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Dr. Lei Zhai

Lei Zhai
Associate Professor of Nanoscience Technology Center and the Department of Chemistry
Ph.D., Carnegie Mellon University, 2002
Phone: 407-882-2847
Office: PVL 424
Zip: 32816-0150
E-mail: lzhai@ucf.edu
View Full Curriculum Vita
Research Videos from Dr. Lei Zhai's Laboratory

Research

Conductive Polymer/Carbon Nanotube Composites (Supported by NSF CAREER Award)
Carbon nanotubes (CNTs) have attracted enormous interest due to their remarkable mechanical, thermal, and electrical properties. The CNTs applications include nanoelectronics, sensors, energy storage devices, photovoltaics, and nanocomposite materials. One of the key challenges to fully realize their extensive applications is the dispersion and functionalization of carbon nanotubes. We have developed a simple and versatile approach to disperse CNTs within various solvents and polymer matrices using conjugated block copolymers with tunable functionalities. In contrast to invasive chemical functionalization of CNTs, this approach provides non-invasive method to disperse and functionalize CNTs. With a simple sonication, the conjugated polymer blocks, such as polythiophenes, can form strong π-π interactions with carbon nanotube walls, while the non-conjugated polymer blocks will provide the de-bundled CNTs with good solubility and stability in a wide range of organic solvents and host polymer matrices. The non-conjugated polymer blocks can also introduce a variety of functionalities to CNTs, allowing further functionalization such as depositing nanoparticles on CNT surfaces. Additionally, we have fabricated ordered poly(3-hexylthiophene)(P3HT) supramolecular structures on CNTs through a CNT enhanced crystallization process. Such bottom-up strategy provides a general approach to build functional conductive supramolecular structures that will lead to numerous applications in nanoscale electronics. Our current work aims at fabricating multifunctional CNT or graphene/conductive block copolymer composites and exploring their applications in energy conversion and storage devices.

2) Polymer Derived Ceramics (Supported by NSF FRG Award)
Ceramics have been extensive used and investigated due to their intriguing properties including high thermal and chemical stability, piezoresistivity, and optoelectrical properties. Unlike conventional ceramics obtained by sintering corresponding powders, the polymer-derived ceramics (PDCs) are synthesized by direct thermal decomposition of polymeric precursors. Such technology allows the control of ceramic composition through the functionalization of polymer precursors. Our research focuses on fabricating functional ceramics by incorporating various materials in polymers, and studying their electrical and mechanic properties. We have developed a unique simple technique to synthesize Si-C-N(O)-Al ceramic with high piezoresistivity from aluminum doped polysilazanes. Ceramic fibers were also fabricated via the electrospinning and PDCs techniques. Preceramic polymer (polysilazane) fibers were fabricated via electrospinning. The obtained polymer fibers were then pyrolyzed into Si-C-N(O)-Al ceramic fibers at 1000 oC in Ar. Based on our discovery of dispersing CNT using conductive block copolymers, we have successfully incorporated CNTs in polymer derived ceramics, which leads to improved electrical conductivity and mechanical properties. Si-C-N(O)-Al ceramics possess excellent thermal stability, low thermal conductivity, piezoresistivity, and resistance to oxidation/corrosion. We are studying their potential applications in high temperature catalyst supports, sensors and protecting materials.

3) Surface Functionalization of Microfluidic Systems
The development of micropumps and microvalves has made it possible to realize a fully integrated microfluidic system for biochemical analysis. Nano/microliter fluid handling on lab-on-a-chip (LOC) by passive fluidic manipulation often employs a hydrophobic surface as a valve in the microchannel network and an external pneumatic control coupled with capillary action to discretely manipulate the fluids. We have extended the surface functionalization via the layer-by-layer deposition of polyelectrolytes and nanoparticles to microfluidic systems, and have fabricated a fully integrated microfluidic valve with a switchable, thermosensitive polymer surface through the combination of the layer-by-layer self-assembly technique and microfabrication. We also developed an analytical model for the switching characteristic of a thermosensitive surface that is very useful for the characterization and design purpose. Current research is focusing on generating cell patterns in microfluidic systems for biomedical application.

