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Origami Inspired Self-assembly of Patterned and Reconfigurable Particles
Published on: February 4, 2013
Light-controlled self-assembly of semiconductor nanoparticles into twisted ribbons
Sudhanshu Srivastava1, Aaron Santos, Kevin Critchley
1Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Science (New York, N.Y.)
|February 13, 2010
Summary
Cadmium telluride (CdTe) nanoparticles self-assemble into ribbons that twist into helical shapes when exposed to light. This light-induced twisting is linked to photooxidation and mechanical stress relief in the nanocrystal assemblies.
Area of Science:
- Nanotechnology
- Materials Science
- Physical Chemistry
Background:
- Nanoparticles exhibit collective properties, including self-organization into microscale structures.
- Cadmium telluride (CdTe) nanoparticles can assemble into ordered ribbons.
- Photooxidation processes can influence nanoparticle assembly dynamics.
Purpose of the Study:
- To investigate the self-assembly and light-induced structural transformations of CdS/CdTe nanocrystal ribbons.
- To understand the mechanism behind the helical twisting of nanoparticle assemblies.
- To explore the role of mechanical stress and electrostatic forces in nanoparticle organization.
Main Methods:
- Synthesis of cadmium sulfide (CdS)/cadmium telluride (CdTe) nanocrystals.
- Observation of nanoparticle self-assembly into flat ribbons via slow oxidation.
- Induction of ribbon twisting using visible light illumination.
- Analysis of pitch length variation with illumination dose.
- Computer simulations to model interparticle forces and assembly geometry.
Main Results:
- CdS/CdTe nanocrystal ribbons (1-4 micrometers) self-assembled through slow oxidation.
- Visible light induced twisting of ribbons into left and right helices (250-1500 nm pitch).
- Twisting correlated with photooxidation of CdS and relief of mechanical shear stress.
- Observed intermediate assembly shapes: ellipsoidal clouds, dog-bone agglomerates, ribbon bunches.
- Simulations showed attraction-repulsion balance dictates assembly geometry.
Conclusions:
- Nanoparticle self-assembly can lead to complex, dynamic structures.
- Light can controllably alter the morphology of nanoparticle assemblies via photo-induced stress.
- Interparticle forces are critical in determining the final architecture of nanoparticle superstructures.
