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Graphite rod surface coated with C 60 Paul Dunk

Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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Page 1: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Graphite rod surface coated with C60

Paul Dunk

Page 2: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

OOO

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Carbon atoms the hot (10000o) focal point C60 evapourates unscathed from surrounding warm domain

Page 3: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

C60 on graphite rod – little fragmentationsmall Cn species are ingested by C60 forming larger fullerenes

m/z1,2001,000800600400200

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Desorbed C60

<2% fragmentation of C60

50% of the C60 converted to

higher fullerenes

200 400 600 800 1000

Page 4: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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MS of C60+n(neven) fullerenes

13C enrichedCarbon + C60

reaction

C62

C64

C66

C68

C70

C76

C74

C72

C78 C80

Page 5: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O
Page 6: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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C60 coated on a glass rod – just C60

C60

Typical desorbed C60

mass spectrum. No growth

Page 7: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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Expanded view of larger C60 + Cn fullerenes

The larger fullerenes become increasingly 13C enriched. In agreement with small Cn species inserting into C60 and higher fullerenes to form even higher fullerenes

C62

C64

C66

C68

C70

C76

C74

C72

C78 C80

Note C62 – C68 are not stable

Page 8: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Fullerenes grow by ingestion of small carbon species

Cn + C2 → Cn+2 etc

Page 9: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

The rod translated and rotated by stepper motor

laser pulse vaporisesrod

Helium pulse C60 reacts with C, C2 exits and undergo supersonic expansion

C60 coatedgraphite rod

Cluster Source

Page 10: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Helium

Pulsed Nozzle

Rod coated with 13C enriched amorphous carbon (ca 10%)

and pure C60

Pulsed Laser

Page 11: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Helium

Pulsed Nozzle

Pulsed Laser

Rotating/translating rod coated with 13C enriched amorphous carbon (ca 10%) and pure C60

Page 12: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

carbon plasma cluster beam

Laser and graphite disk

skimmer hole to mass spectrometer

Laser Vapourisation Cluster Beam System - Smalley

Page 13: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O
Page 14: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

The very sharp edged skimmer skims the expanding pulse into a very narrow beam

Supersonic Expansion into the vacuum chamber cools the clusters to very low

temperatures

Page 15: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Skimmer action more slowly

Page 16: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10,000K plasma of C atoms

Page 17: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10,000K plasma of C atoms

2. The atoms at the plasma/He interface cool to form small linear species: C2 C3, C4 etc

Page 18: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10,000K plasma of C atoms

2. The atoms at the plasma/He interface cool to form small linear species: C2 C3, C4 etc

3. Monocylic rings and at least two other families of carbon molecules form

Page 19: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10,000K plasma of C atoms

2. The atoms at the plasma/He interface cool to form small linear species: C2 C3, C4 etc

3. Monocylic rings and at least two other families of carbon molecules form

4. Small fullerene cages from C28… onwards are created

Page 20: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10,000K plasma of C atoms

2. The atoms at the plasma/He interface cool to form small linear species: C2 C3, C4 etc

3. Monocylic rings and at least two other families of carbon molecules form

4. Small fullerene cages from C28… onwards are created

5. Small fullerenes grow into larger cages by ingestion

Page 21: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10,000K plasma of C atoms

2. The atoms at the plasma/He interface cool to form small linear species: C2 C3, C4 etc

3. Monocylic rings and at least two other families of carbon molecules form

4. Small fullerene cages from C28… onwards are created

5. Small fullerenes grow into larger cages by ingestion

6. Final stage condensation to solid product – only Cn n=60, 70 and higher n species survive

Page 22: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

accumulation octopole

target rod skimmer

transfer octopole

ICR cell

stepper motor

pulsed valve

10-7 torr

diffusion pump

10-7

turbo pump

10-8

turbo pump

10-10

turbo pump

pulsed valve

source

Page 23: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

supersonic expansion

skimmed into beam

C60 reacts with carbon species

Page 24: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

The pulses pass across the chamber at about 10 Hz

…and the signal integrated perhaps 100 to a1000 or more times

The University of Sussex machine

Page 25: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

ions accumulated in octopole

3-10 laser shot accumulated

transferred to the ICR cell

Page 26: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

supersonic expansion

skimmed into beam

C60 reacts with carbon species

ions accumulated in octopole

3-10 laser shot accumulated

transferred to the ICR cell

Page 27: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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C60 + amorphous 13C coated on a quartz rod

Desorbed C60

C60 ingests 13C species

Page 28: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

C60 + Cn → C62 C64 C66 C68 C70 C72 etc

This study shows unequivocally that fullerenes can grow by ingestion of smaller carbon species

in this case

with Paul Dunk and Alan Marshall

Page 29: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

Page 30: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

Refinement of a closed cage growth mechanism proposed by Heath for the fullerenes and Endo and Kroto for nanotube growth