Ultra-light Multi-walled Carbon Nanotube Aerogel
Ultra-light multi-walled carbon nanotube (MWCNT) aerogel with a density of 4 mg/cm3 was fabricated. The fabrication procedure relied on modifying MWCNTs with reactive polymer of poly (3-(trimethoxysilyl) propyl methacrylate) (PTMSPMA), whose hydrolysis and condensation introduces strong chemical bonding interaction between MWCNTs and dramatically decreases the critical gelation concentration of MWCNTs. The MWCNT aerogel has an anisotropic macroporous honeycomb structure with straight and parallel channels separated by thin MWCNT walls. The MWCNT aerogel demonstrates excellent compression recovery properties and its surface area and conductivity were characterized to be 580 m2/g and 0.67 S• cm-1, respectively. The excellent compression recovery property, high surface area, and high conductivity of the MWCNT aerogel lead to interesting pressure and chemical vapor responsive capability.

Bottom-up Assembly of Poly(3-hexylthiophene) on Carbon Nanotubes: 2D Building Blocks for Nanoscale Circuits
Hierarchical poly(3-hexylthiophene)(P3HT)/carbon nanotube (CNT) supramolecular structures were fabricated through a bottom-up CNT induced P3HT crystallization strategy. P3HT nanowires growing perpendicular from CNT surface have uniform width and height. The density and the length of these nanowires can be controlled by tuning the P3HT/CNT mass ratio. The quasi-isothermal crystallization process monitored by in-situ UV-Vis spectroscopy indicates that CNTs can greatly enhance the P3HT crystallization, and the P3HT nanowire formation follows first-order kinetics. Such bottom-up strategy provides a general approach to build 2D functional conductive supramolecular structures that will lead to numerous applications in nanoscale electronics.

Conductive block copolymer systems to disperse and stabilize CNTs
The conjugated polymer block such as polythiophenes can form strong π-π interactions with carbon nanotube walls, while the non-conjugated polymer block offers good solubility and stability in a wide range of organic solvents and host polymer matrices.

Controllable Drug Delivery Systems for Diabetic Patients
Research in my laboratory focuses on the development of drug delivery systems to address limitations in existing techniques.

Selected Publications

Chen, H.; Chunder, A.; Liu, X.; Haque, F.; Zou, J.; Austin, L.; Knowles, G.; Zhai, L.; Huo, Q. "A Multifunctional Gold Nanoparticle/Polyelectrolyte Fibrous Nanocomposite Prepared from Electrospinning Process" Mater. Express, 1, 154.

Shabani, R.; Massi, L.; Zhai, L.; Seal, S.; Cho, H. J. "Classroom Modules for Nanotechnology Undergraduate Education: Development, Implementation, and Evaluation" Eup. J. Eng. Edu. 2011, 36, 199.

Singh, V.; Joung, D.; Zhai, L.; Das, S.; Khondaker, S. I.; Seal, S. "Graphene Based Materials: Past, Present and Future" Prog. Mater. Sci. 2011, 56, 1178.

Sarkar, S.; Zhai, L. "Polymer-Derived Non-Oxide Ceramics Fibers- Past, Present and Future" Mater. Exp. 2011, 1, 18.

Zou, J.; Tran, B.; Zhai, L. "Fabrication of Metal Nanoparticles on Highly Dispersed Pristine Carbon Nanotubes" International Journal of Smart and Nano Materials, 2011, 2, 92.

Liu, J.; Mikhailov, I.; Zou, J.; Osaka, I.; Masunov, A. E.; McCullough, R. D.; Zhai, L. "Insight into How Molecular Structures of Thiophene-based Conjugated Polymers Affect Crystallization Behaviors" Polymer, 2011, 52, 2302.

