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Top-Down Nanomanufacturing

Top-Down Nanomanufacturing. David T. Shaw State University of New York at Buffalo. Contents. Introduction Learning bottom-up synthesis from nature Self assembly Hierarchical assembly Building blocks. Introduction. How Do You Naomanufacture?. Sculpt’ from bulk Lithography Etching

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Top-Down Nanomanufacturing

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  1. Top-Down Nanomanufacturing David T. Shaw State University of New York at Buffalo

  2. Contents • Introduction • Learning bottom-up synthesis from nature • Self assembly • Hierarchical assembly • Building blocks

  3. Introduction

  4. How Do You Naomanufacture? • Sculpt’ from bulk • Lithography • Etching • Ion beam milling • Ball milling • Assemble Nanoscale building blocks (BBs) • nanocrystal Synthesis • Vapour Deposition • Sol-gel • Pyrolysis • Self assembly

  5. Top-down Fabrication for Moore’s Law of Miniaturization

  6. Integration of Top-down and Bottom-up nanomanufacturing Integrated multifunctional nano-assembly onto bio-MEM devices and lead to scalable and cost effective nanomanufacturing X. Zhang et al, Journal of Nanoparticle Research 6: 125–130, 2004.

  7. Future Integrated Nano-Systems Bottom-up (sensors, memories, etc.) will be integrated with top-down nanocomponents C. Sun, X. Zhang UC Berkeley

  8. Future Development of Information Technology

  9. Dip Pen Nanolithography

  10. Strategies for Nanostructure Fabrication Two complimentary strategies can be used in the fabrication of nanostructures: top-down and bottom-up approaches. J. Mater. Chem. 2004, 14, 459-468

  11. Strategies for Making “Things” M. Boncheva and G. M. Whitesides, MRS Bull (30) Oct 2005

  12. Strategies for Making “Things” • The general scheme of “making things”, at size scales ranging from nanometers to kilometers, includes fabri- cation by hands and robots, photolithography, STM writing. • Things, however, can also be made in a different way: that is, by self-assembly. • “Self-assembly” was originally defined in molecular systems as a process in which molecules or parts of molecules spontaneously form ordered aggregates, usually by non-covalent interactions.

  13. Self-assembled “Things” Of Different Scales (a) A hollow TiO2 colloidal crystal; (b) An asymmetric, 3D silicon micro- mirror formed from a planar precursor by surface tension-powered selffolding; (c) A large-area array of silicon segments self-assembled on a flexible, nonplanar support; (d )An elastomeric globe self-assembled from a flat, 2D projection of the Earth; (e) A simple 3D electrical circuit surrounding a spherical cavity; (f) A self- assembled simple-cubic lattice of brass beads. The inset shows a detail of the structure. M. Boncheva and G. M. Whitesides, MRS Bull (30) Oct 2005

  14. Learning Bottom-up Synthesis From Nature

  15. Zaremba, Chem Mater (96) Organic Films Sarikaya et al, Nature Materials (03) Calcium Carbonate Platelets Examples Of Self Assembled Bionanomaterials Natural biomaterials contain layered, tough biocomposites that have yet to be duplicated in the lab.

  16. 4 nm 4 nm Examples Of Self Assembled Bionanomaterials Vukusic et al, Nature, 01

  17. Nature’s Examples Of Self Assembled Nanostructures

  18. Nature’s Examples Of Self Assembled Nanostructures

  19. Nature’s Examples Of Self Assembled Nanostructures

  20. Self-Assembled Biological Machines

  21. Bottom Up Nanomanufacturing – Self Assembly

  22. Bottom Up Nanomanufacturing – Self Assembly • Spontaneous organization of building blocks with dimensions ranging from nanometers to microns. • Two prominent components: • Building blocks -- size, shape, surface structure • Interactive forces between building blocks

  23. Bottom Up Nanomanufacturing – Self Assembly A challenge for perfecting structures made by self-assembly chemistry is to find ways of synthesizing BBs not only with the right composition but also having the same size and shape. • Ideally, BBs should be monodisperse. Most BBs, however, have some degree of polydispersity. • Any deviation from monodispersity in size and shape would lead to defects in the assembled system. • Equally demanding is to control surface structure of BBs, including charge and functionality. Surface properties will control the inter- actions between BBs.

  24. Benefits of Self Assembly

  25. Building Blocks (BBs) and Self Assembly Many factors must be considered when we approach the bottom-up nanomanufacturing by self assembly – including BBs, forces on BBs, and functional nanotechnological applications. Forces on BBs

  26. Strategies for Nanostructure Fabrication • Bottom-up approach for nanostructures using nano- particles as building blocks • Example: Opals: The fascinating interference colors stems from Bragg diffraction of light by the regular lattice of silica particles 100-500 nm in diameter.

  27. Attractive Features of Self-Assembly • Self-assembly proceeds spontaneously • The self-assembled structure is close to thermodynamic equilibrium • Self-assembly tends to have less defects, with self-healing capability

  28. Why Should We Deal With Self Assembly? • Like atoms or molecules, nanocrystals can be treated as artificial atoms and used as the building blocks of condensed matter. • Assembling nanocrystals into solids opens up the possibilities of fabricating new solid-state materials and devices with novel or enhanced physical and chemical properties, as interactions between proximal nano- crystals give rise to new collective phenomena.

