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Trace detection of bioactive small molecules (BSMs) in body fluids is of great importance for disease diagnosis, drug discovery, and health monitoring. Based on the chiral ligand of 4,4'-(1,2-dihydroxyethane-1,2-diyl)dibenzoic acid (H 2 L), an achiral 3D porous Ni(II)-MOF, with a trinuclear cluster based (3,9)-c {4 2 ·6} 3 {4 6 ·6 21 ·8 9 }-xmz net, was constructed under solvothermal conditions. Benefiting from its robust framework and excellent luminescent performance, NiMOF was endowed with remarkable capabilities in efficiently, rapidly, and sensitively detecting the 3-nitrotyrosine (3-NT) biomarker and 6-propyl-2-thiouracil (6-PTU) thyroid drug based on the spectral overlap and photo-induced electron transfer (PET) caused luminescence quenching response. Notably, NiMOF exhibited exceptional performance in quantifying 3-NT and 6-PTU in urine samples, yielding highly satisfactory results. Additionally, an intelligent detection system was crafted to enhance the reliability and practicability of 3-NT/6-PTU detection in urine, based on tandem combinational logic gates. This work not only heralds a promising trajectory in the development of MOF-based luminescent sensors, but also paves the way for the intelligent monitoring of BSMs in real bodily fluids.

A new biomimetic model complex of the active site of acireductone dioxygenase (ARD) was synthesized and crystallographically characterized ( [Ni( ii )( N -(ethyl- N 'Me 2 )(Py)(2- t -ButPhOH))(OTf)]- 1). 1 displays carbon-carbon oxidative cleavage activity in the presence of O 2 towards the substrate 2-hydroxyacetophenone. This reactivity was monitored via UV-Visible and NMR spectroscopy. We postulate that the reactivity of 1 with O 2 leads to the formation of a putative Ni(III)-superoxo transient species resulting from the direct activation of O 2 via the nickel center during the oxidative reaction. This proposed intermediate and reaction mechanism were studied in detail using DFT calculations. 1 and its substrate bound derivatives display reactivity toward mild outer sphere oxidants, suggesting ease of access to high valent Ni coordination complexes, consistent with our calculations. If confirmed, the direct activation of O 2 at a nickel center could have implications for the mechanism of action of ARD and other nickel-based dioxygenases and their respective non-traditional, enzymatic moonlighting functions, as well as contribute to a general understanding of direct oxidation of nickel(II) coordination complexes by O 2 .

Magnetic-fluorescent microbeads have been widely used in the multiplex detection of biological molecules. The traditional method relies on flow cytometry to decode and analyze the microbeads. Alternative strategies that employ immobilized microbeads on a plane and involve fluorescence imaging to analyze the microbeads have been proposed. Among these strategies, an integrated chip that controls magnetic field contribution using nickel powder pillars and captured microbeads has attracted great attention. Despite its unique advantages such as low manufacturing costs, reusability and high capture efficiency, existing research had been limited by the inability to precisely capture a single microbead, and the overlapping of microbeads has made multiplex immunoassays based on this strategy impossible. In this work, low-density microbeads were prepared in a microfluidic chip using IBOMA as the main monomer. The low density of the microbeads made the preparation of an aqueous suspension easier. An integration of nickel patterns, magnets and channels was carried out and demonstrated the capacity of capturing single microbeads precisely. Fluorescence coding further empowered this method with the ability of multiplex immunoassay, which was verified using three types of IgG, and a calibration curve for the detection of anti-human IgG was established using a sandwich immunoassay. These results show the promising potential of this strategy for biomedical detection.

The detrimental effects of widespread pesticide application on the health of living organisms highlight the urgent need for technological advancements in monitoring pesticide residues at trace levels. This study involves the synthesis of a distinctive sensing material, KL@Ni@g-C 3 N 4 , which comprises nanocomposites of graphitic carbon nitride with Kraft lignin and nickel. The prepared samples were characterized using FT-IR, PXRD, TEM, SEM, and EDX techniques. The KL@Ni@g-C 3 N 4 nanocomposite was drop-cast on a graphite electrode. Subsequently, this fabricated electrode was used to detect cypermethrin (CYP) residues in drinking water. The redox properties of the fabricated sensors were evaluated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The limit of detection (LOD) of the fabricated sensor was determined to be 0.026 μg mL -1 , which is below the maximum residual limits of CYP in the environment (0.5 μg mL -1 ) and within the acceptable range for food products (∼0.05 to 0.2 μg mL -1 ). Therefore, this study proposes a promising alternative to conventional methods for detecting pesticides in drinking water.

The exploration of noble metal-free nanoarrays as high-activity catalytic electrodes for glucose biosensing holds great significance. Herein, we propose a Ni nanoparticle-decorated TiO 2 nanoribbon array on a titanium plate (Ni@TiO 2 /TP) as an effective non-enzymatic glucose biosensing electrode. The as-prepared Ni@TiO 2 /TP electrode demonstrates rapid glucose response, a wide linear response range (1 μM to 1 mM), a low detection limit (0.08 μM, S/N = 3), and high sensitivity (10 060 and 3940 μA mM -1 cm -2 ), with good mechanical flexibility and stability. Moreover, it proves efficient in glucose biosensing in real human blood serum and cell culture fluid. Thus, it is highly promising for practical applications.

In recent years, great progress has been made on the study of nanozymes with enzyme-like properties. Here, bimetallic Fe and Ni nanoclusters were anchored on the nanosheets of nitrogen-rich layered graphitic carbon nitride by one-step pyrolysis at high temperature (Fe/Ni-CN). The loading content of Fe and Ni on Fe/Ni-CN is as high as 8.0%, and Fe/Ni-CN has a high specific surface area of 121.86 m 2 g -1 . The Fe/Ni-CN can effectively oxidize 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , and exhibits efficient peroxidase-like activity, leading to a 17.2-fold increase compared to pure graphitic carbon nitride (CN). Similar to the natural horseradish peroxidase (HRP), the Fe/Ni-CN nanozyme follows catalytic kinetics. The Michaelis-Menten constant ( K m ) value of the Fe/Ni-CN nanozyme for TMB is about 8.3-fold lower than that for HRP, which means that the Fe/Ni-CN nanozyme has better affinity for TMB. In addition, the catalytic mechanism was investigated by combination of free radical quenching experiments and density-functional theory (DFT) calculations. The results show that the high peroxidase-like activity is due to the easy adsorption of H 2 O 2 after bimetal loading, which is conducive to the production of hydroxyl radicals. Based on the extraordinary peroxidase-like activity, the colorimetric detection of p -phenylenediamine (PPD) was constructed with a wide linear range of 0.2-30 μM and a low detection limit of 0.02 μM. The sensor system has been successfully applied to the detection of residual PPD in real dyed hair samples. The results show that the colorimetric method is sensitive, highly selective and accurate. This study provides a new idea for the efficient enhancement of nanozyme activity and effective detection of PPD by a bimetallic synergistic strategy.