Joung, D.; Zhai, L. Khondaker, S. K. "Coulomb Blockade and Hopping Conduction in Graphene Quantum Dots Array" Phys. Rev. B. 2011, 83, 115323.

Sarker, B. K.; Liu, J.; Zhai, L.; Khondaker, S. I. Fabrication of Organic Field Effect Transistor by Directly Grown Poly(3-hexylthiophene) Crystalline Nanowires on Carbon Nanotube Aligned Array Electrode" ACS Appl. Mater. Interfaces 2011, 3, 1180.

Li, Q.; Liu, J.; Zou, J.; Chunder, A.; Chen, Y.; Zhai, L. "Synthesis and Electrochemical Performance of Multi-walled Carbon Nanotube/Polyaniline/MnO2 Ternary Coaxial Nanostructures for Supercapacitors" J. Power Sources 2011, 196, 565.

Tafti1, E. Y.; Londe, G.; Chunder, A; Zhai, L.; Kumar, R.; Cho, H. J. "Wettability Control and Flow Regulation Using a Nanostructure-Embedded Surface" J. Nanosci. Nanotechnol. 2011, 11, 1417.

Zou, J.; Liu, J.; Karakoti, A.; Kumar, A.; Joung, D.; Li, Q.; Khondaker, I. S.; Seal, S.; Zhai, L. "Ultra-light Multi-walled Carbon Nanotube Aerogel" ACS Nano 2010,4, 7293.

Hu, Z.; Liu, J.; Gesquiere, A.; Zhai, L. "Single Molecule Spectroscopy and Atomic Force Microscopy Morphology Studies on a Diblock Copolymer Consisting of Poly (3-hexylthiophene) and Fullerene" Macromol. Chem. Phys. 2010, 211, 2416.

Joung, D.; Chunder, A.; Zhai, L.; Khondaker. S. I. "Space Charge Limited Conduction with Exponential Trap Distribution in Reduced Graphene Oxide Sheet" Appl. Phys. Lett.2010, 97, 093105.

Chunder, A.; Pal, T.; Khondaker, S. I.; Zhai, L. "Reduced Graphene Oxide/Copper Phthalocyanine Composite and Its Optoelectrical Properties" J. Phys. Chem. C. 2010, 114, 15129.

Arif, M.; Liu, J.; Zhai, L.; Khondaker, S. I. "Poly(3-hexylthiophene) Crystalline Nanoribbon Network for Organic Field Effect Transistors" Appl. Phys. Lett. 2010. 96, 243304.

Ghosh, S.; Sarker, B. K.; Chunder, A.; Zhai, L.; Khondaker, S. I. "Position Dependent Photodetector from Large Area Reduced Graphene Oxide Thin Films" Appl. Phys. Lett. 2010, 96, 162109.

Sarkar, S.; Zou, J.; Liu, J.; Xu, C.; An, L.; Zhai, L. "Polymer-Derived Ceramic Composite Fibers with Aligned Pristine Multiwalled Carbon Nanotubes" ACS Appl. Mater. Interfaces 2010, 2, 1150.

Joung, D.; Chunder, A.; Zhai, L.; Khondaker. S. I. "High Yield Fabrication of Chemically Reduced Graphene Oxide Field Effect Transistors by Dielectrophoresis" Nanotechnology, 2010, 16, 165202.

Sharma, R.; Karakoti, A.; Seal, S.; Zhai, L. "MWCNT-PSS Supported Polypyrrol/Manganese Oxide Nano-Composite for High Performance Electrochemical Electrodes" J. Power Sources 2010, 195, 1256.

Chunder, A.; Liu, J.; Zhai, L. "Reduced Graphene Oxide/Poly(3-hexylthiophene) Supramolecular Composites" Macromol. Rapid Commun. 2010, 31, 380.

