Monolayer MoS₂ has garnered significant interest because of its exceptional optoelectronic and tribological properties and potential application as a lubrication layer in micro- and nanoelectromechanical systems. Although the nanotribological performance of chemical vapor deposition (CVD)-grown MoS₂ and the characteristics associated with CVD growth have been extensively studied, challenges remain in designing specific regions on the monolayer MoS₂ surface with reduced friction. Here, we develop nuclei with an onion-shell structure on CVD-grown monolayer MoS₂ to achieve remarkable friction and adhesion reduction. These nuclei, dispersed on high-quality and crystalline MoS₂, consist of an oxi-sulfide core surrounded by a multilayer MoS₂ shell. Lateral force microscopy results indicate that onion-shell nuclei create an ensemble effect that decreases friction and adhesion by up to 45% and 20%, respectively, compared with those of MoS₂ because of the multilayer structure and in-plane tensile strain, both of which minimize out-of-plane deformation. Derjaguin–Müller–Toporov (DMT) model calculations and step-down load‒friction correlations illustrate that the work of adhesion, shear strength, and coefficient of friction on the nucleus decrease by more than 22%, 19%, and 34%, respectively, compared with those on MoS₂. The onion-shell nucleus presents a novel lubrication strategy to mitigate friction and adhesion in CVD-grown two-dimensional (2D) materials, with potential applications in lubricating nanoscale friction pairs.

Heterointerfaces formed by the intimate connection of different materials with electromagnetic losses are expected to achieve stronger electromagnetic (EM) absorption. However, constructing composites with heterointerfaces still faces great challenges in facile preparation process, optimized impedance matching, high reflection loss (R_L), and ultrathin matching thickness. In this work, we develop ZIF-8 functionalized MXene to produce hierarchical Ti₃C₂@C@ZnO composites with heterointerface to advance EM absorption enhancement. Modified with polydopamine (PDA), few-layer Ti₃C₂T_x MXene sheets enable adsorption of Zn²⁺ metal ions on Ti₃C₂T_x@PDA by electrostatic interaction for in-situ growth of ZIF-8. Ti₃C₂/C/ZnO heterointerface were obtained after heat treatment of Ti₃C₂T_x@PDA@ZIF-8 nanocomposites at various temperatures. The Ti₃C₂/C/ZnO-600 °C with 1.15 mm thickness have a R_L of −50.241 dB and an effective absorption bandwidth of 3.50 GHz. In-depth studies on the electromagnetic loss mechanisms reveal that Ti₃C₂, carbon, and ZnO in nanocomposites generate multiple interfacial polarization losses beyond partial conductivity losses caused by Ti₃C₂ and ZnO. Oxygen vacancy defects in ZnO form dipole losses with carbon. This work not only provides a simple and effective concept for preparing MXene@MOFs heterogeneous composites as an ultrathin and strong electromagnetic wave absorber, but also offers a vital guideline to fabricate various metal oxides derived from the MXene and metal-organic frameworks (MOFs) precursors.

With the increasing emphasis on ecological safety and physical health, the detection and treatment of harmful substances and diseases are becoming more and more prevalent. Therefore, efficiently monitoring these biological behaviors with high accuracy and sensitivity in real-time has shown prominent research significance. The use of fluorescent probes to analyze organisms has gained momentum in recent years, especially in the field of organ imaging and assisted cancer therapy, where fluorescent bioanalysis demonstrates significant advantageous. In this review, we explored the latest advancements in fluorescent molecular probes (e.g., small-molecule, macro-molecule, supramolecule) and fluorescent nanoparticle probes (e.g., quantum dots or nanoclusters, metal-organic frameworks, polymers, complexes) used as bioanalytical tools in various assays over the last three years. We also delved into their detective mechanisms, specific application areas, and characterization tools for responsive behavior. This review aims to showcase the most recent and comprehensive research progress in fluorescent bioanalysis based on molecular and nanoparticle probes, offering guidance for future developments in the design and fabrication of fluorescent probes and their potential applications.

Nanomaterials as lubricating oil additives have attracted significant attention because of their designable composition and structure, suitable mechanical property, and tunable surface functionalities. However, the poor compatibility between nanomaterials and base oil limits their further applications. In this work, we demonstrated oil-soluble poly (lauryl methacrylate) (PLMA) brushes-grafted metal-organic frameworks nanoparticles (nanoMOFs) as lubricating oil additives that can achieve efficient friction reduction and anti-wear performance. Macroinitiators were synthesized by free-radical polymerization, which was coordinatively grafted onto the surface of the UiO-67 nanoparticles. Then, PLMA brushes were grown on the macroinitiator-modified UiO-67 by surface-initiated atom transfer radical polymerization, which greatly improved the lipophilic property of the UiO-67 nanoparticles and significantly enhanced the colloidal stability and long-term dispersity in both non-polar solvent and base oil. By adding UiO-67@PLMA nanoparticles into the 500 SN base oil, coefficient of friction and wear volume reductions of 45.3% and 75.5% were achieved due to their excellent mechanical properties and oil dispersibility. Moreover, the load-carrying capacity of 500 SN was greatly increased from 100 to 500 N by the UiO-67@PLMA additives, and their excellent tribological performance was demonstrated even at a high friction frequency of 65 Hz and high temperature of 120 °C. Our work highlights oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient lubricating additives.