A new type of hybrid material (NCMTs@MoO 2 /FeNi 3 ) with a multi-layer heterostructure was designed and fabricated via a one-step pyrolysis process using FeOOH/NiMoO 4 @PDA as the precursor. FeOOH/NiMoO 4 @PDA was prepared by the solvothermal method, followed by the nickel-ion etching method coupled with the polymerization of dopamine (DA). The as-obtained material was made of nitrogen-doped carbon nanotubes embedded with FeNi 3 and MoO 2 nanoparticles (NPs). Notably, the FeNi 3 NPs exhibited significantly improved performance in the reduction of 4-nitrophenol (4-NP) and adsorption of histidine-rich protein as well as provided appropriate magnetism resources. The MoO 2 NPs imparted a metallic nature with excellent conductivity, and the N-doped mesoporous carbon microtubes also improved conductivity and facilitated mass transfer, thus leading to enhanced performance in catalysis. Benefiting from the 1D hierarchical porous structure and compositional features, the NCMTs@MoO 2 /FeNi 3 composites exhibited excellent performance in 4-NP reduction and protein adsorption via specific metal affinity between the polyhistidine groups of proteins and the FeNi 3 NPs. The result presented here indicates that the strategy of combining tailored components, heterostructuring, and carbon integration is a promising way to obtain high-performance composites for other energy-related applications.

The synthesis of eleven new nickel Schiff base complexes each bearing four pendant groups is reported. The structures of the complexes differ in the identity of the pendant groups and/or diamine moiety. All complexes were characterised by microanalysis, Nuclear Magnetic Resonance (NMR) spectroscopy and Electrospray Ionisation Mass Spectrometry (ESI-MS), while the solid-state structures of two of the molecules were also determined using X-ray crystallographic methods. The DNA binding properties of the nickel complexes with double stranded DNA and a range of G-quadruplex DNA structures was explored using different spectroscopic methods as well as computational techniques. Results from ESI-MS experiments and Fluorescent Indicator Displacement (FID) assays were consistent with each other and indicated that varying the diamine moiety had less influence on DNA affinity than changing the pendant groups. These conclusions were also generally supported by results obtained from UV melting experiments and Fluorescence Resonance Energy Transfer (FRET) assays. The cytotoxicity of selected examples of the new complexes, and close analogues reported recently, towards V79 Chinese hamster lung cancer cells and THP-1 human leukemia cells was measured. All were found to display modest cytotoxicity, with flow cytometry experiments suggesting an apoptotic pathway was the most likely mechanism of cell death.

In mitochondria, the detoxification of molar excess H 2 S as polysulfide proceeded via an oxidation process promoted by Cu/Zn containing superoxide dismutase (SOD1) enzyme, which has been very recently reported as the alternative enzyme for cytosolic H 2 S oxidation. Herein, we present Ni(II) complexes bearing the terminal SH group as a synthetic functional analogue for the sulfide oxidase function of SOD1. Synthesis, crystal structure and complete spectroscopic characterization of two sets of complexes, [NiL OMe/ t Bu (PPh 3 )] (2OMe/tBu) and tetraethyl salt of [NiL OMe/ t Bu (SH)] -1 (3OMe/tBu), were described (LOMe = ( E )-2-methoxy-6-(((2-sulfidophenyl)imino)methyl)phenolate and LtBu = ( E )-2,4-di- tert -butyl-6-(((2-sulfidophenyl)imino)methyl)phenolate). Under anaerobic conditions, 3OMe/tBu responded to a catalytic sulfur atom transfer (SAT) reaction with PPh 3 to produce SPPh 3 . The SAT reaction was analyzed using detailed studies of 1 H and 31 P NMR spectra. Finally, the SAT reactivity pattern was compared with the same in the native enzyme of SOD1.

Phosphatidic acid and phosphatidylserine are anionic phospholipids with emerging signalling roles in cells. Determination of how phosphatidic acid and phosphatidylserine change location and quantity in cells over time requires selective fluorescent sensors that can distinguish these two anionic phospholipids. However, the design of such synthetic sensors that can selectively bind and respond to a single phospholipid within the complex membrane milieu remains challenging. In this work, we present a simple and robust strategy to control the selectivity of synthetic sensors for phosphatidic acid and phosphatidylserine. By changing the coordination metal of a dipicolylamine (DPA) ligand from Zn(II) to Ni(II) on the same synthetic sensor with a peptide backbone, we achieve a complete switch in selectivity from phosphatidic acid to phosphatidylserine in model lipid membranes. Furthermore, this strategy was largely unaffected by the choice and the position of the fluorophores. We envision that this strategy will provide a platform for the rational design of targeted synthetic phospholipid sensors to probe plasma and intracellular membranes.

Mycophenolate mofetil (MpM) is a medication used to prevent the rejection of transplanted organs, particularly in kidney, heart, and liver transplant surgeries. It is extremely important to be conscious that MpM can raise the risk of severe infections and some cancers if it exceeds the recommended dose while lower doses will result in organ rejections. So, it is essential to monitor the dosage of MpM in real time in the micromolar range. In this work, we have synthesized 3-aminopropyltriethoxysilane (APTES) functionalized nickel cobaltite (NiCo 2 O 4 ) and this amino functionalization was chosen to enhance the stability and electrochemical activity of NiCo 2 O 4 . The enhanced activity of NiCo 2 O 4 was used for developing an electrochemical sensor for the detection of MpM. APTES functionalized NiCo 2 O 4 was coated on carbon cloth and used as the working electrode. Surface functionalization with APTES on NiCo 2 O 4 was aimed at augmenting the adsorption/interaction of MpM due to its binding properties. The developed sensor showed a very low detection limit of 1.23 nM with linear ranges of 10-100 nM and 1-100 μM and its practical applicability was examined using artificial samples of blood serum and cerebrospinal fluid, validating its potential application in real-life scenarios.

High cost, inherent destabilization, and intricate fixing of enzyme molecules are the main drawbacks of enzyme-based creatinine sensors. The design of a low-cost, stabilizable, and enzyme-free creatinine sensing probe is essential to address these limitations. In this work, an integrated three-dimensional (3D) free-standing electrode was designed to serve as a non-enzymatic creatinine sensing platform and was fabricated by rapid electrodeposition of a dense copper nanoparticle film on nickel foam (Cu NP film/NF). This low-cost, stable, easy-to-fabricate, and binder-free Cu NP film/NF electrode has abundant active sites and excellent electrochemical performance. Cyclic voltammetry measurements show a wide linear range (0.25-24 mM), low detection limit (0.17 mM), and high sensitivity (306 μA mM -1 cm -2 ). The developed sensor shows high recovery of creatinine concentration in real urine. Besides, it has better specificity, reproducibility, and robustness in detecting creatinine. These excellent results suggest that a non-enzymatic creatinine sensor based on an integrated 3D free-standing Cu NP film/NF electrode has good potential for non-invasive detection of urinary creatinine.

