Tailoring optical properties and humidity sensing response of multilayered Tb(Sal)3Phen and Eu(DBM)3Phen complex nanofibres

Abstract

In this work, we investigate the opto-humidity sensing and colour tuning in polyvinyl alcohol (PVA) polymeric electrospun nanofibres dispersed with Tb(Sal)₃Phen (TSP) and Eu(DBM)₃Phen (EDP) complexes. Fourier transform infrared spectroscopy, scanning electron microscopy, and photoluminescence analysis were used to thoroughly analyse the structural, morphological, and spectroscopic features of the synthesised nanofibres in single and stacked multilayer nanofibres. A spectroscopic analysis was performed on all configuration schemes. Under UV excitations, the synthesised TSP complex and EDP complex inhibited nanofibres yield green and red emission corresponding to ⁵D₄→⁷F_j (j = 4, 5, 6) and ⁵D₀→⁷F_j (j = 0, 1, 2, 3) transitions attributed to Tb³⁺ and Eu³⁺ ions, respectively. The EDP nanofibres presented better UV radiation absorption than TSP, which was attributed to higher absorptivity of DBM than Sal. Additionally, the photoluminescence intensity ratio of characteristic emission peaks i.e. 544 nm (⁵D₄→⁷F₅)/615 nm (⁵D₀→⁷F₂) is function of humidity exposure and excitation wavelength. The stacked multilayer nanofibres exhibit good response and recovery times, 35 and 52 s, negligible hysteresis, and cyclic stability.