Nanotechnology:The Promise and the Hype

Seán Barry,

Nanoscience Working Group,

Department of Chemistry,

Carleton University

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The Scale of “Nanoscale”

1 – 100 nm1x10-9 – 1x10-7 m

across Canada → a centimetre

Microscopy: scanning electron, transmission electron, and atomic force microscopy

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What Nanotechnology is Not

Modern nanotechnology is not the fabrication of tiny mechanical devices the can and will enter human systems to repair or damage cells.

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Real “Nanomotors”

“machine-like” nanoscale behaviour

A tiny blade of gold attached to a carbon “nanotube”, and an electrical current allows it to spin.

Nature 2003 424, 408.

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History of Nanotechnology – First Example

The “Lycurgus Cup” is a Roman artifact from before 640 AD.

It is dichroic, changing colour when illuminated from the inside. This effect is caused by gold and silver nanoparticles, and was likely produced by accident.

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As early as 500 AD, glass artisans were making stained glass windows with vibrant reds and yellows.

These colours were much more luminous and durable than dyes could produce.

They were the products of “coinage metal” nanoparticles imbedded in the glass.

History of Nanotechnology – Stained Glass

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History of Nanotechnology – Coinage Metals

As these nanoparticles get smaller, the colours shift from red, through yellow and green, to blue.

Here is an example of a copper nanocrystal that is roughly 100 nm across.

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In 1827, Joeph Niépse was able to stabilise silver halide nanocrystals in a gelatin that hardened with exposure to light.

The silver halides decomposed to silver metal, producing black.

The crystal grains were too small to be discerned, and so black-and-white photography gave excellently resolved photos.

History of Nanotechnology - Photography

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History of Nanotechnology - Colloids

Nanoparticles “stay in solution”, leading to one of the most enduring images of nanotechnology:

The rainbow array of solutions made by the suspension of a variety of sizes of nanoparticles.

This was discovered by Michael Faraday in 1857.

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Impact of Nanotechnology

The benefit of nanotechnology is the ability to introduce new characteristics from materials:

•Antibacterial behaviour

•Colour

•Conductivity

•Tensile strength

•Chemical behaviour

•Interaction with water

•“Self-cleaning”

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In Canada, there are 80 companies that make 150 products that use 88 different nanomaterials.

Worldwide, there are about 580 products made by 305 companies in 20 countries.

Keep in mind that several of these share a technology, and many others are “reclassified” as nanotechnology.

http://smarteconomy.typepad.com/smart_economy/2008/02/outsourcing-and.html

Impact of Nanotechnology

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The Xbox 360 is one of the most prevalent microelectronic technologies to employ nanotechnology.

The method is “silicon-on-oxide”, which makes 100 nm silicon layers. This allows for a decrease in microelectronic device size, and so an increased density within a chip.

Modern Nanotechnology - Microelectronics

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Zinc oxide and titanium oxide are both employed as opaquesunblocks.

When particles are nanoscale, they become invisible to the human eye, but still reflect UV light.

Modern sunblocks can provide a physical barrier without this classic appearance.

Modern Nanotech - Sunblock

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Modern Nanotechnology – Antimicrobial Fabric

Nanohorizons, a company in thePennsylvania, has startedproducing a silver nanoparticlematerial as both a dye and inpolyester and nylon.

The silver nanoparticles aretoxic to microbes, and socolonies will never form, andclothes using this material will not have odours.

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Nano Dynamics in the US has produced a golf ball incorporating nanotechnology.

Although they are tight-lipped about what the material is, the inner metallic coating is likely nanoparticles of a coinage metal.

The elasticity (and response to a golf club) is different that a traditional core, and this will affect the aerodynamics.

Modern Nanotechnology – Golf Balls

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Newer solar panels nowincorporate “nanocrystalline silicon”. This increases efficiency by“bouncing” the light around.

Upcoming solar cells incorporate nanostructures (rods, ribbons, particles) of different materials to increase the efficiency of these cells.

Future Directions - Solar Panels

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Uncoiled DNA strands arecentimetres long, and are like polymers.

They can be modified to“cross-link” in such a way todefine shapes.

These impressive images are 165 nm by 165 nm.

Future Directions - DNA as a Nanomaterial

Nature 2006, 440(16), 297.

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Singularly Impressive

Nature 2006, 440(16), 297.

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Future Directions - Nanophotonic Sensors

Mines and other enclosed environments could use fibre optic sensors to detect pollutants.

An ultrathin layer of metal (typically a coinage metal) will allow specific polutants to adhere to the surface, but light could still see through to detect them.

This would allow real-time, on-person environmental monitoring.

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Antibodies can be anchored to nanoparticle surfaces to collect specific proteins.

In this example, the nanoparticle is magnetic, allowing it to be separated and analysed.

Nanoparticle Biosensors

Clinica Chimica Acta 2005, 358, 37

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There is an indication that nanoparticles interact with biological systems like molecules.

Nanotoxicity

J. Nanosci. Nanotechnol. 2007, 7, 3048.

Copper Particle number

(per g)LD50

(mg/kg)Toxicity class

Microscale (17 g)

44 5610 Nontoxic Class 5

Nanoscale (23.5 nm) 1. 7×1010 413

Moderately toxic Class 3

Ionic (0.072 nm) 9. 4×1015 110

Moderately toxic Class 3

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consumer exposure

Human and ecological systems

worker exposure

Introduction to Biological Systems

Production(raw)

Production(consumer)

UseDisposal

(end of life)

Industrial and municipaldischarge Landfills and

Incinerators

recycling

EPA Nanotechnology White Paper 2007

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Solutions to Toxicity

Previously, magnetic iron oxide (SPION) was shown to enhance magnetic imaging.

However, normal SPION is toxic.

When coated with a sugar derivative (Pullulan), it was found to be non-toxic.

Biomaterials 2005, 26, 1565.

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Modification and Study

Healthy cells.

Cells incubated with iron oxide nanoparticles.

Cells incubated with pullulan-coated iron oxide

nanoparticles.

Biomaterials 2005, 26, 1565.

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Summary• Nanotechnology is not very new.

• but our ability to image it (and so, modify it) has increased.

• Nanotechnology will modify existing technologies, and enable new ones.

• But (likely) not radically.

• Health applications drastically improve imaging, drug delivery, and many other aspects.

• Health concerns are presently being studied.

• Cautious and well-reasoned employment of nanotechnology will improve quality of life.

• Research (as always) is ongoing.