Self-assembly and Nanomaterials  

Nanostructured materials represent a fascinating class of materials whose structural elements such as atomic clusters, crystallites or molecules have dimensions in the range of 1 to 100 nm, the length scale that defines physical properties of materials and at which intriguing phenomena are observed due to quantum phenomena. They exhibit unique electrical, optical, magnetic and sensing properties that are readily tunable through controlling their size, and enable novel applications that are impossible to realize with their bulk counterparts. Synthesis and processing of nanostructured materials have come a long way. Methods have now been established to obtain monodisperse nanocrystals of various metallic and semiconducting materials, fullerenes of distinct properties, single- and multi-wall carbon nanotubes. Novel organic nanomaterials such as supramolecular nanostructures, polymeric dendrimers with tailored functionalities, as well as other nanophase constructs, are being actively developed. One key step towards novel applications of nanostructured materials concerns their surface functionalization, assembly, patterning, orientation and alignment into functional networks without mutual aggregation. Among the bottom-up strategies, self-assembly provides a promising route to build up complex systems with immense flexibility in terms of nanoscale building blocks and resulting functionalities and properties. As the name suggests, self-assembly is a process in which organization of colloidal, macromolecular, or supramolecular units into the desired system occurs through nature-intended phenomena, either mediated by physicochemical pathways or assisted by biomolecules to promote molecular selectivity and specificity. Current research is focused mainly on the combination of molecular/biomacmolecular self-assembly and nanostructured materials for electronic, photonic and biological applications.

1. Surface and Interface Engineering via Molecular Self-Assembly

• Molecular self-assembly on metal (Au, Ag) and semiconductor (Si, GaAs) surfaces: self-assembly of pi-conjugated molecules to understand diversified molecule-molecule and molecule-substrate interactions and to have novel nanoelectronic and optical behaviors
• Interfacial engineering of metal oxide substrates (ITO, SiO 2/Si, Al 2O 3, TiO 2): self-assembly of functional (dipolar or hole-transporting) phosphonic acids to enhance charge injection/separation, reduce charge traps and increase charge mobility of organic semiconductors by monolayer-mediated ordering for optoelectronics (LED, FET, PV)
• Surface functionalization of nanomaterials (NP, QD, nanowire): molecular self-assembly on nanosurface to tune the properties of nanostructures, such as charge injection/separation for optoelectronics, and water-solubility, biocompatibility, stability, toxicity, circulating, biodegradability and multifunctionality (targeting, probing and drug delivery) for bioimaging/nanomedicine

2. SAM-Bio-Nanomaterial Hybrids

• Patterned assembly of nanomaterials via genetically engineered proteins for inorganics (GEPI) and self-assembled monolayer (SAM): surface chemistry to build patterned, multi-component and 2D/3D hybrid structures of SAMs, biomacromolecules and nanomaterials
• Bio-nanophotonics (plasmonics) and biosensing: surface plasmon-modulated fluorescence, and metal-molecule-metal charge transfer and/or surface-enhanced Raman scattering (SERS) through spatially-organized nanostructures

3. Supramolecular Nanostructures of pi-Conjugated Materials

• Formation of supramolecular nanostructures: design, synthesis and processing of pi-conjugated molecules with non-covalent intermolecular interactions such as hydrogen bonding, pi-pi stacking, metal-ion coordination, electrostatic, dipolar, and quadrupolar interactions. Combination of easy-to-process and single-crystal-like properties
• Supramolecular electronics/photonics: crosslinking, assembly, patterning and alignment of supramolecular nanostructuresto tailor a large number of unprecedented properties such as charge transport, energy/charge transfer and light harvesting

