Neat and Discrete Carbon Nanoparticles Carbon Chemistry Far

Neat and Discrete Carbon Nanoparticles Carbon Chemistry

Far Out Application? A space elevator-a new transport into space? Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 2

Far Out Application? The Proposal: • 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 • Electric vehicles ascend the ribbon, lifting payloads from Earth to orbiting position Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 3

Far Out Application? 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… Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 4

Review: Carbon Chemistry 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. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 5

Review: Carbon Chemistry Characteristics of discrete nanoparticles: • covalent bonding • three-dimensional • individual “gigantic” molecules • non-extendable Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 6

Review: Carbon Chemistry Let’s focus our attention mostly on discrete nanoparticles made from Carbon Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 7

Review: Carbon Chemistry What is carbon’s electron orbital diagram? How many bonds does carbon always form? Four These can be: • four single bonds • two single bonds and one double bond • two double bonds • one single bond and one triple bond Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 8

Review: VSEPR Theory Four single bonds • Tetrahedral with bond angles of approximately 109º. C Two single bonds and one double bond • Planar with 120º bond angles. =C= Two double bonds • Linear with 180º bond angles. C One single bond and one triple bond • Linear with 180º bond angles. C Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 9

What are Allotropes? Allotropes are one of two or more forms of an element in the same physical state. What are the common allotropes of carbon? Graphite Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 Diamond 10

Diamond How are the carbon atoms arranged in diamond? Each interior carbon is covalently bonded to four others in a tetrahedron. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 11

Graphite How are carbon atoms arranged in graphite? • arranged in planar layers (sheets) • each interior carbon atom 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 Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 12

Graphite Knowing that: 1. carbon always forms four bonds; 2. each carbon atom in graphite is covalently bonded to three other carbon atoms; and 3. the graphite layers are flat. What is the bonding pattern around a given carbon atom in graphite? C Two single bonds C C and one double bond C Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 13

Graphite In the mid 1980 s scientists experimented by vaporizing graphite using a laser. A new substance was formed. This is a diagram of the first experiment with graphite. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 14

Nanoparticles Scientists knew the substance was carbon, but it wasn’t graphite, diamond, or individual carbon atoms. So, what was it? They proposed the formula of the material was C 16. How would chemists represent the structure of C 16? Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 15

Nanoparticles C 16 fragment – a flat structure that does not contain hydrogen What is wrong with this picture? Hint: Remember, carbon always forms four bonds. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 16

C ? ? The product obtained in the lab was identified by mass spectrometry. The mass spectrum of the product is shown below. How many carbon atoms did the sample contain? The evidence points to the formula C 60 (mass 720 amu). Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 17

C 60 Could the structure of C 60 be flat? • No – just like the C 16 fragment, a planar C 60 structure would also have “dangling bonds” on the outer edges. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 18

C 60 How can you bend a sheet of C 60 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. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 19

Nanoparticles Notice that this molecule, corannulene (C 20 H 10), possesses a single 5 -membered ring in addition to five 6 membered rings. Clearly by adding a 5 -membered ring, the structure takes on a bowl-like shape with curvature. Aha! Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 20

Buckyball The mystery of C 60 was finally solved. This material incorporates both 5 -membered and 6 membered rings. It soon became known as a “buckyball” because it resembles the famous architecture of Buckminster Fuller. The Nobel Prize in chemistry was awarded in 1996 for this work. Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 21

Making Connections 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? Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 22

Module Flow Chart Lesson 1. 1 What is Nanoscience? Examine and Compare size: macro, micro, submicro (nano) SI prefixes Lesson 1. 2 What Makes Nanoscience so Different? Lesson 1. 3 What Makes Nanoscience so Important? What makes Nanoscience so different? Compare Newtonian and Quantum Chemistry Regimes as they relate to nanoscale science Interdisciplinary science The development of new technologies and instrumentation applications whose risk and benefits have yet to be determined Lesson 2. 2 Extendable Solids: Reactivity, Catalysis, Adsorption Lesson 2. 3 Extendable Structures: Melting Point, Color Conductivity The difference between the energy at the surface atoms and energy of the interior atoms results in increased surface energy at the nanoscale Higher surface energy allowing for increased reactivity, adsorption and catalysis at the nanoscale In Extendable Structures: Melting point decreases because surface energy increases Color changes because electron orbital changes with decreased particle size Electrical conductivity decreases because electron orbital changes with decreased particle size Neat and Discrete Carbon Nanoparticles: Carbon Chemistry © Mc. REL 2009 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? Lesson 3. 1 Carbon Chemistry 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 Lesson 3. 2 Fullerenes and Nanotubes 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 allotropes Different allotropes can have very different physical and chemical properties. 23