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Title:Surfactant assisted phase transfer of water-insoluble quantum dots
Author(s):Lin, Xiaowen
Advisor(s):Bhalerao, Kaustubh
Department / Program:Engineering Administration
Discipline:Agricultural & Biological Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Quantum dots
environment
water
surfactant
phase transfer
Abstract:Nanotechnology is believed to have the potential of solving the biggest challenges for human beings in areas such as environment protection, renewable energy, and disease detection and treatment. At the same time, this new technology could also pose unknown potential risk to the environment. While commercialization of nanotechnology is growing rapidly across a wide range of products, regulation of nanotechnology to limit the negative impacts is currently lacking. Among the impacts of nanotechnology on the environment, we are specifically interested in the transformation of nanomaterials in the aqueous environment and their subsequent fate. The pri-mary objective of the research presented in this thesis is to study the role of surfactants in facilitating the phase transfer of hydrophobic nanomaterials from organic solvents into the aqueous phase. Without surfactants, hydrophobic nanomaterials would aggregate into micro-scale aggregates in water, potentially reducing their bio-availability, mobility, and toxicity. However, biologically produced surfactant-like molecules are ubiquitous in the aqueous environment, and it might alter the hydrophobic surface into hydrophilic, increasing the environmental risk. Hence, the risk of hydrophobic nanomaterials in the environment may be underestimated. To investigate the potential phase transfer phenomenon, we have chosen a model experimental system consisting of quantum dots (QDs), a nanoparticle with fluorescence and a model surfactant, to study their interaction. A new scenario of quantum dots phase transfer in aqueous environment was proposed. The experimental result shows that there are several factors that affect the extent of phase transfer. These include the rate of addition of organic QDs solution to the surfactant solution and absolute and relative concentrations of surfactant and QDs. The lower the ratio, the higher phase transfer efficiency. Also, as the concentration of surfactant increases, the phase transfer efficiency will increase, as well as the saturation concentration of the phase transferred quantum dots. The stability of the phase transferred quantum dots is determined by the strength of the surfactant. With the surfactant we have tested, the phase transferred QDs eventually forms aggregates and settles out. After investigating the phase transfer of QDs, we are currently investigating the toxicity of these phase transferred QDs on Synechococcus elongatus as well as on microbial communities in an anaerobic bio-digester.
Issue Date:2013-08-22
URI:http://hdl.handle.net/2142/45597
Rights Information:Copyright 2013 Xiaowen Lin
Date Available in IDEALS:2013-08-22
2015-08-22
Date Deposited:2013-08


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