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Mixed multiple oxidation states CoMoO4 nanowires (electrocatalysts) with tunable intrinsic oxygen vacancies were fabricated. CoMoO4 with proper oxygen vacancy can be employed to construct a Li-air battery with a high capacity and stable cyclability. This is possible because CoMoO4 contains surface oxygen vacancies, which result in the unit of CoMo bond, that is important for electrocatalysts used in Li-air batteries. Both the experimental and theoretical results demonstrate that the surface oxygen vacancies containing CoMoO4 nanowires have a higher electrocatalytic activity. This shows that the highly efficient electrocatalysts used for Li-air batteries were designed to modify the redox properties of the mixed metal oxide in the catalytic active sites. This successful material design led to an improved strategy for high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities based on the fast formation and extinction of ORR products.

Reasonably regulating electronic coupling to promote charge transfer and exciton separation has been regarded a promising approach in catalysis. The material engineering of van der Waals heterojunction (vdWsH) based on two-dimensional (2D) materials would be a potential way to optimize the as-prepared extrinsic physicochemical characteristics. However, it was still an almost uncultivated land waiting for exploration in catalysis. Herein, we introduced the inert h-boron nitride (h-BN) in non-metal reduced graphene oxide (GN) catalysts and constructed BN-GN vdWsH. The theoretical calculation demonstrated that the h-BN can effectively modify the electronic properties of graphene. With the introduction of h-BN, the BN-GN vdWsH can obviously enhance the catalytic activity of Li-CO2 battery. The existence of BN-GN vdWsH can reduce the overpotential more than 700 mV compared with reduced graphene oxide during the CO2 reduction reaction (CO2RR) and CO2 evolution reaction (CO2ER), and it extended cyclic stability more than three times, which was one of the most outstanding non-metallic catalysts. The reasonable structure design made it work as a high efficient electrocatalyst, which shed light on the development for functional treatment of catalytic materials.

Combining nanomaterials with complementary properties in a well-designed structure is an effective tactic to exploit multifunctional, high-performance materials for the energy conversion and storage. Nonprecious metal catalysts, such as cobalt oxide, with superior activity and excellent stability to other catalysts are widely desired. Nevertheless, the performance of CoO nanoparticles as an electrode material were significantly limit for its inferior conductivity, dissolution, and high cohesion. Herein, we grow ultrafine cobalt monoxide to decorate the interlayer and surface of the Ti3C2Tx nanosheets via a hydrothermal method companied by calcination. The layered MXenes act as the underlying conductive substrate, which not only increase the electron transfer rate at the interface but also greatly improve the electrochemical properties of the nanosized CoO particles by restricting the aggregation of CoO. The resulting CoO/Ti3C2Tx nanomaterial is applied as oxygen electrode for lithium-oxygen battery and achieves more than 160 cycles and first cycle capacity of 16,220 mAh g−1 at 100 mA g−1. This work paves a promising avenue for constructing a bi-functional catalyst by coupling the active component of a transition metal oxide (TMO) with the MXene materials in lithium-oxygen battery.

Urea, as a prospective energy source, is rarely utilized for lack of effective catalysts to overcome its sluggish kinetics during its electrolysis. Exploiting low-cost and high-efficiency catalysts to accelerate the urea oxidation reaction (UOR) does make sense as it can relieve not only energy shortage but also the water contamination problems. In this work, the Ni₃S₂ nanosheets grown on the Ni foam with different amounts of Mn²⁺ doping were developed as useful electrocatalysts toward UOR. The experimental and computational methods were performed to explore the properties of obtained samples. We found that the doping of Mn²⁺ could distinctly regulate the charge distribution of Ni₃S₂ by which the performance was observably optimized. We also compared the behaviors of obtained catalysts with various dopant concentrations of Mn²⁺. Especially, Ni₃S₂ grown on the Ni foam with the addition of 0.2 mmol of Mn²⁺ exhibits splendid properties with a lower potential and superior longevity, which can achieve a current density of 100 mA cm–² at a voltage of only 1.397 V (vs reversible hydrogen electrode) in 1.0 M KOH containing 0.5 M urea solution, indicating that our findings can serve as promising electrocatalysts for urea electrolysis.

NiFe layered double hydroxides (LDHs) have been denoted as benchmark non-noble-metal electrocatalysts for the oxygen evolution reaction (OER). However, for laminates of NiFe LDHs, the edge sites are active, but the basal plane is inert, leading to underutilization as catalysts for the OER. Herein, for the first time, light and electron-deficient Li ions are intercalated into the basal plane of NiFe LDHs. The results of theoretical calculations and experiments both showed that electrons would be transferred from near Ni2+ to the surroundings of Li+ , resulting in electron-deficient properties of the Ni sites, which would function as "electron-hungry" sites, to enhance surface adsorption of electron-rich oxygen-containing groups, which would enhance the effective activity for the OER. As demonstrated by the catalytic performance, the Li-NiFe LDH electrodes showed an ultralow overpotential of only 298 mV at 50 mA cm-2 , which was lower than that of 347 mV for initial NiFe LDHs and lower than that of 373 mV for RuO2 . Reasonable intercalation adjustment effectively activates laminated Ni2+ sites and constructs the electron-deficient structure to enhance its electrocatalytic activity, which sheds light on the functional treatment of catalytic materials.

The new material Polypyrrole-Mo3S13 (abbr. Mo3S13-Ppy) is a new material prepared by ion-exchange between Ppy-NO3 and (NH4)2Mo3S13. The Mo3S13-Ppy was designed to exhibit strong selectivity for Ag+ and highly toxic Hg2+ in mixtures with other ions. It displays an apparent selectivity ranking of Hg2+ > Ag+ ≥ Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+. The strong affinity of Mo3S13-Ppy for Ag+ and Hg2+ was confirmed with extremely high distribution coefficients (Kd) (∼107 mL/g) and remarkable removal efficiencies (>99.99%), resulting in

Two-dimensional MXene, a significant member of the two-dimensional family, has attracted much interest in physics, energy evolution, environmental science, and nanomedicine. However, the acute toxi...

