Monolayer Nanosheets with an Extremely High Drug Loading toward Controlled Delivery and Cancer Theranostics

2D nanomaterials have attracted considerable research interest in drug delivery systems, owing to their intriguing quantum size and surface effect. Herein, Gd³⁺‐doped monolayered‐double‐hydroxide (MLDH) nanosheets are prepared via a facile bottom‐up synthesis method, with a precisely controlled composition and uniform morphology. MLDH nanosheets as drug carrier are demonstrated in coloading of doxorubicin and indocyanine green (DOX&ICG), with an ultrahigh drug loading content (LC) of 797.36% and an encapsulation efficiency (EE) of 99.67%. This is, as far as it is known, the highest LC level at nearly 100% of EE among previously reported 2D drug delivery systems so far. Interestingly, the as‐prepared DOX&ICG/MLDH composite material shows both pH‐controlled and near‐infrared‐irradiation‐induced DOX release, which holds a promise in stimulated drug release. An in vivo dual‐mode imaging, including near‐infrared fluorescence and magnetic resonance imaging, enables a noninvasive visualization of distribution profiles at the tumor site. In addition, in vitro and in vivo therapeutic evaluations demonstrate an excellent trimode synergetic anticancer activity and superior biocompatibility of DOX&ICG/MLDH. Therefore, MLDH nanosheets provide new perspectives in the design of multifunctional nanomedicine, which shows promising applications in controlled drug delivery and cancer theranostics.     

Enhancement of Light Output Power from LEDs Based on Monolayer Colloidal Crystal

One of the major challenges for the application of GaN‐based light emitting diodes (LEDs) in solid‐state lighting lies in the low light output power (LOP). Embedding nanostructures in LEDs has attracted considerable interest because they may improve the LOP of GaN‐based LEDs efficiently. Recent advances in nanostructures derived from monolayer colloidal crystal (MCC) have made remarkable progress in enhancing the performance of GaN‐based LEDs. In this review, the current state of the art in this field is highlighted with an emphasis on the fabrication of ordered nanostructures using large‐area, high‐quality MCCs and their demonstrated applications in enhancement of LOP from GaN‐based LEDs. We describe the remarkable achievements that have improved the internal quantum efficiency, the light extraction efficiency, or both from LEDs by taking advantages of diverse functions that the nanostructures provided. Finally, a perspective on the future development of enhancement of LOP by using the nanostructures derived from MCC is presented.     

Interfacial Capillary‐Force‐Driven Self‐Assembly of Monolayer Colloidal Crystals for Supersensitive Plasmonic Sensors

Colloidal lithography technology based on monolayer colloidal crystals (MCCs) is considered as an outstanding candidate for fabricating large‐area patterned functional nanostructures and devices. Although many efforts have been devoted to achieve various novel applicatons, the quality of MCCs, a key factor for the controllability and reproducibility of the patterned nanostructures, is often overlooked. In this work, an interfacial capillary‐force‐driven self‐assembly strategy (ICFDS) is designed to realize a high‐quality and highly‐ordered hexagonal monolayer MCCs array by resorting the capillary effect of the interfacial water film at substrate surface as well as controlling the zeta potential of the polystyrene particles. Compared with the conventional self‐assembly method, this approach can realize the reself‐assembly process on the substrate surface with few colloidal aggregates, vacancy, and crystal boundary defects. Furthermore, various typical large‐scale nanostructure arrays are achieved by combining reactive ion etching, metal‐assisted chemical etching, and so forth. Specifically, benefiting from the as‐fabricated high‐quality 2D hexagonal colloidal crystals, the surface plasmon resonance (SPR) sensors achieve an excellent refractive index sensitivity value of 3497 nm RIU^?1, which is competent for detecting bovine serum albumin with an ultralow concentration of 10^?8 m . This work opens a window to prepare high‐quality MCCs for more potential applications.     

Two-dimensional Aluminum Oxide Nanosheets Decorated with Palladium Oxide Nanodots for Highly Stable and Selective Hydrogen Sensing

Hydrogen (H₂) sensing materials such as semiconductor metal oxides may suffer from poor long-term stability against humidity and unsatisfactory selectivity against other interfering gases. To address the above issues, highly stable and selective H₂ sensing built with palladium oxide nanodots decorating aluminum oxide nanosheets (PdO NDs//Al₂O₃ NSs) has been achieved via combined template synthesis, photochemical deposition, and oxidation. Typically, the PdO NDs//Al₂O₃ NSs are observed with thin NSs (≈17 nm thick) decorated with nanodots (≈3.3 nm in diameter). Beneficially, the sensor prototypes built with PdO NDs//Al₂O₃ NSs show excellent long-term stability for 278 days, high selectivity against interfering gases, and outstanding stability against humidity at 300 °C. Remarkably, the sensor prototypes enable detection of a wide-range of 20 ppm – 6 V/V% H₂, and the response and recovery times are ≈5 and 16 s to 1 V/V% H₂, respectively. Theoretically, the heterojunctions of PdO NDs-Al₂O₃ NSs with a large specific surface ratio and Al₂O₃ NSs as the support exhibit excellent stability and selective H₂ sensing. Practically, a sensing device integrated with the PdO NDs//Al₂O₃ NSs sensor prototype is simulated for detecting H₂ with reliable sensing response.     

