Stacking Modes-Induced Chemical Reactivity Differences on

Subscriber access provided by Kaohsiung Medical University

Surfaces, Interfaces, and Applications

Stacking-Modes-Induced Chemical Reactivity Differences on CVD-Grown Trilayer Graphene Yao Ding, Ruizhe Wu, Irfan Haider Abidi, Hoilun Wong, Zhenjing Liu, Minghao Zhuang, Li-Yong Gan, and Zhengtang Tom Luo ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b05635 • Publication Date (Web): 19 Jun 2018 Downloaded from http://pubs.acs.org on June 20, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Stacking-Modes-Induced Chemical Reactivity Differences on CVD-Grown Trilayer Graphene

Yao Ding1, Ruizhe Wu1, Irfan Haider Abidi1, Hoilun Wong1, Zhenjing Liu1, Minghao Zhuang1, Li-Yong Gan2* and Zhengtang Luo1* 1 Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong 2 School of Materials Science and Engineering, Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641, P.R. China Email: [email protected]; [email protected] Abstract Trilayer graphene (TLG) synthesized by chemical vapor deposition (CVD), in particular for the twisted TLGs, exhibits sophisticated electronic structures that depend on their stacking modes. Here, we computationally and experimentally demonstrate the chemical reactivity differences of CVD-TLG induced by the stacking modes and corroborated by a photo-excited phenyl grafting reaction. The experimental results show that the ABA stacking TLGs have the most inert chemical property, yet 30°-30° stacking twisted TLGs are the most active. Further density functional theory (DFT) calculations have shown that the chemical reactivity difference can be quantitatively explained by the differences due to the number of hot electrons generated in their valence band (VB) during irradiation. The activity difference is further verified by the calculated adsorption energy of phenyl on the TLGs. Our work provides insight into the chemistry of TLG and addresses the challenges associated with selective functionalization of the TLG with phenyl groups. The understandings developed in this project can also guide the future development of TLG based functional devices.

1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Keywords: trilayer graphene; band structures; DFT calculations; stacking modes; photo-excited reaction

Introduction Trilayer graphene (TLG), including three graphene layers stacked with different rotation angles (θ), has shown to possess intriguing physical1,2 and electronic3,4 characteristics in the fundamental researches, making them excellent candidates for use in next generation, nanoscale functional devices. Analogous to the bilayer graphene (BLG), recent theoretical studies have shown that the stacking orders, Bernal (θ=0°) or twisted (0° AB-30° > ABA, agreeing well with experimental observations (for details, please see the Experimental Section). The reaction mechanism between BPO and graphene is a hot electron transfer reaction as revealed by previous works on single layer and bilayer graphene10,22. Here, in our case, once the TLG surface is exposed to incident lasers, the electrons initially in the valence band (VB) is excited to the conduction band (CB), and then transferred to the lowest unoccupied molecular orbital (LUMO) of phenyl radicals released by BPO molecules. The excited electrons transferred between TLG and BPO molecules can be described in Eq. 2.

∝ " /0. # , %& '( ()*% )

+ ⁄+,+

120

Where,

.

Eq. 2

is the possibility that electrons can be transferred from TLG to the

LUMO of phenyl groups. 120 is the Fermi energy of TLG, /0. is the 10


Page 11 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


energy level after graphene been exited by lasers. # , %& is the distribution of hot electron caused by the irradiation, which correlates closely with the density of states (DOS) in TLG. '( is the potential barrier between TLG and BPO for excited electrons tunneling at CB. The term ()*% )

+ ⁄+,+

, which is only related to the

energy distribution of LUMO orbital of BPO ()*% ), is a constant. Therefore, the term that will only affect the possibility of hot electrons transferred from TLG to BPO is # , %& which can be varied in different stacking of TLG. In addition, we found that the enhanced reactivity has both contributions from 1) an enhanced absorption energy and 2) the enhanced DOS, similar to a previous report.31 Figure 6b shows the plots of the calculated DOS of the four stacking modes TLG (ABA, AB-30°/30°-AB and 30°-30° stacking modes). When the laser (i.e. 514 nm, 2.41 eV) irradiates the graphene surface, electrons in the VB of graphene is excited to the CB and then transferred to the LUMO of phenyl groups (gray dash line in Figure 6b). According to our DFT calculations, the LUMO of a phenyl group is at -3.09 eV, consistent with the previous report.32 Therefore, the electrons in the VB of graphene at around -5.50 eV should be excited to the CB by adsorbing the photo energy (2.41 eV) from the incident light. To compare the electrons density at -5.50 eV in the four types of stacking modes, the zoomed in image of the DOS around -5.50 ±0.01 eV according to Figure 6b is shown in Figure S8. It can be seen that the DOS was obviously varied with the four types of TLG. Specifically, their values follow an order of 30°-30° > 30°-AB > AB-30° > ABA stacking mode. The high electron density of 30°-30° stacking mode TLG is due to the softened interlayer coupling, while for ABA stacking the energy dispersion can be almost regarded as the superposition of the monolayer massless linear bands and the parabolic Bernal-like bands.3,4 Moreover, if the 633 nm is used as a comparison, a similar result (i.e. Figure S9 in Supporting Information) is 11



