Plasmonic Ti3C2Tx MXene Enables Highly Efficient Photothermal Conversion for Healable and Transparent Wearable Device

Highly sensitive volatile organic compounds monitoring enabling by silver-nanowire@metal-organic frameworks core-shell heterostructure

Metal-organic frameworks (MOFs) hold great promise as advanced chemical sensing materials due to their high surface area and tunable surface chemistry. However, due to the inherent conductivity, building a highly sensitive MOFs-based gas sensor for real-time monitoring hazardous gas operated at room temperature (RT) is still a huge challenge. Herein, an in-situ anchoring strategy is proposed to construct a 1D-0D core-shell heterostructure by integrating silver nanowires (AgNWs) with highly conductivity and Zn-MOF with high specific surface area. The incorporation of AgNWs establishes a highly conductive network architecture to facilitate rapid charge transport while preventing the Zn-MOF nanoparticles from agglomeration, ensuring an effective transmission highway for target gas molecules. Meanwhile, the Zn-MOF nanoparticles induce remarkable absorption capacity and contribute high gas response. By strategically amalgamating the inherent distinctive virtues of the individual components and capitalizing on the synergistic benefits arising from the composite, the sensors hinged upon the refined AgNWs@Zn-MOF (A@Z) heterostructure unveiled remarkable response value of 27 to 20 ppm ethanol at RT, accompanied by a low detection limit of 1 ppm. Moreover, the A@Z sensor further showcases superior selectivity and repeatability. This work offers a fresh standpoint for the fabrication of MOF-based heterostructures, fostering advancements in diverse applications.

Variable-transmittance bio-based phase change composites based on the photothermal property of pectin

In this study, the possibility of using a natural polysaccharide, pectin, in a novel function as a photothermal material was investigated by fabricating a Pectin/Polyethylene glycol (PEG)/Poly(methyl methacrylate) (PMMA) composite via the infiltration of PEG/PMMA polymer mixture into freeze-casted pectin cryogel template. The Pectin/PEG/PMMA composite has high latent heat of 48 J/g, excellent UV blocking ability, and tailorable transmittance as well as capacity to energy storage via photothermal heating to the melting point of PEG under sunlight. The photothermal effect can be enhanced with the increase of pectin concentration and irradiation intensity. Furthermore, by using the Pectin/PEG/PMMA composite as a window of a model house could effectively reduce the temperature rise inside the house under irradiation and reduce the temperature drop after turning off the irradiation, as compared to a model house with conventional glass as the window material. Therefore, this work provides a new application of pectin as photothermal material and opens the opportunity to develop novel sustainable bio-based photothermal materials.

Mechanical reinforcement from two-dimensional nanofillers: model, bulk and hybrid polymer nanocomposites

Thanks to their intrinsic properties, multifunctionality and unique geometrical features, two-dimensional nanomaterials have been used widely as reinforcements in polymer nanocomposites. The effective mechanical reinforcement of polymers is, however, a multifaceted problem as it depends not only on the intrinsic properties of the fillers and the matrix, but also upon a number of other important parameters. These parameters include the processing method, the interfacial properties, the aspect ratio, defects, orientation, agglomeration and volume fraction of the fillers. In this review, we summarize recent advances in the mechanical reinforcement of polymer nanocomposites from two-dimensional nanofillers with an emphasis on the mechanisms of reinforcement. Model, bulk and hybrid polymer nanocomposites are reviewed comprehensively. The use of Raman and photoluminescence spectroscopies is examined in light of the distinctive information they can yield upon stress transfer at interfaces. It is shown that the very diverse family of 2D nanofillers includes a number of materials that can attribute distrinctive features to a polymeric matrix, and we focus on the mechanical properties of both graphene and some of the most important 2D materials beyond graphene, including boron nitride, molybdenum disulphide, other transition metal dichalcogenides, MXenes and black phosphorous. In the first part of the review we evaluate the mechanical properties of 2D nanoplatelets in "model" nanocomposites. Next we examine how the performance of these materials can be optimised in bulk nanocomposites. Finally, combinations of these 2D nanofillers with other 2D nanomaterials or with nanofillers of other dimensions are assessed thoroughly, as such combinations can lead to additive or even synergistic mechanical effects. Existing unsolved problems and future perspectives are discussed.

Double-drying 3D lamellar-structured aerogel membrane for efficient oil-water separation and long-lasting antibacterial activity

Conventional oil-water separation membranes are difficult to establish a trade-off between membrane flux and separation efficiency, and often result in serious secondary contamination due to their fouling issue and non-degradability. Herein, a double drying strategy was introduced through a combination of oven-drying and freeze-drying to create a super-wettable and eco-friendly oil-water separating aerogel membrane (TMAdf). Due to the regular nacre-like structures developed in the drying process and the pores formed by freeze-drying, TMAdf aerogel membrane finally develops regularly arranged porous structures. In addition, the aerogel membrane possesses excellent underwater superoleophobicity with a contact angle above 168° and antifouling properties. TMAdf aerogel membrane can effectively separate different kinds of oil-water mixtures and highly emulsified oil-water dispersions under gravity alone, achieving exceptionally high flux (3693 L·m-2·h-1) and efficiency (99 %), while being recyclable. The aerogel membrane also displays stability and universality, making it effective in removing oil droplets from water in corrosive environments such as acids, salts and alkalis. Furthermore, TMAdf aerogel membrane shows long-lasting antibacterial properties (photothermal sterilization up to 6 times) and biodegradability (completely degraded after 50 days in soil). This study presents new ideas and insights for the fabrication of multifunctional membranes for oil-water separation.

Ultrahigh Thermal Conductivity of Epoxy/Ag Flakes/MXene@Ag Composites Achieved by In Situ Sintering of Silver Nanoparticles

The growing use of high-power and integrated electronic devices has created a need for thermal conductive adhesives (TCAs) with high thermal conductivity (TC) to manage heat dissipation at the interface. However, TCAs are often limited by contact thermal resistance at the interface between materials. In this study, we synthesized MXene@Ag composites through a direct in situ reduction process. The Ag nanoparticles (Ag NPs) generated by the reduction of the MXene interlayer and surface formed effective thermally conductive pathways with Ag flakes within an epoxy resin matrix. Various characterization analyses revealed that adding MXene@Ag composites at a concentration of 3 wt % resulted in a remarkable TC of 40.80 W/(m·K). This value is 8.77 times higher than that achieved with Ag flakes and 7.9 times higher than with MXene filler alone. The improved TC is attributed to the sintering of the in situ reduced Ag NPs during the curing process, which formed a connection between MXene (a highly conductive material) and the Ag flakes, thereby reducing contact thermal resistance. This reduction in contact thermal resistance significantly enhanced the TC of the thermal interface materials (TIMs). This study presents a novel approach for developing materials with exceptionally high TC, opening new possibilities for the design and fabrication of advanced thermal management systems.

