Development of sensing platforms using bulk optode technique for detection of silver and mercury ions

Abstract

This research described�new analytical devices for Ag+ and Hg2+ detection using bulk optode technique. The optode containing 25,27-di(benzothiazolyl)-26,28-hydroxycalix[4]arene (CU1) as an ion-selective ionophore, chromoionophore XIV as a lipophilic pH indicator, and KTpClPB as an ion-exchanger was prepared and used as a sensing agent in the proposed devices. The optode sensors responded to Ag+ and Hg2+ by changing the color from blue to yellow. The colorimetric-based detection was carried out by using the proposed paper-based analytical device. A simple fabrication method was performed by simply dropping the cocktail onto the filter paper, and the detection method was easily performed by immersing the paper strip into the sample solutions. �In this platform, the dual detection of Ag+ and Hg2+ in their mixed solutions was achieved by adding EDTA and NaCl as masking agents, respectively. Additionally, to demonstrate a truly instrument-free optode sensor without the need of any electronic equipment, the distance-based detection was proposed by using the thread-based analytical device. The optode nanosphere with 110 nm in diameters was successfully prepared and incorporated onto the surface of polyester thread by a simple manual pipetting, and the detection method was easily performed by repeatedly dropped sample solutions onto the thread. In this platform, the Hg2+ detection on thread-based device was exhibited. The distances of the color change correlated to the Hg2+ concentrations in sample solutions, so the detection method was easily performed by measuring the length of the color change along the thread with a ruler. Finally, the proposed devices were successfully applied to determine the amount of Ag+ and Hg2+ in real samples, and the results were in agreement with the values obtained from ICP-OES.