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Ultrathin porous and highly curved two-dimensional PdCu alloy metallene are shown to be highly efficient oxidase mimics. Serving as intrinsic oxidase mimic, the ultrathin porous structure of the PdCu metallenezymes could effectively utilize all the Pd atoms of the metallenezymes during catalytic reactions. By using the oxidation capability of 3,3′5,5′–tetramethylbenzidine as distinctive chromogenic substrate, the PdCu metallenezymes was used as oxidase-like mimics for determination of total antioxidant capacity (TAC) of vitamin C containing real products including fresh orange juice, commercial beverages, Vitamin C tablets and dermo-cosmetic products. AAP was hydrolyzed using ALP to generate AA and the corresponding ALP activity was successfully detected in the 0–100 U/L range with a lowest detection limit of 0.9 U/L. This study demonstrates the significant catalytic performance and oxidase-like activity of PdCu metallene nanozyme providing a strategy to develop a TAC assay for the assessment of antioxidant food quality as well as oxidative stress in skin and health care products. [ABSTRACT FROM AUTHOR]

A highly efficient and durable electrocatalyst of Pd hydride nanocubes encapsulated within 2D amorphous Ni-B nanosheets is reported. The PdH0.43 nanocubes are first synthesized via a simple N, N-dimethylformamide thermal treatment. The as-synthesized PdH0.43 nanocubes are then encapsulated in 2D amorphous NiB nanosheets by NaBH4 reduction in the presence of nickel species. During the NaBH4 treatment, the PdH0.43 can be further transformed into PdH0.706 due to the presence of endogenous H2. Electrochemical studies demonstrate that the degree of hydride of Pd nanocubes (PdH x) plays an important role in the enhancement of their oxygen reduction reaction (ORR) activity. With increasing x value, both the activity and stability increase significantly. At 0.90 V versus reversible hydrogen electrode, the ORR activity of PdH0.706 @Ni-B reaches 1.05 A mgPd−1, which is nearly five times higher than that of the state-of-the-art Pt catalysts. Accelerated durability tests show that even after 10 000 potential cycles, there is negligible shift in their half-wave potential and no shape and structure change occurs, indicating the incorporation of amorphous 2D Ni-B nanosheets can greatly improve their stability without compromising their activity. The present study illustrates the importance of high degree of hydride and presence of amorphous Ni-B nanosheets on the enhancement of ORR activity for Pd-based electrocatalyst. [ABSTRACT FROM AUTHOR]

By controlling the surface structure and composition at the atomic level, the catalytic properties of bimetallic alloy catalysts can be precisely and effectively tuned, and their activity and durability can be enhanced. Here, a class of highly active and durable PdAg bimetallic alloy nano-electrocatalysts is demonstrated by tuning the surface composition through a simple electrochemical treatment process in acid medium. Transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammogram measurements clearly show the well-defined core-shell structure that consists of a PdAg alloy core and a few atomic layers of Pd as the shell (PdAg@Pd). Compared to pure Pd and Ag catalysts, the prepared PdAg@Pd/C exhibits enhanced electrocatalytic activity and durability for the oxygen reduction reaction in alkaline media. According to the theoretical and experimental results, the enhanced electrocatalytic activity can be attributed to the synergistic effects between the Pd and the Ag, while the durability is ascribed to the unique alloy core-ultrathin-Pd-shell structure of the PdAg@Pd/C catalyst. This study not only proposes a simple and straightforward approach for preparing highly monodisperse PdAg alloy nanoparticles and designing advanced electrocatalysts for fuel cells, but also demonstrates the crucial effect of electrochemical treatment on the electrocatalytic properties of catalysts. [ABSTRACT FROM AUTHOR]

We report here a facile colorimetric sensor based on the N -acetyl- l -cysteine (NALC)-stabilized Ag nanoparticles (NALC–Ag NPs) for detection of Fe 3+ ions in aqueous solution. The Ag NPs with an average diameter of 6.55 ± 1.0 nm are successfully synthesized through a simple method using sodium borohydride as reducing agent and N -acetyl- l -cysteine as protecting ligand. The synthesized silver nanoparticles show a strong surface plasmon resonance (SPR) around 400 nm and the SPR intensity decreases with the increasing of Fe 3+ concentration in aqueous solution. Based on the linear relationship between SPR intensity and concentration of Fe 3+ ions, the as-synthesized water-soluble silver nanoparticles can be used for the sensitive and selective detection of Fe 3+ ions in water with a linear range from 80 nM to 80 μM and a detection limit of 80 nM. On the basis of the experimental results, a new detection mechanism of oxidation–reduction reaction between Ag NPs and Fe 3+ ions is proposed, which is different from previously reported mechanisms. Moreover, the NALC–Ag NPs could be applied to the detection of Fe 3+ ions in real environmental water samples. [ABSTRACT FROM AUTHOR]

Due to the high costs, slow reaction kinetics, and methanol poisoning of platinum-based cathode catalysts, designing and exploring non-Pt or low-Pt cathode electrocatalysts with a low cost, high catalytic performance, and high methanol-tolerance are crucial for the commercialization of fuel cells. Here, a facile method to fabricate a system of PdAg nanorings supported by graphene nanosheets is demonstrated; the fabrication is based on the galvanic displacement reaction between pre-synthesized Ag nanoparticles and palladium ions. X-ray diffraction and high-resolution transmission electron microscopy show that the synthesized PdAg nanocrystals exhibit a ring-shaped hollow structure with an average size of 27.49 nm and a wall thickness of 5.5 nm. Compared to the commercial Pd-C catalyst, the PdAg nanorings exhibit superior properties as a cathode electrocatalyst for oxygen reduction. Based on structural and electrochemical studies, these advantageous properties include efficient usage of noble metals and a high surface area because of the effective utilization of both the exterior and interior surfaces, high electrocatalytic performance for oxygen reduction from the synergistic effect of the alloyed PdAg crystalline phase, and most importantly, excellent tolerance of methanol crossover at high concentrations. It is anticipated that this synthesis of graphene-based PdAg nanorings will open up a new avenue for designing advanced electrocatalysts that are low in cost and that exhibit high catalytic performance for alkaline fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Highly dispersed Pd nanoparticles (NPs) supported on graphene were successfully prepared by a one-step electrochemical codeposition approach. The as-obtained nanocomposite was very “clean” as a result of the reductant-free and surfactant-free synthesis process. The catalyst remarkably improved the electrocatalytic performance for formic acid oxidation (FAO). This facile and controllable method is of significance for the preparation of graphene–metal NPs with desirable catalytic performance. [Copyright &y& Elsevier]

