Visualization and Tracking of Nanostructures in Aqueous Environments

Visualization of morphological change of telescoping multi-walled carbon nanotubes (MWNT) in fluidic environments through the use of functionalized semiconductor nanocrystals.

image gallery

MWNT with Qdots on open tip and side walls

TEM image of multi-walled carbon nanotube with nanocrystals on tip and walls.

Detailed image of groups of Qdots on defect sites

TEM image of groups of nanocrystals attached to defect sites (~ 5.2 nm crystal diameter)

Fluorescent multi-walled carbon nanotubes

CLSM image of nanotubes with nanocrystals fluorescing under UV light

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 1: carbon nanotubes dispersion over electrodes

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 2: carbon nanotube captured by dielectrophoresis and bridging two electrodes

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 3: carbon nanotube fixed to electrode by electron beam deposition

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 4: functionalized nanocrystals attached to defect sites in wall

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 5: nanotube broken electrically, tips are open and dangling bonds exposed

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 6: nanocrystals covalently attached by amidation to the active sites

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 7: single decorated tube tip in retracted position

Concept study of Qdots attached to the telescoping tip of an MWNT

Step 8: telescoping fluorenscent shells of MWNT extended and tracable in fluids


Functionalized semiconductor nanocrystals, also known as quantum dots (QDs), have been successfully attached to double-walled and multi-walled carbon nanotubes (DWNTs and MWNTs) during a case study completed in 2006 at the Institute of Robotics and Intelligent Systems. Characterization in a transmission electron microscope (TEM) in collaboration with Lixin Dong shows that the QDs are attached mostly at the opened tips and defect sites on the sidewalls of nanotubes, suggesting the covalent nature of the bonding and high selectivity to chemically reactive sites. Due to their unique fluorescent properties, the visibility of the nanometer-sized QDs (a few nm thick) under an optical microscope creates the possibility of tracking the motion or morphology change of individual decorated nanotubes in a liquid environment and identifying possible sites for covalent attachment. This enables the integration of carbon nanotubes with biomolecules such as biomolecular motors, for building bio-nanoelectromechanical systems (BioNEMS).

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