Fabrication of Large-Area Multi-Stimulus Responsive Thin Films via Interfacially Confined Irreversible Katritzky Reaction.

Fabrication of large-area thin films through irreversible reactions remains a formidable task. This study reports a breakthrough strategy for in situ synthesis of large-area, free-standing, robust and multi-stimulus responsive thin films through a catalyst-free and irreversible Katritzky reaction at a liquid-liquid interface. The as resulted films are featured with adjustable thickness of 1-3 µm and an area up to 50 cm2. The thin films exhibit fast photo-mechanical motions (a response time of ca 0.1 s), vapor-mechanical motions, as well as photo-chromic and solvato-chromic behaviors. It was revealed that the reason behind the observable motions is proton transfer from the imine groups to the carbonyl structures within the film induced by photo- and/or dimethyl sulfoxide-stimulus. In addition, the films can harvest anionic radicals and the radicals as captured can be efficiently degraded under UV light illumination. This study provides a new strategy for fabricating smart thin films via interfacially confined irreversible Katritzky reaction.

Efficient Removal of Iodine from Water by a Calix[4]pyrrole-Based Nanofilm.

The efficient removal of radioactive iodine from an aqueous solution is largely dependent on the adsorbent materials employed. In this work, we report a calix[4]pyrrole-based nanofilm and its application for the rapid removal of iodine from water. The nanofilm was synthesized through a confined dynamic condensation of tetra hydrazide calix[4]pyrrole with 1,3,5-tri-(4-formylphenyl) aldehyde at the air/dimethyl sulfoxide (DMSO) interface. The thickness of the obtained nanofilm is ∼35 nm, enabling fast mass transfer and a high ratio of accessible binding sites for iodine. The pseudo-second-order rate constant of the nanofilm for iodine is ∼0.061 g g-1 min-1, 3 orders of magnitude higher than most reported adsorbent materials. Flow-through nanofiltration tests demonstrated that the nanofilm has an adsorption capacity of 1.48 g g-1, a high removal efficiency, and good reusability. The mechanism study revealed that the moieties of Schiff base, pyrrole, and aromatic rings play a key role for binding iodine. We believe this work provides not only a new strategy for the efficient removal of radioactive iodine from water but also new ideas for designing efficient iodine adsorbents.

Self-adhesive, surface adaptive, regenerable SERS substrates for in-situ detection of urea on bio-surfaces.

Wearable SERS substrates have gained substantial attention for health monitoring and other applications. Current designs often rely on conventional polymer substrates, leading to discomfort and complexity due to the need of additional adhesive layers. To address the issues, we fabricate a flexible, uniform, ultrathin, transparent and porous SERS substrate via depositing Ag nanoparticles (AgNPs) onto the CdS nanowires (CdSNWs) grown on the surface of a prepared nanofilm (AgNPs-CdSNWs/nanofilm). Unlike the wearable SERS substrates reported in literature, the one presented in this work is self-adhesive to a variety of surfaces, which simplifies structure, enhances comfort and improves performance. Importantly, the new SERS substrate as developed is highly stable and reusable. Artificial sample tests revealed that the substrate showed a great enhancement factor (EF) of 4.2 × 107 and achieved a remarkable detection limit (DL) of 1.0 × 10-14 M for rhodamine 6G (R6G), which are among the highest records observed in wearable SERS substrates reported in literature. Moreover, the substrate enables at real-time and in-situ reliable monitoring of urea dynamics in human sweat and plant leaves, indicating its applicability for health analysis and in precision agriculture.

Towards a scalable and controllable preparation of highly-uniform surface-enhanced Raman scattering substrates: Defect-free nanofilms as templates.

The uniformity and reproducibility of substrates highly determine the applicability of surface-enhanced Raman scattering (SERS). Production of them, however, remains a challenge. Herein, we report a template-based strategy for the strictly controllable and handily scalable preparation of a very uniform SERS substrate, Ag nanoparticles (AgNPs)/nanofilm, where the template used is a flexible, transparent, self-standing, defect-free and robust nanofilm. Importantly, the obtained AgNPs/nanofilm is self-adhesive to surfaces of different properties and morphologies, ensuring in-situ and at real-time SERS detection. The enhancement factor (EF) of the substrate for rhodamine 6G (R6G) could reach 5.8 × 1010 with a detection limit (DL) of 1.0 × 10-15 mol L-1. Moreover, 500 bending tests and one-month storage showed no observable performance degradation, and up to 50.0 cm2 scaled-up preparation depicted negligible effect upon the structure and the sensing performance. The real-life applicability of AgNPs/nanofilm was demonstrated by the sensitive detection of tetramethylthiuram disulfide on cherry tomato and fentanyl in methanol with a routine handheld Raman spectrometer. This work thus provides a reliable strategy for large area wet-chemical preparation of high-quality SERS substrates.

Large-area Free-standing Metalloporphyrin-based Covalent Organic Framework Films by Liquid-air Interfacial Polymerization for Oxygen Electrocatalysis.

