Metal-Organic Framework-Derived ZnO, N Dually Doped Nanocages as an Efficient Host for Stable Li Metal Anodes.

The drastic volume expansion and dendrite growth of lithium metal anodes give rise to poor electrochemical reversibility. Herein, ZnO, N dually doped nanocages (c-ZNCC) were synthesized as the host for lithium metal anodes using the zeolitic imidazolate framework-8 (ZIF-8). The synthesis is based on a two-step core@shell evolution mechanism, which could guide lithium deposition rapidly and offer a fast lithium-ion diffusion during the cycling process. Benefiting from the unique design, the as-obtained c-ZNCC can render a record short lithium infusion as low as 1.5 s, a stable lithium stripping/plating capability as long as 3000 h, and a voltage hysteresis of 95 mV when cycling at 10 mA cm-2 to 10 mA h cm-2. A low Tafel slope of 3.45 mA cm-2 demonstrates the efficient charge transfer of c-ZNCC-Li, and the galvanostatic intermittent titration technique measurement shows high diffusion coefficient of c-ZNCC-Li during the charging process. In addition, the LNMO||c-ZNCC-Li cell exhibits a capacity retention as high as 93.7% at 1 C after 200 cycles. This work creates a new design for deriving nanocages with dual lithiophilic spots using a metal-organic framework and carbon cloth for favorable Li metal anodes.

Novel design constructed In2S3@SnO2 hollow heterojunctions by insufficiently etched MOFs as framework for photoelectrochemical bioanalysis.

Compared to sufficiently etched MOFs materials, insufficiently etched MOFs materials tend to display unsatisfactory performance due to their immature structure and have been eliminated from scientific research. Herein, this work reported a novel In2S3@SnO2 heterojunction (In2S3@SnO2-HSHT) materials, which were stably synthesized in high temperature aqueous environment and equipped extraordinary photoelectrochemical (PEC) properties, fabricated by a succinct hydrothermal synthesis method using insufficiently etched MIL-68 as a self-sacrificing template. Compared with the control groups and In2S3@SnO2 heterojunctions with collapse morphology synthesized by sufficiently etched MIL-68 in high temperature aqueous environment, In2S3@SnO2-HSHT synthesized from insufficiently etched MIL-68 as a template had a massively enhanced light-harvesting capability and generated more photoinduced charge carriers due to its well-preserved hollow structure. Therefore, based on outstanding PEC performance of In2S3@SnO2-HSHT, the established PEC label-free signal-off immunosensor to detect CYFRA 21-1, revealing vivid selectivity, stability, and reproducibility. This novel strategy adopted the insufficient chemical etching method neglected by the mainstream chemical etching approaches, which solved the challenge that the stability of the sufficient etched MOFs with hollow structure cannot be maintained under the subsequent high temperature aqueous reaction conditions, and was further applied to the design of hollow heterojunction materials for photoelectrochemical fields.

Janus (Mo/ß-Mo2C)@C heterostructure as an efficient electrocatalyst for the hydrogen evolution reaction in acidic and alkaline media.

To explore low-cost, high-efficiency, and noble-metal-free catalysts for electrocatalytic water splitting in both acidic and alkaline media, the metal-metal carbide Janus hierarchical structure comprising Mo andß-Mo2C embedded on a carbon layer (Mo/ß-Mo2C)@C is synthesized by a hydrothermal reaction and subsequent low-temperature magnesium thermic process. Systematic characterization by XRD, XPS, Raman scattering, and SEM/TEM reveals the successful formation of metallic Mo andß-Mo2C nanoparticles. The synthesized (Mo/ß-Mo2C)@C has a large specific surface area and boasts highly efficient hydrogen evolution reaction activity including low overpotentials of 152 and 171 mV at a current density of 10 mA cm-2and small Tafel slopes of 51.7 and 63.5 mV dec-1in acidic and alkaline media, respectively. In addition, the catalyst shows outstanding stability for 48 h in both acidic and alkaline media. The excellent catalytic activity originates from more active sites and greater electron conductivity bestowed by the carbon layer, which also improves the long-term stability in both acidic and alkaline solutions.