  29. Stabilization Of Colloids • Fundamental problem: The thermodynamically stable state of metals, semiconductors, and polymers is bulk material, not colloidal particles. Stable colloidal dispersions require an interfacial stabilizer, which is a chemical that reduces the interfacial free energy between the particle and the solvent and makes short range forces between the particles repulsive. R. P. Andres Science (1996)

  30. Gold Colloidal Nanoparticles • In the case of our gold nanoparticles, the stabilizer is citrate ion, whose negative charge is opposite to that of positive gold ions on the particle surface. The excess negative charge due to adsorption of citrate on the surface of the particles makes the particles repel one another. Our polystyrene latex also is charge stabilized. Dissociation of a fraction of the sodium ions of the sodium 4-styrenesulfonate units of the poly-mer leaves the particles with a negative charge. • The stabilizer often is a surfactant, which is a chemical compound such as sodium dodecyl sulfate (SDS) whose structure has one end that is chemically attracted to the particle and the other end chemically attract-ed to the solvent. However, there are no sur- factants in our gold nanoparticle and polystyrene latex preparations. R. P. Andres, Science (1996)

  31. Self-Assembled Monolayers (SAMs) • Ordered molecular aggregates that form a monolayer of material on a surface. • Formation of SAMs: Alkyl thiols RSH react with Au(0) surface, forming RS-Au(I) adducts: • If R is a long chain, van der Waals interactions between the RS units lead to the formation of a highly ordered monolayer on the surface. • The thermodynamic stability of SAMs increases with the length of the alkyl chain.

  32. Substrate and Ligand Pairs for Forming SAMs

  33. Alkanethiolate SAMs on Gold Surfaces

  34. SAMs Based on Polymer BBs A film formed by the triblock molecules, revealing regularly sized and shaped aggregates that self assemble into monolayer nanostructures. Stupp et al, Science( 97)

  35. Solution-based Molecular Manipulation for BBs Synthesis Mesoporous molecular nanostructures are used as templates for nanocrystal synthesis. Phase sequence of surfactant-water binary system

  36. Self-Assembly of Surfactant (Soap) Molecules

  37. Self-Organized Nanostructures Regularly sized and shaped nanostructures can be tiled into superlattices of varying geometries and symmetries. Stupp et al, Science(97)

  38. Hierarchical Assembly

  39. What is Hierarchical Assembly? • A characteristic feature of self-assembly is hierarchy. • Primary building blocks associate into more complex secondary structures that are integrated into the next size level in the hierarchy. • This organizational scheme continues until the highest level in the hierarchy is reached.

  40. Driving Forces on Various Scales • Molecular Scale: H-bonding, hydrophoic interaction, electrostatic forces, “lock-key” type interactions, and van der Waals forces • Nano- and Mesoscale: capillary forces, external fields (gravitational, centrifugal, magnetic, electric, optical, …… ), surface tension, electrostatic forces, shear forces, and molecule-based interactions

  41. Driving Forces: Attractive vs. Repulsive

  42. Template-Assisted Assembly • Aqueous dispersion of colloidal polystyrene or silica particles are assembled on a solid surface patterned with relief structures. • These patterned structures are used as templates for assembling of a variety of nano-particles Yin et al., J. Am. Chem. Soc. 2001, 123, 8718

  43. Surfactant-Assisted Assembly • Assembly of CeO2 nanoparticles (5 nm) into hierarchically structured nanoporous materials using block copolymers. • The force between particles (Van der Waals force) is weak, surfactants are used to provide the necessary bonding to form self-assembled nanoporous materials. Corma et al., Nat. Mater. 2004,3, 394

  44. Charge-Driven Assembly Assembly of negatively charged gold and silica nanoparticles into hollow microspheres directed by positively charged poly (L-lysine) Murthy et al., J. Am. Chem. Soc. 2004,126, 5292

  45. Self-Assembly of Nanoparticles to Superlattices • Nanocrystals are able to assemble into close-packed ordered superlattices under the following conditions: • narrow size distribution (< 5%) • surfactant that is strong enough to separate the individual nanocrystals • slow drying rate so that the nanocrystals can move to suitable positions Schematic illustration of self-assembled, passivated nanocrystal superlattices of spherical (a) and faceted (b) particles Wang, Adv. Mater.1998,10,13-30

  46. Self-Assembled Nanocrystal Superlattices • Solid, periodic arrays composed of nanocrystals and surfactants have been synthesized into one-, two- and three-D superlattices. • Very narrow size distribution of weakly interacting nanocrystals: • The narrower the particle size distribution, the easier it is to obtain long-range superlattice ordering. • Delicate interplay between interparticle attractions strong enough to drive superlattice crystallization, yet weak enough to allow annealing. • The macroscopic properties of the nanocrystal super-lattices are determined not only by the properties of each individual particle, but also the interaction/coup-ling between the nanocrystals interconnected and isolated by a monolayer of thin organic molecules. Wang, Adv. Mater.1998,10,13-30

  47. “Lock-and-key” Assembly Schematic representation showing possible approaches to the directed self-assembly of metallic (1. and 2.), and bimetallic (3.) macroscopic materials using antibody/anti-gen cross-linking of inorganic nanoparticles. Shenton et al, Adv Mater(1999)11,449-452

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