Solution-Processable MOF-on-MOF System Constructed via Template-Assisted Growth for Ultratrace H2S Detection.

Conductive metal-organic frameworks (c-MOFs) hold promise for highly sensitive sensing systems due to their conductivity and porosity. However, the fabrication of c-MOF thin films with controllable morphology, thickness, and preferential orientation remains a formidable yet ubiquitous challenge. Herein, we propose an innovative template-assisted strategy for constructing MOF-on-MOF (Ni3(HITP)2/NUS-8 (HITP: 2,3,6,7,10,11-hexamino-tri(p-phenylene))) systems with good electrical conductivity, porosity, and solution processability. Leveraging the 2D nature and solution processability of NUS-8, we achieve the controllable self-assembly of Ni3(HITP)2 on NUS-8 nanosheets, producing solution-processable Ni3(HITP)2/NUS-8 nanosheets with a film conductivity of 1.55 × 10-3 S·cm-1 at room temperature. Notably, the excellent solution processability facilitates the fabrication of large-area thin films and printing of intricate patterns with good uniformity, and the Ni3(HITP)2/NUS-8-based system can monitor finger bending. Gas sensors based on Ni3(HITP)2/NUS-8 exhibit high sensitivity (LOD ~ 6 ppb) and selectivity towards ultratrace H2S at room temperature, attributed to the coupling between Ni3(HITP)2 and NUS-8 and the redox reaction with H2S. This approach not only unlocks the potential of stacking different MOF layers in a sequence to generate functionalities that cannot be achieved by a single MOF, but also provides novel avenues for the scalable integration of MOFs in miniaturized devices with salient sensing performance.

Interpenetrated Multinetwork Hybrid Aerogels by Layered Montmorillonite and One-Dimensional Hydroxyapatite Fibers for Heat and Fire Insulation.

It is of practical significance to develop aerogels with effective thermal insulation characteristics together with fireproof properties as well as high mechanical strength. Here, an interpenetrated multinetwork hybrid aerogel realizing thermal insulation, flame retardancy, and high compression modulus is demonstrated. Specifically, one-dimensional hydroxyapatite nanowires (HAP) played dual roles as the aerogel support skeleton to entangle with layered montmorillonite (MMT) each other to form a three-dimensional interpenetrated multinetwork structure and to optimize the thermal conductivity by adjusting the pore space in current HAP/MMT/PVA hybrid aerogels. Therefore, the interpenetrated multinetwork hybrid aerogels exhibit superior thermal insulation performance in room temperature (0.033 W m-1 K-1, 298 K, air conditions) and largely enhanced ultrahigh compression modulus (80 MPa). Moreover, the obtained hybrid aerogels also exhibit excellent flame retardancy and self-extinguishing smoke suppression properties (peak heat release rate and total smoke production as low as 92.44 kW m-2 and 0.1 m2, respectively), which is the outstanding interpenetrated multinetwork hybrid aerogel that has achieved synergistic improvement in heat and fire insulation and mechanical performance. Therefore, the interpenetrated multinetwork hybrid aerogels are promising candidates for efficient heat insulation, fire prevention, and mechanically robust applications.

Amorphous FeSnOx Nanosheets with Hierarchical Vacancies for Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium-ion batteries (LIBs) in various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two-dimensional (2D) iron tin oxide (A-FeSnOx) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1 mg cm-2), ultra-thin (~200 nm), and ultra-robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3 mAh g-1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.

Tuning the morphology of Cu-MOFs nanostructures for sensitive ascorbic acid sensing.

Metal organic frameworks are an attractive platform to develop fascinating electrocatalysts for the oxidation of ascorbic acid (AA), and their different morphologies have been hinted in literature to impact their sensing performance. In this work, by varying the reaction medium of metal source and organic ligand, copper 2-hydroxybenzene-1,4-dicarboxylate (CuBDC-OH) nanosheets (NSs), nanorods (NRs) and bulk were generated. Thereinto, CuBDC-OH-NSs displayed the highest sensitivity of 151.99µA mM-1cm-2in the linear range of 12-1074µM, which is 1.5 times greater than that of CuBDC-OH NRs and 3.5 times greater than that of CuBDC-OH bulk. The electrochemical analyzes manifested that the superiority of nanosheets originated from higher oxidative current, larger electrochemical active surface area and lower charge transfer resistance, which enabling the efficient electro-oxidation of AA. Additionally, satisfactory selectivity, stability and reproducibility were obtained.

