Ligand Basicity Modulates Metal Cation Reduction Potentials at Colloidal Cadmium Chalcogenide Quantum Dot Surfaces

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Redox reactions on semiconductor nanocrystal quantum dot (QD) surfaces are crucial for charge trapping and photoinduced charge transfer.
• Measuring and controlling these surface redox potentials is challenging.

Purpose of the Study:

• To develop a method for controlling and measuring the redox potentials of QD surfaces.
• To investigate the role of ligands in tuning QD surface properties for charge storage and electronic doping.

Main Methods:

• Utilized monoanionic metal carbonyl complexes as electronically tunable X-type ligands for CdSe and CdS QDs.
• Employed IR spectroscopy to monitor C-O stretching vibrations for quantitative measurement of anion dissociation and QD surface reduction.
• Performed spectral redox titrations and spectroelectrochemical experiments.

Main Results:

• Coordination of more Lewis basic anions shifted QD surface reduction potentials to more negative values, covering over 1 V range.
• Demonstrated that complexation energies are key to controlling surface charge storage.
• Showcased anion exchange as a method to control chemical surface reduction and photochemical electronic doping in CdSe QDs.

Conclusions:

• Metal carbonyl complexes offer a versatile platform for tuning QD surface redox potentials.
• Ligand complexation energy is a critical factor in managing charge storage in QDs.
• This approach is generalizable to various QD materials and ligands for tailored electronic properties.