Semiconductive metal–organic frameworks (MOFs) have attracted great interest for the electronic applications. However, dark currents of present hybrid organic–inorganic materials are 1000–10,000 times higher than those of commercial inorganic detectors, leading to poor charge transportation. Here, we demonstrate a ZIF-8 (Zn(mim)₂, mim = 2-methylimidazolate) wafer with ultra-low dark current of 1.27 pA·mm⁻² under high electric fields of 322 V·mm⁻¹. The isostatic pressing preparation process provides ZIF-8 wafers with good transmittance. Besides, the presence of redox-active metals and small spatial separation between components promotes the charge hopping. The ZIF-8-based semiconductor detector shows promising X-ray detection sensitivity of 70.82 μC·Gy⁻¹·cm⁻² with low doses exposures, contributing to superior X-ray imaging capability with a relatively high spatial resolution of 1.2 lp·mm⁻¹. Simultaneously, good peak discrimination with the energy resolution of ~ 43.78% is disclosed when the detector is illuminated by uncollimated ²⁴¹Am@5.48 MeV α-particles. These results provide a broad prospect of MOFs for future radiation detection applications.

Metal-insulator-metal (MIM) cavity as a lithography-free structure to control light transmission and reflection has great potential in the field of optical sensing. However, the dense top metal layer of the MIM prohibits any external medium from entering the dielectric insulation layer, which limits the application of the cavity in the sensing field. Herein, we demonstrate a series of monolithic metal-organic frameworks (MOFs) based MIM cavities, which are treated by plasma etching to provide channels for chemical diffusion and to advance sensing. We modulate the bandwidth of the MIM filters by controlling the MOF thickness as insulator layers. Oxygen plasma-etching is applied to build channels on the top metal layer without altering their saturation and brightness for chemical sensing performance. The etching time regulates the number and size of channels on the top metal layer. Sensing behavior is demonstrated on the plasma-etched MOFs-based MIM cavity when external chemicals diffuse in the cavity. In addition, we generate patterned structure of the MOFs-based MIM cavity via plasma-mask method, which can transfer to different substrates and produce a controllable structure color change for chemical sensing. Our MIM cavity may promote the advancement and applications of structural color in security imaging, color display, information anticounterfeiting, and color printing.

Osteoarthritis (OA) treatment mainly relies on developing new drugs or nanocarriers, while little attention is paid to building novel remedial mode and improving drug loading efficiency. This work reports an integrated nanosystem that not only realizes visual drug loading and release, but also achieves enhanced lubrication and effective joint inflammation therapy based on fluorinated graphene quantum dots (FGQDs). Oxygen introduction promotes FGQDs outstanding water-stability for months, and layered nano-sized structure further guarantees excellent lubricating properties in biomimetic synovial fluid. The special design of chemistry and structure endows FGQDs robust fluorescence in a wide range of pH conditions. Also, the excitation spectrum of FGQDs well overlaps the absorption spectrum of drugs, which further constructs a new concept of internal filtering system to visually monitor drug loading by naked eyes. More importantly, extraordinary long-term lubrication performance is reported, which is the first experimental demonstration of concentration-dependent mutations of coefficient of friction (COF). Cell incubation experiments indicate that drug-loaded FGQDs have good biocompatibility, tracking property of cellular uptake and drug release, which show efficient anti-inflammation potential for H₂O₂-induced chondrocyte degradation by up-regulated cartilage anabolic genes. This study establishes a promising OA treatment strategy that enables to monitor drug loading and release, to enhance long-time lubricating property, and to show effective anti-inflammatory potential for cartilage protection.

Metal-organic framework (MOF)-on-MOF structure allows stacking various types of MOFs with different lattice constants for molecule sieving or filtering. However, the multilayered MOFs-based optical devices have incoherent interference due to the lattice-mismatch at the interface and refractive index (RI) indifference. This paper reports isostructural MOFs-based photonic crystals (PCs) designed by stacking Bragg bilayers of lattice-matched MOFs thin films through a layer-by-layer assembly method. Colloidal nanoparticles (NPs) were homogenously encapsulated in some layers of the MOFs (HKUST-1@NPs) to tune their intrinsic RI during the spraying coating process. The isostructural MOFs-based PCs were constructed on a large scale by sequentially spraying coating the low RI layer of HKUST-1 and high RI layer of HKUST-1@NPs to form the desired number of Bragg bilayers. X-ray photoelectron spectroscopy (XPS) depth profiling proved the Bragg bilayers and the homogenous encapsulation of nanomaterials in certain layers of MOFs. Bandwidth of the PCs was tailored by the thickness and RI of the Bragg bilayers, which had a great consistent with finite difference time domain (FDTD) simulation. Importantly, reflectivity of the isostructural MOFs-based PCs was up to 96%. We demonstrated high detection sensitivity for chemical sensing on the PCs, which could be advanced by encapsulating different types of nanomaterials and designing wide-band isostructural MOFs-based PCs.