Nanozymes are a kind of nanomaterial mimicking enzyme catalytic activity, which has aroused extensive interest in the fields of biosensors, biomedicine, and climate and ecosystems management. However, due to the complexity of structures and composition of nanozymes, atomic scale active centers have been extensively investigated, which helps with in-depth understanding of the nature of the biocatalysis. Single atom nanozymes (SANs) cannot only significantly enhance the activity of nanozymes but also effectively improve the selectivity of nanozymes owing to the characteristics of simple and adjustable coordination environment and have been becoming the brightest star in the nanozyme spectrum. The SANs based sensors have also been widely investigated due to their definite structural features, which can be helpful to study the catalytic mechanism and provide ways to improve catalytic activity. This perspective presents a comprehensive understanding on the advances and challenges on SANs based sensors. The catalytic mechanisms of SANs and then the sensing application from the perspectives of sensing technology and sensor construction are thoroughly analyzed. Finally, the major challenges, potential future research directions, and prospects for further research on SANs based sensors are also proposed.

Hydrogels have gained the attention of researchers worldwide and can be widely applied for use in medical technologies in human health and in industrial applications such as robotics. However, producing a hydrogel with proper mechanical properties, low hysteresis energy, quick shape recovery, and long-range strain sensitivity is still an ongoing development. More development into hydrogel technology could also lead to an increase in the effectiveness and lifespan of artificial joint replacements. Our hydrogels can be incorporated into the development of highly sensitive strain sensors for wearable electronic devices. To work toward developing these technologies, multifunctional dual crosslinked hydrogels were developed using lauryl methacrylate, acrylamide, and acid-functionalized multiwalled carbon nanotubes (A-MWCNTs). Due to the dual crosslinking, the synthesized hydrogels display outstanding mechanical performance (high fracture stress, strain, toughness, and tensile strength). In shape recovery, the materials recover their original shape after compression and maintain hydrostaticity. A low hysteresis energy of 11.57 kJ m −3 makes it a suitable candidate for strain sensing with high sensitivity (GF = 9.2 at 500% strain) to monitor different human motions (wrist, neck movements, flexion of the fingers, swallowing, and during speaking). Additionally, due to its good mechanical properties, the cyclic stability was monitored up to 300 cycles and the hydrogel still was mechanically stable and had the fastest response−recovery time of less than 130 ms during mechanical performance studies. Our hydrogels can be used to develop highly sensitive strain sensors for wearable electronic devices.

Halide solid electrolytes (SEs) stand out among the many different types of SEs owing to their high ionic conductivity and excellent oxidative stability. Aliovalent substitution is a common strategy to enhance the ionic conductivity of halide electrolytes, but this strategy significantly decreases their electrochemical stability. Herein, we report Hf-substituted Li 3 InCl 6 (Li 3−x In 1−x Hf x Cl 6 , 0 ≤ x ≤ 0.7) SEs, in which a low concentration (0.1 ≤ x ≤ 0.5) of Hf enhances the ionic conductivity without affecting the electrochemical stability. Among them, Li 2.7 In 0.7 Hf 0.3 Cl 6 exhibits a high ionic conductivity of 1.28 mS cm −1 and a wide electrochemical stability window of 2.68−4.22 V. All-solid-state batteries fabricated using Li 2.7 In 0.7 Hf 0.3 Cl 6 SE present high discharge capacity and good cycling stability at 25 °C. Furthermore, we summarize the methods of crystal structure regulation by which aliovalent substitution of halide SEs is achieved and discuss potential research directions in the design of novel halide SEs with high ionic conductivity and electrochemical stability.

Natural enzymes are crucial in biological systems and widely used in biology and medicine, but their disadvantages, such as insufficient stability and high-cost, have limited their wide application. Since Fe3O4 nanoparticles were found to show peroxidase-like activity, researchers have designed and developed a growing number of nanozymes that mimic the activity of natural enzymes. Nanozymes can compensate for the defects of natural enzymes and show higher stability with lower cost. Iron, a nontoxic and low-cost transition metal, has been used to synthesize a variety of iron-based nanozymes with unique structural and physicochemical properties to obtain different enzymes mimicking catalytic properties. In this perspective, catalytic mechanisms, activity modulation, and their recent research progress in sensing, tumor therapy, and antibacterial and anti-inflammatory applications are systematically presented. The challenges and perspectives on the development of iron-based nanozymes are also analyzed and discussed.

Solid electrolytes are important materials for energy storage and conversion applications, and the coexistence of the paddle-wheel effect and vacancy diffusion mechanism is commonly observed in many solid electrolytes. However, the mechanism that significantly contributes to this remains unknown. To address this issue, we assess the phase stability and conduction properties of Na3SO4F (NSOF) and magnesium-doped NSOF (Na2.98Mg0.01SO4F, NMSOF). Our results reveal that incorporating Na vacancies in NSOF (i.e., NMSOF) leads to a significant increase in ionic conductivity, with a 2 order of magnitude difference compared to NSOF. The phase transition temperature of NMSOF is also significantly lower than that of NSOF, demonstrating the role of vacancies in enhancing the mobility of Na cations. Furthermore, Raman spectroscopy confirms that the polyanion SO4 2– rotation has a minor effect on the sodium conduction mechanism. Our study provides a fundamental understanding of the sodium conduction mechanism of polyanion-based sodium superionic conductors, including the impact of vacancies on Na conductivity.

Neurotransmitter exocytosis of living cells plays a vital role in neuroscience. However, the available amperometric technique with carbon fiber electrodes typically measures exocytotic events from one cell during one procedure, which requires professional operations and takes time to produce statistical results of multiple cells. Here, we develop a functionally collaborative nanostructure to directly measure the neurotransmitter dopamine (DA) exocytosis from living rat pheochromocytoma (PC12) cells. The functionally collaborative nanostructure is constructed of metal−organic framework (MOF)-on-nanowires-on-graphene oxide, which is highly sensitive to DA molecules and enables direct detection of neurotransmitter exocytosis. Using the microsensor, the exocytosis from PC12 cells pretreated with the desired drugs (e.g., anticoronavirus drug, antiflu drug, or anti-inflammatory drug) has been successfully measured. Our achievements demonstrate the feasibility of the functionally collaborative nanostructure in the realtime detection of exocytosis and the potential applicability in the highly efficient assessment of the modulation effects of medications on exocytosis.