pubs.acs.org/Langmuir © 2009 American Chemical Society
New Strategy for Synthesis and Functionalization of Carbon Nanoparticles Hongquan Jiang,†,§ Feng Chen,^,† Max G. Lagally,† and Ferencz S. Denes*,‡,§ †
Department of Material Science and Engineering, ‡Department of Biological Systems Engineering, and § College of Engineering-Center for Plasma-Aided Manufacturing, University of Wisconsin;Madison, Madison, Wisconsin 53706, and ^Department of Materials Physics at Xi’an Jiaotong University, Xi’an, Shannxi 710049, P. R. China Received June 21, 2009. Revised Manuscript Received November 19, 2009
We describe a novel “one-step” combined synthesis and functionalization of carbon nanoparticles, using a new generation of all-in-one small submerged-arc plasma reactor that we have developed. We take advantage of long-lived free radicals generated by a submerged-arc helium atmosphere plasma and resident on the nanoparticle surfaces to supply ethylenediamine directly after the plasma to functionalize the carbon nanoparticles. XPS, TG/DTG, FTIR, and fluorescence tests confirm the viability of this new amination process. The nanoparticles are small and relatively uniformly sized. Their dispersibility in aqueous solution is significant.
Introduction Carbon nanoparticles (CNPs) have been broadly studied for use in adsorbent,1,2 composite,3 catalyst support,4-8 and electronic materials applications3 as well as use in drug delivery,9,10 medical imaging,11 cell delivery,12 and cancer vaccination.13 Their large surface area, and the ready ability to functionalize carbon, additionally allows for high-capacity binding of biomolecules. Primaryamine groups are among the most desirable reactive functionalities for carbon. Their presence on a substrate creates hydrophilic character and reactivity. They are generally more stable than secondary amines. Because functionalized carbon nanoparticles promise many opportunities in biomedicine and diagnostics, it is of continuous interest to explore improved methods for doing so. *To whom correspondence should be addressed. E-mail:
[email protected]. edu. (1) El-Sayed, Y.; Bandosz, T. J. Langmuir 2005, 21(4), 1282–1289. (2) Yue, Z. R.; Economy, J. J. Nanopart. Res. 2005, 7(4-5), 477–487. (3) Kato, M.; Ishibashi, M. Carbon Nanoparticle Composite Actuators; 4th World Congress on Biomimetics, Artificial Muscles and Nano-Bio, 2008; Journal of Physics: Conference Series: 2008; p 012003. (4) Yoon, H.; Ko, S.; Jang, J. Chem. Commun. 2007, 14, 1468–1470. (5) Rodriguez-Reinoso, F. Carbon 1998, 36(3), 159–175. (6) Oliveira, P.; Ramos, A. M.; Fonseca, I.; do Rego, A. B.; Vital, J. Catal. Today 2005, 102, 67–77. (7) Valente, A.; do Rego, A. M. B.; Reis, M. J.; Silva, I. F.; Ramos, A. M.; Vital, J. Appl. Catal., A 2001, 207(1-2), 221–228. (8) Coloma, F.; Narciso-Romero, J.; Sepulveda-Escribano, A.; RodriguezReinoso, F. Carbon 1998, 36(7-8), 1011–1019. (9) Kim, S.; Shibata, E.; Sergiienko, R.; Nakamura, T. Carbon 2008, 46(12), 1523–1529. (10) Ma, Y. H.; Manolache, S.; Denes, F. S.; Thamm, D. H.; Kurzman, I. D.; Vail, D. M. J. Biomater. Sci., Polym. Ed. 2004, 15(8), 1033–1049. (11) Sun, Y. P.; Zhou, B.; Lin, Y.; Wang, W.; Fernando, K. A. S.; Pathak, P.; Meziani, M. J.; Harruff, B. A.; Wang, X.; Wang, H. F.; Luo, P. J. G.; Yang, H.; Kose, M. E.; Chen, B. L.; Veca, L. M.; Xie, S. Y. J. Am. Chem. Soc. 2006, 128(24), 7756–7757. (12) Yan, A. H.; Lau, B. W.; Weissman, B. S.; Kulaots, I.; Yang, N. Y. C.; Kane, A. B.; Hurt, R. H. Adv. Mater. 2006, 18(18), 2373–þ. (13) Schriber, H. A.; Prechl, J.; Jiang, H.; Zozulya, A.; Fabry, Z.; Denes, F. S.; Sandor, M. Industrial Plasma Technology: Applications from Environmental to Energy Technologies; Kawai, Y., Ikegami, H., Sato, N., Matsuda, A., Uchino, K., Kuzuya, M., Mizuno, A., Eds.; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2009, pp 141–147. (14) Oh, W.-K.; Yoon, H.; Jang, J. Diamond Relat. Mater. 2009, 18(10), 1316–1320. (15) Hollahan, J. R.; Stafford, B. B.; Falb, R. D.; Payne, S. T. J. Appl. Polym. Sci. 1969, 13(4), 807–&. (16) Nakayama, Y.; Takahagi, T.; Soeda, F.; Hatada, K.; Nagaoka, S.; Suzuki, J.; Ishitani, A. J. Polym. Sci., Part A: Polym. Chem. 1988, 26(2), 559–572. (17) Lub, J.; Vanvroonhoven, F. C. B. M.; Bruninx, E.; Benninghoven, A. Polymer 1989, 30(1), 40–44.