We develop a facile method to prepare a hierarchical mesoporous nanocomposite of manganese carbodiimide nanoparticles modified with N-doping carbon materials (MnNCN/NC). The nanocomposite is endowe...

Li–oxygen batteries (LOBs) have drawn widespread attention in the past decades. Herein, bifunctional hybrid catalysts based on perovskite La0.5Sr0.5CoO3−δ with Ti3C2Tx MXene nanosheets have been pr...

The development of highly effective, universal, and economical electrocatalysts for hydrogen evolution reaction (HER) via structure modulations remains a great challenge. Herein, we propose a novel solidoid nitridation reduction method to synthesize α-MoC1–x quantum dots encapsulated in nitrogen-doped carbon (α-MoC1–x/NC) with a shape like “frog eggs”. Carbon nitride was first prepared by pyrolysis of urea and then mixed with ammonium molybdate tetrahydrate under a temperature-programmed reduction. With the assistance of nitrogen release during thermal treatment, N doping and an ultrathin porous structure were obtained. Benefiting from the strong interaction of α-MoC1–x quantum dots and nitrogen-doped carbon, the α-MoC1–x/NC delivered an outstanding performance toward HER at all pH values. Here, 118 mV, a lower overpotential, is needed to reach 10 mA cm–2 in alkaline solution, and the current density of α-MoC1–x grew much faster than the commercial Pt/C with increased potential. And, this can keep steadil...

The development of novel and highly efficient bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an ongoing challenge. The Cr3+ cati...

The development of high-performance, low-cost, and long-lasting electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is urgently needed for effective electrochemical water splitting. In the present study, an engineering process was employed to prepare "Lewis base-hungry" amorphous-crystalline nickel borate-nickel sulfide (Ni3(BO3)2-Ni3S2) heterostructures, which exhibited unprecedentedly high electrocatalytic activity toward both OER and HER in alkaline media. The optimal Ni3(BO3)2-Ni3S2/nickel foam (Ni3(BO3)2-Ni3S2/NF) electrode displayed an ultralow overpotential of only -92 and +217 mV to reach the current density of 10 mA cm-2 for HER and OER, respectively. When the Ni3(BO3)2-Ni3S2/NF electrode was used as both the anode and cathode for overall water splitting, a low cell voltage of 1.49 V was needed to achieve the current density of 10 mA cm-2, which was superior to the performance of most noble metal-free electrocatalysts. Results from density functional theory calculations showed that the Lewis base-hungry sites in the heterostructures effectively enhanced the chemisorption of hydrogen and oxygen intermediates, a critical step in HER and OER electrocatalysis. Results from this study highlight the significance of rational design and engineering of heterostructured materials for the development of high-efficiency electrocatalysts.

Defect engineering is an important approach to enhancing the catalytic activity of a material, but there have been few reported controllable experiments due to the lack of systematic and comprehensive understanding of the effects of defects. For nanocarbon catalysts, it is still a challenge to prepare both atom-doped and defect-engineered catalysts with the desired more effective active centers, which requires an in-depth understanding of both experiment and theory. Herein, a topological rich-vacancy-defect nitrogen-doped nanocarbon (TRNC) material is constructed in situ via a simple magnesiothermic technology. It exhibits remarkable oxygen catalytic performance, which can be compared to the best metal-free bifunctional carbon electrocatalysts reported, even better than that of commercial noble-metal RuO2. Combined with density functional theory (DFT) calculations, the carbon vacancy defects with edge nitrogen doping as intrinsic active sites were found to exhibit excellent oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity. When used practically as a catalyst in Li–O2 batteries, with a capacity restriction of 500 mA h g−1, it displays a long cycling and high rate durability of over 300 cycles at 200 mA g−1. This excellent performance arises from the three-dimensional topological rich-vacancy-defect nitrogen-doped nanocarbon. The effects of vacancy sites and nitrogen doping were probed via first-principles simulations to clarify the catalytic mechanisms which contribute to this superior performance.

NiFe layered double hydroxides (NiFe-LDHs) have been regarded as significant electrocatalysts for the oxygen evolution reaction (OER). However, their overpotential must still be further reduced to enable commercial applications. Herein, a promising and highly effective "hydroxyl ions hungry" electrode structure was prepared for the first time via a two-step hydrothermal reaction procedure to enhance the surface adsorption kinetics to obtain an ultralow overpotential. The electrode exhibits OER activity with ultralow overpotentials of 203 mV and 293 mV at the current densities of 10 mA cm-2 and 100 mA cm-2, respectively, in 1.0 M KOH. These results reveal an important way to improve the catalytic performance in an alkaline medium.

An amorphous boron oxide layer has been deposited in situ on the NiCo-LDH (layered double hydroxide) nanosheet arrays via the simple chemical vapor deposition. The overpotential of the NiCo-LDHs@B2O3/carbon paper (NiCo-LDHs@B2O3/CP) electrode is only 213 mV at the current density of 10 mA cm–2 in 1 M KOH, which is 123 mV less than that of NiCo-LDHs/CP and slightly better than noble metal catalyst RuO2/CP (230 mV). What’s more, at 50 mA cm–2 in 1.0 M KOH, the overpotential of NiCo-LDHs@B2O3/CP is still kept at a low value of 320 mV much better than that of NiCo-LDHs/CP (441 mV) and RuO2/CP (373 mV). Importantly, it showed long-term electrochemical stability. The introduction of amorphous boron oxide layers can be promoted to form a borate interface, and it can effectively enhance reactivity of active species. The boron oxide shell on the surface of LDHs can protect active species stability to enhance cycling stability. This work may inspire the development of low-cost and efficient OER electrocatalysts for...

