Tina Chakrabarty

Polymer thin films embedded with metal nanoparticles for electrochemical biosensors applications.

Currently, polymer thin films embedded with metal nanoparticles provided the suitable microenvironment for biomolecules immobilization retaining their biological activity with desired orientation, to facilitate electron transfer between the immobilized enzymes and electrode surfaces, better conformation and high biological activity, resultant in enhanced sensing performance. This article reviews focus on various methods for brief discussion of fabrication of metal nanoparticles-polymer hybrid materials and their applications in different electrochemical biosensors. The performance of hybrid materials based electrochemical biosensor can be improved by synergic properties of the metal nanoparticles and polymer network with biomolecules interface via engineering of morphology, particle size, effective surface area, functionality, adsorption capability and electron-transfer properties. These attractive features to hybrid materials are expected to find applications in a new generation of miniaturized, smart biochip devices.

Highly charged and stable cross-linked 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS)-sulfonated poly(ether sulfone) polymer electrolyte membranes impervious to methanol

Disulfonated 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS) was synthesized as cross-linking agent. In situ cross-linking of sulfonated poly(ether sulfone) (SPES) via sulfonamide linkage was achieved using BAPBDS, for preparing polymer electrolyte membranes (PEMs), without deterioration in membrane functionality due to cross-linking. Effective cross-linking enhanced the membranes’ dimensional, thermal, and chemical stability without impairing the electro-chemical properties such as ion-exchange capacity and proton conductivity. Thus, the properties of the developed PEMs were significantly improved due to more compact structure of the cross-linked SPES membrane (CPES) over membranes without crosslinking. Comparable selectivity parameter (SP) and direct methanol fuel cell (DMFC) performance of the developed membranes, especially CPES-100, with Nafion 117 (N117) indicated their suitability for fuel cell applications.

Zwitterionic silica copolymer based crosslinked organic–inorganic hybrid polymer electrolyte membranes for fuel cell applications

Zwitterionic (ZI) copolymers (consisting of sulfonic acid and amine groups) with plenty of –Si(OCH)3groups similar to stems, branches and fruits of vines from a bionic aspect, were synthesized as a cross-linking agent. Organic–inorganic hybrid zwitterionic membranes (ZIMs), with high flexibility, charge density and conductivity, was prepared using poly(vinyl alcohol) (PVA). Developed ZIMs with dual acidic and basic functional groups, exhibited high stabilities, water retention ability and cation selectivity. The ZIMs (especially Si–70%) were designed to possess all the required properties (water uptake: 40.6%; ion-exchange capacity: 1.52 equiv. g−1; electro-osmotic flux: (2.34 × 10−5 cm s−1A−1); and conductivity: 9.67 × 10−2 S cm−1. ZIMs were designed to possess all of the required properties of a proton-conductive membrane, namely, reasonable swelling, good mechanical, dimensional, and oxidative strength, flexibility, and low methanol permeability along with good proton conductivity due to zwitterionic functionality. Moreover, Si–70% and a Nafion117 membrane exhibited comparable DMFC performance. Also, investigation on a multi-ionic organic–inorganic hybrid ZIM as polymer electrolyte membranes (PEMs) will give rise to a new developing field in materials and membrane science.

Modified chitosan-based, pH-responsive membrane for protein separation

N-Carboxymethyl chitosan (N-CMCS) and O-carboxymethyl chitosan (O-CMCS)-based amphoteric or pH-responsive charged membranes were prepared for protein separation. Both membranes (O-CMCS and N-CMCS) exhibited different charged natures and acidic/alkaline ion-exchange capacities along with 16–19 kDa molecular weight cut-off (MWCO), corresponding to 0.53 nm and 0.48 nm pore radius at pH 7.0 for O-CMCS and N-CMCS, respectively. Water permeability for O-CMCS and N-CMCS membranes varied between 5.0–6.0 × 10−8 Pa−1 m h−1 (ultra-filter range) and increased with equilibrating medium pH. The dual-charged nature of these membranes (presence of –COOH and –N+H3 groups) was advantageously used to achieve antifouling properties in biomolecule separation. The N-CMCS membrane exhibited a positively charged nature in the 2.0–12.0 pH range. Thus, Donnan exclusion due to mutual electrostatic attraction between the membrane and protein was insignificant in accelerating the mobility of a protein molecule, thus achieving its separation. Meanwhile, the O-CMCS membrane showed pH-tunable charged nature and suitable separation performance for β-casein (β-Cas) and lysozyme (Lys) across alkaline media, as a representative case. Furthermore, no membrane fouling was detected after 50 days of operation in a protein environment.

