October 2012 Teachers Guide For Graphene The Next Wonder

october 2012 teachers guide for graphene: the next wonder material? table of contents 1 about the guide 2 student que

October 2012 Teacher's Guide for
Graphene: The Next Wonder Material?
Table of Contents
1
About the Guide 2
Student Questions 3
Answers to Student Questions 3
Anticipation Guide 4
Background Information 7
Connections to Chemistry Concepts 14
Possible Student Misconceptions 15
Anticipating Student Questions 15
In-class Activities 16
Out-of-class Activities and Projects 17
References 17
Web sites for Additional Information 19
More Web sites on Teacher Information and Lesson Plans 20
About the Guide
===============
Teacher’s Guide editors William Bleam, Donald McKinney, Ronald
Tempest, and Erica K. Jacobsen created the Teacher’s Guide article
material. E-mail: [email protected]
Susan Cooper prepared the anticipation and reading guides.
Patrice Pages, ChemMatters editor, coordinated production and prepared
the Microsoft Word and PDF versions of the Teacher’s Guide. E-mail:
[email protected]
Articles from past issues of ChemMatters can be accessed from a CD
that is available from the American Chemical Society for $30. The CD
contains all ChemMatters issues from February 1983 to April 2008.
The ChemMatters CD includes an Index that covers all issues from
February 1983 to April 2008.
The ChemMatters CD can be purchased by calling 1-800-227-5558.
Purchase information can be found online at www.acs.org/chemmatters
Student Questions
=================
1.
What are three unique properties of graphene?
2.
How does the molecular structure of graphene differ from the
other allotropes of carbon—
diamond and graphite?
3.
What properties of graphene might make it useful in solar
panels?
4.
Why might graphene be a preferable choice for touch screens in
phones and computer screens?
5.
Why are researchers considering graphene for use in bionic
devices?
6.
Explain how single layers of carbon (graphene) might be
deposited on plastic sheets for use in graphene-based devices.
Answers to Student Questions
============================
1.
What are three unique properties of graphene?
Graphene conducts electricity better than any other common substance,
it is the thinnest known material (one atom thick) and is stronger
than steel.
2.
How does the molecular structure of graphene differ from the
other allotropes of carbon—diamond and graphite?
Graphene is a single layer of graphite which consists of carbon atoms
linked (bonded) to one another to form a network of hexagons. The
layers of graphite are only weakly bonded to each other. This is in
contrast to the bonding in diamond in which each carbon atom is bonded
to another carbon atoms, forming a very strong network.
3.
What properties of graphene might make it useful in solar
panels?
Graphene is nearly 100 % transparent to visible light as well as to UV
and IR. It also conducts electricity. Using silicon solar cells,
electricity is generated when the solar cells are exposed to light.
The graphene conducts the electricity away from the panel. Graphene
can be part of a light and flexible solar panel.
4.
Why might graphene be a preferable choice for touch screens in
phones and computer screens?
Touch screens must be conductive. It would also be good to have both
thin and flexible screens. Graphene provides all these properties.
Currently screens have a conductive layer of indium tin oxide which is
brittle and requires protective glass coatings. In turn the glass
makes for both a thick and inflexible display screen.
5.
Why are researchers considering graphene for use in bionic
devices?
Since bionic devices are used within the human body and are exposed to
a variety of ionic solutions, a device made from graphene, which is
non-reactive, could withstand chemical corrosion. It also conducts
electricity which means it could be used in the nervous system.
Graphene-based transistors could conduct nerve impulses around damaged
nerve tissue. Other types of transistors could be used to convert
electrical signals into motion (actuators). Also, a graphene implant
in the brain may be able to convert light signals from a digital
camera-like device in a damaged eye to an image.
6.
Explain how single layers of carbon (graphene) might be
deposited on plastic sheets for use in graphene-based devices.
One method is to pass methane gas over a copper sheet at high
temperatures with the expected result that the carbon from the methane
will deposit on the copper and the hydrogen will escape. The carbon
layer is transferred to a plastic sheet. A second method involves the
mixing of carbon (graphite) with a solvent, spraying the mixture onto
a plastic sheet, and allowing the solvent to evaporate, leaving the
carbon (graphene) behind.
Anticipation Guide
==================
Anticipation guides help engage students by activating prior knowledge
and stimulating student interest before reading. If class time
permits, discuss students’ responses to each statement before reading
each article. As they read, students should look for evidence
supporting or refuting their initial responses.
