Dual imaging of topography and photosynthetic activity of a single protoplast by scanning electrochemical microscopy

Two types (A and B; see Figure 1 in the text) of dual-Pt microdisk electrod es (disk radius, 0.5-4.0 mu m; whole tip radius, 5.0-15 mu m) were fabricat ed to simultaneously detect two electroactive species near a single algal p rotoplast (radius, 25 mu m). At the tip of type A, the two disks were on th e same plane. Two disk planes of electrode type B formed an angle of simila r to 135 degrees at the tip. Cyclic voltammetric investigation indicated th at, compared with type At one disk in type B only slightly collected the sp ecies electrogenerated at the other disk. These dual-microdisk electrodes w ere applied to electrochemical measurements of a single protoplast in artif icial seawater. The topographic profiles Of the single protoplast were obta ined from the variation of oxidation current for 1.0 mM Fe(CN)(6)(4-) at on e disk. The photosynthetic oxygen generation from the protoplast was also m onitored by detecting the reduction current for oxygen at another disk. The electrode of type B was used as a probe for scanning electrochemical micro scopy (SECM) to obtain dual-SECM images of topography and activity of a sin gle protoplast.