5 research outputs found

    Environmentally Friendly High-Near-Infrared Reflectance Blue Pigment YIn<sub>0.9–<i>x</i></sub>Mn<sub>0.1</sub>M<sub><i>x</i></sub>O<sub>3−δ</sub> Based on Li/Zn Doping

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    In this work, the Li/Zn-doped near-infrared reflective inorganic blue pigment YIn0.9–xMn0.1MxO3−δ (M = Li/Zn, x = 0–0.4) was synthesized by the high-temperature solid-state reaction method. The phase structures, morphologies, color properties and optical properties of synthetic pigments were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), CIE1976 color space system, UV–vis-NIR spectrophotometer, and other instruments. All the doped samples have a hexagonal structure with space group P63cm (185). Compared with YIn0.9Mn0.1O3 (b* = −45.91), Li/Zn doped pigments have richer blue hues (b* is ranged from −29.59 to −55.14), which can meet the needs of public’s demands for blue hues. The NIR solar reflectance (R*) of all the samples are above 70%, and the highest R* with different doping concentrations can reach 86% (M = Li, x = 0.2), which is about 16% higher than YIn0.9Mn0.1O3. YIn0.9–xMn0.1MxO3−δ (M = Zn/Li, x = 0–0.4) are indicated to possess higher near-infrared solar reflectivity than other blue compounds, including commercial products. The surface temperature difference between the Li-doped (x = 0.2)/Zn-doped (x = 0.1) paints and commercial ultramarine paint can reach about 20 and 10 °C, respectively. The above properties ensure the potential applications of environmentally friendly YIn0.9–xMn0.1MxO3−δ pigments with a rich blue-hue in the field of energy-saving materials

    Tuning Molecular-Level Polymer Conformations Enables Dynamic Control over Both the Interfacial Behaviors of Ag Nanocubes and Their Assembled Metacrystals

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    In surface chemistry-directed nanoparticle self-assembly, it remains challenging to continuously modulate nanoparticle behavior at the oil/water interface without replacing surface functionality or particle morphology. Here, we utilize solvent-tunable molecular-level polymer conformation changes to achieve “multiple metacrystals using one nanoparticle with one chemical functionality”. We use Ag nanocubes functionalized with a mixed monolayer of thiol-terminated poly­(ethylene glycol) (PEG) and hexade­cane­thiol (C16). We continuously modulate PEG conformation from swollen to coiled states by decreasing solvent polarity, whereas C16 promotes nanocube dispersion in organic carrier solvents. Such PEG conformation changes drive Ag nanocubes to adopt tilted, standing, and planar configurations at the oil/water interface, with their interfacial positions changing from halfway across the interface to almost immersed within the oil phase. We also identify four specific polarities which enable Ag nanocubes to assemble into large-area metacrystals with linear, hexagonal, and square close-packed lattices. Our work establishes an innovative strategy to achieve robust tunability of nanoparticle interfacial behavior and unprecedented modulation of metacrystal structure

    Flexible Three-Dimensional Anticounterfeiting Plasmonic Security Labels: Utilizing <i>Z</i>‑Axis-Dependent SERS Readouts to Encode Multilayered Molecular Information

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    Current surface-enhanced Raman scattering (SERS)-based anticounterfeiting strategies primarily encode molecular information in single two-dimensional (2D) planes and under-utilize the three-dimensionality (3D) of plasmonic hot spots. Here, we demonstrate a 3D SERS anticounterfeiting platform, extending “layered security” capabilities from 2D to 3D. We achieve this capability by combining 3D candlestick microstructures with 3D hyperspectral SERS imaging to fully resolve at least three layers of encoded information within the same 2D area along the <i>z</i>-axis, notably using only a single probe molecule. Specific predesigned covert images can only be fully recovered via SERS imaging at predetermined <i>z</i> values. Furthermore, our 3D SERS anticounterfeiting security labels can be fabricated on both rigid and flexible substrates, widening their potential usages to curved product surfaces and banknotes

    A Chemical Approach To Break the Planar Configuration of Ag Nanocubes into Tunable Two-Dimensional Metasurfaces

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    Current plasmonic metasurfaces of nanocubes are limited to planar configurations, restricting the ability to create tailored local electromagnetic fields. Here, we report a new chemical strategy to achieve tunable metasurfaces with nonplanar nanocube orientations, creating novel lattice-dependent field localization patterns. We manipulate the interfacial behaviors of Ag nanocubes by controlling the ratio of hydrophilic/hydrophobic molecules added in a binary thiol mixture during the surface functionalization step. The nanocube orientation at an oil/water interface can consequently be continuously tuned from planar to tilted and standing configurations, leading to the organization of Ag nanocubes into three unique large-area metacrystals, including square close-packed, linear, and hexagonal lattices. In particular, the linear and hexagonal metacrystals are unusual open lattices comprising nonplanar nanocubes, creating unique local electromagnetic field distribution patterns. Large-area “hot hexagons” with significant delocalization of hot spots form in the hexagonal metacrystal. With a lowest packing density of 24%, the hexagonal metacrystal generates nearly 350-fold stronger surface-enhanced Raman scattering as compared to the other denser-packing metacrystals, demonstrating the importance of achieving control over the geometrical and spatial orientation of the nanocubes in the metacrystals

    Direct Metal Writing and Precise Positioning of Gold Nanoparticles within Microfluidic Channels for SERS Sensing of Gaseous Analytes

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    We demonstrate a one-step precise direct metal writing of well-defined and densely packed gold nanoparticle (AuNP) patterns with tunable physical and optical properties. We achieve this by using two-photon lithography on a Au precursor comprising poly­(vinylpyrrolidone) (PVP) and ethylene glycol (EG), where EG promotes higher reduction rates of Au­(III) salt via polyol reduction. Hence, clusters of monodisperse AuNP are generated along raster scanning of the laser, forming high-particle-density, well-defined structures. By varying the PVP concentration, we tune the AuNP size from 27.3 to 65.0 nm and the density from 172 to 965 particles/Οm<sup>2</sup>, corresponding to a surface roughness of 12.9 to 67.1 nm, which is important for surface-based applications such as surface-enhanced Raman scattering (SERS). We find that the microstructures exhibit an SERS enhancement factor of >10<sup>5</sup> and demonstrate remote writing of well-defined Au microstructures within a microfluidic channel for the SERS detection of gaseous molecules. We showcase in situ SERS monitoring of gaseous 4-methylbenzenethiol and real-time detection of multiple small gaseous species with no specific affinity to Au. This one-step, laser-induced fabrication of AuNP microstructures ignites a plethora of possibilities to position desired patterns directly onto or within most surfaces for the future creation of multifunctional lab-on-a-chip devices
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