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A composite modified electrode was prepared based on α-K 7 P 2 VW 17 O 62 ·18H 2 O (P 2 W 17 V), CNTs and AuCo nanoparticles (AuCo NPs), and used as a structurally stable and highly sensitive electrochemical sensor for simultaneous determination of dopamine (DA) and uric acid (UA). The combination of three active components endows the electrode with large specific surface area, high electrical conductivity, and excellent electrochemical activity. The as-prepared modified electrode exhibited impressive electrocatalytic oxidation performance of DA and UA at an optimum working potential (0.172 V vs. Ag/AgCl for DA and 0.288 V vs. Ag/AgCl for UA) with linear detection range from 1.25 × 10 −6 to 2.81 × 10 −4  M and 0.75 × 10 −6 to 1.66 × 10 −4  M and the detection limit of 0.15 and 0.25 μM (S/ N  = 3) for DA and UA, respectively. Additionally, the peak-to-peak separation signals in DPV are 116 mV. The influence of several possible co-existing substances was investigated. The applicability of the method for real samples analysis was tested by determination of DA and UA in human serums. This new sensor holds great promise for sensitive determination of DA and UA in real application. Graphical abstract

High-energy density supercapacitors have attracted extensive attention due to their electrode structure design. A synergistic effect related to core–shell structure can improve the energy storage capacity and power density of electrode materials. The Ni-foam (NF) substrate coupled with polypyrrole (PPy) conductive coating can serve as an internal/external bicontinuous conductive network. In this work, the distinctive PPy@FeNi2S4@NF and PPy@NiCo2S4@NF materials were prepared by a simple two-step hydrothermal synthesis with a subsequent in situ polymerization method. PPy@FeNi2S4@NF and PPy@NiCo2S4@NF could deliver ultrahigh specific capacitances of 3870.3 and 5771.4 F·g−1 at 1 A·g−1 and marvelous cycling capability performances of 81.39% and 93.02% after 5000 cycles. The asymmetric supercapacitors composed of the prepared materials provided a high-energy density of over 47.2 Wh·kg−1 at 699.9 W·kg−1 power density and 67.11 Wh·kg−1 at 800 W·kg−1 power density. Therefore, the self-assembled core–shell structure can effectively improve the electrochemical performance and will have an effective service in advanced energy-storage devices.

J‐aggregation and H‐aggregation are identified as two classical models of functionally oriented non‐covalent interactions, and significant attention has been drawn by researchers. However, due to the scarcity of single‐crystal examples of H‐aggregation, a comprehensive understanding of the relationship between its stacking mode and optical behaviour has been hindered. In recent studies, two polyaromatic Schiff base compounds, Cl‐Salmphen and H‐Salmphen, were successfully synthesized, and both were found to exhibit H‐aggregation. In the findings, H‐Salmphen was shown to display typical C─H···π interactions, characteristic of Aggregation‐Induced Emission (AIE) active molecules, whereas its halogenated counterpart was identified as behaving similar to Aggregation‐Caused Quenching (ACQ) active molecules. These types of results suggest that identical intermolecular interactions can produce differing optical behaviours. Light was shed, at least in part, on the formation mechanisms of H‐type aggregates and their luminescence properties from these observations. Additionally, the high optical signal‐to‐noise ratio inherent to H‐aggregates was utilized for the exploration of water content detection. As an outcome, a high‐performance fluorescent filter paper was developed, enabling easy real‐time detection using a smartphone. The Cl‐Salmphen and H‐Salmphen are isomers with H‐aggregation characteristics, despite their primary structures comprising multiple aromatic rings, no conventional π–π interactions associated with H‐aggregation were identified. Instead, the interplay between adjacent molecules appears to be orchestrated by C─H···π bonds Moreover, the non‐halogenated H‐Salmphen displayed AIE behaviour dominated by C─H···π interactions, its halogenated counterpart, Cl‐Salmphen, exhibited C─H···π‐dominated ACQ activity.

Optical signals of pH probes mainly driven from the formation or rupture of covalent bonds, whereas the changes in covalent bonds usually require higher chemical driving forces, resulting in limited sensitivity and reversibility of the probes. The exploration of high-performance pH probes has been a subject of intense investigation. Herein, a new pH probe has been developed, with optical property investigation suggesting the probe has excellent signal-to-noise ratio, and fluorescence intensity shows exponential growth, combined with a visible color change, as pH increased from 5.1 to 6.0; Moreover, the probe has outstanding stability and reversibility, with more than 90% of the initial signal intensity remaining after 30 cycles. In order to better understand the special fluorescence behavior of the reported probe, the non-halogenated isomer is introduced for comparison, combined with the results of structural analysis, quantitative calculation and optical experiments, and the possible mechanism of the special supramolecular aggregation-caused quenching effect induced by the halogen atom is discussed.

A Cr-based metal-organic framework MIL-101(Cr) was used to load platinum nanoparticles (PtNPs) that were placed on a glassy carbon electrode (GCE). The modified GCE was used as a non-enzymatic xanthine sensor. Compared to bare GCE, it requires a strongly decreased working potential and an increased signal current for xanthine oxidation. This is due to the crystalline ordered structure and large specific surface of the MIL-101(Cr), and to the high conductivity of the Pt NPs. Differential pulse voltammetry (DPV) shows the sensor to have a wide linear range (0.5 – 162 μM), a low detection limit (0.42 μM), and high selectivity. It was applied to the simultaneous determination of dopamine, uric acid, xanthine and hypoxanthine at working potentials of 0.13, 0.28, 0.68 and 1.05 V, respectively (vs. Ag/AgCl) and to quantify xanthine in spiked serum samples. Graphical abstract This is the first report of non-enzymatic xanthine electrochemical sensor based on metal-organic framework loaded with nanoparticles.

The development of high-performance fluorescence probes has been an active area of research. In the present work, two new pH sensors Zn-3,5-Cl-saldmpn and Zn-3,5-Br-saldmpn based on a halogenated Schiff ligand (3,5-Cl-saldmpn = N, N′-(3,3′-dipropyhnethylamine) bis (3,5-chlorosalicylidene)) with linearity and a high signal-to-noise ratio were developed. Analyses revealed an exponential intensification in their fluorescence emission and a discernible chromatic shift upon pH increase from 5.0 to 7.0. The sensors could retain over 95% of their initial signal amplitude after 20 operational cycles, demonstrating excellent stability and reversibility. To elucidate their unique fluorescence response, a non-halogenated analog was introduced for comparison. The structural and optical characterization suggested that the introduction of halogen atoms can create additional interaction pathways between adjacent molecules and enhance the strength of the interaction, which not only improves the signal-to-noise ratio but also forms a long-range interaction process in the formation of the aggregation state, thus enhancing the response range. Meanwhile, the above proposed mechanism was also verified by theoretical calculations.

Electrocatalytic nitrate reduction to ammonia (ENRA) is a sustainable strategy for decentralized ammonia synthesis and wastewater purification, but its efficiency in neutral media is limited by slow water dissociation and insufficient active hydrogen (*H) supply. Herein, we address this challenge through the rational design of chain-like polyoxometalate-based metal-organic complexes that feature dinuclear ([M(H O) C O N H ] [SiW O ], M-SiW -1D) and trinuclear ([M (H O) C O N H ] [PW W O ], M-PW -1D) architectures (M = Ni, Co, Fe) that create continuous electron channels. Among them, trinuclear Ni-PW -1D exhibits exceptional ENRA performance in neutral electrolytes, delivering a very high Faradaic efficiency of 95.0% and a remarkable ammonia yield rate of 16.9 mg h mg at -1.2 V vs. RHE. In situ Fourier-transform infrared spectroscopy, differential electrochemical mass spectrometry, and density functional theory calculations are used to elucidate the synergistic mechanism operating in this system: polyoxometalate (POM) moieties promote water dissociation to generate *H that migrates to metal-organic reaction sites. Meanwhile, electron transfer from the POM to the metal cluster enhances the adsorption of the nitrate intermediate and lowers the energy barrier of the rate-determining step (NO → *NOH). This synergy balances hydrogenation and suppresses the competing hydrogen evolution reaction, providing insights into multinuclear cluster structure-activity relationships for sustainable nitrogen cycling.

Electrocatalytic water splitting is one of the green and sustainable hydrogen energy methods. However, the hydrogen evolution reaction (HER) suffers from slow kinetics due to the high energy barrier of the H–O bond in a water molecule. The key to boosting HER is to add efficient electrocatalysts. In this paper, by a facile one-pot sulphuration method, the Waugh-type polyoxometalate ((NH4)6[MnMo9O32]) is firstly used as raw materials, and uniform bimetallic sulfides are in situ coupled on high conductivity nickel foam (NF) substrates to form a series of MnS-MoS2-NF electrocatalysts. As a result, the catalysts possess ultrahigh catalytic activity for hydrogen evolution reaction in alkaline electrolyte, showing a low overpotential of 56 mV at a current density of 10 mA cm−2, which is close to that 35 mV dec−1 of the 20% Pt/C electrode. Also, Meanwhile, 24 h I–T test and scanning electron microscopy observation were carried out before and after the experiment, which proved that the material has long-term stability. This work provides a feasible strategy for the rational design and preparation of highly efficient HER electrocatalysts.A bimetallic electrocatalyst were synthesized via coupling of MnS-MoS2 on nickel foam, which shows ultrahigh electrocatalytic-activity for hydrogen evolution reaction.

A stable and innovative composite film-modified electrode based on Dawson polyoxometalates H 8 P 2 Mo 16 V 2 O 62 (P 2 Mo 16 V 2 ) and ionic liquid (BMIMBr)-decorated carbon nanotubes, annotated as PEI/(P 2 Mo 16 V 2 /BMIMBr-CNTs) 8 , has been constructed by using the layer-by-layer self-assembly (LBL) method for the determination of L-tyrosine. The combination of three active components not only offers higher conductivity to facilitate rapid electron transfer, but also avoids the accumulation of P 2 Mo 16 V 2 to expand the contact area and increase the reactive active sites. The modified electrode exhibits outstanding sensing performance for determination of Tyr with wide linear determination range of 5.8×10 −7 M ~ 1.2×10 −4 M, low determination limit of 1.7×10 −7 M (S/N=3), high selectivity for common interferences, and excellent stability at the potential of +0.78 V (vs. Ag/AgCl (3 M KCl)). The relative standard deviation (RSD) of 4.3% for five groups of parallel experiments shows the satisfactory repeatability of PEI/(P 2 Mo 16 V 2 /BMIMBr-CNTs) 8 . In addition, for determination of Tyr, the PEI/(P 2 Mo 16 V 2 /BMIMBr-CNTs) 8 shows good recoveries of 98.8–99.8% in meat floss, which can be feasible in practical application. Graphical abstract

A composite material based on CuFe-ZIF-derived CuFe 2 O 4 nano-microspheres grown in situ and well-ordered on carbon sheets (CS) was prepared and applied for highly effective determination of bisphenol A (BPA). The composite material possessed inherently high redox activity due to the presence of both Cu and Fe ions with various oxidation states (Cu²⁺/Cu⁺ and Fe³⁺/Fe²⁺), high specific surface area, uniform distribution of Cu and Fe ions, and a robust framework imparted by its precursor CuFe-ZIF. This led to increased active sites for electrochemical reactions, improved electron transfer efficiency, and structural integrity during electrochemical cycling. Furthermore, combining CS with CuFe 2 O 4 not only provided a large surface area to support well-ordered CuFe₂O₄ nano-microspheres without aggregation, but also enhanced the conductivity and mechanical stability of the CuFe₂O₄/CS composite. This results in synergistic effects that enhanced the overall performance of the composite material. In addition, both copper and iron are relatively non-toxic and abundant, making CuFe₂O₄/CS safe and cost-effective for large-scale applications. Consequently, the CuFe 2 O 4 /CS-modified electrode shows highly efficient electrochemical sensing properties with a wider detection range of 0.009-168 µM and lower detection limit of 0.0027 µM (S/ N  = 3) compared with most reported BPA sensors. It also has an optimized current at pH 7 which is convenient for real world applications. This CuFe 2 O 4 /CS modified electrode as a highly sensitive electrochemical platform can be applied to monitor BPA concentrations in bottled water with good recovery (97.2-102.2%). Graphical Abstract