Directions: Before reading, in the first column, write “A” or “D,”
indicating your agreement or disagreement with each statement. As you
read, compare your opinions with information from the article. In the
space under each statement, cite information from the article that
supports or refutes your original ideas.
Me
Text
Statement
1.
Graphene is the thinnest material known to exist, yet it is
stronger than steel.
2.
Allotropes of the same element have the same chemical and physical
properties.
3.
The first samples of graphene were made using sticky tape.
4.
Silicon-based transistors conduct electricity better than
graphene-based transistors.
5.
In the future, graphene may be used in solar panels because it is
almost transparent to visible light.
6.
When you use a touch screen on a cell phone or tablet PC, you
transfer some electrical charge to the device.
7.
The word “bionic” comes from “biology” and “electronic.”
8.
Graphene must be in a perfect hexagonal pattern with no impurities
to be useful.
Reading Strategies
These matrices and organizers are provided to help students locate and
analyze information from the articles. Student understanding will be
enhanced when they explore and evaluate the information themselves,
with input from the teacher if students are struggling. Encourage
students to use their own words and avoid copying entire sentences
from the articles. The use of bullets helps them do this. If you use
these reading strategies to evaluate student performance, you may want
to develop a grading rubric such as the one below.
Score
Description
Evidence
4
Excellent
Complete; details provided; demonstrates deep understanding.
3
Good
Complete; few details provided; demonstrates some understanding.
2
Fair
Incomplete; few details provided; some misconceptions evident.
1
Poor
Very incomplete; no details provided; many misconceptions
evident.
0
Not acceptable
So incomplete that no judgment can be made about student
understanding
Teaching Strategies:
1.
Since several of the articles involve nanoparticles, you might
want to preview this issue with your students by reading and
discussing the “Chemistry of Carbon: Going Up!” short article in
“Did You Know?” on page 4 and the “Open for Discussion”
information on page 5.
2.
Links to Common Core State Standards: Ask students to develop an
argument explaining why they would or would not use new materials
made from nanoparticles. In their discussion, they should state
their position, providing evidence from the articles to support
their position. If there is time, you could extend the assignment
and encourage students to use other reliable sources to support
their position.
Directions: As you read the article, complete the chart below
describing the properties of graphene that may make the device
available in the future.
What properties of graphene are important for this application?
Advantages of using graphene
Flexible solar panels
Foldable cell phones
Bionic devices
Background Information
======================
(teacher information)
More on allotropic elemental carbon
Elemental carbon as it occurs in diamond, graphite, and now graphene,
exhibits different bonding characteristics. In diamond, one of the
hardest materials, the carbon atoms in the network are bonded in three
dimensions as single covalent bonds using sp3 bonding. This type of
bonding produces a very hard material. On the other hand, carbon as a
central atom in biological molecules does not produce the same effect
because these molecules are not pure carbon but contain other elements
such as hydrogen, oxygen and sulfur utilizing some of the bonding
positions of the carbon atoms. And the four bonding positions of a
carbon atom can also result in extremely large molecules.
Comparing the effect of bonding in diamond with another pure carbon
molecule, graphite, shows two different types of bonding. Layers of
graphite are formed from carbon atoms bonding to each other in a two
dimensional arrangement, with alternating single and double covalent
bonds. Individual layers of graphite can be thought of as a series of
benzene rings connected to each other. The graphite layers in turn are
bonded to each other through weak London force bonds which accounts
for the slippage of these layers (and their use as a lubricant).
Looking at the two dimensional structure of graphene, the bonding
within a layer is single covalent, sp2 bonding, leaving a single
electron unbonded which accounts for the conductivity properties of
graphene. Experimental results from transport measurements show that
graphene has a remarkably-high electron mobility at room temperature.
The mobility is independent of temperature between 10 K and 100 K. The
individual layers do not bond through London forces as in graphite.

(from http://physics.bu.edu/~neto/Topic0.htm)
Isolating individual layers of graphene for use in both conducting and
non-conducting applications was originally done in an unsophisticated
manner—using sticky cellophane tape to remove layers of pencil
graphite and reattaching them to a silicone plate. Currently, it
remains a technological challenge to develop effective and inexpensive
methods to produce usefully large sheets of graphene. Various
techniques have been developed but there is no one process at the
moment that has become the norm for “manufacturing” large sheets of
graphene. On another note, you can purchase a bottle full of graphene
particles but not of a useful size.
Some of the methods beyond cellophane tape for producing usefully
large sheets of graphene include the following.