Page 31: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10000o plasma of C atoms

Page 32: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10000o plasma of C atoms

2. The atoms at the plasma/He interface cool to form C2 C3, C4 etc

Page 33: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10000o plasma of C atoms

2. The atoms at the plasma/He interface cool to form C2 C3, C4 etc

3. Monocylic rings (and another family) form

Page 34: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10000o plasma of C atoms

2. The atoms at the plasma/He interface cool to form C2 C3, C4 etc

3. Monocylic rings (and another family) form4. Small fullerene cages C28… are created

Page 35: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10000o plasma of C atoms

2. The atoms at the plasma/He interface cool to form C2 C3, C4 etc

3. Monocylic rings (and another family) form4. Small fullerene cages C28… are created

5. Small fullerenes grow into larger cages by ingestion

Page 36: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Multi stage formation mechanism

1. Laser fires and produces a ca10000o plasma of C atoms

2. The atoms at the plasma/He interface cool to form C2 C3, C4 etc

3. Monocylic rings (and another family) form4. Small fullerene cages C28… are created

5. Small fullerenes grow into larger cages by ingestion6. Final stage – only Cn n=60, 70 and higher n species

survive

Page 37: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O
Page 38: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Graphite rod surface coated with C60

Page 39: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O
Page 40: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

The pulses pass across the chamber at about 10 Hz

…and the signal integrated perhaps 100 to a1000 or more times

The University of Sussex machine

Page 41: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

The rod translated and rotated by stepper motor

laser pulse vaporisesrod

Valve emits a helium pulse

Fullerenes react with carbon vapor (C, C2) in the “clustering zone”. Then, the gas exits the channel and undergoes a supersonic expansion to create a cooled, molecular beam

fullerene-coatedgraphite target rod

Cluster Source

Page 42: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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Expanded view of desorbed C60 – normal isotope distribution

Normal ratio

← 13C12C59 ~ 60% of 12C60 signal

12C60 signal

Page 43: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

One strongly held conjecture was that C60 and C70 would be cul-de-sacs and our results indicate that this conjecture is incorrect.

Page 44: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

One strongly held conjecture was that C60 and C70 would be cul-de-sacs and our results indicate that this conjecture is incorrect.

Our results indicate that the primary nascent distribution of fullerenes shows almost no evidence of IPR stabilisation

which is a surprise to at least meRequiring a final stage which non IPR cages do

not survive

Page 45: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

One strongly held conjecture was that C60 and C70 would be cul-de-sacs and our results indicate that this conjecture is incorrect.

Our results indicate that the primary nascent distribution of fullerenes shows almost no evidence of IPR stabilisation

Page 46: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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C60 + amorphous 13C on a quartz rod

Desorbed C60

Page 47: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Q: How many pulses do you need to accumulate?A: A single laser shot is used vaporize the target during a single Helium pulse. Ten singe laser shot + He pulse are used to accumulate ions.

Q:How do you decide when to transfer them.A: After the final laser shot, a voltage at the “back” of the accumulation octopole switched, and the ions are transferred to the ICR cell. The switching of the voltage is controlled by the computer program interface.

Q: How many runs do you need in general for an average result?A: 3 time-domain aquisitions are averaged for when “growing” a preformed fullerene…….the signal is extremely strong.And 10 time-domain acquisitions are averaged when form endohedrals from a graphite-metal target. Thus, up to 10 time-domain acquisitions are averaged.

Answer to questions from email.

Page 48: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Fullerenes react with carbon vapor in the “clustering zone”, then the gas exits the channel and undergoes a supersonic expansion. As the clusters move from a region of high pressure through a small orifice into a high vacuum, they undergo a supersonic expansion. The random thermal energy of the clusters is converted into a directed motion (creating a cooled, molecular beam in which very few collisions occur) toward the skimmer and the ions subsequently enter the ion optics where they are accumulated and then transferred to the ICR cell for detection.

Page 49: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Q: How do you stop the pulse of ions in the accumulation trap A: The ions are confined radially by an oscilating radiofrequency within in octopole, and axially by voltages at the ends of the “accumulation octopole:.

Answer to questions from email.

Page 50: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O
Page 51: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

…undergo supersonic expansion and are skimmed into beam

10-7 torrdiffusion pump

10-7

turbo pump

10-8

turbo pump

10-10

turbo pump

Fullerenes react with

carbon species in the

vapourisation zone, then exit

reaction channel

the ions which enter the ion optics, where they are acuumulated in the central octopole segment

After 3-10 single laser shot accumulations, the ions are transferred to the ICR cell, which is located within in the bore of a 9.4 tesla superconducting magnet. Under the influence of the high magnetic field, the ions exhibit cyclotron motion. The ions induce a current on electrodes, which is detected as an “image current” in the time domain, and then the signal is converted to the frequency domain by an FT. Thus, the mass of the ion is detected as a frequency.