obtained. This sequence obtained based on DFT calculations indicates that the 30°-30° stacking mode of TLG will have the largest amount of electrons to be excited to the excitation state under illumination, while the most inert ABA stacking mode has the smallest. Therefore, the largest amount of hot electrons which can be excited shows the highest chemical reactivity during the phenyl group grafting for 30°-30° stacking mode of TLG, consistent with the above experimental results.

Conclusions In summary, we observed the chemical reactivity differences between different stacking modes of TLG. DFT and adsorption energy calculations show that these chemical reactivity differences arose from the DOS varieties in the valence band of TLG with different stacking modes. The calculation results are supported by the experiments through a grafting reaction between BPO and TLG. The most distorted 30°-30° stacking mode of TLG has the highest reactivity, while the ABA stacking mode TLG is the most inert. Compared with the works on chemical modification with BLG, our work extends one step further to investigate the stacking effect on the chemical reactivity of TLG. Therefore, we believe that such insightful research on the fundamental researches of TLG can pave an approach to controllable modify the physical properties of TLG with tunable band gap and electrical properties.

Experimental Section CVD synthesis of TLG on copper foil: The trilayer graphene with different stacking modes was synthesized using a copper-catalyzed CVD method, as previously reported by our group.11 Before the CVD growth, the copper foil (25 µm, Aldrich Sigma, 99.8 % metal trace) was chemically polished by acetic acid for 5 minutes to remove the 12


Page 12 of 25

Page 13 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


surface contaminations. Then, it was preoxidized at 200 °C for 5 minutes to generate nucleation sites for graphene domains. Thereafter, the Cu foil was loaded in the CVD chamber and flushed with a stream of Ar to flush the chamber. The CVD process started with heating the tube furnace to 1040 °C under flow Ar/H2 mix (300/10 sccm), and annealed the Cu foil for 30 minutes. By using both the pre-oxidation and Ar/H2 annealing steps, we can control the graphene nucleation density to have more exposed Cu surface in order to generate active carbon species and enlarge TLG grains.21 The TLG growth commenced by introducing CH4 (500 ppm in Ar, at rate of 5 sccm) into the chamber, and growth continued for one hour to obtain TLG domains. Finally, the growth was terminated by sliding the Cu foil out of the reaction chamber and cooled down under the stream of Ar/H2 mixture. Transfer of TLG onto substrate: The synthesized CVD-graphene was then transferred, using a clean bubbling transfer method,11 onto a 300 nm oxide silicon wafer (SiO2/Si) with pre-deposited alignment markers defined by Electron Beam Lithography (EBL). On chip functionalization by BPO: Benzoyl peroxide (BPO, >98.0%, Tokyo Chemical Industry Co.Ltd), was used to functionalize the TLGs. More specifically, the graphene/SiO2 wafer was spin-coated with a droplet of solution containing BPO (0.1±0.05 wt%) and toluene. After spin-coating, samples were continually washed by DI water, acetone and ethanol to remove excess reactants on the graphene surface. Since both the BPO and the toluene molecules have the benzene rings and can form π-π interaction with graphene, it is difficult to fully wash the toluene while at the same time maintaining the plenty of BPO molecules for reaction at the same time. However, this will not affect the experiment results since the D band of TLG in Raman test will not be affected by toluene under laser irradiation, as shown in Figure S6. 13



