The Effects of Antimony Thin Film Thickness on Antimony pH Electrode Coated with Nafion Membrane

Abstract

A new antimony pH electrode by employing magnetron sputtering Sb thin film on copper substrates inlaying in printed circuit board (PCB) was developed. To improve the performance of the electrode, nafion membrane was employed as an alternative modification layer. The layer was formed simply by drop casting 5 wt% nafion solutions and drying the resultant coating. Further, the effect of the thickness of the Sb sensing thin film on the performance of antimony pH electrodes was investigated. Surface morphology, energy spectrum, and electrochemical experiments were conducted in Sb thin film thickness of ∼50, ∼150, ∼240, and ∼330 nm. Experimental results demonstrated excellent features of the pH electrodes with ∼240 nm thickness Sb thin film, including high sensitivity, short response time, high resolution, stability, reversibility, and long-term stability. The pH electrode is low cost, high performance, and simple preparation, is promising to popularize in laboratory and industrial production.As a typical electrochemical sensor, pH sensor has been received much attention in various fields, such as food spoilage monitoring, water pollution monitoring, soil pollution monitoring, biomedical sensing, industrial and chemical processing and structural health monitoring, where pH measurements are vital for the characterization of aqueous solutions. 1 Currently the most widely used technique for determination of pH in laboratory is the glass pH electrode. While the performance of the glass electrodes is excellent in terms of high sensitivity, long-term stability, high ion selectivity and wide operating range, such electrodes have many disadvantages including mechanical fragile, need for wet storage, large size, limited shape, high impedance and high cost. 2,3 Drawbacks of glass electrodes have led to intensive research for alternative pH electrodes. Potentiometric metal/metal oxide electrodes have proven to be some of the most promising candidates. 4 Various metals and metal oxides, such as Ti/TiO 2 , Zr/ZrO 2 , W/WO 3 , Ir/IrO 2 , Sb/Sb 2 O 3 , Ru/RuO 2 , and Pd/PdO, have been investigated for pH electrodes due to important attractive features, such as insolubility, mechanical strength, electro catalyst, stability, and manufacturing technology. 1,5-8 Among them, Ir/IrO 2 , Ru/RuO 2 , and Sb/Sb 2 O 3 have been popular research points recently. Some relative studies have been conducted in last decade.For Ir/IrO 2 , many groups tried to fabricate the iridium oxide electrode with some different manufacturing methods, for example, a novel melt-oxidized method, a new carbonate melt oxidation method, the electrodeposited method, the sol-gel fabrication process, and so on. 4,6,[9][10][11] For Ru/RuO 2 , Maurya et al. designed a miniaturized pH sensor employing an R. F. sputtered RuO 2 thin-film electrode in conjunction with an electroplated Ag/AgCl reference electrode, and some factors, such as temperature effects, Ar/O 2 flow ratio, and electrode thickness, were studied. The ruthenium oxide thin-film electrodes were applied in engin...

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