Chitosan Based Membranes for Separation, Pervaporation and Fuel Cell Applications: Recent Developments

Growing public health and environmental awareness accompanied by increasing number of stricter environmental regulations on wastes discharge. Attention has been focused on the use of biopolymers from renewable resources as alternatives to synthetic polymers [1]. Biopolymers are produced in nature by living organisms and plants, participate in the natural biocycle and are eventually degraded and reabsorbed in nature. The most widespread biopolymers are polysaccharides among them chitosan(CS) is most valuable, whose swellability in water and viscous solution/gel-forming properties were utilized by manufacture for number of industrial and consumer products. CS (primary derivative of chitin) is commercially available basic polysaccharide [2,3]. The basicity of CS responsible for singular chemical and biological characteristics, biocompatibility, antibacterial properties, heavy metal ion chelation ability, gel-forming properties, hydrophilicity, affinity to proteins and good membrane forming capability. In this chapter we will discuss for modification of CS and its exploitation for advance membrane separation applications. The membrane processes were classified by Howell includes [4]: 1. Cleaner industrial process: adsorption, ultrafiltration and electro-ultrafiltration. 2. Energy: fuel cell applications 3. Pervaporation: separation of organic solvents from their azeotropic mixtures. 4. Water: virus–free supply, water reuse and micro-pollutant-free water Chitosan is obtained by varied extent N-deacetylation and characterized by degree of deacetylation (Fig. 1). It is a copolymer of N-acetyl glucosamine and glucosamine and insoluble in water. CS readily dissolves in acidic solutions due to the presence of amino groups and 80–85% degree of deacetylation is necessary to obtain a soluble product. Commercially, CS is obtained from low cost shells of shellfish (mainly crabs, shrimps, lobsters and krills), the wastes of the seafood processing industry [2-6]. Chemical and biological properties of CS attributable to the presence of amino and hydroxyl groups [2,3,58]. These groups allow chemical modifications of chitosan: acylation, N-phthaloylation, tosylation, alkylation, Schiff base formation, reductive alkylation, O-carboxymethylation, Ncarboxyalkylation, silylation, and graft copolymerization [3,9]. Modifications of CS will help

Cross-Linked Zirconium Tri-Ethylenetetramine Membrane in Aqueous Media for Selective Separation of Cu2+

Cross-linked membrane of zirconium tri-ethylene tetra-amine (ZrTETA-55) was prepared by sol-gel method using poly (vinyl alcohol) (PVA) in aqueous media for selective separation of Cu2+. Developed ZrTETA-55 hybrid membrane exhibited good thermal, mechanical, and chemical stabilities, which are essential parameters for its durability. ZrTETA-55 hybrid membrane was used as an adsorbent for selective adsorption of Cu2+, and the effect of time, temperature, pH, adsorbent dose, and adsorbate concentration were investigated. The adsorption process followed the pseudo-first and pseudo-second-order kinetic models which were also evaluated. The equilibrium adsorption obeyed the Langmuir and Freundlich isotherms. The thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were calculated. From thermodynamic data, it was found that the adsorption process was endothermic and spontaneous. The maximum adsorption of Cu2+ ions was found to be ∼74% at pH 7 and indicated that the developed material could be effectively utilized for the selective separation of Cu2+ in the presence of other bi-valent ions in industrial effluents. Supplemental materials are available for this article. Go to the publishers online edition of Separation Science & Technology to view the supplemental file.

Correction: Modified chitosan-based, pH-responsive membrane for protein separation

Correction for ‘Modified chitosan-based, pH-responsive membrane for protein separation’ by Tina Chakrabarty et al., RSC Adv., 2014, 4, 53245–53252.