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Primary-amine-grafted surfaces, prepared by cold-plasma techniques,10,14-29 are competitive with surfaces made by conventional chemical-amination approaches,1,6,7,30-38 for the design of artificially intelligent surfaces (molecular recognition and manufacturing systems) that allow the immobilization of active biomolecules. Plasma chemistry methods modify the top layers using gases such as ammonia while conventional wet chemistry modifies a region near the surfaces using strong acids, which usually causes soaking and swelling. Both methods suffer from the fact that they occur as a separate step, after the carbon nanoparticle synthesis. This extra step increases the difficulty of treatment, causes low efficiency, and creates uncertainty in the surface functionalization. It would be desirable to combine the synthesis of nanoparticles with their functionalization.39 (18) Holmes, S.; Schwartz, P. Compos. Sci. Technol. 1990, 38(1), 1–21. (19) Gengenbach, T. R.; Xie, X.; Chatelier, R. C.; Griesser, H. J. In Plasma Surface Modification of Polymers: Relevance to Adhesion; Strobel, M., Luons, C. S., Mittal, K. L., Eds.; VSP: Utrecht, The Netherlands, 1994; p 123. (20) Girardeaux, C.; Zammatteo, N.; M. Art, B. G.; Pireaux, J. J.; Caudano, R. Plasmas Polym. 1996, 1(4), 327–346. (21) Ganapathy, R.; Wang, X.; Denes, F.; Sarmadi, M. J. Photopolym. Sci. Technol. 1996, 9(2), 181–200. (22) Hollahan, J. R.; Wydeven, T. Science 1973, 179(4072), 500–501. (23) Peric, D.; Bell, A. T.; Shen, M. J. Appl. Polym. Sci. 1977, 21(10), 2661–2673. (24) Yasuda, H.; Bumgarner, M. O.; Marsh, H. C.; Morosoff, N. J. Polym. Sci., Part A: Polym. Chem. 1976, 14(1), 195–224. (25) Gombotz, W. R.; Guanghui, W.; Hoffman, A. S. J. Appl. Polym. Sci. 1989, 37(1), 91–107. (26) Sakata, J.; Wada, M. J. Appl. Polym. Sci. 1988, 35(4), 875–884. (27) Sarmadi, M.; Denes, F. Tappi J. 1996, 79(8), 189–204. (28) Chinn, J. A.; Ratner, B. D.; Horbett, T. A. Biomaterials 1992, 13(5), 322–332. (29) Terlingen, J. G. A.; Brenneisen, L. M.; Super, H. T. J.; Pijpers, A. P.; Hoffman, A. S.; Feijen, J. J. Biomater. Sci., Polym. Ed. 1993, 4(3), 165–181. (30) Jansen, R. J. J.; Vanbekkum, H. Carbon 1995, 33(8), 1021–1027. (31) Jansen, R. J. J.; Vanbekkum, H. Carbon 1994, 32(8), 1507–1516. (32) Pittman, C. U.; He, G. R.; Wu, B.; Gardner, S. D. Carbon 1997, 35(3), 317–331. (33) Pittman, C. U.; Wu, Z.; Jiang, W.; He, G. R.; Wu, B.; Li, W.; Gardner, S. D. Carbon 1997, 35(7), 929–943. (34) Jarrais, B.; Silva, A. R.; Freire, C. Eur. J. Inorg. Chem. 2005, 22, 4582–4589. (35) Alves, J. A. C.; Freire, C.; de Castro, B.; Figueiredo, J. L. Colloids Surf., A 2001, 189(1-3), 75–84. (36) Tamai, H.; Shiraki, K.; Shiono, T.; Yasuda, H. J. Colloid Interface Sci. 2006, 295(1), 299–302. (37) Longhi, M.; Bertacche, V.; Bianchi, C. L.; Formaro, L. Chem. Mater. 2006, 18(17), 4130–4136. (38) Hens, S. C.; Cunningham, G.; Tyler, T.; Moseenkov, S.; Kuznetsov, V.; Shenderova, O. Diamond Relat. Mater. 2008, 17(11), 1858–1866. (39) Denes, F. S.; Manolache, S.; Ma, Y. C.; Shamamian, V.; Ravel, B.; Prokes, S. J. Appl. Phys. 2003, 94(5), 3498–3508.
