Co-electro-polymerization/generation of poly-terthiophene/Au nanoparticle incorporated thin-film at a micro liquid|liquid interface

Khoshrou, Siamak (2021) Co-electro-polymerization/generation of poly-terthiophene/Au nanoparticle incorporated thin-film at a micro liquid|liquid interface. Masters thesis, Memorial University of Newfoundland.

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Abstract

Electroactive thin films are desirable for a wide array of applications, including catalysis, energy conversion, and (bio)sensor technologies. Herein, a novel strategy has been developed for the simultaneous electrochemical formation of polythiophene (PT) films with gold (Au) nanoparticle (NP) generation. In this method, AuCl₄⁻ (aq) is reduced at a water|1,2-dichloroethane (w|DCE) micro liquid|liquid interface by terthiophene (TT) positioned in the organic phase. The liquid|liquid interface is advantageous as it is molecularly sharp/smooth and highly reproducible, which distinguishes it from solid/solution interfaces where surface morphology can play a critical role. To further enhance the sensitivity of this technique, a micro interface between two immiscible electrolyte solutions (ITIES) was employed by use of a micropipette (25 μm in diameter). The morphology and size of the Au NPs at the ITIES was investigated by changing the applied potential, aqueous phase pH, and [KAuCl₄]:[TT] concentration ratio. Three different ratios, 1:1, 1:2 and 1:3, where chosen and paired with three pH regimes: 2, 5.5 and 8.5. The as-prepared Au-NP/PT films were then analyzed by Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM), while electrodeposition was monitored by cyclic voltammetry. Interestingly, Au NP size increased concomitantly with pH and the ratio of [KAuCl₄]:[TT]. Bithiophene was also investigated; however, no film formation was observed. Preliminary results using 4,5-didecoxy-1,8-bis(dithiafulvenyl)pyrene (C₁₀C₁₀bisDTF) are also discussed with respect to its electro-polymerization/deposition on to a carbon fiber ultramicroelectrode (UME) followed by electrodeposition of Au nanoparticles via electrode reduction of KAuCl₄(aq). These modified electrodes have been evaluated as selective dopamine (DA) sensors versus ascorbic acid.

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