In-situ growth of SnO2 nanoparticles on Nb2CTx nanosheets as highly sensitive electrochemical sensing platform for organophosphorus pesticide detection.

In this study, the SnO2/Nb2CTx MXene nanocomposite containing 0D/2D interfaces was prepared by situ growth strategy of one-step hydrothermal method. A SnO2/Nb2CTx MXene based acetylcholinesterase (AChE) biosensor was constructed for pesticide detection. Highly conductive Nb2CTx MXene, acting as substrate material, restrained the agglomeration of nanoparticles (NPs) and accelerated electron migration due to the confinement effect and well-known accordion-like layered structure. In addition, SnO2 anchored on both sides of the Nb2CTx MXene nanosheets effectively provided a large surface area, abundant surface groups and active sites, which preserved numbers of electrons at the interface of the heterojunction. The SnO2/Nb2CTx MXene hybrids with outstanding conductivity, good biocompatibility and structural stability were beneficial for AChE immobilization. Under the optimized conditions, as-fabricated electrochemical biosensor demonstrated superior performance with linear detection range of 5.1 × 10-14 - 5.1 × 10-7 M for chlorpyrifos, along with the limit of detection (LOD) down to 5.1 × 10-14 M (calculated for 10% inhibition). Furthermore, it is highly expected that this biosensor can be applied for the detection of other organophosphorus pesticides in the environment, providing an effective nanoplatform in biosensing field.

Two-dimensional manganese-iron bimetallic MOF-74 for electro-Fenton degradation of sulfamethoxazole.

This study reported a novel application of Mn0.67Fe0.33-MOF-74 with two-dimensional (2D) morphology grown on carbon felt as a cathode for efficiently removing antibiotic sulfamethoxazole in the heterogeneous electro-Fenton system. Characterization demonstrated the successful synthesis of bimetallic MOF-74 by a simple one-step method. Electrochemical detection showed that the second metal addition and morphological change improved the electrochemical activity of the electrode and contributed to pollutant degradation. At pH 3 and 30 mA of current, the degradation efficiency of SMX reached 96% with 12.09 mg L-1 H2O2 and 0.21 mM ·OH detected in the system after 90 min. During the reaction, electron transfer between ≡FeII/III and ≡MnII/III promoted divalent metal ions regeneration, which ensured the continuation of the Fenton reaction. Two-dimensional structures exposed more active sites favoring ·OH production. The pathway of sulfamethoxazole degradation and the reaction mechanisms were proposed based on the intermediates identification by LC-MS and radical capture results. High degradation rates were still observed in tap and river water, revealing the potential of Mn0.67Fe0.33-MOF-74@CF for practical applications. This study provides a simple MOF-based cathode synthesis method, which enhances our understanding of constructing efficient electrocatalytic cathodes based on morphological design and multi-metal strategies.

Automated One-Drop Assembly for Facile 2D Film Deposition.

The effective application of 2D materials is strongly dependent on the mass production of high-quality large-area 2D thin films. Here, we demonstrate a strategy for the automated manufacturing of high-quality 2D thin films using a modified drop-casting approach. Our approach is simple; by using an automated pipette, a dilute aqueous suspension is dropped onto a substrate heated on a hotplate, and controlled convection by Marangoni flow and liquid removal causes the nanosheets to come together to form a tile-like monolayer film in 1-2 min. Ti0.87O2 nanosheets are utilized as a model system for investigating the control parameters such as concentrations, suction speeds, and substrate temperatures. We perform the automated one-drop assembly of a range of 2D nanosheets (metal oxides, graphene oxide, and hexagonal boron nitride) and successfully fabricate various functional thin films in multilayered, heterostructured, and sub-micrometer-thick forms. Our deposition method enables on-demand large-size (>2 inchϕ) manufacturing of high-quality 2D thin films while reducing the time and sample consumption.