Au‐Edged CuZnSe2 Heterostructured Nanosheets with Enhanced Electrochemical Performance

Two‐dimensional (2D) nanomaterials and heterostructured nanocrystals (NCs) are two hot topics in current nanoresearch. However, reports on heterostructured NCs with 2D features are still rare. In this work, we demonstrate a one‐pot colloidal chemistry route for synthesizing Au‐CuZnSe₂ heterostructures with spherical Au domains attached to the edge of a sheet of CuZnSe₂. This protocol involves the preferential formation of Au clusters and the seeded growth of CuZnSe₂ sheets because of the lattice matching of CuSe with Au. As an example to demonstrate the importance of such heterostructures, the electrochemical performance of Au‐CuZnSe₂ heterostructured nanosheets is compared with that of heterostructured nanorods, Au NCs, and CuZnSe₂ NCs. The heterostructured nanosheets exhibit the best electrochemical activity.     

Colloidally Stable Silicon Nanocrystals with Near‐Infrared Photoluminescence for Biological Fluorescence Imaging

Luminescent silicon nanocrystals (ncSi) are showing great promise as photoluminescent tags for biological fluorescence imaging, with size‐dependent emission that can be tuned into the near‐infrared biological window and reported lack of toxicity. Here, colloidally stable ncSi with NIR photoluminescence are synthesized from (HSiO_1.5)_n sol–gel glasses and are used in biological fluorescence imaging. Modifications to the thermal processing conditions of (HSiO_1.5)_n sol–gel glasses, the development of new ncSi oxide liberation chemistry, and an appropriate alkyl surface passivation scheme lead to the formation of colloidally stable ncSi with photoluminescence centered at 955 nm. Water solubility and biocompatibility are achieved through encapsulation of the hydrophobic alkyl‐capped ncSi within PEG‐terminated solid lipid nanoparticles. Their applicability to biological imaging is demonstrated with the in‐vitro fluorescence labelling of human breast tumor cells.     

Kirigami‐Inspired Nanoconfined Polymer Conducting Nanosheets with 2000% Stretchability

Stretchable conductors are essential components of wearable electronics. However, such materials typically sacrifice their electronic conductivity to achieve mechanical stretchability and elasticity. Here, the nanoconfinement and air/water interfacial assembly is explored to grow freestanding mechanical endurance conducting polymer nanosheets that can be stretched up to 2000% with simultaneously high electrical conductivity, inspired by kirigami. Such stretchable conductors show remarkable electronic and mechanical reversibility and reproducibility under more than 1000 cycle durability tests with 2000% deformability, which can be accurately predicted using finite element modeling. The conductivity of nanoconfined freestanding conductor nanosheets increases by three orders of magnitude from 2.2 × 10^?3 to 4.002 S cm^?1 is shown, due to the charge‐transfer complex formation between polymer chain and halogen, while the electrical conductance of the stretchable kirigami nanosheets can be maintained over the entire strain regime. The nanoconfined polymer nanosheets can also act as a sensor capable of sensing the pressure with high durability and real‐time monitoring.     

Superhigh and Robust Ion Selectivity in Membranes Assembled with Monolayer Clay Nanosheets

It is crucial to control the ion transport in membranes for various technological applications such as energy storage and conversion. The emerging functional two-dimensional (2D) nanosheets such as graphene oxide and MXenes show great potential for constructing ordered nanochannels, but the assembled membranes suffer from low ion selectivity and stability. Here a class of robust charge-selective membranes with superhigh cation/anion selectivity, which are assembled with monolayer nanosheets of cationic/anionic clays that inherently have permanent and uniform charges on each layer is reported. The transport number of cations/anions of cationic vermiculite nanosheet membranes (VNMs)/anionic Co-Al layered double hydroxide (CoAl-LDH) nanosheet membranes is over 0.90 in different NaCl concentration gradients, outperforming all the reported ion-selective membranes. Importantly, this excellent ion selectivity can persist at high-concentration salt solutions, under acidic and alkaline conditions, and for a wide range of ions of different sizes and charges. By coupling a pair of cation-selective vermiculite membrane and anion-selective CoAl-LDH membrane, a reverse electrodialysis device which shows an output power density of 0.7 W m⁻² and energy conversion efficiency of 45.5% is constructed. This work provides a new strategy to rationally design high-performance ion-selective membranes by using 2D nanosheets with inherent surface charges for controllable ion-transport applications.     

Epitaxial Growth of Honeycomb Monolayer CuSe with Dirac Nodal Line Fermions

2D transition metal chalcogenides have attracted tremendous attention due to their novel properties and potential applications. Although 2D transition metal dichalcogenides are easily fabricated due to their layer‐stacked bulk phase, 2D transition metal monochalcogenides are difficult to obtain. Recently, a single atomic layer transition metal monochalcogenide (CuSe) with an intrinsic pattern of nanoscale triangular holes is fabricated on Cu(111). The first‐principles calculations show that free‐standing monolayer CuSe with holes is not stable, while hole‐free CuSe is endowed with the Dirac nodal line fermion (DNLF), protected by mirror reflection symmetry. This very rare DNLF state is evidenced by topologically nontrivial edge states situated inside the spin–orbit coupling gaps. Motivated by the promising properties of hole‐free honeycomb CuSe, monolayer CuSe is fabricated on Cu(111) surfaces by molecular beam epitaxy and confirmed success with high resolution scanning tunneling microscopy. The good agreement of angle resolved photoemission spectra with the calculated band structures of CuSe/Cu(111) demonstrates that the sample is monolayer CuSe with a honeycomb lattice. These results suggest that the honeycomb monolayer transition metal monochalcogenide can be a new platform to study 2D DNLFs.     

山嵛酸Langmuir膜结合氨气扩散控制生长碱式硝酸锌薄膜

利用山嵛酸Langmuir膜有机模板控制和氨气扩散动力学控制相结合的仿生矿化方法,制备了大面积均匀致密且沿(200)晶面取向生长的Zn5(OH)8(NO3)2·2H2O薄膜。采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和X射线衍射(XRD)分别对样品形貌、表面成分及其晶型进行了表征。结合π-A曲线研究了薄膜生长的驱动力,对材料结构的形成原因进行了探讨。结果表明,Langmuir膜模板诱导结合动力学控制下的无机晶体生长体系为在室温下合成特殊结构和性能的薄膜材料提供了一种可行的方法。     

Ultrathin Iron‐Cobalt Oxide Nanosheets with Abundant Oxygen Vacancies for the Oxygen Evolution Reaction

Electrochemical water splitting is a promising method for storing light/electrical energy in the form of H₂ fuel; however, it is limited by the sluggish anodic oxygen evolution reaction (OER). To improve the accessibility of H₂ production, it is necessary to develop an efficient OER catalyst with large surface area, abundant active sites, and good stability, through a low‐cost fabrication route. Herein, a facile solution reduction method using NaBH₄ as a reductant is developed to prepare iron‐cobalt oxide nanosheets (Fe_x Co_y ‐ONSs) with a large specific surface area (up to 261.1 m² g^?1), ultrathin thickness (1.2 nm), and, importantly, abundant oxygen vacancies. The mass activity of Fe₁Co₁‐ONS measured at an overpotential of 350 mV reaches up to 54.9 A g^?1, while its Tafel slope is 36.8 mV dec^?1; both of which are superior to those of commercial RuO₂, crystalline Fe₁Co₁‐ONP, and most reported OER catalysts. The excellent OER catalytic activity of Fe₁Co₁‐ONS can be attributed to its specific structure, e.g., ultrathin nanosheets that could facilitate mass diffusion/transport of OH^? ions and provide more active sites for OER catalysis, and oxygen vacancies that could improve electronic conductivity and facilitate adsorption of H₂O onto nearby Co³⁺ sites.     

Stabilizing Atomically Dispersed Catalytic Sites on Tellurium Nanosheets with Strong Metal–Support Interaction Boosts Photocatalysis

The utilization of appropriate supports for constructing single‐atom‐catalysts is of vital importance to achieve high catalytic performances, as the strong mutual interactions between the atomically dispersed metal atoms and supports significantly influence their electronic properties. Herein, it is reported that atomic cobalt species (ACS) anchored 2D tellurium nanosheets (Te NS) can act as a highly active single‐atom cocatalyst for boosting photocatalytic H₂ production and CO₂ reduction reactions under visible light irradiation, wherein Te NS serves as the ideal support material to bridge the light absorbers and ACS catalytic sites for efficient electron transfer. X‐ray absorption near‐edge structure spectroscopy reveals that the ACS are built by a Co center coordinated with five Co? O bonding, which are anchored on Te NS through one Co? Te bonding. The strong mutual interaction between the Te NS and ACS alters the electronic structure of Te NS, inducing the introduction of intermediate energy states, which act as trap sites to accommodate the photogenerated electrons for promoting photocatalytic reactions. This work may inspire further capability in designing other Te‐based single‐atom‐catalysts for highly efficient solar energy conversion.