Superoxide dismutase (SOD) enzymes are pivotal in regulating oxidative stress. In order to model Ni containing SOD enzymes, the results of the thermodynamic, spectroscopic and SOD activity studies on the complexes formed between nickel(II) and a NiSOD related peptide, CysCysAspLeuProCysGlyValTyr-NH 2 ( wtCC ), are reported. Cysteine was introduced to replace the first histidine residue in the amino acid sequence of the active site of the NiSOD enzyme. The novel peptide exhibits 3 times higher metal binding affinity compared to the native NiSOD fragment. This is due to the presence of the first cysteine in the coordination sphere of nickel(II). At physiological pH, the (NH 2 ,S - ,S - ,S - ) coordinated complex is the major species. This coordination mode is altered when one thiolate group is replaced by an amide nitrogen of the peptide backbone above pH 7.5. The nickel complexes of wtCC exhibit similar SOD activity to that of the complex formed with the active site fragment of the native NiSOD. The reaction between the complexes and the superoxide anion was studied by the sequential stopped-flow method. These studies revealed that the nickel(II) complex is always in excess over the nickel(III) complex during the dismutation process. However, the nickel(III) species is also involved in a relatively fast degradation process. This unambiguously proves that a protective mechanism must be operative in the NiSOD enzyme which prevents the oxidation of the sulfur atom of cysteine in the presence of O 2 - . The results provide new possibilities for the use of NiSOD mimics in bio- and industrial catalytic processes.

In this study, we have shown how to prepare a ternary nanocomposite (Ag 2 S-NiMoO 4 -g-C 3 N 4 ) consisting of graphitic carbon nitride (g-C 3 N 4 ) nanosheets, silver sulfide (Ag 2 S) nanocrystals, and nickel molybdate (NiMoO 4 ) nanorods and its sensing ability to detect quercetin, a flavonoid found in many fruits and vegetables. An Ag 2 S-NiMoO 4 -g-C 3 N 4 nanocomposite-modified screen-printed electrode (SPE) exhibited remarkable sensing performance in a quercetin (Que) concentration range of 0.005 μM-20 μM with a low detection limit of 2.7 nM. Moreover, we have aimed at improving the selectivity and sensitivity of a sensor for detecting Que by optimizing the composition of Ag 2 S-NiMoO 4 -g-C 3 N 4 , the film thickness, and the electrolyte pH. The sensor's selectivity for Que was tested in the presence of potential interferents such as ascorbic acid, citric acid, fructose, glucose, lactose, maltose, mannose, sucrose, and tyrosine. The performance of the sensor was tested on a variety of food samples, including green apple, green tea, honey, and red onion skin.

Herein, we describe a protocol for the direct and selective acylation and alkynylation of the C(sp 3 )-H bonds of saturated hydrocarbons by synergistic decatungstate photo-HAT and nickel catalysis. This method, using cheap and easy-to-synthesize TBADT as a HAT photocatalyst, exhibits excellent site selectivity. A wide variety of high-value ketones, amides, esters, and diverse alkynes can be efficiently constructed from abundant hydrocarbon feedstocks.

The synthesis of nickel selenide nanostructures under ambient conditions remains fascinating, aesthetically beautiful, and energy efficient, as most reported methods involve high-temperature techniques. In this work, we have reported the wet chemical synthesis of NiSe 2 nanostructures at room temperature. The approach starts with nickel nanowires (NiNW) and selenous acid as active ingredients. Upon the incubation of NiNW in selenous acid, zero-valent metallic nickel gradually oxidised with the successive deposition of nano-selenium, a reductive product, over the pristine NiNW surface. This thermodynamically controlled galvanic replacement reaction (GRR) is favourably governed by the reduction potential values of the Ni 2+ /Ni and SeO 3 2- /Se redox couples. Moreover, the selenium nanoparticles over the NiNW surface and the oxidized Ni 2+ underneath then interplay during inward and outward diffusion. The different diffusivities of the elements/ions cause the generation of void interiors, thus resulting in tubular nanostructures. Therefore, both the GRR and nanoscale Kirkendall effect jointly remain engaged, resulting in the formation of hollow NiSe 2 nanotubular structures. Then, we ably exploit this heterogeneous chalcogenide nanostructure material as an artificial enzyme for peroxidase mimics. This provides a method for the naked-eye detection of peroxide in solution. The peroxidase activity was selectively restrained in the presence of glutathione. Hence, a colourimetric assay was simultaneously developed for the selective detection of this biothiol. The intrinsic nanozyme activity of the substrate is hitherto unknown and can, hence, be explored further with other nanostructured nickel selenide materials.

Water oxidation is the bottleneck of artificial photosynthesis. A novel nickel phenolate complex with a redox-active ligand has been designed to manage multiple electron transfers during water oxidation (D. Wang and C. O. Bruner, Inorg. Chem ., 2017, 56 , 13638). However, the mechanism of the reaction is not well understood and verified from a theoretical aspect. Density functional theory calculations were conducted to investigate the mechanism of water oxidation catalyzed by the nickel(II)-phenolate complex. Because only two cyclic voltammogram (CV) peaks were observed and the phenolate ligand is redox-active, the active species was proposed to be Ni III -OH by the experiment. Based on the calculated results, the first CV peak is phenolate ligand-centered and the second peak is a single two-proton-coupled-two-electron process. In addition, the activation barrier of O-O bond formation of Ni III -OH is higher than that of Ni IV -2OH by 15.3 kcal mol -1 . Thus, the redox-active phenolate ligand does not lower the oxidation state of Ni in the active species to Ni III . The oxidation state of the active species is still Ni IV , the same as other Ni complexes for WOCs. As the phenolate ligand and the hydroxyl ligand can act as an internal base, three pathways are compared for O-O bond formation: normal WNA, phenolate-involving single electron transfer (SET)-WNA, and OH-involving SET-WNA. The OH-involving SET-WNA pathway is the most favorable because the hydroxyl ligand is more nucleophilic than the oxygen radical of the phenolate ligand. Based on the experimental observation and theoretical results, the phenolate ligand is not stable and easily oxidized because of the hydrogen at the benzyl position. Thus, WOC candidates should not have the presence of hydrogen at the benzyl position near the active center.

Tetradentate N 2 S 2 coordination platforms are widespread in biological systems and have endowed metalloenzymes and metalloproteins with abundant reactivities and functions. However, there are only three types of N 2 S 2 scaffolds respectively based on the bipyridine, aryl and alkyl amine derivatives, which are significantly underdeveloped for coordination chemistry. With the objective of developing a new N 2 S 2 coordination platform to assemble a series of first-row transition metal complexes, we have designed a novel tetradentate N 2 S 2 ligand containing a central dipyrrin donor functionalized with two thioether-substituted aryl units. Interestingly, complexation of the N 2 S 2 ligand with the chloride salts of Ni(II), Cu(II) and Zn(II) yields various geometries with various coordination numbers. The reaction between the ligand and NiCl 2 readily forms two chloride-bridged centrosymmetric dinickel complexes in which the nickel centers are hexacoordinated by an N 2 S 2 Cl 2 coordination environment in distorted octahedron geometry. In contrast, metalation of the ligand with CuCl 2 gives a mononuclear copper complex consisting of a pentacoordinated copper center in a trigonal bipyramidal geometry with an N 2 S 2 Cl coordination sphere. Unexpectedly, the complexation of the ligand with ZnCl 2 forms a homoleptic zinc complex in which the zinc center is surrounded by an N 4 coordination sphere from two dipyrrin units in a non-planar pseudo-tetrahedral geometry despite the steric hindrance of two bulk thioether-substituted aryl units. These various geometries illustrate the potential structural flexibility of this new ligand. In addition, the optical properties of these compounds were also examined. This work thus provides a new N 2 S 2 coordination platform with geometric flexibility.

