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Nanotechnology Part 2

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High resolution nanolithography required. Photo taken from: http://news.uns.purdue.edu/UNS/images/chang.quantum.jpeg. Moungi Bawendi (MIT) ... – PowerPoint PPT presentation

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Title: Nanotechnology Part 2


1
Nanotechnology Part 2
  • Bioanalytical Chemistry
  • Spring 2004

2
Selected Recent Nobel Prizes
  • 2001 Physics Lindelof, Copenhagen,
    nanotubes/AFM
  • 1997 Physics Chu, Cohen-Tannoudji, Phillips,
    cold trapping
  • 1996 Chemistry Kurl, Kroto, Smalley, fullerenes
  • 1986 Physics - Gerd Binnig and Heinie Rohrer, IBM
    Zurich, STM

3
Small Materials Have Different Properties
  • Optical NanoDots
  • Electrical
  • Physical
  • Chemical
  • Biological
  • Mechanical
  • Q How can we measure these new properties given
    the scale of the materials with which we are
    working?

4
Band Theory of Solids
Energy states of molecules are quantized Energy
states of solids are bands
Conduction Band
Band Gap
Valence Band
H
H
H2
5
Band Theory of Solids
  • Conductors
  • No Eg
  • Semi-conductors
  • EX Si 1.1 eV
  • EX Ge 0.7 eV
  • EX Sn 0.1 eV
  • Insulators
  • EX C (diamond) 5.5 eV
  • Conclusion Interatomic spacing can be correlated
    with electrical properties

Conduction Band
Band Gap, Eg
Valence Band
6
Quantum Dots
  • Plasmon frequency
  • Smaller particle higher plasmon frequency
  • Breakthrough of the Year 2003 Science Magazine
    (5)
  • Quantum effects important
  • Trapped charge carriers
  • Electrons
  • Holes
  • Absence of electron
  • Behaves like positively charged particle
  • Exciton
  • Electron-hole pair
  • Confined closer than Bohrs radius

hole
Seife, C. Science 2003, 302, 2038-2045.
7
Quantum Dots
CdSe Quantum Dots in hexane
  • Consequence
  • Smaller the quantum dot, the closer electron-hole
    pair is confined, the larger the band gap, the
    higher the exciton absorption and emission
    frequency (the longer the ?s)

Photo taken from http//web.mit.edu/chemistry/na
nocluster/home.html
8
Applications - Computers
  • Transistors switch
  • Based on qu-bits
  • Quantum bits exist in on/off states
    simultaneously
  • Change of spin state for pairs of qubits
  • Advantage faster
  • Disadvantage must isolate each spin
  • High resolution nanolithography required

Photo taken from http//news.uns.purdue.edu/UNS/i
mages/chang.quantum.jpeg
9
Moungi Bawendi (MIT)
  • Education
  • A.B. Harvard 1982
  • Ph.D. U. Chicago 1988
  • Awards
  • 2001 Sackler Prize
  • 1991 Packard Grant
  • 1991 NSF Presidential Young Investigator

Group website http//web.mit.edu/chemistry/nanoc
luster/index.html
10
Dip Pen Nanolithography (DPN)
  • Idea Dip pen in ink and write on
    substrate
  • Can deliver
  • Organic monolayers (thiols) to Au surface
  • Proteins
  • Can create
  • Dots 0.66 µm diameter, 20 s
  • Lines 30 nm width, 5 min (2 µm long)
  • Arrays
  • Q long term stability

Acts as capillary
condensation
Au substrate
Piner, R.D. Zhu, J. Xu, F.Hong, S.H.Mirkin,
C.A. Science 1999, 283, 661-663. Lee, K-B.
Lim, J-H. Mirkin, C.A. J. Amer. Chem. Soc.
2003, 125, 5588-5589.
11
Dip Pen Nanolithography (DPN)
  • Ink Alkane thiol
  • Paper Au substrate
  • Advantage
  • Positive printing method
  • No resist layers to remove

Metal tip
e-
s
Conductive surface
12
Electrochemical Dip Pen Nanolithography (E-DPN)
  • Can deliver M and semiconductors to surface
  • Au, Ge, Cu, Ag, Pd
  • Ex Pt deposition on p-type SiPtCl62- 4e- ?
    Pt 6Cl-
  • 0.4 nm wide by 30 nm long
  • Supporting evidence
  • Can heat (3000C) and melt (5000C)
  • Catalytic activity toward ethylene

Li, Y. Maynor, B.W. Liu, J. J. Amer. Chem.
Soc. 2001, 123, 2105-2106.
13
Chad Mirkin (Northwestern)
  • Education
  • 1986 B.S. Dickinson College
  • 1989 Ph.D. Penn State
  • Awards
  • Feynmann Prize 2002
  • Fellow AAAS 2002
  • ACS Pure Chemistry 1999
  • NSF Young Investigator 1993
  • Director Institute for Nanotechnology Center
    for Nanofabrication and Molecular Self-Assembly
  • 10 Patents

14
Mirkin Timeline
Avail. At URL http//www.chem.nwu.edu/mkngrp/ti
meline.html
15
Scanning Tunneling Microscope (STM)
  • Tunneling current
  • S, distance to surface
  • I ? e-s
  • Constant current image
  • Voltage varied to maintain constant current

Metal tip
e-
s
Conductive surface
16
Atomic Force Microscope (AFM)
  • Piezoelectric ceramic transducer
  • Hooks law
  • F - k x
  • Use in stacks

V
Expands 1 nm/V
17
Atomic Force Microscope (contd)
  • Constant force
  • Deflection mode
  • Vibrating mode
  • Non-contact mode

Feedback unit
piezos
Diode array
laser
sample
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