Tunable solar-heat shielding property of transparent films based on mesoporous Sb-doped SnO₂ microspheres

Corrosion-Resistant Hydrophobic Thermal Barrier Composite Coating on Metal Strip: A New Dimension to Steel Strips for Roofing Segment

This study demonstrates a cost-effective, thin, multifunctional composite coating system with outstanding thermal insulation for thermal management and heat shield applications, such as roofs, as well as outstanding resistance to corrosion. The hydrophobic multifunctional epoxy composite coating systems were designed with surface-modified fillers to impart both reduced heat conduction and high infrared reflectance in a thin coating with a 65-100 μm dry film thickness (DFT). With a judicial combination of hollow microspheres (HMS) activated and modified with silica (sHMS) and stearic acid-modified TiO2 (sMO), the developed composite coating attained the highest thermal insulation property with a temperature drop of 21-31 °C at different distances below the coated panel, which is superior to the values of temperature drop reported earlier. The high solar reflectance of the composite coating in the near-infrared (NIR) region exceeds 72% with a low thermal conductivity of 0.178 W m-1 K-1. After 720 h of exposure in a 3.5 wt % NaCl solution, the composite coating revealed a corrosion protection efficiency of 99%. The work demonstrates that high solar reflectivity and low thermal conductivity must be active simultaneously to achieve superior thermal shielding in a thin coating on a metal. A careful selection of fillers and appropriate surface modifications ensures hydrophobicity and proper distribution of the fillers in the coating for a high barrier effect to prevent environmental deterioration. With these superior performance parameters, the developed composite coatings make an essential contribution to energy sustainability and the protection against environmental degradation.

Gigantic Thermal Shielding in 2D Oxide Nanosheets

Thermal shielding materials that can block near-infrared (NIR) light from the sunlight while maintaining visible transparency have become increasingly important from an energy-saving perspective. Here, we demonstrate a gigantic NIR shielding by an engineered plasmonic material based on a two-dimensional (2D) polytungstate (Cs_4-xW₁₁O_35-d). Starting from a charge-neutral polytungstate (Cs₄W₁₁O₃₅), we synthesize charge-imbalanced 2D nanosheets (Cs_4-xW₁₁O_35-d) that undergo an unusual structural change with the semiconductor-to-metal transition in a reduced atmosphere. Layer-by-layer engineering of the 2D nanosheets enables a plasmon-induced enhancement of the NIR reflectance (>53%) with a high visible transparency (>71%), realizing high-performance thermal shielding. Our approach offers a solution for future thermal management technology.

Infrared Plasmonic Metamaterials Based on Transparent Nanoparticle Films of In2O3:Sn for Solar-Thermal Shielding Applications

Three-dimensional nanoparticle (NP) assemblies show interesting optical responses that differ from naturally occurring materials, such as metals, oxides, and semiconductors. In this study, we investigate the optical response of thin films comprising Sn:In₂O₃ NPs (ITO NP films) based on the correlation between complex permittivity and infrared (IR) reflectance for solar-thermal shielding applications. IR ellipsometry measurements are conducted to clarify the presence of Lorentz resonances in plasmonic metamaterials. The Lorentz resonances are correlated to the electric field strength at interparticle gaps by varying the Sn dopant concentration, as confirmed using finite-difference time-domain (FDTD) simulations. High solar-thermal shielding performance was obtained owing to selective near-IR reflection based on strong Lorentz resonances as the ITO NP films were electrically polarizable but magnetically inactive. Thermal shielding efficiency was demonstrated via a comparison of the air temperature change in a simulated box used as a model house. Additionally, we demonstrate the significance of NP packing density on the enhancement of the near-IR reflectance. The role of interparticle spacing for high near-IR reflectance was revealed by comparing effective medium approximation analyses and FDTD simulations. This relationship was also demonstrated by the reduction of solar-thermal shielding performance when using aggregated ITO NPs. Our work confirmed that the control of complex permittivity in plasmonic metamaterials must be considered in the structural design of transparent and reflective materials for solar-thermal shielding applications.

