Aggregation-induced emission (AIE), conceptually coined by Prof. Ben Zhong Tang in 2001, refers to a unique photophysical phenomenon non- or weakly emissive luminogens in dilute solutions emit intensely upon aggregation. AIE can solve the aggregation-caused quenching problem that traditional fluorophores are suffering from and hold great technological values for practical applications. The past 20 years have witnessed the rapid development of AIE research, from the restriction of intramolecular rotations to restriction of intramolecular motions, and from AIE to aggregate science, and many original results have been achieved. In this review, we summarize the advances in the field of AIE and its related areas. We specifically discuss the recent progress in AIE area, including material classification, mechanism, concept derivation, property, applications, and challenges. It is hoped that this review will inspire more research into the molecular aggregate level and make significant advances in materials, chemistry and biological sciences.

As one of the most important renewable chemicals, aromatic compounds are closely related to human production and life. Increasing concerns about diminishing oil resources and the relevant environmental pollution have gradually motivated interests in exploring new green chemistry routes towards aromatic hydrocarbons synthesis. Prized for the low cost and molecular diversity, biomass-derived furans arise as vital candidate raw materials for the production of aromatic compounds in the new century. Through Diels-Alder cycloaddition and the subsequent dehydration, furans could react with enophiles (such as ethylene and propylene) to obtain value-added aromatics including para-xylene. To our knowledge there exist broad industrial application prospects and economic benefits, and the catalytic reation of biomass-derived furans can effectively utilize renewable, abundant, sustainable energy. However, most of the reported catalytic conversion requires elevated temperature and high pressure, and the one-pot method usually results in multifarious and unrestricted side effects, such as hydrolysis, alkylation, isomerization and oligomerization. In this review, we summarize recent developments in the research achievements and issues of aromatic synthesis based on different biomass-derived furan molecules. The mechanism of Diels-Alder cycloaddition reaction is briefly introduced, followed by its influencing factors: catalyst composition, solvent effect and enophile. Then, perspectives and challenges for biomass-based aromatic synthesis are discussed.

Photocatalytic CO₂ reduction for fuel production has attracted much attention due to its potential for simultaneously solving energy and global warming problems. As a molecular catalyst, earth-abundant and eco-friendly iron complexes take the advantages of adjustable structure, rich valence, and easy synthesis, exhibiting good CO₂ photocatalytic reduction performance, and hence have attracted much attention in the field of CO₂ photocatalytic reduction. This review focuses on the recent progress in photocatalytic reduction of CO₂ based on iron complexes. First, the homogeneous photocatalytic CO₂ reduction systems using iron complex as catalyst, including iron porphyrin, iron polypyridine and iron pentadentate complex, are summarized. Visible-light-driven CO₂ reduction system is generally composed of three basic components: photosensitizer for absorption of visible light, catalyst for catalytic reduction of CO₂, and sacrificial electron donors for providing electrons in reduction reaction. Beyond catalytic efficiency, CO₂ photoreduction is a multi-electron transfer process boosted by the catalysts and inevitable competition with hydrogen evolution is a general issue for molecular catalysis of the CO₂-to-CO conversion, therefore the selectivity of the products is an important indicator. The selectivity and efficiency could be tuned by changing the ligand of iron complex, photosensitizer and sacrificial electron donors. Moreover, the mechanisms for the homogeneous photocatalytic CO₂ reduction, including catalyst activation and reduction process, are deciphered in detail. Second, the recent works of heterogeneous catalytic systems, which combine semiconductor nanomaterials/quantum dots with metal iron complexes as catalysts, are introduced. Considering the superior stability and fairly strong light absorption capacity of inorganic materials to the organic counterparts, the solid nanomaterials can be used as the photosensitizers to incorporate with the molecular catalysts. At the end, the current issues and perspectives on photocatalytic reduction of CO₂ based on iron complexes are discussed. For examples, porphyrin metal organic frameworks become a new research interest, and the design and construction of iron porphyrin metal organic frameworks is a promising way for getting new photocatalytic systems functioning in aqueous conditions. Besides, further efforts could be made on the mechanistic studies, especially the 8e^-/8H⁺ reduction to methane.

Isobutanol is an important compound with widespread applications in chemistry and the energy sector. Isobutanol synthesis from coal or biomass syngas is highly suitable to resource conditions in China, which has plenty of coal but little oil. Zn-Cr based catalysts have been widely used to produce isobutanol because of their long lifetimes and simple product distribution. This mini review highlights recent progress in syngas-based isobutanol synthesis and addresses the crucial role of cation distribution in non-stoichiometric spinel-structure Zn-Cr catalysts for this process. The development of catalysts for isobutanol synthesis is first summarized in terms of catalyst category, preparation methods, and generation mechanism. Some strategies for aggravating cation distribution disorder are then introduced, including adjusting the Zn/Cr ratio and/or annealing temperature, preparation methods, loading with a K promoter, and the use of excess ZnO. Two quantitative methods for obtaining information on cation distribution in Zn-Cr-based catalysts are introduced, i.e., Rietveld analysis for powder X-ray diffraction patterns and multiple-edge refinement for Zn K-edge extended X-ray absorption fine structure spectra. Isobutanol production shows a linear relationship to the degree of cation disorder because cation distribution affects the physicochemical properties of spinel-structure Zn-Cr catalysts, such as particle size, alkalinity, CO adsorption ability, and the state of surface oxygen. Finally, further development and the challenges associated with the synthesis of isobutanol are discussed.