Page 52: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

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Expanded view of larger C60 + Cn fullerenes

Larger fullerenes increasingly 13C enriched

C62

C64

C66

C68

C70

C76

C74

C72

C78 C80

Page 53: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

2.7 eV

C28

2.4 eV

C284-

+ C2

facileC30 and higher

C28 C284-

Less reactive

C30 and higher

Electron donation stabilizes small fullerenes – prevents addition of small Cn

+ C2

Added electron density at the triple pentagon junction stabilizes – prevents C2 addition

Empty cage

endohedral

Page 54: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O
Page 55: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Fullerene Growth Mechanism

• “fullerene road” – Small fullerenes are the first to form, and then growth to larger fullerenes occur by uptake of small carbon species such as C2.

• There has been no evidence that fullerene growth can actually occur this way…until now!

• This growth model accounts for all experimental observations, for endohedrals and empty cages. This is potentially extremely significant if this checks out.

Page 56: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

C60

• C60 has been desorbed many times and analyzed many times by mass spec.

• No growth to larger fullerenes occur.

• However, most of these experiments are performed in a vacuum under conditions where fullerene growth will not be significant.

Page 57: Graphite rod surface coated with C 60 Paul Dunk O OO OO O O O O OO OO O O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O OO OO O O O

Bulk C60 coated on a graphite rod

• The rod was put in our cluster source

• Importantly, the experiment was performed exactly as I would if I were ablating a “clean” carbon rod to produce fullerenes.

• Pulse gas, laser timing, etc all known to be the conditions to see fullerenes

• The result: Addition of C2 to form larger fullerenes!

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Small carbon clusters added to C60 to form larger fullerenes. The coated C60 did not significantly fragment, but did significantly add carbon to form larger fullerenes.

C70

Desorbed C60

Very minor fragmentation of C60

Significant growth to larger fullerenes

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Larger clusters are FULLERENES. C70 (formed from desorged C60) was SWIFT isolated, and then subjected to collision with He while exciting (SORI).

These larger clusters are clearly fullerenes as C2 fragmentation occurs.

C70

C68C60

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C60 coated on a quartz rod

• To gain further insight, C60 was coated on a quartz rod

• The same experiment was performed to see if fullerene growth occurred.

• If no growth occurred, the small carbon species from the graphite were likely adding to C60 in the coated graphite rod experiment.

• The result: no growth!

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C60 + amorphous 13C on quartz rod

• C60 was mixed was some amorphous 13C. There was much more C60 than amorphous 13C, approximately 3:1.

• This mixture was applied to a quartz rod(from toluene)

• Growth to larger fullerene occurred, and they were more 13C enriched with size. This is consistent with small cluster addition to C60

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U@Cn+ directly formed from

U/graphite target enriched with amorphous 13C --for a total 13C content of 10%

U@C28 experimental

U@C28 simulated

U@C28 experimental

U@C28 (9.5% 13C) simulated

U@C28

U@C44

U@C36

U@C28

U@C36

U@C44

BOTTOM-UP GROWTH

U@Cn+ directly formed from

U/graphite target

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Growth mechanism and endoherals

• It is shown through our experiments that the classical endohedrals of Sc, La, and now Ti, Hf, Zr, U all strongly form endohedral fullerenes. But fullerenes smaller than C60 are most abundant, a clear deviation from the empty cages.

• Ionic model – electrons from the metal are transferred to the carbon cage in endohedral fullerenes giving, essentially, an indissociable salt...the cage is negatively charged, the encapsulating metal is positively charged. Our experiments coupled with the theoretical data show this principle applies to small fullerenes too.

• Electron transfer from the encapsulating metal to fullerene cage stabilizes the small fullerene from small carbon addition to larger fullerenes. This is why metals that can donate 3-4 electrons to the cage predominately form smaller fullerenes.

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Growth mechanism and M@C28

• Our experiments show that M@C28 forms first. And then larger clusters are seen under conditions that allow more growth.

• The metal nucleates initial growth.

• Experiments will need to be performed with coating a rod with an endohedral, I plan to ask Shinohara for a sample to use. This will prove that the “fullerene road” applies to endohedrals as well as the empty cages.

• Only a tetravalent metal can stabilize C28 sufficiently to yield a M4+@C284-

• Our calculations show that the donated electrons reside at the most reactive triple pentagon junction…the end result: C28 does not completely react to larger fullerenes.