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Residual antibiotic tetracycline (TC) that is hard to degrade and active has adversely affected public health and ecosystems. Therefore, developing straightforward, rapid, and sensitive probes for TC detection is highly desirable. Herein, we present a facile yet versatile strategy to design and fabricate luminescence turn-on TC sensors by applying the concept of indicator displacement to metal–organic frameworks (MOFs). It is illustrated by an elaborated dual-emitting nanoporous europium–MOF (Eu–MOF) constructed by Eu3+ cations and 2-aminoterephthalic acid (BDC-NH2), in which the former serves as receptors and the latter acts as luminescent indicators. The indicator displacement is based on the competitive interactions within Eu–MOF, which is confirmed by high-resolution mass spectrometry, photoluminescence, and UV–vis spectroscopy. Once Eu–MOF contacts TC, the competitive coordination effect induces the release of BDC-NH2 molecules and the accompanying turn-on blue emission, whereas the red emission of Eu3+ barely changes, thereby resulting in a remarkable ratiometric luminescence response and luminescence color switching from red to blue that is readily observed by the naked eye. The sensitive and quantitative determination of TC is accomplished through multiple readouts involving ratiometric emission intensity and emission color, exhibiting detection limits of 0.08 and 0.95 μM, respectively. Notably, the visual detection of TC is achieved using a smartphone color-scanning app. Considering the excellent tunability in the composition and structure of MOFs and their compatibility with various host–guest interactions applicable to indicator displacement assays, this study helps to create a universal avenue for leveraging MOFs in constructing luminescence turn-on sensors. [ABSTRACT FROM AUTHOR]

Hollow discontinuous Ge/GeO2 nanotubes are successfully prepared after the facile oxidization process in air, which are derived from the C/Ge core–shell nanofibers. Electrospinning and chemical vapor deposition techniques are used to fabricate the carbon nanofiber templates and the Ge shell electrode, respectively. Compared with the C/Ge nanocomposites, the Ge/GeO2 nanotube anode demonstrates improved electrochemical performance due to the enlarged surface area and enough space, which can effectively retard the Ge electrode large volume change during repeated cycling. Full‐battery Ge/GeO2||LiCoO2 is also configured and displays good Li‐ion storage ability. [ABSTRACT FROM AUTHOR]

Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next‐generation high energy‐density lithium‐ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site‐selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd3‾ m structure. This site‐selective doping not only suppresses unfavorable two‐phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg‐doped LNMOs exhibit extraordinarily stable electrochemical performance in both half‐cells and prototype full‐batteries with novel TiNb2O7 counter‐electrodes. This work pioneers an atomic‐doping engineering strategy for electrode materials that could be extended to other energy materials to create high‐performance devices. [ABSTRACT FROM AUTHOR]

1-Hydroxypyrene (1-HP) is a urinary metabolite of polycyclic aromatic hydrocarbons (PAHs), and can function as a convenient biomarker for human intoxication of PAH carcinogens. The development of simple 1-HP sensors with high sensitivity and fast response is highly desirable. Herein, we demonstrate that a robust microcrystalline MOF with fluorescent pyrene cores, NU-1000, exhibits sensitive luminescence detection of urinary 1-HP. The pyrene core within NU-1000 behaves as the signal converter, whose luminescence is significantly quenched upon coming into contact with 1-HP owing to the efficient π–π charge transfer interactions between highly conjugated 1-HP and pyrene cores in NU-1000. The pore confinement effect of the molecular-sized channel of NU-1000 facilitates the preconcentration of 1-HP within NU-1000, which makes 1-HP contact with NU-1000 more sufficient therefore enhancing the detection efficiency. The charge transfer-related quenching mechanism is elucidated by diffuse-reflectance UV-vis and electron paramagnetic resonance (EPR) measurements, and a radical pair state is observed in NU-1000 upon accommodation of 1-HP. This work provides important insights into the development of MOF-based luminescent sensors for 1-HP, and should stimulate further studies toward designing more efficient MOFs with highly conjugated luminescent cores for 1-HP sensing. [ABSTRACT FROM AUTHOR]