Abstract: Two different sized silver nanoclusters are prepared by two different synthetic routs. First, a small nanocluster (NC) which is 0.7nm in diameter was synthesized by using meso-2, 3-dimercapto-succinic acid (DMSA) as a capping ligand, and second a larger nanoparticle (NP) which is 3.3nm in diameter was prepared by chemical reduction and coated with DMSA. The as-prepared silver nanoclusters or nanoparticles are then loaded onto a glassy carbon electrode and the size effect on their electrocatalytic activity toward oxygen reduction reaction (ORR) is investigated with electrochemical techniques in alkaline electrolyte. The cyclic voltammetric (CV) studies show that the onset potential of ORR on 0.7nm silver nanoclusters is 150mV more positive than that from 3.3nm silver nanoparticles. And compared to the larger nanoparticles, five times higher current density of ORR at −0.80V is obtained from the 0.7nm silver nanoclusters. These CV results indicate that the smaller Ag nanoclusters exhibit higher catalytic performance for ORR. Rotating disk voltammetric studies show ORR on both DMSA monolayer-protected silver clusters is dominated first by a two-electron transfer pathway to produce H2O2 and then peroxide is reduced by 2 more electrons to produce water. [Copyright &y& Elsevier]

Abstract: Uniform and ultralong silver nanorods are synthesized with a wet chemical reduction method by using PVP as a stabilizer. The crystal structure and morphology of the synthesized nanorods are characterized with transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and UV–vis absorption spectroscopy. The electrocatalytic activity of the Ag nanorods with and without PVP stabilizer, towards oxygen reduction reaction (ORR), is studied and compared by cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements in alkaline solution. Compared to the low current density and incomplete two-electron reaction process of ORR with PVP-protected Ag nanorods, the catalytic activity of the Ag nanorods with removal of the PVP is found to be enhanced remarkably with much higher oxygen reduction current density and the most efficient four-electron process. [ABSTRACT FROM AUTHOR]

Doping specific active sites and accelerating the decisive step of glucose catalysis to construct highly active glucose sensing electrochemical catalysts remains a major challenge for glucose sensing. Herein, we report the detailed design of Cu–Co dual active site N-doped carbon nanotube (CuCo-NCNTs) obtained by electrodeposition modification, programmed warming and calcination for electrochemical glucose detection. In the CuCo-NCNTs material system, Cu serves as the main active site for glucose sensing. Co with good adsorption of hydroxyl groups acts as the site providing hydroxyl groups to provide oxygen source for Cu oxidized glucose sensing. The synergistic effect between the two active sites in the Cu–Co system and the abundant micro-reactive sites exposed by carbon nanotubes greatly ensure the excellent electrocatalytic performance of glucose oxidation reaction. Therefore, CuCo-NCNTs have good electrocatalytic performance with a sensitivity of 0.84 mA mM−1 cm−2 and a detection limit of 1 μM, and also have excellent stability and specificity. DFT calculations elucidate the decisive steps of H-atom removal in the oxidation of glucose by Cu active site N-doped carbon nanotube (Cu-NCNTs) and Co active site N-doped carbon nanotube (CuCo-NCNTs) materials, illustrating the role of oxygen source provided by hydroxyl group adsorption in the electrochemical sensing process of glucose, thus demonstrating that the electrochemical sensing signal of glucose can be effectively enhanced when cobalt species that readily adsorb hydroxyl groups are introduced into the materials. [Display omitted] • The introduction of Co sites enhances the ability of the material to adsorb hydroxyl groups. • Hydroxyl adsorption provides an oxygen source to promote the sensing performance of Cu on glucose oxidation process. • The synergistic promotion of Cu–Co dual active site was corroborated by DFT calculations. [ABSTRACT FROM AUTHOR]

The modified carbon nitride nanozyme could realize biomimetic catalysis application for evaluation of total antioxidant capacity via self-cascade photocatalytic H 2 O 2 production. [Display omitted] The peroxidase mimics usually requires the addition of exogenous hydrogen peroxide (H 2 O 2), which greatly hinder their practical applications. Herein, through rational co-modification of multiple elements (potassium (K), chlorine (Cl) and iodine (I)), the modified carbon nitride nanomaterials (KCl/KI-CN) could serve as efficient bifunctional catalysts. The multiple elements doping and the incorporation of cyano groups (C N) are deemed to enhance their photocatalytic and peroxidase-like activity, respectively. Based on the photocatalytic function, H 2 O 2 can be produced continuously and steadily via two-electron oxygen reduction over modified carbon nitride under visible light irradiation. Subsequently, the KCl/KI-CN could catalyze the chromogenic substrate by the in-situ produced H 2 O 2. Taking advantage of the bifunctional properties of modified carbon nitride, we for the first time demonstrate a self-cascade catalytic process and apply successfully for the ascorbic acid (AA) detection and versatile total antioxidant capacity (TAC) evaluation. This paper not only prepares an efficiently bifunctional catalyst but also provides a new self-cascade photocatalytic H 2 O 2 production strategy for the peroxidase-like application. [ABSTRACT FROM AUTHOR]

Electrochemical energy conversion and storage are important and coupled with a number of electrocatalytic processes. Renewable hydrogen, as a promising energy carrier, is closely related to the oxygen evolution reaction (OER). However, the OER kinetics is slow due to the slow 4e− transfer process. The low-cost transition metal-based catalysts provide broad prospects for the development of efficient and stable OER catalysts. Designing an efficient transition metal-based OER catalyst is beneficial to improve the overall efficiency of water decomposition. Here, we developed a new three-dimensional carbonized polyaniline fiber material loaded with Fe–Co oxide nanoparticle (denoted as 3D-CPF/FeCoOx-Nanoparticles) material by doping Fe to activate the catalytic activity of cobalt-based catalysts, introducing new reaction pathways and using the synergistic enhancement between metal nanoparticles and carbonized polyaniline fibers. Benefiting from the synergistic enhancement of the conductive three-dimensional carbonized polyaniline fibers and the high catalytic activity of FeCoOx nanoparticles, the 3D-CPF/FeCoOx-Nanoparticles only need a potential of 1.63 V to obtain a current density of 10 mA cm−2. Excitingly, the 3D-CPF/FeCoOx-Nanoparticles have exhibited potential applications in supercapacitors. [ABSTRACT FROM AUTHOR]

Here, we successfully synthesized N‐doped carbon nanotubes embedded with nickel‐based nanoparticles on the top (N‐CNTs/E‐NNPs) by directly procedural calcination of melamine and nickel foam at 520 °C, 540 °C and 700 °C in Ar. When applied for oxygen reduction reaction (ORR), the onset potential and half‐wave potential are 0.96 V and 0.86 V in 0.1 M KOH, comparable to that of the commercial 10 wt% Pt/C. Moreover, the hybrids possess higher stability and better methanol tolerance. Additionally, the Tafel slope of N‐CNTs/E‐NNPs is 76 mV dec−1 in 0.1 M KOH, lower than 83 mV dec−1 of the commercial 10 wt% Pt/C, demonstrating a good kinetic process. The remarkable features are mainly ascribed to synergistic enhancement effect from N‐rich doped carbon nanotubes (N‐CNTs) and embedded Ni‐based nanoparticles on the top, promoting mass and electrons transport, enhancing the activity of active sites and making it a promising highly efficient non‐precious metal ORR catalyst. [ABSTRACT FROM AUTHOR]