As a hot robot research direction, soft robots have potential applications in many fields, such as the operation of small objects in limited space, due to the advantages including many degrees of freedom, excellent adaptability and flexible contact. As a classical smart material, liquid crystal elastomers (LCEs) are very promising to be the suitable candidate for preparing the soft robots owing to the large and reversible shape deformations in response to external stimuli (heat, light, electric or magnetic field, humidity, etc.). Due to the changes of microscopic orders or molecular structures of uniaxial-aligned mesogens, the whole LCE materials can execute very large and reversible macroscopic actuation during the LC-to-isotropic phase transition process. At present, according to different driving modes, the research of LCE-based soft robots mainly focuses on the thermal-driven soft robots, light-driven soft robots, electro-driven soft robots, magnetic-driven soft robots and humidity-driven soft robots. This article reviews the developments of LCE-based soft robots, and also introduces the main different driving modes and related LCE-based soft robot systems in detail. Besides, the article further provides a view of prospective development in the future for LCE-based soft robots.

Tumor liquid biopsy achieves accurate diagnosis of disease by detecting biomarkers in the body fluids which are of great importance for early diagnosis and dynamic monitoring of malignant tumors and are essential biomarkers for liquid biopsies. Circulating tumor cells (CTC) are tumor cells released into the blood from tumor tissue, and extracellular vesicles (EV) are membrane vesicles secreted by cells. Both of them carry tumor molecular information and are closely related to tumor progression and metastasis. Nanomaterials are widely used to detect CTCs and EVs due to their high specific surface area, unique optical, electrical, magnetic and other physical and chemical characteristics that can improve the detection sensitivity and specificity. Nanomaterial-based detection of CTCs and EVs has provided important information for tumor formation, progression, metastasis, and treatment response, and holds great potential in the clinical application. This article reviewes the progress of nanotechnology in three aspects: specific recognition, efficient capture or isolation, and identification of CTC and EV. It includes the functionalization of recognition probes on the surface of nanomaterials to improve the detection specificity and the latest advances in capture and identification of nanomaterials and nanotechnology. It may provide information for the development of liquid biopsy nanotechnology by discussing the advantages and challenges of liquid biopsy technology based on functionalized nanomaterials.

The near-infrared window with a wavelength between 1000 and 1700 nm is usually called the second near-infrared (NIR-Ⅱ) window. In terms of biological imaging (fluorescence imaging, photoacoustic imaging, etc.), this window shows a strong attraction. Compared with traditional imaging in the visible light (400~700 nm) region and the first near-infrared (NIR-Ⅰ 700~900 nm) window, NIR-Ⅱ bioimaging provides the advantages of high resolution and deep penetration depth. However, most current "always-on" probes cannot achieve a higher signal-to-noise ratio. The imaging of tumor microenvironment-responsive smart drugs is only triggered in tumors, which can overcome this limitation. Therefore, the tumor microenvironment and the NIR-Ⅱ intelligent response probe should be fully combined, and the advantages of both will be fully utilized to improve the accurate diagnosis of tumors. This article reviews the latest research progress of activatable NIR-Ⅱ fluorescent probes in bioimaging from different pathological parameters, and presents views on the opportunities and challenges faced by this emerging field.

The novel coronavirus pneumonia epidemic (COVID-19) brings a serious threat to the development of human society and the health of human beings. Due to the stability of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in urban sewage, which has become one of the virus pollution sources, it has been a focus how to eliminate the existing virus in water. SARS-CoV-2 structurally consists of RNA chains and protein capsids, and thus can be inactivated via reactive oxygen species (ROS) attack. Moreover, block of biochemical metabolism and destruction of virus structure are also effective inactivation methods for SARS-CoV-2 inactivation. Nanomaterials exhibit surface and interface effects, specific microstructure and excellent physicochemical properties, implying their high application potential in SARS-CoV-2 inactivation. In this study, we overall review application of nanotechnologies for SARS-CoV-2 inactivation, including photocatalysis, heterogeneous catalytic oxidation, ion toxicity induced inactivation, and structural effects inactivation method. Furthermore, based on the structural composition, as well as survival and transmission characteristics of SARS-CoV-2 in water environment, the application potential of various nanotechnologies for SARS-CoV-2 inactivation are deeply discussed. This study can provide a theoretical basis and practical reference for the application of nanotechnology for the SARS-CoV-2 inactivation and the secondary transmission interruption in water.

Halobenzoquinones (HBQs) are a class of toxic intermediates of the haloaromatic persistent organic pollutants and newly identified chlorination disinfection byproducts in drinking water and swimming pool water. The highly reactive hydroxyl/alkoxyl radicals and quinone enoxy/ketoxy radicals were found to be produced by HBQs with H₂O₂ or organic hydroperoxides metal-independently. However, it remains unknown whether HBQs and hydroperoxides can induce DNA damage, and if so, what are the underlying molecular mechanisms. We found that 8-oxodeoxyguanosine (8-oxodG), DNA strand breaks and three methyl oxidation products could be generated from DNA oxidation by tetrachloro-1,4-benzoquinone (TCBQ) and H₂O₂ via an intercalation-enhanced oxidation mechanism. Analogous effects were observed with other HBQs, which are generally more effective than the classic iron-mediated Fenton system. Further investigations were extended from isolated DNA to genomic DNA in living cells. Potent oxidation of DNA to the more mutagenic imidazolone dIz was also found to be induced by HBQs and organic hydroperoxides such as the physiologically-relevant hydroperoxide 13S-hydroperoxy-9Z,11E-octadecadienoic acid (13-HPODE) via a unique quinone-enoxy radical-mediated mechanism. These findings should provide new perspectives to explain the potential genotoxicity, mutagenesis, and carcinogenicity for the ubiquitously-present haloaromatic persistent organic pollutants.