Scalable production of structurally colored composite films by shearing supramolecular composites of polymers and colloids.

Structurally colored composite films, composed of orderly arranged colloids in polymeric matrix, are emerging flexible optical materials, but their production is bottlenecked by time-consuming procedures and limited material choices. Here, we present a mild approach to producing large-scale structurally colored composite films by shearing supramolecular composites composed of polymers and colloids with supramolecular interactions. Leveraging dynamic connection and dissociation of supramolecular interactions, shearing force stretches the polymer chains and drags colloids to migrate directionally within the polymeric matrix with reduced viscous resistance. We show that meter-scale structurally colored composite films with iridescence color can be produced within several minutes at room temperature. Significantly, the tunability and diversity of supramolecular interactions allow this shearing approach extendable to various commonly-used polymers. This study overcomes the traditional material limitations of manufacturing structurally colored composite films by shearing method and opens an avenue for mildly producing ordered composites with commonly-available materials via supramolecular strategies.

When Iodine Meets Starch: On-Demand Generation of Photothermal Hydrogels for Mild-Temperature Photothermal-Chemo Disinfection.

As an emerging antibacterial strategy, photothermal disinfection attracts increasing attention due to its advantages of high efficacy, wide pertinence, and non-drug resistance. However, the unavoidable shielding of observation by photothermal components and the possible damage to normal tissue caused by hyperthermia restrict its applications. Herein, we propose a composite hydrogel with the ability of on-demand generation of photothermal components and mild-temperature photothermal disinfection by elegantly tuning the binding and release of iodine and starch. The composite hydrogel is obtained by blending iodine-adsorbed pH-responsive ZIF-8 nanoparticles (NPs) with a starch-based hydrogel matrix. Through a convenient pH response, the composite hydrogel leverages the triple functions of iodine, which serves as a disinfectant and reacts with starch to generate a photothermal agent and color indicator, allowing photothermal-chemotherapy combined disinfection on demand. In vitro antibacterial experiments show that the composite hydrogel can respond to the acidification of the microenvironment caused by bacterial metabolism and produce corresponding color changes, realizing naked-eye observation. Meanwhile, under the combined treatment of heating/I2/Zn2+, the composite hydrogel can completely kill Escherichia coli and Staphylococcus aureus at a mild temperature of ∼41 °C. This study represents a breakthrough in on-demand generation of photothermal hydrogels for mild-temperature photothermal disinfection.

Composite Polyelectrolyte Photothermal Hydrogel with Anti-biofouling and Antibacterial Properties for the Real-World Application of Solar Steam Generation.

Solar steam generation provides a promising and low-cost solution for freshwater production in energy scarcity areas. However, in real-world applications, evaporators are easily affected by microorganism contamination in source water, causing surface corrosion, structural damage, or even invalidation. Developing anti-biofouling and antibacterial evaporators is significant for long-term stable freshwater production. Herein, a composite polyelectrolyte photothermal hydrogel consisting of sulfobetaine methacrylate (SBMA), [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), and polypyrrole (PPy) with anti-biofouling and antibacterial properties is developed. Crediting sufficient ammonium groups and zwitterionic segments, the optimized polyelectrolyte hydrogel exhibits an ∼90% antibacterial ratio against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and effectively controls biological contamination. Under 1.0 kW m-2 solar irradiation, a rapid water evaporation rate of ∼1.690 kg m-2 h-1 and a high solar-to-evaporation efficiency of ∼95.94% are achieved with the photothermal hydrogel. We show that a lab-made setup integrated with the hydrogel can realize ∼0.455 kg m-2 h-1 freshwater production from seawater under natural sunlight. Moreover, the hydrogel exhibits excellent durability with a stable evaporation rate of ∼1.617 kg m-2 h-1 in real seawater for over 6 weeks, making it fullhearted in the real-world application of solar steam generation.

Bioinspired Colloidal Photonic Composites: Fabrications and Emerging Applications.

Organisms in nature have evolved unique structural colors and stimuli-responsive functions for camouflage, warning, and communication over millions of years, which are essential to their survival in harsh conditions. Inspired by these characteristics, colloidal photonic composites (CPCs) composed of colloidal photonic crystals embedded in the polymeric matrix are artificially prepared and show great promise in applications. This review focuses on the summary of building blocks, i.e., colloidal particles and polymeric matrices, and constructive strategies from the perspective of designing CPCs with robust performance and specific functionality. Furthermore, their state-of-the-art applications are also discussed, including colorful coatings, anti-counterfeiting, and regulation of photoluminescence, especially in the field of visualized sensing. Finally, current challenges and potential for future developments in this field are discussed. The purpose of this review is not only to clarify the design principle for artificial CPCs but also to serve as a roadmap for the exploration of next-generation photonic materials.

Bioinspired Janus particles for hydrophobic modification of hydrogels with photothermal antibacterial capability.

Hydrogels have received considerable attention due to their biocompatibility and desirable physical characteristics. Nonetheless, due to their open structure, hydrogels are prone to dehydration in air, resulting in a loss in their elasticity and function. Herein, we report a facile yet effective method for the modification of hydrophobic hydrogel surfaces by using bioinspired amphiphilic Janus silica particles, which are obtained by modifying hydrophilic polydopamine and hydrophobic 1H,1H,2H,2H-perfluorodecanthiol on their two sides via a templating method. With the coating of amphiphilic Janus silica particles, the water contact angles of poly(ethylene imine)-polyacrylamide and polydopamine-polyacrylamide hydrogels significantly increase to 96° and 97°, respectively. Furthermore, we demonstrate that the hydrophobic modification of the hydrogels by Janus silica particles improves the water retention capability, and the overall mechanical properties of bulk hydrogels are not compromised. In addition, we show that hydrogels coated with Janus silica particles not only exhibit hydrophobic surfaces but also have photothermal antibacterial capabilities. Consequently, this study provides a facile method for the fabrication of hydrogels with hydrophobic surfaces, which could potentially be applied to biomedical materials.

