Files
Abstract
Infectious diseases caused by bacteria continue to be a major problem in our daily life. The discovery of antibiotics has helped improve human health and medical treatments dramatically since 1940s. However, the number of infections associated with drug-resistant bacteria keeps increasing in recent years. Inorganic nanomaterial is considered as a promising candidate to solve such a difficult problem. This dissertation focuses on exploring three novel inorganic antimicrobial nanomaterials, carbon dots, CuBi2O4 and CuxFeyOz, and their morphological, structural, optical, antimicrobial and other properties.The carbon nanodots with a size around 5 nm are modified with a layer of surface passivation of 2,2-(Ethylenedioxy)bis(ethylamine) (EDA) molecules. They show visible light induced photodecay rate of 0.307 0.0002 h-1 against methylene blue (MB), and demonstrated 4 logs of Escherichia coli (E. coli) reduction after 30 min treatment with visible light illumination. Narrow bandgap semiconductor CuBi2O4 microstructures with different morphologies such as three dimensional hierarchical microspheres, microflowers, one dimensional microrods and nanorods are fabricated through a hydrothermal synthesis approach by systematically changing the synthesis conditions. Among them, the hierarchical micro-flower shaped CuBi2O4 sample at aconcentration of 1 mg/ml shows a high photodecay rate of 0.114 0.002 h-1 against 30 M MB, and a high antibacterial effect against E. coli, with ~ 93% bacteria reduction after 6 h illumination by a commercial white LED light (10 mW/cm2) comparing with the negative controls. In addition to these two antimicrobial photocatalysts, the CuxFeyOz nanostrucutres fabricated by microwave-assisted hydrothermal synthesis exhibit highly antimicrobial properties without light illumination. The optimized CuxFeyOz nanoparticles (1 mg/ml) can kill 109 CFU/ml E. coli in PBS in 15 min and 1010 CFU/ml Staphylococcus aureus (S. aureus) in 1 hr. Similar effect is found for highly drug-resistant bacteria such as K. Pneumoniae 148 and H. pylori X47. These CuxFeyOz suspensions are also effective in inhibiting the bacterial growth in fresh media and are low toxic to mouse fibroblast cells at 1 mg/ml.This dissertation work demonstrates that inorganic nanomaterials are promising candidates for antimicrobial applications.