A new class of nickel(II) oxyquinoline-bipyridine complexes, namely, [Ni(La1) 2 (Lb6)] (Ni1), [Ni(La1) 2 (Lb2)] ·CH 3 OH (Ni2), [Ni(La7) 2 (Lb11)]·2H 2 O (Ni3), [Ni(La1) 2 (Lb9)] (Ni4), [Ni(La1) 2 (Lb8)] (Ni5), [Ni(La2) 2 (Lb1)] (Ni6), [Ni(La2) 2 (Lb6)]·CH 3 OH (Ni7), [Ni(La2) 2 (Lb11)]·CH 3 OH (Ni8), [Ni(La2) 2 (Lb3)] (Ni9), [Ni(La2) 2 (Lb2)]·CH 3 OH (Ni10), [Ni(La2) 2 (Lb5)]·CH 3 OH (Ni11), [Ni(La2) 2 (Lb7)] (Ni12), [Ni(La3) 2 (Lb2)] (Ni13), [Ni(La4) 2 (Lb4)]·2CH 3 OH (Ni14), [Ni(La4) 2 (Lb8)]·2.5CH 3 OH (Ni15), [Ni(La4) 2 (Lb11)]·1.5CH 3 OH (Ni16), [Ni(La5) 2 (Lb7)] (Ni17), [Ni(La5) 2 (Lb10)]·CH 3 OH (Ni18), [Ni(La6) 2 (Lb11)]·3CH 3 OH (Ni19), [Ni(La7) 2 (Lb7)]·2CH 3 OH (Ni20), [Ni(La7) 2 (Lb8)]·2CH 3 OH (Ni21) and [Ni(La7) 2 (Lb1)]·2CH 3 OH (Ni22) bearing oxyquinoline (H-La1-H-La7) and bipyridine derivatives (Lb1-Lb11) were synthesized and characterized by elemental analysis, X-ray crystallography, infrared (IR) spectroscopy and electrospray mass spectrometry (ESI-MS). An MTT method suggested that the IC 50 values of Ni1-Ni22 for A549/DDP tumor cells were 0.25-25.14 μM, but these complexes exhibited low cytotoxicity toward normal HL-7702 cells (>50 μM). Ni2 could induce A549/DDP tumor cell apoptosis, cause a decrease in the mitochondrial membrane potential (MMP, Δ Ψ m ), and increase the intracellular [Ca 2+ ] and reactive oxygen species (ROS) levels better than Ni10, Ni13, and Ni14. Autophagic and western blot assays showed that Ni2, Ni10, Ni13, and Ni14 could induce autophagy and regulate the expression of LC3 II/I, Beclin1, P62, PINK1, and Parkin proteins, and the inducibility activities were in the order of Ni2 > Ni14 > Ni13 > Ni10. Taken together, these results revealed that the nickel(II) oxyquinoline-bipyridine complex Ni2 inhibited cell growth in A549/DDP tumor cells via mitophagy pathways.

Herein, we synthesized nickel (Ni)-doped iron oxide nanoparticles (Fe 2 O 3 ). The presence of the dopant afforded anchoring sites for the porphyrinic hetero cavity of 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin to produce the porphyrin/Fe 2 O 3 @Ni composite. The crystalline structure and morphology of porphyrin/Fe 2 O 3 @Ni were assessed using various tools including Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. Porphyrin/Fe 2 O 3 @Ni has proven to be an excellent dopamine (DA) probe material with good selectivity, reproducibility, stability and reliability owing to its clever morphology, which induces numerous active sites along with good active surface area. It consequently provides good accessibility to DA and allows for the smooth tunneling of electrons between the analyte and sensing interface. Meanwhile, the porphyrin molecules provide good carbon-based resilient support, inhibit the leaching of the electrode matrix and enhance electron shuttling, resulting in the robust oxidation of DA with amplified transduction signals. The designed porphyrin/Fe 2 O 3 @Ni interface showed a low detection limit (1.2 nm) with good sensitivity (1.2 nM) in the linear bounds of 10 μM to 3500 μM. Additionally, the interface was employed successfully to analyze DA from lacrimal fluid with good percentage recoveries (99.8% to 100.1%). We anticipate that such a design will simplify the in vitro screening of DA in rarely studied tear samples with sensitivity and selectivity.

Ni(II)-tetradentate amido-quinoline complexes effectively catalysed C-H chlorination of a series of hydrocarbons in the presence of NaOCl and acetic acid. The bond dissociation energy of the C(sp 3 )-H bond of the substrates varies from 99.3 kcal mol -1 (cyclohexane) to 87 kcal mol -1 (ethyl benzene). Exclusively chlorinated products (TON: 220 for cyclohexane) were obtained without any hydroxylated products, thus mimicking the activity of the halogenase enzyme.

Metal phosphides have been proved to be potential theranostic agents of tumors. However, the limitations of single-modal imaging or the treatment effect of such materials need to be further improved. Here, we successfully prepared polyvinylpyrrolidone-modified bimetallic nickel cobalt phosphide (NiCoP/PVP) nanoparticles as a theranostic agent of tumors. Owing to the different types of magnetic properties of Ni and Co components, T 1 - and T 2 -weighted magnetic resonance imaging (MRI) could be simultaneously achieved to compensate the low accuracy brought about by single-modal MRI. In addition, NiCoP/PVP possesses excellent photothermal properties owing to its obvious absorption in the near-infrared (NIR) region, which endows NiCoP/PVP with high photothermal conversion efficiency (PCE) to serve as a photothermal agent for tumor ablation. Therefore, NiCoP/PVP is a promising theranostic agent for accurate diagnosis and effective treatment of tumors.

A novel non-enzymatic electrochemical sensor was constructed to achieve a highly selective and ultrasensitive detection of cholesterol to address the problems related to serious coronary heart disease. The NiVP/Pi-based sensor exhibited ultra-high sensitivity of 5510.18 μA μM -1 cm -2 and 36.8 μA μM -1 cm -2 for 1 nM to 10 μM and 100 μM to 10 mM of cholesterol, respectively, with an ultra-low detection limit of 1 aM, along with superior selectivity for cholesterol when exposed to various interferents such as ascorbic acid, glucose and uric acid. Also, a novel NiVP/Pi-based flexible sensor coated onto Whatman filter paper was developed and displayed superior sensitivity, even with a human blood serum sample at physiological pH.

A family of dinuclear complexes based on 2,7-disubstituted 1,8-naphthalenediol-ligands has been designed to bind covalently to two neighboring phosphate diester groups in the backbone of DNA. The dinuclear Cu II and Ni II complexes bind to DNA resulting in the inhibition of DNA synthesis in PCR experiments and in a cytotoxicity that is stronger for human cancer cells than for human stem cells of the same proliferation rate. These experiments support but cannot prove that the dinuclear complexes bind as intended to two neighboring phosphate ester groups of the DNA backbone. Here, we evaluate the potential binding mode of the cytotoxic dinuclear Ni II complex using simple phosphate diester models (dimethyl phosphate and diphenyl phosphate). Depending on the reaction conditions, the phosphate diesters bind to the Ni II ions in a bridging or in a terminal coordination mode. The latter occurs by substitution of two coordinated acetates by the phosphate diesters. This reaction has been followed by NMR spectroscopy, which demonstrates that the substitution of acetate by phosphate is thermodynamically strongly favored, while the exchange with excess phosphate is fast on the NMR time scale. The molecular structure of the Ni II complex with two coordinated diphenyl phosphates served as a model for the computational evaluation of the binding to the DNA backbone. This combined experimental and computational study suggests a monodentate coordination mode of the DNA phosphate diesters to the Ni II ions that is assisted by hydrogen bonds with water ligands.