High-quality sheets of few-layer graphene exceeding 1 cm2 (0.2 sq in)
in area have been synthesized via chemical vapor deposition on thin
nickel films with methane as a carbon source. These sheets have been
successfully transferred to various substrates, demonstrating
viability for numerous electronic applications.
An improvement of this technique uses copper foil (instead of the
nickel film), at very low pressure. With this method, the growth of
graphene automatically stops after a single graphene layer forms.
Arbitrarily large graphene films can be created. The aforementioned
single layer growth is also due to the low percentage of carbon in
methane (1C : 4H). Larger hydrocarbon gases such as ethane (2C : 6H)
and propane (3C : 8H) will lead to the growth of bi-layer graphene.
Growth of graphene has been demonstrated at temperatures compatible
with conventional complementary metal oxide semiconductor (CMOS)
processing, using a nickel-based alloy with gold as catalysts. This is
important because graphene may be used in conjunction with CMOS
semiconductors.
Another widely used process for the synthesis of graphene involves the
reduction of graphene oxide (GO). But the process normally employs the
exposure of the GO to hydrazine vapor, which is highly toxic and is
not practical on the commercial scale. Japanese researchers have found
that they can utilize certain bacteria easily obtained from river beds
to carry out the reduction of the graphene oxide flakes. The graphene
flakes act as the terminal electron acceptor for the bacteria when the
microbes “breathe” (the biochemical process of respiration which
involves an electron transport system). (http://www.sciencedaily.com/releases/2012/03/120321152554.htm)
More on integrating graphene into circuitry
One potential roadblock to the use of graphene in mass production is
the instability of graphene flakes. Researchers at Georgia Tech see a
solution to this problem by growing graphene sheets on silicon
carbide. According to the researchers, synthetic graphene sheets have
the potential to achieve a higher level of quality, making them an
alluring substitute for copper in circuitry. In fact, graphene could
outperform copper wire in connecting transistors and other integrated
circuits. Graphene can be manipulated on silicon carbide, using the
familiar steps of silicon processing. As for the advantage over
silicon itself, graphene far surpasses silicon as a conductor on the
nanoscale and is capable of much finer processing.
Another variation on this theme of combining graphene with silicon has
been developed at Penn State’s Electro-Optics Center (EOC) Materials
Division. The process, called silicon sublimation, thermally processes
silicon carbide wafers in a physical vapor transport furnace until the
silicon migrates away from the surface, leaving behind a layer of
carbon that forms into a one- to two-atom-thick film of graphene on
the wafer surface. Achieving 100 mm graphene wafers has put the
synthesis of ultra-large graphene and graphene-based devices into a
practical, usable category. In turn, another group at Penn State has
fabricated field effect transistors on the 100 mm graphene wafers. (http://www.sciencedaily.com/releases/2010/01/100131215530.htm)
Since graphene possesses electron mobility about 200 times greater
than that of silicon, it has been considered a potential substitute in
transistor circuitry. However, in graphene, compared with conventional
semiconducting materials, the current cannot be switched off because
graphene is semi-metallic. Both on and off flow of current is required
in a transistor to represent the “1” and “0” of digital signals.
Previous solutions and research have tried to convert graphene into a
semi-conductor. However, this radically decreased the mobility of
graphene, leading to skepticism over the feasibility of graphene
transistors. By re-engineering the basic operating principles of
digital switches, Samsung Advanced Institute of Technology has
developed a device that can switch off the current in graphene without
degrading its mobility. The demonstrated graphene-silicon Schottky
barrier can switch current on or off by controlling the height of the
barrier. The new device was named Barristor, after its
barrier-controllable feature. (http://en.akihabaranews.com/112562/science/samsung-electronics-presents-a-new-graphene-based-transistors)
Another approach is to create n- and p-type transistors using graphene
that has been modified through the addition of oxygen or nitrogen
(doping of the graphene to create electron holes). The resultant
device, a nanoribbon (strips of graphene that range in width from 10
nanometers to 150 nanometers), does not lose any of the mobility of
its graphene electrons. P-type transistors have been made because
oxygen atoms readily bond to the edges of the graphene, producing the
positively charged counterpart to electrons. The technique for
producing the n-type part of a transistor involves treating the
graphene in a heated environment of ammonia gas for a source of
nitrogen atoms that bond to the edges of the graphene and donate
electrons—the negative (n) part of the transistor. A diode is created
with these two types of transistor for directed flow of electrons in a
circuit. The graphene becomes the very speedy conductor of this
current.