Page 14 of 25

Raman characterization: The Raman spectrum was studied with a Micro-Raman system (Renishaw RM300) with three laser sources at room temperature. The excitation source used in this study were 514 nm with 2.5 mW, 633 nm with 1.7 mW and 1064 nm with 1.13 mW. Numerical aperture of 5× and 100× objective lens (DFC 290 Leica Camera Company) with a standard grating (holographic 1800 mm-1) were used during the characterization. The laser spot size is 1-2 µm. DFT calculations: First-principles calculations were performed using the Vienna Ab-Initio Simulation Package with Perdew-Burke-Ernzerhof exchange correlation functional.33 A cutoff energy of 500 eV was used for the plane-wave expansion.33,34 As shown in Figure S2, a 6√3 × 6√3 lateral periodicity of the twisted graphene (by 30°) and a 7×7 lateral periodicity of the untwisted graphene were employed to model the trilayers, which included a lattice mismatch of 1.03%. Correspondingly, the four types of TLG contained 294 (ABA, Figure S2a), 292 (AB-30° and 30°-AB, Figure S2b & S2c), and 290 atoms (Figure S2d), respectively. The Brillouin zone was sampled by a gamma centered 3 × 3 × 1 k-mesh geometry optimization and 7 × 7 × 1 k-mesh for density of states calculations. In each case, we applied a vacuum thickness of at least 20 Å in the z-direction to separate the neighboring slabs. Due to the absence of strong chemical bonding between graphene layers, we employed a damped van der Waals correction to accurately describe the π-π stacking interaction during the calculations. This was also used in previous reports.5, 35-40 The adsorption energies are defined as ∆ = − ( + )

Eq. 3

where and are the total energies of a TLG surface with and without phenyl radical adsobed, respectively. is the total energy of an isolated phenyl radical. XPS characterizations: The XPS test was conducted using the Kratos Axis Ultra DLD 14


Page 15 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


multi-technique surface analysis system with a Lens Mode: Hybrid; Resolution: Pass energy 20 eV; Dwell Time (ms): 2857 for C1s and with a Lens Mode: Hybrid; Resolution: Pass energy 40 eV; Dwell Time (ms): 889 for N1s. Acknowledgements This project was supported by the Research Grant Council of Hong Kong SAR (Project number 16204815), NSFC-RGC Joint Research Scheme (N_HKUST607/17), the Innovation and Technology Commission (ITC-CNERC14SC01 and ITS/267/15), the

Guangzhou

Science

&

Technology

(Project

2016201604030023

and

201704030134) and the National Natural Science Foundation of China (No. 11504303). Technical assistance from the Materials Characterization and Preparation Facilities is greatly appreciated. The authors also thank the National Supercomputing Center in Guangzhou (Tianhe II supercomputer) for providing computational resources and technical support.

15



Supporting Information This material is available free of charge via the Internet at http://pubs.acs.org. Additional information includes, statistic summarization of the average intensity ratio of D and G peaks (ID/IG); side and top views of the four types of TLG for calculations with simulation; X-ray photoelectron spectroscopy (XPS) results; standard deviations (σ) for t* in Figure 4; OM images for AB-twisted TLG with different rotation angles; Raman spectra for bilayer area of twisted-AB stacking modes TLG with various rotation angles. (with 514 and 633 nm illuminations); SAED patterns for twisted TLG with different rotation angles; the influence of toluene on D band enhancement in reaction; Raman mapping images for a AB-twisted stacking TLG flake before and after functionalization; zoomed in image of Figure 6b with x-axis as -5.51~-5.49 eV, and zoomed in image of Figure 6b with x-axis as -5.03~-5.05 eV.

16


Page 16 of 25

Page 17 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


References [1]

[2]

[3]

[4] [5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13] [14]