Palladium (Pd)-based nanomaterials are the emerging class of catalysts with individual physiochemical properties. Unlike traditional catalysts, metallenes showed abundant active sites, large surface area, and high atomic utilization. Based on these benefits, we demonstrate a highly active 2D graphene-like Pd metallene with abundant accessible active sites serving as a highly efficient oxidase mimic. The structure and morphology of Pd metallenezymes were controlled to enhance the catalytic performance and to efficiently utilize all the Pd atoms. Pd metallenezymes with excellent oxidase-like activity were successfully applied for colorimetric-based chromium (VI) (Cr(VI)) detection in a real environment. 3,3',5,5'-Tetramethylbenzidine (TMB) was used as a typical chromogenic substrate catalyzed by Pd metallene to show that blue oxidized TMB (ox TMB) was significantly reduced to colorless TMB by the reducing agent 8-hydroxyquinoline (8-HQ). The reaction process was impressively reversed by the addition of Cr(VI), which interacted with 8-HQ to restore the blue color of TMB. Based on the above results, a facile and effective colorimetric sensing system for the detection of Cr(VI) with a low detection limit of 2.8 nM was developed and could be successfully applied to the detection of Cr(VI) in a real environment. [ABSTRACT FROM AUTHOR]

A fluorescence assay for the detection of 4-nitrophenol (4-NP), α-glucosidase (α-Glu) activity and α-Glu inhibitors (AGIs) is developed based on the inner filter effect (IFE), a flexible and simple signal transfer strategy. In this assay, silicon nanoparticles (Si NPs) synthesized under mild and easily accessible conditions are employed as fluorescent indicators. 4-NP efficaciously quenches the fluorescence of Si NPs through the IFE at a very rapid rate, thus achieving 4-NP detection in a mix-to-read manner, which is suitable for on-site detection. The quenching mechanism has been comprehensively studied and confirmed. More significantly, based on the fact that 4-NP can be generated through α-Glu-catalyzed hydrolysis of 4-nitrophenyl-α- D -glucopyranoside (NPG), the fluorescence detection of α-Glu activity is legitimately achieved by employing NPG as the substrate. The linear ranges for 4-NP and α-Glu activity detection are 0.5–60 μM and 0.5–60 mU mL−1 with low detection limits of 0.074 μM and 0.094 mU mL−1, respectively. This method not only can preciously assay targets in real samples, but is also capable of screening AGIs as drugs as well as assessing their inhibition efficiency. [ABSTRACT FROM AUTHOR]

Review: 119 refs. [ABSTRACT FROM AUTHOR]

Hexavalent chromium is a highly toxic substance, which will pose a serious threat to human life and health and the entire ecosystem. Therefore, it is crucial to establish a simple and rapid detection method for hexavalent chromium. In this work, we fabricated bovine serum albumin–stabilized silver nanocluster (BSA-Ag13 NC) which exhibited photoresponsive oxidase-like activity, catalyzing the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to the blue oxidized state TMB (oxTMB) in a short time. Interestingly, 8-hydroxyquinoline (8-HQ) can significantly inhibit the color reaction of TMB oxidation while Cr(VI) can interact specifically with 8-HQ to restore this chromogenic reaction. Based on the above facts, a colorimetric sensing system for detecting Cr(VI) was developed. The sensing system shows a wide linear range, and good selectivity, with a low detection limit of 2.32 nM. Moreover, this sensing system could be successfully applied to the detection of Cr(VI) in lake water, tap water, and sewage with satisfactory results. [ABSTRACT FROM AUTHOR]

High levels of uric acid (UA) in humans can cause a range of diseases, and traditional assays that rely on uric acid enzymes to break down uric acid are limited by the inherent deficiencies of natural enzymes. Fortunately, the rapid development of nanozymes in recent years is expected to solve the above-mentioned problems. Hence, we used a host–guest strategy to synthesize a platinum nanoparticle confined in a metal–organic framework (Pt NPs@ZIF) that can sensitively detect UA levels in human serum. Unlike previously reported free radical-catalyzed oxidation systems, its unique electron transfer mechanism confers excellent peroxidase-like activity to Pt NPs@ZIF. In addition, UA can selectively inhibit the chromogenic reaction of TMB, thus reducing the absorbance of the system. Therefore, using the peroxidase-like activity of Pt NPs@ZIF and using TMB as a chromogenic substrate, UA can be detected directly without relying on natural enzymes. The results showed a relatively wide detection range (10–1000 μM) and a low detection limit (0.2 μM). Satisfactory results were also obtained for UA in human serum. This study with simple operation and rapid detection offers a promising method for efficiently detecting UA in serum. [ABSTRACT FROM AUTHOR]

A colorimetric sensing method for alkaline phosphatase detection is developed using the self-deposited ultrasmall Ru nanoparticles on carbon nitride as peroxidase-like nanozyme. [Display omitted] Carbon nitride (C 3 N 4) nanosheets are known as peroxidase mimics, but the low activity hinders their further application. Embedding active metal nanoparticles onto the C 3 N 4 nanosheets is expected to break this limitation. Herein, highly dispersed ultrasmall Ru nanoparticles are anchored onto the C 3 N 4 through spontaneous redox reaction. The as-obtained Ru-C 3 N 4 exhibits excellent peroxidase-like activity, which can be further regulated by adjusting the loading of Ru nanoparticles on C 3 N 4. Using Ru-C 3 N 4 as a mimetic peroxidase, a colorimetric sensing method for alkaline phosphatase (ALP) detection is developed based on the inhibitory effect of ascorbic acid produced by hydrolysis of ALP and l -ascorbic acid 2-phosphate (AAP) on the color development reaction of TMB catalyzed by Ru-C 3 N 4. The sensor exhibits wide linear range and low detection limit for the ALP sensing. Finally, the assay is applied to ALP detection in human serum and satisfactory results are obtained, which provides a promising strategy for colorimetric sensing of ALP. [ABSTRACT FROM AUTHOR]

On page 1289, Wei Chen and co‐workers report a method to fabricate graphene‐supported PdAg nanorings. As a potential fuel cell electrocatalyst, the hybrid nanomaterial exhibits excellent catalytic performance for oxygen reduction with the clean product of water. The unique nanostructure of the material with large active surface area, low noble metal loading, and high methanol tolerance is highlighted. [ABSTRACT FROM AUTHOR]

[Display omitted] In this work, we report a novel MoS x /Mn 0.3 Cd 0.7 S composite catalyst that has been designed and fabricated by in situ coupling MoS x nanoclusters with 1D Mn 0.3 Cd 0.7 S nanorods for photocatalytic H 2 production. The catalyst features a 1D nanostructure with MoS x nanoclusters uniformly dispersed along the Mn 0.3 Cd 0.7 S nanorod. It was found that an intimate interface is built between MoS x nanoclusters and Mn 0.3 Cd 0.7 S nanorods thanks to the facile in situ photoreduction route, which contributes to a high-efficiency interfacial charge separation. The resulting MoS x /Mn 0.3 Cd 0.7 S photocatalyst shows a dramatically enhanced visible-light-driven photocatalytic H 2 production activity compared with the control samples, owing to more efficient spatial charge separation as well as enriched active sites. This work is expected to provide an optimized structure model for rational design and constructing novel, inexpensive, efficient and stable cocatalyst/metal sulfide photocatalyst systems for H 2 production. [ABSTRACT FROM AUTHOR]