Carbon ribbons: A graphene nanoribbon is shown in the center of this
image under an atomic force microscope. Adding nitrogen to the
nanoribbon creates an n-type transistor, an important building block
in graphene circuitry. (http://www.technologyreview.com/news/413425/a-step-toward-graphene-circuitry/?mod=related)
And ZdNet, a Web magazine about internet technology, reports that
Norwegian scientists have moved to “…commercialise [a] breakthrough
that uses a molecular beam device to create gallium arsenide nanowires
on a graphene substrate.”
(http://www.zdnet.com/researchers-find-way-to-grow-nanowires-on-graphene-7000004143/)
More on graphene for photonics
Graphene shows great promise as a candidate for photonics
applications—especially optical communications, where speed is an
issue. A new graphene-based material is covered with special metallic
nanostructures called plasmonic nanostructures. The metals used
include gold, silver and titanium (noble metals). A combination of
these noble metals with graphene significantly increases the amount of
light captured by the graphene. Graphene has an ideal "internal
quantum efficiency", the number of electrons released by a photocell
per photon of incident radiation of a given energy. The role of the
noble metals is to enhance the local electromagnetic fields by
coupling incoming light with electrons on the surface of the metal.
The nanostructures fabricated on top of the graphene concentrate these
electromagnetic fields in the region of the material where light is
converted to an electric current (photovoltage). Almost every photon
absorbed by graphene generates an electron-hole pair that could, in
principle, be converted into electric current. Graphene can also
absorb light of any color and has an extremely fast response to light.
The latter suggests that it could be used to create devices that are
much faster than any employed in optical telecommunications today.

a
b - d
a) An overall image of one of the plasmonic nanostructure devices (in
false colours). Blue, graphene; purple, SiO2 (300 nm); yellow, Ti/Au
electrodes. Scale bar, 20 μm. (b–d) Blow up of contacts with various
tested plasmonic nanostructures (again, in false colours).
http://physicsworld.com/cws/article/news/2011/sep/05/graphene-could-make-perfect-solar-cells
Another use of graphene in photovoltaic cells is to include it with
titanium dioxide in dye-sensitive solar cells (refer to student
projects for information on making a dye-sensitized solar cell). In a
dye-sensitized solar cell, the energy from photons absorbed by the dye
molecules causes some electrons to be ejected into the titanium
dioxide layer which conducts them to the anode of the cell. Adding
some graphene to the titanium dioxide increases conductivity of the
current by more than 50% compared with titanium dioxide alone. The
process for making these particular types of solar cells appears to be
both cost effective and easy to do.
More on flexible, printable solar cells
Plastic solar cells use copper, indium, gallium, and selenium in a
copper indium gallium selenide—(CIGS) mixture to absorb light from the
environment. Using nanotechnology, tiny crystals of this mixture are
sandwiched between metal contacts that “extract the charge” out of the
particle. These “sandwiches” are then added into a solvent creating a
composite that can be sprayed onto any object. (http://blog.txu.com/spray-on-solar-panels)
A video that shows the process of creating these spray-on solar cells
is found at
http://www.mnn.com/earth-matters/energy/videos/using-nanotechnology-to-create-spray-on-solar-panels.
New MIT-developed materials make it possible to produce photovoltaic
cells on paper or fabric, nearly as simply as printing a document. (A
complete article with videos showing the manufacturing/testing process
is found at
http://web.mit.edu/newsoffice/2011/printable-solar-cells-0711.html.)
The process departs from previous techniques that involved liquids and
high temperatures that potentially can damage the substrate onto which
the solar cells are deposited. Rather, a new printing process uses
vapor deposition and temperatures less than 120 oC. As a result,
ordinary paper and plastic can be used as the substrate onto which the
solar cells can be printed. Five layers of material are deposited,
using a paper mask to form patterns of cells on the surface. This is
done in a vacuum chamber. The process is essentially the same as used
to make the silvery lining of a bag of potato chips, so inexpensive on
a vast commercial scale. The resultant flexible device can actually be
folded without damaging its functionality.

These diagrams show how the researchers create an array of
interconnected PV cells. Using their masking technique, they first lay
down the anodes; next come the active layers, perpendicular to the
anode; and finally the silver cathodes—a little offset from the anodes
so as to connect each cell to the one next to it. Little L’s connect
the end of one row to the beginning of the next.
