Fatty Acid Conjugates of Toluidine Blue O as Amphiphilic Photosensitizers: Synthesis,Solubility, Photophysics and Photochemical Properties†

Toluidine blue O (TBO) is a water‐soluble photosensitizer that has been used in photodynamic antimicrobial and anticancer treatments, but suffers from limited solubility in hydrophobic media. In an effort to incrementally increase TBO’s hydrophobicity, we describe the synthesis of hexanoic (TBOC6) and myristic (TBOC14) fatty acid derivatives of TBO formed in low to moderate percent yields by condensation with the free amine site. Covalently linking 6 and 14 carbon chains led to modifications of not only TBO’s solubility, but also its photophysical and photochemical properties. TBOC6 and TBOC14 derivatives were more soluble in organic solvents and showed hypsochromic shifts in their absorption and emission bands. The solubility in phosphate buffer solution was low for both TBOC6 and TBOC14, but unexpectedly slightly greater in the latter. Both TBOC6 and TBOC14 showed decreased triplet excited‐state lifetimes and singlet oxygen quantum yields in acetonitrile, which was attributed to heightened aggregation of these conjugates particularly at high concentrations due to the hydrophobic “tails.” While in diluted aqueous buffer solution, indirect measurements showed similar efficiency in singlet oxygen generation for TBOC14 compared to TBO. This work demonstrates a facile synthesis of fatty acid TBO derivatives leading to amphiphilic compounds with a delocalized cationic “head” group and hydrophobic “tails” for potential to accumulate into biological membranes or membrane/aqueous interfaces in PDT applications.     

Optimal yield in certain continuous chemical reactions

In this paper a consecutive chemical reaction of type A ? B ? C is considered where source A is turned to a product B in a catalytic reaction, and B is decomposed to C at the same time. Suppose that A can be supplied in a constant source concentration and B and C can be removed continuously. This continuous extraction process is modelled by means of partial differential equations and optimal yield of B is compared for different modelling assumptions. The complexity of the reaction models considered is increasing along the paper, starting from a simple flow model, to a percolation model and a transversal flow model describing the kinetics of a continuously operated flow reactor. It is shown that the efficiency of the reaction theoretically can be brought up arbitrary close to 1.     

Linearizing non-linear inverse problems and an application to inverse backscattering

We propose an abstract approach to prove local uniqueness and conditional Hölder stability to non-linear inverse problems by linearization. The main condition is that, in addition to the injectivity of the linearization A, we need a stability estimate for A as well. That condition is satisfied in particular, if A^∗A is an elliptic pseudo-differential operator. We apply this scheme to show uniqueness and Hölder stability for the inverse backscattering problem for the acoustic equation near a constant sound speed.     

Trapping of a Thiolate→Dibromine Charge‐Transfer Adduct by a Macrocyclic Dinickel Complex and Its Conversion into an Arenesulfenyl Bromide Derivative

Stuck on sulfur : The first transition‐metal complexes with S? Br units are surprisingly stable. Solid 3 is stable for at least six months and under vacuum solid 2 does not lose Br₂. The formation of the first structurally characterized transition‐metal arenesulfenyl bromide complex 3 occurs with a change of the spin ground state from S=2 to S=0.

     

On travelling-wave solutions for a moving boundary problem of Hele-Shaw type

We discuss a 2D moving boundary problem for the Laplacian withRobin boundary conditions in an exterior domain. It arises asa model for Hele–Shaw flow of a bubble with kinetic undercoolingregularization and is also discussed in the context of modelsfor electrical streamer discharges. The corresponding evolutionequation is given by a degenerate, non-linear transport problemwith non-local lower-order dependence. We identify the localstructure of the set of travelling-wave solutions in the vicinityof trivial (circular) ones. We find that there is a unique non-trivialtravelling wave for each velocity near the trivial one. Therefore,the trivial solutions are unstable in a comoving frame. Thedegeneracy of our problem is reflected in a loss of regularityin the estimates for the linearization. Moreover, there is anupper bound for the regularity of its solutions. To prove ourresults, we use a quasi-linearization by differentiation, indexresults for degenerate ordinary differential operators on thecircle and perturbation arguments for unbounded Fredholm operators.     

Existence,uniqueness and regularity of the projection onto differentiable manifolds

Annals of Global Analysis and Geometry - We investigate the maximal open domain $${\mathscr {E}}(M)$$ on which the orthogonal projection map p onto a subset $$M\subseteq {{\mathbb {R}}}^d$$ can be...     

Influence of molecular weight on selective oligomer-assisted dispersion of single-walled carbon nanotubes and subsequent polymer exchange

A series of oligofluorenes was synthesized and used as a SWNT selecting template to study the chain length effect on SWNTs dispersions in toluene. The octamer exhibits the same selectivity as the corresponding polymer. Nevertheless, SWNT/oligomer complexes are unstable, which allows fast exchange of the oligomer with a coating polymer.     

Photovoltaic characteristics and dye regeneration kinetics in D149-sensitized ZnO with varied dye loading and film thickness

Porous ZnO electrodes on fluorine-doped tin oxide (FTO) were prepared by electrochemical deposition from an O(2)-saturated ZnCl(2) solution in the presence of eosin Y as a structure directing agent (SDA). Sensitization was reached by desorption of the SDA and subsequent adsorption of the indoline dye D149. The influence of film thickness and dye concentration in the films on their photovoltaic characteristics, recombination, and dye regeneration kinetics was investigated. The recombination kinetics was analyzed by time-resolved photovoltage measurements. The dye regeneration by iodide ions in the electrolyte was investigated using scanning electrochemical microscopy (SECM) feedback mode approach curves. Analysis of a SECM kinetic model shows strongly different effective D149 regeneration rate constants k'(ox) for D149-ZnO electrodes of systematically varied film thickness and dye loading. It was found that the short-circuit current density J(sc) and k'(ox) correlated directly with the adsorbed dye concentration. k'(ox) was found to be independent of the dye loading but correlated strongly with the dye concentration in the film or inversely with the film thickness. Furthermore, we discussed the perspective of correlating macroscopic cell characteristics with SECM kinetics data.