Comparative spectroscopic study of Tb:Ce(Sal)₃Phen complex inhibited PVA nanofibres for flexible moisture sensor

In the present work, we report a systematic study on optical alteration in Tb:Ce(Sal)₃Phen, Tb(Sal)₃Phen complexes, and TbCl₃·6H₂O inhibited in polyvinyl alcohol (PVA) polymeric nanofibres. We also report the feasibility of Tb:Ce(Sal)₃Phen complex dispersed electrospun nanofibres for opto-humidity sensor. Structural, morphological, and spectroscopic properties of the synthesized nanofibres were systematically compared using Fourier transform infrared spectroscopy, scanning electron microscopy, and Photoluminescence analysis. Synthesized Tb(Sal)₃Phen complex inhibited in nanofibres yields characteristic bright green photoluminescence of Tb³⁺ under UV excitations, which is at least two manifolds enhanced on the addition of Ce³⁺ ions in the same complex. The presence of Ce³⁺ ions, the salicylate ligand, and the Tb³⁺ ion help to expand the absorption range (290 nm-400 nm) and, subsequently, the photoluminescence in blue and green regions. Our analysis revealed the linear enhancement of photoluminescence intensity with the addition of Ce³⁺ ions. Upon exposing the flexible Tb:Ce(Sal)₃Phen complex dispersed nanofibres mat in different humidity environments, photoluminescence intensity shows a linear variation. The prepared nanofibres film shows good reversibility, small hysteresis, cyclic stability, and acceptable response and recovery times i.e. 35 and 45 s. The humidity sensing mechanism was proposed on the basis of infrared absorption analysis of dry and humid nanofibres.