Nanostructure Research Laboratory

Schools of Chemistry and Physics

Robert L. Whetten, Principle Investigator

 
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Overview 

The nanostructure research group is located in the School of Physics of the Georgia Institute of Technology in Atlanta Georgia. The main focus of the group deals with the synthesis and characterization of nanometer scale crystalline molecules (nanocrystals), and highly oriented molecular (Au, Ag) nanocrystalline arrays. Research into the properties of nanometer-scale single crystallites has recently matured into a field that is both fundamental and wide-ranging, although a major source of motivation arises from natural phenomena and from technological questions concerning ultimate limits on the miniaturization of solid-state device elements. 

The electronic, optical and magnetic properties of nanocrystals are modified from those of extended solids by the quantum size effects, which arise from the discreteness of the energy level structure and finiteness of the number of electrons within a band. These are also under investigation by spectroscopic methods, both for isolated particles and for those in arrays of weakly coupled equivalent crystallites. These arrays constitute a novel material form with high potential for unusual and useful properties.

Theoretical modelling, or simulations, are critical in establishing ideas and models for the structural, processing, and other properties of nanocrystals; supercomputer-based simulations are carried out in association with the Georgia Tech Center for Computational Materials Science. 

Synthesis of the nanomolecules is achieved both by liquid phase and aerosol techniques. Characterization is currently being done by high resolution electron microscopy (HREM) at the Georgia Tech Center for High Resolution Electron Microscopy. Small and large angle x-ray powder diffraction (XRD); scanning probe microscopy (SPM), x-ray photoelectron spectroscopy (XPS); IR, near-IR, and UV-vis spectroscopy; optical circular dichroism (CD); and laser desorption (LD) and matrix assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry are among the other characterization tools being used for structural and electronic analysis. 

Current Work

We have recently isolated a series of aurothiol (Au:SR) clusters, with Au(0)-metallic cores ranging in size from ~20 to over 250 Au atoms and saturated by -SR groups. These are related asymptotically to the popular extended-surface phases (thiol-on-gold self-assembled monolayers), as well as to the well established nonmetallic poly-(-Au-S(R)-) forms from which they are prepared. The new cluster compounds are robust (air-, water-, light-stable), and possess other attractive features, in various (R) functional forms, as well as intriguing size-dependent properties, e.g. patterns of charging (redox) transitions and intense coloration. When prepared from the natural thiol glutathione (Glu-CyS-Gly), clusters at the small-size extreme can be exclusively generated; they are extremely hydrophilic, separable by modified gel electrophoresis, and show intense circular dichroism in the gold absorption bands. 

Other separate projects include, conductance in nano-scale wires and mass spectrometry of molecular clusters. 

Press Release (April 1997)