Review: noble and coinage metals; 318 refs. [ABSTRACT FROM AUTHOR]

The ultrathin porous Pd metallene as oxidase-like nanozyme with excellent catalytic activity was synthesized to applied to the AA related biosensing analysis, including the total antioxidant capacity (TAC) assessment of several vitamin C-contained tablets and beverages and ALP activity assay with accurate selectivity and sensitivity. [Display omitted] Pd-based nanomaterials have shown great promise as promising mimic enzymes, but traditional catalysts can only expose only part of the active sites, resulting in low atomic utilization. Herein, we demonstrated that ultrathin Pd metallene with abundant accessible active sites could be served as highly efficient oxidase mimics. Due to their ultrathin porous structure, nearly all the Pd atoms of the Pd metallenezymes could be efficiently utilized during the catalytic process. By using the 3,3′,5,5′-tetramethyl benzidine (TMB) as a typical chromogenic substrate, the Pd metallenezymes with excellent oxidase-like activity are successfully applied for some colorimetric-based analysis applications. Benefiting from the sensitive Pd metallene/TMB detection system, the TAC of some commercial beverages and vitamin C chewable pieces are proved to meet the description and the activity of alkaline phosphatase (ALP) was successfully detected in 0–20 U/L range, achieving a lowest detect limit of 0.41 U/L. This work provides not only one kind of novel nanozymes, but also an effective strategy to maximize the atom utilization as enzyme mimics. [ABSTRACT FROM AUTHOR]

• CsPO 3 and Cs 4 Ba(PO 3) 6 of P-Cs-Ba-Si catalyst provide stable acid-base sites. • Acidity/alkalinity of catalyst regulate product distribution of MEA dehydration. • Acidic sites of catalyst enhance conversion of MEA to ethyleneimine. • Forming ethyleneimine requires synergistic catalysis of weak acid and weak base. • P-Cs-Ba-Si catalysts exhibits good stability during continuous operation for 240 h. The dehydration of monoethanolamine (MEA) is an important chemical reaction for the synthesis of nitrogen-containing fine chemicals, but the reactive hydroxyl and amine functional groups of the MEA molecule make it difficult to selectively obtain the specified products. In this study, the basic metal barium and cesium were introduced on the SiO 2 support by sequential impregnation method, and the support and catalyst were modified by phosphoric acid (phosphate) to form CsPO 3 , Cs 4 Ba(PO 3) 6 and other compounds to prepare P-Cs-Ba-Si composite oxide solid base catalyst. Varying the loading of cesium showed that the highly dispersed CsPO 3 and Cs 4 Ba(PO 3) 6 produced stable acid and alkali active centers on the catalyst surface, thus achieving effective regulation of the dehydration reaction path of MEA. The acidic sites of the catalysts improved the intermolecular dehydration of MEA, while the basic sites improved the intramolecular dehydration of MEA. The high selectivity of ethyleneimine (EI) depended on the synergistic effect of the weakly acidic/weakly basic sites of the catalysts. In the fixed bed continuous reaction system, the conversion of MEA reached 60.8 % with the EI selectivity of 82.7 %, and 240 h of continuous operation showed good stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Tyramine is an important index of food freshness degree, and tyrosinase that can specifically oxidized monophenolamine to catecholamine plays a crucial part in the occurrence and development of melanin-related skin diseases. Therefore, it is crucial to develop sensitive and efficient methods for the detection of tyramine and tyrosinase. In this work, encouraged by tyrosinase-triggered specific oxidation of tyramine to dopamine and the unique fluorescent reaction between dopamine and amino silane, we have developed a one-step synthetic strategy of silicon containing nanoparticles (Si CNPs) for "turn-on" detection of tyramine and tyrosinase. The Si CNPs formed with thoroughly studied mechanism exhibit uniform structure and robust yellow-green fluorescence. The low detection limits for tyramine (1.87 μM) and tyrosinase (0.0029 U/mL) demonstrate admirable sensitivity outstripping most methods. The proposed assay achieves satisfactory results in the determination of tyramine and tyrosinase activity in real samples. Furthermore, we leverage this new fluorescent assay to enable the fabrication of an "AND" Boolean logic gate. The entire process can be completed at easily available temperature and pressure with rapid response, convenient operation and visual observation. This fluorescent assay featured with excellent sensitivity, selectivity and stability has considerable prospects in the application of biosensors and disease diagnosis. Fluorescent "AND" logic gate for detection of tyramine and tyrosinase activity is constructed based on the synthesis of Si-containing nanoparticles. [Display omitted] • Si CNPs as fluorescent indicators are in-situ formed under mild conditions. • Amine type determines and amine number/silicon enhance the fluorescence. • Detection of tyramine is achieved by using tyrosinase as a recognition element. • Fluorescent "AND" logic gate is fabricated using tyramine and tyrosinase as inputs. • The system has been successfully applied to the actual sample detection. [ABSTRACT FROM AUTHOR]

The neurotransmitter dopamine (DA) is associated with many physiological and pathological processes, so the importance of low detection limits and high sensitivity analysis cannot be overstated, especially for early disease detection. Here, 2 M NaOH aqueous solution is used to precipitate metal ions in an ethanol solution containing carbon black (CB), and then nanocomposite catalysts (Na x Ti11.5MoVO x /C-40 (40 denoted as 40 mg CB)) were obtained by calcining the precipitation. When used for DA detection, Na x VO x acts as the main active site for electrochemical oxidation of DA and Na x Ti11.5MoO x plays a role in facilitating the binding of DA to the active site and stabilizing the active site. The Na x Ti11.5MoVO x /C-40 electrochemical biosensor has a limit of detection (LOD) of 0.003 μM with a linear range of 0.005–51.665 μM for DA. This sensor can be used to sensitively identify the concentration of DA in human blood and urine. Catalysts containing varying amounts of CB exhibit diverse electron transfer rates, and surprisingly, we found that the appropriate electron transfer rate is optimal for the detection of low concentrations of DA. Because the performance of the electrochemical biosensors is affected by both the activity of the catalysts and the accuracy of the electrochemical testing instrumentation. To better explain this phenomenon, we propose the concept of resolution (Rn) and present the formula to derive it, offering a new approach to evaluating the performance of electrochemical biosensors. Na x Ti11.5MoVO x /C-40 material as dopamine sensing catalyst : In this work, Na x VO x acts as the main active site for electrochemical oxidation of DA and Na x Ti11.5MoVO x plays a role in facilitating the binding of DA to the active site and stabilizing the active site. The performance of the electrochemical biosensors is affected by both the activity of the catalysts and the accuracy of the electrochemical testing instrumentation. To better explain this phenomenon, we propose the concept of resolution (Rn). [Display omitted] • Na x Ti11.5MoVO x /C-40 material was used for electrochemical detection of dopamine. • Na x VO x is the active site and Na x Ti11.5MoO x stabilises the catalytic site. • Carbon black content modulates electron transfer rate. • Concept of resolution was proposed for better evaluation of sensor performance. [ABSTRACT FROM AUTHOR]