Li, Q.; Liu, J.; Zou, J.; Chunder, A.; Chen, Y.; Zhai, L. "Synthesis and Electrochemical Performance of Multi-walled Carbon Nanotube/Polyaniline/MnO2 Ternary Coaxial Nanostructures for Supercapacitors" J. Power Sources 2011, 196, 565.

Tafti1, E. Y.; Londe, G.; Chunder, A; Zhai, L.; Kumar, R.; Cho, H. J. "Wettability Control and Flow Regulation Using a Nanostructure-Embedded Surface" J. Nanosci. Nanotechnol. 2011, 11, 1.

Hu, Z.; Liu, J.; Gesquiere, A.; Zhai, L. "Single Molecule Spectroscopy and Atomic Force Microscopy Morphology Studies on a Diblock Copolymer Consisting of Poly (3-hexylthiophene) and Fullerene" Macromol. Chem. Phys. 2010, 211, 2416.

Zou, J.; Liu, J.; Karakoti, A.; Kumar, A.; Joung, D.; Li, Q.; Khondaker, I. S.; Seal, S.; Zhai, L. "Ultra-light Multi-walled Carbon Nanotube Aerogel" ACS Nano 2010, 4, 7293.

Joung, D.; Chunder, A.; Zhai, L.; Khondaker. S. I. "Space Charge Limited Conduction with Exponential Trap Distribution in Reduced Graphene Oxide Sheet" Appl. Phys. Lett. 2010, 97, 093105.

Chunder, A.; Pal, T.; Khondaker, S. I.; Zhai, L. "Reduced Graphene Oxide/Copper Phthalocyanine Composite and Its Optoelectrical Properties" J. Phys. Chem. C. 2010, 114, 15129.

Arif, M.; Liu, J.; Zhai, L.; Khondaker, S. I. "Poly(3-hexylthiophene) Crystalline Nanoribbon Network for Organic Field Effect Transistors" Appl. Phys. Lett. 2010. 96, 243304.

Ghosh, S.; Sarker, B. K.; Chunder, A.; Zhai, L.; Khondaker, S. I. "Position Dependent Photodetector from Large Area Reduced Graphene Oxide Thin Films" Appl. Phys. Lett. 2010, 96, 162109.

Sarkar, S.; Zou, J.; Liu, J.; Xu, C.; An, L.; Zhai, L. "Polymer-Derived Ceramic Composite Fibers with Aligned Pristine Multiwalled Carbon Nanotubes" ACS Applied Materials & Interface 2010, 2, 1150.

Joung, D.; Chunder, A.; Zhai, L.; Khondaker. S. I. "High Yield Fabrication of Chemically Reduced Graphene Oxide Field Effect Transistors by Dielectrophoresis" Nanotechnology, 2010, 16, 165202.

Sharma, R.; Karakoti, A.; Seal, S.; Zhai, L. "MWCNT-PSS Supported Polypyrrol/Manganese Oxide Nano-Composite for High Performance Electrochemical Electrodes" J. Power Sources 2010, 195, 1256.

Chunder, A.; Liu, J.; Zhai, L. "Reduced Graphene Oxide/Poly(3-hexylthiophene) Supramolecular Composites" Macromol. Rapid Commun. 2010, 31, 380.

Liu, J.; Arif, M.; Zou, J.; Khondaker, S. I.; Zhai, L. "Controlling Poly(3-hexylthiophene) Crystal Dimension: Nanowhiskers and Nanoribbons" Macromolecules, 2009,42, 9390.

Zou, J.; Tran, B.; Huo, Q.; Zhai, L. "Transparent Carbon Nanotube/Poly (3, 4-ethylenedioxythiophene) Composite Electrical Conductors" Soft Materials 2009, 7, 355.

Sharma, R.; Zhai, L. "Multiwall Carbon Nanotube Supported Poly(3,4-ethylenedioxythiophene)/Manganese Oxide Nanocomposite Electrode for Supercapacitors" Electrochim. Acta 2009, 54, 7148.

