13 What drives self assembly? Static assembly (thermodynamic free energy minimum) -- once formed it is stableDynamic assembly (kinetically formed, not necessarily thermodynamic minimum) -- not necessarily stableForces of chemical bonding (4)covalent, ionic, van derWaals, hydrogenOther forces (magnetic, electrostatic, fluidic, ...)Polar/Nonpolar (hydrophobicity)Shape (configurational)Templates (guided self assembly)Kinetic conditions (e.g., diffusion limited)
14 Excerpt from Letter of Benjamin Franklin to William Brownrigg (Nov ...At length being at Clapham, where there is, on the Common, a large Pond ... I fetched out a Cruet of Oil, and dropt a little of it on the Water. I saw it spread itself with surprising Swiftness upon the Surface ... the Oil tho' not more than a Tea Spoonful ... which spread amazingly, and extended itself gradually till it reached the Lee Side, making all that Quarter of the Pond, perhaps half an Acre, as smooth as a Looking Glass....A nanofilm!
15 Langmuir Film of an amphiphilic molecule water hydrophobic end e.g., steric acidpressureof an amphiphilicmoleculemonolayer filmwaterhydrophilic end
16 Langmuir-Blodgett Film solidMust control movablebarrier to keep constantpressuremultiple dips -multiple layersliquid
17 SAM: Self Assembled Monolayer alkanethiol on gold (Au)HS(CH2)nXwhere X is the end group of the chain–CH3, –OH, or –COOHLonger alkanethiol molecules have greater thermodynamic stabilityReview article: J.C. Love, et al., Chem. Rev. 2005, 105, 1103(G. Whitesides group, Chem Dept, Harvard)
18 SAM: Self Assembled Monolayer moleculesfrom solutionsolidChemisorbed moleculesStabilized by intermolecular van der Waals interaction
19 SAMs on Nanoparticles gold NP There are now many configurations and uses of SAMsimperfect packingJ.C. Love, et al., Chem. Rev. 2005, 105, 1103
20 Nanoparticle Monolayer Formed at a Liquid-Air Interface
21 Nanoparticle Monolayer Formation tolueneNature Materials MOVIERequirements:rapid evaporationexcess dodecane presentattractive interation to liq-air interface and between particles
22 SELF ASSEMBLY with DIBLOCK COPOLYMERS Block “B”Block “A”PSPMMA~10 nmScale set by molecular sizeOrdered Phases10% A30% A50% A70% A90% A
23 Versatile, self-assembling, nanoscale lithographic system CORE CONCEPTFOR NANOFABRICATIONDepositionTemplateEtchingMaskNanoporousMembrane(physical orelectrochemical)Remove polymerblock within cylinders(expose and develop)Versatile, self-assembling, nanoscale lithographic system
25 Improving Order: Guided Assembly in a Trench: Graphioepitaxy side viewassemble hereUMass-Seagatetopview
26 Nanomagnets in a Self-Assembled Polymer Mask nanoporous template1x1012 magnets/in2Pulse reverse electrodeposition results in improved microcrystalline structure and improved magnetic properties (larger perpendicula magnetocrystalline anisotropy)Data Storage......and More
27 Metal Nanorings Ferromagnetic cobalt rings as small as 15 nm OD Extracted from a paper in preparation “Nanoscopic Metal Rings Fabricated Using a Self-Assembled Template” by Deepak Singh (Physics), Qijun Xiao (Physics), Robert Krotkov (Physics), Hongie Xiang (PSE), Ting Xu (PSE), Thomas Russell (PSE) and Mark Tuominen (Physics). In magnetic applications the nanoscopic rings are promising for data storage and spintronic applications because of their favored magnetic vortex state. The rings offer promise for new plasmonic and negative refractive index applications.Ferromagnetic cobalt ringsas small as 15 nm OD
28 Kinetic Self-Assembly - by Breath Figures Polystyrene FilmMohan Srinivasarao, et al. Science 292, 79 (2001).
29 More Fabrication by Breath Figures a, Breath-figure pattern obtained with pure polystyrene. b, Optical and c, confocal fluorescence microscope images of different areas of a sample obtained from solvent-casting a polystyrene film from chloroform with CdSe nanoparticles. Scale bars: 16 mum. The inset in c shows a fluorescence intensity scan along the line indicated.UMass: Alexander Böker, Yao Lin, Kristen Chiapperini, Reina Horowitz, Mike Thompson, Vincent Carreon, Ting Xu, Clarissa Abetz, Habib Skaff, A. D. Dinsmore, Todd Emrick and Thomas P. Russell, Nature Materials 3, (2004)
31 Proposed AAO Growth Mechanism Al2O3EAlAl3+O2-Density mismatch between Al and Al2O3Some Al3+ goes to solutionMechanical stress yields pore growth in uniform hexagonal arrayPore diameters of~ nm possibleby choice of anodizationconditionsFigure adapted fromJessensky, Müller, & Gösele, Appl. Phys. Lett. 72, 1173 (1998)
32 Improving AAO Order at Surface SiC stampAluminumanodizee.g., Masuda et al., Appl. Phys. Lett 71, 2770 (1997);Choi, et al., J. Vac. Sci. Tech. B 21, 763 (2003)
33 Ni in Anodized Aluminum Oxide Template SEMMFMNielsch, et al. Appl. Phys. Lett. 79, 1360 (2001).
34 Large Scale Self-Assembly (Geological) Giant's Causeway(Northern Ireland)Volcanic basalt cooled rapidly to form these (mostly) hexagonally shaped columns
35 Microfluidic Assembly Application: RFIDAlien Technologyflow directionParts, having unique shape, are delivered via fluid flow to mating pockets on an assembly substrate.Nanoscale Phase SeparationIBM "air gap" technologyIntroducing nanoscale air pockets into the insulating material separating wires on a computer chip -- lowers the capacitance
37 Using Synthetic DNA for Designer Structures Designer DNA molecules can be synthesized chemically, and allowed to assemble into a specific configuration of lowest energy.Ned Seeman, NYU
38 Programmed DNA Folding to Make "DNA Origami" P.W.K. Rothemund, Nature 440, 297 (2006)
39 Additional examples to amplify concepts balls in a boxmagnetscrystallizationForces (non-directional or directional), shape, thermal agitationNanoscale self assemblycoffee stainnanoparticle assembly by dropletothers