Neat and Discrete Carbon Nanoparticles

Carbon Chemistry

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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A space elevator--a new transport into space?

Far Out Application?

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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The Proposal:

• Electric vehicles ascend the ribbon, lifting payloads from Earth to orbiting position

• A 62,000 mile long thin ribbon composed of an incredibly strong carbon nanotube composite

• Anchored to a ship

• The ribbon is connected to a massive counterweight on the other end that extends into space

Far Out Application?

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Why haven’t we already built a space elevator?

Answer: No materials were available that were both strong and light weight enough.

Carbon holds the key…

Far Out Application?

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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What elements on the periodic table are most likely to form discrete nanoparticles?

• Those that form covalent bonds, elements to the right of the transition metals (groups 13 through 16)

Why?• These elements form covalently bonded

molecules with specific geometry. • The central atom in these molecules form a

relatively small number of bonds to neighboring atoms.

Review: Carbon Chemistry

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Characteristics of discrete nanoparticles:

• covalent bonding

• non-extendable

• three-dimensional

• individual “gigantic” molecules

Review: Carbon Chemistry

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Let’s focus our attention mostly ondiscrete nanoparticles made from

Carbon

Review: Carbon Chemistry

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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How many bonds does carbon always form?

FourThese can be:

What is carbon’s electron orbital diagram?

• two single bonds and one double bond

• one single bond and one triple bond

• four single bonds

• two double bonds

Review: Carbon Chemistry

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Four single bonds

• Tetrahedral with bond angles of approximately 109º.

C Two single bonds and one double bond

• Planar with 120º bond angles.

C One single bond and one triple bond

• Linear with 180º bond angles.

C

=C= Two double bonds

• Linear with 180º bond angles.

Review: VSEPR Theory

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Allotropes are one of two or more forms of an element in the same physical state.

What are the common allotropes of carbon?

Graphite Diamond

What are Allotropes?

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How are the carbon atoms arranged in diamond?

Each interior carbon is covalently bonded to four others in a tetrahedron.

Diamond

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How are carbon atoms arranged in graphite?

• arranged in planar layers (sheets)

• each interior carbonatom is covalently bonded to three others in a hexagonal pattern

• very weak forces exist between the layers (gray lines in the figure above)

• the individual layers extend indefinitely in two dimensions

Graphite

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Knowing that:1. carbon always forms four bonds; 2. each carbon atom in graphite is covalently

bonded to three other carbon atoms; and3. the graphite layers are flat.

Two single bonds and one double bondC C

C

C

What is the bonding pattern around a given carbon atom in graphite?

Graphite

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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In the mid 1980s scientists experimented by vaporizing graphite using a laser. A new substance was formed.

This is a diagram of the first experiment with graphite.

Graphite

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Scientists knew the substance was carbon, but it wasn’t graphite, diamond, or individual carbon atoms.

They proposed the formula of the material was C16.

How would chemists represent the structure of C16?

So, what was it?

Nanoparticles

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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C16 fragment – a flat structure that does not contain hydrogen

What is wrong with this picture?

Hint: Remember, carbon always forms four bonds.

Nanoparticles

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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The product obtained in the lab was identified by mass spectrometry. The mass spectrum of the product is shown below.

The evidence points to the formula C60 (mass 720 amu).

How many carbon atoms did the sample contain?

C ??

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Could the structure of C60 be flat?

• No – just like the C16 fragment, a planar C60 structure would also have “dangling bonds” on the outer edges.

C 60

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How can you bend a sheet of C60 to connect the carbon atoms with dangling bonds?

Will it work to roll the sheet into a cylinder?

So what is the solution? Perhaps the answer can be found by looking at an organic compound.

C 60

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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Clearly by adding a 5-membered ring, the structure takes on a bowl-like shape with curvature. Aha!

Notice that this molecule, corannulene (C20H10), possesses a single 5-membered ring in addition to five 6-membered rings.

Nanoparticles

Neat and Discrete Carbon Nanoparticles: Carbon Chemistry© McREL 2009

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The mystery of C60 was finally solved.

The Nobel Prize in chemistry was awarded in 1996 for this work.

It soon became known as a “buckyball” because it resembles the famous architecture of Buckminster Fuller.

This material incorporates both 5-membered and 6-membered rings.

Buckyball

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1. What are the characteristics of discrete nanoparticles?

2. How does the arrangement of bonds affect the molecular geometry for carbon?

3. Describe the differences in how carbon is arranged in graphite vs. diamond?

4. How might carbon nanoparticles be useful?

Making Connections

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Lesson 1.2 What Makes Nanoscience so Different?

What makes Nanoscience so different?Compare Newtonian and Quantum Chemistry Regimes as they relate to nanoscale science

Lesson 1.3 What Makes Nanoscience so Important?

Interdisciplinary science The development of new technologies and instrumentation applications whose risk and benefits have yet to be determined

Lesson 3.1Carbon Chemistry

The molecular geometry is related to bond number and type of bond (single, double, and triple)The requirement of four bonds and their alternate resonance structures is most significant in the formation of carbon allotropesDifferent allotropes can have very different physical and chemical properties.

Lesson 1.1 What is Nanoscience?

What is Nanoscience? Examine and Compare size: macro, micro, sub-micro (nano)SI prefixes

Lesson 2.2 Extendable Solids: Reactivity, Catalysis, Adsorption

The difference between the energy at the surface atoms and energy of the interior atoms results in increased surface energy at the nanoscaleHigher surface energy allowing for increased reactivity, adsorption and catalysis at the nanoscale

Lesson 2.3Extendable Structures: Melting Point, Color Conductivity

In Extendable Structures:Melting point decreases because surface energy increasesColor changes because electron orbital changes with decreased particle sizeElectrical conductivity decreases because electron orbital changes with decreased particle size

Lesson 3.2Fullerenes and Nanotubes

Lesson 2.1 Extendable Solids

As the size of the sample decreases the ratio of surface particles to interior particles increases in ionic and metallic solids

Poster Assessment

Students will further investigate the essential question that they have considered throughout the module: How and why do the chemical and physical properties of nanosamples differ from those of macrosamples?

Module Flow Chart