Enzyme like activity of Pd metallene was tuned by hydrothermally treating and intercalating N-atom to obtain N-Pdene with expand lattice and changed electronic structure. The atomically modified N-Pdene was proved to be promising enzyme mimic with greater oxidase-like activity compared to Pd metallene. [Display omitted] • Catalytic activity of nanozyme is enhanced by morphology regulation at nanoscales. • The N-Pdene nanozyme was evaluated as enzyme mimics for colorimetric analysis. • Paper-based smartphone sensor was designed for quantitative analysis of glyphosate. • Limit of detection was found to be superior than most of previous studies. Pd-based nanomaterials as enzyme mimics have drawn extensive research interest over the past years. Modulating lattice strain, porosity and electronic structure of them could provide a great opportunity to enhance their enzyme-like performance. Herein, we adopted an atomic scale reconstruction strategy to prepare N atom-intercalated Pd metallene (N-Pdene) with expanded lattice and increased crystallinity for the colorimetric sensing of ascorbic acid (AA), total anti-oxidant capacity (TAC), acid phosphatase (ACP) and glyphosate detection. Various experimental analysis revealed that N-Pdene could serve as promising oxidase mimics for detecting glyphosate in actual environment. Based on the fact, a paper-based N-Pdene/smartphone sensing platform was also successfully developed to analyze the concentration of organophosphorus pesticides (OPs) in food samples with low detection limit of 0.27 µM. Compared to previous reports on glyphosate detection, the designed paper-based sensor is economic, simple, safe and easy, providing efficient and accurate quantification of OPs in practical applications. [ABSTRACT FROM AUTHOR]

A convenient and sensitive antioxidant assay with high performance is essential for assessing food quality and monitoring the oxidative stress level of biological matrices. Although coordination polymer nanoparticles (CPNs)-based nanozymes have emerged as candidates in the analytical field, strategies to improve the catalytic activity of CPNs have been scarcely revealed and studied. Herein, we demonstrate a manganese (Mn) doping strategy to enhance the peroxidase-mimetic activity of Fe-based CPNs. By tuning the Mn doping amounts and selecting 2,5-dihydroxyterephthalic acid (H4DHTP) as ligands, the produced nanozymes in amorphous state followed the catalytic activity order of Fe5Mn-DHTP > Fe8Mn-DHTP > Fe2Mn-DHTP > Fe-DHTP > Mn-DHTP. Ulteriorly, benefitting from the best catalytic performance and definite catalytic mechanism of Fe5Mn-DHTP, versatile colorimetric assays for ultrasensitive detection of one exogenous antioxidant (ascorbic acid, AA) and two endogenous antioxidants (glutathione, GSH; cysteine, Cys) have been deftly devised based on the inhibition of the 3,3′,5,5′-tetramethylbenzidine chromogenic reaction in presence of H2O2. It was found that mercaptan (GSH and Cys) and AA exhibited different inhibition mechanisms. Practically, such a colorimetric assay was viable to determine the total antioxidant capacity of drugs and foods with desirable results. This work proposes a feasible strategy for embellishing CPN nanozymes used for designing sensitive and convenient assays for various antioxidants based on an explicit detection mechanism. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Highly dispersed ultrasmall ruthenium nanoparticles with a clean surface are deposited onto graphitic carbon nitride (C3N4‐Ru) through spontaneous redox reaction between the C3N4 sheets and Ru salt without the use of any reductant. The as‐prepared C3N4‐Ru exhibits distinct peroxidase‐like activity. A nanozyme based method is successfully developed for detecting the H2O2 generated in‐situ by the two‐electron oxygen reduction strategy. The C3N4‐Ru nanozyme can realize the detection of H2O2 with a wide linear range and a low detection limit. The testing results are also compared with the conventional modified titration method, and show greater possibility for the practical detection of H2O2 produced via the electrochemical oxygen reduction for its higher selectivity. [ABSTRACT FROM AUTHOR]

A convenient and sensitive colorimetric assay for acetylcholinesterase (AChE) and its inhibitor has been designed based on the oxidase-like activity of {100}-faceted Pd square nanoplates which are grown in situ on reduced graphene oxide (PdSP@rGO). PdSP@rGO can effectively catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) without the assistance of H2O2 to generate blue oxidized TMB (oxTMB) with a characteristic absorption peak at 652 nm. In the presence of AChE, acetylthiocholine (ATCh), a typical AChE substrate, is hydrolyzed to thiocholine (TCh). The generated TCh can effectively inhibit the PdSP@rGO-triggered chromogenic reaction of TMB via cheating with Pd, resulting in color fading and decrease in absorbance. Thus, a sensitive probe for AChE activity is constructed with a working range of 0.25–5 mU mL−1 and a limit of detection (LOD) of 0.0625 mU mL−1. Furthermore, because of the inhibition effect of tacrine on AChE, tacrine is also detected through the colorimetric AChE assay system within the concentrations range 0.025–0.4 μM with a LOD of 0.00229 μM. Hence, a rapid and facile colorimetric procedure to sensitively detect AChE and its inhibitor can be anticipated through modulating the oxidase-like activity of PdSP@rGO. [ABSTRACT FROM AUTHOR]

Enzyme-mimetic properties of nanomaterials can be efficiently tuned by controlling their size, composition, and structure. Here, ultrathin PdCu alloy nanosheet–assembled three-dimensional (3D) nanoflowers (Pd1Cux NAFs) with tunable surface composition are obtained via a generalized strategy. In presence of H2O2, the as-synthesized Pd1Cux NAFs can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to the oxidized form of TMB (oxTMB) with a characteristic absorption peak at 652 nm. Interestingly, Pd1Cux NAFs show obviously composition-dependent peroxidase-like catalytic activities because of the synergistic interaction of nanoalloy. Additionally, different from 2D Pd nanosheets, the distinctive 3D superstructures are featured with rich approachable sites and proper layer spacing, which are in favor of fast mass transport and electron transfers during the catalytic process. Among the studied Pd1Cux NAFs, the Pd1Cu1.7 NAFs show the highest enzyme-like activities and can be successfully applied for the colorimetric detection of glucose with a low detection limit of 2.93 ± 0.53 μM. This work provides an efficient avenue to fabricate PdCu NAF nanozymes in biosensing toward glucose detection. [ABSTRACT FROM AUTHOR]