High performance {Nb5TaX12}@PVP (X = Cl, Br) cluster-based nanocomposites coatings for solar glazing applications

The development of highly ultraviolet (UV) and near-infrared (NIR) absorbent transparent coatings is an important enabling technology and area of research for environmental sustainability and energy conservation. Different amounts of K₄[{Nb₅TaXⁱ ₁₂}X^a ₆] cluster compounds (X = Cl, Br) dispersed into polyvinylpyrrolidone matrices were prepared by a simple, nontoxic and low-cost wet chemical method. The resulting solutions were used to fabricate visibly transparent, highly UV and NIR absorbent coatings by drop casting. The properties of the solution and films were investigated by complementary techniques (optical absorption, electrospray ionization mass spectrometry and Raman spectroscopy). The UV and NIR absorption of such samples strongly depended on the concentration, dispersion and oxidation state of the [{Nb₅TaXⁱ ₁₂}X^a ₆] nanocluster-based units. By varying and controlling these parameters, a remarkable improvement of the figures of merit T_L/T_E and S_NIR for solar-glazing applications was achieved compared to the previous results on nanocomposite coatings based on metal atom clusters.

Controlling the Deposition Process of Nanoarchitectonic Nanocomposites Based on {Nb6-xTaxXi12}n+ Octahedral Cluster-Based Building Blocks (Xi = Cl, Br; 0 ≤ x ≤ 6, n = 2, 3, 4) for UV-NIR Blockers Coating Applications

The antagonism between global energy needs and the obligation to slow global warming is a current challenge. In order to ensure sufficient thermal comfort, the automotive, housing and agricultural building sectors are major energy consumers. Solar control materials and more particularly, selective glazing are part of the solutions proposed to reduce global energy consumption and tackle global warming. In this context, these works are focused on developing new highly ultraviolet (UV) and near-infrared (NIR) absorbent nanocomposite coatings based on K₄[{Nb_6-xTa_xXⁱ₁₂}X^a₆]. (X = Cl, Br, 0 ≤ x ≤ 6) transition metal cluster compounds. These compounds contain cluster-based active species that are characterized by their strong absorption of UV and NIR radiations as well as their good transparency in the visible range, which makes them particularly attractive for window applications. Their integration, by solution processes, into a silica-polyethylene glycol or polyvinylpyrrolidone matrices is discussed. Of particular interest is the control and the tuning of their optical properties during the integration and shaping processes. The properties of the solutions and films were investigated by complementary techniques (UV-Vis-NIR spectrometry, ESI-MS, SEM, HRTEM, etc.). Results of these works have led to the development of versatile solar control coatings whose optical properties are competitive with commercialized material.

Multilayer Polymer Photonic Aegises Against Near-Infrared Solar Irradiation Heating

Preventing solar heating is nowadays of paramount interest in energy savings and health preservation. For instance, in building thermalization solar heating consumes an excess of energy leading to harmful CO₂ emissions, while in food and beverage packaging it may lead to variation of organoleptic properties or even health issues. The phenomenon is attributed to the large presence of moieties with highly absorbing vibrational overtones and combination bands in the near-infrared spectral region that induces heating in water, moisture, and in polymers used in packaging. Thus, reducing and controlling the light absorbed by these materials with effective low-cost passive systems can play a major role in energy saving and health preservation. In this work, different polymer dielectric mirrors are reported, made of poly(N-vinylcarbazole) and either cellulose acetate or poly(acrylic acid), and able to selectively reflect near-infrared radiation while maintaining high transparency in the visible range. To this end, simple, tandem, and superperiodic mirrors are used to shield radiation impinging on samples of water and paraffin, demonstrating shielding efficiencies up to 52% with respect to unshielded references, promising a new paradigm to solve thermal management issues.

Preparation of Tin-Antimony anode modified with carbon nanotubes for electrochemical treatment of coking wastewater

To improve the electrocatalytic activity, carbon nanotubes (CNTs) were used to modify a titanium-supported tin-antimony anode (Ti/SnO₂-Sb). Compared to a Ti/SnO₂-Sb anode, the Ti/SnO₂-Sb-CNTs anode exhibited a higher oxygen evolution potential (1.62 V), smaller crystalline volume (71.23 Å³), larger active surface area (0.371 mC cm^-2), lower charge transfer resistance (8.24 Ω), and longer service life (291 h). The CNTs provided the Ti/SnO₂-Sb anode with effective electrocatalytic activity, conductivity and stability. To evaluate its performance, the Ti/SnO₂-Sb-CNTs anode was utilized for the treatment of coking wastewater. The chemical oxygen demand (COD) and total organic carbon (TOC) removal yields of the coking wastewater reached 83.05% and 74.56% under the optimal current density of 25 mA m^-2, Na₂SO₄ concentration of 35 mM, and plate spacing of 10 mm. UV₂₅₄, ultraviolet-visible absorption spectroscopy, excitation-emission matrix spectra spectroscopy, and Fourier-transform infrared spectroscopy analyses showed that the aromatic and nitrogenous compounds in the coking wastewater were degraded. Furthermore, the electrochemical treatment could effectively reduce the toxicity of the coking wastewater. The energy consumption of the coking wastewater treatment was reduced to 396.56 kWh (kg COD)^-1. This study provides a basis engineering application of the electrochemical oxidation of coking wastewater.

