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Replacing the thermodynamically unfavorable oxygen evolution reaction (OER) with the low theoretical potential (−0.33 V) and safe by-product (N2/H2O) hydrazine oxidation reaction (HzOR) is an energy-saving way for hydrogen production. Nevertheless, the complexity of bifunctionality increases the difficulty of catalyst design. In this work, a hybrid of NiC2O4 and Nb2O5 is synthesized on nickel foam via a two-step low temperature reaction using Ni3S2 as a sacrificial template, named SNiC2O4–Nb2O5/NF. The experimental and theoretical calculation results illustrate that electrons are transferred from Ni to Nb, thus regulating the electronic structure of Ni. In the hybrid, Nb2O5 can effectively adsorb and split H2O, as well as downshift the d-band center of SNiC2O4, thereby optimizing the Volmer step. SNiC2O4–Nb2O5/NF achieves the properties for the hydrogen evolution reaction (HER: η20 = 155 mV) and the oxygen evolution reaction (OER: η20 = 293 mV). The addition of hydrazine to an alkaline electrolyte can decrease the cell voltage by 1.41 V when the current density is 20 mA cm−2, and achieve a high-speed hydrogen yield driven by an AA battery. This work puts forward an idea for the rational design of environmentally friendly and effective hybrid catalysts. [ABSTRACT FROM AUTHOR]

Magnetism of any material depends on its crystal structure. However, two isostructural compounds such as MCuMoO4(OH) (M = Na, K) can have markedly different magnetic properties. Herein, we introduce a new method to describe the linkages between the O-atoms and their bridged Cu2+ ions in order to clearly illustrate the structure–magnetic property relationships. This new method can account for magnetic differences between the two isostructural MCuMoO4(OH) and is further confirmed by the rational design and development of a new compound KGaCu(PO4)2 with different linkages. The title compound crystalized in a space group of P21/c adopts a one-dimensional (1D) magnetically isolated S = 1/2 zigzag chain composed of elongated [CuO6] octahedra via sharing alternately equatorial and skew edges. O atoms at the skew edges bridge the equatorial and axial orbitals of neighbouring Cu2+ ions (denoted EOA), while those at the equatorial edges bridge the equatorial orbitals of Cu2+ ions (EOE). The nearest-neighbour (NN) magnetic coupling of Cu2+ ions with the EOA linkage at 2.821 Å in the title compound is negligible, whereas the NN magnetic coupling of Cu2+ ions with the EOE linkage at 2.974 Å is essential. Therefore, the zigzag chain containing alternating spin-exchange dimers and no-spin-exchange ones is similar in electronic configuration to the dimerization of the quasi-one-dimensional antiferromagnet. Magnetic investigation of analogous compounds with a 'trans–cis–trans–cis' configuration observed in the title compound may shed light on structural evolutions associated with spin-Peierls (SP) transition. [ABSTRACT FROM AUTHOR]

Magnetism of any material depends on its crystal structure. However, two isostructural compounds such as MCuMoO4(OH) (M = Na, K) can have markedly different magnetic properties. Herein, we introduce a new method to describe the linkages between the O-atoms and their bridged Cu2+ ions in order to clearly illustrate the structure–magnetic property relationships. This new method can account for magnetic differences between the two isostructural MCuMoO4(OH) and is further confirmed by the rational design and development of a new compound KGaCu(PO4)2 with different linkages. The title compound crystalized in a space group of P21/c adopts a one-dimensional (1D) magnetically isolated S = 1/2 zigzag chain composed of elongated [CuO6] octahedra via sharing alternately equatorial and skew edges. O atoms at the skew edges bridge the equatorial and axial orbitals of neighbouring Cu2+ ions (denoted EOA), while those at the equatorial edges bridge the equatorial orbitals of Cu2+ ions (EOE). The nearest-neighbour (NN) magnetic coupling of Cu2+ ions with the EOA linkage at 2.821 Å in the title compound is negligible, whereas the NN magnetic coupling of Cu2+ ions with the EOE linkage at 2.974 Å is essential. Therefore, the zigzag chain containing alternating spin-exchange dimers and no-spin-exchange ones is similar in electronic configuration to the dimerization of the quasi-one-dimensional antiferromagnet. Magnetic investigation of analogous compounds with a 'trans–cis–trans–cis' configuration observed in the title compound may shed light on structural evolutions associated with spin-Peierls (SP) transition. [ABSTRACT FROM AUTHOR]