A bioinspired (N2S2)Ni(II) electrocatalyst is reported that produces H 2 from CF 3 CO 2 H with a turnover frequency (TOF) of ∼1250 s -1 at low acid concentration (<0.043 M) in MeCN. A mechanism for the H 2 production by this electrocatalyst is proposed and its activity is benchmarked against those of other reported molecular Ni H 2 evolution electrocatalysts. The involvement of a hemilabile pyridyl group of the N2S2 ligand is proposed to mimic the role of a cysteine residue involved in the biological proton reduction performed by [NiFe] hydrogenases.

Hydrogen fuel is a promising alternative to fossil fuel. Therefore, efficient hydrogen production is crucial to elucidate the distinctive reactivities of metal hydride species, the intermediates formed during hydrogen activation/evolution in the presence of organometallic catalysts. This study uses density functional theory (DFT) to investigate the isomerizations and reactivities of three nickel-iron (NiFe) hydride isomers synthesized by mimicking the active center of NiFe hydrogenase. Hydride transfer within these complexes, rather than a chemical reaction between the complexes, converts the three hydrides internally. Their reactivities, including their electron-transfer, hydride-transfer and proton-transfer reactions, are investigated. The bridging hydride complex exhibits a higher energy level for the highest occupied molecular orbital (HOMO) than the terminal hydride during the electron-transfer reaction. This energy level indicates that the bridging hydride is more easily oxidized and is more susceptible to electron transfer than the terminal hydride. Regarding the hydride-transfer reaction between the NiFe hydride complex and methylene blue, the terminal hydrides exhibit larger hydricity and lower reaction barriers than the bridging hydride complexes. The results of energy decomposition analysis indicate that the structural deformation energy of the terminal hydride in the transition state is smaller than that of the bridging hydride complex, which lowers the reaction barrier of hydride transfer in the terminal hydride. To produce hydrogen, the rate-determining step is represented by the protonation of the hydride, and the terminal hydrides are thermodynamically and kinetically superior to the bridging ones. The differences in the reactivities of the hydride isomers ensure the precise control of hydrogen, and the theoretical calculations can be applied to design catalysts for hydrogen activation/production.

Cu(II)-peptide complexes are intensely studied as models for biological peptides and proteins and for their direct importance in copper homeostasis and dyshomeostasis in human diseases. In particular, high-affinity ATCUN/NTS (amino-terminal copper and nickel/N-terminal site) motifs present in proteins and peptides are considered as Cu(II) transport agents for copper delivery to cells. The information on the affinities and structures of such complexes derived from steady-state methods appears to be insufficient to resolve the mechanisms of copper trafficking, while kinetic studies have recently shown promise in explaining them. Stopped-flow experiments of Cu(II) complexation to ATCUN/NTS peptides revealed the presence of reaction steps with rates much slower than the diffusion limit due to the formation of novel intermediate species. Herein, the state of the field in Cu(II)-peptide kinetics is reviewed in the context of physiological data, leading to novel ideas in copper biology, together with the discussion of current methodological issues.

A 2D/2D NiCo-MOF/Ti 3 C 2 heterojunction is constructed as a non-enzymatic biosensor for the simultaneous electrochemical detection of acetaminophen (AP), dopamine (DA), and uric acid (UA) via differential pulse voltammetry. Benefiting from the synergistic effects of the high electrocatalytic activity of NiCo-MOF, the outstanding conductivity of Ti 3 C 2 , and the improved specific surface area of NiCo-MOF/Ti 3 C 2 , NiCo-MOF/Ti 3 C 2 displays high sensing performance toward AP (0.01-400 μM), DA (0.01-300 μM), and UA (0.01-350 μM) in 0.1 M phosphate buffer (PB, pH 7.4) at working potentials of 0.346 V vs. SCE for AP, 0.138 V vs. SCE for DA, and 0.266 V vs. SCE for UA. Furthermore, the well-separated oxidation peak potentials allow for the simultaneous detection of the analytes, with detection limits of 0.008, 0.004, and 0.006 μM (S/N = 3), respectively. As a result of its considerable reproducibility and anti-interference and anti-fouling properties, NiCo-MOF/Ti 3 C 2 was also developed into a practical sensing platform to detect AP, DA, and UA in serum and urine, presenting excellent recoveries of 98.1-102.2 %.

Hollow prism-like NiCo 2 S 4 materials (NiCo 2 S 4 HNPs) were successfully fabricated by a two-step method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) confirmed the morphology and structure of the as-prepared NiCo 2 S 4 nanoprisms. A non-enzymatic sensor based on NiCo 2 S 4 HNPs was constructed with outstanding electrochemical activity towards glucose oxidation in alkaline medium. The sensor showed a rapid response time (∼0.1 s), a high sensitivity of 82.9 μA mM -1 cm -2 , a wide linear range (0.005-20.2 mM) and a detection limit of 0.8 μM (S/N = 3) with a good selectivity and reproducibility. Additionally, the proposed electrode also confirmed the feasibility in practical blood serum. These results indicate that NiCo 2 S 4 /ITO has great potential in the development of non-enzymatic glucose sensor applications.

An electrochemical non-enzymatic sensor based on a NiVP/Pi material was developed for the selective and sensitive determination of glucose. The novel sensor showed a high sensitivity of 6.04 mA μM -1 cm -2 with a lowest detection limit of 3.7 nM in a wide detection range of 100 nM-10 mM. The proposed sensor exhibited a superior selectivity without any interference from the oxygen evolution reaction during glucose sensing. We also found that this glucose sensor showed negligible interference from various interferents, such as ascorbic acid, uric acid, dopamine and sodium chloride. Additionally, a novel flexible sensor was developed by coating the NiVP/Pi over Whatman filter paper, which exhibited two linear ranges of 100 nM to 1 μM and 100 μM to 10 mM with an ultra-sensitivity of 1.130 mA μM -1 cm -2 and 0.746 mA μM -1 cm -2 , respectively, in 0.1 M NaOH. The proposed sensor was tested with human blood serum samples demonstrating its practical application. Our findings provide a new route by fine tuning the composition of nickel and vanadium that sheds new light on better understanding the processes. This NiVP/Pi-based sensor offers a new approach towards the electrochemical detection of glucose, enabling glucose monitoring in a convenient way.

