View Article Online View Journal ChemComm Accepted Manuscript

This article can be cited before page numbers have been issued, to do this please use: W. Wang, J. Gu, W. Hua, X. Jia and K. Xi, Chem. Commun., 2014, DOI: 10.1039/C4CC03306J. This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication.

Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available.

You can find more information about Accepted Manuscripts in the Information for Authors.

Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

www.rsc.org/chemcomm Page 1 of 3 ChemComm

Journal Name RSCPublishing View Article Online DOI: 10.1039/C4CC03306J COMMUNICATION

A novel high efficiency composite catalyst: single crystal triangle Au nanoplates supported by functional Cite this: DOI: 10.1039/x0xx00000x reduced graphene oxide

a a b *a *b Received 00th January 2012, Weina Wang, Jiangjiang Gu, Wenwen Hua , Xudong Jia and Kai Xi Accepted 00th January 2012

DOI: 10.1039/x0xx00000x

www.rsc.org/ To improve the utilization efficiency of Au catalyst, triangle dimensional nanoplates may lead to a more efficient utilization of Au nanoplates on functional reduced graphene oxide were noble metal, and perform better in catalysis. prepared by a facile method. The products with ultra-low The coordinate bond between Au and amine group is extremely trace amounts of Au afforded high catalytic efficiency for the strong18. When Au is loaded on amino group-functionalized reduction of 4-nitro phenol. The morphology of the products graphene, Au atoms are then fixed onto the functional graphene. was controlled by tuning the addition of HAuCl4. When metal atoms are limited on a flat surface, the crystal grows Manuscript rapidly in two-dimensional space but extremely slowly in the third 1-3 Au catalysts are extremely attractive during the last decade , dimension19. That will help to synthesize two-dimensional Au but the heavy demand of Au limits their application. Improving material supported by graphene. the utilization of Au is still a challenge for scientists. Graphene is In order to improve the catalytic efficiency and the utilization of considered to be excellent supporting material due to its large Au, we designed and synthesized the composite nanomaterial by 4 surface area and unique interaction with catalyst particles . Au with two-dimensional gold nanostructure dispersing on Metallic nanomaterials on graphene nanosheets not only prevent functional reduced graphene oxide (FRGO). The as-prepared Au 5 the aggregation of graphene, but also bear multiplex functions . nanoplates have regular triangular shape. The products with Graphene composites with noble metal nanoparticles, such as ultralow trace amounts of Au (4.16*10-6 mol · L-1) showed high Au, Pt, Pd and Ag nanoparticles have become attractive for their catalytic activity in liquid-phase reduction of 4-nitro phenol (4-NP). applications in novel catalysts, biosensors, gene delivery vectors, Accepted surface enhanced Raman bases and electrochemical nanoprobes6-11. These materials have been prepared by diverse methods such as seed-mediated method and electrochemical method. However, the shape of nanoparticles is usually Published on 22 May 2014. Downloaded by NANJING UNIVERSITY 25/06/2014 03:07:50. restricted to dot-like. Two-dimensional nanomaterial on graphene has rarely been reported. Nanoplates have a large number of surface and boundary atoms. The synthesis of two-dimensional nanostructures with well-controlled morphology is important in achieving high performance catalysts.The composite material Scheme 1. The synthetic procedure for the Au nanoplates supported by with large specific surface area is highly desirable and has great functional reduced graphene oxide. potential for future practical applications and fundamental studies of graphene-based nanocatalysts. The synthetic procedures of the Au nanoplates supported by ChemComm The graphene supported metal nanoparticles with high catalytic FRGO are shown in Scheme 1. Graphene oxide was modified efficiency have been investigated12. It is known that the size and with N-propyl ethylene diamine, and then reduced by hydrazine shape of nanocrystal is essential for improving catalytic hydrate. The as-prepared FRGO was followed by mixing with properties. Supporting effect and particle size effect on the Au chloroauric acid (HAuCl4). Since the strong interaction between catalysis have been substantiated with a number of Au amino group and aurum ion, chloroauric acid tended to adsorb catalysts13, 14. Two-dimensional noble metal nanomaterials are on the FRGO. When sodium borohydride (NaBH4) was added to almost crystallographically isotropic, and have large surface area thissystem,theAucrystalwasformedontheFRGO.The and high stability13, 15-17. Hence, graphene-supported two- synthesis of FRGO-Au with different proportions of FRGO and

