Tailoring the interface using thiophene small molecules in TiO(2)/P3HT hybrid solar cells

In this paper we focus on the effect of carboxylated thiophene small molecules as interface modifiers in TiO(2)/P3HT hybrid solar cells. Our results show that small differences in the chemical structure of these molecules, for example, the presence of the -CH(2)- group in the 2-thiopheneacetic acid (TAA), can greatly increase the TiO(2) surface wettability, improving the TiO(2)/polymer contact. This effect is important to enhance exciton splitting and charge separation.     

H2-O2 atmosphere increases the activity of Pt/TiO2 for benzene photocatalytic oxidation by two orders of magnitude

Unprecedented photocatalytic activity and durability of Pt/TiO(2) for decomposing persistent organic pollutants (e.g. benzene) have been obtained by adding trace H(2) into an O(2)-rich photooxidation system.     

Tailoring the interfacial assembly of colloidal particles by engineering the mechanical properties of the interface

Fluid interfaces can be used as a platform for promoting the direct and spontaneous self-assembly of colloidal particles, where the driving force is the reduction in interfacial energy. In addition, fluid interfaces allow fine-tuning of the particles ensemble by an external force, such as the presence of an imposed interfacial flow, or by engineering the interparticle interactions dictated by the interplay of interfacial forces. As a consequence, a wide-ranging set of interfacial structures can be achieved from liquid-like layers, which can flow under stress, to amorphous solids that are able to sustain static stress. Here, far from a comprehensive overview of the interfacial assembly of colloidal particles, different ways of tailoring it by rationally designing the rheological properties of the interface are provided, with a focus on experimental and theoretical methods and model systems that have been recently exploited. In particular, ligand-coated nanoparticles, with a strong emphasis on the effect of the ligands on the interfacial structure and the rheological properties, and soft nanogel particles, in which an environmental factor, such as the temperature, drives to different interfacial structures and mechanical responses will be further discussed.     

Polythiophene containing thermally removable solubilizing groups enhances the interface and the performance of polymer-titania hybrid solar cells

A polythiophene derivative containing thermally removable branched ester solubilizing groups has been prepared and tested as a processable organic semiconductor polymer with tunable electronic and chemical properties for hybrid polymer-inorganic solar cells. Thermal removal of the protecting group enhances the interface between the organic and inorganic components while also contributing to better light absorption, energy transfer, and overall cell performance.     

Mass transfer from a moving interface of two immiscible fluids in laminar countercurrent flow between parallel plates

The effect of a moving interface on the mass transfer rate in one of two immiscible fluids in laminar countercurrent flow between parallel flat plates was studied theoretically. An approximate analytical solution for the average Sherwood number was obtained in terms of the confluent hypergeometric functions as a function of the Graetz number and the dimensionless interfacial fluid velocity.     

Mode of interaction of two fluorinated-hydrogenated hybrid amphiphiles with dipalmitoylphosphatidylcholine (DPPC) at the air-water interface

Two-component Langmuir monolayers formed on 0.02M Tris buffer solution (pH 7.4) with 0.13M NaCl at 298.2K were investigated for two different fluorinated-hydrogenated hybrid amphiphiles (F6PH5PPhNa and F8PH5PPhNa or F6 and F8, respectively) with DPPC. Surface pressure (pi), surface potential (DeltaV) and dipole moment (mu( perpendicular)) as a function of molecular surface area (A) were measured by employing the Whilhelmy method and an ionizing electrode method. From the A- and DeltaV-X(F6) (or X(F8)) curves, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined as a function of surface mole fraction (X(Fn)) at discrete surface pressures. Then, the behavior of occupied surface areas and surface potentials of the respective components could be made clearer. Compressibility (C(s)), elasticity (C(s)(-1)), and excess Gibbs energy (DeltaG((ex))) as a function of X(F6) (or X(F8)) were estimated at definite pressures. These physico-chemical parameters were found to reflect the mechanical strength of monolayer films formed. The regular solution theory being applied to DeltaG((ex)), the activity coefficients (f) as well as the interaction parameter (I(p)) between DPPC and two hybrid amphiphiles in the binary monolayers were evaluated. I(p) values thus obtained indicated that F8 molecules interact more strongly with DPPC molecules than F6. Moreover, in order to better understand the morphological monolayer state, Langmuir-Blodgett (LB) films made from DPPC and fluorinated-hydrogenated hybrid amphiphiles were examined by atomic force microscopy (AFM). The miscibility of the two components in the monolayer state is evidenced by these thermodynamic quantities and AFM observations. Furthermore, AFM images demonstrated that F8 could more effectively disperse the ordered domains of DPPC than F6.     