1. “pi-sigma-Phosphonic Acid Organic Monolayers/Sol-Gel Hafnium Oxide Hybrid Dielectrics for Low-Voltage Organic Transistors”, O. Acton, G. Ting, H. Ma, J. W. Ka, H. L. Yip, N. M. Tucker, A. K.-Y. Jen, Adv. Mater. 2008, in press.
2. “Low-Voltage Organic Thin-film Transistors with pi-sigma-Phosphonic Acid Molecular Dielectric Monolayers”, H. Ma, O. Acton, G. Ting, J. W. Ka, H. L. Yip, N. M. Tucker, R. Schofield, A. K.-Y. Jen, Appl. Phys. Lett. 2008, 92, 113303.
3. “Controlled Assembly of Large p-Conjugated Aromatic Thiols on Au(111)”, Q. M. Xu, H. Ma, H. L. Yip, A. K.-Y. Jen, Nanotech. 2008, 19, 135605.
4. “Deprotecting Thioacetyl-Terminated Terphenyldithiol for Assembly on Gallium Arsenide”, D. A. Krapchetov, H. Ma, A. K.-Y. Jen, D. A. Fischer, Y. L. Loo, Langmuir 2008, 24, 851.
5. “Plasmon Resonant Structures with Unique Topographic Characteristics and Tunable Optical Properties for Surface-Enhanced Raman Scattering”, Zin, M. T., Leong, K., Wong, N. Y., Ma, H., Jen, A. K.-Y., Nanotech. 2007, 18, 455301.
6. “An atomic force microcopy study of the mechanical and electrical properties of monolayer films of molecules with aromatic end groups”, L. Fang, J. Y. Park, H. Ma, A. K.-Y. Jen, M. Salmeron, Langmuir 2007, 23, 11522.
7. “Controlled Assembly of Large p–Conjugated n-Type Molecules on Au(111)”, Q. M. Xu, H. Ma, N. M. Tucker, J. A. Bardecker, A. K.-Y. Jen, Nanotech. 2007, 18, 335302.
8. “Direct Surface Functionalization of Indium Tin Oxide via Electrochemically-induced Assembly”, M. S. Kang, H. Ma, H. L. Yip, A. K.-Y. Jen, J. Mater. Chem. 2007, 17, 3489-3492.
9. “Peptide-Mediated Formation of Well-Controlled Quantum Dot Arrays with Tunable Photoluminescence Properties”, M. T. Zin, A. M. Munro, M. Gungormus, H. Ma, C. Tamerler, D. S. Ginger, M. Sarikaya, A. K.-Y. Jen, J. Mater. Chem. 2007, 17(9), 866.
10. “Direct Nanofabrication and Transmission Electron Microscopy on a Suite of Easy-to-Prepare Ultrathin Film Substrates”, D. Allred, M. T. Zin, H. Ma, M. Sarikaya, F. Baneyx, A. K-Y. Jen, D. T., Schwartz, Thin Solid Films, 2007, 515, 5341.
11. “Assembly of Nanomaterials through Highly Ordered Self-Assembled Monolayers and Peptide-Organic Hybrid Conjugates as Templates”, H. Ma, M. T. Zin, M. H. Zareie, M-S. Kang, S. H. Kang, K. S. Kim, B. W. Reed, C. Tamerler, M. Sarikaya, A. K-Y. Jen, J. Nanosci. Nanotech. 2007, 7(8), 2549-2566.
    
12. “Patterning of Robust Self-Assembled n-type H exaazatrinaphthylene-based Nanorods and Nanowires by Microcontact Printing”, H.-L. Yip, J. Zhou, H. Ma, Y. Tian, N. M. Tucker, and A. K.-Y. Jen, J. Am. Chem. Soc., 2006, 128, 13042.
13. “Time-resolved Photoluminescence Spectroscopy of Surface-Plasmon-Enhanced Light Emission from Conjugated Polymers”, T. D. Neal, K. Okamoto, A. Scherer, M. S. Liu, A. K-Y. Jen, C. F. Shu, Appl. Phys. Lett., (in press).
14. “Efficient Photocurrent Generation through a Self-assembled Monolayer of C 60-Phenylacetylene-anthrathene”, M. S. Kang, S. H. Kang, H. Ma, K. S. Kim, and A. K-Y. Jen, J. Power Sources, 2006, 160, 711.
15. “Two-Dimensional Self-Assembly of Pyrene Phosphonic Acid: Transfer of Stacks on Structured Surface” H. L. Yip, H. Ma, A. K-Y. Jen, J-C. Dong, B. A. Parviz, J. Am. Chem. Soc., 2006, 128(17), 5672.
16. “Gated Lateral Charge Transport in a Self-assembled Pyryl Phosphonic Acid Molecular Multi-layer with Defined 2.5 nm Step Heights”, J. Dong, H. L. Yip, H. Ma, A. K-Y. Jen, and B. A. Parviz, Appl. Phys. Lett., 2006, 88, 223112.
17. “Arrays of Covalently Bonded Nanoparticles on Organic Bilayer Assemblies”, M. T. Zin, H-L. Yip, N-Y. Wong, H. Ma, and A. K-Y. Jen, Langmuir, 2006, 22(14), 6346.
18. “New Environmental-Responsive Fluorescent NIPAA Copolymer and Its Application on DNA Sensing”, C. C. Yang, Y. Tian, A. K.-Y. Jen, and W. C. Chen, J. Polym. Sci. A: Polym. Chem., 2006, 44, 5495.
19. “Placement of Chemically Bonded Single Gold Nanoparticles on Laterally Structured Asymmetric Organic Bilayer Assemblies”, M. T. Zin, H. L. Yip, H. Ma, and A. K-Y. Jen, Langmuir, 2006, 22(14), 6346.
20. “Thiol-Linked Anthraquinone Anthryl Acetylene Molecule: Synthesis, Ordered Self-Assembly, and Photoelectrochemical Properties”, H. Ma, M. S. Kang, Q. M. Xu, K. S. Kim, and A. K.-Y. Jen, Chem. Mater., 2005, 17, 2896.
21. “ Self-Assembled Monolayer of Aromatic Thiols Stabilized by Parallel-Displaced p-p Stacking Interactions”, R. F. Dou, X-C. Ma, H. L. Yip, K-Y. Wong, W. M. Lau, W. S. Yang, J. F. Jia, Q. K. Xue, H. Ma, A. K-Y Jen, , and Langmuir, 2006, 22(7), 3049.
22. “The Assembly of Terphenyl- and Quaterphenyl-dithiol on Gold and Gallium Arsenide: Solvent Effects: Investigated by NEXAFS”, D. Krapchetov, H. Ma, A. K-Y. Jen, D. A. Fischer, and Y-L. Loo, Langmuir, 2005, 21, 5887.
23. “Assembly of Gold Nanoparticles Using Genetically Engineered Polypeptides”, M. Zin, H. Ma, M. Sarikaya, A. K-Y. Jen, Small, 2005, 1(7), 698.
24. “Ordered Self-Assembly and Electronic Behavior of C 60-Anthrylphenylacetylene Hybrid ” S. H. Kang, H. Ma, M. H. Zareie, M. Kang, K. Kim, M. Sarikaya, and A. K.-Y. Jen, Angew. Chem, Int. Ed., 2004, 43(12), 1512.
25. “Highly Efficient Current Generation from Self-Assembled Monolayer Film with new C 60-tethered 2, 5-dithienylpyrrole Triad”, K. S. Kim, M. S. Kang, H. Ma, and A. K-Y. Jen, Chem. Mater., 2004, 16(24), 5058.
26. “Functional Self-assemblies for Photocurrent Generation”, H. Ma and A. K-Y. Jen, an Invited Article to Spectrum, 2004, 17(3), 24.
27. “Controlled Assembly of Conducting Monomers for Molecular Electronics”, H. Zareie, H. Ma, B. Reed, A. K-Y. Jen, and M. Sarikaya, Nano Lett., 2003, 3(2), 139.
28. “Molecular Biomimetics: Nanotechnology through Biology”, M. Sarikaya, C. Tamerler, A. K-Y. Jen, K. Schulten, and F. Baneyx, An Invited Review in Nature Materials, 2003, 2, 577.