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Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...

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Related Experiment Video

Updated: May 18, 2026

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

Published on: December 11, 2013

Quenching dynamics in CdSe nanoparticles: surface-induced defects upon dilution.

Lucia Hartmann¹, Abhishek Kumar, Matthias Welker

¹Laboratoire d'Electronique Moléculaire, Organique et Hybride (LEMOH), INAC/SPrAM UMR 5819 (CEA-CNRS-UJF), CEA Grenoble, 17, rue des Martyrs, F-38054 Grenoble, France.

|September 27, 2012

Summary

Ligand removal from colloidal cadmium selenide (CdSe) quantum dots (QDs) quenches fluorescence. Tri-octylphosphine (TOP) addition restores fluorescence, revealing an average of 3.0 quenching sites per QD.

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Area of Science:

Materials Science
Nanotechnology
Physical Chemistry

Background:

Colloidal semiconductor quantum dots (QDs) like cadmium selenide (CdSe) are crucial in optoelectronics.
Surface ligands stabilize QDs but can influence their photophysical properties.
Understanding ligand-QD interactions is key to controlling QD fluorescence.

Purpose of the Study:

To investigate the impact of ligand removal on CdSe quantum dot (QD) fluorescence.
To quantify the number of quenching sites on QD surfaces.
To elucidate the dynamics of fluorescence quenching and restoration.

Main Methods:

Time-resolved fluorescence decay analysis of QD suspensions.
Ligand shell composition analysis using 1H nuclear magnetic resonance (NMR) spectroscopy.
Dilution and titration experiments with specific ligands (TOP, OA, SA).

Main Results:

Ligand removal via dilution caused significant fluorescence quenching in CdSe QDs.
Addition of tri-octylphosphine (TOP) effectively restored QD fluorescence.
Nonparametric analysis revealed an average of 3.0 ± 0.1 quenching sites per QD upon TOP removal.
Quenching rates were found to be additive, and individual site quenching dynamics were extracted.

Conclusions:

The study quantifies ligand-induced quenching sites on CdSe QDs.
Ligand dynamics and their role in fluorescence quenching are elucidated.
The findings offer insights for optimizing QD stability and performance through ligand engineering.