Enhanced Sensitivity of Nonlinear Optical Signatures of Aggregation-Induced Emission

Area of Science:

• Organic electronics
• Photonic materials science
• Supramolecular chemistry

Background:

• Nonlinear optical (NLO) properties are crucial for advanced applications like bioimaging and sensing.
• The influence of molecular aggregation on NLO properties, particularly two-photon absorption (TPA), is not well understood.
• Organic fluorophores offer tunable properties for NLO applications.

Purpose of the Study:

• To investigate the relationship between molecular aggregation and TPA cross-section in the fluorophore TPAPhCN.
• To explore the potential of aggregation-dependent NLO responses for sensing applications.
• To establish a dual-mode optical signature based on the divergence of linear and nonlinear optical responses.

Main Methods:

• Systematic investigation of TPAPhCN aggregation states.
• Measurement of TPA cross-section at varying aggregation degrees.
• Comparison of one-photon excitation (linear) and two-photon excitation (nonlinear) optical responses.

Main Results:

• TPA cross-section increases with the degree of TPAPhCN aggregation.
• TPA signals emerge at early aggregation stages, distinct from linear optical responses.
• TPAPhCN exhibits a dual-mode optical signature based on its aggregation state.

Conclusions:

• Molecular aggregation is a key factor in tuning TPA properties of organic fluorophores.
• TPAPhCN can serve as a self-reporting probe for precise aggregation-state sensing.
• This approach offers a sensitive platform for materials diagnostics and intelligent optical sensing.