Fabrication of a MXene-based shape-memory hydrogel and its application in the wound repair of skin

Wound dressings can generally complete hemostasis and provide temporary protection after skin damage. Herein, a MXene-based hydrogel was prepared from MXene, gelatin, poly(ethylene glycol)diacrylate (PEGDA) and N,N'-methylenebis(acrylamide) (HEAA) to prepare wound-dressing hydrogels for skin repair. HEAA and PEGDA crosslink polymerization formed the first layer of the network. Hydrogen bonds between MXene, PHEAA, and gelatin formed the second layer of the network. To make the hydrogel more suitable for skin repair, the mechanical properties of the hybrid hydrogel were adjusted. The MXene-based hydrogel could recover its original shape in 16 s upon immersion in water or for a few minutes under light irradiation. The obtained hydrogel showed good photothermal properties upon light irradiation (808 nm, 1 W cm-2) for 20 s, and its temperature on the surface could reach 86.4 °C. Due to its good photothermal properties, this MXene-based hydrogel was suitable for skin repair.

Robust and Superhydrophobic Polydimethylsiloxane/Ni@Ti3C2Tx Nanocomposite Coatings with Assembled Eyelash-Like Microstructure Array: A New Approach for Effective Passive Anti-Icing and Active Photothermal Deicing

To solve the problem of ice condensation and adhesion, it is urgent to develop new anti-icing and deicing technologies. This study presented the development of a highly efficient photothermal-enhanced superhydrophobic PDMS/Ni@Ti3C2Tx composite film (m-NMPA) fabricated cost-effectively and straightforwardly. This film was fabricated utilizing PDMS as a hydrophobic agent, adhesive, and surface protector, while Ni@Ti3C2Tx as a magnetic photothermal filler innovatively. Through a simple spraying method, the filler is guided by a strong magnetic field to self-assemble into an eyelash-like microstructure array. The unique structure not only imparts superhydrophobic properties to the surface but also constructs an efficient "light-capturing" architecture. Remarkably, the m-NMPA film demonstrates outstanding superhydrophobic passive anti-icing and efficient photothermal active deicing performance without the use of fluorinated chemicals. The micro-/nanostructure of the film forms a gas layer, significantly delaying the freezing time of water. Particularly under extreme cold conditions (-30 °C), the freezing time is extended by a factor of 7.3 compared to the bare substrate. Furthermore, under sunlight exposure, surface droplets do not freeze. The excellent photothermal performance is attributed to the firm anchoring of nickel particles on the MXene surface, facilitating effective "point-to-face" photothermal synergy. The eyelash-like microarray structure enhances light-capturing capability, resulting in a high light absorption rate of 98%. Furthermore, the microstructure aids in maintaining heat at the uppermost layer of the surface, maximizing the utilization of thermal energy for ice melting and frost thawing. Under solar irradiation, the m-NMPA film can rapidly melt approximately a 4 mm thick ice layer within 558 s and expel the melted water promptly, reducing the risk of secondary icing. Additionally, the ice adhesion force on the surface of the m-NMPA film is remarkably low, with an adhesion strength of approximately 4.7 kPa for a 1 × 1 cm2 ice column. After undergoing rigorous durability tests, including xenon lamp weathering test, pressure resistance test, repeated adhesive tape testing, xenon lamp irradiation, water drop impact testing, and repeated brushing with hydrochloric acid and particles, the film's surface structure and superhydrophobic performance have remained exceptional. The photothermal superhydrophobic passive anti-icing and active deicing technology in this work rely on sustainable solar energy for efficient heat generation. It presents broad prospects for practical applications with advantages such as simple processing method, environmental friendliness, outstanding anti-icing effects, and exceptional durability.

MXene-Enhanced Ionovoltaic Effect by Evaporation and Water Infiltration in Semiconductor Nanochannels

In recent years, substantial attention has been directed toward energy-harvesting systems that exploit sunlight energy and water resources. Intensive research efforts are underway to develop energy generation methodologies through interactions with water using various materials. In the present investigation, we synthesized sodium vanadium oxide (SVO) nanorods with n-type semiconductor characteristics. These nanorods facilitate the initiation of capillary phenomena within nanochannels, thereby enhancing the interfacial area between nanomaterials and ions. The open-circuit voltage (VOC) was 0.8 V, and the short-circuit current (ISC) was 30 μA, which were continuously monitored at room temperature using a 0.1 M saltwater solution. Additionally, we achieved enhanced energy generation by efficiently converting light energy into thermal energy using MXene, a 2D material. This was accomplished through the photothermal effect, leveraging the inherent semiconductor characteristics. Under light exposure, the system exhibited improved performance attributed to heightened ion diffusion and increased conductivity. This phenomenon was a result of the concerted synergy between ions and electrons facilitated by a semiconductor nanofluidic channel. Ultimately, we demonstrated an application to showcase real-world viability. In this scenario, electricity was harvested through a smart buoy floating on the water, and, based on this, data from the surrounding environment was sensed and wirelessly transmitted.

Elevating Low-Grade Heat Harvesting with Daytime Radiative Cooling and Solar Heating in Thermally Regenerative Electrochemical Cycles

Thermal radiation control has garnered growing interest for its ability to provide localized cooling and heating without energy consumption. However, its direct application for energy harvesting remains largely underexplored. In this work, we demonstrate a novel system that leverages daytime radiative cooling and solar heating technologies to continuously power charging-free thermally regenerative electrochemical cycle (TREC) devices, turning ubiquitous low-grade ambient heat into electricity. Notably, by harnessing a substantial 35 °C temperature differential solely through passive cooling and heating effects, the integrated system exhibits a cell voltage of 50 mV and a specific capacity exceeding 20 mAh g-1 of PB. This work unlocks the potential of readily available low-grade ambient heat for sustainable electricity generation.

Rotini-like MXene@LCE Actuator with Diverse and Programmable Actuation Based on Dual-mode Synergy

Liquid crystalline elastomer (LCE) exhibits muscle-like actuation upon order-disturbed stimulus, offering ample room for designing soft robotic systems. Multimodal LCE is demonstrated to unleash the potential to perform multitasks. However, each actuation mode is typically isolated. In contrast, coordination between different actuation modes based on an MXene-doped LCE is realized, whose actuation can be triggered either by directly heating/cooling or using near-infrared light due to the photo-thermal effect of MXene. As such, the two activation modes (heat and light) not only can work individually to offer stable actuation under different conditions but also can collaborate synergistically to generate more intelligent motions, such as achieving the brake and turn of an autonomous rolling. The principle therefore can diversify the design principles for multifunctional soft actuators and robotics.

