Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Dr. Paul A. Charpentier

Abstract

While temporary disinfection of a surface is possible with the help of strong cleaners, tremendous interest exists for the control of microorganisms on surfaces by effective, durable antimicrobial coatings. There is a wide spectrum of potential applications for antibacterial coatings, spanning from industrial surface coatings to biomedical applications, where sterile conditions are crucial. This work examined the synthesis of the functionalized 2,2-Dimethylolpropionic acid - nanotitanium dioxide (DMPA-nTiO2) monomer. Moreover, functionalized nanotitanium dioxide/polyurethane (nTiO2/PU) composite coatings were prepared using the above mentioned functionalized monomer. The distribution of nTiO2 in the polymer matrix was enhanced by monomer functionalization in which nTiO2 was chemically attached to the backbone of the polyurethane polymer matrix with a bifunctional monomer (DMPA). The coordination of nTiO2 to DMPA was monitored by TGA characterization. Moreover, the surface hydrophilicity test was conducted on the nanofilms by examining the contact angle. SEM and elemental mapping analysis were also performed to study the surface morphology of the nanofilms and to measure the dispersion and compositional analysis of nanofillers in the polymer matrix. Two metal doped TiO2 nanoparticles (Fe/TiO2, and Ag/TiO2) were synthesized to control the band gap energy of TiO2 nanomaterials and hence the photocatalytic activities of nTiO2/polyurethane nanocomposite coatings. Moreover, some characterization techniques (such as SEM, TEM, XRD, and TGA) were done to probe the internal structure and properties of the above mentioned doped titania nanoparticles. The photocatalytic reaction rate constants of Fe and Ag doped TiO2 nanoparticles, along with undoped TiO2 nanoparticles, were measured and compared under solar light illumination. Since the photocatalytic reaction rate constant of Ag doped TiO2 nanoparticles was generally higher than that of Fe doped TiO2 nanoparticles, under both solar and visible light illumination, Ag doped TiO2 nanoparticles were used in this study to make functional nanocomposites. The antibacterial behavior of nTiO2/PU and silver doped nTiO2/PU composites were investigated qualitatively and quantitatively against both gram-negative (Escherichia coli) and gram-positive (Micrococcus luteus) bacteria. The effect of exposure time was investigated using a solar simulator by monitoring the growth of bacterial populations in the presence and absence of the above-mentioned nanocomposites. The quantitative examination of bacterial activity was determined by the survival ratio as calculated from the number of viable cells, which form colonies on the Petri dishes with nutrient agar. Excellent inhibition results were observed and demonstrated visually with more than 99% of bacteria killed after 2 hours of irradiation. In summary, the functionalized nTiO2/PU and silver doped nTiO2/PU composite coatings displayed considerable antibacterial activity against both gram-positive and gram-negative bacteria under solar light irradiation while silver doped nTiO2/PU coatings displayed considerable antibacterial activity even under irradiation of visible light.

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