Highly Durable and Efficient Ni-FeOx/FeNi3 Electrocatalysts Synthesized by a Facile In Situ Combustion-Based Method for Overall Water Splitting with Large Current Densities.

Ni-/Fe-based materials are promising electrocatalysts for the oxygen evolution reaction (OER) but usually are not suitable for the hydrogen evolution reaction (HER). Herein, a durable and bifunctional catalyst consisting of Ni-FeOx and FeNi3 is prepared on nickel foam (Ni-FeOx/FeNi3/NF) by in situ solution combustion and subsequent calcination to accomplish efficient alkaline water splitting. Density functional theory (DFT) calculation shows that the high HER activity is attributed to the strong electronic coupling effects between FeOx and FeNi3 in the Janus nanoparticles by modulating ΔGH* and electronic states. Consequently, small overpotentials (η) of 71 and 272 mV in HER and 269 and 405 mV in OER yield current densities (j) of 50 and 1000 mA cm-2, respectively. The catalyst shows outstanding stability for 280 and 200 h in HER and OER at a j of ∼50 mA cm-2. Also, the robustness and mechanical stability of the electrode at an elevated j of ∼500 mA cm-2 are excellent. Moreover, Ni-FeOx/FeNi3/NF shows excellent water splitting activities as a bifunctional catalyst as exemplified by j of 50 and 500 mA cm-2 at cell voltages of 1.58 and 1.80 V, respectively. The Ni-FeOx/FeNi3/NF structure synthesized by the novel, simple, and scalable strategy has large potential in commercial water electrolysis, and the in situ combustion method holds great promise in the fabrication of thin-film electrodes for different applications.

Rationally constructed ZnCdS-HDCs@In2S3-HNRs double-hollow heterojunction with promoted light capture capability for photoelectrochemical biosensing.

The construction of novel heterojunction is regarded as an operative scheme to promote the transport of photogenerated carriers and reduce electron-hole pair recombination to enhance the photoelectrochemical (PEC) performances. Herein, ZnCdS hollow dodecahedral nanocages (ZnCdS-HDCs) and In2S3 hollow nanorods (In2S3-HNRs), which were derived from two different of metal-organic frameworks (MOFs) by solvothermal sulfidation method and were constructed an original double-hollow heterostructure ZnCdS-HDCs@In2S3-HNRs. The intrinsic mechanism of In2S3-HNRs benefiting from unique morphology to boost the photochemical properties under visible light irradiation was illustrated. Meanwhile, the mechanism of the novel type II heterojunction with staggered matching levels was revealed, which could effectively restrict electron-hole pair reassociation separation, and accelerated charge separation and transfer. Therefore, based on the excellent PEC performance of ZnCdS- HDCs@In2S3-HNRs double-hollow heterostructure, a signal-off PEC biosensor platform without labeled was constructed for the detection of CA15-3, which manifested acceptable specificity, reproducibility and stability. Additionally, the expected PEC biosensors showed a linear response range from 1.0 × 10-5 to 10 U·mL-1 in addition to an ultralow detection limit of 3.78 × 10-6 U·mL-1. This study innovatively constructed and prepared a new double-hollow heterojunction material with superior PEC nature for the application of PEC biosensing, which exhibits a broad application prospect.

Growth of 1D Nanorod Perovskite for Surface Passivation in FAPbI3 Perovskite Solar Cells.