Advancements in Nanoenabled Membrane Distillation for a Sustainable Water-Energy-Environment Nexus

The emergence of nano innovations in membrane distillation (MD) has garnered increasing scientific interest. This enables the exploration of state-of-the-art nano-enabled MD membranes with desirable properties, which significantly improve the efficiency and reliability of the MD process and open up opportunities for achieving a sustainable water-energy-environment (WEE) nexus. This comprehensive review provides broad coverage and in-depth analysis of recent innovations in nano-enabled MD membranes, focusing on their role in achieving desirable properties, such as strong liquid-repellence, high resistance to scaling, fouling, and wetting, as well as efficient self-heating and self-cleaning functionalities. The recent developments in nano-enhanced photothermal-catalytic applications for water-energy co-generation within a single MD system are also discussed. Furthermore, the bottlenecks are identified that impede the scale-up of nanoenhanced MD membranes and a future roadmap is proposed for their sustainable commercialiation. This holistic overview is expected to inspire future research and development efforts to fully harness the potential of nano-enabled MD membranes to achieve sustainable integration of water, energy, and the environment.

Preparation and Characterization of Electrospun EVOH/Ti3C2 Composite Fibers

In this work, the EVOH/Ti3C2 composite fibers were prepared via electrospinning and the effect of added Ti3C2 on the structure and properties of electrospun EVOH fibrous membranes was further investigated. The morphology, crystal structure, thermal properties, wettability, tensile properties, as well as air permeability and water vapor permeability of as-prepared EVOH/Ti3C2 composite fibers were studied. The Ti3C2 is uniformly loaded onto the surface and inside the composite fiber and affects the fiber diameters. Furthermore, The Ti3C2 self-orients along the fiber axis and does not change the crystal structure of the electrospun EVOH fibers, improving the crystallinity and thermal stability of the electrospun EVOH/Ti3C2 fibrous membranes. With the increase in the Ti3C2 concentration in the electrospinning polymer solution, the addition of Ti3C2 not only rapidly improves the wettability of the fibrous membranes, but also enhances their air permeability, compared with the pristine electrospun EVOH fibrous membranes. The experimental results provide theoretical guidance for the preparation of Ti3C2 composite fibers, and also expand the application of electrospun EVOH and EVOH/Ti3C2 fibrous membranes.

Stepless IR Chromism in Ti3 C2 Tx MXene Tuned by Interlayer Water Molecules

Real-time control over infrared (IR) radiation of objects is highly desired in a variety of areas such as personal thermal regulation and IR camouflage. This requires the dynamic modulation of IR emissivity in a stepless manner over a wide range (>50%), which remains a daunting challenge. Here, an emissivity modulation phenomenon is reported in stacked 2D Ti3 C2 Tx MXene nanosheets, from 12% to 68% as the intercalation/discharging of water molecules within the interlayers. The intercalation of water molecules dynamically changes the electronic properties and the complex permittivity in IR frequencies of Ti3 C2 Tx . This emissivity modulation is a stepless and reversible process without the assistance of any external energy input. Further, intercalating cellulose nanofibers into the Ti3 C2 Tx interlayers makes this dynamic process highly repeatable. Last, a sweat-responsive adaptive textile that can improve thermal comfort of human body under changes in metabolic rates and environmental conditions is demonstrated, showing great potential of this mechanism in passive on-demand radiation modulation.

MXene/zinc ion embedded agar/sodium alginate hydrogel for rapid and efficient sterilization with photothermal and chemical synergetic therapy

Bacterial infections can significantly impair wound healing. Therefore, it is essential to develop wound dressings with high antimicrobial activity. Hydrogels are often used as wound dressings due to their excellent physicochemical properties. Herein, by cross linking sodium alginate (SA), agar (AG) with Ti3C2Tx MXene and Zinc ions (Zn2+), a biosafe composite hydrogel (MSG-Zn2+) was developed for fast and efficient sterilization treatment. The excellent photothermal properties of Ti3C2Tx MXene and the chemical antimicrobial activity of Zn2+ enable synergistic photothermal therapy (PTT)/chemical therapy in NIR biowindow with reduced power density and improved antimicrobial efficiency. More importantly, the incorporation of Zn2+ can enhance the effective contact between the hydrogel and bacteria, benefiting both photothermal and chemical antibacteria. In vitro antibacterial experiments showed that MSG-Zn2+ has a broad-spectrum antibacterial effect against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). Cellular experiments showed that the hydrogel had excellent biocompatibility and the released Zn2+ stimulated cell migration. In addition, the prepared MSG-Zn2+ hydrogel has other advantages such as hydrophilic, high swelling, simple and low cost preparation, which meets the requirements of an economical wound dressing. This proposed work shows that this composite hydrogel MSG-Zn2+ has great potential for practical antimicrobial wound dressing applications.

MXene/Cellulose Composite Cloth for Integrated Functions (if-Cloth) in Personal Heating and Steam Generation

Given the abundant solar light available on our planet, it is promising to develop an advanced fabric capable of simultaneously providing personal thermal management and facilitating clean water production in an energy-efficient manner. In this study, we present the fabrication of a photothermally active, biodegradable composite cloth composed of titanium carbide MXene and cellulose, achieved through an electrospinning method. This composite cloth exhibits favorable attributes, including chemical stability, mechanical performance, structural flexibility, and wettability. Notably, our 0.1-mm-thick composite cloth (RC/MXene IV) raises the temperature of simulated skin by 5.6 °C when compared to a commercially available cotton cloth, which is five times thicker under identical ambient conditions. Remarkably, the composite cloth (RC/MXene V) demonstrates heightened solar light capture efficiency (87.7%) when in a wet state instead of a dry state. Consequently, this cloth functions exceptionally well as a high-performance steam generator, boasting a superior water evaporation rate of 1.34 kg m-2 h-1 under one-sun irradiation (equivalent to 1000 W m-2). Moreover, it maintains its performance excellence in solar desalination processes. The multifunctionality of these cloths opens doors to a diverse array of outdoor applications, including solar-driven water evaporation and personal heating, thereby enriching the scope of integrated functionalities for textiles.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s42765-023-00345-w.

