2D materials are of particular interest in light‐to‐heat conversion, yet challenges remain in developing a facile method to suppress their light reflection. Herein, inspired by the black scales of ...Bitis rhinoceros, a generalized approach via sequential thermal actuations to construct biomimetic 2D‐material nanocoatings, including Ti3C2Tx MXene, reduced graphene oxide (rGO), and molybdenum disulfide (MoS2) is designed. The hierarchical MXene nanocoatings result in broadband light absorption (up to 93.2%), theoretically validated by optical modeling and simulations, and realize improved light‐to‐heat performance (equilibrium temperature of 65.4 °C under one‐sun illumination). With efficient light‐to‐heat conversion, the bioinspired MXene nanocoatings are next incorporated into solar steam‐generation devices and stretchable solar/electric dual‐heaters. The MXene steam‐generation devices require much lower solar‐thermal material loading (0.32 mg cm−2) and still guarantee high steam‐generation performance (1.33 kg m−2 h−1) compared with other state‐of‐the‐art devices. Additionally, the mechanically deformed MXene structures enable the fabrication of stretchable and wearable heaters dual‐powered by sunlight and electricity, which are reversibly stretched and heated above 100 °C. This simple fabrication process with effective utilization of active materials promises its practical application value for multiple solar–thermal technologies.
Inspired by the black scales of Bitis rhinoceros, a generalized approach is developed via sequential thermal actuations to construct biomimetic 2D‐material nanocoatings, including Ti3C2Tx MXene, reduced graphene oxide, and MoS2. The hierarchical MXene nanocoatings result in broadband light absorption, and realize improved light‐to‐heat performance, demonstrating extremely practical application value in solar steam generation and wearable thermal management.
Microsupercapacitors (MSCs) with neutral multivalent electrolytes are safer, cheaper, and exhibit higher theoretical energy densities compared with the MSCs with acidic and alkaline electrolytes. ...Multivalent charge carriers (e.g., Mg2+, Zn2+) in the MSCs with Ti3C2Tx MXene electrodes have not been demonstrated, which could theoretically achieve higher specific capacitances and energy densities. However, because of the larger size of multivalent charge carriers, the MXene electrodes require further modifications to facilitate reversible electrochemical reactions. Herein, through spontaneous intercalation of various metal ions into MXene multilayers, twelve metal ion intercalated MXene electrodes (Mn+‐MXene) are fabricated and demonstrate improved electrochemical performance. Different nanopillar effects are observed between divalent Be2+ and trivalent Al3+ intercalants, which are systematically investigated by electrochemical impedance spectroscopy and molecular dynamics simulation. Among all Mn+‐MXene electrodes, the Be2+‐MXene electrode largely facilitates the charge‐transfer process with minimal disturbance of electrolyte diffusion rates, showing improved specific capacitances and high rate performance in univalent (Li2SO4, Na2SO4, K2SO4) and multivalent electrolytes (BeSO4, MgSO4, ZnSO4). Finally, flexible Be2+‐MXene MSCs with neural ZnSO4 gel electrolytes are fabricated, demonstrating superior areal capacitances (77.2 mF cm−2) and high energy density (3.86 μWh cm−2 at 0.12 mW cm−2) together with high user safety.
A facile metal‐ion intercalation technology is developed to enhance the electrochemical performance of Ti3C2Tx MXene in various neutral multivalent electrolytes. Twelve metal ions are intercalated into MXene electrodes. The Be2+‐intercalated MXene electrode facilitates the charge‐transfer process with minimal disturbance of electrolyte diffusion rates. Finally, Be2+‐MXene microsupercapacitors with neural ZnSO4 gel electrolytes demonstrate superior areal capacitances together with high user safety.
Bacterial resistance toward antibiotics has been a worldwide threat; one way to fight against the resistance is to develop a multimechanism antibacterial agent to achieve synergistic performance. ...Graphene oxide (GO) is an emerging antibacterial agent combining multiple mechanisms (physical insertion and chemical disruption), and its rich functional groups enable the complexation/conjugation of nanomaterials to further improve antibacterial performance. Herein, a synergistic antimicrobial agent is established through the assembly of paramagnetic holmium ions and gold nanoclusters (AuNCs) onto GO nanosheets. The assembled nanosheets can be vertically aligned under weak and practical magnetic fields (<0.5 T ), providing high‐density sharp edges with preferential orientation to effectively pierce the bacterial membrane. Also, the conjugated AuNCs are efficiently delivered into bacteria to induce high oxidative stress, which strongly disturbs bacterial metabolism, leading to the death of both Gram‐positive and Gram‐negative bacteria. The antibacterial agent uses both physical (via oriented GO) and chemical (via GO and AuNCs) mechanisms to achieve synergistic antimicrobial performance with low IC50 values of 9.8 µg mL−1 on the basis of GO and 0.39 × 10−6 m on the basis of AuNCs. This multicomponent agent with dual antimicrobial mechanisms is expected to be a promising multifunctional‐antimicrobial agent with high biosafety.
A synergistic antimicrobial agent is established through the complexation of paramagnetic ions (holmium ions, Ho3+) and the conjugation of gold nanoclusters (AuNCs) onto graphene oxide (GO) nanosheets. The synergistic antimicrobial ability is achieved by disrupting the bacterial metabolism physically (via GO alignment under magnetic field inserting bacteria) and chemically (via GO and AuNCs producing reactive oxygen species) simultaneously.
