Nanoparticle Technology Dispersions in liquids: suspensions, emulsions, and foams ACS National Meeting April 9 10, 2008 New Orleans
Wetting in nano ACS National Meeting April 9 10, 2008 New Orleans 10
Apparent contact angles - surface roughness Water strider resting on water and SEM images of a water strider leg at two magnifications. Feng, X.-Q.; Gao, X.; Wu, Z.; Jiang, L.; Zheng, Q.-S. Superior water repellency of water strider legs with hierarchical structures: Experiments and analysis. Langmuir, 23, 4892 4896, 2007. 11
Contact angles on non-uniform surfaces Langmuir, 23(7) 3820. The effects are due to the nonuniformity at the contact line, not the contact area. cosθ rough cosθ = f cosθ + f cosθ c For air pockets: 1 1 2 2 cosθ = f cosθ + f 1 c 1 1 1 Combining gives: smooth cosθ = f cosθ + f 1 c = r cosθ 1 smooth 1 12
Superhydrophobic surfaces Many superhydrophobic surfaces are unstable. Dorrer and Ruehe, Langmuir, 23(7) 3820. 13
Nanoparticle ACS National Meeting April 9 10, 2008 New Orleans 14
Nano is research and development at the atomic, molecular or macromolecular levels, in the length scale of approximately 1 100 nm National Science Foundation 15
Common nanoparticles Silver: catalysis, photographic processes CdSe: optoelectronics, photoluminescence Gold: optoelectronics, electronics, biosensors Silica: insulators, catalyst supports, membranes, filling material Palladium: catalysis TiO 2 : photoelectrochemistry Metal oxides: Mg, Ca, Mn, Fe, Co, Ni, Cu: magnetic properties Polymers: conducting composites, drug delivery Rigoberto C. Advincula, University of Houston 16
Nanoparticle synthesis - nanoreactors Micro-structures in condensed phases are sometimes used: zeolites, layered solids, molecular sieves, micelles/microemulsions, gels, polymers, and glasses Heinrich Hofmann, Swiss Federal Institute of Technology,EPFL Lausanne, Switerland 17
Surfactant phases Semiconductors - CdS nanoparticles and nanotriangles Coprecipitation Oxides - V2O5 nanorods and nanowires - Hydrolysis- Condensation Metals - Silver nanoparticles and nanodisks - Reduction Nicola Pinna, Max Planck Institute of Colloids and Interfaces 18
Surface modification of nanoparticles Rigoberto C. Advincula, University of Houston Grafting from is preferred to achieve high brush density: average between grafting points < radius of gyration (Rg). 19
Surface modification 20
Quantum dots CdSe CdSe Quantum Dots from the Bawendi group at MIT. Christopher B. Murray, IBM Research 21
Arjun G. Yodh, Department of Physics & Astronomy, University of Pennsylvania Entropic forces from nanoparticles (1) 22
Arjun G. Yodh, Department of Physics & Astronomy, University of Pennsylvania Entropic forces from nanoparticles (2) 23
Schematic Diagram of Chemical Mechanical Polishing Downforce Carrier Pad Conditioner Retaining Ring Slurry Pad Polish Platen Ara Philipossian Intel Corporation NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing 1 24
Effect of Abrasive Geometry on ILD Polish Performance Slurry Appx. Primary Particle Size (nm) Appx. Mean Aggregate Size (nm) Normalized Mean Removal Rate Normalized WIWNU (3-sigma) A 29 122 86 -- B 29 110 100 100 C 19 95 82 83 D 20 110 79 154 E 50 200 94 104 NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing Ara Philipossian Intel Corporation - Fumed silica abrasive - Constant ph and abrasive content - Comparable defect density and planarity 25
Convective assembly by dip-coating Orlin D. Velev Department of Chemical Engineering North Carolina State University 26
Rapid deposition of 2D crystal coating of particles Orlin D. Velev Department of Chemical Engineering North Carolina State University 27
Structured metallic films via colloidal crystals Orlin D. Velev Department of Chemical Engineering North Carolina State University 28
Nanotoxicology A worry DDT cured malaria - Endangered birds Pesticides improved crop yields - Toxic to animals Refrigerants made houses cool - Lead to ozone hole Asbestos improved insulation - Liability expenses Is size dangerous? Dr. Vicki Colvin Director, CBEN Professor of Chemistry Rice University 29
Scaling relations ACS National Meeting April 9 10, 2008 New Orleans 30
Characteristic times and forces Characteristic times (seconds) Force Time scale Sphere radius 10-2 μm 1 μm Brownian a 2 / D 10-6 10-2 Viscous ρa 2 / η 10-10 10-6 Convection a/ U 10 2 1 Characteristic forces (N/m 2 ) Force Force scale Sphere radius 10-2 μm 1 μm Brownian kt/d 10-13 10-15 a = sphere radius D = Diffusion coefficient ρ = density η = viscosity U = fluid velocity kt = Boltzmann factor A = Hamaker constant ε = dielectric constant ε0 = permittivity of free space ζ = zeta potential 0 Viscous 6πη au 10-20 10-14 Dispersion A/a 10-12 10-14 Russel, pp 9-12. 2 Electrostatic εε0ζ 10-12 10-12 0 36
Information resource for nanotechnolgy http://nanoparticles.org John Texter, University of Eastern Michigan 37