Recent advances in the determination of enantiomeric drugs and their metabolites in biological fluids by capillary electrophoresis-mediated microanalysis

This review summarizes the recent developments in the application of electromigration techniques for the enantioselective analysis of drugs and metabolites in biological fluids. During the period covered by this review, it has been observed an increase in the use of negatively charged chiral selectors, particularly sulfobutyl ether-beta-cyclodextrin and sulfated-beta-cyclodextrin, and the combination of two different chiral selectors in the running buffer to obtain the resolution of drugs and their metabolites. Low detection limits as required for pharmacokinetic studies were obtained by using concentration techniques, including sample stacking procedures, and more sensitive detection systems, such as laser-induced fluorescence and mass spectrometry. Finally, the major points are discussed that can be considered to obtain reliable methods for enantioselective bioanalysis.     

Study of ionic liquids by the method of voltammetry at the interface between two immiscible electrolytes

Ionic liquids were studied as the organic phase in the method of voltammetry between two immiscible electrolytes. The polarization of the interface between ionic liquid and water was studied; the dependence of the polarization range (potential window) on the solubility of ionic liquid in water was shown. It was established that the interface between H₂O and ionic liquid based on hydrophobic substituted phosphonium cation and tris(pentafluoroethyl)-trifluorophosphate anion is polarized in the range of potential of about 500 mV, which creates the possibility of determining the concentration of some union, in particular perchlorate and nitrate, even in when they are both present, as well as to measure the solubility of more hydrophilic ionic liquids in water.     

Size-selective voltammetry: modification of the interface between two immiscible electrolyte solutions by zeolite Y

Size- and charge-selective ion transfer across the zeolite-Y-modified interface between two immiscible electrolyte solutions (ZM-ITIES) is described. The zeolite-Y membrane is prepared from pressed disks by healing with tetraethyl orthosilicate (TEOS). Size- and charge-selective transfer of the tetraethylammonium cation, size-selective exclusion of tetrabutylammonium cation, and charge-selective exclusion of the tetrafluoroborate and perchlorate anions are demonstrated at the ZM-ITIES. The exclusion studies suggest that the membrane is coherent and contains a low density of pinholes, after healing with TEOS. Various factors affecting the ion transfer such as analyte concentration, supporting electrolyte concentration, and scan rate are investigated. The diffusion coefficient of tetraethylammonium ions within the zeolite-Y pores is found to be on the order of 10(-8) cm2 s(-1).     

Calculating the hopping times of confined fluids: two hard disks in a box

The dynamical transition between the anomalous single file diffusion of highly confined fluids and bulk normal diffusion can be described by a phenomenological model involving a particle hopping time tau(hop). We suggest a theoretical formalism that will be useful for the calculation of tau(hop) for a variety of systems and test it using a simple model consisting of two hard disks confined to a rectangular box with hard walls. In the case where the particles are moving diffusively, we find the hopping time diverges as a power law in the threshold region with an exponent of -(3/2). Under conditions where the particles move inertially, transition state theory predicts a power law behavior with an exponent of -2. Molecular dynamics simulations confirm the transition state theory result for inertial dynamics, while Brownian dynamics simulations suggest the scaling exponent is highly sensitive to the details of the algorithm.     

Electrolysis at the interface between two immiscible electrolyte solutions by means of a hanging electrolyte drop electrode

A three-electrode system with a hanging electrolyte drop electrode is described. The system facilitates analytical exploitation of electrolysis at the interface between two immiscible electrolyte solutions. Its use is demonstrated for the determination of micromolar concentrations of tetraethylammonium cation by differential pulse stripping voltammetry, based on transfer of the cation from water to nitrobenzene.     

