A potentiometric glucose biosensor based on immobilization of glucose oxidase (GOD) on ZnO nanorods (ZnO-NRs) has been developed for the indirect determination of environmental mercury ions. The ZnO-NRs were grown on a gold coated glass substrate by using the low temperature aqueous chemical growth (ACG) approach. Glucose oxidase in conjunction with a chitosan membrane and a glutaraldehyde (GA) were immobilized on the surface of the ZnO-NRs using a simple physical adsorption method and then used as a potentiometric working electrode. The potential response of the biosensor between the working electrode and an Ag/AgCl reference electrode was measured in a 1mM phosphate buffer solution (PBS). The detection limit of the mercury ion sensor was found to be 0.5 nM. The experimental results provide two linear ranges of the inhibition from 0.5 × 10⁻⁶ mM to 0.5 × 10⁻⁴ mM, and from 0.5 × 10⁻⁴ mM to 20 mM of mercury ion for fixed 1 mM of glucose concentration in the solution. The linear range of the inhibition from 10⁻³ mM to 6 mM of mercury ion was also acquired for a fixed 10 mM of glucose concentration. The working electrode can be reactivated by more than 70% after inhibition by simply dipping the used electrode in a 10 mM PBS solution for 7 min. The electrodes retained their original enzyme activity by about 90% for more than three weeks. The response to mercury ions was highly sensitive, selective, stable, reproducible, and interference resistant, and exhibits a fast response time. The developed glucose biosensor has a great potential for detection of mercury with several advantages such as being inexpensive, requiring minimum hardware and being suitable for unskilled users.

In this study, we have successfully demonstrated the fabrication of a biosensor based on well aligned single-crystal zinc oxide (ZnO) nanorods which were grown on gold coated glass substrate using a low temperature aqueous chemical growth (ACG) method. The ZnO nanorods were immobilized with penicillinase enzyme using the physical adsorption approach in combination with N-5-azido-2-nitrobenzoyloxysuccinimide (ANB-NOS) as cross linking molecules. The potentiometric response of the sensor configuration revealed good linearity over a large logarithmic concentration range from 100 µM to 100 mM. During the investigations, the proposed sensor showed a good stability with high sensitivity of ~121 mV/decade for sensing of penicillin. A quick electrochemical response of less than 5 s with a good selectivity, repeatability, reproducibility and a negligible response to common interferents such as Na¹⁺, K¹⁺, d-glucose, l-glucose, ascorbic acid, uric acid, urea, sucrose, lactose, glycine, penicilloic acid and cephalosporins, was observed.

We have successfully synthesized Fe‐doped ZnO nanorods by a new and simple method in which the adopted approach is by using ammonia as a continuous source of OH⁻ for hydrolysis instead of hexamethylenetetramine (HMT). The energy dispersive X‐ray (EDX) spectra revealed that the Fe peaks were presented in the grown Fe‐doped ZnO nanorods samples and the X‐ray photoelectron spectroscopy (XPS) results suggested that Fe³⁺ is incorporated into the ZnO lattice. Structural characterization indicated that the Fe‐doped ZnO nanorods grow along the c‐axis with a hexagonal wurtzite structure and have single crystalline nature without any secondary phases or clusters of FeO or Fe₃O₄ observed in the samples. The Fe‐doped ZnO nanorods showed room temperature (300 K) ferromagnetic magnetization versus field (M‐H) hysteresis and the magnetization increases from 2.5 μemu to 9.1 μemu for Zn_0.99Fe_0.01O and Zn_0.95Fe_0.05O, respectively. Moreover, the fabricated Au/Fe‐doped ZnO Schottky diode based UV photodetector achieved 2.33 A/W of responsivity and 5 s of time response. Compared to other Au/ZnO nanorods Schottky devices, the presented responsivity is an improvement by a factor of 3.9.