The fabrication, characterization and application of nanostructured zinc oxide (ZnO) thin films on interdigitated silver electrodes
were described for the determination of phosphate buffer saline (PBS) concentration. The ZnO thin films were synthesized on a
silicon dioxide wafer using a sol-gel spin coating technique. Two different seed solutions were prepared by dissolving Zn-acetate dihydrate
in methanol and isopropanol in presence of a stabilizer, monoethanolamine. The field emission scanning electron microscope,
atomic force microscope, X-ray diffractometer and Fourier transform infrared characterization revealed the presence of hexagonal ZnO
nano-crystals in all thin films. However, the smaller sized and homogeneous ZnO nano-crystals were observed in isopropanol derived
thin films. These thin films were used to discriminate the concentrations of different PBS solutions and the discriminatory signals were
captured using a low-cost dielectric analyzer and a source meter. The frequency-capacitance curve reflected 2.85 fold increase in capacitance
values when the sensor was exposed to 1000-fold diluted PBS in deionized water. A change in PBS concentration from 1000 fold
to 10 fold increased the current flow from 6uF to 122uF. Thus the capacitance and current flow demonstrated a proportional relationship
with the concentration of PBS, suggesting the application of the fabricated sensor in the determination and discrimination of chemicalspecies
concentration in various solutions.
Keywords: Interdigitated electrodes, Sol-gel spin coating technique, Dielectric analyzer and source meter, I-V curve, Double layer capacitance.
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