Recent 
Publications 
  1. “Imaging and spectroscopy of gold nanocrystal arrays,” T. P. Bigioni, W. G. Cullen, D. K. Guthrie, L. E. Harrell,   P. N. First, R. L. Whetten, Eur. Phys J. D6, 355-364 (1999).Cover Illustration, J Phys Chem, March 2000
  2. "Giant Gold-Glutathione Cluster Compounds: Intense Optical Activity in Metal-Based Transitions," T. Gregory Schaaff, Robert L. Whetten, J. Phys. Chem. B, 104, 2630-2641 (2000).
  3. "Greengold, a giant cluster compound of unusual electronic structure," E. Gutierrez, R. D. Powell, F. R. Furuya, J. F. Hainfeld, T.G. Schaaff, M. N. Shafigullin, P.W. Stephens, R. L. Whetten, Eur.Phys. J. D (ISSPIC 9) 9 647-651 (December 1999). 
  4. “Crystal structures of molecular gold nanocrystal arrays,” R. L. Whetten, M. N. Shafigullin, J. T. Khoury, T. G. Schaaff, I. Vezmar, M. M. Alvarez, Angus Wilkinson, Acc. Chem. Res. Special Issue on Nanoscale Materials, 1999, 32, 397-406.
  5. "Scanning tunneling microscopy of passivated Au nanocrystals immobilized on Au(111) surfaces," L. E. Harrell, T. P. Bigioni, W. G. Cullen, R. L. Whetten, P.N. First, J. Vac. Sci Technol. B 17(6), November 1999.
  6. “Isolation and Selected Properties of a 10.4 kDa Gold:Glutathione Cluster Compound,” T. Gregory Schaaff, Grady Knight, Marat N. Shafigullin, Raymond F. Borkman, Robert L. Whetten, J. Phys. Chem. B 102, 10643-10646 (1998).
  7. Cover Illustration, J. Phys. Chem.,“Bundling and Interdigitation of Adsorbed Thiolate Groups in Self-Assembled Nanocrystal Superlattices,” Z. L. Wang , S. A. Harfenist and R. L. Whetten , J. Bentley and N. D. Evans J. Phys. Chem. B. 102, 3068-72 (1998), and issue cover illustration.
  8. “Gold Nanoelectrodes of Varied Size: Transition to Molecule-Like Charging,” S. Chen, R. S. Ingram, M. J. Hostetler, J. J. Pietron, R. W. Murray, T. G. Schaaff, J. T. Khoury, M. M. Alvarez, R. L. Whetten, Science,280, 2098 - 2101 (1998).
  9. “On-line sampling and intact mass-analysis of nanometer-size aerosols via time-of-flight high-mass spectrometry,” M. M. Alvarez, I. Vezmar, R. L. Whetten, J. Aerosol Sci. 29, 115-127 (1998) 
  10. “The ensemble coulomb staircase in solution electrochemistry of 28-kDa Au:SR clusters,” R. S. Ingram, M. J. Hostetler, R. W. Murray, T. G. Schaaff, J. T. Khoury, R. L. Whetten, T. P. Bigioni, D. K. Guthrie, P. N. First,J. Am. Chem. Soc.119, 9279-80 (1997).
  11. Cover Illustration, J. Phys. Chem.,“Isolation of smaller nanocrystal gold molecules: robust quantum effects in optical spectra,” T. G. Schaaff, M. N. Shafigullin, J. T. Khoury, I. Vezmar, R. L. Whetten, W. G. Cullen, P. N. First, C. Gutiérrez-Wing, J. Ascensio, M. J. Jose-Yacamán, J. Phys. Chem. B 101(40),7885-91 (1997), and issue cover illustration.
  12. “Optical absorption spectra of nanocrystal gold molecules,” M. M. Alvarez, J. T. Khoury, T. G. Schaaff, M. N. Shafigullin, I. Vezmar, R. L. Whetten, J. Phys. Chem. B 101, 3706-12 (1997). 
  13. “Electron dynamics of passivated gold nanocrystals probed by subpicosecond transientabsorption spectroscopy,” S. L. Logunov, T. S. Ahmadi, J. T. Khoury, R. L. Whetten, M. A. El-Sayed, J. Phys. Chem. B 101, 3713-19 (1997). 
  14. “Structural evolution of smaller gold nanocrystals: the truncated-decahedral motif,” C. L. Cleveland, U. Landman, T. G. Schaaff, M. N. Shafigullin, P. W. Stephens, R. L. Whetten, Phys. Rev. Lett. 79, 1873-6 (1997). 
  15. “Structural evolution of larger gold clusters,” C. L. Cleveland, U. Landman, M. N. Shafigullin, P. W. Stephens, R. L. Whetten, Z. Phys. D 40, 503-8 (1997). 
  16. “Critical sizes in the growth of Au clusters," M. M. Alvarez, J. T. Khoury, T. G. Schaaff, M. N. Shafigullin, I. Vezmar, R. L. Whetten, Chem. Phys. Lett. 266, 91-8 (1997). 
  17. “Three-dimensional hexagonal close-packed superlattice of passivated silver nanocrystals,” S. A. Harfenist, Z. L. Wang, R. L. Whetten, I. Vezmar, M. M. Alvarez, Adv. Mater. 9, 817-22 (1997). 
  18. “Cluster beams from passivated nanocrystals,” I. Vezmar, M. M. Alvarez, J. T. Khoury, B. E. Salisbury, R. L. Whetten, Z. Phys. D 40, 147-51 (1997). 
  19. “Stability and reversibility of conductance steps in metallic nanowires under ordinary ambience," B. E. Salisbury, R. L. Whetten, in Nanowires, edited by P. A. Serena and N. García (Kluwer, Dordrecht, 1997) pp. 219-26.
  20. “Liquid-phase synthesis of thiol-derivatized silver nanocrystals,” S. Murthy, T. P. Bigioni, Z. L. Wang, J. T. Khoury, R. L. Whetten, Mater. Lett.30, 321-5 (1997). 
  21. “Thin films of thio-derivatized gold nanocrystals,” S. Murthy, Z. L. Wang, R. L. Whetten, Phil. Mag. Lett. 75, 321-7 (1997). 
  22. Cover Illustration, J. Phys. Chem, Aug 1996“Structure, dynamics and thermodynamics of passivated gold nanocrystallites and their assemblies,” W. D. Luedtke, U. Landman, J. Phys. Chem. 100, 13323-28 (1996).
  23. “Highly oriented molecular Ag nanocrystal arrays,” S. A. Harfenist, Z. L. Wang, M. M. Alvarez, I. Vezmar, R. L. Whetten, J. Phys. Chem. 100, 13904-10 (1996).
  24. “Reversible manipulations of room-temperature mechanical and quantum transport properties in nanowire junctions,” U. Landman, W. D. Luedtke, B. E. Salisbury, R. L. Whetten, Phys. Rev. Lett. 77, 1362 (1996).
  25. “Nanocrystal gold molecules,” R. L. Whetten, J. T. Khoury, M. M. Alvarez, S. Murthy, I. Vezmar, Z. L. Wang,P. W. Stephens, C. L. Cleveland, W. D. Luedtke, U. Landman, Adv. Mater. 8, 428-433 (1996).
  26. Cover Illustration, Adv. Mater, May 1996“Nanocrystal gold molecules,” R. L. Whetten, J. T. Khoury, M. M. Alvarez, S. Murthy, I. Vezmar, Z. L. Wang, C. L. Cleveland, W. D. Luedtke, U. Landman, in The Chemical Physics of Fullerenes, 10 (and 5) Years Later, ed. W. Andreoni (Kluwer, Dordrecht, 1996) pp. 475-490.
  27. "Nanocrystal Micromulsions: Surfactant-Stabilized Size and Shape," R. L. Whetten and W. M. Gelbart, J. Phys. Chem. 98, 3544 (1994). 
  28. "Adsorption Reactions of Alkali-Halide Nanocrystals: Identification of an Important Surface Defect," M. L. Homer, F. E. Livingston, and R. L. Whetten, Z. Phys. D 26, 20 (1993). 
  29. "Alkali-Halide Nanocrystals," R. L. Whetten, Acc. Chem. Res. 26(2), 49-56 (1993). 
  30. "Processing of Single Nanocrystals," R. L. Whetten, Mat. Sci. Eng. B 19, 8-13 (1993). 
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