Dai, Q.; Li, Y.; Zhai, L.; Sun, W. "3, 4-Ethylenedioxythiophene (EDOT)-Based -Conjugated Oligomers: Facile Synthesis and Excited-state Properties" J. Photochem. Photobio. A: Chem. 2009, 206,164.

Liu, J.; Zou, J.; Zhai, L. "Bottom-up Assembly of Poly(3-hexylthiophene) on Carbon Nanotubes: 2D Building Blocks for Nanoscale Circuits" (Cover Featured) Macromol. Rapid Commun. 2009, 30,1387.

Dhir, V.; Natarajan, A.; Stanceescu, M.; Chunder, A.; Bhargava, N.; Das, M.; Zhai, L.; Molnar, P. "Patterning of Diverse Mammalian Cell Types in Serum Free Medium with Photoablation" Biotechnol. Prog. 2009, 25, 594.

Londe, G.; Chunder, A.; Zhai, L.; Cho, H. J. "An Analytical Model for the Wettability Switching Characteristic of a Nanostructured Thermoresponsive Surface" Appl. Phys. Lett. 2009, 94, 164104.

Chunder, A.; Etcheverry, K.; Wadsworth, S.; Boreman, G. D.; Zhai, L. "Fabrication of Antireflection Coatings on Plastics Using the Spraying Layer-by-layer Self-assembly Technique" Journal of the Society for Information Display (invited), 2009, 17, 389.

Scolari, L.; Gauza, S.; Xianyu, H.; Zhai, L. ; Eskildsen, L.; Akleskhold, T. T.; Wu, S. -S.; Bjarklev, A. "Frequency Tunability of Solid-Core Photonic Crystal Fibers Filled with Nanoparticle-Doped Liquid Crystals" Opt. Exp. 2009, 17, 3754.

Stokes, P.; Liu, L.; Zou, J.; Zhai, L.; Huo, Q.; Khondaker, S. I. "Photoresponse in Large Area Multi-walled Carbon Nanotube/Polymer Nanocomposite Films" Appl. Phys. Lett. 2009, 94, 042110.

Zou, J.; Khondaker, S. I.; Huo, Q.; Zhai, L. "A General Strategy to Disperse and Functionalize Carbon Nanotubes Using Conjugated Block Copolymers" Adv. Funct. Mater. 2009, 19, 479.

Chunder, A.; Etcheverry, K.; Londe, G.; Cho, H. J.; Zhai, L. "Conformal Switchable Superhydrophobic/Hydrophilic Surfaces for Microscale Flow Control" Colloids Surf., A 2009, 333, 187.

Zou, J.; Chen, H.; Chunder, A.; Yu, Y.; Huo, Q.; Zhai, L. "A Simple Preparation of Superhydrophobic and Conductive Nanocomposite Coating from a Carbon Nanotube-Conjugated Block Copolymer Dispersion" Adv. Mater. 2008, 20, 3337.

Sarkar, S.; Chunder, A.; Fei, W.; An, L.; Zhai, L. "Superhydrophobic Mats of Polymer Derived Ceramics" J. Am. Ceram. Soc. 2008, 91, 2751.

Zou, J.; Liu, L.; Chen, H.; Khondaker, S. I.; McCullough, R. D.; Huo, Q.; Zhai, L. "Dispersion of Pristine Carbon Nanotubes Using Conjugated Block Copolymers" Adv. Mater. 2008, 20, 2055.

Londe, G.; Chunder, A.; Wesser, A.; Zhai, L.; Cho, H. J. "Microfluidic Valves Based on Superhydrophobic Nanosctructures and Switchable Thermosensitive Surface for Lab-on-a-chip (LOC) Systems" Sens. Actuators, B 2008, 132, 431.

