Tuning Luminescence from Carbon Nanodots: A New Strategy for Antimicrobial Inactivation
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Date
2020-01-01
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Department
Chemistry & Biochemistry
Program
Chemistry
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Distribution Rights granted to UMBC by the author.
This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu
This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu
Abstract
Beyond antibiotics, sterilization techniques hold significant promise in combating the growing threat of bacterial antibiotic resistance—which has retained urgency in recent years. One such strategy is antimicrobial photodynamic inactivation (APDI) of bacteria, also known as antimicrobial photodynamic therapy. APDI—which combines excitation light, molecular oxygen, and a photosensitizing agent to generate highly reactive oxygen species (ROS)—is broadly effective against many pathogens. Activity is controllable by modulating exposure light and tunable by photosensitizer properties. Although many photosensitizers are reported, many are small molecules limited in scalability by complex synthetic procedures, purification requirements, and costly reagents. Carbon nanodots present a promising alternative. These fluorescent nanoparticles are composed of many-layered oxidized graphene and are known combustion byproducts that may be easily and inexpensively collected. To date, most carbon dot research has focused on tuning fluorescent properties. In this emerging chapter of carbon nanodot research, we aim instead to tune the carbon dot properties for APDI. We report a simple set-up, employing the combustion of natural gas for nanodot collection together with an array of diverse precursors to gain novel photophysical properties. Namely, we report the collection of phosphorescent brominated carbon nanodots, and further characterize their ROS-generating capabilities (producing both singlet oxygen and hydroxyl radical) with 365 nm activation. Remarkably, we find them to be effective APDI photosensitizers against both gram-negative Escherichia coli and gram-positive Staphylococcus aureus and Listeria monocytogenes. Further, we find that these properties are all enhanced by the principles of "inter” metal-enhanced fluorescence, employing the "Quanta Plate™” plasmonic silver platform. We conclude by suggesting further tuning of the synthetic regime to reach new applications in the titular objective: "Tuning Luminescence from Carbon Nanodots.”