Hydrogels are materials with a three-dimensional cross-linked structure and large surface area that are easily swollen by water. Due to interstitial spaces, hydrogels allow the transport of small molecules. Conductive polymer hydrogels are preferable due to not only their swelling and mechanical properties, but also the electron transport properties that conductive polymers provide. Hydrogels of polyaniline (PANI), polyindole (PIN), and poly(indole-5-carboxylic acid) (PIN5COOH) were chemically synthesized with poly(styrene sulfonate) at pH 5. To characterize the hydrogels, Infrared Spectroscopy (IR) was used, but intense bands from both water and poly(styrene sulfonate) were present. Thus, Raman Spectroscopy was used at excitation lines 455, 633, and 1064 nm to characterize the gels. The spectra of the PANI gel showed bands corresponding to its bipolaronic and conductive forms. Spectra for the PIN gel reveal bands characterizing C=N bond modes and heteroaromatic rings, which agree with PIN structure. The PIN5COOH gel spectra showed bands typical to carboxylic acid groups, as well as bands in the PIN spectra. In addition, Raman spectra of electrochemically deposited films of the polymers were obtained, which confirmed bands seen in the gel spectra. Cyclic voltammograms of the gels validated the redox properties of the conductive polymers gels. Morphological studies were conducted using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), which suggested formation of tiny polymer spheres bound to each other. Overall, conductive polymer hydrogels enhance conductivity and sensitivity, potentially adding to sensor design possibilities. Preliminary application of PANI gel as substrate for the enzyme tyrosinase was applied to the chronoamperometric detection of catechol. The sensitivity of the PANI gel-based biosensor (1080 μA M-1) was notably greater when compared to that of the PANI film (103 μA M-1). Catechol detection was also studied using PANI gel enhanced with gold nanoparticles, which increased the sensitivity to 2370 μA M-1.

Synthesis and characterization of conductive polymer hydrogels and the investigation of their application as a biosensor hybrid for the detection of catechol

253rd National Meeting (2017)

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