Bioinspired Photonic Ionogels as Interactively Visual Ionic Skin with Optical and Electrical Synergy.

With the ever-growing demands for flexible smart interactive electronics, it remains highly desirable yet challenging to design and fabricate interactive ionic skin with multiple signal synergistic outputs. Herein, high-performance photonic ionogels (PIGs) with excellent stability and synergy sensitivity are designed by locking a non-volatile and non-hygroscopic ionic liquid (IL), that is, 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ([EMIm][TFSI]), into photonic elastomers based on polymer networks of poly(ethylene glycol) phenyl ether acrylate (PEGPEA). Through manipulating the degree of crosslinking, PIGs exhibit high sensitivity that can output distinct and intuitive color change in visual with the mechanochromic sensitivity of ≈1.76 nm per percent strain and clear electrical signal with the gauge factor of 1, in response to a tiny stretch of millimeter scale. Thanks to the stable photonic elastomers and IL employed, the PIGs developed in this study exhibit good performance under harsh and complex environmental conditions, including high/low temperature (from -35 °C to 100 °C), dry/wet air, and high vacuum. This study provides a novel strategy for developing integrated, stable, and multifunctional photonic ionogels for ionic skin sensors and flexible interactive devices with synergistically optical and electrical output.

Cationic Photothermal Hydrogels with Bacteria-Inhibiting Capability for Freshwater Production via Solar-Driven Steam Generation.

Solar-driven steam generation has been recognized as a sustainable and low-cost solution to freshwater scarcity using abundant solar energy. To harvest freshwater, various interfacial evaporators with rational designs of photothermal materials and structures have been developed concentrating on increasing the evaporation rate in the past few years. However, pathogenic microorganism accumulation on the evaporators by long-duration contact with natural water resources may lead to the deterioration of water transportation and the reduction of the evaporation rate. Here, we develop cationic photothermal hydrogels (CPHs) based on [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) and photothermal polypyrrole (PPy) with bacteria-inhibiting capability for freshwater production via solar-driven steam generation. A rapid water evaporation rate of 1.592 kg m-2 h-1 under simulated solar irradiation is achieved with CPHs floating on the water surface. Furthermore, we find that CPHs possess nearly 100% antibacterial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The significant bacteria-inhibiting capability is mainly attributed to the large number of ammonium groups on the CPH network. Moreover, we show that CPHs exhibit good applicability with stable evaporation in natural lake water over 2 weeks, and the number of bacteria in purified lake water is significantly reduced. The device based on CPHs can achieve ∼0.49 kg m-2 h-1 freshwater production from lake water under natural sunlight. This study provides an attractive strategy for the evaporator to inhibit biological contamination and a potential way for long-term stable freshwater production from natural water resources in practical application.

Moist-Induced Electricity Generation by Electrospun Cellulose Acetate Membranes with Optimized Porous Structures.

Harvesting energy from moist in the atmosphere has recently been demonstrated as an effective manner for a portable power supply to meet the ever-increasing demands of energy consumption. Porous materials are shown to have great potential in moist-induced electricity generation. Herein, we report moist-induced electricity generation by electrospun cellulose acetate (CA) membranes with optimized porous structures. We show that the pore size and porosity of CA membranes can be readily tuned via a facile compression and annealing process, and the effect of pore features on the output voltages can thus be investigated systematically. We find that, at a relatively high porosity, the electricity-generation performance can be further enhanced by constructing a smaller pore to form more nanochannels. Porous CA membranes, with an optimized porosity of 52.6% and a pore diameter less than 250 nm, are prepared to construct moist-induced electricity generators, which can be applied as breath sensors and can power up calculator operation. The current study provides insights for the construction of porous materials with different pore characteristics for moist-induced electricity generation, especially in the exploration of more efficient and low-cost porous materials for large-scale practical application of the portable power supply.

Fluorescent Metallosupramolecular Elastomers for Fast and Ultrasensitive Humidity Sensing.

Fluorescent supramolecular polymers that can respond to subtle external stimuli to generate luminescence signals are promising in a wide range of applications, including probes, anti-counterfeiting materials, and sensors. However, complicated preparative procedures, limited responsive speed, and relatively low sensitivity still limit their practical sensing applications. Herein, we report europium-containing metallosupramolecular (PU-Eu) elastomers for fast and ultrasensitive humidity sensing by employing hygroscopic polyurethane (PU), whose urethane groups can coordinate with europium ions (Eu3+), emitting a strong luminescent signal by ligand-to-metal energy transfer. The variant of the coordination bond strength triggered by external humidity imparts the PU-Eu elastomer with a fast (∼1.1 s) and ultrasensitive response to the humid condition, where the external humidity increases by ∼1% and the corresponding fluorescence intensity will drop by ∼421.98 a.u. By a dip-coating process, PU-Eu elastomers can be conveniently coated on a hydrophilic and porous cellulose acetate nanofiber membrane, and the resulting composite membrane can achieve real-time and reversible monitoring of environmental humidity and human respiration. Given the versatility of PU-Eu elastomers, this study provides a low-cost and facile route of obtaining fluorescent metallosupramolecular polymers for fast and ultrasensitive humidity sensing.