Grey level replaces fluorescent intensity: Fluorescent paper sensor based on ZnO nanoparticles for quantitative detection of Cu2+ without photoluminescence spectrometer

Abstract

This work uses ZnO nanoparticles as the probe and a case, proving that the grey level can replace fluorescent intensity to realize a quantitative detection function of paper-based Cu2+ sensor. Portable Cu2+ test papers were obtained through dipping filter papers in as-prepared ZnO sol possessing the Cu2+ quenching property. Based on grey level which is obtained through ordinary digital camera and computer, the detection function of the fabricated Cu2+ test paper is extended from qualitative detection relied on naked eyes to quantitative detection whose detection range is calculated to be 10–1000μM. The fabricated test papers also could resist the interruption of some competing ions and is a potential candidate for portable Cu2+ detection device with quantitative function. Since the strategy of replacing fluorescence intensity by grey level is based on the map relationship between the fluorescence intensity and the digital signal (grey level), it is promising to be applied to other fluorescent test papers to gain quantitative test papers aimed at corresponding chemicals. At the same time, the mechanism of Cu2+-induced fluorescence quenching was also investigated by fluorescence lifetime, UV–vis spectra, and photoluminescence spectra. And a static quenching mechanism based on the non-fluorescence complex formed by Cu2+ and Ox− is brought up.