The requirement of hydrogen adsorption Gibbs free energy (ΔGH*) approximating to 0 eV limits the hydrogen evolution reaction (HER) activity of most electrocatalysts in alkaline media. The construction of interface and defects engineering is an effective strategy to obtain the optimal ΔGH*. Ni3N exhibits poor HER activity due to its undesirable ΔGH*. By cooperating with Nb2O5, the d-band center of Ni3N was reduced, improving its catalytic performance. The optimized Nb2O5–Ni3N displays an overpotential of 80 mV at 10 mA cm−2 and superior activity than the benchmark Pt/C catalyst when the current density is greater than 125 mA cm−2. Experimental and density functional theory results demonstrate that the improved catalytic activity is because the electronic interaction between Ni and Nb changes the coordination numbers of these two atoms, resulting in oxygen vacancies at the interface. Under the synergistic effect of Nb2O5 and Ni3N, the catalyst exhibits optimal ΔGH* and water adsorption energy. [ABSTRACT FROM AUTHOR]

Lanthanide metal–organic frameworks (Ln-MOFs) have demonstrated great potential in luminescence sensing and optical anti-counterfeiting. High-security anti-counterfeiting technology is of great importance and requires the development of universal luminescent materials with multiple modes of emission and adjustable photoluminescence. Herein, a 3D red light emission microporous europium(III) metal–organic framework [Eu3(OH)(1,3-db)2(H2O)4]·3H2O (1) (1,3-db = 1,3-di(3′,5′-dicarboxylpheny) benzene) was constructed from a zigzag [Eu3(COO)8] chain and π-electron-rich terphenyl-tetracarboxylate. Notably, the quenched fluorescence of 1 under hydrogen chloride vapor could be recovered upon fuming by a vapor of Et3N. Most strikingly, the strong blue light emission by nitrogen and sulfur co-doped carbon dots (N,S-CDs) could be encapsulated in 1 to generate a dual-emission composite, namely, N,S-CDs@Eu-MOF, which shows solvent-dependent photoluminescence: N,S-CD-related blue luminescence in water and Eu-MOF-related red emission in organic solvents. Taking advantage of the above unique reversible fluorescent behavior, Eu-MOF and N,S-CDs@Eu-MOF are prepared as fluorescent high-security inks to achieve data encryption and decryption on specific flower patterns. [ABSTRACT FROM AUTHOR]

Herein, we have synthesized successfully a three-dimensional/two dimensional (3D/2D) core–shell Cu2O@Fe–Ni3S2 nanoflower on copper foam at room temperature. Remarkably, by virtue of rich active sites and vacancies, large surface area, high conductivity and close contact with the electrolyte, the Cu2O@Fe–Ni3S2 catalyst exhibits superior stability and oxygen evolution reaction performance. [ABSTRACT FROM AUTHOR]

Sensitive detection of disease-related DNA is of great significance for early and accurate diagnosis and therapy. To achieve this aim, we constructed a dual-cycling amplification biosensor for target oligonucleotide detection. Based on the toehold-mediated strand displacement reaction (TSDR), target DNA competitively hybridized with the assistant DNA which previously formed a duplex complex with the trigger DNA, and the trigger DNA was released. Exonuclease III (Exo III) would specially hydrolyze the assistant DNA in the new duplex DNA to free the target DNA for a new cycle. Similarly, based on the TSDR and Exo III assisted amplification, the released trigger DNA would repeatedly open the G-quadruplex hairpins and promote the generation of numerous G-quadruplex sequences. Then, the fluorescence intensity of Thioflavin T (ThT) would present apparent enhancement due to the formation of the G-quadruplex/ThT complex. The commercially available ThT is economical and of low toxicity. More importantly, owing to its satisfactory water solubility, ThT effectively avoids the introduction of organic solvents. There was no need for expensive modification through the whole process. The proposed method displayed high distinction efficiency towards target DNA against mismatched DNA. Additionally, the linear range of this strategy was 0.2–10 nM, and the detection limit was 0.04 nM. Besides, this sensor can be applied in human serum with satisfactory results. [ABSTRACT FROM AUTHOR]