Heavy metal (HM) containing quantum dots (Qdots) are increasingly used in commercial products due to their unique electronic, optoelectronic, optical and magnetic properties. Once disposed to the landfill, environmental weathering is likely to compromise HM Qdot integrity, leading to release of heavy metal ions. To minimize any negative environmental impact of HM Qdots, there is an increasing demand for developing HM free or environmentally-friendly surface modified HM Qdot alternatives. In this study, synthesis of HM free ZnS:Mn/ZnS and surface modified HM CdS:Mn/ZnS Qdots (using N-acetylcysteine, NAC, and Dihydrolipoic acid, DHLA) and their potential toxicity assessment using E. coli as a model system is reported. NAC and DHLA are known antioxidants and therefore expected to reduce HM induced toxicity and improve colloidal stability of Qdots. All Qdots were synthesized at room temperature using a reverse micelle microemulsion method. Qdots were fully characterized using UV-visible absorption spectroscopy, fluorescence emission spectroscopy, zeta potential, Nuclear Magnetic Resonance spectroscopy (NMR) and High Resolution Transmission Electron Microscopy (HRTEM). Qdot environmental weathering was simulated by treating Qdots with concentrated acid (6N HCl). Qdot toxicity was evaluated on E. coli growth and viability using growth curves, turbidity and bactericidal assays (CFU). Results show that Zn based Qdots exhibit reduced toxicity on E.coli growth and viability when compared to Cd based Qdots. In addition, surface modification with NAC and DHLA minimized toxicity of Cd based Qdots. In summary, Zn based Qdots appear to be more environmental-friendly than Cd based Qdots
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd-4012 |
| Date | 01 January 2013 |
| Creators | Tharkur, Jeremy |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations |
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