Recognition of small organic molecules and large biomolecules such as proteins is of great importance in pharmaceutical as well as biological applications. Recognition inside a nanoporous membrane is particularly attractive, because of the advantages associated with ligand-receptor interactions in confined spaces. Classical nanoporous membrane-based separations simply use the difference in size of the analytes relative to pore size in the membrane. In order to bring about selectivity beyond size, it is necessary that methods for functionalizing the membrane pores are readily available. Here, we describe a simple approach to functionalize the nanopores within these membranes using self-assembling and non-self-assembling polymers. We show that these modified membranes separate small molecules based on size, charge and hydrophobicity. We also demonstrate here that proteins can be differentially transported through the nanopores based on their size and/or electrostatics.

The common reactions of dioxygen, superoxide and hydroperoxides with thiolates are thought to proceed via persulfenate intermediates, yet these have never been visualized. Here we report a 1.4 Å resolution crystal structure of the Fe2+-dependent enzyme cysteine dioxygenase (CDO) containing this putative intermediate trapped in its active site pocket. The complex raises the possibility that, distinct from known dioxygenases and proposed CDO mechanisms, the Fe-proximal oxygen atom may be involved in the primary oxidation event to yield a unique three-membered Fe-S-O cyclic intermediate. A non-polar environment of the distal oxygen would facilitate isomerization of the persulfenate to the sulfinate product.

A dibenzyl substituted poly (3,4-propylenedioxythiophene) was designed and synthesized, and exhibited a contrast of 89% at 632 nm with switching speeds of 400 ms and coloration efficiency of 575 cm 2 C 21 .Conjugated polymers 1 belong to an important class of polymers due to their widespread use in industrial applications like sensors, electrochromic materials, light emitting diodes (LEDs), actuators, and batteries etc. Electrochromics (ECs) are materials where the color exhibited is a function of applied potential. 2-4 Both inorganic and organic materials have been used as EC materials but there is still a lot of scope for further improvement in terms of switching speeds, stability, contrast and ease of synthesis and processing. Conducting or conjugated polymers have been found to be more promising as EC materials because of their better stability, faster switching speeds and easy processing compared to the inorganic EC materials. 2 EC materials where the color changes from a highly opaque colored state to highly transmissive bleached state are highly desirable as they are potential candidates for applications in display devices. In these systems, the change in percentage transmittance (D%T) between the two states is called the contrast and the higher the contrast, the better the material is for display applications. Conjugated polymers based on 3,4-alkylenedioxythiophene have attracted a lot of attention, both in academic as well as in industrial labs, as potential candidates for display applications because of their high contrast, low oxidation potential, better stability to air exposure at ambient and at elevated temperature conditions, and faster switching speeds. 5 Recently, Reynolds and coworkers have extensively studied the effect of ring size and also of ring substitution on the electrochromic properties of polymers based on 3,4-alkylenedioxythiophene. 5 They observed that the electrochromic contrast improves on increasing the ring size and also on increasing the interchain separation by the incorporation of a rigid/bulky side chain. 6 A tetradecyl substituted polyethylenedioxythiophene derivative was found to exhibit a D%T of 64%. However, the highest contrast (D%T of 78%) reported to date was observed in the case of a dimethyl substituted polypropylenedioxythiophene (PProDOT-Me 2 ). 7 Therefore, if one has to design a polymer with even better contrast than PProDOT-Me 2 one has to use more rigid/bulky substituents instead of methyl groups. Based on these facts, we designed and synthesized a dibenzyl propylenedioxythiophene (ProDOT-Bz 2 ) monomer (1). Incorporation of benzyl groups as the substituents, we think, will increase the interchain separation due to its rigid and bulky nature and hence the contrast. PProDot-Bz 2 exhibits an extremely high contrast of 89% at l max (632 nm) with coloration efficiencies of the order of 575 cm 2 C 21 ; in fact, these are the best reported values to date. In this communication, we report its synthesis, electrochemical and optical properties.The monomer 1 was synthe...

Organic lithium batteries are attractive because of the possibility of fabricating lightweight and flexible devices. However, the organic lithium batteries have a few drawbacks. The specific capacity is usually lower than the theoretical capacity, which further decreases upon cycling. Often, the specific capacity is very low compared to theoretical capacity while discharging the battery at moderate and high C rates. To circumvent this issue, we chemically reduced carboxylic acid functionality substituted perylene diimide (benzoic-PDI) with hydrazine. Indeed, we found that the rate of redox reaction as well as the conductivity of the benzoic-PDI increased upon chemical reduction. The battery comprising reduced benzoic-PDI exhibits 100% Coulombic efficiency and specific capacity while discharging at 20C. The battery also exhibits very high specific energy (213 Wh/kg) and specific power (8548 W/kg). The control experiments confirm our hypothesis of using chemical reduction to improve the performance of organic lithium battery.

A simple chemical etching procedure based on the solubility of polycarbonate membranes in solvent mixtures is reported for fabricating 3D gold nanoelectrode ensembles. A solvent ratio of 50:50 dichloromethane/ethanol was found to be optimum for selective controlled etching of the surface layers of the polycarbonate membranes to expose up to 200-nm lengths of gold nanowires. The absence of double layer charging current in cyclic voltammograms of the resulting 3D nanoelectrode ensemble verified that the seal between the gold nanowires and the polycarbonate membrane was not compromised as a result of the chemical etching.

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Monosubstituted and disubstituted 3,4‐propylenedioxythiophenes were synthesized and polymerized by both chemical and electrochemical methods. All the monomers were characterized for their molecular structures, and the polymers were characterized for their electrochemical properties. The disubstituted derivatives showed higher contrast than the corresponding monoalkyl derivatives. The highest electrochromic contrast of 89% was exhibited by a dibenzyl derivative, but the derivative was insoluble. On the other hand, the electrochemically polymerized dihexyl‐ and didodecyl‐substituted poly(3,4‐propylenedioxythiophene)s exhibited 74 and 77% electrochromic contrast, respectively, and were soluble. The molecular weights of the chemically and electrochemically synthesized polymers were analyzed by gel permeation chromatography. The chemically synthesized polymers showed higher molecular weights. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 419–428, 2005

Chemical doping of an electron transporter results in the formation of a radical anion containing semiconductor which showed high electron mobility (13 cm(2) V(-1) s(-1)) at low operating voltage (1 V).