Nanotechnology Concepts and Particle Sizes

Nanotechnology

• Nanoparticles are generally 1-100 nm in size
• Nanoscale ranges from 1 to 1000 nm
• Particle size classification corresponds to different materials

Particle Size Classification

• 1 nm: Chemical drug
• 5 nm: Protein
• 10 nm: DNA
• 20-50 nm: Blood vessel pore
• 50 nm: Carbon nanotube
• 100-500 nm: Liposome nanoparticle
• 1000 nm (1 µm): Bacteria
• 10 µm: Cell
• 50 µm: Human hair

The Scale of Things - Nanometers and More

• Different scales of size, natural and man-made
• Includes various objects, from dust mites to human hair, and from gears to atoms

Titanium Dioxide Nano Powder

• Image of a white powder in a small, white bowl

Quantum Confinement Effect

• Quantum confinement effect happens when particle size is comparable with the electronic wave function
• Effects changes in the energy of electrons within a particle
• This phenomenon is known as the quantum size effect

Quantum Confinement Structures

• Quantum Confinement is described by quantum number
• Classification based on confinement dimension (Bulk, 2D sheet, 1D wire, and 0D dot)

Quantum Confinement and Particle Size

• Quantum confinement reduces as a particle's size increases.
• Decreasing size causes change in the bandgap, thus producing a blue shift in optical illumination.

Quantum Dots

• Quantum dots are semiconductors where excitons are confined in all three dimensions
• Quantum dots exhibit size-dependent properties
• Larger dots emit redder light while smaller dots emit bluer light.
• Quantum Dots are used to generate different colors

Tunnel Effect

• The transmission coefficient (T) is related to the particle's energy (E) and the potential barrier (V₀)
• Tunneling occurs even if the particle energy is less than the potential barrier
• The tunneling effect is described as having a finite probability

Tunneling Microscopy

• Tunneling Microscopy exploits the quantum effect of "barrier penetration" to measure a material's surface electron density
• The method uses tunneling voltage and distance control with scanning unit.