High-Capacity Conductive Nanocellulose Paper Sheets for Electrochemically Controlled Extraction of DNA Oligomers

Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg−1, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30–50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m2 g−1) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)6, (dT)20, and (dT)40 DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules

Synthesis, characterisation and ion transport studies on polypyrrole/deoxyribonucleic acid conducting polymer membranes

Thin films composed of polypyrrole/deoxyribonucleic acid (PPy/DNA) were prepared by potentiodynamic potentiostatic and galvanostatic methods from aqueous solutions containing pyrrole and salmon sperm DNA. This material was also grown as large free-standing membranes, and onto platinum sputter-coated polyvinylidene fluoride (PVDF) filters to form composite membranes. Electrochemical studies of this material indicated that it could be oxidised and reduced, inducing ion movement in and out of the surrounding solution. The results of elemental phosphorus analysis confirmed that DNA had been incorporated into the conducting polymer as a dopant, while four-point probe measurements on free-standing PPy/DNA membranes gave a conductivity of 0.11 S cm-1. UV-VIS spectroscopic studies of films grown onto indium/tin oxide coated glass were also consistent with the polymer being conducting in its oxidised form. Scanning electron microscopy and atomic force microscopy showed that the surface of free-standing membranes was relatively smooth. Transport of potassium and copper across composite PPy/DNA/Pt/PVDF membranes was achieved using an applied pulsed potential and source solutions containing these ions. However, under the same conditions no transport of calcium, magnesium or iron was observed. A Cu2+/Fe3 selectivity factor of 33 was calculated using metal ion fluxes obtained from a transport experiment performed using a source solution containing both of the above metal ions. This value is six times larger than Cu2 /Fe3 selectivity factors previously reported for conducting polymer membranes

Conducting Polymer Nanomaterials and Their Applications

A paradigm shift takes place in the fabrication of conducting polymers from bulky features with microsize to ultrafine features with nanometer range. Novel conducting polymer nanomaterials require the potential to control synthetic approaches of conducting polymer on molecular and atomic levels. In this article, the synthetic methodology of conducting polymer has been briefly considered with chemical oxidation polymerization and electrochemical polymerization. The recent achievements in the fabrication of conducting polymer nanomaterials have been extensively reviewed with respect to soft template method, hard template method and template-free method. It also details the morphological spectrum of conducting polymer nanomaterials such as nanoparticle, core-shell nanomaterial, hollow nanosphere, nanofiber/nanorod, nanotube, thin film and nanopattern and nanocomposite. In addition, their applications are discussed under nanometer-sized dimension.This work has been financially supported by the Brain Korea 21 program of the Korean Ministry of Education and the Hyperstructured Organic Materials Research Center supported by Korea Science and Engineering Foundation