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Fabrication and Characterization of Nanopore-Array Electrodes

Fabrication and Characterization of Nanopore-Array Electrodes. Track-etched membranes. Diblock copolymer. 200 nm. “Chemistry” within nanometer-scale pores (nanopores) Chemical sensing using nanopores. 1. Takashi Ito. Department of Chemistry, Kansas State University.

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Fabrication and Characterization of Nanopore-Array Electrodes

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  1. Fabrication and Characterization of Nanopore-Array Electrodes Track-etched membranes Diblock copolymer 200 nm “Chemistry” within nanometer-scale pores (nanopores) Chemical sensing using nanopores 1 Takashi Ito Department of Chemistry, Kansas State University Softmatter miniconference, KSU-Physics, May 16, 2007

  2. Nanopore-Array Electrodes (NAEs) 2 1. An array of parallel cylindrical nanopores • Good model to study the mass transport behaviors (fluid dynamic simulations) • Well-defined control of molecular interactions by surface modification • Relatively easy preparation • Larger electrochemical signals; no difficulty to find nanopores for fluorescence microscopy 2. Insulator-based nanopores • Control the electric field in the pores and thus molecular flow (electrokinetic effects) 3. Nanopores immobilized on an electrode • Support a nanoporous membrane: wider thickness range • Preconcentrate analytes (via electrokinetic effects and via binding sites immobilized on it) • Detect the molecules within the nanopores 4. Methods to measure mass transport • Electrochemistry: quick, quantitative, suitable for the future sensor applications • Fluorescence: directly “see” molecular behaviors, information on molecular structure

  3. Issues to be Studied in this Project 3 1. Clarify “chemistry” within polymer-based cylindrical nanometer-scale pores • “Chemistry” covalent reactions on nanopore surface, chemical interactions (mass transport, entrapment) • Mass transport behaviors of molecules and biomolecules in the nanopores chemical interactions, steric effects, electrokinetic effects 2. Develop new analytical methods for biomolecules (proteins, oligonucleotides and viruses) using the nanopores • Chemical sensors, biosensors • Chemical separation

  4. Previous Achievements and Ongoing Topics 200 nm 4 1. Toestablish simple and reproducible ways to prepare nanopore-array electrodes Diblock copolymer Track-etched membranes 2. To establish ways to characterize the nanopore-array electrodes & nannoporous structure • electrochemistry(in addition to AFM, EM, ellipsometry, IR,…) Ito, T.; Audi, A. A.; Dible, G. P. Anal. Chem.2006, 78, 7048-7053. 3. To control chemical interactions within nanopores • identify chemical functional groups (nanopores from a diblock copolymer) • control: chemical modification (covalent; polymer adsorption) in particular, reduction of nonspecific adsorption (PEG?) 4. To measure molecular mass transport and entrapment in nanopores • electrochemistry • fluorescence (single molecule spectroscopy, with Dr. Higgins) 5. To demonstrate chemical sensing using nanopore-array electrodes

  5. Other Projects in Ito‘s Group 2. Surface Chemistry of GaN (Collaboration with Dr. Edgar (Chem. Eng.)) 1. Multiphoton Photolithography (Collaboration with Dr. Higgins (Chem.)) Higgins, D. A.; Everett, T. A.; Xie, A.; Forman, S. M.; Ito, T. Appl. Phys. Lett.2006, 88, 184101. Xie, A.; Ito, T.; Higgins, D. A. Adv. Funct. Mater.2007, in press. 20 µm 475 nm 0 nm 5 Interdisciplinary research involving analytical chemistry and nanotechnologies My Previous Works (except electrochemistry-related works) 1. Carbon Nanotube-Based Coulter Nanoparticle Counters 2. Molecular STM Tips for Single Molecule Discrimination 3. Chemical Force Microscopy Ito, T.; Namba, M.; Bühlmann, P.; Umezawa, Y. Langmuir1997, 13, 4323. Ito, T.; Citterio, D.; Bühlmann, P.; Umezawa, Y. Langmuir1999, 15, 2788. Ito, T.; Sun, L.; Henriquez, R. R.; Crooks, R. M. Acc. Chem. Res. 2004, 37, 937. Nishino, T.; Ito, T.; Umezawa, Y. Proc. Natl. Acad. Sci. USA2005, 102, 5659.

  6. Instruments & Techniques in Ito’s Group • electrochemistry (potentiostat, AC impedance, potentiometer) • AFM/STM (electrochemistry, in solution, in air, in Ar) • organic thin film characterization (spectroscopic ellipsometer, contact angle goniometer, FTIR-RAS/ATR) • fluorescence microscopy (fluorescence microscope) • simple organic synthesis (organic mercaptans) 6 For my near-future projects… • Relatively large biomolecules (or their assemblies; except DNA; > 5 nm in diameter). - Their dynamic properties (structural change, deformation, denature) is medically or biologically important. - They are available commercially or through collaboration. - They can be fluorescently labeled (e.g., for FRET experiments).

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