Dual Localized Surface Plasmon Resonance effect enhances Nb2AlC/Nb2C MXene thermally coupled photocatalytic reduction of CO2 hydrogenation activity

Nb2AlC/Nb2C MXene (NAC/NC) heterojunction photocatalysts with Schottky junctions were obtained by selective etching of the Al layer, resulting in 146.25 μmol·g-1 electrons and 15.28 μmol·g-1 holes stored in the heterojunction. The average conversion of NAC/NC thermally coupled photocatalytic reduction of CO2 under the simulated solar irradiation reached 110.15 μmol⋅g-1⋅h-1, and the CO selectivity reached over 92%, which was 1.49 and 1.74 times higher than that of pure Nb2AlC and Nb2C MXene, respectively. After light excitation, the localized surface plasmon resonance (LSPR) effect of holes distributed on the surface of Nb2C MXene crystals in the heterojunction will form high-energy thermal holes to dissociate H2 to H+ and reduce CO2 to form H2O at the same time. The high-energy electrons formed by the LSPR effect of Nb2C MXene and the conduction band electrons generated by the photoexcitation of Nb2C MXene can be migrated to Nb2AlC under the action of the interfacial Schottky junction to supplement the electrons needed for the LSPR effect of Nb2AlC, which continuously forms high-energy hot electrons to convert the adsorbed CO2 into *CO2-, b-HCO3, and HCOO. Subsequently, HCOO releases ⋅OH in a cyclic reaction to continuously reduce to form CO. The dual LSPR effect of Nb2AlC and Nb2C MXene is used to enhance the hydrogenation activity of thermally coupled photocatalytic reduction of CO2, which provides a new research idea for the application of MXene in thermally coupled photoreduction of CO2.

Thermally Conductive MXene

MXene materials, which consist of nitrides, carbides, or carbonitrides of transition metals, possess a distinctive multilayered structure resulting from the specific etching of the "A" layer from MAX phase precursors. This unique structure allows for tunable properties through intercalation and surface modification. Beyond their structural novelty, MXenes exhibit exceptional thermal conductivity, mechanical resilience, and versatile surface functionalization capabilities, rendering them highly versatile for a wide range of applications. They are particularly renowned for their multifaceted utility and are emerging as outstanding candidates in applications requiring robust thermal conductivity. MXenes, when integrated into textile, fiber, and film forms, have gained increasing relevance in fields where efficient heat management is essential. This work provides a comprehensive exploration of MXene materials, delving into their inherent structure and thermal properties. This Perspective places particular emphasis on their crucial role in efficient heat dissipation, which is vital for the development of wearable heaters and related technologies. Engineered compounds such as MXenes have become indispensable for personal and industrial heating applications, and the advancement of wearable electronic devices necessitates heaters with specific properties, including transparency, mechanical reliability, and adaptability. Recent advancements in emergent thermally conductive MXene compounds are discussed in this study, shedding light on their potential contributions across various domains, including wearable heaters and biosensors for healthcare and environmental monitoring. Furthermore, the versatile nature of MXene materials extends to their application in interfacial solar steam generation, representing a breakthrough approach for solar water desalination. This multifaceted utility underscores the vast potential of MXenes in addressing various pressing challenges.

Unraveling the optoelectronic properties of CoSbx intrinsic selective solar absorber towards high-temperature surfaces

The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers (SSAs) to maximize solar energy to heat conversion, which is critical to several advanced applications. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption. Typically, intrinsic materials exhibit high performances when integrated into complex multilayered solar absorber systems due to their limited spectral selectivity and solar absorption. In this study, we propose CoSbx (2 < x < 3) as a new exceptionally efficient SSA. Here we demonstrate that the low bandgap nature of CoSbx endows broadband solar absorption (0.96) over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region, resulting in a remarkable intrinsic spectral solar selectivity of 5.3. Under 1 sun illumination, the heat concentrates on the surface of the CoSbx thin film, and an impressive temperature of 101.7 °C is reached, demonstrating the highest value among reported intrinsic SSAs. Furthermore, the CoSbx was tested for solar water evaporation achieving an evaporation rate of 1.4 kg m-2 h-1. This study could expand the use of narrow bandgap semiconductors as efficient intrinsic SSAs with high surface temperatures in solar applications.

A Simple and Effective Physical Ball-Milling Strategy to Prepare Super-Tough and Stretchable PVA@MXene@PPy Hydrogel for Flexible Capacitive Electronics

Biomimetic flexible electronics for E-skin have received increasing attention, due to their ability to sense various movements. However, the development of smart skin-mimic material remains a challenge. Here, a simple and effective approach is reported to fabricate super-tough, stretchable, and self-healing conductive hydrogel consisting of polyvinyl alcohol (PVA), Ti3 C2 Tx MXene nanosheets, and polypyrrole (PPy) (PMP hydrogel). The MXene nanosheets and Fe3+ serve as multifunctional cross-linkers and effective stress transfer centers, to facilitate a considerable high conductivity, super toughness, and ultra-high stretchability (elongation up to 4300%) for the PMP hydrogel with. The hydrogels also exhibit rapid self-healing and repeatable self-adhesive capacity because of the presence of dynamic borate ester bond. The flexible capacitive strain sensor made by PMP hydrogel shows a relatively broad range of strain sensing (up to 400%), with a self-healing feature. The sensor can precisely monitor various human physiological signals, including joint movements, facial expressions, and pulse waves. The PMP hydrogel-based supercapacitor is demonstrated with a high capacitance retention of ≈92.83% and a coulombic efficiency of ≈100%.

Rare-earth hydroxide/MXene hybrid: a promising agent for near-infrared photothermy and magnetic resonance imaging

Layered gadolinium hydroxide (LGdH) and Ti3C2 monolayers were assembled into a LGdH/Ti3C2 (GTC) hybrid. The hybrid demonstrated enhanced near-infrared (NIR) light absorption properties and superior photothermal performance. Moreover, the GTC hybrid achieved an excellent T1-weighted magnetic resonance imaging (MRI) effect.

Synergistic Dual-Mechanism Localized Heat Channeling and Spectrum-Tailored Liquid Metal Hydrogels for Efficient Solar Water Evaporation and Desalination

Photothermal hydrogels featuring broadband light absorption abilities and highly hydrated networks provide an appealing mass-energy transfer platform for water evaporation by using solar energy. However, the targeted delivery of solar heat energy to power the water evaporation process remains challenging. Herein, enlightened by metal-phenolic coordination chemistry and camouflaged architecture, photothermal hydrogels with dual-mechanism vaporization structure are tactfully designed via a rational interfacial engineering and integration strategy to enable near-µm heat confinement and highly efficient light-to-heat conversion ability. The spectrum-tailored liquid metal droplet (LMGAs-FeIII ) and optimized carbon-wrapped silver nanowire sponge (Ag@C750 ) are integrally built as photothermal promotors/channels and jointly embedded into a highly hydratable poly(vinyl alcohol) hydrogel, denoted as PALGH, to synergistically boost water molecule activation and interfacial vaporization behavior by triggering robust photothermal performance. As a result, under one sun irradiation, the all-embracing PALGH hydrogel evaporation system achieves a brine evaporation rate to a high level of 3.47 kg m-2 h-1 , and >19 L m-2 clean water of PALGH is ideally delivered daily when purifying natural seawater. This work offers not only a rational design principle to create sophisticated photothermal materials but also replenishes insight into solar heat generation and water transportation in a cross-media system.

