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.