In this work, a novel convenient colorimetric method for sensitive detection of thiocyanate (SCN−) has been developed based on its suppression of the oxidase-like activity of palladium square nanoplates on reduced graphene oxide (Pd SP@rGO). SCN− can be adsorbed onto the surface of Pd SP@rGO via binding with Pd atoms and blocks the active sites that mimic oxidase, thus inhibiting the corresponding chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine, which has been comprehensively revealed by the UV-vis spectra and X-ray photoelectron spectra. The color fading exhibits SCN− concentration-dependent behavior and can be easily recorded by either UV-vis spectroscopy or naked-eye observation. Therefore, both quantitative detection via measurement of the decrease in absorbance and visual detection of SCN− can be achieved. Owing to the intrinsic amplification of signals by the oxidase-like activity of Pd SP@rGO without resorting to unstable and destructive H2O2, this assay is straightforward, robust and sensitive enough for the detection of SCN− in real samples. Furthermore, an "INH" logic gate is rationally constructed based on the proposed colorimetric SCN− sensor. [ABSTRACT FROM AUTHOR]

The facile detection of total antioxidant capacity (TAC) is limited by in-situ analysis, because it usually requires complex laboratory equipments. Here, a colorimetric assay for TAC detection is developed based on the peroxidase-like activity of iron-doped carbon nitride (Fe/NC) and the smartphone platform. The peroxidase-like activity of carbon nitride is greatly improved by the introduction of Fe atoms, and the active sites turn to Fe-N x coordination groups in the Fe/NC. The inhibition mechanism of the chromogenic reaction for different kinds of antioxidants is also studied. The colorimetric assay is fabricated by the relationship of absorbance-color-antioxidant content and applied successfully to the TAC detection of several fruit juicesand commercial beverages. This work not only provides a promising approach for convenient in-situ TAC assay without the use of large instruments, but also expands the application of nanozymes in nutritional value assessment of foods. The Fe atom-containing carbon nitride shows greatly improved peroxidase-like activity and can be conveniently used for the on-site smartphone-based colorimetric assay of total antioxidant capacity of foods. [Display omitted] • The peroxidase-like activity of C 3 N 4 is greatly improved by Fe atom doping. • The newly formed Fe-N x serve as the main active sites in the Fe/NC nanozyme. • The antioxidants content are tested and different mechanisms are proposed for AA or GSH/Cys. • RGB model of smartphone can be used for on-site colorimetric assay of TAC in food samples. [ABSTRACT FROM AUTHOR]

In this paper, the (Gd,Y)AG:Mn2+,Ce3+ phosphors were synthesized by high temperature solid-state reaction method. The lattice stabilization, microstructure and fluorescence properties were systematically investigated via XRD, FE-SEM, PLE/PL spectra and fluorescence decay analysis, respectively. Under the excitation of 461 nm, two emission peaks appear at 585 nm and 740 nm, which can be assigned to the transition 5 d →4 f of Ce3+ and 4 T 1 →6 A 1 of Mn2+. The color of (Gd,Y)AG:Mn2+,Ce3+ phosphor can be adjusted from yellow to orange-red by changing the doping concentration of Mn2+, and the quenching mechanism of Mn2+ in (Gd,Y)AG: Mn2+,Ce3+ system is attributed to the electric multipole interactions. With the increase of Mn2+ concentrations, the fluorescence lifetime reduced from 152 ns to 9 ns, and the energy transfer efficiency of Ce3+→Mn2+ can be calculated to increase from 35.32% to 95.89%. The underlying mechanisms were thoroughly investigated and elucidated. Furthermore, the thermal stability of (Gd,Y)AG:Mn2+,Ce3+ phosphor systematically studied. The excellent fluorescence properties and high stability of (Gd,Y)AG:Mn2+,Ce3+ phosphor is expected to be widely used in lighting and display areas. • The crystal structure of Gd 3 Al 5 O 12 garnet has been stabilized via doping with Y3+. • The emission color can be controlled using the Mn2+-Ce3+ energy transfer. • The energy transfer mechanism between Mn2+ and Ce3+ is deeply researched. [ABSTRACT FROM AUTHOR]

As one of the highly crystalline porous materials, metal–organic frameworks (MOFs) have drawn immense attention due to their diverse structures and a wide variety of applications. In this study, [In3(ipbp)2(μ2-OH)(μ2-O)3] (1) that has a three-dimensional framework, including two types of cages with cuboctahedra and trigonal antiprism configurations, has been successfully synthesized based on the zwitterionic ligand 1-(3,5-dicarboxyphenyl)-4,4′-bipyridinium bromide (H2(ipbp)Br). Strikingly, a relatively rare trapeziform metal layer consisting of In3+, μ2-OH, μ2-O, carboxyl, and nitrogen from the ligand appears in the structure of 1. Benefitting from the formation of the ipbp radicals under UV light irradiation, compound 1 exhibits photochromic property that can transform the color from yellow to green. Moreover, it possesses commendable Cr(VI) removal capacity with the maximum adsorption amount of 74.4 mg·g−1 due to the surface electrostatic interaction between the crystal surface and Cr(VI) in the aqueous system. This work will promote the design of functional MOFs that show potential applications in UV light detection and removal of oxyanions. [ABSTRACT FROM AUTHOR]

Core-shell palladium cube@CeO2 (Pd cube@CeO2) nanoparticles are shown to display oxidase-like activity. This is exploited in a method for determination of the activity of alkaline phosphatase (ALP). The Pd cube@CeO2 nanoparticles were thermally synthesized from Ce(NO3)3, L-arginine and preformed Pd cube seeds in water. The Pd cube@CeO2 nanoparticles catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by oxygen. This results in the formation of oxidized TMB (oxTMB) with an absorption peak at 652 nm. Ascorbic acid (AA) is generated from the hydrolysis of L-ascorbic acid 2-phosphate (AAP) catalyzed by ALP. It can reduce oxTMB to TMB, and this results in a decrease of the absorbance. The method allows for quantitative determination of the activity of ALP in the range from 0.1 to 4.0 U·L−1 and with a detection limit down to 0.07 U·L−1. Endowed with high sensitivity and selectivity, the assay can quantify ALP activity in biological system with satisfactory results. [ABSTRACT FROM AUTHOR]

Thiophenol (PhSH) is toxic to the environment and biological systems although it is an indispensable material in the synthetic processes of chemical products. In this work, we designed and synthesized a malonitrile-based colorimetric and deep-red emission fluorescent dosimeter specifically for thiophenol detection by switching on the intramolecular charge transfer process. The 2,4-dinitrobenzene moiety in the probe could be cleaved by thiophenol, which led to strong deep-red fluorescence increase at 645 nm (50-fold) with a low detection limit of 9 nM. The maximum plateau of emission intensity was reached in about 30 min after the addition of thiophenol. Simultaneously, the presence of thiophenol could result in a prominent color change from orange to blue. Furthermore, the dosimeter could quantitatively sense thiophenol spiked in water samples and successfully visualize thiophenol in living SH-SY5Y cells. [ABSTRACT FROM AUTHOR]