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

Maintaining human thermal comfort in the cold outdoors is crucial for diverse outdoor activities, e.g., sports and recreation, healthcare, and special occupations. To date, advanced clothes are employed to collect solar energy as a heat source to stand cold climates, while their dull dark photothermal coating may hinder pragmatism in outdoor environments and visual sense considering fashion. Herein, tailor-made white webs with strong photothermal effect are proposed. With the embedding of cesium-tungsten bronze (Csx WO3 ) nanoparticles (NPs) as additive inside nylon nanofibers, these webs are capable of drawing both near-infrared (NIR) and ultraviolet (UV) light in sunlight for heating. Their exceptional photothermal conversion capability enables 2.5-10.5 °C greater warmth than that of a commercial sweatshirt of six times greater thickness under different climates. Remarkably, this smart fabric can increase its photothermal conversion efficiency in a wet state. It is optimal for fast sweat or water evaporation at human comfort temperature (38.5 °C) under sunlight, and its role in thermoregulation is equally important to avoid excess heat loss in wilderness survival. Obviously, this smart web with considerable merits of shape retention, softness, safety, breathability, washability, and on-demand coloration provides a revolutionary solution to realize energy-saving outdoor thermoregulation and simultaneously satisfy the needs of fashion and aesthetics.

Optically Active MXenes in Van der Waals Heterostructures

The vertical integration of distinct 2D materials in van der Waals (vdW) heterostructures provides the opportunity for interface engineering and modulation of electronic as well as optical properties. However, scarce experimental studies reveal many challenges for vdW heterostructures, hampering the fine-tuning of their electronic and optical functionalities. Optically active MXenes, the most recent member of the 2D family, with excellent hydrophilicity, rich surface chemistry, and intriguing optical properties, are a novel 2D platform for optoelectronics applications. Coupling MXenes with various 2D materials into vdW heterostructures can open new avenues for the exploration of physical phenomena of novel quantum-confined nanostructures and devices. Therefore, the fundamental basis and recent findings in vertical vdW heterostructures composed of MXenes as a primary component and other 2D materials as secondary components are examined. Their robust designs and synthesis approaches that can push the boundaries of light-harvesting, transition, and utilization are discussed, since MXenes provide a unique playground for pursuing an extraordinary optical response or unusual light conversion features/functionalities. The recent findings are finally summarized, and a perspective for the future development of next-generation vdW multifunctional materials enriched by MXenes is provided.

Waterproof, Light Responsive, and Highly Sensitive Fabric Strain Sensor for Flexible Electronics

Corrosion resistant, durable, and lightweight flexible strain sensor with multiple functionalities is an urgent demand for modern flexible wearable devices. However, currently developed wearable devices are still limited by poor environmental adaptability and functional singleness. In this work, a conductive fabric with multifunctionality in addition to sensing was successfully prepared by assembling zero dimensional silver nanoparticles (AgNPs) and one-dimensional carbon nanotubes (CNTs) layer by layer on the surface of the elastic polypropylene nonwoven fabric (named PACS fabric). Polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene (SEBS) added as binder materials favored strong interaction between conductive fillers and the fabric. Benefiting from the synergistic interaction among the conductive fillers with different dimensions and the fabric, the strain sensor based on the conductive fabric showed high sensitivity (GF up to 8064), wide detection range (0-200%), and excellent stability and durability (more than 10000 stretch-release cycles). Besides, the prepared conductive fabric showed superhydrophobicity (water contact angle = 154°) with excellent durability. This ensured the performance stability of the fabric sensor in harsh environments. At the same time, the fabric also showed excellent photothermal conversion performance (90 °C at a power density of 0.2 W/cm2 within 20 s). The PACS fabric strain sensor proved excellent performance and environmental adaptability, revealing great potential to be applied in human motion monitoring, self-cleaning, biomedicine, and other fields.

Pattern design of a liquid metal-based wearable heater for constant heat generation under biaxial strain

As the wearable heater is increasingly popular due to its versatile applications, there is a growing need to improve the tensile stability of the wearable heater. However, maintaining the stability and precise control of heating in resistive heaters for wearable electronics remains challenging due to multiaxial dynamic deformation with human motion. Here, we propose a pattern study for a circuit control system without complex structure or deep learning of the liquid metal (LM)-based wearable heater. The LM direct ink writing (DIW) method was used to fabricate the wearable heaters in various designs. Through the study about the pattern, the significance of input power per unit area for steady average temperature with tension was proven, and the directionality of the pattern was shown to be a factor that makes feedback control difficult due to the difference in resistance change according to strain direction. For this issue, a wearable heater with the same minimal resistance change regardless of the tension direction was developed using Peano curves and sinuous pattern structure. Lastly, by attaching to a human body model, the wearable heater with the circuit control system shows stable heating (52.64°C, with a standard deviation of 0.91°C) in actual motion.

Clearly transparent and air-permeable nanopaper with porous structures consisting of TEMPO-oxidized cellulose nanofibers

Optically transparent materials that are air permeable have potentially numerous applications, including in wearable devices. From the perspective of sustainable development, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers with widths of 3-4 nm have attracted considerable attention as starting materials for the preparation of clearly transparent nanofiber paper (denoted as conventional nanopaper). However, conventional nanopaper that is prepared from a water dispersion of TEMPO-oxidized cellulose nanofibers by direct drying exhibits poor air permeability owing to its densely packed layered structure. In this study, we prepared a clearly transparent and air-permeable nanopaper by applying filtration-based solvent exchange from high-surface-tension water to low-surface-tension ethanol and hexane, followed by drying under continuous vacuum filtration. The resulting hexane-exchanged nanopaper had a porous structure with individually dispersed and thin nanofiber networks and interlayer pore spaces. Owing to the tailored porous structures, the hexane-exchanged nanopaper provides similar clear transparency (total light transmittance and haze at 600 nm: 92.9% and 7.22%, respectively) and 10⁶ times higher air permeability (7.8 × 10⁶ mL μm m^-2 day^-1 kPa^-1) compared to the conventional nanopaper. This study will facilitate the development of clearly transparent and air-permeable nanopapers to extend their functional applications.

Functional Materials and Innovative Strategies for Wearable Thermal Management Applications

Highlights

This article systematically reviews the thermal management wearables with a specific emphasis on materials and strategies to regulate the human body temperature. Thermal management wearables are subdivided into the active and passive thermal managing methods. The strength and weakness of each thermal regulatory wearables are discussed in details from the view point of practical usage in real-life.