Novel structure NiO-graphene foam (NiO-GF) and Ni-graphene foam (Ni-GF) were synthesized via a simple hydrothermal method combined with high-temperature calcination. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results proved that NiO and Ni nanoparticles were uniformly distributed on the reduced graphene oxide (rGO) and the particle size was about 10 nm. Graphene foam (GF) was made by rGO with a three-dimensional reticular structure. NiO-GF and Ni-GF were used as cathode catalysts for lithium-oxygen battery and showed a specific capacity performance of 25,986 mA h g−1 and 22,035 mA h g−1 at a current density of 100 mA g−1, respectively. As a three-dimensional reticular material, GF can improve the efficiency of electron transfer and provide higher surface area for NiO and Ni to grow on, which offers more active sites for catalyst. Meanwhile, NiO and Ni are capable of reducing the energy barrier of the reaction from Li and O2 to Li2O2. Three dimensional reticular material, which is made by combining rGO and NiO or Ni together, is suitable for the catalyst of lithium-oxygen battery. The research provides a new way for developing catalyst for high performance lithium-oxygen battery.

Electrospinning and annealing methods are applied to prepare cobalt nanoparticles decorated in N-doped carbon nanofibers (Co/N-C NFs) with solid and macroporous structures. In detail, the nanocomposites are synthesized by carbonization of as-electrospun polyacrylonitrile/cobalt acetylacetonate nanofibers in an argon atmosphere. The solid Co/N-C NFs have lengths up to dozens of microns with an average diameter of ca. 500 nm and possess abundant cobalt nanoparticles on both the surface and within the fibers, and the cobalt nanoparticle size is about 20 nm. The macroporous Co/N-C NFs possess a hierarchical pore structure, and there are macropores (500 nm) and mesopores (2-50 nm) existing in this material. The saturation magnetization ( Ms) and coercivity ( Hc) of the solid Co/N-C NFs are 28.4 emu g-1 and 661 Oe, respectively, and those of the macroporous Co/N-C NFs are 23.3 emu g-1 and 580 Oe, respectively. The solid Co/N-C NFs exhibit excellent electromagnetic wave absorbability, and a minimum reflection loss (RL) value of -25.7 dB is achieved with a matching thickness of 2 mm for solid Co/N-C NFs when the filler loading is 5 wt %, and the effective bandwidth (RL ≤ -10 dB) is 4.3 GHz. Moreover, the effective microwave absorption can be achieved in the whole range of 1-18 GHz by adjusting the thickness of the sample layer and content of the dopant sample.

Due to the increasing demand for energy, improving the current density of fuel cells is an urgent issue. Here we report a bifunctional electrocatalyst for fuel cells involving methanol or formic acid oxidation. A nanocomposite consisting of 7.2 nm NiPt nanocrystals, which are grown in situ on graphene nanosheets (NiPt/GN), has been prepared via a solution thermal decomposition method. The NiPt/GN nanocatalyst presents specific activities as high as 41.1 mA cm-2 and 42.9 mA cm-2 for methanol oxidation and formic acid oxidation, respectively, outperforming most reported catalysts. Moreover, it retains 76.3% of this activity after 900 cycles of methanol oxidation. Additionally, in comparison with general NiPt nanoparticles, the NiPt/GN nanocatalyst shows higher electrocatalytic activity in methanol and formic acid oxidation. All these results indicate that ultrathin NiPt nanocrystals grown in situ on graphene nanosheet substrates can significantly improve performance as a bifunctional electrocatalyst.

Two kinds of coumarin derivatives, 7-hydroxy coumarin and 7-hydroxy-4-methyl coumarin, were intercalated into the layered europium hydroxide by ion exchange reaction. The two organic compounds, despite with the same basic structure of benzopyrone but only varied substituent groups, demonstrated much different intercalation structures. The 7-hydroxy coumarin molecules may deposite on the external surface of the layers and 7-hydroxy-4-methyl coumarin molecules corresponded to a vertical mono-layered arrangement. In addition, co-intercalation of surfactant 1-octane sulfonic acid sodium with coumarin anions into layered europium hydroxide can enlarge the interlayer distance, both of the coumarin anions located vertically in the interlayer. The thermal stability of organics was enhanced after intercalation. The combination of the coumarin anions with the positively-charged layers generated hybrid materials exhibiting versatile luminescence properties. In solid state, the luminescence of the organics and Eu3+ were co-quenched for 7-hydroxy coumarin composites, but surfactant co-intercalated 7-hydroxy-4-methyl coumarin composite showed strong violet emission. In formamide, all of the composites displayed blue emission. The energy transfer between Eu3+ and organics and the change of microenvironment were proposed to account for the versatile luminescence properties. This work benefits the improvement of stability and fluorescence property of coumarin dyes and offers a beneficial approach to fabricate organic-inorganic hybrid materials with controllable structures and luminescence properties.

We demonstrate fast, highly efficient concurrent removal of toxic oxoanions of Se(VI) (SeO42–) and Se(IV) (SeO32–/HSeO3–) and heavy metal ions of Hg2+, Cu2+, and Cd2+ by the MoS42– intercalated Mg/Al layered double hydroxide (MgAl-MoS4-LDH, abbr. MoS4-LDH). Using the MoS4-LDH as a sorbent, we observe that the presence of Hg2+ ions greatly promotes the capture of SeO42–, while the three metal ions (Hg2+, Cu2+, Cd2+) enable a remarkable improvement in the removal of SeO32–/HSeO3–. For the pair Se(VI)+Hg2+, the MoS4-LDH exhibits outstanding removal rates (>99.9%) for both Hg2+ and Se(VI), compared to 81% removal for SeO42– alone. For individual SeO32– (without metal ions), 99.1% Se(IV) removal is achieved, while ≥99.9% removals are reached in the presence of Hg2+, Cu2+, and Cd2+. Simultaneously, the removal rates for these metal ions are also >99.9%, and nearly all concentrations of the elements can be reduced to

