The detection of ultralow or nonvolatile target analytes remains a significant challenge for artificial olfactory systems even after decades of development, which severely limits their widespread application. To overcome this challenge, an artificial olfactory system based on a colorimetric hydrogel array is constructed for the first time as a universal representative. As an effective extension of conventional artificial olfactory systems that integrates the merits of its predecessors, the proposed system accurately mimics olfactory mucosa and specific odorant binding proteins using hydrogels endowed with specific colorimetric reagents for the detection of hypochlorite, chlorate, perchlorate, urea, and nitrate. Therefore, the proposed system is capable of detecting and discriminating between these five airborne improvised explosive microparticulates with a detection limit as low as 39.4 pg. Additionally, the system demonstrates good reusability over ten cycles, rapid response time of ≈0.2 s, and excellent discrimination properties, despite significant variation. This proof‐of‐concept study on colorimetric artificial olfactory systems yields a novel strategy for the direct and discriminative detection of nonvolatile airborne microparticulates.

The precise regulation of fluorophore binding sites in an organic probe is of great significance toward the design of fluorescent sensing materials with specific functions. In this study, a probe with specific fluorescence properties and nitrite detection ability is designed by precisely modulating benzothiazole binding sites. Only the fluorophore bond at the ortho-position of the aniline moiety can specifically recognize nitrite, which ensures that the reaction products displays a robust green emission. The unique 2-(2-amino-4-carboxyphenyl) benzothiazole (ortho-BT) shows superior nitrite detection performance, including a low detection limit (2.2 fg), rapid detection time (<5 s), and excellent specificity even in the presence of >40 types of strong redox active, colored substances, nitro compounds, and metal ions. Moreover, the probe is highly applicable for the rapid on-site and semiquantitative measurement of nitrite. The proposed probe design strategy is expected to start a new frontier for the exploration of probe design methodology.

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Naphthalene-based poly(arylene ether ketone)s with pendant sulfoalkyl groups were prepared by a demethylation and sulfobutylation method. They exhibited high proton conductivity, low methanol permeability and high thermal stability.

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Although a set of functional molecules with the D-π-A structure has been explored as optical probes for the detection of target analytes, it remains a great challenge to elaborately design a single probe for distinguishing different analytes by their intrinsic oxidation or reduction capabilities and thus to generate distinct optical responses. Here, a unique TCF-based probe (DMA-CN) containing two unsaturated double bonds in the π-conjugation bridge and TCF with different reaction activities that could be cut off by KMnO4 and NaClO in varying degrees was developed, causing remarkably distinguishable responses for both fluorescence and colorimetric channels to discriminate KMnO4 and NaClO from each other. The fluorescence and colorimetric limits of detection (LODs) of the proposed DMA-CN toward KMnO4 were calculated as 60 and 91 nM, respectively, while those for NaClO were 13.3 and 214 nM, and all the optical signal change can be observed within 1 s with good specificity. Based on the proposed probe design strategy, a well-fabricated test strip was proven to be promising for the rapid, in-field detection and risk management. We expect that the present probe design methodology would provide a powerful strategy for efficient probe exploration, especially for discriminating the substances with similar oxidizing properties.

To understand the underlying fundamental mechanism affecting the optical sensitivity of a paper‐based substrate, a layered polyvinyl alcohol (PVA) network paper is proposed considering the physical geometry and chemical composition required to enhance the sensitivity. It is verified both theoretically and experimentally that the dimension confinement effect introduced by the Steiner network, layered and pore structures, as well as massive hydroxyl groups, play an essential role in enhancing the concentration signal on the surface. Trace chlorate droplets and particles are considered representative examples to prove the excellent structural design‐induced performance of the PVA network paper. A practical mass detection from potassium chlorate solution and particles could be as low as 9.9 pg and 0.34 fg, respectively, and the corresponding naked‐eye observation limit could reach 0.69 ng and 1.6 pg, respectively, assuming the distinguishable size for human eyes is 100 µm. Further, the detection time could be far less than 2 s, which is remarkably superior than the detection performance of the parallel filter paper counterpart. The dimension confinement effect demonstrated here is expected to be of great importance for advancing the development of paper‐based trace detection.