Nickel(II) and zinc(II) complexes of various peptide fragments of tau protein have been investigated by potentiometric, UV-Vis, CD and ESI-MS techniques. The peptides include the native fragment tau(9-16) (Ac-EVMEDHAG-NH 2 ), and the Gln/Lys and Tyr/Ala mutated peptides (Ac-KGGYTMHK-NH 2 and Ac-KGGATMHK-NH 2 ) of tau(26-33). Similar to copper(II) the complexes of a chimeric peptide containing both His14 and His32 residues in one molecule (Ac-EDHAGTMHQD-NH 2 ) were also studied. The metal binding ability of the R3 domain was studied by using the native fragment tau(326-333) (Ac-GNIHHKPG-NH 2 ), and its two mutants (Ac-GNIHHKAG-NH 2 ) and (Ac-GNGHHKPG-NH 2 ) and the corresponding 1-histidine mutants (Ac-GNGAHKPG-NH 2 and Ac-GNGHAKPG-NH 2 ). The results of this study reveal that the histidyl residues of the N-terminal and R3 regions of tau protein can effectively bind nickel(II) and zinc(II) ions. In the case of nickel(II) and zinc(II) the M-N im coordinated complexes are the major species in the physiological pH range and their stability is significantly enhanced by the presence of Glu and Asp residues in the neighbourhood of the His14 site. For all studied peptides, nickel(II) ions are able to promote the deprotonation and coordination of amide groups preceding histidine resulting in the exclusive formation of square planar (N im ,3N - ) complexes in alkaline solutions. The native fragment of the R3 region and its mutants containing two adjacent histidine moieties also bind only one nickel(II) ion with the His330 residue being the primary metal binding site. Exclusive binding of the independent imidazole side chains (His14 and His32 sites) cannot prevent the hydrolysis of zinc(II) in a slightly basic solution but the adjacent histidines of the R3 domain can promote the formation of amide coordinated zinc(II) complexes.

The electrochemical water splitting by transition metal complexes is emerging very rapidly. The nickel complexes also play a very vital role in various biological activities. Here, three new ligands {H 2 mbhce = N '-(4-methyl-benzoyl), H 2 pchce = N '-(pyridine-carbonyl) and H 2 hbhce = N '-(2-hydroxy-benzoyl) hydrazine carbodithioic acid ethyl ester} and their corresponding Ni(II) complexes [Ni(Hmbhce) 2 (py) 2 ] (1), [Ni(pchce)( o -phen) 2 ]·CH 3 OH·H 2 O (2) and [Ni(hbhce)( o -phen) 2 ]·1.75CHCl 3 ·H 2 O (3) have been synthesized and fully characterized by various physicochemical and X-ray crystallography techniques. The photoluminescence study and thermal degradations were also examined. The treatment of K562 cells with the increasing concentrations of the nickel salts, ligands, and complexes 1, 2, and 3 showed dose-dependent cytotoxicity. The cytotoxic activity of ligands reveals that ligand H 2 mbhce is more potent in inhibiting the growth of tumor cells in comparison to other ligands H 2 pbhce and H 2 hbhce. Cytotoxicity assay results indicate that all complexes have remarkable cytotoxic potential in comparison to either nickel salts or the free ligands. Among these complexes, complex 1 has significantly better anti-tumor activity as compared to complexes 2 and 3. The electrochemical study of complexes 1, 2, and 3 for water oxidation reveals that all the complexes possess admirable electrocatalytic activity towards oxygen evolution reaction (OER) and have lower overpotential (328, 338, and 370 mV, respectively) than many previously reported complexes and RuO 2 (390 mV). Among complexes 1, 2, and 3, complex-2 shows a better water oxidation response. Consequently, these complexes have great potential to be utilized in fuel cells. The more reliable electrochemical parameter TOF is also calculated for all three complexes.

Non-enzymatic glucose sensors based on metal oxides are receiving remarkable attention owing to their outstanding characteristics of being easy-to use, low cost, and reusability. However, the disadvantage of weak anti-interference associated with poor selectivity significantly restricts their applicability. Herein, we report a two-step in situ fabrication of nanosized CuO encapsulated Ni/Co bimetal Prussian blue (PB) with a typical core-shell structure, which can be efficiently used for non-enzymatic glucose detection, ascribing to the permeability and abundant active sites of out-shelled crystalline porous Ni/Co PB and the high catalytic activity and conductivity of embedded CuO nanoparticles, afforded by their mutual synergistic interactions. The glassy carbon electrode modified with the hybrid of the CuO-encapsulated Ni/Co PB (simplified as the Ni/Co-PB/CuO/GCE electrode) exhibited a high glucose sensitivity of 600 μA mM -1 cm -2 with a low detection limit of 0.69 μM (S/N = 3), a fast response time (less than 3 s), and excellent long-term stability. In addition, the CuO-encapsulated Ni/Co PB showed favorable anti-interference ability in the presence of ascorbic acid (AA), L-lysine (Lys), dopamine (DA), cysteine (Cys), dopamine (DA), and KCl interferences. The reusability and long-term stability, as well as the practicability of the Ni/Co-PB/CuO/GCE sensing electrode verified by testing real serum samples were also investigated, and the experimental results demonstrated the applicability of the core-shell NiCo-PB/CuO based flexible electrochemical sensor for non-enzymatic glucose sensing in practical applications.

HypB is one of the chaperones required for proper nickel insertion into [NiFe]-hydrogenase. Escherichia coli HypB has two potential Ni(II) and Zn(II) binding sites-the N-terminal one and the so-called GTPase one. The metal-loaded HypB-SlyD metallochaperone complex activates nickel release from the N-terminal HypB site. In this work, we focus on the metal selectivity of the two HypB metal binding sites and show that (i) the N-terminal region binds Zn(II) and Ni(II) ions with higher affinity than the G-domain and (ii) the lower affinity G domain binds Zn(II) more effectively than Ni(II). In addition, the high affinity N-terminal domain, both in water and membrane mimicking SDS solution, has a larger affinity towards Zn(II) than Ni(II), while an opposite situation is observed at basic pH; at pH 7.4, the affinity of this region towards both metals is almost the same. The N-terminal HypB region is also more effective in Ni(II) binding than the previously studied SlyD metal binding regions. Considering that the nickel chaperone SlyD activates the release of nickel and blocks the release of zinc from the N-terminal high-affinity metal site of HypB, we may speculate that such pH-dependent metal affinity might modulate HypB interactions with SlyD, being dependent on both pH and the protein's metal status.

Herein, a highly regioselective alkylation of propargylic carbonates for trisubstituted allenes with alkyl 1,4-dihydropyridine derivatives (1,4-DHPs) is developed via a photoredox/nickel dual-catalyzed process, which represents the first direct approach to access alkylated allene products without alkyl organometallic reagents. This method features a broad substrate scope and mild conditions. A hypothetical mechanism with an alkyl radical and an allenyl Ni(III) species is proposed. Benzylation products were also obtained to be the complement building blocks for the potential synthesis of pharmaceuticals.

The construction of cooperative systems comprising several units is an essential challenge for artificial systems toward the development of sophisticated functions comparable to those found in biological systems. Flexible frameworks possessing various functional groups that can form weak intra/intermolecular interactions similar to those observed in biological systems have promising design features for artificial systems used to control cooperative systems. However, it is difficult to construct multiple component systems >1 nm using these flexible units by controlling the arrangement of functional units, beginning with the precise control of the cooperative switching of multiple units. In general, it is difficult for oligopeptides to form stable conformations by themselves, although they have designability and structural features suitable for the development of cooperative systems. Increasing the number of coordination bonds in peptides, which are stronger than hydrogen bonds, can be used to control the assembled peptide structures and stabilize their structures owing to the variety of coordination bonds and selective binding affinity. Thus, metal complexes of artificial short peptides have great potential for the development of multicomponent cooperative systems. Based on this concept, we have developed a series of novel metal complexes of flexible peptides and have achieved, to date, cooperative systems, the formation of giant structures, and precise control over the functional units that are the essential bases for designable multifunctional systems that can be regarded as artificial enzymes. In this feature article, we summarize these results and discuss the principal/essential design of artificial systems.

