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Synthesis and Environmental Chemistry of Silver and Iron Oxide Nanoparticles

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Synthesis and Environmental Chemistry of Silver and Iron Oxide Nanoparticles SYNTHESIS AND ENVIRONMENTAL CHEMISTRY OF SILVER AND IRON OXIDE NANOPARTICLES By SUSAN ALISON CUMBERLAND A thesis submitted to The University of Birmingham For the degree of DOCTOR OF PHILOSOPHY School of Earth and Environmental Sciences College of Life and Environmental Sciences The University of Birmingham March 2010 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract Engineered nanoparticles are defined as having a dimension that is between one and one hundred nanometres. With toxicology studies reporting various degrees of toxicity the need to investigate nanoparticle fate and behaviour is vital. Monodispersed engineered nanoparticles were synthesised in-house to produce suitable materials to examine such processes. Iron oxide nanoparticles (5 nm) and citrate coated silver nanoparticles (20 nm) were subjected to different conditions of pH, ionic strength and different types of commercially available natural organic matter. Changes in particle size and aggregation were examined using a multi-method approach. Results showed that the natural organic matter was able to adsorb onto nanoparticle surfaces and improve their stability when subjected to changes in pH and ionic strength, where they would normally aggregate. The presence of higher concentrations of NOM in some cases promoted aggregation due to bridging. This work also concluded that silver nanoparticles could be produced in the presence of NOM without additional stabilisers and that they themselves were stable. This work has demonstrated that engineered nanoparticles could remain stable within a range of environmental conditions, and thus raise future pollution concerns. Acknowledgements Firstly, I would like to acknowledge my sponsors, NERC for funding this work. I would also like to thank all the people that made this thesis possible. To my supervisor, Professor Jamie Lead, who took me on to do this project and gave much support, direction and opportunity. The team at Exeter, Professor Charles Tyler, Dr Blair Johnson and Tessa Scown for the collaborative work that went into chapter 4 and supplying the tank water samples for analysis and Blair for supplying the fish mucus. There are many people that provided training and laboratory support, to which I would like to thank Ming Chu and Paul Stanley for help and support with the TEM and ESEM, Prof Colin Greaves for the XRD analysis. I would like to thank Mohammed Baalousha for his help and expertise with FFF and my first introduction to working with nanoparticles. Peter Bomford and Yon Ju-Nam for help and discussion about the nanoparticle synthesis, particularly Yon, whose early discussions led to developing the synthesis of the silver nanoparticles. I would also like to thank Paula, Eva, Nadia, Breda and the rest of r325 for being such excellent team mates and providing moral support and Gillian Kingston for extra lab support and chats about horses! John Bridgeman for his patience and help And lastly, to my partner, Steve, - for all the unlimited support he gave throughout for which I am eternally grateful- thank you! Contents 1 ....................................................................................................................... - 1 - Introduction ................................................................................................... - 1 - 1.1 Nanoparticles and their relevance ........................................................................................... - 2 - 1.1.1 History ................................................................................................................................. - 4 - 1.2 Need behind the research ......................................................................................................... - 5 - 1.3 Aims and objectives ................................................................................................................... - 7 - 1.4 Guide to the thesis ..................................................................................................................... - 7 - 2 ...................................................................................................................... - 9 - Background .................................................................................................... - 9 - 2.1 Definitions, classifications and history of NPs.................................................................... - 10 - 2.1.1 Natural NPs ...................................................................................................................... - 11 - 2.1.2 Incidentally produced NPs ............................................................................................. - 15 - 2.1.3 Intentionally produced NPs (manufactured NPs) ....................................................... - 17 - 2.1.4 Special properties of nanoparticles ................................................................................ - 21 - 2.1.5 Particle stability and aggregation .................................................................................... - 24 - 2.2 Types and applications of manufactured NPs ..................................................................... - 28 - 2.2.1 Applications ...................................................................................................................... - 29 - 2.2.2 International economics of manufactured NPs ........................................................... - 32 - 2.3 Nanoparticles and the environment ...................................................................................... - 34 - 2.3.1 Exposure ............................................................................................................................ - 35 - 2.3.2 Hazard and toxicity of ENPs ......................................................................................... - 40 - 2.3.3 Environmental risk of manufactured nanoparticles .................................................... - 46 - 2.4 Conclusion ................................................................................................................................ - 48 - 3 .................................................................................................................... - 50 - Methodology ................................................................................................ - 50 - 3.1 Introduction .............................................................................................................................. - 51 - 3.2 Nanoparticle characterisation techniques ............................................................................. - 54 - 3.2.1 Filtration and ultrafiltration ............................................................................................ - 54 - 3.2.2 Flow field-flow fractionation (FlFFF) ........................................................................... - 57 - 3.2.3 Dynamic light scattering (DLS) ...................................................................................... - 66 - i 3.2.4 Electron microscopy (EM) ............................................................................................. - 68 - 3.2.5 Brunauer, Emmett and Teller (BET) surface area analyser ....................................... - 71 - 3.2.6 X-ray diffraction (XRD) .................................................................................................. - 71 - 3.2.7 Electrophoretic mobility (EPM) and zeta potential .................................................... - 72 - 3.2.8 Surface plasmon resonance (SPR) ................................................................................. - 73 - 3.2.9 Fluorescence ..................................................................................................................... - 74 - 3.2.10 Total organic carbon (TOC) ......................................................................................... - 75 - 3.2.11 Graphite furnace atomic absorption spectrometry (GFAAS) ................................. - 75 - 3.3 Laboratory techniques ............................................................................................................. - 76 - 3.3.1 Sample preparation .......................................................................................................... - 76 - 3.3.2 Glassware preparation ..................................................................................................... - 77 - 3.3.3 Preparation of commercial NOM.................................................................................. - 77 - 3.3.4 Measurement of dissolved iron ...................................................................................... - 78 - 3.4 Statistical methods ................................................................................................................... - 79 - 3.4.1 Descriptive statistics ........................................................................................................ - 79 - 3.4.2 Parametric
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