Vanadium Oxide Nanosheet-Infused Functionalized Polysulfone Bipolar Membrane for an Efficient Water Dissociation Reaction.

A high-performing bipolar membrane (BPM) was fabricated using functionalized polysulfones as the ion-exchange layers (IELs) and two-dimensional (2D) V2O5-nanosheets blended with polyvinyl alcohol (PVA) as the water dissociation catalyst (WDC) at the interfacial layer. The composite BPM showed a low resistance of 0.79 Ω cm2, confirming the good contact between the IEL and WDC, much needed for the ionic conductivity. It also demonstrated high water dissociation performance with a water dissociation voltage of 1.11 V corresponding to a current density of 1.02 mA/cm2 in the presence of a 1 M NaCl electrolytic solution. The functionalization of the polysulfone with -SO3- and R4N+ groups successfully resulted in the increase of hydrophilicity of the polymer, thereby increasing the water uptake capacity of the membranes. The blending of 2D V2O5 nanosheets with PVA proved to be an effective WDC, as confirmed by the increased conductivity and efficiency of the water dissociation (WD) reaction. The 2D V2O5-ns have great potential toward water adsorption onto its surface, thereby interacting with the water molecules, weakening the bonding force of water, and dissociating it into H+ and OH-. The transportation of coions across the membranes and generation of protons and hydroxyl ions at the interfacial layer are correlated with the change in the pH of the catholyte and anolyte as a function of current density during the WD reaction. The high performance of the composite BPM (BPM_VO-ns) was demonstrated at a higher current density of 100 mA/cm2 with a WD resistance of 0.027 Ω cm2. The durability was tested by subjecting it to 45 h of run at lower (1.02 mA/cm2) and higher (100 mA/cm2) current densities which display a negligible change in the interlayer voltage. Thus, the fabricated composite BPMs pave the way to be utilized for efficient and durable WD reactions under neutral electrolytic conditions.

Ultrathin Hafnium Disulfide Atomic Crystals with ROS-Scavenging and Colon-Targeting Capabilities for Inflammatory Bowel Disease Treatment.

The exciting success of NBTXR3 in the clinic has triggered a tumult of activities in the design and development of hafnium-based nanoparticles. However, due to the concerns of nondegradation and limited functions, the biomedical applications of Hf-based nanoparticles mainly focus on tumors. Herein, tannic acid capped hafnium disulfide (HfS2@TA) nanosheets, a 2D atomic crystal of hafnium-based materials prepared by liquid-phase exfoliation, were explored as high-performance anti-inflammatory nanoagents for the targeted therapy of inflammatory bowel disease (IBD). Benefiting from the transformation of the S2-/S6+ valence state and huge specific surface area, the obtained HfS2@TA nanosheets were not only capable of effectively eliminating reactive oxygen species/reactive nitrogen species and downregulating pro-inflammatory factors but also could be excreted via kidney and hepatointestinal systems. Unexpectedly, HfS2@TA maintained excellent targeting capability to an inflamed colon even in the harsh digestive tract environment, mainly attributed to the electrostatic interactions between negatively charged tannic acid and positively charged inflamed epithelium. Encouragingly, upon oral or intravenous administration, HfS2@TA quickly inhibited inflammation and repaired the intestinal mucosa barrier in both dextran sodium sulfate and 2,4,6-trinitrobenzenesulfonic acid induced IBD models. This work demonstrated that ultrathin HfS2@TA atomic crystals with enhanced colon accumulation were promising for the targeted therapy of IBD.

Enhancing Tumor Catalytic Therapy by Co-Catalysis.

