The significant in situ multicolored patterning without changing printing tools nor substrate media still remains challenging, especially toward practical applications for anti-counterfeiting. This research invented a unique universal approach for the laser-induced in situ synthesis of colorful fluorescent patterns (from blue: CIE 0.15, 0.18 to red orange: CIE 0.36, 0.39) through the controlled formation of N, S doped carbon dots (CDs) in solid composite polymer films or hydrogel with a hierarchical and physically unclonable microsurface architecture for anti-counterfeiting. The in situ patterning approach, coupled with multi-layer technique, yielding designable blue, yellow, orange, and red orange color under 365 nm in the same pattern. A 5 cm² colorful pattern can be efficiently finished within 5 min without changing the substrate and the line width accuracy can be up to 300 μm. The absolute quantum efficiency of the blue pattern reached as high as 23%. The fluorescent patterns can be survived at indoor for 24 months. The hydrogen bonding interactions between the CDs precursor and polymer facilitated the generation, uniform dispersion and stabilization of CDs during the laser irradiation. The hypothesis that laser irradiation induced photochemical reactions of CD precursors within a polymer matrix was supported by thermodynamic assessments. The universality of in situ fluorescent patterning strategy was demonstrated by developing fluorescent patterns on both solid polymer films, hydrogel, pharmaceutical packaging and textile.

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Photochromic smart windows have drawn increasing attention as an approach to improve building energy efficiency and enhance indoor daylight comfort. However, existing photochromic smart windows still block sunlight from entering the room on sunny winter days, causing additional energy consumption for heating. Herein, a dual-mode smart window is designed with decoupled photo and thermal functions by combining colorless Fe-doped WO3 photochromic film with window rotation. Based on this, selective heating and cooling of the room between winter and summer is achieved while maintaining the daylight comfort benefits during all seasons. As a proof of concept, the smart window reduces the temperature of a model house by up to 7.9 °C in summer mode, while in winter mode the temperature is only reduced by 0.7 °C. The proposed seasonally adaptive dual-mode smart window obtains by window rotation overcomes the limitations of conventional photochromic smart windows, which not only achieves better energy efficiency but also retains improved daylight comfort. Furthermore, it demonstrates that the heat absorbed by the smart window can be harnessed to produce electricity through the integration of thermoelectric modules within the glazing, which enhances its impact on reducing energy consumption.@en

The Fe₂P type Mn–Fe–P–Si alloys exhibit a giant magneto-elastic first-order transition, but the large hysteresis limits their performance. Crystal structure evolution and magnetocaloric performance were investigated by varying the Mn and Fe contents at a constant V substitution of 0.02 in Fe₂P-type (Mn_1.17-xFe_0.73-yV_0.02) (P_0.5Si_0.5) (where x + y = 0.02). The V substitution of Fe content shows a larger reduction of hysteresis compared with the same substitution amount of Mn content. During magnetoelastic phase transition, V-substitution reduces the volume change and the volumetric stresses, providing a superior mechanical stability. Compound with the V substitution of Fe (y = 0.02) shows the best magnetocaloric effect with a low thermal hysteresis of 0.6 K. Our developed Mn_1.17-xFe_0.73-yV_0.02P_0.5Si_0.5 alloys are excellent materials for room-temperature magnetic heat-pumping applications by using a permanent magnet.

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Inspired by the CO₂-induced reversible activation mechanism of the slow anion channel 1 (SLAC1) in plant stomatal guard cells during plant photosynthesis, we designed and prepared a CO₂- switchable H⁺/OH⁻ ion channel (CSPH ion channel). A high-performance chemiresistive room temperature CO₂ sensor has been prepared based on this CSPH ion channel. The obtained CO₂ room temperature sensor γ-CD-MOF@RhB exhibits high sensitivity (R_g/R₀ = 1.50, 100 ppm), excellent selectivity, good stability (less than 5% reduction in 30 days response value), and 99.96% consistency with commercial infrared CO₂ meter. The practical limit of detection (pLOD) of the γ-CD-MOF@RhB sensor reaches 10 ppm at room temperature toward CO₂, which is the lowest for reported MOF-derived chemiresistive room temperature CO₂ sensors so far. Ion conduction mechanism studies have shown that the CSPH ion channel behaves as a CO₂-switchable H⁺/OH⁻ ion channel with a switching point of approximately 60 000 ppm CO₂. As an application attempt, the fabricated low pLOD CO₂ sensor has been used for human exhaled CO₂ detection to compare CO₂ concentration in the breath of individuals before and after exercise and COVID-19. It was also logically indicated that the average concentration of human exhaled CO₂ after COVID-19 recovery is different for undiseased subjects.

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Constructing near-infrared light (NIR) light-enhanced room temperature gas sensors is becoming more promising for practical application. In this study, learning from the structure and photosynthetic process of chlorophyll thylakoid membranes in plants, the first “Thylakoid membrane” structural formaldehyde (HCHO) sensor is constructed by matching the upconversion emission of the lanthanide-doped upconversion nanoparticles (UCNPs) and the UV–vis adsorption of the as-prepared nanocomposites. The NIR-mediated sensor exhibits excellent performances, including ultra-high response (R_a / R_g = 2.22, 1 ppm), low practical limit of detection (50 ppb), reliable repeatability, high selectivity, and broadband spectral response. The practicality of the NIR-mediated gas sensor is confirmed through the remote and external stimulation test. A study of sensing mechanism demonstrates that it is the UCNPs-based light transducer produces more light-induced oxygen species for gas response in the process of non-radiative/radiative energy transfer, playing a key role in significantly improving the sensing properties of the sensor. The universality of NIR-mediated gas sensors based on UCNPs is verified using ZnO, In₂O_3, and SnO₂ systems. This work paves a way for fabricating high-performance NIR-mediated gas sensors and will expand the application fields of NIR light.

