Simple, Robust, and Plasticizer-Free Iodide-Selective Sensor Based on Copolymerized Triazole-Based Ionic Liquid

Novel solid-contact iodide-selective electrodes based on covalently attached 1,2,3 triazole ionic liquid (IL) were prepared and investigated in this study. Triazole-based IL moieties were synthesized using click chemistry and were further copolymerized with lauryl methacrylate via a simple one-step free radical polymerization to produce a "self-plasticized" copolymer. The mechanical properties of the copolymer are suitable for the fabrication of plasticizer-free ion-selective membrane electrodes. We demonstrate that covalently attached IL moieties provide adequate functionality to the ion-selective membrane, thus achieving a very simple, one-component sensing membrane. We also demonstrate that the presence of iodide as the counterion in the triazole moiety has direct influence on the membrane's functionality. Potentiometric experiments revealed that each electrode displays high selectivity toward iodide anions over a number of inorganic anions. Moreover, the inherent presence of the iodide in the membrane reduces the need for conditioning. The nonconditioned electrodes show strikingly similar response characteristics compared to the conditioned ones. The electrodes exhibited a near Nernstian behavior with a slope of -56.1 mV per decade across a large concentration range with lower detection limits found at approximately 6.3 × 10(-8) M or 8 ppb. These all-solid-state sensors were utilized for the selective potentiometric determination of iodide ions in artificial urine samples in the nanomolar concentration range

Circumventing Traditional Conditioning Protocols in Polymer Membrane-Based Ion-Selective Electrodes

Preparation of ion-selective electrodes (ISEs) often requires long and complicated conditioning protocols limiting their application as tools for in-field measurements. Herein, we eliminated the need for electrode conditioning by loading the membrane cocktail directly with primary ion solution. This proof of concept experiment was performed with iodide, silver, and sodium selective electrodes. The proposed methodology significantly shortened the preparation time of ISEs, yielding functional electrodes with submicromolar detection limits. Moreover, it is anticipated that this approach may form the basis for the development of miniaturized all-solid-state ion-selective electrodes for in situ measurements

Ion sensing pencil: Draw your own sensor

We demonstrate for the first time the concept of ion sensing pencil (ISP). The pencil’s lead carries chemical sensing functionality and is constructed by compression of graphite and zeolite, while the clutch is prepared by 3D printing. The ISP can be used to draw a chemical sensor by simple abrasion onto a hydrophobic surface. The ISP can be stored at home, used immediately off-the-shelf without any handling prior to measurements. It’s simple preparation, handling, and measuring protocols offer the possibility of integration into large scale sensor networks or to be offered to the general public for use at home using readout devices already present at many homes. We demonstrate the chemical functionality of ISP by producing 14 ISPs prepared by compression of graphite and one of 14 different zeolites individually in 60:40 wt%. These ISPs are then used to draw electrodes which were characterized in analogy to ion-selective electrodes. The ISP-drawn electrodes were utilized as a multi-sensor array for the determination of water quality in a model sample, which is a first reported case of using zeolite-based electrodes in multisystem arrays, followed by the demonstration of their potential to be used by non-trained personnel. The implementation ISPs in potentiometric detection holds promise for further development of inexpensive and accessible tools for obtaining chemical information in areas where utilization of chemical sensors is currently limited