In this invention, a mixture of a diazotizing reagent which reacts with nitrous ions to produce a diazo compound, a coupling reagent which couples with a diazo compound to produce {HEAD ~ an azo dye}, and an acid is placed in pores of a transparent porous body to prepare {TAIL ~ a sensor element} 
In this invention , a mixture of a diazotizing reagent which reacts with nitrous ions to produce a diazo compound , a coupling reagent which couples with a diazo compound to produce { HEAD ~ an azo dye } , and an acid is placed in pores of a transparent porous body to prepare { TAIL ~ a sensor element }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL