Substitution and condensation reactions with poly(anilineboronic acid): reactivity and characterization of thin films

Poly(anilineboronic acid) thin films are treated under various conditions to achieve substitution or condensation reactions involving the boronic acid moiety. These reactions are studied with polarization modulated infrared reflection absorption spectroscopy, cyclic voltammetry, and UV-vis spectroscopy. The results suggest the single-step formation of substituted polyanilines, such as poly(hydroxyaniline), halogenated polyanilines, and mercury chloride-substituted polyaniline. A condensation reaction of poly(anilineboronic acid) with cis-diol compounds in aqueous solution, as well as with phenylenebisboronic acid and salycilamide in THF, indicates the formation of boronic esters. The latter reactions appear to be a good entry point for the formation of complex or supramolecular polymer structures.     

Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate

An overoxidized polypyrrole colloid, which can recognise enantiomers of amino acids has been prepared by a newly developed molecular imprinting technique. A polypyrrole colloid, which had been polymerised from a mixture of pyrrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and L-lactate (dopant), was overoxidized to create a dopant-complementary cavity. The enantioselectivity of the overoxidized colloid was evaluated by comparing the uptake of L-alanine and L-cysteine with that of the respective D-enantiomers. The L/D uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantiomers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by L-lactate. In contrast, a colloid templated with L-phenyllactate took up L-phenylalanine with a higher enantioselectivity of about 7. A colloid templated with L-lactate was applied to surface chirality analysis through enantioselective adsorption on cysteine-modified gold surfaces. Quartz microbalance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surface modified with L-cysteine than to one modified with D-cysteine.     

β‐Functionalized meso Tetrahalothien‐2‐ylporphyrins: Synthesis,Spectral, and Electrochemical Properties

Two types of β‐ functionalized (mono nitrated and perbrominated) meso tetrakis(5‐halothien‐;2‐yl)porphyrins, which can be used as precursors for the synthesis of other asymmetric and highly substituted porphyrins, have been synthesised and characterized. Introduction of a nitro group at the β‐ position shifted soret band 11–16 nm to the red region and redox potentials to > 170 mV for oxidation and > 250 mV for reduction anodically. Perbromination of halothienylporphyrins lead to enhanced bathochromically shifted uv‐visible spectral bands, but had only marginal influence on oxidation potentials. Effect of mono nitro group and eight bromo groups on the electronic properties of the porphyrins is attributed, respectively to, the electron deficiency created in the porphyrin π‐ system and the nonplanar conformation induced by the bulky bromo groups.     

A Fixed Point Theorem in Intuitionistic Fuzzy Metric Spaces by Using New Commutativity Condition

We prove a common fixed point theorem for discontinuous,noncompatible mappings on noncomplete intuitionistic fuzzy metric spaces by using a new commutativity condition.We validate our main result by an example.     

Porous conducting polymer/heteropolyoxometalate hybrid material for electrochemical supercapacitor applications

A porous conducting polymer/heteropolyoxometalate hybrid material that displays high specific capacitance and low ionic resistance has been prepared for electrochemical supercapacitor applications. Polypyrrole/phosphomolybdate composite films were chemically synthesized in tetrahydrofuran in the presence of sodium sulfate, which acts as a porogen. While the phosphomolydic acid could be removed from the film upon rinsing with pure tetrahydrofuran or acetone, rinsing with water or methanol resulted in retention of the heteropolyoxometalate at a level high enough to easily observe its electrochemistry. The retained phosphomolybdate exhibits fast and reversible redox behavior, adding a significant amount of pseudocapacitance to the polymer. Porous films were obtained by leaching out the sodium sulfate porogen from the films using water. The morphology obtained using this method is altered by varying the monomer-to-porogen ratio. Increasing the porosity increases the rate at which the hybrid material can be charged/discharged (i.e., oxidized/reduced) by increasing the ionic conductivity and in turn lowering the resistor-capacitor time constant of the material. The ability to tune the porosity of the material allows the optimization of performance characteristics for use in supercapacitor applications. Impedance measurements indicate that the ionic conductivity of these porous structures can be increased more than an order of magnitude over that observed for standard conducting polymer films and that the hybrid material displays peak specific capacitance of around 700 F/g as well as excellent reversibility and cyclability.     

