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Reliable and nondestructive monitoring of food quality is of great importance in sustaining life and promoting good health. Herein, we developed sensitive, fast, reversible, and nanometer-thick fluorescent films for the nondestructive evaluation of fish freshness. The nanofilms were prepared via the dynamic condensation of tetraphenylethylene derivative (TPEBA) with Calix[4]-pyrrole derivative (CPTH) at the humid air/DMSO interface. The amorphous nanofilm is uniform with the thickness in the range of 12∼58 nm. Owing to the aggregation-induced emission (AIE) property of TPEBA, the nanofilm is highly emissive with a Stokes shift of ∼175 nm. The typically designed chemical composition and nanostructure endow the film-preferable affinity to amine vapors, and the networked structure allows fast mass transfer, which lays foundation for high-performance sensing. With an optimized nanofilm-based sensor, biogenetic amines were sensitively, selectively, and reversibly detected. The detection limit (DL) for trimethylamine (TMA) is 0.89 ppm. Typically, interference from water can be neglected; thus, the nondestructive evaluation of fish freshness was realized. Moreover, a portable seafood freshness detector was conceptually built. [ABSTRACT FROM AUTHOR]

A siliconnanowires (SiNWs)-based fluorescent sensor for complexedCu2+was realized. High sensitivity and selectivity ofthe present sensor facilitate its bioapplications. The sensor wassuccessfully used to detect the Cu2+in liver extract.Meanwhile, real-time and in situ monitoring of Cu2+releasedfrom apoptotic HeLa cell was performed using the as-prepared SiNWarrays-based sensor. These results indicate that the present SiNWs-basedsensor would be of potential applications in revealing the physiologicaland pathological roles of Cu2+. [ABSTRACT FROM AUTHOR]

Although it is widely used in industry and food products, formic acid can be dangerous owing to its corrosive properties. Accurate determination of formic acid would not only benefit its qualified uses but also be an effective way to avoid corrosion or injury from inhalation, swallowing, or touching. Herein, we present a nanofilm-based fluorescent sensor for formic acid vapor detection with a wide response range, fast response speed, and high sensitivity and selectivity. The nanofilm was synthesized at a humid air/dimethyl sulfoxide (DMSO) interface through dynamic covalent condensation between two typically designed building blocks, de- tert -butyl calix[4]arene-tetrahydrazide (CATH) and 4,4',4″,4‴-(ethene-1,1,2,2-tetrayl)tetra-benzaldehyde (ETBA). The as-prepared nanofilm is uniform, flexible, fluorescent, and photochemically stable. The thickness and fluorescence intensity of the nanofilm can be facilely adjusted by varying the concentration of the building blocks and the sensing performance of the nanofilm can be optimized accordingly. Based on the nanofilm, a fluorescent sensor with a wide response range (4.4 ppt-4400 ppm) for real-time and online detection of formic acid vapor was built. With the sensor, a trace amount (0.01%) of formic acid in petroleum ether (60-90 °C) can be detected within 3 s. Besides, fluorescence quenching of the nanofilm by formic acid vapor can be visualized. It is believed that the sensor based on the nanofilm would find real-life applications in corrosion and injury prevention from formic acid.

Portable, miniaturized, and inexpensive detectors are in high demand for detecting and discriminating volatile organic compounds (VOCs). Sensor array design and exploitation are two key issues for new detector development. In contrast to the most reported plane-shaped sensor array for gaseous analyte sensing, here we report a column-shaped fluorometric sensor array by using fluorophore-loaded silica particles (∼40 μm) filled capillary. In the design, the capillary serves as test chamber and facilitates visualization. The orifices of the capillary were used as inlet and outlet for gaseous analyte. Sensing modules are installed in series, which lays foundation for their even and effective contact with the gaseous analyte. Meanwhile, further capsulation could be avoided. Silica particles were chosen as carries due to their preferred adsorption behavior to VOCs. By choosing four typical fluorophores (PBI-CB, Py-CB-Ph, Py-At, and NA-Ch) as sensing units, a 4-element fluorometric sensor array was achieved. Fluorescence of the array varied when different alcohol vapors were pumped in. The six tested alcohols could not only be distinguished as primary, secondary, or tertiary, but also be identified individually. The array had good reproducibility in visualization of the six alcohols. In addition, the orders of the fluorophores can be changed as desired. It is believed that the proofed concept provides not only a totally new design of sensor array but also contributes a new strategy for the discrimination of the alcohols as examined.

