoles for the synthesis of spirocyclic oxindoles was developed successfully under visible light irradiation conditions. The cycloaddition products were obtained in good yields (up to 93%) with excellent diastereoselectivity and regioselectivity by using a low loading of Rose Bengal (0.125 mol%) as a triplet sensitizer. This work demonstrates the potential benefits of Rose Bengal in visible light catalysis.     

Charge transport versus recombination in dye-sensitized solar cells employing nanocrystalline TiO2 and SnO2 films

We report a comparison of charge transport and recombination dynamics in dye-sensitized solar cells (DSSCs) employing nanocrystalline TiO(2) and SnO(2) films and address the impact of these dynamics upon photovoltaic device efficiency. Transient photovoltage studies of electron transport in the metal oxide film are correlated with transient absorption studies of electron recombination with both oxidized sensitizer dyes and the redox couple. For all three processes, the dynamics are observed to be 2-3 orders of magnitude faster for the SnO(2) electrode. The origins of these faster dynamics are addressed by studies correlating the electron recombination dynamics to dye cations with chronoamperometric studies of film electron density. These studies indicate that the faster recombination dynamics for the SnO(2) electrodes result both from a 100-fold higher electron diffusion constant at matched electron densities, consistent with a lower trap density for this metal oxide relative to TiO(2), and from a 300 mV positive shift of the SnO(2) conduction band/trap states density of states relative to TiO(2). The faster recombination to the redox couple results in an increased dark current for DSSCs employing SnO(2) films, limiting the device open-circuit voltage. The faster recombination dynamics to the dye cation result in a significant reduction in the efficiency of regeneration of the dye ground state by the redox couple, as confirmed by transient absorption studies of this reaction, and in a loss of device short-circuit current and fill factor. The importance of this loss pathway was confirmed by nonideal diode equation analyses of device current-voltage data. The addition of MgO blocking layers is shown to be effective at reducing recombination losses to the redox electrolyte but is found to be unable to retard recombination dynamics to the dye cation sufficiently to allow efficient dye regeneration without resulting in concomitant losses of electron injection efficiency. We conclude that such a large acceleration of electron dynamics within the metal oxide films of DSSCs may in general be detrimental to device efficiency due to the limited rate of dye regeneration by the redox couple and discuss the implications of this conclusion for strategies to optimize device performance.     

PHOTODYNAMIC INACTIVATION OF AN ION CHANNEL: GRAMICIDIN A

The ion channel formed by the peptide gramicidin A in planar lipid membranes is inactivated by visible light in the presence of the photosensitizer Rose Bengal. This is concluded from the strong decrease of the membrane conductance by more than two orders of magnitude. Experiments performed at different oxygen concentrations, in the presence of the singlet oxygen quenchers beta-carotene or alpha-tocopherol indicate, that presumably a type I process between the dye Rose Bengal and the tryptophan residues of the gramicidin channel with a subsequent oxidation of the tryptophans is responsible for the loss of the conductance properties of the channel.     

Metal-free photo-induced radical C-P and C-S bond formation for the synthesis of 2-phosphoryl benzothiazoles

We reveal here a visible-light promoted phosphorylation of 2-isocyanoaryl thioethers for the first time with concomitant C(sp³)-S bond cleavage and imidoyl C–S formation. Additionally, this method features the use of 3 mol% organic dye Rose Bengal as the photocatalyst without external transition-metal or peroxide oxidants, and provides a novel and environmentally friendly approach for the preparation of a variety of 2-phosphoryl benzothiazoles in moderate to good yields.     