Published on Web 12/28/2009
DOI: 10.1021/la9022163
1991
Article
Jiang et al.
We report here a novel approach to such “one-step” combined synthesis and functionalization, using a new generation of all-in-one small submerged-arc plasma reactor with low power input that we have developed. We merge the functionalization into the synthesis process by taking advantage of free radicals generated by a submerged-arc helium atmosphere plasma to supply ethylenediamine directly after the plasma to functionalize the carbon nanoparticles. We investigate the surface characteristics of the carbon nanoparticles synthesized by this submerged-arc plasma and prove the viability of this new amination process. In addition, we show that the dispersibility of the carbon nanoparticles in aqueous solution is dramatically improved compared to the carbon nanoparticles solely synthesized from benzene. We demonstrate uniform and smaller nanoparticle sizes (1 μm) particles. The smaller nanoparticles not only have more surface area per volume for functionalization but also migrate more efficiently through the endothelial monolayer, which is essential to magnetic resonance imaging (MRI),44 and the lymphatic system, which DCs utilize as their preferential route to the lymph nodes.45 Thus, it has been proposed that targeting DCs with magnetic carbon nanoparticles could be a new route for the development of efficient vaccines. Moreover, the functionalized carbon nanoparticles we have made in this manner induce no inflammation or toxicity following intravenous injection, and nearly all extracellular nanoparticles are cleared after 1 week.13 Fluorescence microscope images clearly show that the functionalized nanoparticles have been modified to incorporate primaryamine functionalities because fluorescamine is specific for identi(43) Fifis, T.; Gamvrellis, A.; Crimeen-Irwin, B.; Pietersz, G. A.; Li, J.; Mottram, P. L.; McKenzie, I. F. C.; Plebanski, M. J. Immunol. 2004, 173(5), 3148–3154. (44) Weissleder, R.; Elizondo, G.; Wittenberg, J.; Rabito, C. A.; Bengele, H. H.; Josephson, L. Radiology 1990, 175(2), 489–493. (45) Reddy, S. T.; van der Vlies, A. J.; Simeoni, E.; Angeli, V.; Randolph, G. J.; O’Neill, C. P.; Lee, L. K.; Swartz, M. A.; Hubbell, J. A. Nat. Biotechnol. 2007, 25 (10), 1159–1164.
1994 DOI: 10.1021/la9022163
Figure 8. Results of thermogravimetry/differential thermogravimetry (TG/DTG) analysis of functionalized carbon nanoparticles. The two-step weight loss indicates a less (primary amine) and a more (amide) stable structural component.
fication of primary amines. As shown in Figure 7, the strong fluorescence of the ethylenediamine graft nanoparticles can be contrasted with the complete absence of fluorescence in the case of the virgin nanoparticles, which were not exposed to ethylenediamine. However, surface morphology and the thickness of the fluorescent layer on carbon-based nanoparticle surfaces strongly influence the intensity of the fluorescence by quenching.46 Very thin fluorescent layers produce an even stronger effect, which makes quantitative fluorescence evaluations difficult. The fluorescence images therefore have only a qualitative character. However, fluorescence images combined with the XPS results, which indicate relatively high surface nitrogen content, allow us to conclude that the grafting of primary-amine groups was successful. Even though many N functional groups show the same XPS N peak, the free-radical and ethylenediamine reaction limits the formation of all chemical bonds except amide (C-NH-). More chemical-bond evidence is shown in FTIR data described below. TG/DTG diagrams indicate that the functionalized nanoparticles loose relatively low-weight volatile compounds in two separate steps, namely at 37 C (2.5%) and at 130 C (2.9%) (Figure 8). Overall, the nanoparticles are thermally quite stable, exhibiting a weight loss of only 11% at 600 C and a relatively slow weight loss at a constant rate of 0.14%/min in the limits of (46) Roer, T.; Kitzerow, H. S.; Hummelen, J. C. Synth. Met. 2004, 141(3), 271–275.
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environments47-51 and be long-lived if they occur in a conjugated π system, such as the radical derived from R-tocopherol (vitamin E), fullerenes, etc.52-57 Our results support these findings. Submerged-arc helium plasma generated free radicals are also relatively stable and are long-lived under our experimental condition. Radicals add rapidly to the double bond, and the resulting Rradical carbonyl, for instance, is relatively stable; it can couple with another molecule or be oxidized. Nonetheless, the electrophilic/neutrophilic character of radicals has been shown in a variety of instances, and the radicals will attack the closest reactive sites the most readily.10,29,58-62 In our case, free radicals located on the particle surfaces allow the covalent attachment even of stable organic molecules such as ethylenediamine.10 The method described here thus provides an efficient way for the synthesis and functionalization of carbon-based nanoparticles and avoids at the same time the shortcomings and extra steps of conventional chemistry and plasma-functionalization processes.