(source:
http://web.mit.edu/mitei/news/energy-futures/Energy_Futures_Autumn2011.pdf)

These photos show single PV cells deposited on newsprint (left) and on
copy paper
(right). The dark gray area is the anode; blue is the photoactive
layer; and silver is
the cathode coming from the other side. In the left sample, the text
of the newspaper
is still visible—undisturbed by the dry deposition of the PV
materials. The right
sample is folded, but it still functions.
One advantage of printing solar cells on something like paper or even
cloth is the reduction in costs for the inactive components of a solar
cell (glass, support structures, installation costs) which are usually
greater than the cost of the active films of the cells—sometimes twice
the cost. Just one interesting application of paper-based solar
cells—using them as window shades! It is calculated that paper costs
one-thousandth as much as glass for a given area. And if the paper
solar cells are used outdoors, they can be protected through standard
lamination materials. Further, it does not matter what kind of paper
is used. Even newsprint with the printing still on it works just fine
(as shown above)!
Also coming out of MIT research is the combining of conventional
silicon-based solar cells with pure carbon solar cells (using both
carbon nanotubes and buckyballs, C60). The reasons for incorporating
the carbon solar cells are because they are capable of absorbing in
the near infrared region (comprises 40% of the solar energy reaching
Earth) that part of the spectrum not absorbed by silicon-based solar
cells, and because the carbon layer would be transparent to visible
light, allowing it to be placed on top of the conventional silicon
cells. This tandem device could harness most of the energy of
sunlight. In addition, the carbon component increases the efficiency
of the solar cells because of its high conductivity characteristics.
(http://web.mit.edu/newsoffice/2012/infrared-photovoltaic-0621.html—included
as a reference for all-carbon solar cell using fullerenes and
buckyballs, absorbing at the near infra-red region)
More on graphene and capacitors for storing solar-generated
(photovoltaic) electricity
Existing battery technologies fail to address the marketplace needs
for high-power energy storage. With significant emphasis on renewable
energy, including a rapid ramp-up of solar, wind and geothermal
technologies and government mandated requirements for high efficiency
vehicles, there is a critical need for cost-effective, high-power and
high-capacity energy storage solutions. Graphene is one of the most
promising materials for ultracapacitor electrodes, with expectation of
power densities surpassing any other known form of activated carbon
electrodes due to its large and readily accessible surface area.
One interesting application of graphene that is being investigated is
its capacity to act as a capacitor for storing electrical energy that
can be part of a solar photovoltaic cell. It has very interesting
electrical properties that have allowed researchers to create a
graphene-based supercapacitor that exhibits a "specific energy density
of 85.6 Wh/kg at room temperature and 136 Wh/kg at 80 °C", which is
similar to nickel-metal hydride batteries, the chemistry used in most
current hybrid vehicles. The main difference is that supercapacitors
can be cycled an almost unlimited number of times (they don't lose
their ability to hold a charge, like batteries do), and they can be
charged and discharged extremely quickly (as long as you have a "fat
pipe", a cord that can handle a large current, to supply the power).
This would make them ideal for hybrids and electric cars if their
power-density were high enough (so far it isn't) and their cost came
down.
An application of the supercapacitor concept of graphene is a device
from India dubbed the “Amrita Smart”. The "integrated power storage
tile" weighs in at 200 g and, when exposed to the sun for 4 hours, can
go on to charge a laptop or phone in two hours, along with energy
storage of up to 7 days (30 days in one account). There is the
possibility of developing these into solar roof tiles, which can be
installed so that they blend in with regular tiles.
More on graphene and lithium ion battery combinations.
Graphene holds the promise of improving battery technology for hybrid
cars and electric vehicles (EVs). Adding graphene to lithium batteries
has recently been shown to prolong lithium battery life while
increasing usable charge.
As attractive as Li-ion batteries are for application in electric
vehicles and renewable energy applications, many potential electrode
materials are limited by slow Li-ion diffusion, poor electron
transport in electrodes, and increased resistance at the interface of
electrode/electrolyte at high charge. One avenue researchers are
exploring to improve that performance is to introduce hybrid
nanostructured electrodes that interconnect nanostructured electrode
materials with conductive additive material…TiO2 is an attractive
electrode material. It is abundant, low cost, and environmentally
benign. It is also structurally stable during the insertion and
extraction of lithium ions, and is intrinsically safe by avoiding
lithium electrochemical deposition. Graphene has excellent electronic
conductivity and mechanical properties, and may be the ideal
conductive additive for hybrid nanostructured electrodes, the
researchers suggested.
