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Fig. 1. Schematic of the biosensor testing unit. (a) the modified YSI electrochemical chamber (reactor); (b) YSI sipper tube; (c) glassy carbon electrode (GCE); (d) Ag/AgCl reference electrode; (e) Pt wire auxiliary electrode is separately drawn, whose position on the chamber is marked. The body of the auxiliary electrode was vertical to the plane of the drawing paper and the Pt wire spring was immersed in the working solution; (f) the flowing direction for the flushed solution; (g) the stirring bar; (h) the organophosphorus hydrolase functionalized mesoporous silica (OPH-FMS) layer held on GCE by a Nafion gel. The three electrodes are connected with Autolab PSTAT12. The sipper tube is driven by a YSI mechanism system so that the sipper tube can descend into or ascend from the chamber, or rotate above the chamber. Thus, the samples can be injected into the chamber and the tested solution can be flushed by refilling the working buffer solution via the sipper tube.
