Langmuir 2008, 24, 5667-5671
5667
Sequential Solid-Phase Fabrication of Bifunctional Anchors on Gold Nanoparticles for Controllable and Scalable Nanoscale Structure Assembly Jeong-Hwan Kim and Jin-Woo Kim* Department of Biological and Agricultural Engineering, UniVersity of Arkansas, FayetteVille, Arkansas 72701 ReceiVed February 15, 2008. ReVised Manuscript ReceiVed April 24, 2008 This letter reports a serial solid-phase placement approach to synthesize anisotropically or symmetrically functionalized gold nanoparticles (AuNPs), in which the functionality and directionality (i.e., numbers, locations, and orientations) of the functional ligands are controlled. The solid-phase ligand exchange methodology using highly rigid filter papers enabled us to produce two types of bifunctionalized (bif-) AuNPs in a site-specific manner with increased yield and accuracy: (1) homobif-AuNPs with two carboxyl groups at ∼180° (para configuration) and (2) heterobif-AuNPs with one carboxyl and one amine functional groups at less than 180° but greater than 90° (meta configuration). Their chemical functionality was validated by 1H nuclear magnetic resonance as well as cyclic voltammetry after ferrocene ethylamine coupling reactions. The directional assemblies of 1D chains with homobif-AuNPs and 2D rings with heterobif-AuNPs were demonstrated through diamine and imidization coupling reactions, respectively, further validating their highly functional and directional selectivity, which is critical to realizing the practical nanoscale assembly.
Ligand molecules, such as n-alkanethiols, DNA, RNA, peptides, and antibodies, are fundamental interfacing components on nanoparticles (NPs) for solution-based NP assembly processes.1 A combination of their molecular recognition properties and self-assembling nature provides structural diversity and makes NPs ideal building blocks for controlled molecular interactions on the nanometer scale.1 To date, DNA-directed self-assembly approaches are promising in maneuvering both the complexity and hierarchy of nanostructures.2 DNA-directed self-assembly has been successfully used to construct regular, periodic structures2d-2f or simple circuits.2c In addition, protein-directed NP assembly has also been suggested, using the lock-and-key interactions between antibody and antigen1b or the peptide folding of chaperonins.1d However, the “panoscopic” organization of biological constituents still has grand challenges for the realization of functionally complex structures. Furthermore, practical nanofabrication would require the precise design and synthesis of nanostructures of arbitrary complexity with precise control over component placement. Well-defined and controlled functionality and directionality of the NP building blocks are essential to the active control of the molecular assembly processes on the nanometer scale as well as to the integration of heterogeneous * Corresponding author. E-mail:
[email protected]. Tel: +1-479-5752351. Fax: +1-479-575-2846. (1) (a) Mann, S.; Shenton, W.; Li, M.; Connolly, S.; Fitzmaurice, D. AdV. Mater. 1999, 12, 147–150. (b) Shenton, W.; Davis, S. A.; Mann, S. AdV. Mater. 1999, 11, 449–452. (c) Dujardin, E.; Mann, S. AdV. Mater. 2002, 14, 775–788. (d) McMillan, R. A.; Paavola, C. D.; Howard, J.; Chan, S. L.; Zaluzec, N. J.; Trent, J. D. Nat. Mater. 2002, 1, 247–252. (e) Huie, J. C. Smart Mater. Struct. 2003, 12, 264. (f) Daniel, M.-C; Astruc, D. Chem. ReV. 2004, 104, 293. (g) Love, J. C.; Estroff, L. A.; Kriebel, J. K.; Nuzzo, R. G.; Whitesides, G. M. Chem. ReV. 2005, 105, 1103. (2) (a) Mirkin, C. A.; Letsinger, R. L.; Mucic, R. C.; Storhoff, J. J. Nature 1996, 382, 607. (b) Loweth, C. J.; Caldwell, W. B.; Peng, X. G.; Alivisatos, A. P.; Schultz, P. G. Angew. Chem., Int. Ed. 1999, 38, 1808. (c) Mao, C.; LaBean, T. H.; Reif, J. H.; Seeman, N. C. Nature 2000, 407, 493–496. (d) Park, S. J.; Lazarides, A. A.; Mirkin, C. A.; Letsinger, R. L. Angew. Chem., Int. Ed. 2001, 40, 2909– 2912. (e) Yan, H.; LaBean, T. H.; Feng, L.; Reif, J. H. Proc. Natl. Acad. Sci. U.S.A. 2003, 100, 8103–8108. (f) Gothelf, K. V.; LaBean, T. H. Org. Biomol. Chem 2005, 3, 4023–4037. (g) Deng, Z.; Tian, Y.; Lee, S.-H.; Ribbe, A. E.; Mao, C. Angew. Chem., Int. Ed. 2005, 44, 3582. (h) Niemeyer, C. M.; Simon, U. Eur. J. Inorg. Chem. 2005, 18, 3641. (i) Huo, F.; Lytton-Jean, K R.; Mirkin, C. A. AdV. Mater. 2006, 18, 2304–2306.