This work demonstrates tunable and purified luminescence via one-step delamination of HPTS/OS-LRH composites (HPTS is trisodium 8-hydroxy-pyrene-1,3,6-trisulphonate, OS is sodium salt of 1-octane sulfonic acid, LRH is layered rare-earth hydroxide, R=Tb, Y) along with energy transfer. The HPTSxOS1-x-LTbyY1-yH composites presented varied luminescence behavior depending on their physical state. In solid state, dual-color luminescence was observed: blue-dominant emissions (437nm) for HPTSxOS1-x-LTbH, and blue- (437nm) to green-dominant (516nm) luminescence for HPTS0.02OS0.98-LTbyY1-yH. In delaminated state in famamide, purified luminescence was present: pure blue emission (440nm) for HPTSxOS1-x-LTbH and HPTS0.02OS0.98-LTbyY1-yH (y≥0.5), while pure bluish-green emission (498nm) for HPTS0.02OS0.98-LTbyY1-yH (y≤0.3). Both the delamination of the composites and energy transfer from layer Tb3+ to HPTS contributed to the blue luminescence. The intriguing energy transfer process between photoactive inorganic hosts and organic guests can be utilized to fabricate hybrid materials with superior luminescence property.

We herein demonstrate the intercalation of several organic benzenepolycarboxylic compounds, terephthalic acid (TC), 1,3,5-benzenetricarboxylic acid (BTC) and 1,2,4,5-benzenetetracarboxylic acid (BTCC), into the layered terbium hydroxide (LTbH) and the sensitized luminescence of these organic species for the layer Tb 3+ . All of the as-prepared products demonstrated characteristic XRD diffractions attributed to layered materials. Compared with the NO 3 –LTbH precursor, efficient energy transfer from intercalated organic anions to Tb 3+ centers in LTbH layers took place, thus markedly enhancing the Tb 3+ luminescence. The relationship between the triplet energy levels of the organic guests and the energy level of Tb 3+ was analyzed to explain the sensitization effect and energy transfer from the gallery sensitizers to the layer Tb 3+ ions. The fluorescence lifetimes of NO 3 -LTbH, TC-LTbH, BTC-LTbH and BTCC-LTbH were determined to be 0.131, 0.315, 0.579 and 0.642 ms, respectively, indicating significantly increased lifetimes of the LTbH composites intercalated with the organic species.

We demonstrate the highly selective and exceptionally efficient capture of toxic oxoanions of As(III)/As(V) (HAsO32–/HAsO42–) and Cr(VI) (CrO42–) by the Mg/Al layered double hydroxide (Mg/Al-LDH) intercalated with MoS42– (MoS4-LDH). The MoS4-LDH exhibits very high removal rates (>99%) of As(III), As(V), and Cr(VI) from complex aqueous solutions. In the presence of many competing nontoxic anions such as SO42–, NO3–, and Cl–, remarkable selectivity for HAsO32–, HAsO42–, and CrO42– is observed. Highly concentrated As(III) and Cr(VI) can be rapidly reduced to 93% removals within 1 min and >96% removal within 5 min. Sorption kinetics for these oxoanions follow...

MOFs present potential application in electrocatalysis. The structure-activity of the Ni-MOFs with different morphologies, nanowires, neurons, and urchins is systemically investigated. The Ni-MOFs were controllably synthesized via the facile solvothermal method. Among them, the Ni-MOF nanowires are endowed with the highest electrocatalytic activity due to the unique structure, more exposed active sites, lower charge transfer resistance, and the fast and direct electron transfer in 1D structures. The typical morphology of the Ni-MOF nanowires is ca. 10 nm in diameter and several micrometers in length. When employed as an electrocatalyst in urea oxidation reaction, it exhibits a lower overpotential than and superior stability to the Ni-MOFs with other morphologies. Ni-MOF nanowires require a potential of ∼0.80 V (vs Ag/AgCl) to obtain 160 mA cm-2. In addition, after continuous electrocatalyzing for 3600 s at 0.40 V (vs Ag/AgCl), the current density retention of Ni-MOF nanowires could still reach more than 60% (>12 mA cm-2), which demonstrates Ni-MOF nanowires as promising electrocatalysts for urea oxidation.

We demonstrate a novel example of a delaminated MoS4/OS-LEuH composite (LEuH is layered europium hydroxide, OS is 1-octane sulfonate), which exhibits quenched luminescence in formamide and highly enhanced red emission in the water-present case. The turn-on luminescence sensing capability of the material is promising for feasible detection of a trace amount of water in formamide (FM) and N,N-dimethylformamide (DMF).

With a remarkably high theoretical energy storage capacity, a rechargeable lithium oxygen battery has attracted enormous attention. However, inert kinetics of oxygen evolution reaction and oxygen reduction reaction process generate low round-trip efficiency and poor cyclability. NiO materials are recognized as efficient and low-cost catalysts for Li–O2 battery. Here, we report a controllable approach to synthesize metal oxide decorated highly conductive Ti3C2 composite as cathode catalyst for rechargeable Li–O2 battery. In this composite, multi-layered Ti3C2 MXene enacts a superior host to load NiO nanoparticles on account of the open layered structure, the good electronic conductivity and the excellent chemical stability. Serving as Li–O2 battery cathode catalyst, NiO/Ti3C2 nanomaterials deliver a high initial capacity of 13350 mAh g−1 and good cycling performance of over 90 rounds at a current density of 100 mA g−1 and 500 mA g−1, respectively. Such properties of the prepared composite are attributed to the excellent conductivity of MXene and the high catalytic activity of NiO. As far as we know, this is the prior report that MXenes based materials are made into Li–O2 battery cathodes catalyst and proved to have a potential application in cathode materials of Li–O2 battery.

