Grafting of terbium(iii) complexes onto layered rare-earth hydroxide nanosheets to fabricate novel optical fiber temperature sensors

Abstract

Optical sensors of temperature possess the unique advantages of contactless measurement and large-scale imaging. Developments have been rapidly made in optical fiber sensors due to their high sensitivity, short response time, and electromagnetic immunity, and being easy to handle and light weight. Therefore, novel optical sensors of temperature based on optical fibers were fabricated to explore their application in special environments, such as poisonous, sparkless, currentless, and gelid ones. The present study is the first report of successful intercalation of neutral Y(III) complexes in situ into the gallery of Y/Eu binary layered rare-earth hydroxides by hydrothermal processing without replacing the nitrate ions. The swollen layered rare-earth hydroxides were then exfoliated into ultrathin nanosheets ∼2 nm thick through dispersion in formamide. Grafting of Tb(III) complexes onto the exfoliated nanosheets yielded novel temperature sensor films <100 nm thick, which exhibited color emissions from green to pink tunable through temperatures ranging from 77 to 360 K under ultraviolet excitation. Due to the highly sensitive and temperature-dependent emission, an optical fiber-based temperature sensor was fabricated by employing these novel allochroic films, which showed luminescence that could reversibly undergo repeated thermocycles. These optical fiber sensors have the potential to open up new fields in material functionalities via nanostructure manipulation and functionalized optical fiber engineering.