Chang, N. -B.; Wanielista, M.; Hossain, F.; Zhai, L.; Lin, K. -S. "Integrating Nanoscale Zero-valent Iron and Titanium Dioxide for Nutrient Removal in Stormwater Systems" NANO 2008, 3, 297.

Zhang, L.; Wang, Y.; Wei, Y.; Xu, W.; Fang, D.; Zhai, L.; Lin, K.-C.; An, L. "A Silicon Carbonitride Ceramic with Anomalously High Piezoresistivity" J. Am. Ceram. Soc. 2008, 91, 1346.

Chen, H.; Muthuraman, H.; Stokes, P.; Zou, J; Liu, X.; Wang, J; Huo, Q.; Khondaker, S. I.; Zhai, L. "Dispersion of Carbon Nanotubes and Polymer Nanocomposite Fabrication Using Trifluoroacetic Acid as a Co-solvent" Nanotechnology 2007, 18, 415606.

Chunder, A.; Sarkar, S.; Yu, Y.; Zhai, L. "Fabrication of Ultrathin Polyelectrolyte Fibers and Their Controlled Release Properties" Colloids Surf., B 2007, 58, 172.

Patents

  1. Zou, J.; Zhai, L.; Huo, Q. "Dispersions of Carbon Nanotubes in Copolymer Solutions and Functional Composite Materials and Coatings Therefrom" US 20090118420 (2009)
  2. Huo, Q.; Khondaker, S.; Zou, J.; Zhai, L.; Chen, H.; Muthuraman, H. "Polymer Composites Having Highly Dispersed Carbon Nanotubes and Methods for Forming Same" US 2009001325 (2009)
  3. Sheng, X.; Zhai, L.; Rubner, M. F.; Cohen, R. E. "Patterned Coatings Having Extreme Wetting Properties and Methods of Making" US 20070166513A1 (2007)
  4. Zhai, L.; Cebeci, Fevzi C.; Cohen, Robert E.; Rubner, Michael F. "Superhydrophilic Coatings with Antireflective and Antifogging Property" US 2007104922 (2007)
  5. Berg, M.; Ahn, H.; Zhai, L.; Cohen, R. E.; Rubner, M. F. "Polyelectrolyte Mutilayers Deposited on a Surface and Converted to a Porous Structure" U. S. 2006029634 (2006)
  6. Zhai, L.; Cebeci, F.; Cohen, R. E.; Rubner, M. F. " Superhydrophobic Coatings that Mimic Lotus Leaf Structure" U.S. 2006029808 (2006)

Current Funding

  • NSF CAREER: Regioregular Poly(3-alkylthiphene) Supramolecular Structures
    PI: Zhai, 6/2008-5/2013
  • NSF FRG: Electronic Properties of Polymer-Derived Amorphous Ceramics
    Co-PI: Zhai, 9/2007-8/2010
  • NSF NUE: Preparing Undergraduates for Careers in Nanotechnology
    Co-PI: Zhai, 6/2008-5/2010
  • US Army Research Laboratory: Development of Surface Modification Techniques for Synthesis of Hybrid Tungsten Nano-Powders
    Co-PI: Zhai, 8/2006 - 8/2009

Past Funding

  • NSF NER: Nanoscale Optical and Electronic Processes in Active Nanostructures and Devices for Solar Energy Conversion
    Co-PI: Zhai, 6/2006 - 12/2007
  • Mechanical, Materials & Aerospace Engineering SFTI Ph1: Failure Mechanisms, Life Prediction and Enhanced Performance of Thermal and Environmental Barrier Coatings
    Co-PI: Zhai, 12/2006 - 3/2008

Graduate Students

The graduate students will be part of a new group, situated in a brand new laboratory, pursuing exciting projects in an interdisciplinary field of chemistry, physics, biology and nanoscience. They will receive a highly interdisciplinary education covering topics ranging from polymer synthesis to device physics. The future success of many emerging technologies currently under development in this country clearly depends on an expanded work force of such diverse scientists.

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