This journal is © The Royal Society of Chemistry 2012 J. Name., 2012, 00,1‐3|1 ChemComm Page 2 of 3 COMMUNICATION Journal Name

HAuCl4 (FRGO-Au1, FRGO-Au10 and FRGO-Au100) was growing mechanism of the nanoplates. In addition, the tiny displayed in ESI. triangular plates were formed in the initial period, and would be View Article Online transformed into larger triangular, hexagonal,DOI: truncated10.1039/C4CC03306J triangular and other symmetrical structures (Figure S9).

Figure 1. (a) TEM image of a typical Au nanoplates supported by FRGO, (b) HRTEM image of a typical Au nanoplates supported by FRGO, (c) lattice fringes image of Au plates, (d) FFT of the lattice fringe image. Figure 2. (a) Scheme of the nanoplates growing mechanism, (b) TEM image of FRGO‐Au1, (c) TEM image of FRGO‐Au100, inset is a representative hexagonal A series of analyses were carried out to study FRGO (ESI Figure nanoplate. S1-S4). These results proved that well-distributed FRGO nanosheets had successfully been synthesized. The energy Figure 2 (a) shows the growing mechanism of the nanoplates. dispersive X-Ray spectroscopy (EDX) analysis and X-ray During the synthesis of the Au nanoplates, the FRGO acted not photoelectron spectroscopic (XPS) analysis (ESI Figure S5 and only as supporting material but also as template and modifying ‐ S6) of Au nanoplates supported by FRGO indicated that Au was agent. When HAuCl4 was mixed with FRGO, AuCl4 was distributed on the FRGO. The transmission electron microscope concentrated on FRGO by coordinate bond between Au and (TEM) image and high resolution transmission electron secondary amine group. The gold atoms were limited on the microscope (HRTEM) image of a typical Au nanoplates FRGO surface. When the reducing agent was added, the Au

15, 20, 22 Manuscript supported by FRGO (FRGO-Au10) are shown in Figure 1. The crystals growed along close packing plane, {111} plane . TEM image indicated that the Au nanoplates on FRGO were Furthermore, the secondary amine groups adsorbing on the sites nanometer-sized and mostly triangular. The HRTEM image of the {111} planes of Au greatly decreased the surface energy of demonstrated that the lattice fringes were clear. The interplanar the planes, thus the Au crystal further grew and formed triangular structure (AFM image of the triangular structure in FRGO-Au100 spacing was 0.235 nm, which was consistent with d111 of a face- centred cubic structure (0.2355 nm)20. The fast Fourier transform was shown in ESI Figure S10). When the amount of HAuCl4 23 (FFT) of the lattice fringe image is also shown in Figure 1. The further increased, the tiny triangular nanoplates acted as seeds . result indicated that the triangular nanoplate on FRGO was Then they grew into larger triangular, hexagonal, truncated single and crystalline21. The crystal structure of these nanoplates triangular and other symmetrical structures, which were was characterized with powder X-ray diffraction (XRD) patterns thermodynamically stable. Accepted (ESI Figure S7). In addition to the strong (111) diffraction peak, the other diffraction peaks of face-centered cubic structure were also present. These diffraction peaks were weak, less than one- third of that of the (111) peak. Thus the Au nanoplates on FRGO were single-crystalline with {111} lattice planes as the basal Published on 22 May 2014. Downloaded by NANJING UNIVERSITY 25/06/2014 03:07:50. plane, which was consistent with the previous reports on the structural characterization of Au nanoplates15, 16. Control experiments without rGO or functional group were carried out to confirm the function of FRGO for the shape control of Au nanoplates. There were no triangular plates in the two products (ESI Figure S8). For further study of the influencing factors on the formation of Au nanoplates, a series of products

