Single-Step Coelectrodeposition of Hybrid Silica Nanocomposite Directs the Fabrication of Free-Standing and Transferal Conducting Polymer Thin Films
Authors: Farghaly Ahmed A. , Collinson Maryanne M. 
Published: February 2020

Conducting polymers have fascinated scientists over the years due to their superior properties and potential technological applications in optoelectronic devices, sensors, coatings, flexible electronics, electrocatalysis, tissue engineering, batteries, etc.1-3 However, the poor mechanical properties, stability and processability of the conductive polymer materials have limited such applications. Doping the conductive polymer material with inorganic components through the formation of organic–inorganic hybrid composites is an appealing route to overcome these problems. Silica is a potential candidate as the inorganic component in such hybrid composites due to its improved mechanical strength, chemical and thermal stability, tunable structure and porosity. Conducting polymers can be prepared by oxidizing the monomer solution using oxidizing agents, such as FeCl3 or by applying an anodic potential. On the other hand, silica can be prepared electrochemically via cathodic deposition of the silane monomers.4 To date, there is no available strategy to simultaneously synthesize silica-conducting polymer hybrid composites using a single deposition potential.3 Silica-conducting polymer hybrid composites are generally prepared in a two-step process that involves anodic deposition of the conducting polymer followed by cathodic deposition of the silica and vice versa.3Herein, we report on several new findings based on the combination of electrodeposition, sol-gel chemistry and electropolymerization processes. First, silica can be electrodeposited from strongly acidic solution of pH ~ 1 containing the silane monomers. Second, silica-conducting polymer and silica-metal-conducting polymer hybrid nanocomposites can be fabricated by cathodic deposition in a one-step process. The mechanism of the electropolymerization process under cathodic conditions is different from that occurring under anodic potentials, which allows the formation of new structures and morphologies and provides new avenues for material synthesis that cannot be achieved using conventional anodic methods. Third, the preparation of free standing and transferable thin films was achieved by two different routes: (a) silica etching due to the different kinetics for silica and the conducting polymer electrodeposition; (b) by dissolving the oxidizable electrode material in an acidic solution. The obtained silica-conducting polymer thin films can be immobilized on a variety of substrates, such as gold, ITO, glassy carbon, copper and even glass, which enables the preparation of cheap conducting polymer-based sensors and miniaturized devices. The as-prepared silica-conducting polymer and silica-metal-conducting polymer hybrid nanocomposites were characterized by XRD, surface profilometry, BET, EDX, SEM and cyclic voltammetry.
References
1. C. Janaky and C. Visy, Analytical and Bioanalytical Chemistry 405 (11), 3489 (2013)
2. T. F. Otero, Polymer Reviews 53 (3), 311 (2013)
3. M. Raveh, L. Liu and D. Mandler, Physical Chemistry Chemical Physics 15 (26), 10876 (2013)
4. A. A. Farghaly and M. M. Collinson, Langmuir 30 (18), 5276 (2014)

Figure 1