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Analytical Chemistry, Nanomaterials, Electrochemistry, and Microfluidics
Research Overview
Our research interests involve development of new sensing techniques based on nanomaterials such as nanoporous materials and ultrathin films for chemical and biological targets of medical and environmental interests. Additionally, we strive to understand the sensing mechanisms of such techniques and to incorporate such sensors into microfluidic devices.
Nanomaterials, including nanoparticles (1-100 nm in diameter), nanopores (2-1000 nm in pore diameter) and ultrathin films (1-1000 nm thick), are known to have unique physical and chemical characteristics that are applicable for new separation and detection principles. Their nanometer-scale size is comparable to biological macromolecules such as DNA and proteins, and thus can be used to recognize chemical and biological species with unique selectivity, and in favorable cases, to recognize individual molecular species. These features of nanomaterials can provide a means to develop unique sensing techniques that cannot be easy achieved using conventional techniques. In addition, because of their small size, sensing devices based on such materials can be easily incorporated into µm~nm-scale analytical devices known as microfluidic (Lab-on-a-chip) devices.
Our research involves (A) preparation of nm-scale materials (more specifically, nanoporous materials and ultrathin films), (B) characterization of the materials using various electrochemical, spectroscopic and microscopic techniques, (C) application of the nanomaterials for separation and/or detection of chemical and biological targets, (D) quantitative understanding the separation and/or detection mechanism, and (E) incorporation the nanomaterial-based sensors into microfluidic devices and application of the device for practical medical and environmental purposes. These research procedures demonstrate that our research will have an impact on many fundamental aspects of analytical, physical and material chemistry as well as on developing practical analytical devices.
So far, we have established a way to characterize electrodes modified with a membrane containing an array of cylindrical nanopores using electrochemical methods, and have clarified surface chemistry of nanopores prepared from polystyrene-poly(methylmethacrylate) diblock copolymers (Figure 1) [2,5,10,11]. We have also developed a multiphoton photolithography to fabricate submicron-scale devices based on polymer thin films on planar transparent substrate (Figures 2 and 3) (in collaboration with Dr. Higgins (KSU, Chemistry)) [1,3,4,9]. In addition, we have systematically investigated the surface chemistry of GaN for the future sensor applications (in collaboration with Drs. Edgar and Hohn (KSU, Chemical Engineering) and Dr. Eddy (Naval Research Lab)) [8], and have developed nanoscience-related experiments for undergraduate lab courses [6,7].
Selected Publications
[1] D. A. Higgins, T. A. Everett, A. Xie, S. M. Forman, T. Ito “High-Resolution Direct-Write Multiphoton Photolithography in Poly(methylmethacrylate) Films” Appl. Phys. Lett. 2006, 88, 184101.
[2] T. Ito, A. A. Audi, G. P. Dible “Electrochemical Characterization of Recessed Nanodisk-Array Electrodes Prepared from Track-Etched Membranes” Anal. Chem. 2006, 78, 7048-7053.
[3]
A. Xie, T. Ito, D. A. Higgins “Fabrication and Characterization of Polymer/Liquid-Crystal Composite Diffractive Optics by Multiphoton Methods” Adv. Funct. Mater. 2007, 17, 1515-1522.
[4] S. Ibrahim, D. A. Higgins, T. Ito “Direct-Write Multiphoton Photolithography: A Systematic Study of the Etching Behaviors in Various Commercial Polymers”, Langmuir 2007, 23, 12406-12412.
[5]
Y. Li, H. C. Maire, T. Ito “Electrochemical Characterization of Nanoporous Films Fabricated from a Polystyrene–Poly(methylmethacrylate) Diblock Copolymer: Monitoring the Removal of the PMMA Domains and Exploring the Functional Groups on the Nanopore Surface”, Langmuir 2007, 23, 12771-12776.
[6] T. Ito “Observation of DNA Molecules Using Fluorescence Microscopy and Atomic Force Microscopy: An Undergraduate Instrumental Analysis Laboratory Experiment” J. Chem. Educ. 2008,
85, 680-682.
[7] T. Ito, D.-M. N. T. Perera, S. Nagasaka “Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment”, J. Chem. Educ. 2008, in press.
[8] T. Ito, S. M. Forman, C. Cao, F. Li, C. R. Eddy, Jr., M.A. Mastro, R.T. Holm, R.L. Henry, K. L. Hohn, J. H. Edgar “Self-Assembled Monolayers of Alkylphosphonic Acid on GaN Substrates” Langmuir 2008, in press.
[9] Y. Xiao, T. Ito, D. A. Higgins “Grayscale Patterning of Polymer Thin Films with Nanometer Precision by Direct-Write Multiphoton Photolithography” Langmuir 2008, in press.
[10]
Y. Li, T. Ito “Surface Chemical Functionalization of Cylindrical Nanopores Derived from a Polystyrene-Poly(methylmethacrylate) Diblock Copolymer via Amidation” Langmuir 2008, in press.
[11] H. C. Maire, Y. Li, S. Ibrahim, T. Ito “Roughness-Induced Vertical Alignment of Cylindrical Domains in Thin Films of a Polystyrene–Poly(methylmethacrylate) Diblock Copolymer Studied Using Atomic Force Microscopy and Cyclic Voltammetry” submitted.
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