Oral Presentation 18th International Congress on Photobiology 2024

Harnessing, protecting from, and evaluating effects of UV radiation: Case studies of cellulose nanocrystals, nanodiamond-laden gels and biodegradable polymers (#149)

Saad Khan 1
  1. North Carolina State University, RALEIGH, NC, United States

UV radiation produces a wide range of effects with it being more readily known for its deleterious impact; however we can also utilize it to our advantage. In this presentation, we discuss three scenarios for UV radiation. In the first case, we discuss cases where UV radiation can be exploited to develop functional polymer gels and coatings. We discuss how UV curable coatings can be developed by understanding the effects of UV radiation on the rheology of polymers. In particular, we will explore the gelation of these systems as a function of UV radiation. Two systems of interest would be alginate- and cellulose nanocrystals (CNCs)-based materials. The sol-gel transition, evidence of dark curing, formation of percolating networks and gelation mechanism will be elucidated. In the second case, we discuss the use of nanodiamonds to protect us from UV radiation. NDs are carbon-based multifunctional nanomaterials that contain a sp3 hybridized core, a graphitic outer shell and multiple surface functional groups that can be readily tuned. The high refractive index of NDs promotes light scattering while the functional groups and graphitic shell absorb UV photons, allowing broad-spectrum UV filtering. In this case, we show how carboxylated nanodiamonds (cNDs) modulate the rheology and UV attenuation properties of polyacrylic acid (PAA) microgels through pH and concentration modulation. The unique aspects of our work lie in a) tunability of microgel rheology and lubrication, through controlled modulation of pH and cND concentration, b) an understanding of the underlying interaction mechanism of pH-tunable microstructural reinforcement, c) broad-spectrum, photostable UV protection by cNDs comparable to TiO2 , d) preservation of gel microstructure after prolonged UV irradiation, all of which leading to e) a safer formulation (e.g., for sunscreen and topical lotions) using multifunctional nanodiamonds. In the final case, we discuss how UV radiation affect polylactic acid (PLA) degradation. Our choice for PLA stems from its appeal to replace more traditional polymers. Approaches to measure PLA degradation under aerobic and anaerobic conditions following UV radiation, and possible mechanisms involved will be discussed.