Nanoscience and Nanotechnology

Ideas for Educators

Why teach nano?

• An active area of research – science “in real time”

• Multidisciplinary

• Interesting applications

• Hooks to basic science

• “Extra-scientific” implications

Challenges

• Possibly unfamiliar subject matter– True boundaries of knowledge may not be

clear except to (some) experts!

• Multidisciplinary

• Centrality of quantum physics

Workshop Goals

• Subject-matter orientation

• Some ideas for teaching

• Lab exercises

• Pointers to additional resources

A Short History of Atomic Ideas

• Earliest formulation due to the Greeks– “atom” = a-tom, Greek for “not divisible”– Pre-scientific

• In Rome: Lucretius (1st century B.C.)

• Out of favor (along with much other learning and scholarship) for almost 2000 years

The Modern Era

• 18th century: Re-introduced by Daniel Bernoulli, Roger Boscovitch

• Dalton: Laws of Definite and Multiple Proportions

• Kinetic Theory– Clausius, Maxwell, Boltzmann; 19th c.

• Brownian Motion– Brown, Einstein, Perrin; early 20th c.

Democritus (~460–380 B.C.)• “Thought experiment”: Subdivide a

piece of gold– Each part is still gold after every division– Claimed there must be some limit; matter is made

of particles that cannot be further divided

• These “atoms” move endlessly in all directions in “the void”

• Determinism?– A relief from capricious and cruel gods

Lucretius (~95–55 B.C.)

• Roman philosopher and poet; student of Epicurus

• Manuscript De Rerum Natura (On the Nature of Things) re-discovered in late 14th century

• Allegedly driven mad by a “love potion” given to him by his wife, committed suicide

…clothes hang above a surf swept shoregrow damp; spread them in the sun they dry again.Yet it is not apparent to us howthe moisture clings to the cloth, or flees the heat.Water, then, is dispersed in particles,atoms too small to be observable.…For surely the atoms did not hold council, assigningorder to each, flexing their keen minds with questions of place and motion and who goes where.But shuffled and jumbled in many ways, in the courseof endless time they are buffeted, driven along,chancing upon all motions, combinations.At last they fall into such an arrangementas would create this universe…

–Lucretius, De Rerum Natura

Early Objections

• Some quasi-religious or philosophical, of course, but some “scientific” ones as well

• How can atoms continue moving for all time without stopping?– According to Aristotle, moving objects come to a

halt unless something intervenes to keep them moving

Early Objections

• The “void” in which atoms supposedly move cannot exist, according to some philosophers:– For anything to exist it must have a name, which

refers to something rather than nothing– Since “nothing” cannot have such a name, it

therefore cannot exist

Atomic Theory

• Key strands of evidence from both physics and chemistry…

If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis … that all things are made of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.

– Richard Feynman

John Dalton (1766-1844)

• British chemist and physicist

• The foremost proponent of atomic theory– all elements are composed of

indestructible atoms– all compounds are simple

combinations of atoms

• Law of Multiple Proportions (1803)

Dmitri Mendeleyev

• One of several to see the patterns in the properties of the elements

• Predicted the existence (and properties) of several then unknown elements!

Discovery of the Elements

1750 1800 1850 1900

elements predictedby Mendeleyev

Mendeleyev's Periodic Table

Otterbein

oxygen

year

What is Heat?• A central part of the mystery

• Majority view around 1800: heat is a fluid, called caloric

• It flows from hotter bodies to colder ones– E.g. we drop a hot horseshoe in water; caloric

flows from the shoe into the water, cooling the shoe and heating the water

• Mysterious, undetectable (?)

Kinetic Theory• In the atomic theory, heat has to do with

the (random) motion of the particles– Faster speeds on average means higher

temperature

• Rudolf Clausius: The Kind of Motion We Call Heat (1857)

• A consequence: There is a lowest temperature! (Davy)

Kinetic Theory

• A description of matter in terms of randomly moving particles (atoms)– Response to Aristotle (how

can atoms stay moving forever?) given by Newton

Kinetic Theory

• For a gas, for example– Pressure is due to the

particles colliding with the container walls

– Temperature is a measure of the average speed of the particles

Ludwig Boltzmann (1844-1906)• Professor in Vienna

– Also Graz, Munich, Heidelberg, Berlin, Leipzig

• Brings kinetic theory onto a firm foundation: “statistical mechanics”– Independently: J. W. Gibbs

• Ongoing battles with Ernst Mach and others over atomic and kinetic theory

The Conflict With Mach

• Mach’s view: “Positivism” (a particularly strong version!)

• Science should be based only on observable facts– The pressure exerted by a gas on the walls of its

container is an acceptable fact– “Explaining” that pressure in terms of invisible

particles is unacceptable, since the particles cannot be seen

The Conflict With Mach

• Heat is also a primary phenomenon– Explaining it in terms of the motion of unseen

particles is unacceptable

• For Mach, science is more description than understanding– Just study the relation between T and P, e.g. how

does P change as T is increased? Then make a catalog of results…

Boltzmann’s View

• Truth in science need not be seen directly, but is what can be consistently inferred from observations– Even though we cannot see atoms directly, the

atomic hypothesis makes predictions, e.g. about how P changes if T is increased

– If those predictions are confirmed by experiment, it provides support to the atomic hypothesis

Boltzmann’s View• If many predictions that follow from the

atomic hypothesis are confirmed, we may believe in the existence of atoms– In effect, we “see” atoms by their effects– Not really so different from “seeing” anything!

• This is the modern attitude

• Plus, today we can “see” atoms directly!

X-Ray Diffraction• X-rays have wavelengths

comparable to atomic sizes (~10–10 m)

• Can “see” atoms and molecules by bouncing X-rays off them

• Crystals and molecules reflect X-rays in patterns depending on their structures

X-ray diffraction pattern of DNA

Electron Microscope Images

•

Iron on Copper

Xenon on Nickel

Boltzmann and Philosophy

• After Mach retired, Boltzmann returned to Vienna and was given Mach’s philosophy course to teach

• These lectures became famous, in part for their attacks on various philosophies and philosophers

Boltzmann and Philosophy

• Proposed title of a talk for the VPS:Proof that Schopenhauer is a stupid, ignorant philophaster, scribbling nonsense and dispensing hollow verbiage that fundamentally and forever rots people’s brains

(These were actually Schopenhauer’s own words regarding Hegel!)

Boltzmann’s Death

• Moody, depressed, highly sensitive to criticism

• Suicide, (perhaps) due to despair at slow acceptance of his ideas

Brownian Motion

• Discovered in 1828 by Robert Brown, a botanist

• Observed that microscopic pollen grains suspended in a liquid move around erratically, even though the liquid itself has no observable motion

Explanation

• The grains are being jostled and buffeted by unseen atoms

• In 1905, Albert Einstein calculated the details of this process and made several predictions– E.g. how fast a collection of pollen grains should

spread out

• Quickly confirmed by experiments• Convinced remaining skeptics

Einstein’s “Miraculous Year”• In addition to the paper on

Brownian motion, AE published two other papers in 1905:– The special theory of

relativity (including E = mc2)– An explanation of the

“photoelectric effect”• Early quantum ideas• Won him the Nobel prize in

1921

Recap: Why Atoms?

• Chemical combination rules (Dalton)

• Success of atomic/kinetic theory in describing behavior of matter

• Brownian motion

• X-ray diffraction