We demonstrate a novel example of tunable luminescence and the application of the delaminated FLN/OS-LRH composites (LRHs are layered rare-earth hydroxides, R = Tb, Y; FLN is the fluorescein named 2-(6-hydroxy-3-oxo-(3H)-xanthen-9-yl)benzoic acid; OS is the anionic surfactant 1-octane sulfonic acid sodium) in detecting Fe(III) ions. The FLNxOS1−x species (x = 0.02, 0.05, 0.10, and 0.20) are intercalated into the LTbyY1−yH layers (y = 1, 0.9, 0.7, 0.5, 0.3, 0.1 and 0) by ion exchange reactions to yield the composites FLNxOS1−x-LTbyY1−yH. In the solid state, the LYH composites display green emission (564 nm) arising from the organic FLN, while in LTbH composites, the luminescence of the Tb3+ in the layers (545 nm) and the FLN in the interlayers is co-quenched. In the delaminated state in formamide (FM), FLNxOS1−x-LTbH composites display green to yellowish-green luminescence (540–574 nm) following the increasing FLN/OS ratio; while the FLN0.02OS0.98-LTbyY1−yH composites show green emission at ∼540 nm. The fluorescence lifetimes of the composites (4.22–4.63 ns) are comparable to the free FLN-Na, and the quantum yields (31.62–78.70%) of the composites especially that (78.70%) of the FLN0.02OS0.98-LYH are much higher than that (28.40%) of free FLN-Na. The recognition ability of the FLN0.02OS0.98-LYH composite for metal cations is researched. The delaminated FLN0.02OS0.98-LYH colloidal suspension exhibits high selectivity for Fe3+ over other ions (Mg2+, Al3+, Ni2+, Co2+, Cu2+, Zn2+, Mn2+, Pb2+, and Cd2+) with fluorescence quenching, which can work as a kind of turn-off fluorescence sensor for the detection of Fe3+. The detection limit of Fe3+ is determined to be 2.58 × 10−8 M and the quenching constant (Ksv) is 1.70 × 103 M−1. This is the first work on LRH materials working as a chemosensor for recognising metal cations. It provides a new approach for the design of LRH materials to be applied in fluorescence chemosensing.

There is a need to develop highly selective and efficient materials for capturing uranium (normally as UO2(2+)) from nuclear waste and from seawater. We demonstrate the promising adsorption performance of S(x)-LDH composites (LDH is Mg/Al layered double hydroxide, [S(x)](2-) is polysulfide with x = 2, 4) for uranyl ions from a variety of aqueous solutions including seawater. We report high removal capacities (q(m) = 330 mg/g), large K(d)(U) values (10(4)-10(6) mL/g at 1-300 ppm U concentration), and high % removals (95% at 1-100 ppm, or ∼80% for ppb level seawater) for UO2(2+) species. The S(x)-LDHs are exceptionally efficient for selectively and rapidly capturing UO2(2+) both at high (ppm) and trace (ppb) quantities from the U-containing water including seawater. The maximum adsorption coeffcient value K(d)(U) of 3.4 × 10(6) mL/g (using a V/m ratio of 1000 mL/g) observed is among the highest reported for U adsorbents. In the presence of very high concentrations of competitive ions such as Ca(2+)/Na(+), S(x)-LDH exhibits superior selectivity for UO2(2+), over previously reported sorbents. Under low U concentrations, (S4)(2-) coordinates to UO2(2+) forming anionic complexes retaining in the LDH gallery. At high U concentrations, (S4)(2-) binds to UO2(2+) to generate neutral UO2S4 salts outside the gallery, with NO3(-) entering the interlayer to form NO3-LDH. In the presence of high Cl(-) concentration, Cl(-) preferentially replaces [S4](2-) and intercalates into LDH. Detailed comparison of U removal efficiency of S(x)-LDH with various known sorbents is reported. The excellent uranium adsorption ability along with the environmentally safe, low-cost constituents points to the high potential of S(x)-LDH materials for selective uranium capture.

Organic compounds of ortho-coumaric acid (abbr. o-CMA) and para-coumaric acid (abbr. p-CMA) are intercalated into the layered rare-earth hydroxides (LRHs, R = Eu, Gd) via the ion exchange method. The two organics having the same phenolic hydroxyl and carboxyl groups located at different positions demonstrate variant intercalation structures. The CMA anion guests within the LRH gallery indicate monolayered or bi-layered arrangements depending on their own characteristic features and deprotonation degrees. The combination of o-/p-CMA molecules with LEuH/LGdH layers generates hybrid materials exhibiting versatile luminescence properties. In the solid state, for LEuH layers, the luminescence of layer Eu3+ and interlayer o-CMA is co-quenched; however, for LGdH layers, green emissions (∼520 nm) are observed, both of which are different from the cyan emission (475 nm) of free o-CMA anions. When dispersed in formamide (FM), o-CMA–LEuH composites exhibit weak luminescence, in sharp contrast to o-CMA–LGdH composites displaying green emissions (495–520 nm) with markedly enhanced intensity. The p-CMA–LGdH composites display blue emission (457 nm) quite different from the green emission (499 nm) for free p-CMA in FM, compared with the unobservable emission within LEuH layers. In addition, co-intercalation of the surfactant OS (1-octane sulfonic acid sodium) with o-CMA anions into LEuH produces composites showing desirable blue emission or violet emission, due to the change of the microenvironment of organic guests. The energy transfer between layer Eu3+ and interlayer CMA was proposed to account for the co-quenching or blue shift. This work offers a beneficial approach to fabricate organic–inorganic photofunctional materials with a controllable structure and tunable fluorescence properties.

