Year: 2025
Type: dissertation
Abstract: Blue upconverter (UC) crystals, when incorporated into biophotonic scaffolds, can present a promising approach for biomedical applications like drug release, tissue regeneration. In this work, CaWO4: (Yb3+/Tm3+/Nd3+) crystals, prepared using a solid-state reaction, were found to emit blue light under 808nm and 980nm excitation. The role of Nd3+in this emission is discussed. The blue emission intensity from Tm3+ in Yb3+/Tm3+/Nd3+ triply doped CaWO4 under 808 nm pumping was achieved through Nd3+ sensitization with Yb3+ ions, facilitating energy transfer, whereas the blue emission under 980nm was only due to Yb3+ activating Tm3+. The UC crystals-Persistent Luminescent (PeL) phosphors ratio was optimized to achieve the best optical performance: long-lasting green emission after 808 and 980 nm charging. The porous bio-photonic scaffold, fabricated using the robocasting method, consisted of UC crystal, PeL phosphor SrAl2O4: Eu2+, Dy3+, and bioactive glass 1393B20. The printability of the scaffolds by using a 3D printer is also discussed. Upon 808nm excitation, scaffolds lose their green after-glow but still emit blue emission. However, at 980nm, it shows intense blue emission with strong green afterglow. Here, the challenges related to the fabrication of these composites are discussed. The elevation of sample temperature influenced by laser irradiation is suspected to depend on the doping concentration of Nd3+ and the excitation power density of the 808nm pump laser. The printability of the composite ink into biophotonic scaffolds has been proven, opening a new perspective in smart photoactivable materials for photo-induced drug release within bone tissue engineering.
Author: Chowdhury, Pinky
Institution: Tampere University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7133016259