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SYNTHESIS AND ASSEMBLY Slide 2 Size Dependent Properties Slide 3 Electronic Energy Band Slide 4 Slide 5 For example, 5 cubic centimeters about 1.7 cm per side of material divided 24 times will produce 1 nanometer cubes and spread in a single layer could cover a football field Repeat 24 times Nanoscale = High Ratio of Surface Area to Volume Source: Clayton Teague, NNI Slide 6 Slide 7 Nanoscale sizes can lead to different physical and chemical properties -Optical properties -Bandgap -Melting point -Surface reactivity Even when such nanoparticles are consolidated into macroscale solids, new properties of bulk materials are possible. -Example: enhanced plasticity Size Dependent Properties Slide 8 The melting point of gold particles decreases dramatically as the particle size gets below 5 nm Source: Nanoscale Materials in Chemistry, Wiley, 2001 Melting Point Slide 9 Top-Down and Bottom-Up Processes Slide 10 Nanoparticle Synthesis Slide 11 Slide 12 Slide 13 Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Slide 22 Slide 23 Slide 24 Slide 25 Slide 26 Slide 27 Quantum dots change color with size because additional energy is required to confine the semiconductor excitation to a smaller volume. Ordinary light excites all color quantum dots. (Any light source bluer than the dot of interest works.) Source: Bala Manian, Quantum Dot Corp. Optical Properties Slide 28 Material band-gap determines the emission range; particle size tunes the emission within the range Nanocrystal quantum yields are as high as 80% Narrow, symmetric emission spectra minimize overlap of adjacent colors Source: Bala Manian, Quantum Dot Corp. Optical Properties Slide 29 Core/Shell Heterostructure QDs Slide 30 Slide 31 Slide 32 Slide 33 Slide 34 Slide 35 Slide 36 Slide 37 Slide 38 Slide 39 Slide 40 Gas Phase Synthesis Slide 41 Slide 42 Slide 43 Slide 44 Slide 45 Slide 46 Thin-Film Synthesis of QDs Slide 47 Slide 48 Slide 49 Slide 50 Slide 51 Slide 52 Slide 53 Slide 54 Slide 55 Dendrimers Slide 56 Dendrimers consist of a series of chemical shells built on a small core molecule. Each shell consists of two chemicals, always in the same order and is called a generation http://nano.med.umich.edu/Dendrimers.html# dendrimer_introduction G0 G1 G2 G3 http://www.ninger.com/dendrimer/ Slide 57 http://www3.interscience.wiley.com/cgi-bin/fulltext/106558159/PDFSTART Slide 58 The dendrimer (blue and red) attaches to multiple receptors (pink) on cell membranes or other biological structures such as a virus. The dendrimers (blue and red) in VivaGel interact with protein structures (yellow) on the surface of HIV, blocking the interaction of HIV (purple) with healthy human cells (pink) that results in HIV infection. Illustrations courtesy of Starpharma Pooled Development, Ltd http://www.smalltimes.com/document_display.cfm?document_id=6691 Dendrimers Fighting the Spread of Diseases Slide 59 Drug Delivery http://www.davidwang.homestead.com/files/Drug_delivery.pdf http://www.umich.edu/news/?Releases/2004/Mar04/r032304 Slide 60 Slide 61 Quantum Dots as Cellular Markers www.qdots.com Slide 62 Self-Assembled Mono and Binary Superlatices Slide 63 GaN Nanowires Slide 64 Vapor-Liquid-Solid Process Slide 65 Different Approaches to Nanowire Processing