We demonstrate a novel example of delaminated layered rare-earth hydroxide (LRH, R = Tb, Y) composites with ortho-coumaric acid (CMA) and surfactant 1-octane sulfonic (OS) anions that exhibit tunable photoluminescence, especially blue emission due to energy transfer via the layer Tb3+. Different molar ratios of organic guests (OS/CMA) and layer ions (Tb/Y) give rise to versatile composites of OSxCMA1−x–LTbyY1−yH (x = 0.9, 0.8, 0.7, 0.6, 0.5, y = 1, 0.9, 0.7, 0.5, 0.3, 0.1, 0). In the solid state, for LTbH composites, co-quenching for emissions of CMA and the layer Tb3+ is found, while for LYH composites, green emission (502 nm) is observed. In formamide (FM), all of the composites are found to be facilely delaminated, and the colloidal suspensions of LTbH composites with varied OSxCMA1−x interlayer guests exhibit color-tuning within the blue-light region (430–465 nm), with blue-shift of emissions and enhanced luminescence intensity following increased OS content. LTbyY1−yH composites (with a fixed OS/CMA ratio of 0.7 : 0.3), however, present emissions from blue to green with increased Y3+ content. A new concept of ‘host-energy transfer-induced-emission (HETIE)’ is proposed to explain the blue luminescence via energy transfer of the host Tb3+. The intriguing energy transfer between a photoactive host matrix and interlayer guests in the delaminated state offers a promising approach to achieve efficient tuning of luminescence, thus meeting the high demand of applications on multicolor optical and display devices; especially blue emission.

We demonstrate the first example of exfoliated layered europium hydroxide (LEuH) composites with a fluorescent molecule that exhibit blue luminescence. Co-quenching in the solid state, blue emission (440 nm) in formamide, and green emission (514 nm) in water-formamide were found, for which delamination and swollen states account for the versatile luminescence behaviors.

The organic compound of coumarin-3-carboxylic acid (CCA), deprotonated beforehand by NaOH, and the 1-octane sulfonic acid anion (OS) were co-intercalated into the gallery of the layered europium hydroxide (LEuH) via an ion exchange method. Different molar ratios of CCA/OS and NaOH/CCA gave rise to the composites of CCA1−xOSx-LEuH (x = 0.8–1.0) showing different emission intensities. In formamide (FM), all composites were delaminated and the formed colloidal suspensions exhibited enhanced red luminescence of Eu3+ in comparison with the OS-LEuH without CCA. Also, the red emissions of the composites were different from the violet emission (421 nm) of free CCA− and blue emission (471 nm) of CCA2− anions in different deprotonation states. The energy levels of CCA and Eu3+ were analyzed to explain the sensitization effect for Eu3+ luminescence. The fluorescence lifetimes of CCA0.2OS0.8-LEuH-1 : 1, CCA0.02OS0.98-LEuH-1 : 1, CCA0.2OS0.8-LEuH-1 : 2, and CCA0.02OS0.98-LEuH-1 : 2 were determined to be 0.705, 0.704, 0.699 and 0.638 ms, respectively, indicating significantly longer lifetimes. The PL quantum yields of ∼10% demonstrate the excellent luminescence properties of the as-prepared CCA1−xOSx-LEuH composites. This is the first report on the sensitized luminescence properties of layer Eu3+ ions in LRH composites in the delaminated state. The intriguing red luminescence of delaminated LEuH composites offers a promising approach to achieve efficient luminescent film materials.

We demonstrate strong iodine (I2) vapor adsorption using Mg/Al layered double hydroxide (MgAl-LDH) nanocomposites intercalated with polysulfide (Sx2–) groups (Sx-LDH, x = 2, 4, 6). The as-prepared LDH/polysulfide hybrid materials display highly efficient iodine capture resulting from the reducing property of the intercalated polysulfides. During adsorption, the I2 molecules are reduced to I3– anions by the intercalated [Sx]2– groups that simultaneously are oxidized to form S8. In addition to the chemical adsorption, additional molecular I2 is physically captured by the LDH composites. As a result of these parallel processes, and despite their very low BET surface areas, the iodine capture capacities of S2-LDH, S4-LDH, and S6-LDH are ∼1.32, 1.52, and 1.43 g/g, respectively, with a maximum adsorption of 152% (wt %). Thermogravimetric and differential thermal analysis (TG-DTA), energy dispersive X-ray spectroscopy (EDS), and temperature-variable powder X-ray diffraction (XRD) measurements show the resulting ...

Two benzenepolycarboxylic organic sensitizers, 1,3,5-benzenetricarboxylic acid (BTA) and 1,2,4,5-benzenetetracarboxylic acid (BA), were intercalated into the gallery of NO 3 − type Eu 3+ -doped layered gadolinium hydroxide (NO 3 –LGdH:Eu). CHN analysis, FTIR, and SEM were employed to characterize the intercalation structures of the as-prepared organic/inorganic hybrids. The area per unit charge ( S charge ) was used to explain the intercalation structure and the arrangement of the interlayer guests. Different structures of the two organic compounds resulted in varied arrangement of guests. Photoluminescence studies indicated that both of the two organic compounds especially BA markedly enhanced the red luminescence of Eu 3+ due to efficient energy transfer between the organic guests and Eu 3+ centers.

Molybdenum disulfide (MoS2), as an extremely intriguing two-dimensional (2D) material with excellent electrocatalyst, has attracted more and more attentions in recent years. However, the lack of precisely engineered rich-edge S-vacancy MoS2 constitutes a major obstacle for in-depth studying of structure-activity relationship of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, based on Lewis acid-base theory, we prepared rich-edge S-vacancy MoS2 quantum dots (MoS2 QDs) via top-down strategy using lithium bis(trifluoromethylsulphonyl)imide as a stripper and clipper. It is demonstrated for the first time that the rich-edge S-vacancy MoS2 QDs exhibit an extraordinary ORR/OER catalytic performance in Li-O2 batteries system by a joint experimental and theoretical study. Importantly, the rich-edge S-vacancy MoS2 QDs can run more than 230 cycles at high current density, which was almost 9 times longer than the cycle stability of bulk MoS2. The excellent activity arises primarily due to that the MoS2 QDs facilitate conformal growth of amorphous Li2O2 film on the cathode, originating from the significant differences of adsorption energies between Li+ and O2, which could significantly enhanced Li2O2 formation/decomposition kinetics. This work provides a novel way for controllable synthesis of rich-edge S-vacancy MoS2 QDs, establishes the underlying mechanisms for the high OER/ORR activity, and suggests high translatability to apply other TMDs.

