Effect of processable polyindole and nanostructured domain on the selective sensing of dopamine

The effect of carboxylic acid functionality present in polymer backbone is reported on electrochemical sensing of dopamine (DA). The electropolymerized conducting polymers made from carboxylic acid substituted indole at positions − 5 and − 6 are found processable in aqueous medium and are compatible with suitable additives/precursors for fabricating polymer modified electrodes (PMEs). The modified electrodes are fabricated following two methods, i.e.: (1) the processable polymers are cast over glassy carbon electrode (GCE) using Nafion® followed by chemical modification using hydrophobic organic redox mediators and (2) the processable polymers are encapsulated within organically modified silicate (Ormosil) matrix along with the hydrophilic redox mediator followed by incorporation of silver and gold nanoparticles. The electrochemical performances of these modified electrodes show selective sensing of DA with major findings: (i) both polymers introduced selectivity in electrochemical sensing of DA with analogous sensitivity, (ii) sensitivity is enhanced when hydrophobic organic redox mediators are coupled with modified electrode matrix involving Nafion®, (iii) the polymers are suitable for encapsulation within ormosil matrix thus introducing nanostructured network for further improvement in sensitivity of DA analysis, (iv) the presence of gold and silver nanoparticles within ormosil matrix along with polymers caused > 100 fold increase in sensitivity of DA sensing with lowest detection limit to the order of 100 nM.

► We report electrochemical polymerization of carboxylic acid substituted indoles.
► The polymers of 5 and 6 substituted indoles are found processable in aqueous medium.
► The processable polymers are utilized for selective sensing of dopamine.
► Incorporation of electron transfer mediators resulted into tremendous improvement in sensitivity.
► Introduction of nanostructured domains further enhanced the performance of sensor.