Potentiometric biosensors based on flexible arrayed silver paste electrode and copper-doped zinc oxide sensing film modified by iron-platinum nanoparticles (FePt NPs) are designed and manufactured to detect lactate in human. The sensing film is made of copper-doped zinc oxide (CZO) by a radio frequency (RF) sputtering system, and then modified by iron-platinum nanoparticles (FePt NPs). The surface morphology of copper-doped zinc oxide (CZO) is analyzed by scanning electron microscope (SEM). FePt NPs are analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The average sensitivity, response time, and interference effect of the lactate biosensors are analyzed by voltage-time (V-T) measurement system. The electrochemical impedance is analyzed by electrochemical impedance spectroscopy (EIS). The average sensitivity and linearity over the concentration range 0.2–5 mM are 25.32 mV/mM and 0.977 mV/mM, respectively. The response time of the lactate biosensor is 16 s, with excellent selectivity.

In this study, we prepared a non-enzymatic potentiometric ascorbic acid sensor based on molybdenum oxide (MoO ₃ ) and copper nanoparticles (CuNPs). Also, we prepared a potentiometric sensor by monitoring the voltage change between the sensor and ascorbic acid, and proposed the reaction mechanism between molybdenum oxide and ascorbic acid. It is relatively rare in the field of non-enzymatic ascorbic acid sensors. Molybdenum oxide is a relatively new material applied in ascorbic acid sensors. The application of molybdenum oxide film and copper nanoparticles to ascorbic acid sensors is a new research direction. We employed screen printing technology to prepare reference electrodes and conductive wires on the polyethylene terephthalate (PET) substrate, and we also used epoxy for packaging. In the ascorbic acid concentration range of $7.81 ~\mu \text{M}$ -2 mM, we measured the characteristics of sensors with the voltage-time (V-T) measurement system, namely the average sensitivity, linearity, response time, interference effects, limit of detection (LOD), and temperature effects. The performance of the ascorbic acid sensor was significantly improved by the modification of CuNPs.

This study proposed a potentiometric non-enzymatic electrochemical sensor for glucose detection based on copper doped zinc oxide (CZO) as a sensing film. In this article, a metal oxide film was used, which was able to react catalytically with glucose. The wires of the sensor were prepared by screen printing technology, and the CZO thin film was deposited on the sensor by the radio frequency (R. F.) sputtering system. In order to make the non-enzymatic sensor more stable, Nafion layer was added to the working electrodes. The characteristics of the sensor were measured using a voltage time (V-T) measurement system. Average sensitivity and linearity of the Nafion/CZO glucose sensor was tested in glucose concentrations ranging from 2 mM - 14 mM. After experiment, it was confirmed that the sensor had good performance. Experiments confirmed that the Nafion/CZO sensor exhibited characteristics including: good selectivity for glucose, average sensitivity of 6.45 mV/mM, a linearity of 0.998, a response time of 20 sec, and a limit of detection (LOD) of 0.51 mM. The device has a low relative standard deviation (RSD) and would be suitable for further development and eventual use in biomedical applications.

A non-enzymatic copper-doped zinc oxide glucose sensor, which is covered with silver nanowires (AgNWs) and modified with Nafion, can be employed to measure glucose with a concentration of 2-14 mM. In this study, X-ray photoelectron spectroscopy (XPS) was used to analyze the film of the working electrodes, and the AgNWs on the electrode surface were analyzed by a field-emission scanning electron microscope (FE-SEM). Also, the AgNW/CZO structure was investigated through the use of an atomic force microscope (AFM) and an ultraviolet/visible (UV/Vis) spectrophotometer. Finally, we used electrochemical impedance spectroscopy (EIS) and the voltage-time (V-T) measurement system to measure the sensing characteristics of the thin film. The potentiometric non-enzymatic glucose sensor has the average sensitivity of 10.31 mV/mM, and the linearity is 0.997. Also, the sensor has the response time with 15 s, and the interference experiment proved that it has good anti-interference and excellent repeatability (relative standard deviation (RSD) = 3%). Besides, the sensor still maintains a certain degree of average sensitivity at high temperatures, and it has the limit of detection (LOD) with 0.272 mM.

In a previous study, this laboratory produced and tested a lactic acid biosensor using a copper-doped zinc oxide (CZO) sensing film modified with graphite carbon nitride (g-C ₃ N ₄ ) and iron platinum nanoparticles (FePt NPs). The previous sensor exhibited two non-ideal effects during persistent use and when alternating between high and low lactose concentrations. Using a low unity-gain frequency and low power consumption instrumentation amplifier (UGFPCIA) in conjunction with a calibration readout circuit, it was possible to reduce the previously observed drift and hysteresis effects. The UGFPCIA and calibration readout circuit were connected to a voltage-time (V-T) measurement system so the effects could be accurately quantified. The influence of the UGFPCIA on the measurement characteristics of the lactate biosensor were recorded and compared to a similar device using a commercial LT1167. Results showed that the UGFPCIA produced a more stable measurement, where linearity increased from 0.985 to 0.998. When measuring interference effects, the fluctuation in response voltage became smaller, and the time drift effect was successfully reduced by 89.7%. The hysteresis effect reduced the forward period by 0.13 mV, and the reverse period by 4.37 mV.

In this research, we proposed a potentiometric sensor based on copper doped zinc oxide (CZO) films to detect glucose. Silver nanowires were used to improve the sensor’s average sensitivity, and we used the low power consumption instrumentation amplifier (UGFPCIA) designed by our research group to measure the sensing characteristics of the sensor. It was proved that the sensor performs better when using this system. In order to observe the stability of the sensor, we also studied the influence of two kinds of non-ideal effects on the sensor, such as the drift effect and the hysteresis effect. For this reason, we chose to combine the calibration readout circuit with the voltage-time (V-T) measurement system to optimize the measurement environment and successfully reduced the instability of the sensor. The drift rate was reduced by about 51.1%, and the hysteresis rate was reduced by 13% and 28% at different measurement cycles. In addition, the characteristics of the sensor under dynamic conditions were also investigated, and it was found that the sensor has an average sensitivity of 13.71 mV/mM and the linearity of 0.998 at a flow rate of 5.6 μL/min.