Dipicolinic acid (DPA) can serve as a convenient biomarker for Bacillus anthracis, which is an extremely hazardous pathogen and can be used as a biological weapon. Herein, we demonstrate a ratiometric luminescent sensor of DPA based on a dual-emissive MOF hybrid, which is developed by encapsulation of Tb3+ cations into an anionic MOF through a cation exchange process. The Tb3+@MOF hybrid well inherits the intrinsic ligand emission of the host framework and the Tb3+ emission. The parent framework can function as a host matrix to sensitize and protect the emission of incorporated Tb3+. The Tb3+ emission within the MOF hybrid is significantly enhanced in the presence of DPA molecules owing to the occurrence of antenna sensitization upon the formation of the Tb–DPA complex, while the ligand emission is insensitive to DPA. This unique ratiometric luminescence response of the Tb3+@MOF hybrid towards DPA can be exploited for sensitive self-calibrated detection of DPA. The Tb3+@MOF sensor shows a fast response rate, high sensitivity and selectivity with a limit of detection of 3.6 nM. Besides, the feasibility of this sensor operating in real samples is demonstrated by the good recovery of DPA in human serum. The present study provides a promising luminescent platform for routine analysis of an anthrax biomarker. [ABSTRACT FROM AUTHOR]

In this paper, we put forward a strategy to assemble a novel series of multi-component photofunctional hybrid materials (named as Eu-Si-P1(2,3)) centered with europium polyoxometalates (Na9EuW10O36·32H2O, abbreviated as EuW10) and polyester modified silane (P1-Si, P2-Si, P3-Si, P1 = poly glycohol, P2 = bis(2-hydroxyethyl)ether, P3 = 2-hydroxyethyl methacrylate) through an ionic liquid compound (1-methyl-3-(trimethoxysilylpropyl) imidazolium chloride, IM+Cl−) as the double functional linker. Furthermore, using Pluronic P123 surfactant as a template to control the sol–gel process of organically modified siloxane precursors, Eu-SBA15-P1(2,3) hybrids with mesoporous silica are constructed correspondingly. The results reveal that Eu-Si-P1(2,3) hybrids present the lower red/orange intensity ratio, longer lifetime and higher quantum yield than Eu-SBA15-P1(2,3) hybrids. The luminescent lifetime and quantum efficiency of Eu-Si-P1(2,3) hybrids are comparable with EuW10 compounds in spite of their low concentration of photoactive EuW10, which is important for practical applications. The CIE chromatic coordinates of some systems are close to the cool-white region and can be expected to be utilized as cool white lighting (close to sunlight). [ABSTRACT FROM AUTHOR]

Aqueous ZIBs are one of the most promising next-generation rechargeable batteries because of the high capacity, high hydrogen evolution overpotential, and chemically stable reversible plating/stripping of the zinc electrode in the mild aqueous electrolyte. However, there are limited cathode materials that can store Zn 2+ reversibly with superior cycling and rate capability. Herein, hierarchically porous nanorods composed of twinborn α-(Mn 2 O 3 -MnO 2 ) heterostructures are proposed as a robust cathode for Zn storage. Thanks to the hierarchically porous nanorod morphology and the abundant interface of the heterostructures involving a built-in electric field, the as-obtained twinborn α-(Mn 2 O 3 -MnO 2 ) electrode delivers a high capacity of 170 mA h g -1 for 2000 cycles at 500 mA g -1 and shows an excellent rate capability of up to 1.5 A g -1 with a capacity of 124 mA h g -1 . The inspiring results achieved exhibit the enormous potential of the high-performance heterostructure cathode for fast and stable ZIBs.

As an important class of multielectron reaction materials, the applications of transition-metal oxides (TMOs) are impeded by volume expansion and poor electrochemical activity. To address these intrinsic limitations, the renewal of TMOs inspires research on incorporating an advanced interface layer with multiple anionic characteristics, which may add functionality to support properties inaccessible to a single-anion TMO electrode. Herein, a transition-metal oxycarbide (TMOC, M = Mo) with more than one anionic species was prepared as an interface layer on a corresponding oxide. A multiple anionic TMOC possesses advantages of structural stability, abundant active sites, and elevated metal cation valence states. Such merits mitigate volume changes and enhance multielectron reactions significantly. The TMOC nanocomposite has a well-maintained capacity after 1000 cycles at 2 A·g -1 and fully resumed rate performance. In situ synchrotron X-ray powder diffraction (SXRPD) analysis unveils negligible volume expansions occurring upon oxycarbide layer coupling, with lattice spacing variation less than 1% during cycling. The lithium storage mechanism is further inspected by combined analysis of kinetics, SXRPD, and first-principles calculations. Superior to TMO, multielectron reactions of the TMOC electrode have been boosted due to easier rupture of the metal-oxygen bond. Such improvements underscore the importance of incorporating an oxycarbide configuration as a strategy to expand applications of TMOs.