(http://www.greencarcongress.com/2009/09/adding-graphene-to-metal-oxides-significantly-improves-liion-electrode-specific-capacity-at-high-cha.html)
More on circuits in graphene-based transistors
There is great interest in using graphene to replace silicon in
electronic circuits. Already there are transistors that are made from
graphene. But the technique for creating the circuitry in these
graphene-based transistors requires that the graphene be first cut
into ribbons that are then incorporated into the device. But there is
a newer and more efficient (and accurate?) technique that is more akin
to establishing circuits by the old style of etching, done using acid
on reactive metal. But this time researchers start with a sheet of
graphene oxide (non-conductive) onto which they can write the circuits
or nanoribbons using the tip of a device known as an Atomic Force
Microscope (AFM). The tip is heated to between 150 and 1060 oC and
pulled across the graphene oxide sheet in whatever pattern is desired.
The heated tip causes the graphene oxide to lose oxygen atoms at
whatever spot it touches. This leaves behind pure graphene which is
10,000 times more conductive than the surrounding non-conductive
graphene oxide. So circuits can be established with good accuracy.
Connections to Chemistry Concepts
=================================
(for correlation to course curriculum)
1.
Allotrope—The fact that carbon can exist in three different
physical forms creates three very different sets of useful
physical and chemical properties. Compare the properties of
diamond with that of graphene and graphite, based on bonding, both
two- and three- dimensional aspects.
2.
Covalent Bonding—Depending on the spatial orientation of bonds in
carbon, you can end up with multidirectional bonding in diamond,
producing a lattice that is very strong due to each carbon atom
bonding to four other atoms ad infinitum. This is in contrast with
bonding of carbon in only one plane (graphene) which produces a
strong material in that plane but not between planes or layers.
3.
Conductivity—Conductivity of materials will depend on availability
of valence electrons that are mobile. The bonding in graphene
produces one unbonded electron per atom that contributes to the
conductivity of the carbon material.
4.
Photovoltaic—The use of certain elements such as silicon that can
lose electrons when particular wavelengths of electromagnetic
radiation (EMR) are absorbed can be coupled with a highly
efficient conductor such as graphene to move the electron stream
to some electrical device or storage mechanism.
5.
Metals—Metals are associated with conducting electrical currents
because of their loosely bonded valence electrons. Carbon is
neither a metal nor a non-metal but is able to conduct electricity
depending on the form of the carbon. Both graphite and graphene
conduct electricity. Graphite has a long history of use in
electrodes. Graphene is the new speedy non-metal conductor of
electricity.
6.
Electromagnetic radiation—In order for photovoltaics to work
efficiently, the solar absorbing materials must be able to respond
to the energy values of various parts of the electromagnetic
spectrum and eject electrons into an electron-capturing circuit.
7.
Semiconductor—A semiconductor is an important device in
electronics because it changes a non-conductor into a partial or
semiconductor. For pure silicon, which is a preferred chemical in
solar cells, absorption of electromagnetic radiation (EMR) does
not necessarily produce a flow of electrons. Rather, the pure
silicon has to be contaminated with elements having five valence
electrons such as phosphorus and antimony that become acceptors of
electrons lost by the silicon through absorption of certain
wavelengths of EMR. A conductor is an element that has no
separation (energy gap) between the conduction band and the
valence band of electrons. Non-conductors or insulators have
larger energy gaps and semiconductors are in between the two
extremes of energy gaps.
Possible Student Misconceptions
===============================
(to aid teacher in addressing misconceptions)
1.
“Only carbon can be used to form nanotubes.” It is found that
nanotubes made from boron and nitrogen, with or without carbon,
have electrical properties equal to or better than pure carbon
nanotubes.
Anticipating Student Questions
==============================
(answers to questions students might ask in class)
1.
“What is the nanoscale?” The nanoscale is the dimensional range of
approximately 1 to 100 nanometers.
2.
“What are nanomaterials? Do they exist in nature?” Nanomaterials
are substances that contain nanoscale structures internally or on
their surfaces. These can include engineered nano-objects such as
nanoparticles, nanotubes, and nanoplates. Naturally occurring
nanoparticles can be found in volcanic ash, sea spray, and smoke.
3.
“What is the difference between graphene and fullerene?” Graphene
is a two dimensional sheet of carbon atoms linked together by
single covalent bonds to form a network. Fullerenes are also made
of carbon atoms but in the form of tubes or spheres. The term
fullerene comes from the name of Buckminster Fuller, a famous
architect who designed the geodesic dome that has the shape of the
spherical fullerene, also called a buckyball, which is formed from
60 carbon atoms.
