Force-Induced Luminescence Suppression in Colloidal Clusters Revealed by Optical Tweezers

Area of Science:

• Materials Science
• Nanotechnology
• Photophysics

Background:

• Colloidal clusters, particularly Cs3Cu2I5 perovskite, suffer from aggregation, which suppresses their luminescence.
• This aggregation limits their application as efficient luminescent materials.
• Understanding intercluster forces is crucial for controlling cluster behavior and luminescence.

Purpose of the Study:

• To measure intercluster forces in Cs3Cu2I5 perovskite colloidal clusters using noncontact optical tweezers.
• To investigate the relationship between intercluster forces, intercluster distance, and photoluminescence intensity.
• To determine the critical intercluster distance for optimal luminescent performance and stability.

Main Methods:

• Utilized noncontact optical tweezers generated by autofocusing beams to measure intercluster forces.
• Employed Cs3Cu2I5 perovskite colloidal clusters suspended in n-hexane.
• Correlated measured forces with photoluminescence intensity as a function of intercluster distance.

Main Results:

• A critical intercluster distance of approximately 235 nm was identified, where net intercluster forces approach zero.
• Above 235 nm, weak van der Waals attraction and electrostatic repulsion lead to stable, non-aggregated clusters with high photoluminescence.
• Below 235 nm, dominant van der Waals attraction causes aggregation and significant photoluminescence suppression.

Conclusions:

• Accurate measurement of intercluster forces allows for the determination of optimal conditions for luminescent materials.
• Maintaining an intercluster distance above the critical threshold is essential for preventing aggregation and maximizing luminescence.
• Findings provide theoretical insights for designing high-performance luminescent materials and explain force-induced luminescence suppression.