international institute for nanotechnology nanoscale science & engineering center for integrated...

International Institute for NanotechnologyNanoscale Science & Engineering Center for Integrated Nanopatterning and Detection TechnologiesNorthwestern University

Nanotechnology:

BIG Ideas From Small Things

Mike Davis – Harold Washington CollegeRET Director: Northwestern University


Outline

Brief Overview of Size and Scale Making Nanoparticles Arranging Nanoparticles Lithography Nanotechnology in Education Nanostructures – Gallery


Nanotechnology - Basics

Techniques that produce, manipulate or arrange particles that are less than 100nm in their largest dimension.

One nanometer is 1 billionth of a meter.

‘1 nanometer is the length a man’s beard grows when he picks up the razor’


Nano Buzz


Nanotechnology – Surface Particles

Individual atoms can exhibit quantum effects. Groups of atoms can start to exhibit collective effects,

but are too big to have noticeable quantum effects. As particles get bigger, the number of particles on the

surface relative to the particles in the interior gets smaller.

Nanotechnology happens when the number of particles on the surface is similar to the number of particles in the bulk.


Nanotechnology – Total number of Particles

Particle Size vs. Surface Percentage

0

20

40

60

80

100

120

0 5 10 15 20 25

Particles Size (length of a side nm)

Per

cent

age

Sur

face

Par

ticle

s


Nanotechnology – More than a size


Nanotech - Computing

Moore’s Law Doubling the

number of transistors on an integrated circuit every two years.

Enormous increase in computing power and memory.


iPod Nano


Demonstration

Bulk properties – Liquid Phase Reaction

Surface Properties – Gas Phase Reaction


Gold Nano Particles

As these particles get larger, their color becomes more blue in appearance.


Making Gold Nanoparticles

Chemical Reaction

– Solvated form of the metal (gold or silver)– Introduction of a reducing agent (citrate or borohydride)– Slightly elevated temperature

Control over particle size (monodispersion)

– Light conditions– Temperature conditions– Stabilizing media


Carbon Nanotubes

Made by passing an electrical arc between two graphite rods.

Seeded by small amounts of metal.

Can be grown to specific lengths, diameters, and wall thickness.

Stronger than steel. Electrically in some

configurations. Semiconductor in other configurations. Chiral in other configurations.


Nanoparticle Synthesis – Wet Chemical

Chad Mirkin – Northwestern University


Nano Printing Press – Micro contact Printing

A technique for modifying surfaces with a high degree of control.

Hydrophobic and hydrophilic regions on a gold surface (CDRs)

Inexpensive method to demonstrate a simple process.

Commonly used technique for surface modification.


Nano Printing Press – Microcontact Printing

Expose a gold surface on a CDR.

Pattern the surface with a hydrophilic organic molecule.

Dip the patterned surface in a solution with a hydrophobic organic molecule.

Dry the surface. Cool the surface below the

dew point. Observe the areas where

water condenses.


Nano Printing Press

Science is based on a strong bond between gold and sulfur (thiol).

Long organic molecule ends in something either hydrophilic or hydrophobic.

Microcontact printing uses a stamp made by pouring an elastic polymer over a mask.

Finer mask, finer features, more control.


Multiple Nano Features with One Mask


Micro Contact Printing with Biological Samples - Whitesides


Nanoparticle Synthesis – Surfaces

Prepare a surface that has a pattern on it.

Use those patterns for growing crystals.

Teri Odom – Northwestern University


Instrumentation – Visualizing the Nanoscale

Most nanofeatures are smaller than the visible wavelengths of light.

Can’t use visible light to determine surface features.

Electron microscopy (wavelength smaller than light)

Force micrscopy (no light used).

Tools of the trade.


Scanning Tunneling Microscope

A very sharp tip is brought near a surface.

A voltage is applied between the surface and tip.

Current is measured on the surface to determine the size and shape of features.

STM can resolve features that are 0.1nm wide and 0.01nm high.

Atomic resolution.


Atomic Force Microscopy (AFM)


Nano-Analogy


Nano – Analogy


Lithographic Techniques – Solar Photography

Photo sensitive paper– Mixture of iron salts

Place an opaque object over the paper.

Expose the paper to light.– Opaque objects block out the

light and expose the rest of the salts.

– Exposed iron salts form an insoluble salt.

– Unexposed salts are water soluble.

Remove the object. Wash.


Lithographic Techniques in Nanotech

Techniques that build nanostructures or arrays.

Bottom – up approach– Prepare areas on a surface

– Utilize self assembly to build up from that point.

Top – down approach– Prepare a surface and etch

into it.

– Can involve some light based photochemistry.


Lithographic Techniques in Nanotech – Top Down Approach

Forming arrays of nanopyramids.

Colloidal crystal of nanospheres on a surface. (Mask)

Thermally deposit metal onto the top of the surface and the sphere mask.

Remove the sphere mask. Look at the pretty remaining

structures.VanDuyne – Nanoletters 2007


Colloidal Crystals – Chiang MIT

282 nm 356 nm

482 nm 424 nm


Colloidal Crystals – Chiang MIT

STM Images of Layers of Polystyrene Spheres on a Silicon substrate. Opals.


Nanolithography – Bottom Up Approach

Pattern a surface with something.

Allow other species to assemble there spontaneously.

Grow upwards from the base. Whitesides – approach to

paper based telemedicine.


Nano in the Environment

Nanoparticles being made end up being released into the environment.

Unicellular and multicellular organisms pick up the particles.

Silver nanoparticles are antimicrobial.

What are the long term effects of exposure?


Nano in Commercial Products

Sunscreen (TiO2 and ZnO)

Silver in bandages. Silver in plastic food

containers. Nanoscale fabrics on

stainresistant clothing. Carbon nanotubes in sporting

equipment. Particles in stained glass.


Nano-Imagination - Robots


Nano-Imagination – Robots in the Blood

False – Blood Robots True – Nanoparticles to Treat Tumors


Nano-Imagination – Reproduction


Nano - Resources

NISE-Net: Network of Informal Educators and Researchers (nisenet.org).

MRS Nano Days:Free digital and physical activities for kids and adults. (nisenet.org/nanodays/2010)

National Lab Day: Localized resources for teachers. (Nationallabday.org)

Nanohub: Online resource for computational nanotech (nanohub.org)

iLabcentral: Forum for shared instrumentation. Nanotech coming. (ilabcentral.org)


Nano Resources Students - REU

Summer Research Experience for Undergraduates.

Spend the summer working in a lab group.

Potential for a publication. 8 – 10 weeks. On campus housing Stipend ~$4,500 REU sites all over the US www.nsec.northwestern.edu/

REU Applications due in Feb.


AcknowledgementsKathy Cook

Margaret Connolly

NSF – EEC 0118025 / NSF – EEC 0647560

Questions / Concerns / Comments

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