Conclusions Figure 9. Fourier transform infrared (FTIR) spectrum of functionalized carbon nanoparticles.
150-350 C. Samples heated under identical TG/DTG conditions to 138 and 399 C and then analyzed using HR XPS evaluations exhibit the following relative surface atomic compositions: C: 80.8%; O: 15.5%; N: 3.7% and C: 85.0%; O: 13.0%; N: 1.9%, respectively. These data allow us to suggest that two different types of C-N bonds are incorporated into the structure of the nanoparticles: those that produce a less and a more stable structural component. Such a conclusion is in good agreement with the XPS data, which indicate the presence of both amine and amide groups. FTIR spectroscopy results from the functionalized nanoparticles are presented in Figure 9. The important characteristic vibrations of primary and secondary amines are present in the spectrum: A strong absorption in the wavenumber range of 3000 and 3450 cm-1 is assigned to a N-H stretch mode of primary and secondary amines. N-H bending of primary amines 1643 cm-1, C-N stretching at 1253 and 1092 cm-1, and N-H wagging modes of primary and secondary amines at 805 cm-1 can also be identified. The 2923 and 2960 cm-1 peaks are assigned to sp2 CH2 vibrations originating from ethylenediamine. The potential presence of sp (CH) vibrations is difficult to evaluate because above 3000 cm-1 the NH groups have very strong absorption. The origin of the relatively strong 2357 cm-1 peak is CO2 contamination. It is well-known that organic radicals can be generated even under conditions when a substrate is exposed to inert-gas plasma (47) Kuzuya, M.; Niwa, J.; Ito, H. Macromolecules 1993, 26(8), 1990–1995. (48) Kuzuya, M.; Kondo, S.; Sugito, M. Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1997, 38, 1049–1050. (49) Kuzuya, M.; Sugito, M.; Kondo, S. J. Photopolym. Sci. Technol. 1997, 10(1), 135–138. (50) Kuzuya, M.; Kondo, S.; Sugito, M.; Yamashiro, T. Macromolecules 1998, 31(10), 3230–3234.
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In this contribution, we describe a new approach that allows synthesis of carbon nanoparticles and the grafting of primaryamine functionalities onto the surface of these nanoparticles in a single process. The process uses a submerged-arc, atmospheric-pressure plasma reaction and takes advantage of the high reactivity and interaction of the plasma-generated free-radical sites with stable primary-amine precursor molecules in an in situ environment. Our findings demonstrate that the dispersibility of carbon nanoparticles has been improved enormously (see Figures 4 and 5), relative to the carbon nanoparticles without ethylenediamine functionalization, and is even better than that in our previous work.39 This new approach avoids the post-treatments either by conventional chemistry or by cold plasma surface modification and thus the incorporation of undesired, plasma mediated fragmentation reactions of primary-amine precursor molecules. This fortuitous situation provides an effective route to the surface modification of carbon nanoparticles. One can anticipate that other functionalities can be introduced in a similar manner. Acknowledgment. This research was supported in part by NSF and by DOE. (51) Kuzuya, M.; Yamashiro, T.; Kondo, S.; Sugito, M.; Mouri, M. Macromolecules 1998, 31(10), 3225–3229. (52) Oakley, R. T. Prog. Inorg. Chem. 1988, 36, 299–391. (53) Waters, W. A. Trans. Faraday Soc. 1941, 37, 770–780. (54) Rawson, J. M.; Banister, A. J.; Lavender, I. Adv. Heterocycl. Chem. 1995, 62, 137-247. (55) Griller, D.; Ingold, K. U. Acc. Chem. Res. 1976, 9(1), 13–19. (56) Baldock, R. W.; Hudson, P.; Katritzk, Ar; Soti, F. J. Chem. Soc., Perkin Trans. 1 1974, 12, 1422–1427. (57) Lomnicki, S.; Truong, H.; Vejerano, E.; Dellinger, B. Environ. Sci. Technol. 2008, 42(13), 4982–4988. (58) Hon, D. N. S.; Feist, W. C. Wood Fiber Sci. 1993, 25(2), 136–141. (59) Carley, J. F.; Kitze, P. T. Polym. Eng. Sci. 1980, 20(5), 330–338. (60) Hon, N. S. J. Appl. Polym. Sci. 1975, 19(10), 2789–2797. (61) Mitchell, J.; Perkins, L. R. Appl. Polym. Symp. 1967, 4, 167. (62) Martinez-Gomez, A. D.; Manolache, S. O.; Gonzalez-Alvarez, V.; Young, R. A.; Denes, F. S. Cellulose 2009, 16(3), 501–517.
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