Low-molecular-mass organic gelator (LMOG)-based molecular gels are known as one of the most attractive soft materials and have received great attention since the early 1990s. In the last few decades, many LMOGs have been synthesized, and a series of theories have been proposed to better understand molecular gels. However, only limited applications of LMOGs have been realized for a variety of reasons, such as their lack of stability compared to chemical gels. Therefore, efforts to explore the applications of these materials are especially meaningful. As an example, this feature article mainly introduces studies on the application of LMOGs as intermediates in porous materials and fluorescent sensing films. Particular attention will be paid to gelator design, LMOG emulsion preparation, solid surface modification, and the practical application of the obtained materials. Concepts that are related to these studies, such as organic gel-water interface equilibria and molecular gel strategies, will be comprehensively illustrated. Finally, we will conclude with a study of LMOG-based intermediates. Some challenges and future perspectives related to these research areas will also be presented. It is anticipated that this feature article will not only contribute to the further understanding of LMOG-based intermediates but also will help to promote the practical application of molecular gels and facilitate development in related research areas.

The supramolecular approach plays a pivotal role in the construction of smart and functional materials due to the reversible nature of noncovalent interactions. In the present work, two compounds, cholesterol-functionalized calix[4]pyrrole (CCP) and perylene bisimide diacid (PDA), were synthesized. Little fluorescence is observed in the ethanol solution of the mixture of CCP and PDA, while the solution turns fluorescent upon introduction of ammonia, which is attributed to the formation of a supramolecular ensemble, PDA/(CCP) 2 /NH 3 . The fluorescence emission of the as-formed ensemble is sensitive to the presence of phenol, an electron-rich analyte. Interestingly, the sensing can also be observed in the film state, and the relevant detection limit (DL) is lower than 1 ppb. Moreover, the sensing could also be performed in a visualized manner. Upon the basis of the findings, a sensor device with instant response and good reversibility was developed. Further studies revealed that the as-developed fluorescent ensemble is also sensitive to the presence of TNT, an electron-poor compound. The DL for this sensing is ∼80 nM. To our knowledge, this is the first report that a fluorescent sensor could be used for phenol sensing in the vapor state, and for sensing of both electron-rich and electron-poor analytes in solution state. It is believed that the present study presents a distinctive example that demonstrates how smart sensing is realized via combination of the host-guest chemistry of calix[4]pyrrole and the aggregation and disaggregation property of PBI derivatives.

A novel, facile, and effective method for modification of SiNWs or SiNW arrays has been developed. In this method, reaction between reductive Si-H bonds on the surface of SiNWs and the aldehyde group containing in organic molecules has been used for immobilization of organic molecules onto the surface of SiNW arrays. The method is time saving and can be operated at room temperature without any other complex reaction requirement. Fluorescence images, XPS, fluorescence spectra, and IR spectra were used for characterization of the modification. Through this method, a SiNW array-based pH sensitive chip was realized by covalently immobilizing 5-aminofluorescein molecules onto the surface of SiNW arrays with glutaraldehyde as linker molecules. Fluorescence intensity of the chip increased with increasing of pH value and a linear relationship between fluorescence intensity and pH values was acquired. In addition, the chip has been successfully used for real-time and in situ monitoring of extracellular pH changes for live HeLa cells and the result exhibited fine resolution of time and space.