Supplementary Information for Graphene Quantum Dots Derived from Carbon Fibers

Transcription

1 Supplementary Information for Graphene Quantum Dots Derived from Carbon Fibers Juan Peng 1,2, Wei Gao 3, Bipin Kumar Gupta 1,4, Zheng Liu 1, Rebeca Romero-Aburto 1,5, Liehui Ge 1, Li Song 6, Lawrence B. Alemany 3, Xiaobo Zhan 1, Guanhui Gao 1,7, Sajna Antony Vithayathil 8, Benny Abraham Kaipparettu 8, Angel A. Marti 3,9, Takuya Hayashi 10, Jun-Jie Zhu 2,* and Pulickel M. Ajayan 1,3* 1 Mechanical Engineering and Materials Science Department, Rice University, Houston, Texas 77005, USA 2 State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing , P. R. China 3 Department of Chemistry, Rice University, Houston, Texas 77005, USA 4 National Physical Laboratory (CSIR), Dr K S Krishnan Road, New Delhi , India 5 Department of Molecular Pathology, The University of Texas MD. Anderson Cancer Center, Houston TX 77054, USA 6 Research Center for Exotic Nanocarbons, Shinshu University, Wakasato, Nagano , Japan 7 Institute of Materials Science and Engineering, Ocean University of China, Qingdao, , P.R. China 8 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA 9 Department of Chemistry and Bioengineering, Rice University, Houston, Texas 77005, USA 10 Faculty of Engineering, Shinshu University, Wakasato, Nagano , Japan 1

2 Methods Synthesis of graphene quantum dots: Pitch carbon fibers (0.30 g, directly purchased from Fibre Glast Development Corporation) were added into a mixture of concentrated H 2 SO 4 (60 ml) and HNO 3 (20 ml). The solution was sonicated for two hours and stirred for 24 hours at different temperatures of 80 0 C, C, and C, respectively. The mixture was cooled and diluted with deionized (DI) water (800 ml). The ph was adjusted to 8 with Na 2 CO 3. The final product solution was further dialyzed in a dialysis bag (retained molecular weight: 2000 Da) for 3 days. Characterization of graphene quantum dots: The TEM image and the selected area electron diffraction pattern were obtained on a JEOL 2100 Field Emission Gun TEM. The AFM image was obtained on a Digital Instrument Nanoscope IIIA AFM. XPS analyses were carried out on a PHI Quantera x-ray photoelectron spectrometer with a chamber pressure of torr and an Al cathode as the X-ray source. The source power was set at 100 W, and pass energies of ev for survey scans and ev for high-resolution scans were used. Raman spectra were recorded with a Renishaw InVia Raman microscope using a 50 objective lens at room temperature, with a nm laser beam and 1,800 lines per mm grating. XRD data were collected on a Rigaku D/Max Ultima II Powder X-ray diffractometer. FTIR spectra were obtained on a Nicolet FTIR Microscope with an MCT/A detector, and for FTIR measurements, an MCT/B detector was used. Photoluminescence characterization was done using a luminescence spectrometer (Nanolog, HORIBA, Jobin Yvon) with xenon lamp as the source of excitation. Time resolved photoluminescence (TRPL) was recorded using a time-correlated single photon counting technique with an Edinburgh-spectrometer, Model No. FLSP-920 using picosecond laser diodes as the source of excitation. Cytotoxicity evaluation: The cells were cultured and maintained in DMEM high glucose medium (Invitrogen) containing 4.5g/mL D-glucose, 4 mm L-glutamine, and 110 mg/ml sodium pyruvate, with 2

3 10% fetal bovine serum (FBS), 100 IU ml -1 penicillin and 100 µg/ml streptomycin. MDA-MB231 and T47D cells were plated at cells per well on 96 well plates, and were left to adhere overnight. Different concentrations of GQDs (0-50 µg/ml) in culture media were added to each well in triplicate. The cells were then incubated for hours. At the end of the study, cells were washed gently with 200 µl warm, sterile PBS. Then 200 µl per well of [3-(4,5-dimethyl-2-thiazolyl)-2, 5-diphenytetrazolium bromide(4 mg/ml)] was added per well and incubated for 4h. After removing the MTT reagent, 200 µl of dimethyl sulfoxide (DMSO) was added per well and incubated for additional 5 min at RT (M.B. Hansen. S.E. Nielsen, 1989). Optical density of solubilized formazan salts was assessed at 570 nm in a Tecan Infinite M200 microplate reader (Mannedorf, Switzerland). Cell imaging: For imaging, 1x10 4 cells were plated in each well of a 4 well sterile chamber slides (Nunc, USA) 500 µl culture medium. After overnight culture, 50 µg/ml GQDs was added in culture medium and incubated in regular cell culture conditions. After 24 hours of culture, medium with GQDs was removed from the cells and washed two times with 1ml 1X PBS. Cells were fixed using 1% paraformaldehyde and mounted with Vectashield antifade mounting media with DAPI (Vector Laboratories, Inc., CA). Cellular imaging was done using a Nikon Eclipse 90i microscope equipped with the Cool SNaP HQ2 CCD camera (Photometrics, AZ). Nikon Intensilight C-HGFI lamp was used as the fluorescence light source. 3

4 Figure S1. SEM images of (a) carbon fibers; (b) cross section part of carbon fiber; (c) and (d) fractured carbon fiber. Figure S2. The phtograph of the GQDs dispersion in (a) DMF and (b) DMSO. 4

5 Figure S3. Tuning in color coordinates of GQDs with different reaction temperature. Figure S4. (a) Size distribution of green GQDs; (b) Size distribution of yellow GQDs; (c) HRTEM image of typical green GQDs; (d) HRTEM image of typical green GQDs. 5

6 Figure S5. PLE spectrum of the blue GQDs with emission at 434 nm and PL spectrum of the blue GQD excited at 318 nm registered at room temperature. Figure S6. Typical electronic transitions of triple carbenes at zigzag sites observed in the optical spectra for blue emission color GQDs. 6

7 Figure S7. PLE spectrum of the green GQDs with emission at 500 nm. Figure S8. PLE spectrum of the yellow GQDs with emission at 564 nm. 7

8 Figure S9. PL spectra of the blue GQDs at different excitation wavelengths. Figure S10. PL spectra at 318 nm excitation of blue GQDs at different ph. 8

9 Figure S11. TRPL decay profile of green GQDs recorded at room temperature while monitoring the emission at emission at 434 nm upon 371 nm excitation wavelength. The inset shows the lifetime data and the parameter generated by the exponential fitting. 9

10 Figure S12. Cell viability assay with human breast cancer cell lines MDA-MB-231 and T47D cell treated with different concentration of green and blue GQDs. 10

11 Figure S13. Cell viability assay with 1µM of doxorubicin was used as a positive control experiment, toxicity at 24 and 48 hrs is 50 % and 35%, respectively. 11