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Published on: August 7, 2018
Polyaniline-metal oxide coatings for biocidal applications: Mechanisms of activation and deactivation
Han Fu1, Sofia Shewfelt1, Lena D Sylvan1
1Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, USA.
Abstract:
Metal oxide (MO) coatings (e.g. TiO2, ZnO, and CuO) have shown great promise to inactivate pathogenic bacteria, maintain self-cleaning surfaces, and prevent infectious diseases spread via surface contact. Under light illumination, the antibacterial performance of photoactive MO coatings is determined by reactive oxygen species (ROS) generation. However, several drawbacks, such as photo-corrosion and rapid electron-hole recombination, hinder the ROS production of MO coatings and diminish their antibacterial efficiency. In this study, we employed polyaniline (PANI), an inexpensive and easy-to-synthesize conductive polymer, to fabricate polyaniline-metal oxide composite (PMC) films. The antibacterial performance of PMC films was tested using E. coli as the model bacterium and Lake Michigan water (LMW) as the background medium and revealed enhanced antibacterial performance relative to MO coatings alone (approximately 75-90 % kill of E. coli by PMC coatings in comparison to 20-40 % kill by MO coatings), which is explained by an increase in the ROS yields of PMC. However, with repeated use, the antibacterial performance of the PMC coatings is diminished due to deprotonation of the PANI in the neutral/slightly basic aqueous environment of LMW. Overall, PANI can enhance the antibacterial performance of MO coatings, but efforts need to be directed to preserve or regenerate PMC stability under environmental conditions and applications.
Insights
Polyaniline-metal oxide composite films show enhanced antibacterial activity against E. coli by increasing reactive oxygen species (ROS) production. However, their performance decreases in neutral water due to polyaniline deprotonation.
Area of Science:
- Materials Science
- Nanotechnology
- Environmental Science
Background:
- Photoactive metal oxide (MO) coatings (TiO2, ZnO, CuO) offer antibacterial properties for self-cleaning surfaces and disease prevention.
- Their efficiency is limited by photo-corrosion and rapid electron-hole recombination, hindering reactive oxygen species (ROS) generation.
- Developing stable and efficient antibacterial coatings remains a critical challenge.
Purpose of the Study:
- To fabricate and evaluate polyaniline-metal oxide composite (PMC) films for enhanced antibacterial performance.
- To investigate the role of polyaniline (PANI) in improving the ROS generation and antibacterial efficacy of MO coatings.
- To assess the stability and performance of PMC films in a relevant environmental medium.
Main Methods:
- Fabrication of polyaniline-metal oxide composite (PMC) films using polyaniline (PANI) and MO nanoparticles.
- Testing antibacterial performance against E. coli in Lake Michigan water (LMW).
- Quantifying ROS yields and evaluating coating stability under repeated use.
Main Results:
- PMC films demonstrated significantly enhanced antibacterial activity (75-90% E. coli kill) compared to MO coatings alone (20-40% kill).
- The enhanced performance is attributed to increased ROS generation in PMC films.
- Antibacterial efficacy diminished with repeated use due to PANI deprotonation in the neutral/slightly basic LMW environment.
Conclusions:
- Polyaniline enhances the antibacterial performance of metal oxide coatings by boosting ROS production.
- The stability of PANI in PMC films is a limiting factor in neutral/alkaline aqueous environments.
- Further research is needed to improve the stability and longevity of PMC coatings for practical applications.
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