A hierarchical hollow Ni/Co-codoped MoS2 architecture was successfully prepared using a Ni/Co Prussian Blue analogue as the precursor followed by the solvothermal-assisted insertion of MoS42- and extraction of [Co(CN)6]3- at 200 °C for 32 h. The obtained Ni/Co-codoped MoS2 composite exhibited a hollow microcubic structural characteristic, and the morphology, structure, and chemical compositions were carefully characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. The Ni/Co-codoped MoS2 composite used as an electrode material featured excellent glucose sensing activity and a high sensitivity of 2546 μA mM-1 cm-2 with a relatively low detection limit of 0.69 μM (S/N = 3). In addition, the Ni/Co-codoped MoS2 composite showed good anti-interference sensing performance in the presence of ascorbic acid (AA), lysine (Lys), cysteine (Cys), urea, H2O2, KCl, and other interferents. These experimental results revealed that the composite is a promising electrode material for enzyme-free glucose sensing, and the feasible synthetic strategy may provide an effective and controlled route to prepare other multi-metal substituted sulfide-based hierarchical structures with high electrochemical sensing performance.

Aliphatic artificial α-amino acids (α-AAs) have attracted great interest in biochemistry and pharmacy. In this context, we developed a promising practical protocol for the asymmetric synthesis of these α-AAs through the selective and efficient intermolecular cross-electrophile coupling of Belokon's chiral dehydroalanine Ni(ii) complex with different alkyl and perfluoroalkyl iodides mediated by a dual Zn/Cu system. The reaction afforded diastereomeric complexes with dr up to 21.3 : 1 in 24-95% yields (19 examples). Exemplarily, three enantiomerically pure aliphatic α-AAs were obtained through acidic decomposition of (S,S)-diastereomers of Ni(ii) complexes. Importantly, the chiral auxiliary ligand (S)-BPB ((S)-2-(N-benzylprolyl)aminobenzophenone) was easily recycled by simple filtration after acidic complex decomposition and reused for the synthesis of the initial dehydroalanine Ni(ii) complex.

Nickel has emerged as a desirable substitute for palladium in Sonogashira coupling reactions due to its abundance, less toxicity and high catalytic activity. Ni complexes have been developed to catalyse C(sp)-C(sp 2 ) and C(sp)-C(sp 3 ) Sonogashira couplings that find applications in the synthesis and modifications of biologically relevant molecules. This review focuses on the catalytic potential and mechanistic details of various Ni complexes employed in the Sonogashira coupling. These include homogeneous catalytic systems with Ni-phosphorus and Ni-nitrogen catalysts, ligand-free catalysts, and carbonylative coupling strategies. Various heterogeneous catalytic systems using supported Ni complexes, Ni nanoparticles and Pd-Ni bimetallic catalysts have also been discussed. This is the first review reported so far dealing exclusively with Ni-catalysed Sonogashira coupling reactions. This review illustrates the current strategies and potential of Ni-catalysed Sonogashira coupling reactions in both homogeneous and heterogeneous systems, and covers the literature up to 2020.

Designing metal complexes as functional models for metalloenzymes remains one of the main targets in synthetic bioinorganic chemistry. Furthermore, the utilization of the product(s) derived from the catalytic reaction for subsequent organic transformation that occurs in biological systems is an even more difficult challenge for biochemists. Urease, the most efficient enzyme known, catalyzes the hydrolysis of urea and it contains an essential dinuclear Ni II cluster in the active site. Inspired by the catalytic properties of urease, two dinickel(ii) complexes viz. Ni 2 L 1 2 (OAc) 2 (H 2 O) (1) and Ni 2 L 2 2 (OAc) 2 (H 2 O) (2) [HL1 = 2,4-dimethyl-6-{[(2'-dimethyl aminoethyl)methylamino]methyl}-phenol and HL2 = 2,4-dichloro-6-{[(2'-dimethyl aminoethyl)methylamino]methyl}-phenol] have been synthesized and characterized in this report. Both the complexes have shown the urease kind of activity with the liberation of ammonia from urea in aqueous solution. The plausible mechanistic pathway and kinetics of the reactions have been studied. Besides, the liberated ammonia has been utilized in the one-pot synthesis of biologically active products like 2-amino-3-cyanopyridines and their derivatives in aqueous medium with excellent yields.

A new Ni(ii) complex [NiL] (complex 1) of an asymmetrically di-condensed N 2 O 3 donor Schiff base ligand, N-salicylidene-N'-3-methoxysalicylidene-1,3-propanediamine (H 2 L), has been synthesized and utilized for the synthesis of three heterometallic complexes, [(NiL) 2 Mn(NCS) 2 (CH 3 OH) 2 ]·CH 3 OH (2) [(NiL) 2 Mn(N(CN) 2 ) 2 (CH 3 OH) 2 ]·CH 3 OH (3) and [(NiL) 2 Mn 2 (N 3 ) 2 (μ 1,1 -N 3 ) 2 (CH 3 OH) 2 ] (4). Single crystal X-ray diffraction analyses show that complexes 2 and 3 have linear trinuclear structures where two tridentate O 3 donor (NiL) units are coordinated to the central octahedral Mn(ii) centre, whereas complex 4 has a centrosymmetric tetranuclear structure where two binuclear (NiL)Mn units are linked via two phenoxido and two μ 1,1 -N 3 bridges. Among the heterometallic complexes (2-4), only 4 is active towards the catalytic oxidation of 3,5-di-tert-butylcatechol to the corresponding quinone. The turnover number for the aerobic oxidation of 3,5-DTBC is 935 h -1 . ESI-mass spectra have been recorded to scrutinize the mechanistic pathway of this catalytic reaction. Variable temperature magnetic susceptibility measurements suggest that complexes 2-4 are antiferromagnetically coupled with coupling constants (J) of -4.84 and -5.23 cm -1 for complexes 2 and 3, respectively and J 1 = -2.20 cm -1 , J 2 = 1.13 cm -1 and J 3 = -1.12 cm -1 for complex 4. DFT calculations have been used to rationalize the magnetic super-exchange in complexes 2-4, by computing the theoretical coupling constants and analyzing the spin density plots.

A facile and single-step nickel oxide-dispersed in situ grown 3-D graphitic forest engrained carbon foam (NiO-CNF-CF)-based electrode was fabricated for high-performance microbial fuel cells (MFCs). The metal oxide, graphitic contents, biocompatibility, stability and large surface area available in the material for biofilm formation rendered the prepared electrode competent for wastewater treatment and bioenergy (0.79 V and 1.955 W m-2) generation with a coulombic efficiency of 85.66%.