Craciun, M.; Russo, S.; Yamamoto, M.; Oostinga, J. B.; Morpurgo, A.; Tarucha, S. Trilayer graphene is a semimetal with a gate-tunable band overlap. Nat. Nanotechnol., 2009, 4, 383-388. Bao, W.; Jing, L.; Velasco Jr, J.; Lee, Y.; Liu, G.; Tran, D.; Standley, B.; Aykol, M.; Cronin, S.B.; Smirnov, D.; Koshino, M.; McCann, E.; Bockrath, M.; Lau, C. N. Stacking-dependent band gap and quantum transport in trilayer graphene. Nat. Phys., 2011, 7, 948-952. Zhu, W.; Perebeinos, V.; Freitag, M.; Avouris, P. Carrier scattering, mobilities, and electrostatic potential in monolayer, bilayer, and trilayer graphene. Phys. Rev. B, 2009, 80, 235402. Morell, E. S.; Pacheco, M.; Chico, L.; Brey, L. Electronic properties of twisted trilayer graphene. Phys. Rev. B, 2013, 87, 125414,. Wang, Y.-P.; Li, X.-G.; Fry, J. N.; Cheng, H.-P. First-principles studies of electric field effects on the electronic structure of trilayer graphene. Phys. Rev. B, 2016, 94, 165428. Datta, B.; Dey, S.; Samanta, A.; Agarwal, H.; Borah, A.; Watanabe, K.; Taniguchi, T.; Sensarma, R.; Deshmukh, M. M.; Agarwal, H. Strong electronic interaction and multiple quantum Hall ferromagnetic phases in trilayer graphene. Nat. Commun., 2017, 8, 14518. Cao, Y.; Fatemi, V.; Fang, S.; Watanabe, K.; Taniguchi, T.; Kaxiras, E.; Herrero-J., P. Unconventional superconductivity in magic-angle graphene superlattices. Nature, 2018, 556, 43. Cong, C.; Yu, T.; Sato, K.; Shang, J.; Saito, R.; Dresselhaus, G.; Dresselhaus, M. Raman characterization of ABA-and ABC-stacked trilayer graphene. ACS Nano, 2011, 5, 8760-8768. Cao, H., Guo, Z.; Xiang, H.; Gong, X. Layer and size dependence of thermal conductivity in multilayer graphene nanoribbons. Phys. Lett. A, 2012, 376, 525-528. Liao, L.; Wang, H.; Peng, H.; Yin, J.; Koh, A. L.; Chen, Y.; Xie, Q.; Peng H.; Liu, Z. van Hove singularity enhanced photochemical reactivity of twisted bilayer graphene. Nano Lett., 2015, 15, 5585-5589. Ding, Y.; Peng, Q.; Gan, L.; Wu, R.; Ou, X.; Zhang, Q.; Luo, Z. Stacking-Mode-Induced Reactivity Enhancement for Twisted Bilayer Graphene. Chem. Mat., 2016, 28, 1034-1039. Vecera, P.; Eigler, S.; Koleśnik-G., M.; Krstić, V.; Vierck, A.; Maultzsch, J.; Schäfer, R. A.; Hauke, F.; Hirsch, A. Degree of functionalisation dependence of individual Raman intensities in covalent graphene derivatives. Sci. Rep., 2017, 7, 45165. Dai, L.; Functionalization of graphene for efficient energy conversion and storage. Accounts Chem. Res., 2012, 46, 31-42. Bissett, M. A.; Takesaki, Y.; Tsuji, M.; Ago, H. Increased chemical reactivity achieved by asymmetrical ‘Janus’ functionalisation of graphene. RSC Adv., 2014, 4, 52215-52219. 17



[15]

[16]

[17]

[18]

[19]

[20] [21]

[22]

[23]

[24] [25]

[26]

[27]

[28]

