Nanotechnology Chemical Imaging:  As yet, there exists no powerful technique for chemical imaging under ambient conditions at the nanoscale.  We are developing apertureless infrared near field spectroscopy to help fill that gap.  Our current sensitivity permits us to image 24 bp DNA at submonolayer coverage, with a tunable IR source.  We are developing alternative tunable IR sources for broader spectral coverage and greater sensitivity to macromolecular conformations at surfaces. Akhremitchev, B. B; Walker G. C. “Apertureless Scanning Near-Field Infrared Microscopy of Rough Polymeric Surface”, Langmuir, 2001, 17, 2774-2781. Akhremitchev, B. B.; Sun, Y.; Stebounova, L.; Walker, G. C.  “Monolayer-Sensitive Infrared Imaging of DNA Stripes Using Apertureless Near-Field Microscopy”, Langmuir,  2002, 18, 5325-5328. Stebunouva, L.; Akhremitchev, B.; Walker, G. C. “Enhancement of the weak scattered signal in apertureless near-field scanning infrared microscopy”, Rev. Sci. Inst., 2003, 74, 3670-3674. Nanophotonic Apertures: In collaboration with researchers at CMU, we are designing and testing nanoscale apertures for hybrid information storage technologies. Below is an FDTD simulation of a ridge waveguide and its experimental realization. Chen, F.; Itagi, a.; Stebounova, L.; Bain, J.; Stancil, D. D. Walker, G.; Schlesinger, T. E.  “A Study of Near-field Aperture Geometries on VSALs “, SPIE-,Opt. Soc. Am., 2003, 0000. Chen, F.; Stebounova, L.; Itagi, A.; Akhremitchev, B. B.; Bain, J. A. ; Stancil, D. D.; Walker, G. C.; Schlesinger, T.E. “Imaging of Optical Field Confinement in Ridge Waveguides Fabricated on a Very Small Aperture Laser (VSAL)”, Appl. Phys. Lett., in press. Nanomaterials Synthesis and Assembly: We are synthesizing materials to be used as interconnects in next generation electronic devices and sensors. Our strategy is to use macromolecules or surface topography to direct the self-assembly. Metals or semi-conductors can then be added to the templating polymers.  Chen, J.; Liu, H.; Weimer, W. A.; Halls, M. D.; Waldeck, D. H.; Walker, G. C.  “Noncovalent Engineering of Carbon Nanotube Surfaces by Rigid Functional Conjugated Polymers”, J. Am. Chem. Soc., 2002, 124, 9036-9037. Sun, Y.; Walker, G. C. "Two-Dimensional-Self-Assembly of Latex Particles in Wetting Films on Patterned Polymer Surfaces", J. Phys. Chem. B., 2002, 106(9); 2217-2223. Nanoscale Conductivity: We have also developing conductive probe AFM methods for examining the role of pressure in  nanoscale conductivity of polymers.  Tivanski, A. V.; Bemis, J. E.; Akhremitchev, B. B.; Liu, H.; Walker, G.C. “Adhesion Forces in Conducting Probe Atomic Force Microscopy”, Langmuir, 2003, 19, 1929-1934. Tivanski, A. V.; He, Y.; Waldeck, D. H.; Walker, G. C. “Conjugated Thiol Linker for Enhanced Conductivity of Gold-Molecule Contacts”, submitted. Gu, Y.; Akhremitchev, B. B.; Walker, G. C.; Waldeck, D. H. “Structural Characterization and Electron Tunneling at n-Si/SiO2/SAM/Liquid Interface,” J. Phys. Chem. B, 1999, 103, 5220-5226. Walker, G. C., Beratan, D. N. "Electron Transfer", in Encyclopedia of Chemical Physics and Physical Chemistry, Eds. J. Moore and N. Spencer, (Institute of Physics Publishing, Bristol, UK, 2001). III, 2657-2680. Nanostructures on Surfaces