This study reports the synthesis of a novel graphene/chitosan/β-cyclodextrin composite material (GO/CS/β-CD) via a onestep chemical reduction method, which combines the advantages of graphene, chitosan, and β-cyclodextrin. The morphology and structure of the composite were characterized using various techniques, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Subsequently, sortase A (SA) was immobilized onto the GO/CS/β-CD for the detection of Staphylococcus aureus. The sensor exhibited a good linear relationship within the concentration range of 30–300 CFU/mL, with a detection limit of 12 CFU/mL. The GO/CS/β-CD composite material showed enhanced properties due to the synergistic effect of graphene, chitosan, and β-cyclodextrin. The immobilization of sortase A onto the composite material improved the sensitivity and selectivity of the sensor for the detection of S. aureus. This study presents a novel graphene/chitosan/β-cyclodextrin composite material with immobilized sortase A, demonstrating enhanced sensitivity and selectivity for the detection of Staphylococcus aureus, which has potential for the development of high-performance sensors in various fields.

Environmental pollution has become an alarming issue for the modern world due to the extensive release of untreated chemical waste into freshwater bodies. Untreated chemical waste poses significant negative impacts on aquatic life and human health. The phenolic compounds are widely used in different industries for dyeing, as food preservatives, and for the production of pesticides. 2,4,6-Trichlorophenol (TCP) is among the most hazardous phenolic compounds that cause several serious health effects. Thus, it is important to monitor TCP in the environmental samples frequently. In the current work, it was aimed to develop a highly sensitive zinc oxide-doped (ZnO) reduce graphene oxide (rGO) composite-based electrochemical sensor for TCP monitoring in the real samples. In this regard, graphene oxide (GO) was simultaneously reduced and doped with ZnO using a facile microwave-assisted synthesis strategy. The resulting ZnO/rGO composite was successfully utilized to fabricate ZnO/rGO-modified glassy carbon electrode (ZnO/rGO/GCE) for the selective and trace level determination of TCP. The conductivity and electrocatalytic behaviors of ZnO/rGO/GCE were examined through different modes of electrochemical setup. Under the optimal operating conditions such as a scan rate of 80 mV.s−1, PBS electrolyte (pH 7.0), and the concentration range of 0.01–80 μM, the fabricated electrochemical sensor manifested outstanding responses for monitoring TCP. The limit of detection (LOD) and limit of quantification (LOQ) of the ZnO/rGO/GCE for TCP were found as 0.0067 μM and 0.019 μM, respectively. Moreover, the anti-interference profile and stable nature of ZnO/rGO/GCE made the suggested electrochemical sensor a superb tool for quantifying TCP in a real matrix.

In this research, reduced graphene oxide/polypyrrole (rGO/PPy) particles were synthesized and used to measure the amount of dopamine (DA) electrochemically. The obtained rGO/PPy particle was characterized by Fourier Transform Infrared Spectrophotometer (FTIR), UV–Visible Spectrophotometer (UV–Vis), and X-Ray Diffraction Diffractometry (XRD). To investigate the DA sensor performance, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to acquire electrochemical measurements of the sensor. Current values of 1.65 and 5.9 mA were observed in the CV at 0.2 mM and 1.2 mM concentrations of target molecule, respectively. Under optimized conditions, the linear calibration plots were found to exhibit significant sensitivity in the linear range of 0.2 and 1.2 mM, with a corresponding detection limit of 0.061 μM for DA. The results obtained were similar to the sensor results of DA made using precious metals. This work was a demonstration of the feasibility of high-sensitivity electrochemical analysis with conductive carbon materials without the use of precious metals. It was also observed that the cost-effective rGO/PPy exhibited a very high potential for DA detection.

The electrochemical type gas sensor has the advantage of being easy to use due its small size, and it is also relatively inexpensive. However, its output can easily vary depending on temperature and humidity conditions. Therefore, it is important to ascertain the exact output characteristics of a sensor according to the measuring environment in order to improve measurement accuracy for any set of given conditions. The purpose of this study is to obtain basic information about the output characteristics of a sensor that is used both indoor and outdoor according to the variation in temperature and humidity conditions in order to improve the accuracy of the sensor. To achieve this result, a calibration curve was made using ammonia standard gas and the calibration factor was calculated using the calibration curve and the measuring accuracy was confirmed with regard to the ammonia sensor. Based on the test results, the variation of the sensor output value was large in relation to temperature and humidity variation. It was found that the output value from the sensor at higher temperature and humidity conditions was also higher. However, the measuring accuracy of the sensor could be improved by more than 10% by applying the calibration factor and an average accuracy of more than 97% could be achieved. It is anticipated that the result of this study can be used as basic data to obtain more accurate results using electrochemical sensors for a given set of temperature and humidity conditions, and therefore, it can also be considered that the reliability and applicability of electrochemical sensors can be improved.