ELECTROCHROMIC SENSOR FOR HYDROGEN-PHOSPHATE ION WITH SPINEL-TYPE OXIDE-BASED THIN-FILM ELECTRODE

摘要

An electrochromic sensor for hydrogen-phosphate ion was developed with a spinel-type oxide-based thin-film electrode. The MnCo_2O_4 thin-film electrode exhibited a remarkable change of the absorbance at 500 nm, under a positive potential at +0.80 V vs. Ag/AgCl, which was dependent on HPO_4~(2-) concentration. The change of the absorbance at 500 nm, the sensor signal, was almost linear to the logarithm of HPO_4~(2-) concentration between 1.0x10~(-6) and 1.0x10~(-2) M. The 90% response time, when the electrode potential was changed from +0.80 to 0 V vs. Ag/AgCl at 1.0x10~(-2) M, was about 40 s at room temperature. The MnCo_2O_4-based element also showed high HPO_4~(2-) selectivity among the tested anions of HPO_4~(2-), Cl~-, NO_3~-, and SO_4~(2-).