Cancer cells that shed from solid tumor and circulate into bloodstream, namely circulating tumor cells(CTCs), are closely related to tumor metastasis. Therefore, CTCs detection is of great significance for cancer diagnosis, treatment monitoring, disease assessment and understanding of the mechanisms underlying tumor metastasis. However, CTCs are extraordinarily rare, heterogeneous, nonuniform in blood. Even if strategies for detection of CTCs in static blood collected from patients have made significant progress, they still face the tumor cell loss, cell death, low fidelity, and low sensitivity. It is essential to develop approaches available for detection of tumor cells in fast-flowing blood, allowing real-time monitoring of CTC dynamic changes under physiological conditions. In this review, we summarize techniques developed for CTC detection in vivo and their related applications. Furthermore, the advantages and disadvantages of these techniques are analyzed. Finally, future techniques for detection of CTCs in vivo are discussed and predicted.

Viruses are one of the biggest threats to human health, and the outbreak of viral diseases not only poses a great threat to human health and national security, but also causes great losses to the social economy. Uncovering the mechanisms of virus infection is crucial for preventing the spread of viruses and treating viral diseases. The dynamic process of virus infection in host cells involves intricate interactions between viral components and cellular structures or organelles, but conventional methods lack the ability to acquire dynamic information on individual viruses during the infection process. Single-virus tracking(SVT) technique is a powerful approach for studying the real-time and in-situ dynamics of viral processes in live cells and it plays an increasingly important role in the study of viral infection mechanism. SVT allows researchers to obtain the dynamic information on individual viruses during the infection process, including viral entry, trafficking, and genome release, which is meaningful to study the infection mechanisms on the molecular level. In this article, we first discuss the measurement techniques, viral labeling strategies and data analysis methods for SVT, then summarize a couple of applications of SVT and finally propose the challenges and future possibilities of the SVT technique.

Metal-organic frameworks(MOFs) are a class of crystalline porous materials formed by self-assembly of metal ions or clusters and organic ligands through coordination bonds. Due to the high porosity and functional designability, MOFs have found wide applications of which make them widely used in various fields. However, most traditional MOFs have poor conductivity, which severely restricts their development in electrical related fields. In recent years, electrically conductive MOFs, especially two dimensional electrically conductive MOFs(2D ECMOFs), have attracted a great deal of research attention due to their semiconducting or metallic properties closely-related to their unique π-π stacking and π-d conjugation structures, which have great application potentials in electrical and energy related fields such as sensors, electronics, electrocatalysts, batteries, and supercapacitors. In this review, the recent progress in conducting mechanisms, structures, synthesis strategies and applications of 2D ECMOFs are summarized and highlighted. Furthermore, future challenges and opportunities based on the current research status are prospected.

The enzyme-like activity of nanozymes is an emerging effect of nanomaterials. Due to the excellent physicochemical properties and unique enzyme-like activities, nanozymes have become promising functional nanomaterials. Till now nanozymes have been used in biomedical sensing, diagnosis and therapeutics, as well as environment protection. Despite of the great success achieved in the past several decades, how to efficiently design nanozymes is still one of the bottlenecks in the field, which is originated from the complicated composition and ambiguity in the active sites of nanomaterials. To tackle these challenges, this insight first summarizes the current efficient design strategies of nanozymes, such as computation-aided high throughput screening, rational design, and biomimetic design. And then, the development of bio-inspired metal-organic framework(MOF) nanozymes, particularly the structure-activity relationship study, is highlighted. At the end, combined with current research trend, several directions and inspirations for the future study are suggested to advance the nanozymes research.

Fluorescence imaging has a promising application prospect in clinical tumor tracing and intraoperative navigation, by virtue of its simple operation, high resolution, safety and real-time imaging. Though there are no targeted fluorescent probes clinically approved yet, a great number of targeted fluorescent probes are indeed under clinical trials. The very first ones are fluorescent dyes conjugated with tumor-targeting ligands, such as tumor-specific antibodies labeled with near-infrared(NIR) cyanine dye(IRDye800CW) and fluorescein isothiocyanate labeled with folic acid(EC17). In recent years, more complicated fluorescent probes, such as activatable probes and PET/fluorescent dual-modal imaging probes, have gradually entered clinical trials. Based on the latest research progress of fluorescent probes for intraoperative navigation, this review discusses receptor-mediated targeted fluorescent probes, activatable targeted fluorescent probes, NIR-Ⅱ fluorescent probes, multimodal fluorescent probes and theranostic fluorescent probes, with an emphasis on analyzing and summarizing the molecular design principles of fluorescent probes which are undergoing clinical evaluation or with the potential of clinical translation. At last, the future perspectives of fluorescent probes for intraoperative navigation are prospected.

H₂O₂ is widely used in the fields of chemical industry and environmental protection. The only product of its decomposition is water, which is environmentally friendly and conducive to the coordinated and sustainable development of production. The industrial synthesis of H₂O₂ is mainly indirectly through the anthraquinone method, which consumes a lot of energy and pollutes the environment. The preparation of H₂O₂ directly from the mixture of H₂ and O₂ has great safety risks and requires a large amount of H₂. The method of converting O₂ and H₂O into H₂O₂ through photocatalytic technology avoids the direct mixing of H₂ and O₂, and uses endless solar energy as an energy source, which has attracted much attention in recent years. This article summarizes the research progress of photocatalytic reduction of O₂ to H₂O₂, compares and analyzes the reaction performance and control measures of different catalytic systems, such as g-C₃N₄, TiO₂, and other photocatalysts, and the mechanisms of photocatalytic preparation of H₂O₂. In the end, the development of this field is prospected.