Nowadays, fabricating simple and efficient pesticide detection methods become a research focus due to the great threat pesticide residues posed to human health and environment. Herein, we constructed a high-efficiency and sensitive colorimetric detection platform for malathion detection based on polydopamine-dressed Pd nanocubes (PDA-Pd/NCs). The Pd/NCs coated with PDA exhibited excellent oxidase-like activity, which was attributed to the substrates accumulation and accelerated electron transfer induced by PDA. What's more, we successfully achieved sensitive detection of acid phosphatase (ACP) using 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate, relying on the satisfactory oxidase activity from PDA-Pd/NCs. However, the addition of malathion could inhibit the activity of ACP and limit the production of medium AA. Therefore, we constructed a colorimetric assay for malathion based on PDA-Pd/NCs + TMB + ACP system. The wide linear range (0–8 μM) and low detection limit (0.023 μM) indicate excellent analytical performance, which is superior to most malathion analysis methods previously reported. This work not only provides a new idea for dopamine coated nano-enzyme to improve its catalytic activity, but also creates a new tactics for the detection of pesticides such as malathion. [Display omitted] • PDA-Pd/NCs prepared in this text exhibit excellent oxidase-like activity. • Proving that dopamine dramatically improves the catalytic activity of nanozymes. • Catalytic and enhancement mechanisms were analyzed in detail. • A colorimetric assay for ACP and malathion was constructed. [ABSTRACT FROM AUTHOR]

• A deep-red emission fluorescent probe (DRP-Cys) for Cys based on a hemicyanine scaffold was developed. • A tailed malononitrile group could chromatically shift excitation/emission wavelengths to the deep-red emission range. • The probe could detect Cys with an ultrafast response time of about 1 min and a low limit of detection of 10 nM • The probe was also successfully applied for visualizing endogenous Cys in living HeLa cells and mice. It is still challenging how to selectively and sensitively detect cysteine in living systems which plays crucial roles in many physiological and biological processes. Here, we developed a deep-red emission fluorescent probe (DRP-Cys) for Cys based on a hemicyanine scaffold. A tailed malononitrile group could chromatically shift excitation/emission wavelengths to avoid the limitations such as photo-damage or auto-fluorescence in biological samples. Compared with other amino acids, Cys could trigger the Michael addition reaction to release a dramatic enhancement in fluorescence centering at around 645 nm in DMSO aqueous solution under physiological conditions with an ultrafast response time of about 1 min and a low limit of detection of 10 nM which significantly benefited from the introduction of the malononitrile moiety. The probe was also successfully applied for visualizing endogenous Cys in living HeLa cells and mice with low cytotoxicity and good cell-membrane permeability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Furan can be converted to methyl levulinate in dimethoxymethane. • 2-methoxymethylfuran is an intermediate formed via electrophilic substitution. • Methanol in reaction medium suppresses the polymerisation to some extent. • Dimethoxymethane can react with methyl levulinate, which is a key side reaction. • DRIFTS study shows structures of coke from furan or methyl levulinate is different. Abstract This study developed a method for the direct conversion of the biomass-derived furan to the methyl levulinate, a platform molecule, via acid-catalysis in dimethoxymethane/methanol. Dimethoxymethane acted as the electrophile to transform furan into 2-methoxymethyl-furan (the ether of furfuryl alcohol). The following step of acid catalysis converted 2-methoxymethyl-furan to methyl levulinate. No hydrogenation catalyst or hydrogen was used in the process, which was the new reaction route for the conversion of furan to the value-added levulinic acid/ester. Polymerization was the main challenge in this reaction route, which could be suppressed but to some limited extent with methanol as a co-reactant/solvent in the reaction medium. The polymerization of furan and cross-polymerization reactions between dimethoxymethane (the reactant) and methyl levulinate (the targeting product) via Aldol condensation were the important reasons for the decreased production of methyl levulinate. The DRIFTS and TG-MS studies showed that the coke formed from the polymerization of furan contained more aliphatic structure, more carboxylic groups and methyl groups, while the coke from methyl levulinate contained more carbonyl groups and more conjugated π-bonds, projecting the structural difference of furan and methyl levulinate. [ABSTRACT FROM AUTHOR]

Hemin, the most common biological iron form, serves many biological functions. However, studies on hemin detection are scarce. As an unusual natural peroxide, artemisinin is quite stable in the presence of common species. While, it can decompose to generate superoxide radicals in the presence of hemin. And the as-obtained superoxide radicals can effectively oxidize thiamine to form fluorescent thiochrome. Inspired by this, a simple and novel fluorescent assay for hemin detection based on artemisin-thiamine is developed. Based on the linear relationship between the fluorescence intensity and concentration of hemin, the developed artemisinin-thiamine assay can be utilized for sensitive detection of hemin in the concentration range of 2.0–300.0 nM with a detection limit of 0.68 nM. Moreover, this assay shows high selectivity over other cations and biomolecules. Besides, hemin can be detected in serum samples with satisfactory results, which demonstrates its great potential for real sample analysis. The designed assay is free of any fluorescent nanomaterials or probes by just mixing these reagents together, and all the detection processes is performed within 20 min. Therefore, it can offer a simple, highly sensitive and selective sensing platform for fluorescence detection of hemin. [ABSTRACT FROM AUTHOR]

In this work, we propose a fluorescence method for the simultaneous detection of glutathione (GSH) and histidine (His) based on the Cu(ii)-thiamine (Cu(ii)-TH) system. It is well established that non-fluorescent thiamine (TH) can be oxidized by Cu(ii) to generate fluorescent thiochrome (TC) under alkaline conditions. The introduction of GSH and His can inhibit the oxidation of TH by Cu(ii) due to the strong affinity between Cu(ii) and GSH or His. With this strategy, the detection limit for GSH and His is 10.5 nM and 26.4 nM, respectively. The developed method shows several obvious advantages: (1) simplicity in design and operation without the utilization of fluorescent nanomaterials or probes; (2) time-saving detection process since all the detection process is completed within 15 min; (3) cost-effectiveness by using TH as the fluorescent substrate; and (4) higher sensitivity and good selectivity. Therefore, it shows great potential in biosensing fields. [ABSTRACT FROM AUTHOR]

Alkaline phosphatase (ALP) is a significant biomarker for diagnostics. Simple, selective and sensitive detection of ALP activity is thus of critical importance. In this study, an artful fluorescence assay for ALP is proposed based on adenosine triphosphate (ATP) hydrolysis-triggered disassociation and fluorescence quenching of cerium coordination polymer nanoparticles (CPNs). ATP, a recognized natural substrate of phosphatase, can serve as a superb “antenna” to sensitize the luminescence of Ce3+ with the aid of tris(hydroxymethyl) aminomethane (Tris), forming Ce3+–ATP–Tris CPNs. In the presence of ALP, ATP will be catalytically converted into adenosine and inorganic orthophosphate, however neither of them can sensitize Ce3+ in alkaline media. As a result, the obtained CPNs are disassociated, inducing the quenching of the fluorescence. On this basis, a straightforward fluorescence assay for ALP activity is rationally developed. The fluorescence quenching efficiency shows a linear relationship for ALP within the activity range from 0.1 to 10 mU mL−1 with a detection limit of 0.09 mU mL−1 under the optimal experimental conditions. Moreover, this facile yet effective fluorescence method featured simplicity, cost-effectiveness, high sensitivity and high selectivity and can be successfully utilized for the quantitative detection of ALP in human serum samples. [ABSTRACT FROM AUTHOR]