Organic anions of two benzenepolycarboxylic acids [1,3,5-benzenetricarboxylic acid (BTA) and 2,2′-biphenyldicarboxylic acid (BDA)], two pyridinecarboxylic acids [quinolinic acid (QA) and 2,5-pyridinedicarboxylic acid (PDA)], and two amino acids [phenylalanine (Phe) and tyrosine (Tyr)] were intercalated into the galleries of NO3–-type layered europium hydroxide (NO3–LEuH). All the prepared products displayed XRD patterns with series of diffractions due to layered materials. The composite structures and the arrangement of the guests in the galleries were investigated in detail. The structure of the organic guests (such as the number and position of carboxyl groups) affects the arrangement in the interlayer. SEM observations showed that the NO3–LEuH precursor and its intercalates crystallize in a columnar or layered stacking structure composed of hexagonal thin platelets. The luminescence study indicated that all samples display the typical red emission of Eu3+. Efficient energy transfer between intercalated BTA/BDA anions and Eu3+ centers takes place, markedly enhancing the Eu3+ luminescence, whereas QA–LEuH and PDA–LEuH with pyridinedicarboxylic acid anions show no obvious change in luminescence intensity. When amino acid anions such as Phe and Tyr were introduced into the interlayer, the Eu3+ emission was strongly quenched. The simple soft chemical method can open great opportunities for developing organic–inorganic multifunctional luminescent materials or biological probes for detecting certain amino acids.

A carboxyethyl substituted azacrown ether (CSAE) derivative was intercalated as a second host into a parent host of layered gadolinium hydroxides (LGdH) by an anion-exchange reaction. The influence of intercalation temperature and starting material ratios of CSAE/LRH on the structures and compositions of CSAE-LRH nanocomposites were investigated. Higher temperature and larger initial CSAE-LGdH weight ratios favor of higher degree of ion exchange at a certain range, while lower temperature gives good morphology for the composites. The adsorptive properties for transition and heavy metal ions were studied using the 20 °C-reacted composite, which showed higher adsorptivity toward transition and heavy metal ions, accompanied by the introduction of nitrate anions. The adsorptive capacity for transition metal ions was in the sequence of Cu(2+)Zn(2+)∼Ni(2+)∼Co(2+) with a high selectivity to Cu(2+). For the heavy metal ions Ag(+), Hg(2+), Pb(2+), and Cd(2+), the composite showed markedly high selectivity for Ag(+) and Hg(2+). When putting Cu(2+), Ag(+), Hg(2+), Pb(2+), and Cd(2+) together, Ag(+) and Hg(2+) still have higher adsorptive selectivity over Pb(2+) and Cd(2+), and Cu(2+) has also relatively high selectivity but not as high as Ag(+) and Hg(2+). The nanocomposites with a second host in the interlayer are one promising kind of material because of the synergy of the steric effect of the parent host (LRH layer) and the particular characteristics of the secondary host (interlayer crown ether anions).

Cobalt is a promising soft metallic magnetic material used for important applications in the field of absorbing stealth technology, especially for absorbing centimeter waves. However, it frequently presents a weak dielectric property because of its instability, aggregation, and crystallographic form. A method for enhancing the electromagnetic property of metal Co via phase-controlled synthesis of Co nanostructures grown on graphene (GN) networks has been developed. Hexagonal close-packed cobalt (α-Co) nanocrystals and face-centered cubic cobalt (β-Co) nanospheres with uniform size and high dispersion have been successfully assembled on GN nanosheets via a facile one-step solution-phase strategy under different reaction conditions in which the exfoliated graphite oxide (graphene oxide, GO) nanosheets were reduced along with the formation of Co nanocrystals. The as-synthesized Co/GN nanocomposites showed excellent microwave absorbability in comparison with the corresponding Co nanocrystals or GN, especially for the nanocomposites of GN and α-Co nanocrystals (the reflection loss is -47.5 dB at 11.9 GHz), which was probably because of the special electrical properties of the cross-linked GN nanosheets and the perfect electromagnetic match in their microstructure as well as the small particle size of Co nanocrystals. The approach is convenient and effective. Some magnetic metal or alloy materials can also be prepared via this route because of its versatility.

We report, for the first time, structural transformation and photoluminescence behavior by calcination of layered europium-doped yttrium hydroxide (LYH:Eu) intercalate with organic sensitizer terephthalate (TA). The calcined samples displayed tunable luminescent performance dependent on calcined temperatures. Calcination under low temperatures (200 and 300 °C) retained layered structure, while high temperatures (>400 °C) yielded oxide phase. The optimal fluorescence occurred in 200 °C-calcination, possibly resulting from an optimal arrangement of TA. Above 200 °C, the luminescence intensity was first weakened and then enhanced, due to gradual departure of TA and following occurrence of oxide phase. The energy transfer presented an intrinsic transition from TA-to-Eu 3+ in the organic intercalate to O 2− -to-Eu 3+ charge transfer in as-transformed oxide. The predominant luminescence property of the hybrid material can provide valuable guide for developing tunable luminescent materials, especially flexible materials resulting from the containing organic component.

Co-assembly of inorganic LDH nanosheets with an organic azacrown ether carboxylic acid derivative was studied by a flocculation method. The homogeneous structure seen in the wet state changed markedly after drying: a staging structure transformed into a homogeneous one after increased assembly times. The experimental observations, changeover from homogeneous to staging and unequal charges of organic and inorganic guests in gallery, might suggest the Daumas–Herold model applicable in LDH system. The composites with staging could function as powerful water adsorption materials with facile reversibility.

