Title: Nanotechnology Part 2
1Nanotechnology Part 2
- Bioanalytical Chemistry
- Spring 2004
2Selected 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
3Small 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?
4Band Theory of Solids
Energy states of molecules are quantized Energy
states of solids are bands
Conduction Band
Band Gap
Valence Band
H
H
H2
5Band 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
6Quantum 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.
7Quantum 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
8Applications - 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
9Moungi 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
10Dip 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.
11Dip Pen Nanolithography (DPN)
- Ink Alkane thiol
- Paper Au substrate
- Advantage
- Positive printing method
- No resist layers to remove
Metal tip
e-
s
Conductive surface
12Electrochemical 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.
13Chad 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
14Mirkin Timeline
Avail. At URL http//www.chem.nwu.edu/mkngrp/ti
meline.html
15Scanning 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
16Atomic Force Microscope (AFM)
- Piezoelectric ceramic transducer
- Hooks law
- F - k x
- Use in stacks
V
Expands 1 nm/V
17Atomic Force Microscope (contd)
- Constant force
- Deflection mode
- Vibrating mode
- Non-contact mode
Feedback unit
piezos
Diode array
laser
sample