Vlassiouk, I. V.; Stehle, Y.; Pudasaini, P. R.; Unocic, R. R.; Rack, P. D.; Baddorf, A. P.; Ivanov, I. N.; Lavrik, N. V.; List, F.; Gupta, N.; Bets, K. V.; Yakobson, B. I.; Smirnov, S. N. Evolutionary selection growth of two-dimensional materials on polycrystalline substrates. Nat. Mater., 2018, 17(4), 318-322. Deokar, G.; Avila, J.; Razado-C., I.; Codron, J.L.; Boyaval, C.; Galopin, E.; Asensio, M. C.; Vignaud, D. Towards high quality CVD graphene growth and transfer. Carbon, 2015, 89, 82-92. Abidi, I. H.; Liu, Y.; Pan, J.; Tyagi, A.; Zhuang, M.; Zhang, Q.; Cagang, A. A.; Weng, L.-T.; Sheng, P.; Goddard, W. A.; Luo, Z. Regulating Top-Surface Multilayer/Single-Crystal Graphene Growth by “Gettering” Carbon Diffusion at Backside of the Copper Foil. Adv. Funct. Mater., 2017, 27, 1700121 . Gao, Z.; Zhang, Q.; Naylor, C. H.; Kim, Y.; Abidi, I. H.; Ping, J.; Ducos, P.; Zauberman, J.; Zhao, M.-Q.; Rappe, A. M.; Luo, Z.; Ren, L.; Johnson, A. T. Charlie. Crystalline Bilayer Graphene with Preferential Stacking from Ni-Cu Gradient Alloy. ACS Nano, 2018, 12, 2275-2282,. Yan, Z.; Liu, Y.; Ju, L.; Peng, Z.; Lin, J.; Wang, G.; Zhou, H.; Xiang, C.; Samuel, E.L.G.; Kittrell, C.; Artyukhov, V. I.; Wang, F.; Yakobson, Boris. I.; Tour, J. M. Large Hexagonal Bi-and Trilayer Graphene Single Crystals with Varied Interlayer Rotations. Angew. Chem. Int. Ed., 2014, 126, 1591-1595. Park, K.; Ryu, S. Direction-Controlled Chemical Doping for Reversible G-Phonon Mixing in ABC Trilayer Graphene. Sci. Rep., 2015, 5, 8707. Gan, L.; Luo, Z. Turning off hydrogen to realize seeded growth of subcentimeter single-crystal graphene grains on copper. Acs Nano, 2013, 7, 9480-9488. Liu, H.; Ryu, S.; Chen, Z.; Steigerwald, M. L.; Nuckolls, C.; Brus, L. E. Photochemical reactivity of graphene. J. Am. Chem. Soc., 2009, 131, 17099-17101. Zhao, H.; Lin, Y.-C.; Yeh, C.-H.; Tian, H.; Chen, Y.-C.; Xie, D.; Yang, Y.; Suenaga, K.; Ren, T.-L.; Chiu, P.-W. Growth and Raman spectra of single-crystal trilayer graphene with different stacking orientations. ACS Nano, 2014, 8, 10766-10773. Malard, L.; Pimenta, M.; Dresselhaus, G.; Dresselhaus, M. Raman spectroscopy in graphene. Phys. Rep., 2009, 473, 51-87. Nair, N.; Kim, W.-J.; Usrey, M. L.; Strano, M. S. A Structur-Reactivity relationship for single walled carbon nanotubes reacting with 4-hydroxybenzene diazonium salt. J. Am. Chem. Soc., 2007, 129, 3946-3954. Ferreira, E. M.; Moutinho, M. V.; Stavale, F.; Lucchese, M.; Capaz, R. B.; Achete, C.; Jorio, A. Evolution of the Raman spectra from single-, few-, and many-layer graphene with increasing disorder. Phys. Rev. B, 2010, 82, 125429. Cançado, L.; Jorio, A.; Pimenta, M. Measuring the absolute Raman cross section of nanographites as a function of laser energy and crystallite size. Phys. Rev. B, 2007, 76, 064304. Peng, H.; Schröter, N.; Yin, J.; Wang, H.; Chung, T.-F.; Yang, H.; Ekahana, S.; 18


Page 18 of 25

Page 19 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


[29]

[30]

[31]

[32]

[33] [34] [35]

[36] [37]

[38]

[39] [40]

