The Environmental and Biological Implications of Nanoparticles - PowerPoint PPT Presentation

The Environmental and Biological Implications of Nanoparticles Faculty Advisor: Dr. Arturo Keller UC Center for the Environmental Implications of Nanotechnology INSET Project Mentor: Dr. Milka Montes Jason Gehrke, Chemistry Major, Santa Barbara City College

Nanoparticle Lifecycles  Expand on the knowledge of nanoparticles (NPs)  Increase understanding of NP life cycle  During use and after entering environment  Interactions with biological systems http://www.futurity.org/science-technology/designer-dots-could shield-food-chain/ 2

Silver Nanoparticle Size http://www.jnanobiotechnology.com/content/figures/1477-3155-3-6-1.jpg 3

Amino Acid Adsorption and NP Behavior  TiO 2 and Ag-citrate NPs - Widely used in consumer products  Effects of ionic strength, pH  Stability of suspension: -Amino acid adsorption -Surface charges http://pubs.acs.org/doi/full/10.1021/es1042832 -Aggregation 4

Determining Suspension Characteristics Spectrophotometry http://en.wikipedia.org/wiki/File:Spetrophotometer-en.svg Dynamic Light Scattering 5 http://en.wikipedia.org/wiki/File:DLS.svg

Zeta Potential and Suspension Stability 6 http://www.bioresearchonline.com/article.mvc/Automated-Protein-Characterization-With-The-M-0002

Environmental Thiol Concentrations Bell, 1997 7

Ag, L-Cysteine Complex Aggregation pH < 8.0 - pH > 8.0 Time (min) 8 Samples: Ag NPs (1 mg/L), L-cysteine (10 mM), NaCl (10 mg/L)

Ag-Cysteine Complex as Function of Ionic Strength, pH Ag-Cysteine Absorption Spectra 0.25 Ag Control 0.2 (10mg/L) 0.15 Absorption Cys pH 7.0 10mM 0.1 NaCl 0.05 Cys pH 9.0 10mM 0 0 200 400 600 800 1000 -0.05 Wavelength (nm) 9

Formation Mechanism Cohen-Atiya et al , Journ. Elec. Chem., 2002 10

Cysteine Adsorption Conformation  Coadsorption of chloride ion with cysteine + + - Ag NP + + + + + 11

Complex Formation as a Function of IS Ag, L-Cysteine Particle Size 1200 60 Hydrodynamic Diameter 50 1000 40 (nm) 30 Hydrodynamic Diameter (nm) 20 800 10 0 0 20 40 60 80 100 120 140 Time (min) 600 400 Ag-Cys, pH 7.1, 1 mM NaCl 200 Ag-Cys, pH 7.1, 10 mM NaCl 0 0 20 40 60 80 100 120 140 160 12 Time (min)

Ag-Cysteine Complex in Environment 13

Complex Characterization • Formation is highly dependent on pH, IS, and concentration of L-cysteine • Chloride ions are coadsorbed on Ag surface with cysteine • Complex results in aggregation or disaggregation of NPs based on IS • Prevents stabilization by natural organic matter (NOM) 14

Future Research • Environmental Scenarios - involving freshwater with natural organic matter • Adsorption isotherms – characterizing the Ag-cysteine complex formation as a function of cysteine concentration • Fate of Ag-cysteine complex 15

Ag-Cysteine Count Rates, [NaCl]=10 mM 16

Complex Formation and Aggregation 17