Inkjet-printed thiol self-assembled monolayer structures on gold: quality control and microarray electrode fabrication

Laterally structured, self-assembled monolayers (SAMs) of different thiols (HS-R-X, R = (CH 2) 3-16, X = -CH 3, -COOH, -NH 2) on gold have been prepared by inkjet printing. The printer is a modified, low-cost desktop printer (Epson Stylus Photo R200), the ink is a 1 mM solution of the thiol in ethanol/glycerol (6:1). The quality of inkjet-printed large area SAMs obtained in this study is between that of a layer self-assembled from a thiol solution and that obtained by soft lithography, according to cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy (SECM), and polarization-modulated Fourier transform infrared reflection-absorption spectroscopy (PM IRRAS). For the first time, simultaneous printing of two different thiols in a single print job as an alternative to sequential printing and backfilling is demonstrated. The smallest structures consisting of conductive disks of 40 microm diameter were analyzed as single spots by SECM and as random array electrodes with different average disk-disk distance. Conductive band electrodes with variable bandwidth (300 microm to 1 cm) are presented, as well as a pH switchable band structure. As compared to stamping, inkjet printing allows for simultaneous multiple thiol printing in a single print job with the resolution limited only by the droplet size and the precision of the translation stage.     

Hydrogen-bond acceptance of bifunctional ligands in an alkyne-metal pi complex

Experiment and theory have been used to study reactive alkyne pi complexes, intermediates in anti-Markovnikov alkyne hydration by CpRu bis(phosphine) catalysts with heterocyclic substituents. Each heterocycle accepts a hydrogen bond from an acetylene C-H, as revealed by NMR coupling constants between alkyne 13C and 1H nuclei as well as between alkyne 13C and pyridine 15N (2hJCN). Moreover, further alkyne transformations occur at temperatures from 50 to 90 degrees C below what is needed to convert a control compound without the heterocycles.     

Synthesis of highly phenylene substituted p-phenylene oligomers from pyrylium salts

A transition metal free route to phenyl substituted oligophenylenes that tolerates halogens is described.     

Photophysics and deactivation pathways of thymine

Combined complete active space perturbation theory (CASPT2) and multireference configuration interaction calculations with single and double excitations (MR-CISD) were performed in order to explore possible deactivation pathways of thymine after photoexcitation. Equilibrium geometries are reported together with a total of eight extremes (minima or maxima) on the crossing seam (MXS), through which such radiationless transitions may occur. Furthermore, conformational analysis allows grouping these conical intersections in five distinct types. Reaction paths were calculated connecting the S1 (1)n pi* minimum with the lowest-energy MXS of each group. Two distinct types of paths were observed, both with features that should delay the internal conversion to the ground state. This is shown to provide a possible explanation for the relatively long excited-state lifetime of thymine.     

Scanning electrochemical microscopy study of laccase within a sol-gel processed silicate film

The enzyme p-diphenol:dioxygen oxidoreductase (laccase, EC 1.10.3.2) was isolated from Cerrena unicolor fungus and embedded in a sol-gel film obtained by acidic condensation of TMOS. The gel was cast to thin films on glass. The laccase-containing silicate films were inspected by confocal laser scanning microscopy (CLSM), scanning force microscopy (SFM) and scanning electrochemical microscopy (SECM). CLSM images in the reflection mode showed aggregates within the silicate films. SECM images in the substrate-generation/tip-collection mode using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as electron donor for laccase showed that the position of aggregates coincides with increased enzymatic activity within the silicate film. The flux from individual aggregates was detected. SECM images in the redox competition mode confirmed the assignment and could exclude that topographic features observed by CLSM and SFM could be the reason for the image contrast. SFM images showed that the aggregates partially dissolve during prolonged exposure to aqueous buffer. The experimental setup allowed following one individual aggregate over time with all three microscopic techniques which enabled the collection of complementing information on morphology and catalytic activity as well as their development over time.     

Tight focusing of radially polarized Gaussian and Bessel-Gauss beams

We examine the effects of tightly focusing a radially polarized beam with uniform, Gaussian, or Bessel-Gauss pupil functions. The resulting FWHM is smallest for the case of a uniform amplitude profile, while the Bessel-Gauss beam results in the largest FWHM. The uniform amplitude profile also results in an axial field component that increases fastest with increasing NA. The ratio of the axial component to the transverse component is also the greatest for the uniform pupil function. On the other hand, the Bessel-Gauss beam benefits the most from the use of an annulus.     

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.