Humans are fundamentally interested in monitoring and understanding interactions that occur in and around our bodies. Biological interactions within the body determine our physical condition and can be used to improve medical treatments and develop new drugs. Daily life involves contact with numerous chemicals, ranging from household elements, naturally occurring scents from common plants and animals, and industrial agents. Many chemicals cause adverse health and environmental effects and require regulation to prevent pollution. Chemical detection is critically important for food and environmental quality control efforts, medical diagnostics, and detection of explosives. Thus, sensitive devices are needed for detecting and discriminating chemical and biological samples. Compared to other sensing devices, the Quartz Crystal Microbalance (QCM) is well-established and has been considered and sufficiently sensitive for detecting molecules, chemicals, polymers, and biological assemblies. Due to its simplicity and low cost, the QCM sensor has potential applications in analytical chemistry, surface chemistry, biochemistry, environmental science, and other disciplines. QCM detection measures resonate frequency changes generated by the quartz crystal sensor when covered with a thin film or liquid. The quartz crystal is sandwiched between two metal (typically gold) electrodes. Functionalizing the electrode’s surface further enhances frequency change detection through to interactions between the sensor and the targeted material. These sensors are sensitive to high frequencies and can recognize ultrasmall masses. This review will cover advancements in QCM sensor technologies, highlighting in-sensor and real-time analysis. QCM-based sensor function is dictated by the coating material. We present various high-sensitivity coating techniques that use this novel sensor design. Then, we briefly review available measurement parameters and technological interventions that will inform future QCM research. Lastly, we examine QCM’s theory and application to enhance our understanding of relevant electrical components and concepts.

Fine-tuning of the morphology from two-dimensional (2D) to three-dimensional (3D) nanostructures by structural engineering leads to improved biosensing. Herein, a 3D assembly of MXene and rGO nanosheets was synthesized by a hydrothermal process, and then, a naturally abundant and promising biosensing catalyst of Cu2O was added by a coprecipitation method to prepare a 3D ternary composite (MXene graphene aerogel–Cu2O composite). The prepared ternary nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and Brunauer–Emmett–Teller (BET). It exhibited a low crystallite size, spherical-shaped Cu2O, and a large surface area with a porous structure. Further, a sensing electrode was fabricated by the drop-casting method, and then, a chronoamperometric (CA) study was performed to understand the sensing performance of the 3D ternary composite. The fabricated electrode showed sensitivities of 264.52 and 137.95 μA cm–2 mM–1 compared to 2D composites (126.6 μA cm–2 mM–1) with two wide linear ranges of 0.1–14 and 15–40 mM, respectively. The electrode also gave a low detection limit and good stability, selectivity, and reproducibility, thus making it suitable for the determination of glucose levels in human serum samples. These findings reveal that the 3D network of MXene and rGO nanosheets assists in effective charge transfer and promotes the sensing activity of nonenzymatic glucose sensors.

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This study generally relates to nuclear sensors and specifically to detecting nuclear and electromagnetic radiation using an ultrasensitive quartz tuning fork (QTF) sensor. We aim to detect low doses of gamma radiation with fast response time using QTF. Three different types of QTFs (uncoated and gold coated) were used in this study in order to investigate their sensitivity to gamma radiations. Our results show that a thick gold coating on QTF can enhance the quality factor and increase the resonance frequency from 32.7 to 32.9 kHz as compared to uncoated QTF. The results also show that increasing the surface area of the gold coating on the QTF can significantly enhance the sensitivity of the QTF to radiation. We investigated the properties of gold-coated and uncoated QTFs before and after irradiation by scanning electron microscopy. We further investigated the optical properties of SiO2 wafers (quartz) by spectroscopic ellipsometry (SE). The SE studies revealed that even a small change in the microstructure of the material caused by gamma radiation would have an impact on mechanical properties of QTF, resulting in a shift in resonance frequency. Overall, the results of the experiments demonstrated the feasibility of using QTF sensors as an easy to use, low-cost, and sensitive radiation detector.

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