SnO2-TiO2复合颗粒的形态结构及其光催化活性

在气溶胶反应器中,利用TiCl4高温氧化反应制备超细TiO2,采用均匀沉淀法在TiO2表面沉积SnO2,制备SnO2-TiO2复合颗粒,应用TEM、EDS、XRD、BET比表面积测试等手段对粒子进行表征。以活性艳红X-3B溶液为处理对象,考察复合颗粒的光催化活性。结果表明SnO2-TiO2复合颗粒的光催化活性较纯气相合成超细TiO2有较大提高,SnO2最佳含量为15.3%,SnO2-TiO2复合颗粒光催化活性的提高归因于不同能级半导体之间光生载流子的输运和分离。     

LONG-RANGE TRIPLET-SINGLET ENERGY TRANSFER FROM ENZYME GENERATED TRIPLET ACETONE TO XANTHENE DYES

Enzyme-generated and protected acetone transfers its energy to xanthene dyes by a nontrivial process. The relative populations of the S₁ state are indicative of the operation of a heavy atom effect, being 1:15:100 for fluorescein, eosine and Rose Bengal. On the other hand Stern-Volmer constants and k _ET⁰ values are similar for the three dyes and are remarkably higher than for collisional processes.
It is tentatively suggested that at least for eosine and Rose Bengal, a triplet-triplet cxciton transfer may occur to populate an upper triplet state of the dye followed by heavy-atom enhanced intersystem crossing to the S₁ state.     

New benchmark for water photooxidation by nanostructured alpha-Fe2O3 films

Thin films of silicon-doped Fe2O3 were deposited by APCVD (atmospheric pressure chemical vapor deposition) from Fe(CO)5 and TEOS (tetraethoxysilane) on SnO2-coated glass at 415 degrees C. HRSEM reveals a highly developed dendritic nanostructure of 500 nm thickness having a feature size of only 10-20 nm at the surface. Real surface area determination by dye adsorption yields a roughness factor of 21. XRD shows the films to be pure hematite with strong preferential orientation of the [110] axis vertical to the substrate, induced by silicon doping. Under illumination in 1 M NaOH, water is oxidized at the Fe2O3 electrode with higher efficiency (IPCE = 42% at 370 nm and 2.2 mA/cm2 in AM 1.5 G sunlight of 1000 W/m2 at 1.23 VRHE) than at the best reported single crystalline Fe2O3 electrodes. This unprecedented efficiency is in part attributed to the dendritic nanostructure which minimizes the distance photogenerated holes have to diffuse to reach the Fe2O3/electrolyte interface while still allowing efficient light absorption. Part of the gain in efficiency is obtained by depositing a thin insulating SiO2 interfacial layer between the SnO2 substrate and the Fe2O3 film and a catalytic cobalt monolayer on the Fe2O3 surface. A mechanistic model for water photooxidation is presented, involving stepwise accumulation of four holes by two vicinal iron or cobalt surface sites.     

Solvatochromic behavior on the absorption and fluorescence spectra of Rose Bengal dye in various solvents

The absorption and fluorescence spectra of Rose Bengal dye were studied in various solvents. It was found that solvent effects on the absorption wavelength are consistent with the solvatochromic model of Kamlet, Abboud and Taft. The solvent polarizability value pi* was found to have a linear relationship with the absorption wavelength of the dye in various solvents. Additionally, the normalized transition energy value (E(T)(N)) showed some scattering when plotted versus Deltanu(af). Density functional calculations were used to assign the absorption in the region 540-570 nm to a pi-pi* transition between the HOMO and LUMO of the anion. Experimental ground state and excited state dipole moments were calculated by using the solvatochromatic shifts of absorption and fluorescence spectra as a function of the dielectric constant (epsilon) and refractive index (n). The dipole moment for Rose Bengal was found to be 1.72 Debye in the ground state, whereas this value was 2.33 Debye in the excited state.     

Morphological and photoelectrochemical characterization of core-shell nanoparticle films for dye-sensitized solar cells: Zn-O type shell on SnO2 and TiO2 cores

Core-shell type nanoparticles with SnO2 and TiO2 cores and zinc oxide shells were prepared and characterized by surface sensitive techniques. The influence of the structure of the ZnO shell and the morphology ofnanoparticle films on the performance was evaluated. X-ray absorption near-edge structure and extended X-ray absorption fine structure studies show the presence of thin ZnO-like shells around the nanoparticles at low Zn levels. In the case of SnO2 cores, ZnO nanocrystals are formed at high Zn/Sn ratios (ca. 0.5). Scanning electron microscopy studies show that Zn modification of SnO2 nanoparticles changes the film morphology from a compact mesoporous structure to a less dense macroporous structure. In contrast, Zn modification of TiO2 nanoparticles has no apparent influence on film morphology. For SnO2 cores, adding ZnO improves the solar cell efficiency by increasing light scattering and dye uptake and decreasing recombination. In contrast, adding a ZnO shell to the TiO2 core decreases the cell efficiency, largely owing to a loss of photocurrent resulting from slow electron transport associated with the buildup of the ZnO surface layer.     

