SYNTHESIS AND ASSEMBLY

Size – Dependent Properties

Electronic Energy Band

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

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

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

Top-Down and Bottom-Up Processes

Nanoparticle Synthesis

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

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

Core/Shell Heterostructure QDs

Gas Phase Synthesis

Thin-Film Synthesis of QDs

Dendrimers

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 dendrimer_introduction G0 G1 G2 G3

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 Dendrimers Fighting the Spread of Diseases

Drug Delivery

Quantum Dots as Cellular Markers

Self-Assembled Mono and Binary Superlatices

GaN Nanowires

Vapor-Liquid-Solid Process

Different Approaches to Nanowire Processing