Abstract

Thermal management is essential in our body as it affects various bodily functions, ranging from thermal discomfort to serious organ failures, as an example of the worst-case scenario. There have been extensive studies about wearable materials and devices that augment thermoregulatory functionalities in our body, employing diverse materials and systematic approaches to attaining thermal homeostasis. This paper reviews the recent progress of functional materials and devices that contribute to thermoregulatory wearables, particularly emphasizing the strategic methodology to regulate body temperature. There exist several methods to promote personal thermal management in a wearable form. For instance, we can impede heat transfer using a thermally insulating material with extremely low thermal conductivity or directly cool and heat the skin surface. Thus, we classify many studies into two branches, passive and active thermal management modes, which are further subdivided into specific strategies. Apart from discussing the strategies and their mechanisms, we also identify the weaknesses of each strategy and scrutinize its potential direction that studies should follow to make substantial contributions to future thermal regulatory wearable industries.

Radiation synthesis of MXene/Ag nanoparticle hybrids for efficient photothermal conversion of polyurethane films

Flexible conductive films based on light-to-heat conversion are promising for the next-generation electronic devices. A flexible waterborne polyurethane composite film (PU/MA) with excellent photothermal conversion performance was obtained by combination of PU and silver nanoparticle decorated MXene (MX/Ag). The silver nanoparticles (AgNPs) uniformly decorated on the MXene surface by γ-ray irradiation induced reduction. Because of the synergistic effect of MXene with outstanding light-to-heat conversion efficiency and the AgNPs with plasmonic effect, the surface temperature of the PU/MA-II (0.4%) composite with lower MXene content increased from room temperature to 60.7 °C at 5 min under 85 mW cm^-2 light irradiation. Besides, the tensile strength of PU/MA-II (0.4%) increased from 20.9 MPa (pure PU) to 27.5 MPa. The flexible PU/MA composite film shows great potential in the field of thermal management of flexible wearable electronic devices.

A Review on Interface Engineering of MXenes for Perovskite Solar Cells

With an excellent power conversion efficiency of 25.7%, closer to the Shockley-Queisser limit, perovskite solar cells (PSCs) have become a strong candidate for a next-generation energy harvester. However, the lack of stability and reliability in PSCs remained challenging for commercialization. Strategies, such as interfacial and structural engineering, have a more critical influence on enhanced performance. MXenes, two-dimensional materials, have emerged as promising materials in solar cell applications due to their metallic electrical conductivity, high carrier mobility, excellent optical transparency, wide tunable work function, and superior mechanical properties. Owing to different choices of transition elements and surface-terminating functional groups, MXenes possess the feature of tuning the work function, which is an essential metric for band energy alignment between the absorber layer and the charge transport layers for charge carrier extraction and collection in PSCs. Furthermore, adopting MXenes to their respective components helps reduce the interfacial recombination resistance and provides smooth charge transfer paths, leading to enhanced conductivity and operational stability of PSCs. This review paper aims to provide an overview of the applications of MXenes as components, classified according to their roles as additives (into the perovskite absorber layer, charge transport layers, and electrodes) and themselves alone or as interfacial layers, and their significant importance in PSCs in terms of device performance and stability. Lastly, we discuss the present research status and future directions toward its use in PSCs.

Photothermal Nanomaterials: A Powerful Light-to-Heat Converter

All forms of energy follow the law of conservation of energy, by which they can be neither created nor destroyed. Light-to-heat conversion as a traditional yet constantly evolving means of converting light into thermal energy has been of enduring appeal to researchers and the public. With the continuous development of advanced nanotechnologies, a variety of photothermal nanomaterials have been endowed with excellent light harvesting and photothermal conversion capabilities for exploring fascinating and prospective applications. Herein we review the latest progresses on photothermal nanomaterials, with a focus on their underlying mechanisms as powerful light-to-heat converters. We present an extensive catalogue of nanostructured photothermal materials, including metallic/semiconductor structures, carbon materials, organic polymers, and two-dimensional materials. The proper material selection and rational structural design for improving the photothermal performance are then discussed. We also provide a representative overview of the latest techniques for probing photothermally generated heat at the nanoscale. We finally review the recent significant developments of photothermal applications and give a brief outlook on the current challenges and future directions of photothermal nanomaterials.

Organic Photothermal Cocrystals: Rational Design, Controlled Synthesis, and Advanced Application

Organic photothermal cocrystals, integrating the advantages of intrinsic organic cocrystals and the fascinating photothermal conversion ability, hold attracted considerable interest in both basic science and practical applications, involving photoacoustic imaging, seawater desalination, and photothermal therapy, and so on. However, these organic photothermal cocrystals currently suffer individual cases discovered step by step, as well as the deep and systemic investigation in the corresponding photothermal conversion mechanisms is rarely carried out, suggesting a huge challenge for their further developments. Therefore, it is urgently necessary to investigate and explore the rational design and synthesis of high-performance organic photothermal cocrystals for future applications. This review first and systematically summarizes the organic photothermal cocrystal in terms of molecular classification, the photothermal conversion mechanism, and their corresponding applications. The timely interpretation of the cocrystal photothermal effect will provide broad prospects for the purposeful fabrication of excellent organic photothermal cocrystals toward great efficiency, low cost, and multifunctionality.

Electrostatically Assisted Construction Modified MXene-IL-Based Nanofluids for Photothermal Conversion

Solar energy, as renewable energy, has paid extensive attention for solar thermal utilization due to its unique characteristics such as rich resources, easy access, clean, and pollution-free. Among them, solar thermal utilization is the most extensive one. Nanofluid-based direct absorption solar collectors (DASCs), as an important alternative method, can further improve the solar thermal efficiency. Notably, the stability of photothermal conversion materials and flowing media is critical to the performance of DASC. Herein, we first proposed novel Ti3C2Tx-IL-based nanofluids by the electrostatic interaction, which consists of functional Ti3C2Tx modified with PDA and PEI as a photothermal conversion material and ionic liquid with low viscosity as the flow medium. Ti3C2Tx-IL-based nanofluids exhibit excellent cycle stability, wide spectrum, and efficient solar energy absorption performance. Besides, Ti3C2Tx-IL-based nanofluids maintain liquid state in a range of -80 to 200 °C, and its viscosity was as low as 0.3 Pa·s at 0 °C. Moreover, the equilibrium temperature of Ti3C2Tx@PDA-IL at a very low mass fraction of 0.04% reached 73.9 °C under 1 Sun, indicating an excellent photothermal conversion performance. Furthermore, the application of nanofluids in photosensitive inks has been preliminarily explored, which is expected to play a role in the fields of injectable biomedical materials and photo/electric double-generation thermal and hydrophobic anti ice coatings.