Fenton reactions have been recently applied in tumor catalytic therapy, whose efficacy suffers from the unsatisfactory reaction kinetics of Fe3+ to Fe2+ conversion. Here we introduce a co-catalytic concept in tumor catalytic therapy by using a two-dimensional molybdenum disulfide (MoS2 ) nanosheet atomically dispersed with Fe species. The single-atom Fe species act as active sites for triggering Fenton reactions, while the abundant sulfur vacancies generated on the nanosheet favor electron capture by hydrogen peroxide for promoting hydroxyl radical production. Moreover, the 2D MoS2 support also acts as a co-catalyst to accelerate the conversion of Fe3+ to Fe2+ by the oxidation of active Mo4+ sites to Mo6+ , thereby promoting the whole catalytic process. The 2D nanocatalyst exhibits a desirable catalytic performance, as well as a significantly enhanced anticancer efficacy both in vitro and in vivo, which indicates the feasibility for applying such a co-catalytic concept in tumor therapy.

Yb3+-Doped Two-Dimensional Upconverting Tb-MOF Nanosheets with Luminescence Sensing Properties.

In this article, we synthesized a Yb3+-doped two-dimensional (2-D) upconverting Tb metal-organic framework (Tb-MOF) (hereinafter referred to as Tb-UCMOF) by a one-step solvothermal method. The synthesized Tb-UCMOF is composed of stacks of 2-D nanosheets with an average width distributed between 250 and 300 nm, and these nanosheets can be exfoliated by a simple liquid ultrasound method. The structural characteristics of this flaky particle accumulation are confirmed by the type IV adsorption-desorption isotherm with a H3-type adsorption hysteresis loop, and the Brunauer-Emmett-Teller surface of Tb-UCMOF is 143.9257 m2·g-1. Tb-UCMOF has characteristic emissions of Tb3+ which are located at 490, 545, 585, and 621 nm under 980 nm excitation. The upconverting luminescence mechanism is attributed to that Yb3+ absorbs multiple photons and transfers the energy to Tb3+, causing its 4f electrons to jump to the excited state, and then the upconverting emissions are obtained when electrons return to the ground state. Since the Tb-UCMOF nanosheets have high dispersibility and an obvious upconverting luminescent signal, we explored their luminescence sensing properties. The luminescence intensity is found to gradually decrease with the addition of Cu2+, the linear range of Cu2+ sensing is 0-1.4 µM, and the detection limit is 0.16 µM. This rapid, highly selective, and sensitive Cu2+ sensing indicates that 2-D upconverting MOF nanosheets have great application prospects in luminescence sensing and also promote the research of 2-D upconverting MOFs with specific recognition for the application of biological and environmental luminescent sensors.

Copper-doping defect-lowered perovskite nanosheets for deep-blue light-emitting diodes.

Mixed-halide blue perovskites CsPb(Br/Cl)3 are considered promising candidates for developing efficient deep-blue perovskite light-emitting diodes (PeLEDs), but their low photoluminescence quantum yield (PLQY), environmental instability, and poor device performance gravely inhibit their future development. Here, we employ a heteroatomic Cu2+ doping strategy combined with post-treatment Br- anion exchange to prepare high-performance deep-blue perovskites CsPb(Br/Cl)3. The Cu2+ doping strategy significantly decreases the intrinsic chlorine defects, ensuring that the inferior CsPbCl3 quantum dots are transformed into two-dimensional nanosheets with enhanced violet photoluminescence and increased exciton binding energy. Further, with the post-treatment Br- anion exchange, the as-prepared CsPb(Br/Cl)3 nanosheets with more radiation recombination and less ion migration present an enhanced PLQY of 94% and better humidity stability of 30 days. Based on the optimized CsPb(Br/Cl)3, we fabricated deep-blue PeLEDs with luminescence emission at 462 nm, a maximum luminance of 761 cd m-2, and a current density of 205 mA cm-2. This work puts forward a feasible synthesis strategy to prepare efficient and stable mixed-halide blue perovskite CsPb(Br/Cl)3 and related blue PeLEDs, which may promote the further application of mixed-halide perovskites in the blue light range.

Frustrated Layered Self-Assembly Induced Superlattice from Two-Dimensional Nanosheets.

