Fabrication and Characterization of ZnO Thin Films by Sol-Gel Spin Coating Method for the Determination of Phosphate Buffer Saline Concentration

Abstract: The fabrication, characterization and application of nanostructured zinc oxide (ZnO) thin films on interdigitated silver elec-trodes 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 dihy-drate 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 capaci-tance 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 chemical-species concentration in various solutions