The major obstacle to developing nanozymes which are considered as promising alternatives to natural enzymes is their moderate performance, including poor affinity for substrates, low catalytic activity, and severe pH-dependence. To address these issues, herein, we synthesize ultrathin layered double hydroxide (LDH) nanosheets with a thickness of 1.4 nm and an average lateral size of 23 nm using a fast-precipitation method. Through the rational design of their compositions, it is found that NiMn LDHs exhibit the optimum peroxidase mimicking performance with excellent substrate affinity, high catalytic activity (a limit of detection (LOD) of 0.04 μM H 2 O 2 ) and robustness in a wide pH range (from 2.6 to 9.0), which is superior to that of natural horseradish peroxidase (HRP). The main active centers are identified as Mn sites because of their strong Lewis acidity and low redox potential. Furthermore, a series of disposable paper bioassays based on NiMn LDH nanozymes are designed and used for the highly sensitive detection of H 2 O 2 and ascorbic acid (AA).

In this work, Ni-doped ZrO 2 nanoparticles (NPs) were used to decorate multi-walled carbon nanotubes (MWCNTs) to obtain a Ni-ZrO 2 /MWCNT nanocomposite, which acted as an efficient electrode material for the highly sensitive electrochemical detection of the anti-inflammatory drug 5-amino salicylic acid (5-ASA). The Ni-ZrO 2 NPs were obtained through a facile co-precipitation method, and the subsequent support of these Ni-ZrO 2 NPs onto MWCNTs was accomplished via an ultrasonication technique. Supporting Ni-ZrO 2 NPs on MWCNTs not only results in excellent catalytic properties, but it also substantially enhances the surface area, electrical conductivity, and electron transfer process. The electrochemical activity of the synthesized Ni-ZrO 2 /MWCNT nanocomposite was systematically investigated via cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The constructed Ni-ZrO 2 /MWCNT-modified glassy carbon (GC) electrode manifests superior electrocatalytic oxidation activity toward 5-ASA, with a lower peak potential compared with Ni-ZrO 2 -NP- and MWCNT-modified GC electrodes. Importantly, the proposed biosensor exhibited excellent sensitivity during the detection of 5-ASA with a wide linear concentration range (0.001-500 μM) and a low detection limit of 0.0029 μM. Moreover, the biosensor demonstrated excellent repeatability, reproducibility, stability, and high specificity toward 5-ASA detection in the presence of different interfering species. Furthermore, the biosensor showed satisfactory recovery rates in complex biological samples, such as human blood serum, human urine, and 5-ASA tablet samples.

Replacing coenzyme F 430 , an Ni(i) F 430 -like cofactor derived from vitamin B 12 (F 430-B12 ) is revealed by DFT calculations to be able to catalyze methane formation in methyl-coenzyme M reductase with a barrier of 13.3 kcal mol -1 , demonstrating the correctness of the route starting from vitamin B 12 . The structure-activity relationships of F 430 and F 430-B12 (especially the roles of the F ring) are discovered and several sources of inspiration promoting the application of F 430-B12 are also obtained, coming closer to using F 430 chemistry in man-made catalysis.

Novel hierarchical CuNiAl layered double hydroxide (CuNiAl LDH) nanotubes were prepared with in situ transformation of Al 2 O 3 produced using the atomic layer deposition (ALD) method. Based on the characterizations using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FT-IR spectrometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), CuNiAl LDH displays a typical nanotube-like structure consisting of uniform ultrathin nanoflakes. It is also confirmed that nitrate precursors play a crucial role in the formation of the LDH hierarchical structure. The unique hierarchical tube-like structure for CuNiAl LDH can supply more active sites and higher surface areas, leading to outstanding peroxidase mimicking property. The kinetic analyses indicate that the catalytic behavior of CuNiAl LDH follows classic Michaelis-Menten models and the affinity of CuNiAl LDH to the substrate is significantly higher than horseradish peroxidase. A simple and label-free method was developed for the colorimetric detection of glucose. As low as 2.9 μM of glucose can be detected with a broad linear range from 10 to 200 μM. The established method is also proved to be suitable for glucose detection in juice samples.

A 2D CuNi metal-organic framework (MOF) named CuxNi3-x(HHTP)2 was synthesized with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as the linker and was used as a sensitive scaffold to adsorb aptamer strands for the electrochemical detection of living C6 glioma cells and one of their biomarkers, epidermal growth factor receptor (EGFR). Different from conventional MOFs, the CuxNi3-x(HHTP)2 MOF comprises long-range delocalized electrons, a graphene-analog nanostructure, multiple metal states (Cu0/Cu+/Cu2+ and Ni2+/Ni3+), and abundant oxygen vacancies. With these features, the CuxNi3-x(HHTP)2 MOF anchored a large amount of C6 cell-targeted aptamer strands via coordination among metal centers, oligonucleotides, π-π stacking, and van der Waals force. The CuxNi3-x(HHTP)2-based cytosensor showed a low limit of detection (LOD) of 21 cells mL-1 toward C6 glioma cells within a wide range from 50 cells mL-1 to 1 × 105 cells mL-1. Moreover, the proposed aptasensor displayed high selectivity, good stability, acceptable reproducibility, and a low LOD of 0.72 fg mL-1 for detecting EGFR with the concentration ranging from 1 fg mL-1 to 1 ng mL-1. The aptasensor based on the CuxNi3-x(HHTP)2 MOF exhibited superior sensing performance over those based on its monometallic analogues such as Cu3(HHTP)2 MOF and Ni3(HHTP)2 MOF. Hence, this sensing strategy based on a bimetallic semiconducting MOF shows great potential for cancer diagnosis.

Two sets of macrocyclic, bio-inspired, non-heme ligands are utilized for the synthesis of NiII, PdII and PtII complexes. The ligands consist of a 16-atom macrocycle, formed by four methylene bridged NHC moieties, with imidazole or benzimidazole as building blocks. The complexes exhibit a square planar coordination geometry and are characterized by NMR, ESI-MS, elemental analysis, SC-XRD and UV/Vis. For complexes incorporating benzimidazole, an evaluation of luminescence properties is performed, and is found that phosphorescence is present for the PdII derivative and there is fluorescence for the PtII derivative. Stability studies in cell culture medium are performed for subsequent MTT assays. Here, the NiII complexes show low to no activity, and PdII and PtII complexes exhibit remarkable low IC50 values in cisplatin resistant A2780cisR cells.

We present a novel fuel cell heterogeneous catalyst based on rhodium, nickel and sulfur with power densities 5-28% that of platinum. The NiRhS heterogeneous catalyst was developed via a homogeneous model complex of the [NiFe]hydrogenases (H 2 ases) and can act as both the cathode and anode of a fuel cell.

Fe-Ni-MOFs with different amounts of Fe are synthesized through a two-step template etching method. Kinetic analysis indicates that Fe-Ni-MOF exhibits prominent intrinsic peroxidase-like activity, which could catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to produce oxidized TMB (oxTMB) with a blue color. As a peroxidase-mimicking MOF, Fe-Ni-MOF with its efficient stable catalysis properties is demonstrated to allow a sensitive colorimetric assay for Sn2+ ions. The mechanism is explored, whereby Sn2+ ions could reduce the peroxidase-like activity of Fe-Ni-MOF based on a redox interaction, making the oxTMB color lighter and decreasing the absorbance intensity at 652 nm. The linear determination of the Sn2+ ion concentration using a UV-vis spectrometer ranges from 0.01 mM to 1.0 mM and from 1.0 mM to 4.0 mM. The presented Fe-Ni-MOF-based assay of Sn2+ ions was successfully applied to real water samples.