The design of new advanced materials and technologies is essential for the development of smart windows for the next generation of energy-efficient buildings. Here, it is demonstrated that the functionalization of glucose-derived carbon dots with 1-butyl-3-methylimidazolium chloride results in a self-standing, water-soluble, viscous, reusable nanofluid with self-improving conductivity, thermotropy around 30-40 °C, and ultraviolet blocking ability. Its synthesis is straightforward, clean, fast, and cheap. At 36 °C (hot summer day), a sunactuated thermotropic (TT) device incorporating a 95% w/w nanofluid aqueous solution exhibits a transmittance variation (ΔT) of 9% at 550/1000 nm, which is amplified to 47/31% via the surface plasmon resonance effect. An integrated self-healing system enabling independent sun-actuated TT and voltage-actuated electrochromic (EC) operation is also produced. The low-energy EC device offers bright hot and dark cold modes (ΔT = 68/64%), excellent cycling stability, unprecedented coloration efficiency values (−1.73 × 10 6 /−1.67 × 10 6 cm 2 C −1 (coloring) and +1.12 × 10 7 /+1.08 × 10 7 cm 2 C −1 (bleaching) at ±2.5 V), and impressive memory effect. The disruptive design and sustainable synthesis of the new nanofluid proposed here will foster the agile development of novel products with improved ecological footprint.

(001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented SrTiO3 (STO) substrates. The α-phase (high-temperature phase in bulk) is successfully stabilized with an orthorhombic structure (a = 16.585(1) Å, b = 5.717(2) Å, c = 8.865(5) Å). X-ray-diffraction pole-figure measurements suggest that crystallographic relationships between the film and substrate are [100]LWO ∥ [110]STO, [010]LWO ∥ [11̅0]STO and [001]LWO ∥ [001]STO. From optical properties, investigated by spectroscopic ellipsometry, we extract a refractive-index value around 2 (at 500 nm) along with the presence of two absorption bands situated, respectively at 3.07 and 6.32 eV. Ferroelectricity is evidenced as well on macroscale (standard polarization measurements) as on nanoscale, calling for experiments based on piezo-response force-microscopy, and confirmed with in situ scanning-and-tunneling measurements performed with a transmission electron microscope. This work highlights the ferroelectric behavior, at room temperature, in high-temperature LWO phase when stabilized in thin film and opens the way to new functional oxide thin films dedicated to advanced electronic devices.

Taking advantage of strain engineering, Nd2WO6 (NdWO) thin films have been successfully grown on (001)-oriented SrTiO3 single-crystal substrates by pulsed-laser deposition. High-resolution X-ray diffraction characterizations highlight the stabilization of a new orthorhombic (Pm21 n) NdWO polymorphic form, isostructural to α-La2WO6. Reciprocal space mappings have been used in the determination of the NdWO thin-film structure. Coupled with the 2θ-ω X-ray patterns, the cell parameters were calculated: a = 16.34(5) Å, b = 5.46(5) Å, and c = 8.68(1) Å. X-ray-diffraction pole-figure measurements show the crystallographic relationships between the film and substrate: [100]NdWO∥[110]STO, [010]NdWO∥[11̅0]STO, and [001]NdWO∥[001]STO. Both X-ray diffraction and transmission electron microscopy studies reveal the existence of (510)-oriented crystallites with respect to the plane of the substrate mainly at the interface film/substrate and dispersed in the (001)-NdWO matrix. In addition, robust piezoelectricity and ferroelectricity are revealed at room temperature through both local hysteresis loops and domain manipulation experiments using the piezoresponse force microscopy technique. Typical polarization retention behaviors associated with specific nanoscale conduction are in good agreement with the classical ferroelectric phenomenon in oxide materials. The successful observation of piezo-/ferroelectricity at room temperature in innovative strain-stabilized α-NdWO thin films paves the way for new lead-free functional materials devoted to numerous applications, including actuators, sensors, or nonvolatile memory devices.

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Glass thin films (with nanometer to micrometer thicknesses) are promising in numerous applications, both as passive coatings and as active components. Self-healing is a feature of many current technological developments as a means of increasing the lifetime of materials. In the context of these developments, we report on the elaboration of the first self-healing glassy thin-film coating developed specifically for high-temperature applications. This coating is obtained by pulsed laser deposition of alternating layers of vanadium boride (VB) and a multicomponent oxide glass. Self-healing is obtained through the oxidation of VB at the operating temperature. The investigation of the effect of elaboration parameters on the coating composition and morphology made it possible to obtain up to seven-layer coatings, with good homogeneity and perfect interfaces, and with a total thickness of less than 1 μm. The autonomic self-healing capacity of the coating has been demonstrated by an in situ experiment, which shows that a crack of nanometric dimension can be healed within a few minutes at 700 °C.