Actuating droplets for various dynamic behaviors has significant applications in the fields of biomedicine, microfluidics, and trace detection. The droplet movement depends on the adjustment of the forces on different positions of the droplets. Droplet self-propulsion based on heterogeneous surfaces shows advantages such as easy operation and energy conversation, which has been one of the research hotspots in droplet propulsion. In this article, recent research of droplet propulsion based on heterogeneous surfaces is reviewed. Firstly, the general principle of droplet self-propulsion based on surface heterogeneity is discussed. According to the different preparation methods, heterogeneous surfaces are divided into three categories: the heterogeneous wettability surface, the anisotropic structure surface and the synergistic surface. Their fabrications and applications are summarized, respectively. Finally, the limitations and the developments of heterogeneous surface are prospected and discussed.

Secondary ion mass spectrometry(SIMS), as the highest spatial resolution mass spectrometry imaging technique, holds label-free, high sensitivity, multi-component detection advantages and sub-micron high spatial resolution imaging advantage, providing new analysis method to study life science problems. SIMS has been widely used in cell biology, tissue pathological physiology, biological medicine, clinical medicine and other fields. This paper reviews the progress of SIMS imaging in biological tissue, cell, bionic biofilm and other bio-samples.

During the past years, metal complexes have attracted intensive research interest in biological sensors and imaging of cellular dynamics during a series of biological events. This is due to their unique advantages includes the following:(1) easily tunable chemical and photophysical properties resulting from their synthetic versatility;(2) high emission quantum yields and long phosphorescence lifetimes, which may avoid interferences from background auto-fluorescence;(3) large Stokes shifts for effective discrimination of excitation and emission wavelengths, as well as prevention of fluorescence quenching induced by self-absorption, and(4) emissive properties that are sensitive to subtle changes in the local environment. In recent years, metal complexes with obvious two-photon absorption have been attracted extensive attention in luminescence detection of biomolecules and organelle dyes because of their superior depth resolution and low light damage compared with traditional one-photon absorption. This review describes the latest two-photon absorption metal complexes with detection of biomolecules(pH, O₂, HClO, NO, SO₂, GSH, DNA, and so on) for diagnosis of diseases, as well as organelle probes(mitochondria, lysosomes, lipid droplets, nucleus, and so on) for intracellular dynamic behaviors and evolution processes. Finally, the perspectives of metal complexes in application of biomolecular probes and organelle dyes were analyzed and discussed.

The all-solid secondary lithium batteries are characteristic of high energy density and high safety. Combining the high flexibility of the polymer electrolytes and the high mechanical strength and high Li-ion transference number of the ceramic electrolytes, the ceramic-polymer composite solid electrolytes with high ceramic contents(HCC) are expected to find applications prior to the other solid electrolytes in the all-solid secondary lithium batteries. Following a brief introduction on the composite solid electrolytes, the recent advances of the HCC ceramic-polymer composite electrolyte are reviewed in the general performances of the composite electrolytes, the fabrications of their membranes, the ceramic-polymer interfacial interactions and the resultant new ionic transport mechanisms. At the end of this review, we prospect the fundamental and applicable issues that the HCC composite electrolytes have to meet and propose the future research directions and possible solutions to these questions. We wish that this review could be of help for the R&D of the composite solid electrolytes of other ions as well.

The all-inorganic perovskite solar cells(PSCs) have attracted much attention because of their good thermal stability, high carrier mobility and excellent compatibility with tandem devices. With the in-depth study of all-inorganic PSCs and continuous optimization of the fabrication process, the power conversion efficiency of all-inorganic PSCs have exceeded 19%. However, the phase stability of all-inorganic perovskite materials is relatively poor, therefore, the preparation and long-term application of all-inorganic PSCs in the air environment still faces great challenges. By analyzing the phase transition mechanism of all-inorganic perovskite, many researchers have proposed various methods including additive engineering, interface engineering and the development of all-inorganic perovskite quantum dot solar cells to improve their long-term stability. This review summarizes the research progress of all-inorganic PSCs in recent years from the aspects of all-inorganic perovskite materials and structure of solar cells, the fabrication method of the active layer and its phase stability.

Reactive gaseous mercury(RGM), also known as gaseous oxidized mercury, dominates atmospheric mercury deposition and is critical to the global cycle of mercury. This review introduces various sampling and analysis methods of RGM in detail, and discusses the advantages and limitations of the current techniques. The environmental processes including the formation, occurrence, and depletion of RGM in the atmosphere and related mechanisms are reviewed, and the contribution of each process in the atmospheric mercury cycle is explored. In view of the current analytical difficulties of RGM(e.g., ultralow concentration and sampling problems) and key scientific issues(e.g., chemical form and transformation) in the RGM research, efforts should be made to develop the feasible methods for RGM collection and speciation determinatiton in the real environment, so as to further explore its environmental behavior. This is challenging but important for the research of atmospheric mercury and will be helpful for understanding the role of RGM in cycle processes of atmospheric mercury.