1-D Nanorods Remember: –Tomorrow (4/30): Lab #2 report is due –Monday (5/4): Paper w/ group...
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Transcript of 1-D Nanorods Remember: –Tomorrow (4/30): Lab #2 report is due –Monday (5/4): Paper w/ group...
1-D Nanorods• Remember:
– Tomorrow (4/30): Lab #2 report is due
– Monday (5/4): Paper w/ group members name, email, project topic is due
– Wed (5/6): Alissa + Mine, Quiz 2 covering material from 4/27 – 5/4
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http://www.technologyreview.com/news/409496/flexible-nanowire-solar-cells/
• Spontaneous Growth
• Template-based Synthesis
• Electrospinning
• Lithography
Techniques for 1-D Nanostructure Formation
Bottom-up
Top-down
http://mrsec.umd.edu/Research/Seeds.html#Template
2
Spontaneous Growth:
• Anisotropic Growth– Growth rate of planes– Growth imperfections– Accumulation of impurities
http://www.softmachines.org/wordpress/?p=202
http://www.its.caltech.edu/~atomic/snowcrystals/designer2/designer2.htm 3
Oriented attachment• Solution method, controlled with ligands
and growth conditions
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CrystEngComm, 2014,16, 1419-1429
Talapin Group, U Chicago https://talapinlab.uchicago.edu/page/nanocrystal-synthesis
Hydrothermal Synthesis• Like heat up method for nanocrystlas• Can be free standing or on substrate
6Chem. Soc. Rev., 2014,43, 2187-2199
PbTiO3
Evaporation-Condensation• Helical Nanostructures & Nanorings (Wang,
2003)
8
Wang, Z. L. MRS Bull. 2007,
VLS or SLS Growth• VLS: Vapor-Liquid-Solid• SLS: Solution-Liquid-Solid
• Impurity or catalyst introduced
• Different from Evaporation-Condensation1. No screw dislocations in growth direction
2. Impurities always required
3. Liquid-like globule always found in tip of nanowires
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VLS Growth Method
1. Growth species evaporated2. Growth species diffused and dissolved into
droplet3. Droplet (with growth species) deposits on
growth surface4. Growth species diffused and precipitated
onto growth surface
N & N, Fig. 4.11
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VLS Growth: Control of Nanowire Size
• Dependent on size of liquid catalyst droplets– Small droplets:
• thin layer of catalyst on substrate• anneal at high temperature
Gudiksen, M.S., et al., J. Phys. Chem. B105, 4062 (2001).
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Classic: Si Nanowire/Gold Catalyst
• Filler Group, Georgia Techhttp://fillergroup.gatech.edu/research/
12
• Spontaneous Growth
• Template-based Synthesis
• Electrospinning
Techniques for 1-D Nanostructure Formation
Bottom-up
http://mrsec.umd.edu/Research/Seeds.html#Template
14
Template-Based Synthesis• Used for polymers, metals, semiconductors,
oxides• Membranes as templates
Methods of filling1. Electroplating2. Colloid, melt, or vapor
15Aluminum oxide templateSensors 2005, 5, 245-249
Template-based Synthesis
Requirements for Membranes
1. Chemically and thermally inert during synthesis
2. Depositing materials must “wet” internal pores3. Growth:
• Nanorods/Nanowires:• Must start from one end of pore end at opposite
• Nanotubules:• Must start from pore wall and move in
4. Easy release of nanostructures after synthesis
16
Template-Based Synthesis
• Ran Research Group, Penn Statehttp://research.chem.psu.edu/axsgroup/Ran/research/templatesynthesis.html
17
Electrochemical Deposition
Method:1. Charged growth species moves through solution
in one direction when electric field applied2. Charged growth species reduced at deposition
surface (also an electrode)
http://tutors4you.com/electrochemicalcell.jpg 18
Electrochemical Deposition
• Products:– Metals: Ag, Ni, Co, Cu, Au nanowires: <10 nm- 200
nm dia– Semiconductors: CdSe, CdTe– Polymers: polyporrole
N & N, Fig. 4.21
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Template Filling• Liquid precursor poured into template
pores• Requirements:
1. “Wetability” of pore walls2. Template materials must be inert3. Control of shrinkage during solidification
Can use centrifugation
• Vapor precursor can be used Diffuse gas through porous material, then heat
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Positive Templates
• Green rod is DNA or CNTNanoscale, 2014, 6, 4027-4037
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Polypyrrole on DNA
Step/Groove Templates
• Guide horizontal growth of nanostructures• Used w/ Evaporation-Condensation or VLS22
GaN NanowiresWeizmann Institutehttp://wis-wander.weizmann.ac.il/nanowires-get-into-the-groove#.VD3YEvldWSo
• Spontaneous Growth
• Template-based Synthesis
• Electrospinning
Techniques for 1-D Nanostructure Formation
Bottom-up
http://mrsec.umd.edu/Research/Seeds.html#Template
23
Electrospinning• Electrical forces at surface overcome surface
tension Electrically charge jet is ejected• Fiber can be directed or accelerated by electrical
forces• Product: 30+ types of polymer, 40 -500 nm
diameter– Can be collected in sheets or other forms– Morphology depends on:
• Solution concentration• Applied electric field strength• Feeding rate of precursor solution
N & N, Fig. 4.33
24
Electrospinning
http://nano.mtu.edu/documents/Electrospinning.swf
http://www.centropede.com/UKSB2006/ePoster/images/background/ElectrospinFigure.jpg
25
Lab #3 – Surface Modification• Form a SAM on a copper substrate • Observe change in surface properties w/
different tail groups– Like dissolves like– Hydrophilic : charged, H-bonding, large dipole– Hydrophobic : neutral, no H-bonding, small
dipole
• What will the difference be between water drop on hydrophilic vs hydrophobic surface?
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