Tailor-Made White Photothermal Fabrics: A Bridge between Pragmatism and Aesthetic

Colorful photothermal photonic crystal cotton fabric based on melanin-like polycaffeic acid nanoparticles

Photothermal materials have been extensively researched and utilized owing to their exceptional energy conversion capabilities. However, developing dual-functional materials with both vivid coloration and efficient photothermal performance remains a significant challenge, primarily because most photothermal materials have an undesirable black appearance. Herein, colorful photothermal polycaffeic photonic crystal (PCfA PC) cotton fabric was successfully created by assembling melanin-like polycaffeic acid nanoparticles (PCfA NPs) with adjustable size and high monodispersity. The photothermal performance of the PCfA NPs enabled the developed PCfA PC cotton fabric to reach a temperature increase of 86 °C under laser irradiation at a power density of 0.298 W/cm2, suggesting a high photothermal conversion efficiency of 50.6 %. The PCfA PC fabric also demonstrated adjustable, broad spectrum, and highly saturated structural colors, thanks to the regulation of visible light by the PC nanoparticle array. This innovative colorful photothermal fabric effectively combines the inherent photothermal performance of PCfA NPs with the ability of the PCfA PC to modulate visible light, providing novel materials for photothermal imaging and flexible anti-counterfeiting applications.

Large-area radiation-modulated thermoelectric fabrics for high-performance thermal management and electricity generation

Flexible thermoelectric systems capable of converting human body heat or solar heat into sustainable electricity are crucial for the development of self-powered wearable electronics. However, challenges persist in maintaining a stable temperature gradient and enabling scalable fabrication for their commercialization. Herein, we present a facile approach involving the screen printing of large-scale carbon nanotube (CNT)-based thermoelectric arrays on conventional textile. These arrays were integrated with the radiation-modulated thermoelectric fabrics of electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes for the low-cost and high-performance wearable self-power application. Combined with the excellent photothermal properties of CNTs, the resulting thermoelectric fabric (0.2 square meters) achieves a substantial ΔT of 37 kelvin under a solar intensity of ~800 watt per square meter, yielding a peak power density of 0.20 milliwatt per square meter. This study offers a pragmatic pathway to simultaneously address thermal management and electricity generation in self-powered wearable applications by efficiently harvesting solar energy.

A Scalable and Robust Personal Health Management Textile with Multiple Desired Thermal Functions and Electromagnetic Shielding

The development of functional textiles combining conventional apparel with advanced technologies for personal health management (PHM) has garnered widespread attention. However, the current PHM textiles often achieve multifunctionality by stacking functional modules, leading to poor durability and scalability. Herein, a scalable and robust PHM textile is designed by integrating electrical, radiative, and solar heating, electromagnetic interference (EMI) shielding, and piezoresistive sensing performance onto cotton fabric. This is achieved through an uncomplicated screen-printing process using silver paste. The conductivity of the PHM textile is ≈1.6  ×  104 S m-1, ensuring an electric heating temperature of ≈134 °C with a low voltage of 1.7 V, as well as an EMI shielding effectiveness of ≈56 dB, and human motion monitoring performance. Surprisingly, the radiative/solar heating capability of the PHM textile surpasses that of traditional warm leather. Even after undergoing rigorous physical and chemical treatments, the PHM textile maintains terrific durability. Additionally, the PHM textile possesses maneuverable scalability and comfortable wearability. This innovative work opens up new avenues for the strategic design of PHM textiles and provides an advantageous guarantee of mass production.

Rational design and easy fabrication of transparent photothermal/hygroscopic composite coatings with long-lasting antifogging performance under sunlight activation

Hygroscopic polymers are good candidates for antifogging coatings, but their long-term effectiveness is limited by the equilibrium between water absorption and expansion. As an efficient and environmentally friendly solution, photothermal materials are being introduced into the field of antifogging. However, there is a need for enhancement in the spectral characteristics of most photothermal materials within the visible light region. In addition, photothermal antifogging coatings often exhibit a delay in heating response, which hinders their ability to promptly evaporate condensed water droplets in the absence of illumination or during initial illumination. Here, a bilayer structure design of photothermal nanomaterials/hygroscopic polymers is proposed to achieve long-term antifogging under sunlight activation. Ensuring the rapid absorption of condensed water droplets on the coating surface, while simultaneously achieving efficient photothermal conversion for a swift temperature increase over the entire coating, is key to this approach, which will not only suppress early fogging but also lead to an exponential decrease of the nucleation rate of droplets. During this process, a dynamic equilibrium is gradually established between the condensation and evaporation of fog droplets, leading to long-term antifogging properties. The light transmittance of the composite coatings reaches as high as ca. 75% in the visible light region, making them well suited for a diverse range of transparent substrate and device applications. A clear field of view can be maintained for at least 6 h under 1 sun illumination above 65 °C hot steam. The antifogging/defogging performance is effectively demonstrated even under challenging non-ideal natural conditions, such as low solar irradiation during dusk or when placed indoors behind windows.

Absorption peak decomposition of an inhomogeneous nanoparticle ensemble of hexagonal tungsten bronzes using the reduced Mie scattering integration method

Recent optical analyses of cesium-doped hexagonal tungsten bronze have accurately replicated the absorption peak and identified both plasmonic and polaronic absorptions in the near-infrared region, which have been exploited in various technological applications. However, the absorption peaks of tungsten oxides and bronzes have not generally been reproduced well, including those of the homologous potassium- and rubidium-doped hexagonal tungsten bronzes that lacked evidence of polaronic subpeaks. The present study reports a modified and simplified Mie scattering integration method which incorporates the ensemble inhomogeneity effect and allows precise peak decomposition and determination of the physical parameters of nanoparticles. The decomposed peaks were interpreted in terms of electronic structures, screening effect, and modified dielectric functions. The analysis revealed that the plasma frequencies, polaron energies, and the number of oxygen vacancies decrease in the dopant order Cs → Rb → K. The coexistence of plasmonic and polaronic excitations was confirmed for all the alkali-doped hexagonal tungsten bronzes.

Ag-lignin hybrid nanoparticles for high-performance solar absorption in photothermal antibacterial chitosan films

There is an urgent need for antimicrobial films based on sustainable resources and production methods. In this study, we present a bio-based nanocomposite film composed of chitosan (∼60 wt %), lignin nanoparticles (LNPs, ∼40 wt %), a small amount of glutaraldehyde (1.5 wt %), and a trace level of silver nanoparticles (AgNPs, 0.072 wt %). The uniform dispersion with LNPs prevented aggregation of metallic silver, resulting in small (diameter 3.3 nm) AgNPs. The nanocomposite film absorbs 89% of radiation across the entire solar spectrum and exhibits a remarkable photothermally triggered antibacterial effect, which is further enhanced by the dark color of lignin. Under simulated solar light illumination, the nanocomposite films demonstrated a significant reduction in viable Escherichia coli count compared to control scenarios. The potential applications of these nanocomposites extend to sunlight-activated antimicrobial films and coatings, addressing the growing demand for sustainable and effective antimicrobial materials.