Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts
Abstract
Owing to its high conductivity, graphene holds promise as an electrode for energy devices such as batteries and photovoltaics. However, to this end, the work function and doping levels in graphene need to be precisely tuned. One promising route for modifying graphene’s electronic properties is via controlled covalent electrochemical grafting of molecules. We show that by employing diaryliodonium salts instead of the commonly used diazonium salts, spontaneous functionalization is avoided. This then allows for precise tuning of the grafting density. Moreover, by employing bis(4-nitrophenyl)iodonium(III) tetrafluoroborate (DNP) salt calibration curves, the surface functionalization density (coverage) of glassy carbon was controlled using cyclic voltammetry in varying salt concentrations. These electro-grafting conditions and calibration curves translated directly over to modifying single layer epitaxial graphene substrates (grown on insulating 6H-SiC (0 0 0 1)). In addition to quantifying the functionalization densities using electrochemical methods, samples with low grafting densities were characterized by low-temperature scanning tunneling microscopy (LT-STM). We show that the use of buffer-layer free graphene substrates is required for clear observation of the nitrophenyl modifications. Furthermore, atomically-resolved STM images of single site modifications were obtained, showing no preferential grafting at defect sites or SiC step edges as supposed previously in the literature. Mostmore »
- Authors:
-
- Univ. of Texas, Austin, TX (United States)
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Publication Date:
- Research Org.:
- Energy Frontier Research Centers (EFRC) (United States). Understanding Charge Separation and Transfer at Interfaces in Energy Materials (CST); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA)
- OSTI Identifier:
- 1140350
- Alternate Identifier(s):
- OSTI ID: 1252823
- Report Number(s):
- SAND2014-0150J
Journal ID: ISSN 1572-6657; PII: S1572665715002301; TRN: US1600351
- Grant/Contract Number:
- AC04-94AL85000
- Resource Type:
- Journal Article: Accepted Manuscript
- Journal Name:
- Journal of Electroanalytical Chemistry
- Additional Journal Information:
- Journal Volume: 753; Journal Issue: C; Journal ID: ISSN 1572-6657
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 74 ATOMIC AND MOLECULAR PHYSICS; epitaxial graphene; electrochemical modification; functionalization; iodonium salts; STM
Citation Formats
Gearba, Raluca I., Mueller, Kory M., Veneman, Peter A., Holliday, Bradley J., Chan, Calvin K., and Stevenson, Keith J. Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts. United States: N. p., 2015.
Web. doi:10.1016/j.jelechem.2015.05.009.
Gearba, Raluca I., Mueller, Kory M., Veneman, Peter A., Holliday, Bradley J., Chan, Calvin K., & Stevenson, Keith J. Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts. United States. https://doi.org/10.1016/j.jelechem.2015.05.009
Gearba, Raluca I., Mueller, Kory M., Veneman, Peter A., Holliday, Bradley J., Chan, Calvin K., and Stevenson, Keith J. Sat .
"Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts". United States. https://doi.org/10.1016/j.jelechem.2015.05.009. https://www.osti.gov/servlets/purl/1140350.
@article{osti_1140350,
title = {Atom-scale covalent electrochemical modification of single-layer graphene on SiC substrates by diaryliodonium salts},
author = {Gearba, Raluca I. and Mueller, Kory M. and Veneman, Peter A. and Holliday, Bradley J. and Chan, Calvin K. and Stevenson, Keith J.},
abstractNote = {Owing to its high conductivity, graphene holds promise as an electrode for energy devices such as batteries and photovoltaics. However, to this end, the work function and doping levels in graphene need to be precisely tuned. One promising route for modifying graphene’s electronic properties is via controlled covalent electrochemical grafting of molecules. We show that by employing diaryliodonium salts instead of the commonly used diazonium salts, spontaneous functionalization is avoided. This then allows for precise tuning of the grafting density. Moreover, by employing bis(4-nitrophenyl)iodonium(III) tetrafluoroborate (DNP) salt calibration curves, the surface functionalization density (coverage) of glassy carbon was controlled using cyclic voltammetry in varying salt concentrations. These electro-grafting conditions and calibration curves translated directly over to modifying single layer epitaxial graphene substrates (grown on insulating 6H-SiC (0 0 0 1)). In addition to quantifying the functionalization densities using electrochemical methods, samples with low grafting densities were characterized by low-temperature scanning tunneling microscopy (LT-STM). We show that the use of buffer-layer free graphene substrates is required for clear observation of the nitrophenyl modifications. Furthermore, atomically-resolved STM images of single site modifications were obtained, showing no preferential grafting at defect sites or SiC step edges as supposed previously in the literature. Most of the grafts exhibit threefold symmetry, but occasional extended modifications (larger than 4 nm) were observed as well.},
doi = {10.1016/j.jelechem.2015.05.009},
url = {https://www.osti.gov/biblio/1140350},
journal = {Journal of Electroanalytical Chemistry},
issn = {1572-6657},
number = C,
volume = 753,
place = {United States},
year = {2015},
month = {5}
}
Search WorldCat to find libraries that may hold this journalWeb of Science
Figures / Tables:
Figure 1: (a) Schematic showing the covalent grafting of DNP to a glassy carbon (GC) surface. (b) Sequential cyclic voltammograms of the reduction of a 1.0 mM solution of DNP in CH 3CN containing 0.1 M TBAPF 6 using a GC working electrode. The scan rate is 50 mV smore »
Figures / Tables found in this record: