Research

Self-Assembled Electronically Active Systems

Society is facing a technological revolution in information processing led by artificial intelligence. Conventional computers based on von Neumann architectures are not well-adapted for processing large scale information in parallel, which is essential for artificial intelligence applications. On the other hand, the neuronal network architecture in the brain is a remarkably efficient platform for information processing. However, it has proven to be extremely difficult to build such architectures using silicon-based electronics due to the limitations of 2D lithographic fabrication methods. To this end, crafting integrated circuits via self-assembly of functional nanomaterials using a “bottom-up” paradigm provides a promising solution to these technological challenges. I am particularly interested in control ovel the charge transport in self-assembled electronically active systems to enable advanced information processing and sensing.

Understanding charge transport at single molecule level

Charge transport in single molecule is the basis of any self-assembled electronically active systems. However, there is still a lack of fundamental understanding of the charge transport mechanism in molecules. The key challenge is to understand how the molecular structure and conformation determines intrachain charge transport. As a result, building even a simple molecular conductor that entails long range charge transport beyond several nanometers is still not feasible. In my recent work, I have explored the single molecule conductance of donor-acceptor typed oligomers and oxazole-terminated conjugated oligomers. In addition, the key factors that determine ultrahigh conductance of redox-active oligopeptides have been discovered, which will provide important insights for achieving the long-range charge transport in single molecules

1. B. Li, S. Li, A. Ellington, E. Anslyn and C.M. Schroeder, “Single Molecule Study of Charge Transport in Sequence-defined Redox Active Biomolecules”, (in prep)
2.S. Li, H. Yu, K. Schwieter, K. Chen, B. Li, Y. Liu, J. S. Moore and C.M. Schroeder, "Charge Transport and Quantum Interference Effects in Oxazole-Terminated Conjugated Oligomers”, Journal of the American Chemical Society, 141, 16079 (2019)
3. B. Li, H. Yu, E. C. Montoto, Y. Liu, S. Li, K. E. Schwieter, J. Rodriguez-Lopez, J. Moore and C. M. Schroeder, " Intrachain charge transport through conjugated donor-acceptor oligomers", ACS Applied Electronic Materials, 1,7, (2018)
4.X. Xin, B. Li, J. Jung, R. Biswas and Z. Lin, "Charge transfer at the semiconductor quantum dot/TiO2 interface in quantum dot-sensitized solar cells: ab initio simulation”, Particle and Particle Systems Characterization, 32, 80 (2015)

Controlled self-assembly under non-equilibrium conditions

Notably, nanomaterials, such as functional nanoparticles/nanowires, carbon nanotube, supramolecular materials, are typically synthesized with specific procedures in solution and need to be assembled into nanoelectronic circuits thereafter. The key to solution-based nanomaterial assembly lies in confining functional nanomaterials assembly under non-equilibrium conditions. I worked on self-assembly of nanomaterials under non-equilibrium condition (e.g., evaporation-induced self-assembly) using various nanomaterials, aiming to explore general rules for nanomaterials assembly and the dominate factors that governs the non-equilibrium kinetics

1.X. Li, B. Li, M. He, W. Wang, T. Wang, A. Wang, J. Yu, Z.L. Wang, S. W. Hong, M. Byun, S. Lin, H. Yu and Z. Lin, "A Convenient and Robust Route to Photoswitchable Hierarchical Liquid Crystal Polymer Stripes via Flow-Enabled Self-Assembly”, ACS Applied Materials & Interfaces, 10, 4961 (2018)
2.B. Li, C. Zhang, B. Jiang, W. Han and Z. Lin, "Flow-enabled self-assembly of large-scale aligned nanowires ", Angewandte Chemie International Edition, 54, 4250 (2015) (selected as Very Important Paper (VIP) paper by Angewandte Chemie International Edition).
3.B. Li, W. Han, B. Jiang and Z. Lin, "Crafting threads of diblock copolymer micelles via flow-enabled self-assembly",ACS Nano, 8, 2936 (2014)
4.W. Han, B. Li and Z. Lin, "Drying-mediated assembly of colloidal nanoparticles into large-scale microchannels",ACS Nano, 7, 6079 (2013)
5.W. Han, M. He, M. Byun, B. Li and Z. Lin, "Large-scale hierarchically structured conjugated polymer assemblies with enhanced electrical conductivity",Angewandte Chemie International Edition, 52, 2564 (2013)
6.M. Byun, W. Han, B. Li, X. Xin and Z. Lin, "An unconventional route to hierarchically ordered block copolymer on gradient patterned surface enabled by controlled evaporative self-assembly",Angewandte Chemie International Edition, 52, 1122(2013)
7.W. Han, M. Byun, B. Li, X. Pang and Z. Lin,"A simple route to hierarchically assembled micelles and inorganic nanoparticles",Angewandte Chemie International Edition, 51, 12588 (2012)
8.M. Byun, W. Han, B. Li, S. Hong, J. Cho, Q. Zou and Z. Lin, "Guided organization of λ-DNA into microring arrays from liquid capillary bridge", Small, 12, 1641 (2011)

Controlled self-assembly via non-covalent interactions

Self-assembly via non-covalent interactions is a powerful method that can be used to generate materials with well-defined structures across multiple length scales. Inspired by nature, a possible way to achieve complicated interconnected 3D network architecture at nanometer scale is via hierarchical assembly directed by non-covalent interactions. For example, supramolecular assemblies consisting of biopolymer polymer subunits are specifically known to exhibit exceptional structural and functional diversity as well as programmable control of noncovalent interactions through hydrogen bonding in biopolymer subunits. My goal is to understandthe relationship between the non-covalent interactions of molecules and the final assembled structure.

1. B. Li, S. Li, Y. Zhou, H.A.M. Ardoña, L. R. Valverde, W. L. Wilson, J. D. Tovar and C. M. Schroeder, "Nonequilibrium self-assembly of π-conjugated oligopeptide in solution", ACS Applied Materials & Interfaces, 9, 3977 (2017)
2. B. Li, L.R. Valverde, F. Zhang, Y. Zhou, S. Li, Y. Diao, W. L. Wilson and C. M. Schroeder, " Macroscopic alignment and assembly of π-conjugated oligopeptides using colloidal microchannels",ACS Applied Materials & Interfaces, 9, 41586 (2017)
3. L.R. Valverde, B. Li, C.M. Schroeder and W.L. Wilson, "In situ photophysical characterization of π-conjugated oligopeptides assembled via continuous flow processing”, Langmuir, 35, 10947 (2019)
4. C. Boucher-Jacobs, B. Li, C.M. Schroeder and D. Guironnet, " Solubility and activity of a phosphinosulfonate palladium catalyst in water with different surfactants”, Polymer Chemistry, 10, 1988 (2018)
5. Y. Zhou, B. Li, S. Li, H.A.M. Ardoña, W.L. Wilson, J.D. Tovar and C.M. Schroeder, "Concentration-Driven Assembly and Sol–Gel Transition of π-Conjugated Oligopeptides", ACS Central Science, 9, 986 (2017)
6. B. Jiang, C. Han, B. Li, Y. He and Z. Lin, "In-situ Crafting of ZnFe2O4 Nanoparticles Impregnated within Continuous Carbon Network as Advanced Anode Materials ", ACS Nano, 10, 2728 (2016)
7. B. Li, W. Han, M. Byun, L. Zhu, Q. Zou and Z. Lin, "Macroscopic highly aligned DNA nanowires created by controlled evaporative self-assembly", ACS Nano, 7, 4326 (2013)

Lithography-free microstructure fabrication

To face formidable challenges of future devices with complex functionality and architecture, not only new materials but also new fabrication method need to be developed. In addition, geometrical confinement using microstructure is an important strategy for constructing hierarchically structured nanocomposites assembly, entailing novel optical, electrical, and magnetic properties for various of potential applications. However, microstructures are oftern fabricated by complicated lithographic method, which are usually expensive and time-consuming, and not suitable for large scale manufacture. Therefore, a low-cost, large-scale method needs to be developed. To this end, I have developed a new strategy for massive parallel fabrication of microstructures by leveraging the film-cracking technique..

1. B. Li, B. Jiang, W. Han, M. He, X. Li, W. Wang, S.W. Hong, M. Byun, S. Lin and Z. Lin, " Harnessing Colloidal Crack Formation by Flow‐Enabled Self‐Assembly",Angewandte Chemie International Edition, 56, 4554 (2017) (selected as Very Important Paper (VIP) paper and featured on the Cover of by Angewandte Chemie International Edition)
2. M. He, B. Li, X. Cui, B. Jiang, Y. He, Y. Chen, D. O’Neil, P. Szymanski, M. A. El-sayed, J. Huang and Z. Lin, "Meniscus-assisted solution printing of large-grained perovskite films for high-efficiency solar cells", Nature Communications, 8, 16045 (2017)
3. L. Li, B. Li, C. Zhang, C. Tuan, Z. Lin and C. P. Wong, " A facile and low-cost route to high-aspect-ratio microstructures on silicon via a judicious combination of flow-enabled self-assembly and metal-assisted chemical etching",Journal of Materials Chemistry C, 4, 8953 (2016)
4. L. Li, B. Li, Z. Lin and C. P. Wong, " A low-cost fabrication route for silicon microchannels and microgratings with flow-enabled polymer self-assembly patterning and wet etching",Electronic Components and Technology Conference (ECTC), 2015 IEEE 65th, 2149 (2016)

Organic-inorganic nanomaterials systhesis

Colloidal nanocrystals exhibit a wide range of size- and shapedependent properties and have found application in myriad fields, incuding optics, electronics, mechanics, drug delivery and catalysis. Synthetic protocols that enable the simple and convenient production of colloidal nanocrystals with controlled size, shape and composition are therefore of key general importance. However, procedures such as organic solution-phase synthesis, thermolysis of organometallic precursors, sol–gel processes and hydrothermal reactions require stringent experimental conditions, are difficult to generalize, or necessitate tedious multistep reactions and purification. In such context, I am interested in organic-inorganic nanomaterial synthesis using organic templates, including DNA, self-assembled block-copolymer micelles, unimolecular star-like block-copolymers. These nanomaterials also serve as buildibing blocks for “bottom-up” self-assembly as mentioned above.

1.B. Li, B. Jiang, H. Tang and Z. Lin, "Unconventional seed-mediated growth of ultrathin Au nanowires in aqueous solution",Chemical Science, 6, 6349 (2015)
2. B. Jiang, Y. He, B. Li, S. Zhao, S. Wang, Y. B. He and Z. Lin, "Polymer‐Templated Formation of Polydopamine‐Coated SnO2 Nanocrystals: Anodes for Cyclable Lithium‐Ion Batteries", Angewandte Chemie International Edition, 56, 1869 (2017)
3. H. Tang, Y. He, B. Li, J. Jung, C. Zhang, X. Liu, and Z. Lin, " Continuous crafting of uniform colloidal nanocrystals using an inert-gas-driven microflow reactor",Nanoscale, 7, 9731 (2015)
4. B. Jiang, X. Pang, B. Li and Z. Lin, "Organic-Inorganic Nanocomposites via Placing Monodisperse Ferroelectric Nanocrystals in Direct and Permanent Contact with Ferroelectric Polymer", Journal of the American Chemical Society, 137, 11760 (2015)
5. C. Feng, X. Pang, Y. He, B. Li and Z. Lin, "Crafting unimolecular nanocapsules from photo-crosslinkable core-shell star-like block copolymer”, Chemistry of Materials. 26, 6058 (2014)