Mechanism of a Mussel-Inspired Polydopamine-Modified Bioaffinity Spider Silk Self-Cleaning Photocatalyst for Enhanced Bioaerosol Purification

The demand for self-cleaning air purification is urgently increasing due to concerns for human health and long-term use. Herein, this study investigated the enhanced mechanism of a self-cleaning artificial spider silk (PMAS) photocatalyst, which was modified by bioaffinity polydopamine (PDA) for highly efficient bioaerosol adhesive capture and photocatalytic inactivation. By increasing the bioaffinity of the PMAS photocatalyst, bioaerosols can adhere to the surface, increasing capture efficiency by 50–700%. The captured bioaerosols were concentrated on the spindle knots of the PMAS photocatalyst, forming droplet reactors for subsequent photocatalytic inactivation. Through a combination of experiments and calculations, the mechanism of enhanced capture efficiency by the PMAS photocatalyst was revealed: PDA endows doubled adsorption energy and tripled adhesion forces between the interfaces of bioaerosols and the photocatalyst due to the abundant indole and amino groups. PDA also provides hydrophilic properties to the PMAS photocatalyst, leading to a sevenfold increase in captured bacterial droplet volumes. Due to its bioaffinity, hydrophilic, and photocatalytic properties, the PMAS photocatalyst possesses self-cleaning capability by in situ inactivation of microorganisms and purification of self-washed debris, facilitating repeated use for long-term capture and regeneration of occupied active sites. This work may offer rational designs for a new generation of self-cleaning photocatalysts for air purification.