Synthesis,Spectral, and Electrochemical Properties of meso‐5,10,15,20‐Tetrakis (2′‐chlorobenzoquinolin‐3′‐yl)porphyrins

The synthesis, characterization, and redox and spectral properties of the meso‐5,10,15,20‐tetrakis(2′‐chlorobenzoquinolin‐3′‐yl)porphyrin are reported. The synthesis of the porphyrin was performed by following the modified Lindsey procedure, and its zinc(II) derivative was prepared by using the conventional method. The electronic properties of the compound were investigated by cyclic voltammetry and spectroscopy. This compound shows unusual redox behavior with difficulty in oxidation and ease of reduction compared to tetraphenylporphyrin.     

Wireless Coupling of Conducting Polymer Actuators with Light Emission

Combining the actuation of conducting polymers with additional functionalities is an interesting fundamental scientific challenge and increases their application potential. Herein we demonstrate the possibility of direct integration of a miniaturized light emitting diode (LED) in a polypyrrole (PPy) matrix in order to achieve simultaneous wireless actuation and light emission. A light emitting diode is used as a part of an electroactive surface on which electrochemical polymerization allows direct incorporation of the electronic device into the polymer. The resulting free-standing polymer/LED hybrid can be addressed by bipolar electrochemistry to trigger simultaneously oxidation and reduction reactions at its opposite extremities, leading to a controlled deformation and an electron flow through the integrated LED. Such a dual response in the form of actuation and light emission opens up interesting perspectives in the field of microrobotics.     

Designing tubular conducting polymer actuators for wireless electropumping

Rational design and shaping of soft smart materials offer potential applications that cannot be addressed with rigid systems. In particular, electroresponsive elastic materials are well-suited for developing original active devices, such as pumps and actuators. However, applying the electric stimulus requires usually a physical connection between the active part and a power supply. Here we report about the design of an electromechanical system based on conducting polymers, enabling the actuation of a wireless microfluidic pump. Using the electric field-induced asymmetric polarization of miniaturized polypyrrole tubes, it is possible to trigger simultaneously site-specific chemical reactions, leading to shrinking and swelling in aqueous solution without any physical connection to a power source. The complementary electrochemical reactions occurring at the opposite extremities of the tube result in a differential change of its diameter. In turn, this electromechanical deformation allows inducing highly controlled fluid dynamics. The performance of such a remotely triggered electrochemically active soft pump can be fine-tuned by optimizing the wall thickness, length and inner diameter of the material. The efficient and fast actuation of the polymer pump opens up new opportunities for actuators in the field of fluidic or microfluidic devices, such as controlled drug release, artificial organs and bioinspired actuators.

Tubular conducting polymer actuators are used for developing a wireless electropumping device. Bipolar electrochemistry, allowing symmetry breaking in terms of polarization and electrochemical reactions, is the key ingredient for efficient pumping.     

Trace analysis of 1,10-phenanthroline based herbicide in water and soil samples

A sensitive analytical procedure for diquat herbicide viz. 5,6-dihydropyrazino[1,2,3,4-lmn]-1,10-phenanthrolinium dichlorides in drinking water and soil samples, using differential pulse adsorptive stripping voltammetry (DPAdSV) has been developed. This involved the adsorptive accumulation of a diquat herbicide onto a hanging mercury drop electrode [accumulation potential -0.8 V vs Ag/AgCl, accumulation time 60 s, pH 7.0, ionic strength 0.1 M] for DPAdSV measurement. The detection limit for diquat herbicide was as low as 0.034 micromol L(-1) level (S/N 2, RSD 2.9%) at an accumulation time of 60 s.     

Hemicyanine-linked pyrimidine mimics as solvatochromic fluorophores with visible excitation wavelengths

The design of solvatochromic fluorescent nucleosides with visible excitation wavelengths is a goal towards the generation of modified oligonucleotides for fluorimetry-based molecular imaging. Herein, two hemicyanine-linked C5-2′-deoxyuridine nucleosides (PyI-dU and APPy-dU) have been synthesized by first generating hemicyanine-alkyne precursors that were attached via the alkyne moiety to 5-iodo-2′-deoxyuridine (5-I-dU) by Sonogashira coupling. The photophysical properties of the hemicyanine-linked dU probes have been characterized and compared to the corresponding properties of the hemicyanine-alkyne precursors. The nucleoside probe PyI-dU exhibits optical features that mimic the properties of the free hemicyanine-alkyne precursor, while the APPy-dU probe displays more favorable optical properties (longer excitation wavelength, brighter emission in water) than its precursor that is ascribed to π-stacking interactions between the hemicyanine dye with the dU nucleobase. Overall, probe APPy-dU is a superior solvatochromic fluorophore than PyI-dU suggesting its greater utility for fluorescent imaging applications.