Highly sensitive optical ion sensor with ionic liquid-based colorimetric membrane/photonic crystal hybrid structure

Area of Science:

• Nanotechnology
• Materials Science
• Optical Sensing

Background:

• Ionic liquid-based colorimetric membranes (CMs) are vital for optical ion sensing.
• Two-dimensional photonic crystal slabs (PCS) offer advanced light control capabilities.
• Integrating CMs and PCS presents an opportunity for enhanced sensing performance.

Purpose of the Study:

• To develop and characterize a novel hybrid colorimetric membrane on a photonic crystal slab (CM/PCS) for highly sensitive optical ion sensing.
• To investigate the optical properties and sensing mechanisms of the CM/PCS hybrid structure.
• To demonstrate the enhanced absorption sensitivity for calcium ion detection.

Main Methods:

• Fabrication of the CM/PCS hybrid structure using nanoimprinting and spin-coating techniques.
• Optical characterization through reflection spectrum measurement and simulation.
• Analysis of the relationship between CM thickness and absorption sensitivity enhancement.

Main Results:

• Successful fabrication of a thin CM/PCS hybrid structure with controlled CM thickness.
• Demonstrated drastic absorption of light confined in PCS by the CM when spectral overlap occurs.
• Achieved approximately 78-fold improvement in absorption sensitivity for Ca ion sensing compared to CM alone.
• Identified that controlled light in PCS enhances the absorption cross-section of dye molecules.

Conclusions:

• The CM/PCS hybrid structure significantly enhances optical ion sensing sensitivity.
• Controlled light confinement within the PCS plays a crucial role in improving absorption efficiency.
• This highly sensitive optical ion sensor is suitable for micro-scale bio-analysis, including cell dynamics studies using reflectometric Ca ion detection.