The regulation of perovskite crystallization and nanostructure have revolutionized the development of high-performance perovskite solar cells (PSCs) in recent years. Yet the problem of stably passivating perovskite surface defects remains perplexing. The 1D perovskites possess superior physical properties compared with bulk crystals, such as excellent moisture stability, self-healing property, and surface defects passivation. Here, 4-chlorobenzamidine hydrochloride (CBAH) is developed as spacer to form orientationally crystallized nanorod-like 1D perovskite on the top surface of 3D perovskite for surface passivation of FAPbI3 perovskite. Further structure characterizations indicate the coexistence of 1D-3D hybrid perovskite lattices in nanorod-like perovskite passivation layer, which regulates the crystallization and morphology effectively and assists in promoting charge extraction, and suppressing charge recombination. As a result, the CBAH treated FAPbI3 -based PSCs exhibit a boosted power conversion efficiency of 21.95%. More importantly, the resultant unencapsulated devices display improved thermal, moisture, and illumination stability, and high reproducibility in terms of device performance. These results indicate the potential of organic halide salts for regulation of perovskite crystallization, offering a promising route of utilizing 1D perovskites nanorods in photovoltaic fields.

Enhanced photocatalytic degradation of 4-chlorophenol under visible light over carbon nitride nanosheets with carbon vacancies.

Two-dimensional graphitic carbon nitride (g-C3N4, GCN) is considered as one of the promising visible light-responsive photocatalysts for energy storage and environmental remediation. However, the photocatalytic performance of pristine GCN is restricted by the inherent shortcomings of rapid charge carrier recombination and limited absorption of visible light. Vacancy engineering is widely accepted as the auspicious approach for boosting the photocatalytic activity of GCN-based photocatalysts. Herein, a magnesium thermal calcination method has been developed to reconstruct GCN, in which magnesium serves as a carbon etcher for introducing carbon vacancies and pores into GCN (Vc-GCN). The fabricated Vc-GCN demonstrates excellent photocatalytic performances of degrading hazardous 4-chlorophenol under visible light irradiation benefiting from the improved carrier separating and light absorption ability as well as rich reactive sites. The optimal Vc-GCN sample delivers 2.3-fold enhancement from the pristine GCN. The work provides a tactic to prepare GCN photocatalysts with controllable carbon vacancies and for a candidate for the degradation of organic pollutants from the environment.

Porous hollow carbon nanobubbles@ZnCdS multi-shelled dodecahedral cages with enhanced visible-light harvesting for ultrasensitive photoelectrochemical biosensors.

Herein, novel photoactive materials, MOF-derived porous hollow carbon nanobubbles@ZnCdS multi-shelled dodecahedral cages (C@ZnCdS MSDCs)， were synthesized via continuous chemical etching, sulfurization, cation-exchange and calcination strategies. Due to the synergistic effect between the porous shells and the carbon-layer coating， C@ZnCdS MSDCs displayed superior photoelectrochemical (PEC) performance. The synthesized C@ZnCdS MSDCs were assembled onto TiO2 modified ITO electrodes to form a type-II heterostructures. Then, Au nanoparticles (NPs) were deposited on the surface of ITO/TiO2/C@ZnCdS MSDCs. Benefiting from the unique structure and performance merits of photoactive materials, a label-free PEC sensing platform based on ITO/TiO2/C@ZnCdS MSDCs/Au was successfully constructed for CEA detection. Under optimal conditions, the PEC biosensor exhibited a wide linear range (0.00005-500 ng mL-1) and low detection limit (2.28 fg mL-1). The proposed PEC biosensor also showed good stability, specificity, reproducibility and acceptability in human serum. The prepared C@ZnCdS MSDCs would be a promising photoactive material for PEC biosensors. Most importantly, this work opens up new horizons for the application of MOFs-derived hollow carbon materials in sensing.

Synthesis and Applications of Graphdiyne-Based Metal-Free Catalysts.

The development of carbon materials offers the hope for obtaining inexpensive and high-performance alternatives to substitute noble-metal catalysts for their sustainable application. Graphdiyne, the rising-star carbon allotrope, is a big family with many members, and first realized the coexistence of sp- and sp2 -hybridized carbon atoms in a 2D planar structure. Different from the prevailing carbon materials, its nonuniform distribution in the electronic structure and wide tunability in bandgap show many possibilities and special inspirations to construct new-concept metal-free catalysts, and provide many opportunities for achieving a catalytic activity comparable with that of noble-metal catalysts. Herein, the recent progress in synthetic methodologies, theoretical predictions, and experimental investigations of graphdiyne for metal-free catalysts is systematically summarized. Some new perspectives of the opportunities and challenges in developing high-performance graphdiyne-based metal-free catalysts are demonstrated.

A Universal Strategy for Constructing Seamless Graphdiyne on Metal Oxides to Stabilize the Electrochemical Structure and Interface.

The structural and interfacial stabilities of metal oxides (MOs) are key issues while facing the volumetric variation and intensive interfacial polarization in electrochemical applications, including lithium-ion batteries (LIBs), supercapacitors, and catalysts. The growth of a seamless all-carbon interfacial layer on MOs with complex dimensions is not only a scientific problem, but also a practical challenge in these fields. Here, the growth of graphdiyne under ultramild condition is successfully implemented in situ for coating MOs of complex dimensions. The seamless all-carbon interface and conductive network are formed at the same time. This method cleverly avoids the structural degradation of MOs at a high temperature in the presence of traditional carbon materials. Under the protection of the high-quality graphdiyne layer, the samples as LIB anodes deliver high performances in terms of Coulomb efficiency, capacity, long-term retention, and structural and interfacial stabilities. Both experimental achievements and theoretical calculations demonstrate that the graphdiyne is a particular protection layer for MOs and plays a crucial role for preventing the structural and interfacial degradation of the electrode. Furthermore, the universality of this method will promote the potential applications of many promising MOs in other electrochemical fields.

Graphdiyne as a Host Active Material for Perovskite Solar Cell Application.

This work demonstrates a novel photovoltaic application in which graphdiyne (GD) can be employed as a host material in a perovskite active layer for the first time. In the device fabrication, the best molar ratio for active materials is verified as PbI2/MAI/GD being 1:1:0.25, yielding a peak power-conversion efficiency of 21.01%. We find that graphdiyne, as the host material, exerts significant influence on the crystallization, film morphology, and a series of optoelectronic properties of the perovskite active layer. A uniform MAPbI3 film with highly crystalline qualities, large domain sizes, and few grain boundaries was realized with the introduction of graphdiyne. Moreover, the current-voltage hysteresis was negligible, and device stability was significantly improved as well. The results indicate that graphdiyne as the host active material presents great potential for the enhancement of the performance of perovskite solar cells.

Ternary CuZnS Nanocrystals: Synthesis, Characterization, and Interfacial Application in Perovskite Solar Cells.

Ternary CuZnS nanocrystals (NCs) are synthesized via a facile, scalable, noninjection method at low temperatures for the first time, wherein sodium ascorbate plays the dual roles of reducing agent and capping ligand in the preparation process. These NCs can be dispersed well in a polar solvent like dimethyl sulfoxide, and the average size is ∼4 nm as measured by transmission electron microscopy. The results of X-ray diffraction and X-ray photoelectron spectroscopy indicate that the crystal structure of CuZnS NCs displays covellite CuS-like structure and the Zn element partly occupies the Cu position. Also, the crystal structure of CuZnS NCs is completely converted from a covellite CuS structure into a digenite Cu9S5 structure when the NCs are treated above 350 °C. Moreover, CuZnS NCs demonstrate favorable hole transport properties. When it is employed in MAPbI3-based perovskite solar cells as a hole transport layer, a peak power conversion efficiency of 18.3% is achieved. Simultaneously, the devices based on CuZnS exhibit a remarkably reduced J-V hysteresis. The results indicate that CuZnS is a promising hole transport layer for enhancing perovskite solar cell performance and presents great potential for optoelectronic applications, as well.

Efficient detection of hazardous catechol and hydroquinone with MOF-rGO modified carbon paste electrode.

Reduced graphite oxide (rGO) was incorporated into a metal organic framework (MOF) MIL-101(Cr) for the modification of carbon paste electrode. Taking advantages of the large surface area of MOF and the electrical conductivity of rGO, the resulted electrodes exhibited high sensitivity and reliability in the simultaneous electrochemical identification and quantification of catechol (CC) and hydroquinone (HQ). Specifically, in the mixture solution of catechol and hydroquinone (constant concentration of an analyte), the linear response ranges for catechol and hydroquinone were 10-1400 µM and 4-1000 µM, and detection limits were 4 µM and 0.66 µM (S/N = 3) for individual catechol and hydroquinone, respectively. Therefore, the relatively easy fabrication of modified CPE and its fascinating reliability towards HQ and CC detection may simulate more research interest in the applications of MIL-101(Cr)-rGO composites for electrochemical sensors.

A photoelectrochemical aptasensor for thrombin based on the use of carbon quantum dot-sensitized TiO2 and visible-light photoelectrochemical activity.

A photoelectrochemical (PEC) aptasensor for the highly sensitive and specific detection of thrombin is described. This aptasensor is based on an indium tin oxide (ITO) support that is covered with carbon quantum dot (CQD)-sensitized TiO2 and acts as a photoactive matrix. The ITO/TiO2/CQD electrode was prepared by impregnation assembly. It displays an enhanced and steady photocurrent response under irradiation by visible light. A carboxyl-functionalized thrombin-binding aptamer was covalently immobilized on the modified ITO to obtain a PEC aptasensor whose photocurrent decreases with increasing concentration of thrombin. Under 420 nm irradiation at a bias voltage of 0 V, the aptasensor has a linear response in the 1.0 to 250 pM thrombin concentration range, with a 0.83 pM detection limit. Conceivably, this approach can be extended to numerous other PEC aptasensors for the detection of targets for which appropriate aptamers are available. Graphical abstract Schematic of a PEC aptasensor for thrombin. It is based on the use of CQD as the sensitizer, TiO2/CQDs as the photoactive matrix, and the thrombin aptamer as the recognition element.

Facile preparation and characterization of ZnCdS nanocrystals for interfacial applications in photovoltaic devices.

Recently, ZnCdS nanocrystals (NCs) have attracted intense attention because of their specific optical properties and electrical characteristics. In this paper, a green and facile solution method is reported for the preparation of ZnCdS nanocrystals using dimethylsulfoxide as small molecular ligands. The ZnCdS nanocrystals are used as an interface modification material in the photovoltaic devices. It is found that the modification of ZnCdS on TiO2 surface not only suppresses the recombination loss of carriers but also reduces the series resistance of TiO2/active layer. Consequently, both of the short circuit current (Jsc) and the fill factor (FF) of the solar cells were significantly improved. Power conversion efficiency (PCE) of 7.75% based on TiO2/ZnCdS was achieved in contrast to 6.65% of the reference devices based on pure TiO2 film in organic solar cells. Furthermore, the PCE of perovskite solar cells based on TiO2/ZnCdS was observed with 8.3% enhancement compared to that of pure TiO2-based ones.

Photoacoustic stimulation promotes the osteogenic differentiation of bone mesenchymal stem cells to enhance the repair of bone defect.

The aim of this study was to evaluate the direct photoacoustic (PA) effect on bone marrow mesenchymal stem cells (BMSCs) which is a key cell source for osteogenesis. As scaffold is also an indispensable element for tissue regeneration, here we firstly fabricated a composited sheet using polylactic-co-glycolic acid (PLGA) mixing with graphene oxide (GO). BMSCs were seeded on the PLGA-GO sheets and received PA treatment in vitro for 3, 9 and 15 days, respectively. Then the BMSCs were harvested and subjected to assess alkaline phosphatase (ALP) activity, calcium content and osteopontin (OPN) on 3, 9 and 15 days. For in vivo study, PLGA-GO sheet seeded with BMSCs after in vitro PA stimulation for 9 days were implanted to repair the bone defect established in the femoral mid-shaft of Sprague-Dawley rat. PLGA-GO group with PA pretreatment showed promising outcomes in terms of the expression of ALP, OPN, and calcium content, thus enhanced the repair of bone defect. In conclusion, we have developed an alternative approach to enhance the repair of bone defect by making good use of the beneficial effect of PA.

