Hydrothermal-assisted crystallization for the synthesis of upconversion nanoparticles/CdS/TiO2 composite nanofibers by electrospinning

Abstract

Upconversion nanoparticles/semiconductor nanocomposites have received intense interest in the past two decades. In this work, we demonstrated a facile electrospinning technique and a hydrothermal-assisted crystallization process to fabricate upconversion nanoparticles (UCNPs)/CdS/TiO₂ nanofibers successfully. Polyvinylpyrrolidone (PVP, M_w ≈ 1 300 000) has been selected as the polymer matrix and tetrabutyl titanate (TBT, 99.0%) was used as the titanium source. The morphologies and phase of the as-prepared samples have been studied using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Experimental results revealed that the polymer matrix (PVP) can be dissolved and removed completely under hydrothermal conditions. In addition, the crystalline phase of TiO₂ was also achieved under hydrothermal conditions. The as-prepared composite nanofibers are hundreds of micrometers in length and 650 nm in diameter and show weak upconversion fluorescence under the excitation of near-infrared light (980 nm), indicating the high energy transfer efficiency between upconversion nanoparticles and semiconductors. As expected, the UCNPs/CdS/TiO₂ nanofibers may have enhanced photocatalytic performance as they make full use of solar energy using UCNPs as nanotransducers for infrared (IR) light.