Human skin serves as a multifunctional organ with remarkable properties, such as sensation, protection, regulation, and mechanical stretchability. The mimicry of skin's multifunctionalities via ...various nanomaterials has become an emerging topic. 2D materials have attracted much interest in the field of skin mimicry due to unique physiochemical properties. Herein, recent developments of using various 2D materials to mimic skin's sensing, protecting, and regulating capabilities are summarized. Next, to endow high stretchability to 2D materials, the approaches for fabrication of stretchable bilayer structures by integrating higher dimensional 2D materials onto soft elastomeric substrates are introduced. Accordion‐like 2D material structures can elongate with elastomers and undergo programmed folding/unfolding processes to mimic skin's stretchability. That stretchable 2D material devices can achieve effective tactile sensing and protecting capabilities under large deformation is then highlighted. Finally, multiple key directions and existing challenges for future development are discussed.
Progress in the use of various 2D materials to mimic skin's sensing, protecting, and regulating capabilities has been demonstrated in recent studies. Two important strategies to fabricate stretchable 2D material architectures are highlighted, including deposition on prestretched elastomer and back‐infiltration of elastomeric liquid. The accordion‐like 2D material structures can elongate with elastomers and undergo programmed folding/unfolding processes to mimic skin's stretchability.
A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4–4.3 eV is synthesized by a modified Hummers' procedure. The as‐synthesized GO photocatalyst has an interlayer spacing ...of 0.42 nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20 vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination.
Graphite oxide with an appropriate oxidization level serves as a photocatalyst for stable H2 generation from water in an aqueous solution or pure water. The energy level of the conduction band edge of the graphite oxide is high enough to effectively donate electrons for H2 generation from water in the presence of methanol.
Zr‐based porphyrin metal–organic framework (MOF‐525) nanocrystals with a crystal size of about 140 nm are synthesized and incorporated into perovskite solar cells. The morphology and crystallinity of ...the perovskite thin film are enhanced since the micropores of MOF‐525 allow the crystallization of perovskite to occur inside; this observation results in a higher cell efficiency of the obtained MOF/perovskite solar cell.
Flame‐retardant coatings are widely used in a variety of personnel or product protection, and many applications would benefit from film stretchability if suitable materials are available. It is ...challenging to develop flame‐retardant coatings that are stretchable, eco‐friendly, and capable of being integrated on mechanically dynamic devices. Here, a concept is reported that uses pretextured montmorillonite (MMT) hybrid nanocoatings that can undergo programed unfolding to mimic the stretchability of elastomeric materials. These textured MMT coatings can be transferred onto an elastomeric substrate to achieve an MMT/elastomer bilayer device with high stretchability (225% areal strain) and effective flame retardancy. The bilayer composite is utilized as flame‐retardant skin for a soft robotic gripper, and it is demonstrated that the actuated response can manipulate and rescue irregularly shaped objects from a fire scene. Furthermore, by depositing the conformal MMT nanocoatings on nitrile gloves, the firefree gloves can endure direct flame contact without ignition.
Montmorillonite–elastomer bilayer architectures with high stretchability and effective flame retardancy can be applied as flame‐retardant protective skins for soft robotic grippers and nitrile gloves. With the stretchable and flame‐retardant barriers, the soft pneumatic actuator is capable of continuous inflation/deflation within flames and can act as a compliant gripper for manipulating and rescuing irregular objects from a fire scene.
Uniform zirconium-based porphyrin metal–organic framework (MOF-525) thin films are grown on conducting glass substrates by using a solvothermal approach. The obtained MOF-525 thin film is ...electrochemically addressable in aqueous solution and shows electrocatalytic activity for nitrite oxidation. The mechanism for the electrocatalytic oxidation of nitrite at the MOF-525 thin film is investigated by cyclic voltammetry. The redox mechanism of the MOF-525 thin film in the KCl aqueous solution is studied by amperometry. The MOF-525 thin film is deployed as an amperometric nitrite sensor. The linear range, sensitivity, and limit of detection are 20–800μM, 95μA/mM-cm2, and 2.1μM, respectively.
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•Zirconium-based porphyrin MOF thin films are grown on conducting substrates.•The MOF-525 thin film shows electrocatalytic activity for nitrite oxidation.•Redox and electrocatalytic mechanisms of the MOF thin film are investigated.•The amperometric nitrite sensor using MOF-525 thin film is successfully developed.
Mismatched deformation in a bilayer composite with rigid coating on a soft substrate results in complex and uniform topographic patterns, yet it remains challenging to heterogeneously pattern the ...upper coatings with various localized structures. Herein, a heterogeneous, 3D microstructure composed of Ti3C2T x titanium carbide (MXene) and single-walled carbon nanotubes (SWNTs) was fabricated using a one-step deformation of a thermally responsive substrate with designed open holes. The mechanically deformed SWNT–MXene (s-MXene) structure was next transferred onto an elastomeric substrate, and the resulting s-MXene/elastomer bilayer device exhibited three localized surface patterns, including isotropic crumples, periodic wrinkles, and large papillae-like microstructures. By adjusting the number and pattern, the s-MXene papillae arrays exhibited superhydrophobicity (>170°), strong and tunable adhesive force (52.3–110.6 μN), and ultra-large liquid capacity (up to 35 μL) for programmable microdroplet manipulation. The electrically conductive nature of s-MXene further enabled proper thermal management on microdroplets via Joule heating for miniaturized antibacterial tests. The s-MXene papillae were further fabricated in a piezoresistive pressure sensor with high sensitivity (11.47 kPa–1). The output current changes of s-MXene sensors were highly sensitive to voice vibrations and responded identically with prerecorded profiles, promising their application in accurate voice acquisition and recognition.
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