were prepared by varying the proportions of FRGO and HAuCl4 ChemComm (FRGO-Au1, FRGO-Au10 and FRGO-Au100). The TEM images Figure 3. (a) Scheme of the reduction of 4‐NP, (b) Reaction time of different of FRGO-Au1, FRGO-Au10 and FRGO-Au100 are shown in catalysts when the conversion of 4‐NP reaches 99%. Figure 2 (b), Figure 1 (a) and Figure 2 (c), respectively. It was obvious that the size of the Au nanoplates on FRGO increased The catalytic reduction of 4-NP by NaBH4 is chosen as a model to determine the catalytic properties of synthetic Au nanoplates significantly with the increase of HAuCl4. Moreover, the smallest 24 Au nanoplates on FRGO (FRGO-Au1) mainly showed triangular supported by FRGO . The results are illustrated in Figure 3. The shape, while the larger plates (FRGO-Au100) exhibited more reduction does not take place without catalyst. When a trace hexagonal and truncated triangular structures, which implied the amount of Au nanoplates supported by FRGO was added to the

2 | J. Name., 2012, 00,1‐3 This journal is © The Royal Society of Chemistry 2012 Page 3 of 3 ChemComm Journal Name COMMUNICATION

solution, the absorption of 4-NP at 400 nm decreased 1. G. Seidel, R. Mynott and A. Fürstner, Angewandte Chemie significantly and a new absorption at around 295 nm gradually International Edition, 2009, 48, 2510-2513. View Article Online appeared. The solution varied in color from light yellow to almost 2. M. Haruta, Catalysis Today, 1997, 36, 153-166.DOI: 10.1039/C4CC03306J colorless (Figure 3a). It indicated the rapid decrease of 4-NP and 3. A. S. K. Hashmi and G. J. Hutchings, Angewandte Chemie the formation of 4-Aminophenol (4-AP). The details of the International Edition, 2006, 45, 7896-7936. reduction process were displayed in ESI. 4. A. K. Geim, science, 2009, 324, 1530-1534. We further investigated and compared the catalytic efficiencies of 5. Z. Tang, S. Shen, J. Zhuang and X. Wang, Angewandte Chemie, 2010, Au nanoplates supported by FRGO with different sizes. For the 122, 4707-4711. catalysts of FRGO-Au1, FRGO-Au10 and FRGO-Au100, the Au 6. X. Huang, S. Li, Y. Huang, S. Wu, X. Zhou, S. Li, C. L. Gan, F. contents in the reactions were all the same. This reaction could Boey, C. A. Mirkin and H. Zhang, Nature communications, 2011, 2, be monitored by UV-vis absorption spectroscopy. The 292. conversion of 4-NP could be calculated by the absorption at 400 7. Y. Mao, T. J. Park, F. Zhang, H. Zhou and S. S. Wong, Small, 2007, nm. For all of the three samples, the reaction was completed in 3 3, 1122-1139. minutes (ESI Figure S11). Figure 3 (b) demonstrated the reaction 8. H. Zhang, D. Song, S. Gao, J. Zhang, H. Zhang and Y. Sun, Sensors time for different samples when the conversion of 4-NP reached and Actuators B: Chemical, 2013, 188, 548-554. 99%. When FRGO-Au1 was used, as much as 99% of 4-NP was 9. F.-F. Cheng, W. Chen, L.-H. Hu, G. Chen, H.-T. Miao, C. Li and J.-J. reduced in just 12 seconds. The 4-NP conversion rate catalyzed Zhu, J. Mater. Chem. B, 2013, 1, 4956-4962. by FRGO-Au1 in 6 cycles was shown in ESI Figure S12. Even to 10. J. Huang, L. Zhang, B. Chen, N. Ji, F. Chen, Y. Zhang and Z. Zhang, the sixth cycle, the 4-NP conversion rate remained high level Nanoscale, 2010, 2, 2733-2738. (about 95 %). The reaction time was significantly shorter 11. S. Song, Y. Qin, Y. He, Q. Huang, C. Fan and H.