The organic sensitizer terephthalic acid and its anion terephthalate (TA) were introduced into the galleries of europium-doped layered yttrium hydroxide (LYH:Eu). In contrast to using water as solvent, the use of formamide resulted in the introduction of more organic guests and markedly enhanced the Eu3+ luminescence. Formamide prevented water from entering the system, leading to an excess of terephthalic acid molecules, and more efficient coordination of the TA guest with the Eu3+ in the layers of the composite, all of which may have contributed to the enhanced Eu3+ luminescence.

A simple, highly efficient, and eco-friendly method is prepared to divide bulk boron nitride (BN) into boron nitride nanosheets (BNNSs). Due to the anisotropy of the hexagonal BN expansion coefficient, bulk BN is exfoliated utilizing the rapid and tremendous change in temperature, the extreme gasification of water, and ice thermal expansion pressure under freeze drying. The thickness of most of the BNNSs was less than ∼3 nm with a yield of 12-16 wt%. The as-obtained BNNS/polyacrylamide (PAAm) composite hydrogels exhibited outstanding mechanical properties. The tensile strength is fives times the bulk of the BN/PAAm composite hydrogels and the elongations are more than nine-fold the bulk of the BN/PAAm composite hydrogels. The BNNS/PAAm nanocomposite hydrogels also exhibited excellent elastic recovery, and the hysteresis of the BNNS nanocomposite hydrogels was negligible even after 30 cycles with a maximum tensile strain (e max) of 700%. This work provides new insight into the fabrication of BN/polymer nanocomposites utilizing the excellent mechanical properties and transparency of BN. The results confirm that a few layers of BNNSs can also efficiently and directly improve the mechanical properties of composite polymer due to its stronger surface free energy and better wettability.

Novel hierarchical cobalt phosphate (alpha- and beta-Co2P2O7) and cobalt hydrogen phosphate hydroxide [Co-11(HPO3)(8)(OH)(6)] three-dimensional (3D) architectures with different morphologies were synthesized under a solvothemal condition. The form and shape of cobalt phosphate can be readily tuned by adjusting experimental parameters of the reaction system. The novel hierarchical alpha-CO2P2O7 microcrystals with basketry-like microstructures were obtained with a molar ratio of Co2+/H3PO4/CH3NH2/HO(CH2)(2)0OH of 1:1.2:1:108, the reaction temperature of 180 degrees C, and the reaction time of 5 days; dumbbell-like beta-Co2P2O7 microspheres were formed with the same reaction temperature and time but the molar ratio of 1: 1.2:1:54, and Co-11(HPO3)(8)(OH)(6) with peony-like nanostructures was prepared with the same molar ratio and reaction time as beta-Co2P2O7 but the reaction temperature of 120 degrees C. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectra (FT-IR) technologies, a Quantum Design superconducting quantum interference device (SQUID) magnetometer, and a network analyzer. The formation mechanism of cobalt phosphate microstructures was investigated in detail.

Fe4[Fe(CN)6]3 nanoparticles were prepared with potassium ferrocyanide as the single precursor. The effects of precursor concentration and temperature on the particles were investigated. The reaction mechanism was explained. Calculation showed that formation of Fe4[Fe(CN)6]3 precipitates and volatile HCN greatly reduce the electron potential of Fe3+/Fe2+ and increase the reaction extent of the oxidation of ferrous ions.

We report the synthesis of Fe{sub 3}N nanodendrites directly by reduction-nitriding of {alpha}-Fe{sub 2}O{sub 3} nanopine dendrites in a mixed stream of H{sub 2}-NH{sub 3}. Fe{sub 3}N basically retains dendritic morphology of the starting material {alpha}-Fe{sub 2}O{sub 3.} It is found that nanorod branches of Fe{sub 3}N dendrites have relatively uniform diameters and are evenly distributed at both sides of the stem with a periodicity of about 50nm. The diameters of the nanorods are about 50nm, and their lengths range from 50 to 1000nm. Fe{sub 3}N nanodendrites show a rapid saturation of magnetization of 104emu/g at 300K, as expected for a magnet.

Large over-potentials during battery operation remain a big obstacle for aprotic Li–O2 batteries. Herein, a nanocomposite of about 4 nm cobalt monoxide nanocrystals grown in situ on reduced graphene oxide substrates (CoO/RGO) has been synthesized via a thermal decomposition method. The CoO/RGO cathode delivers a high initial capacity of 14 450 mAh g−1 at a current density of 200 mA g−1. Simultaneously it displays little capacity fading after 32 cycles with a capacity restriction of 1000 mAh g−1. Additionally, compared with Ketjenblack and general CoO nanoparticles, ultrathin CoO nanoparticle-decorated RGO electrode materials with a delaminated structure display an observable reduction of over-potential in Li–O2 batteries. These results demonstrate that the introduction of RGO improves the performance of CoO, which is a promising strategy for optimizing the design of electrocatalysts for aprotic rechargeable Li–O2 batteries.

Fast intercalation of macrocyclic tetraazacrown ether carboxylic acid derivative (TECA) into the interlayer of Mg/Al-layered double hydroxide (Mg/Al-LDH) via a “one-step” reaction in formamide was carried out. Compared with swelling/restoration and ion-exchange reactions, this method can markedly decrease the reaction time (even shorter than 10 min), thus give high yield of the products and well-retain the hexagonal morphology of the starting LDH. The investigation of the reaction process demonstrated that the preceding combination of TECA and formamide accelerated the swelling of LDH, and the quasi-homogeneous colloidal system promoted the facile incorporation of TECA with the LDH sheets to cause their quick restoration. The obtained staging structure may originate from the flexibility of crown ether guest and LDH host layer, and the structural transformation from homogeneous to second-staging suggests the Daumas–Herold model rarely observed in LDH system. The simple and fast one-step method can conveniently fabricate new multifunctional hybrid materials with combined advantages of the organic/inorganic intercalates plus those of LDH host.