Figure 4. Sensor's performance.

(a) Amperometric current response at +0.55 V with successive addition of different glucose concentrations including 25 μM (5 times, with magnified inset), 0.1 mM (9 times), 0.25 mM (5 times), and 1 mM (7 times), illustrated with the black curve. Amperometric response of the none-modified electrode (DLEG) with a negligible current response, green curve. (b) Calibration curve of the sensor. (c) The sensing linear range of the sensor as compared to physiological levels of glucose found in sweat, tear, saliva, and urine. (d) Selectivity experiment using amperometric current responses of sensor with successive addition of 0.25 mM glucose (twice), then 0.02 mM electroactive interfering species of AA, DA, UA, Lactose, Sucrose, Fructose, and 0.2 mM NaCl, and finally 1 mM glucose into 0.1 M NaOH at an applied potential of 0.55 V. (e) Reproducibility (3 sensors were compared) and stability (compared with the value of the first test) of the sensors 1, 2, and 3 stored at normal ambient conditions using 0.1 mM glucose in 100 mM NaOH at 0.55 v of applied potential, conducting repeating amperometric experiments every three days for a total of 10 times during one month.