Applications of Graphitic Carbon Materials

1. Applications of Graphitic Carbon Materials Dr. Lain-Jong Li (Lance Li) Associate Research Fellow Research Center for Applied Science Academia Sinica, Taiwan

2. Single-Walled Carbon Nanotubes for Macroelectronics

3. 1. Transistors based on carbon nanotube networks Solution processable Printable ( Adv. Mater. 2010) (Chem. Comm. 2009)

4. 2. Carbon Nanotube Networks as DNA sensors 1. Devices are fabricated by microelectronic fabrication. 2. DNA addition directly affects the transfer characteristics 3. Detection limit: ~ 10 nM DNA Bare Immobilized Hybridized Intercalated Appl. Phys. Lett. 89, 232104 (2006)

5. 2.1 Study of Sensing Mechanism Changing the contact metals

6. Covering the contacts SWNT channels slightly response to DNA molecules But electrode-SWNT Contacts seem to play more important roles ( J. Am. Chem. Soc. 129, 14427, 2007)

7. 2.2 Introducing more charges More charges can be introduced to the DNA with reporter DNA

8. Sensitivity enhancement The DNA detection limit is dramatically improved from 1 nM to 100 fM by using reporter DNA-AuNP conjugates ( Adv. Mater. 20, 2389, 2008)

9. Graphene-related

10. 1. Large Size Graphene Oxides Ultra-large single layer graphene oxides ( up to mm size) ( absorption ~ 2%) Chem. of Mater. 21, 5674 (2009)

11. 2. Graphene Oxide Reduction by Alcohol * 1st stage: I(D) increases with richness of 6-fold aromatic rings * 2nd stage: I(D) is inversely proportional to the graphene domain size (T-K relations)

12. Graphene Oxide Reduction by Alcohol * Graphene domain size is dominating conduction properties (submitted)

13. Pressure: 0.1~1 Torr and 750 Torr on Cu and Ni substrates respectively. 900 ºC 1 2 3 4 RT 30 min 30 min 10~20 min 3. CVD Graphene Step 1: H2 Step 2: H2 Step 3: CH4/H2 Step 4: Ar Substrate: Ni foil, 30 μm in thickness

14. FLG FLG New Substrate New Substrate Transfer to the desired substrates Immerse FLG/Cu foil in ~ 1.5 wt% FeCl3 solution (a) Rub one side FLG by sandpaper FLG FLG FLG Cu foil Cu foil Cu foil FLG FeCl3 solution Wait for several hours Heat at 80 0C for 5-10 minutes Dilute FeCl3 solution and transfer to new substrate, such as PET, SiO2 FLG (b) FeCl3 solution FLG

15. Effective doping in graphene monolayer 4.1 Doping of Graphene from Substrates Charge exchange may occur between graphene and SiO2 SiO2

16. Doping of Monolayered graphene dependson the surface potential of SiO2 substrates Phys. Rev. B 79, 115402 (2009)

17. 4.2 Doping of Graphene by Aromatic Molecular Adsorption Small 5, 1422 (2009)

18. 4.3 Stable Doping of CVD Graphene by AuCl3 Work Function is Tunable

19. Work function

20. Work function is tunable ACS Nano (2010 in press)

21. 5. Aromatic molecules on Graphene Tetrasodium 1,3,6,8-pyrenetetrasulfonic acid (TPA) Strong electron-withdrawing groups attached to pyrene

22. Phonon Symmetry Breaking- DFT calculation a full geometry optimization is performed including the optimization of the lattice constants using the DMol3 package (with all electrons considered) and the GGA (PBE) and DNP basis sets. Once the optimized structure is obtained, the force constants are calculated directly by altering atomic positions in both pristine and decorated graphene. ( ~4% different from those in pristine graphene) *Various aromatic molecules result in different energies of G-band splitting. Phys. Rev. Lett. 102, 135501 (2009)

23. Ongoing study • Gap Opening: Stripping ? • AB-stacked bilayer graphene ? • How to grow bilayer graphene with desired stacking • 2. Effect of defects on transport? • Effect of graphene edge (or edge defect)?