Enhancing performance of optical sensor through the introduction of polystyrene and porous structures

Abstract

Simple and promising approaches for developing high-performance Fe3+ sensors were proposed. Polyvinyl chloride (PVC) membrane containing pyrene as a fluorescent indicator was prepared via solvent-cast method. Upon immersion into 1.0 mM Fe3+ solution, the fluorescence emission of the membrane decreased with the ratio of fluorescence intensities before and after (F0/F) immersion of 1.25. The sensitivity enhancement was achieved through the introduction of polystyrene (PS) onto PVC and the introduction of porous structures. Polyvinyl chloride-graft-polystyrene copolymers (PVC-g-PS) were synthesized via Atom Transfer Radical Polymerization using PVC as macroinitiator. The grafting percentages of PS on PVC calculated from Nuclear Magnetic Resonance Spectroscopy were 17 and 41. The membrane prepared from low molecular weight copolymer showed higher sensing ability than that from PVC with the F0/F value of 1.39. The increase in PS chain length did not significantly affect the fluorescence quenching. A Stern-Volmer quenching relationship was found with Ksv of 3.96 × 102 M-1. The effect of porous structures on fluorescence quenching was studied by introducing Triton X-100 as a porogen to PVC/pyrene solution. Attenuated total reflection Fourier transform infrared spectroscopy and Scanning Electron Microscopy analyses confirmed a complete removal of Triton X-100 after 3 days of immersion in water. The porous membrane demonstrated an enhanced sensing performance with the F0/F value of 1.46. PVC-g-PS/pyrene membrane exhibited highly sensitive and selective responses toward Fe3+ over Cu2+, Mg2+, Co2+, Zn2+, Ni2+, and Ag+. In addition, a good reversibility after five cycles of quenching and regeneration was obtained.