Design, Fabrication and Applications of Efficient Conductive Polymers for Photocatalytic Antimicrobials
Abstract
Designing new antimicrobial surfaces which are effective under visible light irradiation without leaching toxic ions is a current challenge for effective disinfection. A new polymeric system poly[2,11’-thiophene-ethylene-thiophene-alt-2,5-(3-carboxyl) -thiophene] (PTET-T- COOH) with broad light absorption was synthesized. Its photocatalytic disinfection performance against staphylococcus aureus (S. aureus) and streptococcus suis (S. suis) was evaluated, showing over 99.999% inactivation (higher than 5-log inactivation) in 2 h for both bacteria, under visible light irradiation at a low concentration of PTET-T-COOH (0.1 mg/mL). In addition, a PTET-T-COOH/polyurethane (PU) polymeric coating was designed and fabricated. Chemical attachment was confirmed between PTET-T-COOH and PU using various thermophysical techniques (FTIR, XPS and UV-Vis absorption spectra). The coating was found to possess excellent photocatalytic disinfection effect on S. aureus (7-log inactivation) in 4 h under visible-light exposure. PTET-T-COOH and PTET-T-COOH/PU coating demonstrated good stability, showing excellent antibacterial activity after five runs. The chemical interaction was generated and confirmed between PTET-T-COOH and PU. The active species generated and responsible for the photocatalytic disinfection were confirmed to be singlet oxygen and free electrons by using scavengers and electron spin resonance spectroscopy (ESR) in PTET-T-COOH based systems. In addition, ultrathin graphitic carbon nitride (g-C3N4) nanosheets with rich amino groups (g-C3N4-NH2) were also fabricated to inactivate more than 80 % of S. aureus in 2 h upon visible light exposure. The photocatalytic activities of g-C3N4-NH2 and g-C3N4 were compared and the reasons for improved performance of g-C3N4-NH2 were also analyzed. The results from this thesis will open a new strategy for exploring novel high-efficiency and durable disinfection coatings for living environmental and industrial applications.