September 23, 2011. Background What is nanoscience? What is considered nanoscale? What is the...

September 23, 2011

Background

Background

What is nanoscience? What is considered nanoscale? What is the significance?

Fullerene (C60, D<5nm)

Nobel Prize in Chemistry 1996

Harold Kroto, Robert Curl & Richard Smalley (Rice University)

Graphene

Nobel Prize in Physics 2010

Andre Geim & Konstantin Novoselov (University of Manchester)

Carbon Nanotubes (D ~ 4 nm)

Quantum Dots (5 to 50 nm)

Gold Nanoparticles

HeLa cells with fluorescent gold nanoparticles

(Dr. Mengxiao Yu and Dr. Jie Zheng – UT Dallas).

Background

Properties of Light

Light is a wave (Electromagnetic (EM) radiation)

Waves have 3 features Wavelength (λ) Amplitude Frequency (ν)

EM radiation = continuous spectrum of all wavelengths (no gaps).

Electromagnetic Spectrum

Equations of Light

c = λν, c is the speed of light (m/s), λ is the wavelength (m) , ν is the frequency (s-1)

∆E = hν h is Planck’s constant (J s) ν is the frequency (s-1)

∆E = (hc)/λ

When light hits an object… Different wavelengths can be…

Absorbed Transmitted (allowed to pass through) Reflected

…depending on the wavelengths of light, object’s chemical composition, and its size.

Color Wheel

Object absorbs orange = blue color observed.

No light absorbed = all are reflected or transmitted (white light).

All wavelengths are absorbed = black color observed.

How to separate light

Prism Diffraction

Figure 5: Diffraction of light (pg 25) w(sinθn) = nλ tan(θn) = yn/L

Purpose

Measure the width of a single hair using a laser pointer and diffraction.

Synthesize Ag NPs, and investigate how color is related to particle size.

Materials

Laser pointer Measuring tape Scotch tape Hair Stock solutions (Sodium citrate, silver

nitrate, hydrogen peroxide, potassium bromide, sodium borohydride)

Large test tubes Stoppers or parafilm to seal test tubes Spectrophotometer Cuvettes (2 to 5)

Safety

Wear goggles and gloves! AgNO3 is corrosive

NaBH4 is flammable and toxic (inhalation, absorption and ingestion)

Sodium Citrate may irritate skin, etc. Hydrogen peroxide is corrosive and

causes burns to eyes, skin etc. Don’t play with the laser pointers!