Here we reported a hierarchical self-assembly approach toward well-defined superlattices in supramolecular liquid crystals by fullerene-based sphere-cone block molecules. The fullerenes crystallize to form monolayer nanosheets intercalated by the attached soft hydrocarbon cones. The frustration caused by cross-sectional area mismatch between the spheres and the somewhat oversize cones leads to a unique lamellar superlattice whereby each stack of six pairs of alternating sphere-cone sublayers is followed by a cone double layer. While such areal mismatch problems in soft matter are usually solved by interface curvature, the lamellar superlattice solution is best suited to systems with rigid layers. Meanwhile, formation of the superlattice significantly improves the material's transient electron conductivity, with the maximum value being among the highest for π-conjugated organic materials. The design principle of solving steric frustration by forming a superlattice opens a new avenue toward self-assembled optoelectronic materials.

One-step controllable synthesis of amino-modification siloxene for enhanced solar water-splitting.

Novel two-dimensional silicon-based material siloxene has been synthesized handily by a one-step method, which utilizes the characteristics of the topological exfoliation to simplify the process of synthesis and modification. It is worth mentioning that for the first time amino-modified derivative has been investigated. Amino modification can promote the oxidation of siloxene, enlarge the bandgap and extend the carrier lifetime of siloxene. The application of siloxene before and after modification in water-splitting has been investigated. In addition, the superiority of the resultant two-dimensional materials was concisely elaborated, which revealed that owing to more effective photogenerated carriers' separation in amino modification siloxene, hydrogen production could be greatly promoted.

Two-Dimensional Transition Metal Oxide and Hydroxide-Based Hierarchical Architectures for Advanced Supercapacitor Materials.

The supercapacitor has been widely seen as one of the most promising emerging energy storage devices, by which electricity is converted from chemical energy and stored. Two-dimensional (2D) metal oxides/hydroxides (TMOs/TMHs) are revolutionizing the design of high-performance supercapacitors because of their high theoretical specific capacitance, abundance of electrochemically active sites, and feasibility for assembly in hierarchical structures by integrating with graphitic carbon, conductive polymers, and so on. The hierarchical structures achieved can not only overcome the limitations of using a single material but also bring new breakthroughs in performance. In this article, the research progress on 2D TMOs/TMHs and their use in hierarchical structures as supercapacitor materials are reviewed, including the evolution of supercapacitor materials, the configurations of hierarchical structures, the electrical properties regulated, and the existence of advantages and drawbacks. Finally, a perspective covering directions and challenges related to the development of supercapacitor materials is provided.

Ultrathin cobalt pyrophosphate nanosheets with different thicknesses for Zn-air batteries.

Two dimensional (2D) ultrathin nonprecious metal based catalysts show excellent electrocatalytic activities, due to the larger surface areas, more catalytic sites and more interconnected electron-transfer access than their bulk counterparts. Here, we synthesized cobalt pyrophosphate (Co2P2O7) nanosheets with different thickness by a simple and efficient one-step hydrothermal process. The catalytic performance of the obtained Co2P2O7 was investigated via diverse electrochemical measurement. Due to the unique 2D structure and the flexible coordination of pyrophosphate group, the as-prepared Co2P2O7 catalyst had excellent electrocatalytic performance and good stability, which could rank among the most active nonprecious metal catalysts for oxygen evolution reaction and oxygen reduction reaction. In addition, the ultrathin Co2P2O7 nanosheets exhibited good performance as the air cathode catalyst for zinc air batteries.

Two-dimensional nanosheets with high curcumin loading content for multimodal imaging-guided combined chemo-photothermal therapy.

Nowadays, two-dimensional (2D) nanomaterials with many fascinating physicochemical properties have drawn extensive attention as drug delivery platforms for cancer theranostics. Nevertheless, current existing 2D nanomaterial-based drug delivery systems normally undergo the bottlenecks of hash preparation process, low drug loading content and unsatisfactory therapeutic outcome. Herein, we developed a novel nanoparticles-induced assemble strategy to construct 2D nanosheets with ultra-high curcumin loading content of 59.6 % and excellent stability in water. Furthermore, a distinct photothermal effect and multimodal imaging property after polydopamine coating could be obtained, thereby leading to precise and efficient ablation of tumor in combination of curcumin-induced chemotherapy. More importantly, the design principle of our work offers novel facile strategy to assemble metal-binding drugs into 2D nanomedicine with high drug content and well-defined shapes.

