Advancing Light-Driven Reactions with Surface-Modified Optical Fibers

Conspectus The challenge of optimizing decentralized water, wastewater, and reuse treatment systems calls for innovative, efficient technologies. One advancement involves surface-modified side-emitting optical fibers (SEOFs), which enhance biochemical and chemical light-driven reactions. SEOFs are thin glass or polymeric optical fibers with functionalized surfaces that can be used individually or bundled together. They can be attached to various light sources, such as light-emitting diodes (LEDs) or lasers, which launch ultraviolet (UV) or visible light into the fibers. This light is then emitted along the fiber’s surface, creating irradiance similar to a glow stick. The resulting SEOFs uniquely deliver light energy to complex environments while maximizing photon utilization and minimizing energy loss, addressing long-standing inefficiencies in photolysis and photocatalysis systems. SEOFs generate and leverage refracted light and evanescent waves to achieve continuous irradiation of their cladding, wherein photocatalysts are embedded. This method contrasts with traditional slurry-based systems, where light energy is often scattered or absorbed before reaching the reaction sites. Such scattering typically reduces quantum yields and reaction kinetics. In contrast, SEOFs create a controlled light delivery system that enhances reaction efficiency and adaptability to diverse applications. Important chemical and physical concepts are explored when scaling up SEOFs for three potential engineered applications. The selection of polymer materials and nanoparticle compositions is crucial for optimizing SEOFs as waveguides for visible to UV-C wavelengths and for embedding surface-accessible photocatalysts within porous polymer coatings on SEOF surfaces. Additionally, understanding how light propagates within SEOFs and emits along their exterior surface and length is essential for influencing the quantum yields of chemical products and enhancing biochemical sensitivity to low UV-C exposure. UV-C SEOFs are employed for germicidal disinfection, inactivating biofilms and pathogens in water systems. By overcoming UV light attenuation issues in traditional methods, SEOFs facilitate uniform distribution of UV-C energy, disrupting biofilm formation at early stages. SEOFs enhance UV-A and visible-light photocatalytic degradation of pollutants. Embedding photocatalysts in porous polymer cladding enables simultaneous improvements in reaction kinetics and quantum yields. SEOFs enable decentralized light-driven production of clean energy resources such as hydrogen, hydrogen peroxide, and formic acid, offering sustainable alternatives for off-grid systems. The design principles of SEOFs emphasize scalability, flexibility, and efficiency. Recent innovations in polymer chemistry, nanoparticle coatings, and surface roughness engineering have further optimized light delivery and side-emission. Tailoring the refractive index and nanoparticle distribution on fiber surfaces ensures precise evanescent wave propagation, enhancing photocatalytic performance. These advancements, coupled with scalable fabrication techniques, have positioned SEOFs as promising platforms for broad photochemical applications. By summarizing recent advances and identifying future needs, this Account positions SEOFs as a transformative approach to light-driven reactions, merging cutting-edge materials science with sustainable water treatment and energy production goals. This emerging technology offers immense potential to reshape photochemical processes for decentralized applications. Despite significant progress, challenges remain. Future research should focus on optimizing catalyst loading, improving uniformity in side emissions, and enhancing polymer durability for long-term operational stability. Additionally, scaling SEOF configurations to multifiber bundles and integrating them into decentralized water systems will be critical for broader adoption.