MSc Thesis Defense: Helin Hivda Yıldırım, LIGNIN-BASED PHOTOTHERMAL MATERIALS FOR LIGHT-ACTIVATED ANTIBACTERIAL APPLICATIONS, Date & Time: June 11, 2026 – 10:00 AM , Place: FENS 2019
LIGNIN-BASED PHOTOTHERMAL MATERIALS FOR LIGHT-ACTIVATED ANTIBACTERIAL APPLICATIONS
Helin Hivda Yıldırım
Materials Science and Nano Engineering, MSc Thesis, 2026
Thesis Jury
Asst. Prof. Serap Hayat Soytaş (Thesis Advisor)
Assoc. Prof. Hayriye Ünal (Thesis Co-Advisor)
Prof. Fevzi Çakmak Cebeci
Asst. Prof. Serkan Ünal
Asst. Prof. Merve Senem Seven
Date & Time: June 11th, 2026 – 10:00 AM
Place: FENS 2019
Keywords: Lignin, Hydrogels, Electrospun nanofibers, Photothermal antibacterial therapy, Near-infrared responsive materials
Abstract
Lignin, the second most abundant biopolymer on Earth, is mostly used in low-value applications or disposed of as waste despite its promising photothermal conversion capability. Motivated by this potential, this thesis explores lignin-containing material systems that generate localized heat under light irradiation to achieve antibacterial activity. In the first study, lignin-based hydrogels with a novel formulation were prepared through the physical crosslinking of lignin with poly(vinyl alcohol) (PVA), using Ca2+ ions as a secondary crosslinking agent. The resulting hydrogels exhibited strong photothermal conversion and achieved more than 99.9% antibacterial activity against Staphylococcus aureus (S. aureus) after 5 min of irradiation with an 808 nm near-infrared (NIR) laser at 0.8 W/cm2. In the second study, lignin was incorporated into polyacrylonitrile (PAN) nanofibers to produce electrospun nanofibrous mats for air filtration. These mats also showed over 99.9% antibacterial activity against S. aureus within 20 min of 840 nm NIR LED exposure at 0.2 W/cm2, effectively filtered various aerosol particles, and achieved 99.99% filtration efficiency against S. aureus bioaerosols while maintaining an acceptable pressure drop. Collectively, these results demonstrate the potential of lignin as a sustainable and naturally derived photothermal agent for light-activated antibacterial materials.