Sb/Pd co-doped SnO2nanoparticles for methane detection: resistance reduction and sensing performance studies

Methane (CH₄) gas sensors play an important role in industrial safety and detection of indoor gas quality. In general, metal oxide semiconductor sensing materials with nano-structure have high responses to the target gas. However, the sensor resistance is usually very high. Considering the practical application, it is vital to reduce base resistance and improve sensitivity for gas sensors. Herein, Pd-doped SnO₂nanoparticles were prepared as the basis material by a simple sol-gel method. In order to adjust the resistance, the pentavalent metal element (Sb) was introduced via a simple doping route. As CH₄sensing layers, the prepared SnO₂-sensors doped with Pd and Sb exhibited the most obvious resistance reduction effect. Meantime, excellent sensing performances including high response, fast response/recovery time, excellent reproducibility and great stability were also obtained. In-depth research has shown that the ability to reduce resistance depends on the effective internal doping of cation with high valence. The enhanced sensing capability can be attributed to the 'synergistic effects' including catalytic effects of novel metals, increased oxygen vacancies and decreased band gap energy. This work can provide a new opportunity to design metal oxide sensing materials with low resistance and high sensitivity.

Flexible core-shell Cs x WO3-based films with high UV/NIR filtration efficiency and stability

Cesium-doped tungsten bronze Cs _x WO₃ (CWO) is an ideal near infrared (NIR) shielding material for solar filters. However, the NIR shielding ability of CWO-dispersed films easily deteriorates in hot humid environments, which severely hinders the commercial application of CWO. In this paper, UV/NIR shielding nanocomposite films were prepared by dispersing core-shell structured CWO@polydopamine (CWO@PDA) in a poly(vinyl alcohol) matrix. Because of the strong ultraviolet light absorption ability of PDA, it can shield ultraviolet light, which is generally detrimental to our health. The prepared nanocomposite films can efficiently shield 88.3% UV and 85.5% NIR radiation even though they show relatively high transparency in the visible range. Importantly, the good protection of the continuous PDA shells played an important role in enhancing the stability of CWO nanoparticles. The nanocomposite films also exhibit excellent stability in hot humid environments. Therefore, core-shell structured CWO@PDA nanoparticles have great potential as a novel UV/NIR shielding material for the development of efficient energy-saving windows.

Dopant-dependent crystallization and photothermal effect of Sb-doped SnO2 nanoparticles as stable theranostic nanoagents for tumor ablation

Ideal theranostic nanoagents should be "all-in-one" type nanocrystals that have a single-semiconductor component and all-required properties (such as imaging and photothermal effects), but most semiconductor nanocrystals do not have these required properties. With SnO₂ as a model of a typical wide-band semiconductor, we report the tuning from UV-responsive SnO₂ to blue SnO₂ nanocrystals with imaging ability and a Sb-doping-dependent photothermal effect. Sb-Doped SnO₂ nanocrystals were prepared by heating SbCl₃ and SnCl₄ in benzyl alcohol solution through a facile solvothermal route. When the SbCl₃/SnCl₄ molar ratio increases from 0 to 0.2/1, the obtained samples exhibit an increased photothermal effect under the irradiation of a 1064 nm laser, accompanied by gradually decreased size and crystallinity. With a further increase of the molar ratio from 0.3/1.0 to 1.0/1.0, the resulting samples demonstrate the tetragonal SnO₂ phase with amorphous-like compounds and they show no obvious enhancement of a photothermal effect. After a surface modification with biological molecules, the optimized Sb_0.2-SnO₂ nanocrystals demonstrated good stability and a high photothermal conversion efficiency of 48.3% as well as low cytotoxicity. When Sb_0.2-SnO₂ was injected into a tumor of mice, the tumor could be simultaneously detected by X-ray computed tomography (CT) and photoacoustic (PA) imaging, and then thermally ablated when exposed to a 1064 nm laser. Therefore, these nanocrystals can be used as "all-in-one" type nanoagents for imaging guided photothermal ablation of tumors under the irradiation of a laser in the second bio-transparent window.

Silanated nano ZnO hybrid embedded PMMA polymer coatings on cotton fabrics for near-IR reflective, antifungal cool-textiles

Silanated nano ZnO hybrid embedded PMMA polymer coatings for cotton fabrics are developed to produce near-IR reflective, antifungal cool-textiles.