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Both temperature-responsive and patterned photonic coatings are receiving a lot of attention from a fundamental and application point of view. However, the fabrication of multicolor patterns, which are also temperature-responsive, remains challenging. The current work presents a thermochromic photonic coating with light polarization-dependent multiple structural colors from a polymer-stabilized cholesteric liquid crystal siloxane oligomer. It is found that the structural color and the temperature response can be manipulated by varying the polymerization temperature, allowing the fabrication of thermochromic multicolor patterns. During heating, each color starts shifting at a different temperature until the sample is entirely blue at a high temperature. Upon cooling, the multicolor pattern returns, showing that the thermochromic response is reversible. On top of that, linearly polarized light dependency is also obtained, showing different reflection colors when varying the incident light polarization angles. A multicolor, thermochromic photonic coating with light polarization- and structural color-dependent features is fabricated for demonstration.

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It is a great challenge to develop efficient room-temperature sensing materials and sensors for nitric oxide (NO) gas, which is a biomarker molecule used in the monitoring of inflammatory respiratory diseases. Herein, Hemin (Fe (III)-protoporphyrin IX) is introduced into the nitrogen-doped reduced graphene oxide (N-rGO) to obtain a novel sensing material HNG-ethanol. Detailed XPS spectra and DFT calculations confirm the formation of carbon–iron bonds in HNG-ethanol during synthesis process, which act as electron transport channels from graphene to Hemin. Owing to this unique chemical structure, HNG-ethanol exhibits superior gas sensing properties toward NO gas (R_a/R_g = 3.05, 20 ppm) with a practical limit of detection (LOD) of 500 ppb and reliable repeatability (over 5 cycles). The HNG-ethanol sensor also possesses high selectivity against other exhaled gases, high humidity resistance, and stability (less than 3% decrease over 30 days). In addition, a deep understanding of the gas sensing mechanisms is proposed for the first time in this work, which is instructive to the community for fabricating sensing materials based on graphene-iron derivatives in the future.

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The fabrication of reversible and robust thermochromic coatings remains challenging. In this work, a temperature-responsive photonic coating with a protective topcoat is fabricated. A cholesteric oligosiloxane liquid crystal possessing a smectic-to-cholesteric phase-transition temperature response is synthesized. A planar alignment of its cholesteric phase is possible with blade coating. By stabilizing with 3 wt % of a crosslinked liquid crystal network, the photonic coating shows a color change ranging from red to blue upon heating. High transparency is retained, and the structural color changes are fully reversible. A transparent polysiloxane layer can be directly applied on top of the cholesteric layer to protect it against damage without affecting its optical properties. This approach satisfies the basic requirements of thermochromic polymer coatings, as it combines easy processability, coating robustness, and a reversible temperature response.

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Graphene foams are promising three-dimensional (3D) architectures with the combination of the intrinsic nature of graphene and unique cellular structures for various realms. Herein, a facile technique is developed by combining supramolecular assembly with lyophilization to functionalize graphene with donor−π-acceptor (D−π-A) molecules and then massively transform the two-dimensional (2D) plane nanosheets into 3D foams. The as-prepared gas sensors work at room temperature (RT) and reveal comprehensive gas sensing performance with an ultrahigh response (R _a/R _g = 3.2, 10 ppm), excellent selectivity, and reliable repeatability toward NO ₂. Notably, a gas sensing enhancement mechanism with density functional theory (DFT) calculations is proposed to unravel the synergetic effect of the “Greater Electron Transferring Area” and the specific 3D foam structure for the enhancement of charge transfer and NO ₂ adsorption. The combination of supramolecular assembly and the lyophilization technique provides a strategy to prepare 3D architectural graphene-based materials for high-performance gas sensors and chemical trace detectors.

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A crosslinkable cholesteric main-chain liquid crystal oligomer was prepared, and coated on glass using blade-coating. The coating showed a reflection band that varied as a function of temperature over a range of several hundreds of nanometers. This allowed patterning of the coating in various colours using multiple crosslinking steps at different temperatures.

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A temperature-responsive near-infrared reflective coating was fabricated based on a side-chain liquid crystal siloxane polymer using a simple wired-bar method. The cholesteric liquid crystalline polymer film showed a blue shift of the reflection band of 1000 nm in the IR region upon heating. The temperature-responsive change of the reflection band was reversible. Compared to that of the same mixture system in an alignment cell, the coating showed a significantly faster response. This research demonstrates an easy way to prepare a temperature-responsive IR-reflective coating that shifts its reflection to a shorter wavelength upon heating. As IR radiation of shorter wavelengths is more strongly represented in sunlight than longer wavelengths, this coating could be used to selectively reduce heating of an indoor space when the temperature is high. This is promising for the future application of smart climate control.

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