june 13, 2015sean glass 2003 two and three- dimensional nanoscale structures for molecular...
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April 18, 2023 Sean Glass 2003
Two and three-dimensional nanoscale structures for molecularelectronics
Controlled self assembly of charged-stabilized goldnanoparticles into close-packed arrays
Executive Summary
Origins of the project Initial Research The tilting method Coffee Drops & Nanoparticles? Current Status and Future plans
Molecular Electronics
Using Individual Molecules as electronic devices Different paths to achieve molecular devices Planar Devices The Nanocell
The Nanocell
Gold Nanoparticles Molecular Wires Addressable through leads
into the nanocell Programmed to function
as a logic device
Gold Nanoparticle Deposition
Ideal - Hexagonal close packing
Confined to within the Nanocell
Not easily trapped using voltage or magnetic fields
SiO2 Microsphere Deposition
Photonic band gap crystals
Numerous methods previously explored Spinning Tilting Tapered Cell
Ng et al. Nanotechnology 13
My result with 100nm Polyspheres
1st Experiments with Tilting Setup
Temperature / Concentration Constant / Varied Tilt
Polyspheres and Gold Nanoparticles Au: 60nm 100nm
PS: 50nm 100nm 500nm
Results
Best assembly with 0 tilt Assembly at the rim of the drop Polyspheres assembly better than Au
Nanoparticles Distinct layers form with 60nm Au nanoparticles!
Nanoparticle Deposition at the Rim
Occurs at edge of drop. Caused by pinning of edge of drop to surface and
capillary forces that are created as a result during evaporation
From “Capillary flow as the causeof ring stains from driedliquid drops”Robert D. Deegan*, Olgica Bakajin*, Todd F. Dupont†,Greb Huber*, Sidney R. Nagel* & Thomas A. Witten*
Nature, October 22 1995?
Hypothesis – Particle Motion
V V-V
Velocity is proportional to height b/ch(t) * v(t) = constant
(Deegan et al. Physical Review E Volume 62 Number 1)
0 tilt
Significant tilt
Layer Formation Control Hypothesis
Depends directly on J(r) – the evaporation
profile Depends on temperature
and area of evaporation v(r) depends on J(r) and
the contact angle J(r) depends on T and
surrounding environment
Concentration
Deegen et Al. demonstrated on a macro scalehow different evaporative profiles affect deposition at the contact line
Ongoing work to be done with step formation / control Vary concentration, temperature, and evaporation
profile while fixing tilt Computer Simulation of Model
Further Experiments
Multiple Drops
Ultrasonic bath to increase ordering
IV measurements through Au NP arrays