Metal and acid-free visible light-mediated Friedel-Crafts alkylation reactions of indole with anilines

Metal and acid-free visible light-induced Friedel-Crafts C3-alkylation reactions of indole derivatives were developed using N,N-dimethylanilines as the carbon source. A cheap and readily available organic dye, Rose Bengal, was applied as the photocatalyst. This environmentally friendly transformation afforded C3-alkylated indoles in moderate to good yields under mild conditions.     

SnO2-TiO2复合光催化剂的制备和性能

采用均匀沉淀法在超细TiO2表面包覆SnO2,制备出SnO2-TiO2复合光催化剂,并用EDS,XRD,TEM和BET比表面积测定等手段进行了表征.以活性艳红X-3B溶液为模拟废水,考察了SnO2-TiO2的光催化活性.结果表明,复合粒子由锐钛矿型TiO2和金红石型SnO2组成;与纯TiO2相比,SnO2-TiO2的光催化活性有较大提高,SnO2最佳包覆量为18.4%.复合光催化剂活性的提高归因于不同能级半导体之间光生载流子的输运和分离.     

IONIC STRENGTH EFFECTS ON THE GROUND STATE COMPLEXATION and TRIPLET STATE ELECTRON TRANSFER REACTION BETWEEN ROSE BENGAL and METHYL VIOLOGEN

Abstract— The equilibrium constants, K_c, for complexation between methyl viologen dication (MV²+) and Rose Bengal, or Eosin Y, decrease with increasing ionic strength. At zero ionic strength K_c is 6500 (± 500) mol^?1 dm³ for Rose Bengal and 3200 (± 200) mol^?1 dm³ for Eosin Y, and these values decrease to 1500 (± 100) and 680 (± 40) mol^?1 dm³, respectively, at an ionic strength of 0.1 mol dm^?3. K_c is independent of pH between 4.5 and 10. ΔH is -25 (± 1) kJ mol^?1 for complexation with either dye, whereas ΔS is -15 (± 3) J K^?1 mol^?1 for Rose Bengal, and - 23 (± 3) J K^?1 mol^?1 for Eosin Y. The complexation constant for Rose Bengal and the neutral viologen, 4,4'-bipyridinium-N, N'-di(propylsulphonate), (4,4'-BPS), is 420 (± 35) mol^?1 dm³, and independent of ionic strength. No complexation could be observed for either Rose Bengal or Eosin with another neutral viologen, 2,2'-bipyridinium-N,N'-di(propylsulphonate), (2,2'-BPS). MV²+ quenches the triplet state of Rose Bengal with a rate constant of 7 × 10⁹ mol^?1 dm³ s^?1, and this rate constant decreases slightly as ionic strength increases. The cage escape yield following quenching, Φ_cc is very low (Φ_cc= 0.02 (± 0.005), and independent of ionic strength. 4,4'-BPS quenches the triplet state of Rose Bengal with a rate constant of 2.2 (± 0.1) × 10⁹ mol^?1 dm³ s^?1, and gives a cage escape yield of 0.033 (± 0.006). 2,2'-BPS quenches the Rose Bengal triplet with a rate constant of 6 (± 1) × 10⁸ mol^?1 dm³ s^?1 and gives a cage escape yield of 0.07 (± 0.01). Conductivity measurements indicate that MV²+(Cl^?)₂ is completely dissociated at concentrations below 2 × 10^?2 mol dm^?3.     