Multifunctional MoSe2 @MXene Heterostructure-Decorated Cellulose Fabric for Wearable Thermal Therapy

A booming demand for wearable electronic devices urges the development of multifunctional smart fabrics. However, it is still facing a challenge to fabricate multifunctional smart fabrics with satisfactory mechanical property, excellent Joule heating performance, highly efficient photothermal conversion, outstanding electromagnetic shielding effectiveness, and superior anti-bacterial capability. Here, a MoSe₂ @MXene heterostructure-based multifunctional cellulose fabric is fabricated by depositing MXene nanosheets onto cellulose fabric followed by a facile hydrothermal method to grow MoSe₂ nanoflakes on MXene layers. A low-voltage Joule heating therapy platform with rapid Joule heating response (up to 230 °C in 25 s at a supplied voltage of 4 V) and stable performance under repeated bending cycles (up to 1000 cycles) is realized. Besides, the multifunctional fabric also exhibits excellent photothermal performance (up to 130 °C upon irradiation for 25 s with a light intensity of 400 mW cm^-2 ), outstanding electromagnetic interference shielding effectiveness (37 dB), and excellent antibacterial performances (>90% anti-bacterial rate toward Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). This work offers an efficient avenue to fabricate multifunctional wearable thermal therapy devices for mobile healthcare and personal thermal management.

Highly Flexible Ti3C2Tx MXene/Waterborne Polyurethane Membranes for High-Efficiency Terahertz Modulation with Low Insertion Loss

The dynamic control of terahertz (THz) wave transmission on flexible functional materials is a fundamental building block for wearable electronics and sensors in the THz range. However, achieving high-efficiency THz modulation and low insertion loss is a great challenge while maintaining the excellent flexibility and stretchability of the materials. Herein, we report a Ti₃C₂T_x MXene/waterborne polyurethane (WPU) membrane prepared by a vacuum-assisted filtration method, which exhibits excellent THz modulation properties across stretching. The hydrophilic Ti₃C₂T_x MXene and WPU enable the uniform 3D distribution of Ti₃C₂T_x MXene in the WPU matrix. Particularly, the stretchability with the maximum strain of the membranes can reach 200%, accompanied by dynamic tuning of THz transmittance for more than 90% and an insertion loss as low as -4.87 dB. The giant THz modulation continuously decreases with MXene content per unit area, accompanied by a lower density of the MXene interface and diminished THz absorption during stretching. Such a design opens a pathway for achieving flexible THz modulators with a high modulation depth and low insertion loss, which would be used for THz flexible and wearable devices.

Transparent sunlight-activated antifogging metamaterials

Counteracting surface fogging to maintain surface transparency is important for a variety of applications including eyewear, windows and displays. Energy-neutral, passive approaches predominantly rely on engineering the surface wettability, but suffer from non-uniformity, contaminant deposition and lack of robustness, all of which substantially degrade durability and performance. Here, guided by nucleation thermodynamics, we design a transparent, sunlight-activated, photothermal coating to inhibit fogging. The metamaterial coating contains a nanoscopically thin percolating gold layer and is most absorptive in the near-infrared range, where half of the sunlight energy resides, thus maintaining visible transparency. The photoinduced heating effect enables sustained and superior fog prevention (4-fold improvement) and removal (3-fold improvement) compared with uncoated samples, and overall impressive performance, indoors and outdoors, even under cloudy conditions. The extreme thinness (~10 nm) of the coating-which can be produced by standard, readily scalable fabrication processes-enables integration beneath other coatings, rendering it durable even on highly compliant substrates.

Facile fabrication of a novel self-healing and flame-retardant hydrogel/MXene coating for wood

To improve flame retardancy of wood, a novel high-water-retention and self-healing polyvinyl alcohol/phytic acid/MXene hydrogel coating was developed through facile one-pot heating and freeze-thaw cycle methods, and then painted on wood surface. The coating exhibit excellent self-healing property and significantly enhanced water-retention property (water content ≥ 90 wt%), due to the increased hydrogen bonds within the coating system with the presence of MXene nanosheets. Compared to pristine wood, the flame retardancy of coated wood is greatly improved, such as passed V0 rating in UL-94 test, increasing time to ignition (TTI, from 32 to 69 s), and decreased heat release rate and total heat release by 41.6% and 36.14%. The cooling effect and large thermal capacity of high-water-retention hydrogel, and physical barrier effects for flammable gas products, heat and oxygen by MXene nanosheets and the compact char layer formed during combustion play key roles in the flame retardancy enhancements of the wood. High thermal stability of MXene nanosheets is another beneficial factor. The detailed flame-retardant and self-healing mechanisms were proposed.

Solar-Driven Reversible Hydrogen Storage

The lack of safe and efficient hydrogen storage is a major bottleneck for large-scale application of hydrogen energy. Reversible hydrogen storage of light-weight metal hydrides with high theoretical gravimetric and volumetric hydrogen density is one ideal solution but requires extremely high operating temperature with large energy input. Herein, taking MgH₂ as an example, a concept is demonstrated to achieve solar-driven reversible hydrogen storage of metal hydrides via coupling the photothermal effect and catalytic role of Cu nanoparticles uniformly distributed on the surface of MXene nanosheets (Cu@MXene). The photothermal effect of Cu@MXene, coupled with the "heat isolator" role of MgH₂ indued by its poor thermal conductivity, effectively elevates the temperature of MgH₂ upon solar irradiation. The "hydrogen pump" effect of Ti and TiH_x species that are in situ formed on the surface of MXene from the reduction of MgH₂ , on the other hand, plays a catalytic role in effectively alleviating the kinetic barrier and hence decreasing the operating temperature required for reversible hydrogen adsorption and desorption of MgH₂ . Based on the combination of photothermal and catalytic effect of Cu@MXene, a reversible hydrogen storage capacity of 5.9 wt% is achieved for MgH₂ after 30 cycles using solar irradiation as the only energy source.

Flexible Torsional Photoactuators Based on MXene-Carbon Nanotube-Paraffin Wax Films

A flexible actuator, which can convert external stimuli to mechanical motion, is an essential component of every soft robot and determines its performance. As a novel two-dimensional material, MXene has been used to fabricate flexible actuators due to its excellent physical properties. Although MXene-based actuators exhibit excellent actuation performance, their bending deformation is solely due to the in-plane isotropy of the MXene film, and an MXene torsional actuator has not been reported. This study presents a flexible torsional actuator based on an MXene-carbon nanotube (CNT)-paraffin wax (PW) film. In this actuator, the MXene thin film acts as a light absorption layer with wavelength selectivity, superaligned CNT provides structural anisotropy for the composite film, and PW acts as the active layer. The chirality and helical structure of the actuator could be tuned by the orientation of the CNT film. Such an actuator delivers excellent actuation performance, including high work density (∼1.2 J/cm³), low triggering power (77 mW/cm²), high rotational speed (320°/s), long lifetime (30,000 cycles), and wavelength selectivity. Inspired by vines, we used the torsional actuator as a spiral grabber, which lifted an object that weighs 20 times more than the actuator. The high-performance torsional actuator would be potentially used as a noncontact sensor, rotary motor, and grabbing tool in the soft robot system.