4.
“In what chemicals is graphene soluble?” Graphene and fullerenes
are sparingly solubility in aromatic solvents such as toluene and
benzene. They are also soluble in carbon tetrachloride, carbon
disulfide, and 1,2-dichlorobenzene.
In-class Activities
===================
(lesson ideas, including labs & demonstrations)
1.
Using molecular models, students could construct diamond,
graphite, and graphene (using the individual layers used to show
graphite). There are also instructions for producing buckyballs
from paper. (http://www.nisenet.org/sites/default/files/catalog/uploads/2008/11/3066/strucbucky_diecut_1of8_dec09.pdf)
2.
A collection of activities on the nanoscale can be found at
http://mrsec.wisc.edu/Edetc/nanoquest/carbon/index.html. Included
in the activity list are applications of nanoarchitecture, liquid
crystal sensors, nanofabric testing, size of nanotubes, and
nanomedicine. Printable classroom materials are included.
3.
Another source of printable classroom activities at the nanoscale
is found at http://nanosense.org/activities/sizematters/index.html.
At the same Web site is a collection of Power Points for use in
the classroom.
4.
Students could perform a lab exercise in which they determine the
size of a single molecule, through a series of measurements and
calculations for a layer of oleic acid that is considered to be
one molecule thick. The lab exercise can be found at
http://kaffee.50webs.com/Science/labs/Chem/Lab-Size.of.Molecule.html.
5.
Students might want to mimic the process of the sticky tape
removal of a single layer of carbon by applying a similar forensic
technique for lifting fingerprints. The procedure can be found at
http://www.ehow.com/how_6523624_lift-fingerprints-home.html.
6.
A related activity for detecting fingerprints uses a technique
based on depositing superglue onto the fingerprint, then
chemically highlighting the print. An instruction video can be
found at
http://special-effects.wonderhowto.com/how-to/lift-fingerprints-using-superglue-211990/.
7.
If students have not gone through the exercise of determining
conducting and non-conducting elements, they will be surprised to
find that carbon lacks the characteristics of conductors (shiny,
metallic-looking, flexible), yet it conducts. Students can build
their own conductivity meter; pencil “lead” (carbon) can be used
for the electrodes. (For instructions see
http://www.chymist.com/conductivity.pdf or
http://www.essortment.com/test-solids-liquids-conduct-electrical-current-best-39620.html
or http://chemmovies.unl.edu/chemistry/smallscale/SS035.html or
refer to diagram below (from the last listed source):

Out-of-class Activities and Projects
====================================
(student research, class projects)
1.
Students who have an interest in photovoltaics can use the
following Web site for understanding the basics of solar cells and
the principles of electrical circuits:
http://photonicswiki.org/index.php?title=Photovoltaics-_Outreach_Kit#Three_types_of_solar_cells.
2.
Students who want to build their own nanocrystalline solar cells
that use various dyes can obtain information at
http://photonicswiki.org/index.php?title=Nanocrystalline_-_Dye_Solar_Cell_Lab.
The site includes diagrams that show the workings of the device.
Another very good visual that shows how the cell works is found at
http://www.community.nsee.us/concepts_apps/dssc/DSSC.html.
Kits for dye-sensitive nanocrystalline solar cells can be purchased
from ICE (Institute for Chemical Education) at
http://ice.chem.wisc.edu/Catalog/SciKits.html#Anchor-Nanocrystalline-41703
as well as http://www.solideas.com/solrcell/english.html.
3.
Students can do their own single layer carbon extraction by
following the illustrated instructions at
http://www.scientificamerican.com/slideshow.cfm?id=diy-graphene-how-to-make-carbon-layers-with-sticky-tape#1.
References
==========
(non-Web-based information sources)

Rosenthal, A. New Technology—The World of the Super Small, ChemMatters
2002, 20 (4), pp 9–13. This article looks at nanotechnology that uses
empty viral capsules (capsids) to manufacture specific molecules
within another cell such as a yeast or bacterial cell (E. coli)
through genetic coding (RNA). They can also be used to create specific
non-biological molecules such as those that can be used in nano-scale
transistors (specific structure that can produce the “on” and “off”
switches of transistors).
Rosenthal, A. Nanomotors, ChemMatters 2006, 24 (2), pp 18–19. This
article describes the operation of naturally occurring nanomotors
(think of single cell organisms propelled by a flagella) and the
design and construction of non-biological (synthetic) nanomotors that
can be used to deliver specific chemicals for medical treatment within
the human body.
