Transcript Nanotechnology

Nanotechnology
• What is nano?
• Nanotechnology?
Creation of nanostructures
Applications of the nanostructures
Nanofabrication techniques
Y.-P. Zhao, “Growth and Synthesis of Nanostructured Thin Films,” in “Functional Thin
Films and Nanostructures for Sensors” edited by A. Zribi and J. Fortin (Springer, 2008)
Top-down
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Photo lithography
Electron beam lithography
Microcontact printing
Nanoimprint Mask or maskless ?
Nanosphere lithography?
And so on…
Bottom-up
• Supramolecular assembly
• nanoparticle formation
• monolayer self-assembly
…
Combination of top-down and bottom-up methods
Han, J.T. et al. J. Am. Chem. Soc., 126 (15), 4796 -4797, 2004
The dividing line of top-down and bottom-up sometime is vague and it is
only a matter of opinion
Hah, J. H. et al. J. Vac. Sci. Technol. B (2006). 10.1116/1.2244541
Nanofabrication techniques
Thermo-vapor transport method
A general setup for thermal-vapor transport method
Catalyst-assisted fabrication
Deposition of a catalyst layer, e.g. thermal evaporation of a 10 nm thick metal film
or injection of a precursor which decomposes into particles
ZnO nanorods on Au and NiO catalysts
Physical Vapor Deposition (PVD)
• Thermal evaporation (resistively, electron beam)
• Sputtering (gas ion bombardment)
• Pulsed laser deposition (laser beam)
Chemical Vapor Deposition (CVD)
Reactant gases
Precursors/carrier gas
Laser beam or plasma can be introduced to enhanced the reaction
Can fabricate: carbon nanotubes, inorganic oxide nanorods, nanowire etc.
Liquid Phase Methods
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Sol-gel dip-coating
Electro-spin coating
Block-copolymer
Electro-chemical deposition/etching
Template-based Methods
Kim k. et al.
Applications
Just name a few
• Biosensor
• Chemical sensor
• Drug delivery
• Self-cleaning
• Energy harvesting
…
Biosensor: glucose detection
Biosensor bacterial/virus detection
dye
+
antibody
target
Conventional fluorescence antibody method
gold
Si
nanorods
antibody
+
target
dye
Enhanced fluorescence antibody method
The fluorescence signal will be greatly enhanced by a large amount
of dye molecules on the nanorods.
Thank the author for sharing her research results
Junxue Fu et al 2008 Nanotechnology 19 155502
SEM image of Si nanorods: top view and side view
TEM image of Au coated Si nanorods
What are these dark
dots and what is the
material?
Bio-functionalization of Au/Si Nanorods
gold
antibody
Si nanorods
dye
Dye immobilization on Au/Si Nanorods
NH2
NH2
NH2
+
NH2
45˚C,
overnight
2% (3-Aminopropyl)triethoxysilane
(APTES) in Acetone
O
N
1 hour at room
temperature and
overnight at 4°C
+
Alexa488succinimide ester
Wash by DI
water
H
C
O
C
N
H
Fluorescence Scan
Si film/Alexa488 IF
Si rods/ Alexa488 IR
IR
 9.45
IF
Do sonication in
DI water
Observation under
fluorescence
microscope
Salmonella detection
Sample: Anti-Sal/Au/Si nanorods/Alexa488/2%BSA + Salmonella
Control: Au/Si nanorods/Alexa488/2%BSA + Salmonella
The bacteria were fixed on the glass slides by 95% ethanol. The
unbound nanorods should be washed away by 0.05% Tween 20/FA
buffer after the incubation.
Sample: Anti-Sal/Au/Si nanorods/Alexa488/2%BSA
Fluorescence Scan
532nm(ex.)/526nm SP
emission filter
Fluorescence image
Bright field image
The Alexa488 labeled nanorods (darker particles) stick on the
bacteria due to the antibody-antigen interaction.
Salmonella detection
Control: Au/Si nanorods/Alexa488/2%BSA
Fluorescence Scan
532nm(ex.)/526nm SP
emission filter
Fluorescence image
Bright field image
The control shows there is no fluorescence signal since the nanorods
cannot attach to the bacteria without the antibody.
Lotus effect: self cleaning
A
Barthlot et al. Planta 202, 1 (1997)
Feng et al. Adv, Mater. 14, 1857 (2002)
Motivation
wings of a Cicada orni
Water strider’s leg
Gao et al. Nature 36, 432 (2004)
Lee et al. Langmuir 20, 7665 (2004)
Tune the nanorod coverage
Si coverage f ~ 48%
Deposition angle = 84o
Si coverage f ~ 32%
Deposition angle = 88o
After coating a fluorocarbon monolayer
148o
165o
Water droplets bounce on a sold surface
Water droplets impacting a superhydrophobic surface vs. a normal hydrophobic surface
Quantum Dots for targeting
Challenge?
Nonspecific binding can lead to false signal
Au nanoparticle for in vivo tumor targeting
PEG is a popular polymer in the pharmaceutical industry for reducing nonspecific
uptake of drugs and drug-delivery systems
Qian et al. Nature Biotechnology