A study on the role of plasmonic Ti3C2Tx MXene in enhancing photoredox catalysis

Engineering the spatial separation and transfer of photogenerated charge carriers has been one of the most enduring research topics in the field of photocatalysis due to its crucial role in determining the performances of photocatalysts. Herein, as a proof-of-concept, Ti₃C₂T_x MXene is coupled with a typical heterojunction of TiO₂@CdS through a co-assembly strategy to boost electron pumping towards improving the photocatalytic efficiency. In addition to the band alignment-mediated electron transfer in TiO₂@CdS-Ti₃C₂T_x heterojunctions, the plasmon-induced electric field enhancement of Ti₃C₂T_x is found to cooperate with the electron-reservoir role of Ti₃C₂T_x to extract photoinduced electrons. The synergistic dual functions of Ti₃C₂T_x promote multichannel electron transfer in TiO₂@CdS-Ti₃C₂T_x hybrids to improve the photocatalytic efficiency. These results intuitively show that there is a wide scope to manipulate the spatial separation and transfer of photoinduced electrons by cultivating the fertile ground of Ti₃C₂T_x toward boosting the efficiency of solar-to-chemical conversion.

Cellulose nanofiber/molybdenum disulfide aerogels for ultrahigh photothermal effect

The photothermal materials have a broad range of applications in crude oil spills treatment, desalination, and photothermal therapy. However, the rational construction of aerogels with exceptional photothermal performance is highly desired yet still challenging. Herein, a class of stable aerogels comprised of molybdenum disulfide (MoS₂) nanoflowers and cellulose nanofibers (CNFs) was fabricated, affording extraordinary light-to-heat energy conversion capability. Benefiting from the intercalated porous structure, the resultant cellulose nanofibers/molybdenum disulfide (CNF/MoS₂) aerogels deliver an ultrahigh temperature output up to 260.4 °C with near infrared (NIR) laser power densities of 0.8 W cm^-2. Remarkably, when NIR laser power density increased to 1.0 W cm^-2, the aerogels began to burn, achieving the superhigh surface temperature of ∼ 690 °C. The combustion process of CNF/MoS₂ composite aerogels was evaluated in detail. Therefore, this work provides experiment evidence and theoretical basis for the rational applications of photothermal materials at high temperature in future.

Integrating Dual-Interfacial Liquid Metal Based Nanodroplet Architectures and Micro-Nanostructured Engineering for High Efficiency Solar Energy Harvesting

Broadband strong absorption of solar light over a wide range of angles, low heat loss, and excellent structural reliability are of significance for enhancing solar harvesting of photothermal materials; however, it remains a challenge to achieve these attributes simultaneously. Herein, a tailored photothermal composite nanodroplet (LMP-rGO) featured with dual-interface, which comprises liquid metal (LM) core with polydopamine (PDA) photothermal middle layer of tunable thickness and reduced graphene oxide (rGO) shell, is particularly prepared. Thermal-insulating PDA coating and light-absorbing carbonaceous shell allow it to synergistically suppress heat loss and reinforce photon absorptivity. To maximize photothermal conversion and photon harvesting yield on solar light, inspired by light trapping architecture, a three-dimensional (3D) stepped micropyramid grating array framework is tactfully designed to ameliorate light coupling. Utilizing the scalability and cost-effectiveness of the poly(vinyl alcohol) (PVA), the flexible 3D-structured PVA/LMP-rGO absorbers are successfully constructed via a controllable casting molding strategy. As a proof-of-concept, the developed micrograting absorber exhibits a desirable combination of strong broadband selective light absorption (94.9% for parallel to the grating direction and 97.3% for perpendicular to the grating direction), superior photothermal conversion effect (89.4%), high heat flux density, and fascinating mechanical properties. Also, an efficient and steady solar-driven thermoelectric generator (STEG) system for real-time solar-heat-electric conversion, with its high peak power density of 245.9 μW cm^-2 under one sun irradiation, is further displayed, making an important step to rationally design LM-based nanocomposite droplets for solar energy harvesting.

Bond engineering of molecular ferroelectrics renders soft and high-performance piezoelectric energy harvesting materials

Piezoelectric materials convert mechanical stress to electrical energy and thus are widely used in energy harvesting and wearable devices. However, in the piezoelectric family, there are two pairs of properties that improving one of them will generally compromises the other, which limits their applications. The first pair is piezoelectric strain and voltage constant, and the second is piezoelectric performance and mechanical softness. Here, we report a molecular bond weakening strategy to mitigate these issues in organic-inorganic hybrid piezoelectrics. By introduction of large-size halide elements, the metal-halide bonds can be effectively weakened, leading to a softening effect on bond strength and reduction in polarization switching barrier. The obtained solid solution C₆H₅N(CH₃)₃CdBr₂Cl_0.75I_0.25 exhibits excellent piezoelectric constants (d₃₃ = 367 pm/V, g₃₃ = 3595 × 10⁻³ Vm/N), energy harvesting property (power density is 11 W/m²), and superior mechanical softness (0.8 GPa), promising this hybrid as high-performance soft piezoelectrics.

Improving piezoelectric strain and voltage constant generally compromises piezoelectric performance and mechanical softness. Here, the authors report a bond weakening strategy for organic-inorganic hybrid piezoelectrics and mitigated these issues.

C. D, Karki B, Samatha K, Kim AA, Park M, Pant B. Advancements in MXene-Polymer Nanocomposites in Energy Storage and Biomedical Applications

MXenes are 2D ceramic materials, especially carbides, nitrides, and carbonitrides derived from their parent 'MAX' phases by the etching out of 'A' and are famous due to their conducting, hydrophilic, biocompatible, and tunable properties. However, they are hardly stable in the outer environment, have low biodegradability, and have difficulty in drug release, etc., which are overcome by MXene/Polymer nanocomposites. The MXenes terminations on MXene transferred to the polymer after composite formation makes it more functional. With this, there is an increment in photothermal conversion efficiency for cancer therapy, higher antibacterial activity, biosensors, selectivity, bone regeneration, etc. The hydrophilic surfaces become conducting in the metallic range after the composite formation. MXenes can effectively be mixed with other materials like ceramics, metals, and polymers in the form of nanocomposites to get improved properties suitable for advanced applications. In this paper, we review different properties like electrical and mechanical, including capacitances, dielectric losses, etc., of nanocomposites more than those like Ti3C2Tx/polymer, Ti3C2/UHMWPE, MXene/PVA-KOH, Ti3C2Tx/PVA, etc. along with their applications mainly in energy storing and biomedical fields. Further, we have tried to enlist the MXene-based nanocomposites and compare them with conducting polymers and other nanocomposites. The performance under the NIR absorption seems more effective. The MXene-based nanocomposites are more significant in most cases than other nanocomposites for the antimicrobial agent, anticancer activity, drug delivery, bio-imaging, biosensors, micro-supercapacitors, etc. The limitations of the nanocomposites, along with possible solutions, are mentioned.