Assessing the quality of raw cotton knitted fabrics by their streaming potential coefficients

Raw cotton knitted fabrics of Greek, Indonesian, and Indian origin were investigated through surface characterization before and after processing. Surface modifications of all the knitted cotton fabrics were objectively evaluated through zeta potential measurements within a range of the electrolyte solution pHs, and swelling over time. Streaming potential coefficients of different cotton knitted fabrics were applied in order to establish a correlation between the properties of the raw and treated cotton knitted fabrics of different origins. The rate of swelling was calculated from the streaming potential coefficients of the raw knitted fabrics before and after different treatments. Swelling rate for different origins and different treatments of cotton knitted fabrics and the correlation coefficients were obtained using linear regression. Additionally, a data cluster analysis was performed in order to group different origins of cotton, while all the treatments were sorted according to zeta potential and the rate of swelling coefficients. The obtained results showed differences among the clusters, depending on the origin of the cotton knitted fabrics and treatments they were exposed to.     

Simultaneous quantitation of phenobarbitone and p-hydroxyphenobarbitone and their perdeuteroethyl analogues in biological fluids by combined gas chromatography-mass spectrometry

In order to develop 5-pentadeuteroethyl-5-phenyl barbituric acid as an alternative tracer in pharmacokinetic and metabolic studies of phenobarbitone, and to search for possible isotope effects associated with such labelling, we propose a gas chromatographic-mass spectrometric assay for simultaneous measurement of phenobarbitone, p-hydroxyphenobarbitone and their perdeuteroethyl analogues, using [1,3-15N2,2-13C] phenobarbitone as internal standard. These compounds were extracted from plasma (50 microliter) or urine (500 microliter) and pentylated according to Greeley's method. Linear calibration curves were obtained in the concentration range from 0.5 to 3 micrograms/ml. The interday precision, mean accuracy and detection limit were 0.77-5.28%, 99.99-100.80% and 0.03-0.05 microgram/ml, respectively. Results for plasma and urine concentrations, and pharmacokinetic parameters in humans, are presented to illustrate this method.     

Stability of the interface between two dynamic phases in capillary flow of linear polymer melts

Results of previous work¹ on a theoretical explanation of the “spurt effect” in polymer melt flow are extended. A modified Doi—Edwards liquid is shown to support axisymmetric traveling waves on an interface between high and low shear-rate phases in capillary flow. The stability of these perturbations is found to be governed by normal stress effects and may be related to certain types of melt fracture. Observed effects of varying the capillary length are explained qualitatively.     

Determination of diphenylmethane antihistaminic drugs and their analogues in body fluids by gas chromatography with surface ionization detection.

Eleven diphenylmethane antihistaminic drugs and their analogues were tested for their detection by capillary gas chromatography (GC) with surface ionization detection (SID). The GC-SID response was highest for doxylamine, diphenhydramine and orphenadrine and lowest for terodiline, clemastine and pipethanate. The detection limits for drugs with the highest response were 2-5 pg (ca. 6-20 fmol) on-column (100-250 pg/ml of body fluid). The detection limits with GC-SID were 10-100 times higher than those with GC with nitrogen-phosphorus detection. A detailed procedure for the isolation of the antihistaminics from human whole blood and urine by the use of Sep-Pak C18 cartridges, prior to GC-SID, is also presented. The recoveries of the drugs (50 or 500 pmol), which had been added to 1 ml of body fluids, were > 60%. The baselines remained steady as the column temperature was increased and the background was clean, especially for whole blood extracts.     

Derivative spectrophotometric analysis of 4-quinolone antibacterials in formulations and spiked biological fluids by their Cu(II) complexes

A derivative UV-spectrophotometric analytical procedure was developed for determination of three 4-quinolone antibacterials: norfloxacin (NFX), ciprofloxacin (CFX), and sparfloxacin (SFX). The method depends on the complexation of Cu(II) with the studied compounds in aqueous medium. A third order, measurement was applied for their quantification. A linear correlation was established between the amplitude of the peak and concentration for all the studied drugs in the range of 15-80, 35-120, and 200-700 ng/mL, with minimum detectability (S/N = 2) of 1.0, 1.3, and 5.1 ng/mL for NFX, CFX, and SFX, respectively. The method was successfully applied for accurate, sensitive, and selective determination of the studied drugs in bulk and tablets formulation with average percentage recoveries of 99.22 +/- 0.55 to 100.33 +/- 1.60. The results obtained were favorably compared with those of the reference method. The method was also used to determine sparfloxacin in spiked human plasma and urine. The results obtained were satisfactory, accurate, and precise.