An Exceptionally Water Stable Metal-Organic Framework with Amide-Functionalized Cages: Selective CO2 /CH4 Uptake and Removal of Antibiotics and Dyes from Water.

As the main organic pollutants in wastewater, antibiotics and organic dyes are harmful to the environment and public health, and their removal is important but challenging. In this work, highly porous 3D metal-organic frameworks (MOFs) [M2 (PDAD)(H2 O)]n (PCN-124-stu; M=Cu, Zn; H4 PDAD = 5,5'-(pyridine-3,5-dicarbonyl)bis(azanediyl)diisophthalic acid) were synthesized, and PCN-124-stu(Cu) shows excellent chemical and thermal stability. PCN-124-stu(Cu) was used as a host for efficient extraction of various organic dyes, especially the large-molecule dye Coomassie brilliant blue, and fluoroquinolones from water, in comparison with five common MOFs, zeolite 13X, and activated carbon. PCN-124-stu(Cu) exhibits absolute predominance for fluoroquinolone adsorption among these microporous materials because of the H-bonds between fluoroquinolone molecules and the amide groups in the frameworks, except for MIL-100(Cr), which is a mesoporous MOF. Moreover, PCN-124-stu(Cu) could release fluoroquinolones slowly in physiological saline and retained its framework structure after four adsorption/desorption cycles. In addition, PCN-124-stu(Cu) can be used as a platform for selective adsorption of CO2 /CH4.

A novel and sensitive fluorescence sensor for glutathione detection by controlling the surface passivation degree of carbon quantum dots.

A novel fluorescence sensor based on controlling the surface passivation degree of carbon quantum dots (CQDs) was developed for glutathione (GSH) detection. First, we found that the fluorescence intensity of the CQDs which was obtained by directly pyrolyzing citric acid would increased largely after the surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). In the light of this phenomenon, we designed a simple, rapid and selective fluorescence sensor based on the surface passivated CQDs. A certain and excess amount of EDC were mixed with GSH, part of EDC would form a stable complex with GSH owing to the exposed sulfhydryl group of GSH. As the synthesized CQDs were added into the above mixture solution, the fluorescence intensity of the (EDC/GSH)/CQDs mixture solution could be directly related to the amount of GSH. Compared to other fluorescence analytical methods, the fluorescence sensor we design is neither the traditional fluorescent "turn on" probes nor "turn off" probes. It is a new fluorescence analytical method that target object indirectly control the surface passivation degree of CQDs so that it can realize the detection of the target object. Moreover, the proposed method manifested great advantages including short analysis time, low cost and ease of operation.

Boron Nitride Nanosheet-Anchored Pd-Fe Core-Shell Nanoparticles as Highly Efficient Catalysts for Suzuki-Miyaura Coupling Reactions.

Boron nitride nanosheets (BNNS) were used to anchor bimetallic Pd-Fe nanoparticles for Suzuki-Miyaura coupling catalysts. The bimetallic nanoparticles were found to be core-shell in structure, and their formation was likely facilitated by their interactions with the BNNS. The Pd-Fe/BNNS catalysts were highly effective in representative Suzuki-Miyaura reactions, with performances matching or exceeding those of the state-of-the-art methods. Specifically, the superior catalytic activities were characterized by generally shortened reaction times, minimal Pd usage, excellent reusability of the catalysts and high or nearly quantitative conversion yields in a benign solvent system without the need for any special conditions, such as ligands and surfactants or inert gas protection. The obvious advantages of the Pd-Fe/BNNS over similar catalysts based on other supports, such as reduced graphene oxide (rGO), suggest that BNNS may be developed into a versatile platform for many other important catalytic reactions.