-Y. Chen, Chemical compared to that using the pure Au nanoparticles (ESI Figure Society Reviews, 2010, 39, 4234-4243. S13) and the reported Au nanoparticles composited with 12. L. Shang, T. Bian, B. Zhang, D. Zhang, L. Z. Wu, C. H. Tung, Y. Yin graphene25. It may be attributed to that the nanocomposites with and T. Zhang, Angewandte Chemie, 2014, 126, 254-258. thin plate structure had larger contact area to reactant compared 13. A. M. Henning, J. Watt, P. J. Miedziak, S. Cheong, M. Santonastaso, to those with dot-like structure by using the same amount of Au. M. Song, Y. Takeda, A. I. Kirkland, S. H. Taylor and R. D. Tilley, Manuscript As to Au nanoplates, they can get thinner and disperse better on Angewandte Chemie, 2013, 125, 1517-1520. FRGO when the proportion of FRGO increased. This could 14. Y. Yuan, A. P. Kozlova, K. Asakura, H. Wan, K. Tsai and Y. explain why the smallest Au nanoplates had the best catalytic Iwasawa, Journal of Catalysis, 1997, 170, 191-199. effect. Furthermore, FRGO-Au had a wide variety of practical 15. H. L. Qin, D. Wang, Z. L. Huang, D. M. Wu, Z. C. Zeng, B. Ren, K. applications. For example, the FRGO-Au1 with less addition (Au Xu and J. Jin, Journal of the American Chemical Society, 2013, 135, 2.07*10-6 M) could catalyze the reduction of para-nitroaniline. 12544-12547. The reduction was rapidly completed as the catalyst added in the 16. C. Li, W. Cai, B. Cao, F. Sun, Y. Li, C. Kan and L. Zhang, Advanced system (Electronic Supplementary Material, ESI Figure S14). Functional Materials, 2006, 16, 83-90. FRGO-Au could also catalyze the reduction of 2, 4-dinitrotoluene 17. L. Yi and M. Gao, Crystal Growth & Design, 2011, 11, 1109-1116. at room temperature in only 10 minutes26 (ESI). 18. P. Sudeep, S. S. Joseph and K. G. Thomas, Journal of the American Accepted Chemical Society, 2005, 127, 6516-6517. Conclusions 19. S. A. Morin, A. Forticaux, M. J. Bierman and S. Jin, Nano letters, 2011, 11, 4449-4455. We have designed and prepared FRGO supported Au 20. M. Grzelczak, J. Pérez-Juste, P. Mulvaney and L. M. Liz-Marzán, nanoplates by a facile, efficacious and environment-friendly Chemical Society Reviews, 2008, 37, 1783-1791. Published on 22 May 2014. Downloaded by NANJING UNIVERSITY 25/06/2014 03:07:50. method. The products show regular triangular shape. By simply 21. C. J. Johnson, E. Dujardin, S. A. Davis, C. J. Murphy and S. Mann, manipulating the amount of HAuCl , nanoplates with different 4 Journal of Materials Chemistry, 2002, 12, 1765-1770. morphologies could be obtained. The as-prepared composite 22. A. Kirkland, D. Jefferson, D. Duff, P. Edwards, I. Gameson, B. nanomaterials improves catalytic efficiency for the reduction of 4- Johnson and D. Smith, Proceedings of the Royal Society of London. NP by NaBH with ultra-low trace addition. The described 4 Series A: Mathematical and Physical Sciences, 1993, 440, 589-609. technology possesses the potential application prospect in 23. Y. Sun and Y. Xia, Science, 2002, 298, 2176-2179. environmental monitoring, biosensors and electrochemical 24. R. Liu, F. Qu, Y. Guo, N. Yao and R. D. Priestley, Chemical nanoprobes.

Communications, 2014, 50, 478-480. ChemComm Notes and references 25. B. Nam, H.-J. Lee, H. Goh, Y. B. Lee and W. San Choi, Journal of a State Key Laboratory of Coordination Chemistry, Department of Polymer Science & Engineering, Nanjing National Laboratory of Materials Chemistry, 2012, 22, 3148-3153. Microstructures, Nanjing University, Nanjing 210093, P.R. China. Fax: 26. B. Zeynizadeh and D. Setamdideh, Synthetic communications, 2006, +86-25-83621337; E-mail: [email protected] 36, 2699-2704. b Department of Polymer Science & Engineering, Nanjing University, Nanjing 210093, P.R. China. Fax: +86-25-83686197; E-mail: [email protected] † Electronic Supplementary Information (ESI) available: Experimental details and supporting data. See DOI: 10.1039/b000000x/

This journal is © The Royal Society of Chemistry 2012 J. Name., 2012, 00,1‐3|3