Laboratory 04 Light and Nanotechnology : How Do we “See” Something Too Small to See?

1. Laboratory 04 Light and Nanotechnology : How Do we “See” Something Too Small to See?

2. Objectives • Measure the width of a human hair using a laser pointer and diffraction. • • Synthesize silver nanoparticles, and investigate how color is related to particles.

3. Nanotechnology Nanotechnology is the technology for design, fabrication and manipulation of nanometre scale systems, in the scale of 1-100 nm

4. How Small is nano ? 1 µm = one millionth of a meter 1 nm = one billionth of a meter ≈ 1/50,000 thickness of a hair! ≈ a string of 3 atoms If we shrunk all distances by 110,000,000,000 X The sun and earth would be separated by 1 m A football field would be 1 nm Human hair thickness ~ 50 µm 110 m 110,000,000 km

5. Why Nanomaterials ? High Aspect ratio Quantum Effect

6. Properties of Nanomaterials Enhanced electrical and heat conductivity • Increased strength, tensile properties • Magnetic properties • Optical properties – color changes with size

7. Silver Nanoparticles Size: 10nm-100nm Chemical formula: Ag Details: Silver nanoparticles are ultra fine particles of silver. They are ten to a hundred nanometers large, and differ from the bulk silver as they have different colors such as yellow, as opposed to the silver. This is due to plasmon absorbance: Incident light rays create oscillation in free electrons on the surface of nanoparticles, causing them to absorb electromagnetic radiation, creating different colors reflected.

8. Synthesis of Silver nanoparticles Reduction method Ag + → Ag (Reducing agent NaBH4) Ag atoms will stick together to form small particles. Addition of citrate- Act as a buffer to control pH Act as a binding agent to limit the growing of nanoparticls Addition of hydrogen peroxide- Act as a etching agent , remove silver atoms from less stable nanoparticles. Silver nanoprism is formed. Bromide is added to control the size of the nanoprisms.

9. Diffraction of light through a single slit y W L w sin Ɵ = n λ tan Ɵ = y / L In this lab, a variation of single slit diffraction is used to measure the width of a human hair; instead of a single slit in a wall.