离子液体AlCl3/Et3NHCl中电沉积法制备金属铝

在AlCl3/Et3NHCl型离子液体中铝电极上通过恒电位电解沉积制备出金属铝. 测定了不同摩尔比的AlCl3/Et3NHCl离子液体在不同温度下的电导率, 考察了离子液体AlCl3/Et3NHCl摩尔比为2/1中Al电极上铝沉积的晶核成核过程, 以及恒电位电解沉积铝的工艺条件对电流效率和沉积铝表面形貌的影响. 结果表明, 不同比例AlCl3/Et3NHCl离子液体的电导率随温度升高而升高, 符合Arrhenius规律; 在Al电极上铝沉积的成核机理为三维瞬时成核过程; 恒电位电解沉积结果表明, 室温下在电位-2.4 V(vs Pt)和电解时间20 min条件下, 沉积铝的表面形貌比较平整致密,电流效率达73%, 沉积铝的纯度达96%(w).     

Aluminum chloride as a solid is not a strong Lewis acid

Aluminum chloride is used extensively as Lewis acid catalyst in a variety of industrial processes, including Friedel-Crafts and Cl/F exchange reactions. There is a common misconception that pure AlCl3 is itself a Lewis acid. In the current study, we use experimental and computational methods to investigate the surface structure and catalytic properties of solid AlCl3. The catalytic activity of AlCl3 for two halide isomerization reactions is studied and compared with different AlF3 phases. It is shown that pure solid AlCl3 does not catalyze these reactions. The (001) surface of crystalline AlCl(3) is the natural cleavage plane and its structure is predicted via first principles calculations. The chlorine ions in the outermost layer of the material mask the Al3+ ions from the external gas phase. Hence, the experimentally found catalytic properties of pure solid AlCl3 are supported by the predicted surface structure of AlCl3.     

Activation of C-Cl by ground-state aluminum atoms: an EPR and DFT investigation

The reaction of ground-state Al atoms with dichloromethane (CH(2)Cl(2)) in an adamantane matrix at 77 K yielded two mononuclear Al species. The magnetic parameters, extracted from the axial EPR spectrum of Species A/A' (g(1) = 2.0037, g(2) = g(3) = 2.0030, a(Al,1) = 1307 MHz, a(Al,2) = a(Al,3) = 1273 MHz, a(35Cl) = 34 MHz and a(37Cl) = 28 MHz) were assigned to the Al-atom insertion product, ClCH(2)AlCl. Density functional theory (DFT) calculations of the values of the Al and Cl hyperfine interaction (hfi) of the Cl(1)-Cl(2)gauche conformer were in close agreement with the experimental values of ClCH(2)AlCl. The second species, B/B', had identical magnetic parameters to those of ClCH(2)AlCl with the exception that the Al hfi was 15% smaller. Coordination of a ligand, possessing a lone pair of electrons, to the Al atom of the insertion product, [ClCH(2)AlCl]:X, could cause the a(Al) to decrease by 15%. Alternatively, it is possible that the Cl(1)-Cl(2) anti conformer of ClCH(2)AlCl is also isolated in the matrix. Support for the spectral assignments is given by calculation of the nuclear hfi of [ClCH(2)AlCl]:H(2)O and the Cl(1)-Cl(2) anti conformer of ClCH(2)AlCl using a DFT method. The potential energy hypersurface for an Al atom approaching CH(2)Cl(2), calculated at the B3LYP level, suggests that Al atom abstraction of Cl forming AlCl and CH(2)Cl is favoured in the gas phase. When produced in a matrix, the close proximity of AlCl and CH(2)Cl could account for the formation of ClCH(2)AlCl. EPR evidence was also found for the formation of the CHCl(2) radical.     

Fullerene-containing N-vinylpyrrolidone copolymers as sorbents and polymeric containers for low-molecular-weight compounds

Branched copolymers of N-vinylpyrrolidone with triethylene glycol dimethacrylate, containing covalently bound fullerene, were synthesized, and their main physicochemical characteristics were determined. These copolymers show promise as sorbents and polymeric containers for low-molecular-weight compounds, as demonstrated by the example of a hydrophilic dye, Rose Bengal.