Liu, Z.-K.; Jiang, J.; Yang, L.-X.; Zhang, T.; Chen, C.; Ni, H.; Barinov, A.; Chen, Y.-P.; Liu, Z.-F.; Peng, H.-L.; Chen, Y.-L. Substrate Doping Effect and Unusually Large Angle van Hove Singularity Evolution in Twisted Bi-and Multilayer Graphene. Adv. Mater., 2017, 29, 27. Kim, K.; Coh, S.; Tan, L. Z.; Regan, W.; Yuk, J. M.; Chatterjee, E.; Crommie, M. F.; Cohen, M. L.; Louie, S. G.; Zettl, A. Raman spectroscopy study of rotated double-layer graphene: misorientation-angle dependence of electronic structure. Phys. Rev. Lett., 2012, 108, 246103. Wang, Y.; Su, Z.; Wu, W.; Nie, S.; Xie, N.; Gong, H.; Guo, Y.; Lee, J.-H.; Xing, S.-R.; Lu, X.-X.; Wang, H.-Y.; Lu, X.-H.; McCarty, K.; Pei, S.-S.; Robles-H., F.; Hadjiev, V. G.; Bao, J.-M., Resonance Raman spectroscopy of G-line and folded phonons in twisted bilayer graphene with large rotation angles. Appl. Phys. Lett., 2013, 103, 123101. Hammer, B.; Noerskov, J. K. ChemInform Abstract: Theoretical Surface Science and Catalysis — Calculations and Concepts. Cheminform, 2000, 31. Lee, J.; Min, K.-A.; Hong, S.; Kim, G. Ab initio study of adsorption properties of hazardous organic molecules on graphene: Phenol, phenyl azide, and phenylnitrene. Chem. Phys. Lett., 2015, 618, 57-62. Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett., 1996, 77, 3865. Kresse, G.; Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B, 1999, 59, 1758. Grimme, S. Accurate description of van der Waals complexes by density functional theory including empirical corrections. J. Comput. Chem., 2004, 25, 1463-1473. Mapasha, R. E.; Ukpong, A. M.; Chetty, N. Ab initio studies of hydrogen adatoms on bilayer graphene. Phys. Rev. B, 2012, 85, 205402. Park, C.; Ryou, J.; Hong, S.; Sumpter, B. G.; Kim, G.; Yoon, M. Electronic properties of bilayer graphene strongly coupled to interlayer stacking and an external electric field. Phys. Rev. Lett., 2015, 115, 015502. Jang, W.; Lee, J.; In, C.; Choi, H.; Soon, A. Designing Two-Dimensional Dirac Heterointerfaces of Few-Layer Graphene and Tetradymite-Type Sb2Te3 for Thermoelectric Applications. ACS Appl. Mater. Interfaces., 2017, 9, 42050-42057. Zhang, F.; Sahu, B.; Min, H.; MacDonald, A. H. Band structure of A B C-stacked graphene trilayers. Phys. Rev. B, 2010, 82, 035409. Wang, Y.; Wang, H.; Gao, J.-H.; Zhang, F.-C. Layer antiferromagnetic state in bilayer graphene: A first-principles investigation. Phys. Rev. B, 2013, 87, 195413.

19



Figure 1. Schematic illustration of the reaction between benzoyl peroxide molecules (BPO) and trilayer graphene (TLG). When BPO is excited by a laser under a nitrogen protected environment, the generated free radicals will allow phenol groups to be grafted on the TLG.

20


Page 20 of 25

Page 21 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2. Stacking modes of TLG. (a,b,c&d) Optical images of the bilayer (BL) and trilayer (TL) domains of ABA, AB-30°, 30°-AB, 30°-30° stacking modes, respectively. Inset: the single- (SL) and bi-layer domains of the TLG. The black (SL), green (BL) and red (TL) dots indicate spots for Raman collection. The black dash lines outline the edges of the hexagonal graphene. Inset scale bar, 50 µm. (e,f,g&h) Schematic drawing of the four types of TLG in (a,b,c&d). (i,j,k&l) Raman spectra of a,b,c&d,. The black, green and red lines indicate the Raman spectra of the SL, BL and TL area in four types of TLG, respectively.

21



Figure 3. Raman spectra of different grafting times. All the reactions and Raman spectra were collected under 514 nm laser. (a), (b), (c) and (d) are presented for ABA, AB-30°, 30°-AB and 30°-30° stacking modes, respectively. D band around 1350 cm-1 is highlighted under the red shadow. The Raman spectra were taken for different time intervals (0, 10, 30 and 60 s) under the illumination.

22


Page 22 of 25

Page 23 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. ID/IG ratio evolution of four types of TLG for phenyl group grafting reaction (λincident=514 nm).

23



Figure 5. Resonance effect. (a) Raman spectra of 10 s reaction for AB-10° (top pattern) and 10°-AB (bottom pattern) TLG under the irradiation of 514 nm (green line) and 633 nm (red line). (b) 10 s reaction for AB-13° (top pattern) and 13°-AB (bottom pattern) TLG. (c) Statistical counts of the ID/IG ratios for these four types of TLG from 10 pairs of samples for the reaction triggered by 514 nm and 633 nm lasers after 10 s.

24


Page 24 of 25

Page 25 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. DFT calculation of hot electron transfer between TLG and BPO. (a) Adsorption energy (∆ ) for phenyl groups on the surface of four types of TLG. (b) Calculated DOS for the four types of TLG. The dash line (-3.09 eV) indicates the LUMO of a phenyl radical. The solid line (-5.50 eV) indicates the photoexcited energy level of graphene. Inset: zoom in DOS around -5.50 (80.01) eV. The vacuum level is set to zero. Among the four types of graphene, the DOS shows remarkable differences at the photoexcited energy level. The zoomed in image of the orange rectangle area is shown in SI, Figure S8.

25


Stacking Modes-Induced Chemical Reactivity Differences on

Recommend Documents