nanocomponents into complex structures. Such control over the functionality and directionality would enable us to construct sophisticated nanostructures to take advantage of the increasing number of available nanocomponents, to construct complex nanoscale structures, and ultimately to approximate the complexity and functionality of current microfabrication techniques.3 Anisotropic chemical modifcation strategies would permit the precise positioning and interconnection of the NP nanobuilding blocks, enabling us to control the spatial placement of individual functional components and to minimize defects on the molecular level. Recently, several attempts have been made to control the valency of NPs by controlling their chemical functionality.4 Huo and co-workers4a,4b and Jacobson and co-workers4c have successfully demonstrated monoalkanethiol-terminated gold nanoparticles (AuNPs) using a solid-phase ligand-exchange method as a superior strategy to use in controlling the chemical lithography of NPs. With this asymmetrically functionalized NP, they could assemble 1D dimers with greater accuracy. In addition, the anisotropic self-assembly of 1D AuNP chains was demonstrated using asymmetrically functionalized AuNPs and a polymer as a template for the assembly.4f However, the functionality and directionality of the building blocks should be further increased for the practical nanoscale assembly, which requires the reliable synthesis of 2D and 3D supernanostructures with heterogeneous nanocomponents. Here, we report a versatile and efficient anisotropic NP functionalization strategy to increase control over the locations, orientations, and compositions of the functional ligand groups. (3) (a) Braun, E.; Sivan, U. In Nanobiotechnology: Concepts, Applications and PerspectiVes; Niemeyer, C. M., Mirkin, C. A., Eds.; Wiley-VCH Verlag GmbH & Co.: Weinheim, Germany, 2004; p 244. (b) Thaxton, C. S.; Mirkin, C. A. In Nanobiotechnology: Concepts, Applications and PerspectiVes; Niemeyer, C. M., Mirkin, C. A., Eds.; Wiley-VCH Verlag GmbH & Co.: Weinheim, Germany, 2004; p 288. (4) (a) Shaffer, A. W.; Worden, J. G.; Huo, Q. Langmuir 2004, 20, 8343. (b) Worden, J. G.; Dai, Q.; Shaffer, A. W.; Huo, Q. Chem. Mater. 2004, 16, 3746– 3755. (c) Sung, K.-M.; Mosley, D. W.; Peelle, B. R.; Zhang, S.; Jacobson, J. M. J. Am. Chem. Soc. 2004, 126, 5064. (d) Xu, X.; Rosi, N. L.; Wang, Y.; Huo, F.; Mirkin, C. A. J. Am. Chem. Soc. 2006, 128, 9286–9287. (e) Sardar, R.; Heap, T. B.; Shumaker-Parry, J. S. J. Am. Chem. Soc. 2007, 129, 5356. (f) Sardar, R.; Shumaker-Parry, J. S. Nano Lett. 2008, 8, 731–736.
10.1021/la800506g CCC: $40.75 2008 American Chemical Society Published on Web 05/09/2008
5668 Langmuir, Vol. 24, No. 11, 2008 Scheme 1. Synthesis of MUA-Monofunctionalized, MUA-Homobifunctionalized, and MUA/ EDA-MUA-Heterobifunctionalized Gold Nanoparticlesa
a Reagents and conditions: (a) DCM, 40 °C, 6 h, room temperature, 12 h. (b) 2 M NH3Cl2. (c) DCM, 40 °C, 6 h, room temperature, 12 h. (d) 2 M NH3Cl2. (e) 83 mM EDA/10 µM DICDI, 10% MeOH/DCM, room temperature, 12 h. (f) 2 M NH3Cl2.
The synthesis of bifunctionalized (bif-) AuNPs in a site-specific manner, which contain two same (homo-) and different (hetero-) functional groups at defined angles (i.e., 180 and