____________________
An article that discusses all aspects of graphene is found in
Scientific American: Geim,A.K; Kim, P. Carbon Wonderland, Scientific
American, April 2008, 299, pp 90–97. Included in the article is a
description of how to produce single layers of graphene (DIY), using
the original technique of cellophane tape extraction.
An interesting and detailed article that deals with nanosize machines
and the important requirement that they have a source of power is
found in Scientific American: Wang,Z.L. Self-Powered Nanotech,
Scientific American, January 2008, 298 (1), pp. 82–87. The interesting
aspect of this article is the information as to how useful energy for
locomotion can be generated through vibrations (including the human
pulse), along with temperature differences that can be transformed
into useable electricity through piezoelectric nanowires. Applications
of these tiny devices could include their use as monitoring devices
within the body as well as a battery that never needs to be replaced
(such as its use in powering a pacemaker).
A complementary article that elaborates on the powering of nanorobots
is found in: Mallouk, T.E. and Ayusman, S. Powering Nanorobots,
Scientific American, May 2009, 300 (5), pp. 72–77.
Web sites for Additional Information
====================================
(Web-based information sources)
More sites on using graphene for desalination of water
The use of graphene membranes for desalination of water is described,
with video and diagrams of molecules at the graphene interface, at
http://www.nanowerk.com/news/newsid=25780.php. The key in the design
of these graphene-based membranes is to get the pores the correct
size—not too large to let salt through and not too small to
essentially block the transmission of the water. The membrane does not
depend on reverse osmosis which requires an energy-dependent
mechanical design.
More sites on the sticky tape extraction of graphene
If you want to see how to do the sticky tape extraction of graphene,
refer to the following Web sites:
http://www.scientificamerican.com/slideshow.cfm?id=diy-graphene-how-to-make-carbon-layers-with-sticky-tape#1
and
http://physicsworld.com/cws/article/multimedia/2011/sep/29/how-to-make-graphene.
More sites on carbon basics and graphene in particular
A video about carbon and the co-discoverers of graphene extraction
with sticky tape is found at
http://www.scientificamerican.com/article.cfm?id=graphene-material-marvel-video.
More sites on designing nano-scale robots for medical use
An article and a video that describe the design and application of
nano-scale robots for delivering cancer-fighting chemicals can be
found at http://harvardmagazine.com/2012/09/cancer-fighting-robots.
These robots (images included in article) are constructed from protein
and DNA molecules.
More sites on techniques for weighing a single molecule or
nanoparticle
Massing of a single molecule or nanoparticle is done through the use
of nanoelectromechanical systems resonators. A description of this
technique is found at
http://www.scientificamerican.com/article.cfm?id=nems-resonator-nanoparticle-mass&WT.mc_id=SA_DD_20120830&WT.mc_id=SA_emailfriend.
More sites on the nano scale
A government site, the National Technology Initiative, devoted to all
things “nano-“, is found at
http://www.nano.gov/nanotech-101/nanotechnology-facts.
More sites on graphene models
An extensive collection of images of models of graphene molecules can
be found at
http://www.google.com/search?q=graphene&hl=en&client=firefox-a&hs=M2g&rls=org.mozilla:en-US:official&prmd=imvnsl&tbm=isch&tbo=u&source=univ&sa=X&ei=PpXxT7obwpTpAfadpdgG&ved=0CHQQsAQ&biw=1333&bih=702.
Another site with several drawings and a micrograph of graphene (along
with text about graphene) is found at
http://hplusmagazine.com/2010/05/03/graphene-next/.
More sites on buckyballs and fullerenes
A comprehensive Web site about the history of discovering buckyballs
and fullerenes is found at
http://physicsworld.com/cws/article/print/1998/jan/01/carbon-nanotubes.
Included in the article are descriptions of structure, making
nanotubes, electronic properties, measurement of predicted properties
of the carbon molecules, and the behavior of nanotubes in light.
More Web sites on Teacher Information and Lesson Plans
======================================================
(sites geared specifically to teachers)
A complete set of lessons (includes printable activities and Power
Point presentations) on nano can be found at
http://nanosense.org/activities.html. Topics covered include an
introduction to the basics about size, interaction of light with
matter (sunscreen at the nano scale), converting light to electricity
(photovoltaics) and filtering to produce clean water using
nanomaterials.
Another source of classroom activities about carbon with useful
references can be found at
http://mrsec.wisc.edu/Edetc/EExpo/carbon/FormsofCarbon_programguide.pdf.
20