Quasi-BIC metasurfaces enable rapid, localized singlet-oxygen generation

Area of Science:

• Photonics
• Materials Science
• Photochemistry

Background:

• Bound states in the continuum (BIC) offer efficient light confinement.
• Hot carriers are crucial for photocatalysis and photodynamic applications.
• Interfacial charge transfer in metal-semiconductor nanostructures is key for energy conversion.

Purpose of the Study:

• To engineer metasurfaces for enhanced hot-carrier generation and singlet oxygen (¹O₂) production.
• To leverage BIC resonance for efficient photon-to-chemical conversion.
• To demonstrate wavelength- and position-selective photodynamic effects.

Main Methods:

• Fabrication of Au-TiO₂ metasurfaces with coupled q-BIC resonance.
• Utilizing photonic engineering to increase optical absorption and reduce electron-hole recombination.
• Investigating hot-carrier-mediated ¹O₂ generation under continuous-wave excitation.

Main Results:

• Achieved a six-order-of-magnitude increase in local ¹O₂ concentration.
• Demonstrated rapid molar-level ¹O₂ concentration within seconds.
• Enabled selective phototoxicity by tuning structural asymmetry and excitation wavelength.

Conclusions:

• BIC-engineered metasurfaces provide a general platform for efficient photon-to-chemical conversion.
• The approach decouples strong absorption from noble metal usage, prolonging carrier lifetimes.
• Offers significant potential for photodynamic therapy, selective oxidation, and microreactor applications.