Size-dependent second virial coefficients of quantum dots from quantitative cryogenic electron microscopy

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Understanding interparticle interactions is crucial for controlling the properties of colloidal systems.
• Lead selenide quantum dots (PbSe QDs) are important nanomaterials with tunable optoelectronic properties.
• Accurate determination of the second virial coefficient is key to characterizing these interactions.

Purpose of the Study:

• To determine the second virial coefficient of PbSe quantum dots (QDs) in an apolar solvent using cryo-transmission electron microscopy (cryo-TEM).
• To investigate the size dependence of interparticle interactions in PbSe QD dispersions.
• To elucidate the nature of attractive forces between PbSe QDs.

Main Methods:

• Cryogenic transmission electron microscopy (cryo-TEM) was used to image vitrified samples of PbSe QDs.
• Radial distribution functions were calculated from cryo-TEM images to analyze particle distribution.
• Second virial coefficients were derived from the radial distribution functions.

Main Results:

• The second virial coefficient was successfully determined for PbSe QDs using cryo-TEM.
• Calculated coefficients showed good agreement with those obtained via analytical centrifugation and small-angle X-ray scattering.
• The study revealed that the interparticle interaction strength is proportional to the QD surface area.

Conclusions:

• Cryo-TEM is a viable method for quantifying interparticle interactions in QD dispersions.
• Surface ion interactions are identified as a likely cause for the observed attractive forces between PbSe QDs.
• The findings provide insights into the fundamental forces governing QD assembly and behavior.