Synthesizing large-area free-standing covalent organic framework (COF) films is of vital importance for their applications but is still a big challenge. Herein, we reported the synthesis of large metalloporphyrin-based COF films and their applications for oxygen electrocatalysis. The reaction of meso-benzohydrazide-substituted metal porphyrins with tris-aldehyde linkers afforded free-standing COF films at the liquid-air interface. These films can be scaled up to 3000 cm2 area and display great mechanical stability and structural integrity. Importantly, the Co-porphyrin-based films are efficient for electrocatalytic O2 reduction and evolution reactions. A flexible, all-solid-state Zn-air battery was assembled using the films and showed high performance with a charge-discharge voltage gap of 0.88 V at 1 mA cm-2 and high stability under bent conditions (0° to 180°). This work thus presents a strategy to synthesize functionalized COF films with high quality for uses in flexible electronics.

Interfacially confined preparation of copper Porphyrin-contained nanofilms towards High-performance Strain-Pressure monitoring.

The development of ultrasensitive, durable and anti-jamming strain-pressure sensors that can precisely distinguish different motions or deformations is crucial for health diagnosis and disaster monitoring, but it also remains a challenge. In this study, a self-standing, highly flexible and uniform nanofilm (CuPTFA) was fabricated via interfacial covalent condensation of a copper complex of 5,10,15,20-tetra(4-carboxyphenyl)-porphine tetrahydrizides (Cu-TPPNHNH2) and tris-(4-formylphenyl)-amine (TFA). The film was used as a sensing layer in a strain-pressure sensor with a sandwich-like structure of Au/I2@CuPTFA/Au. The sensor had a gauge factor exceeding 10000, a strain range of linear response of 3-7%, reliable output signals after 5000 times of continuous use, and extraordinary noise-screening capability. The strain-pressure sensor can differentiate moderate muscle hyper-spasm from subtle swaying, walking and vigorous sporting activities, with great potential for real-life applications.

Film Nanoarchitectonics of Pillar[5]arene for High-Performance Fluorescent Sensing: a Proof-of-Concept Study.

Substrates play crucial roles for the sensing performances of fluorescent films owing to their effect on the formation of a fluorescent adlayer. However, no such film has been developed through synthesizing a substrate with a defined structure. We herein report a kind of self-standing, uniform, and thickness tunable pillar[5]arene-based nanofilms to serve as substrates for fabricating fluorescent sensing films. In comparison with a glass plate, the pillar[5]arene-based nanofilms can ensure spatial and electronic isolation of immobilized fluorophores and circumvent aggregation-caused quenching in a film state. For conceptual proof, a formic acid fluorescent sensing film was developed through simple loading of a fluorophore, a 4-azetidine-1,8-naphthalimide derivative of cholesterol (NA-Ch), onto the prepared nanofilm. Sensing performance studies demonstrated that the fluorescent film showed a sensitive, fast, and highly selective response to formic acid in air with a detection limit of lower than 2.8 mg m-3 and a response time of less than 3 s. Moreover, the sensing is fully reversible and highly repeatable. Further studies showed that the film sensor can be used for fast determination of methanol acidity via vapor sampling. Clearly, innovation of substrates with defined structures can be taken as an effective and efficient way to develop new sensing films via combination with known fluorophores.

A robust, freeze-resistant and highly ion conductive ionogel electrolyte towards lithium metal batteries workable at -30 °C.

The wide applications of lithium metal batteries have encountered a severe conductivity issue when operating in cold weather. Here we report a freeze-resistant lithium metal battery, which displays outstanding rate performance, negligible polarization deterioration, and a good capacity retention of 94.25% after 700-cycles of use at -30 °C, the lowest temperature ever reported for gel electrolyte-based lithium metal batteries. Remarkably, the lithium metal batteries are even workable at temperatures down to -60 °C. The key point of the innovative design is the utilization of a newly created anti-freezing ionogel as an electrolyte, which is produced by gelation of an electrochemically inert ionic liquid, 1-butyl-3-methylimidazolium tetrafluoro-borate ([BMIM]BF4), via dynamic condensation of a specially designed benzaldehyde-terminated polyethylene glycol (PEG-CHOs) with the tetra-hydrazide derivative of p-tert-butyl-calix[4]arene (CTH). The as-prepared ionogel electrolyte demonstrates a high ionic conductivity (0.43 mS cm-1), a broad stability window (2.4-4.3 V vs. Li+/Li), and high flexibility at -30 °C. The outstanding property of the ionogel electrolyte is ascribed to its unique gel network structure as it enables enrichment of Li+ and enhances its efficient transportation. Further tests demonstrate that the ionogel electrolyte could be also used for the assembly of flexible lithium metal batteries.

Selective segmentation for global optimization of depth estimation in complex scenes.

This paper proposes a segmentation-based global optimization method for depth estimation. Firstly, for obtaining accurate matching cost, the original local stereo matching approach based on self-adapting matching window is integrated with two matching cost optimization strategies aiming at handling both borders and occlusion regions. Secondly, we employ a comprehensive smooth term to satisfy diverse smoothness request in real scene. Thirdly, a selective segmentation term is used for enforcing the plane trend constraints selectively on the corresponding segments to further improve the accuracy of depth results from object level. Experiments on the Middlebury image pairs show that the proposed global optimization approach is considerably competitive with other state-of-the-art matching approaches.