Green optical dissolved oxygen sensor based on a chlorophyll–zinc complex extracted from the plant Brassica oleracea L

Abstract

In this study, we present the development of a green and high-sensitivity optical dissolved oxygen (DO) sensor for measuring DO in water using spectrofluorimetry. For the development of the sensor element, an organometallic complex was synthesized from the “chlorophyll A” molecule, extracted from the plant Brassica oleracea L., with zinc insertion (Zn+2) replacing the magnesium (Mg+2). In the investigation, we evaluated the fluorescence suppression of the organometallic zinc complex for samples with different concentrations of DO. The complex has shown two absorption regions, 350–475 nm and 600–700 nm. We observed the fluorescence suppression of the complex, when excited at 440 nm and analyzed at 635 nm, by using the spinning oxygenation and air pump flow methods, respectively. The fluorescence suppression curves presented first-order decay with good correlation, resulting in R2=0.98282 and R2=0.83849 for the spinning and air pump flow methods, respectively. To validate the methodology, we developed a prototype of a bench sensor. For the relation between the fluorescence intensity and oxygenation time, we obtained a ratio curve with R2=0.9809. The methodology and prototype sensor developed in this work are presented as a new optical method for the measurement of DO.