Carbon-Coated MoSe2/MXene Hybrid Nanosheets for Superior Potassium Storage.

Potassium-ion batteries (PIBs) are attracting intensive interest for large-scale applications due to the high natural abundance of potassium sources. However, the large radius of K+ makes it difficult for electrode materials to accommodate the repeated K+ insertion and extraction. Thus, developing high-performance electrode materials for PIBs remains a great challenge. Herein, we present the rational design and fabrication of hierarchical carbon-coated MoSe2/MXene hybrid nanosheets (MoSe2/MXene@C) as a superior anode material for PIBs. Specifically, the highly conductive MXene substrate can effectively relieve the aggregation of MoSe2 nanosheets and improve the electronic conductivity. Moreover, the carbon layer enables us to reinforce the composite structure and further enhance the overall conductivity of the hybrid nanosheets. Meanwhile, strong chemical interactions are found at the interface of MoSe2 nanosheets and MXene flakes, contributing to promoting the charge-transfer kinetics and improving the structural durability. Consequently, as an anode material for PIBs, the resulting MoSe2/MXene@C achieves a high reversible capacity of 355 mA h g-1 at 200 mA g-1 after 100 cycles and an outstanding rate performance with 183 mA h g-1 at 10.0 A g-1. The presented design strategy holds great promise for developing more-efficient electrode materials for PIBs.

Scalable Production of Few-Layer Niobium Disulfide Nanosheets via Electrochemical Exfoliation for Energy-Efficient Hydrogen Evolution Reaction.

Two-dimensional (2D) niobium disulfide (NbS2) materials feature unique physical and chemical properties leading to highly promising energy conversion applications. Herein, we developed a robust synthesis technique consisting of electrochemical exfoliation under alternating currents and subsequent liquid-phase exfoliation to prepare highly uniform few-layer NbS2 nanosheets. The obtained few-layer NbS2 material has a 2D nanosheet structure with an ultrathin thickness of ∼3 nm and a lateral size of ∼2 µm. Benefiting from their unique 2D structure and highly exposed active sites, the few-layer NbS2 nanosheets drop-casted on carbon paper exhibited excellent catalytic activity for the hydrogen evolution reaction (HER) in acid with an overpotential of 90 mV at a current density of 10 mA cm-2 and a low Tafel slope of 83 mV dec-1, which are superior to those reported for other NbS2-based HER electrocatalysts. Furthermore, few-layer NbS2 nanosheets are effective as bifunctional electrocatalysts for hydrogen production by overall water splitting, where the urea and hydrazine oxidation reactions replace the oxygen evolution reaction.

Wet/Sono-Chemical Synthesis of Enzymatic Two-Dimensional MnO2 Nanosheets for Synergistic Catalysis-Enhanced Phototheranostics.

2D nanomaterials have attracted broad interest in the field of biomedicine owing to their large surface area, high drug-loading capacity, and excellent photothermal conversion. However, few studies report their "enzyme-like" catalytic performance because it is difficult to prepare enzymatic nanosheets with small size and ultrathin thickness by current synthetic protocols. Herein, a novel one-step wet-chemical method is first proposed for protein-directed synthesis of 2D MnO2 nanosheets (M-NSs), in which the size and thickness can be easily adjusted by the protein dosage. Then, a unique sono-chemical approach is introduced for surface functionalization of the M-NSs with high dispersity/stability as well as metal-cation-chelating capacity, which can not only chelate 64 Cu radionuclides for positron emission tomography (PET) imaging, but also capture the potentially released Mn2+ for enhanced biosafety. Interestingly, the resulting M-NS exhibits excellent enzyme-like activity to catalyze the oxidation of glucose, which represents an alternative paradigm of acute glucose oxidase for starving cancer cells and sensitizing them to thermal ablation. Featured with outstanding phototheranostic performance, the well-designed M-NS can achieve effective photoacoustic-imaging-guided synergistic starvation-enhanced photothermal therapy. This study is expected to establish a new enzymatic phototheranostic paradigm based on small-sized and ultrathin M-NSs, which will broaden the application of 2D nanomaterials.