Zn2+ plays fundamental roles in cellular metabolism and apoptosis, as well as neurotransmission. However, how to fast detect Zn2+ in biology is still challenging and meaningful. In this study, we rationally synthesized a simple OFF–ON fluorescent probe for fast detection of Zn2+ based on intramolecular charge transfer and chelation-enhanced fluorescence. Addition of Zn2+ into the probe induced a significant fluorescence enhancement with a bathochromic shift of 55 nm. Moreover, the probe demonstrated excellent sensitivity (detection limit = 0.072 μM) and outstanding selectivity toward Zn2+ and an ultra-fast response rate of two seconds. The recognition mechanism of the probe toward Zn2+ was fully confirmed by HRMS and 1H NMR spectra, as well as TDDFT calculations. Furthermore, the probe could rapidly visualize Zn2+ in living cells and zebrafish models in bioimaging experiments with low cytotoxicity and good biocompatibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • The coating film of [(C 2 H 5) 2 NH 2 ] 2 NiBr 4 @SiO 2 with VO 2 is prepared for the first time; • The Δ T sol of composite film is 2.1 times better than that of single VO 2 film; • Evident thermoresponsive color change from brown to green as temperature rises; • DFT calculations prove the key role of N H...X H-bond on the stability of the complex; • SiO 2 shell effectively inhibits the deliquescence of [(C 2 H 5) 2 NH 2 ] 2 NiBr 4 complex. Vanadium dioxide (VO 2) has attracted consideration because of its thermochromic performance in smart windows. However, the practical applications of VO 2 -based smart windows are seriously hindered by their low luminous transmittance (T lum), poor solar modulation efficiency (Δ T sol), and the monotonous "brown-yellowish" color. This study aims at developing a newly reported metal complex [(C 2 H 5) 2 NH 2 ] 2 NiBr 4 and its core–shell structure of [(C 2 H 5) 2 NH 2 ] 2 NiBr 4 @SiO 2 , combined with the thermochromic VO 2 to enhance optical performance (T lum and Δ T sol). Density Functional Theory (DFT) calculations indicate that the as-obtained metal complex is thermodynamically stable, and the weaker N H...Br hydrogen bond makes the complex possesses a lower phase transition temperature (T C = 57.6 °C) than the reported [(C 2 H 5) 2 NH 2 ] 2 NiCl 4 (T C = 75.4 °C). In addition, it is found that the SiO 2 shell can effectively inhibit the deliquescence of the [(C 2 H 5) 2 NH 2 ] 2 NiBr 4 complex, and DFT calculations reveal that the oxygen of SiO 2 can bond with the hydrogen of ammonium, thus the water molecules in the air cannot continue to react with the complex. Interestingly, the combination of [(C 2 H 5) 2 NH 2 ] 2 NiBr 4 @SiO 2 /Polystyrene film with VO 2 /Polyvinylbutyral film demonstrates exemplary solar modulation abilities (T lum,low = 52.9 %, T lum,high = 37.3 %, Δ T sol = 25.7 %, Haze = 26.5 %), 2.1 times better than that of VO 2 /Polyvinylbutyral film (T lum,low = 55.9 %, T lum,high = 54.2 %, Δ T sol = 12.4 %, Haze = 17.2 %). Moreover, the color of VO 2 -based film changes from light-brown (at low temperature) to green (at high temperature). [ABSTRACT FROM AUTHOR]

we have demonstrated that bovine serum albumin (BSA) templated MnO 2 nanosheets (NSs) are robust oxidase mimics and oxidants that can switch o -phenylenediamine (OPD)-based fluorescent reactions in presence of ascorbic acid (AA) under neutral conditions. Finally, we successfully used this approach to evaluate the activity of α-Glu and the inhibitory efficiency of its inhibitor voglibose. [Display omitted] • There are two in situ fluorescence signals from the same precursor. • In the presence of AA, the fluorescence reaction based on OPD was switched. • This sensor has been applied to the determination of activity of α-Glucosidase. • The inhibition efficiency of inhibitors of α-Glucosidase was evaluated. Determination of α-glucosidase (α-Glu) activity and screening its inhibitors have great significance in disease diagnosis and biomedical research. In contrast to the flourishing development in fluorescent α-Glu assays, very few fluorescent ratiometric methods have been designed, especially the simplified one with two in-situ formed fluorescent signals derived from the same precursor. In this work, we have demonstrated that bovine serum albumin (BSA) templated MnO 2 nanosheets (NSs) are robust oxidase mimics and oxidants that can switch o -phenylenediamine (OPD)-based fluorescent reactions in presence of ascorbic acid (AA). MnO 2 NSs exert oxidase-like effects to simulate the oxidation of non-fluorescent OPD to orange fluorescent 2,3-diaminophenol (DAP) with fluorescence emission at 565 nm. In the presence of AA, MnO 2 NSs as oxidants can effectively promote the dehydrogenation of AA and thus facilitate the fluorescent reaction between AA and OPD to generates fluorescent probe with emission at 425 nm. At the same time, generation of DAP is hindered due to OPD consuming and MnO 2 NSs decomposition. AA-induced reversed fluorescence response at 425 and 565 nm lays the foundation for fluorescent ratiometric detection of α-Glu by using 2-O-α- d -glucopyranose- l -ascorbic acid (AAG) as substrate. This α-Glu assay features with the merits of strong anti-interference ability, easy operation and time-saving, and can be further used for inhibitor screening and inhibition efficiency evaluation. [ABSTRACT FROM AUTHOR]

• A dual-readout signals (colorimetric and fluorescent) ALP sensor is developed. • Further construction of chlorpyrifos assay owing to its inhibition effect to ALP. • No additional nanomaterials are needed. • The dual signals reporting can prove each other. Chlorpyrifos is widely used in agriculture but their residue is a threat to food safety and human health. The study aims to find an accurate and sensitive detection method for chlorpyrifos. Silicon-based nanoparticles (Si BNPs) with fluorescent and colorimetric dual signals are in-situ formed through the alkaline phosphatase (ALP) triggered reaction. The dual-mode sensor for chlorpyrifos can be facilely fabricated because the existence of chlorpyrifos would inhibit the activity of ALP and thus affect the production of Si BNPs. Under optimal condition, the fluorescence intensity and absorption intensity linearly correlate with the logarithm of chlorpyrifos concentration over wide range of 0.5–5000 ng/mL and 1–5000 ng/mL with low detection limit by the two detection modes, respectively. The dual-mode sensor is further applied to the detection of spiked chlorpyrifos in practical samples with satisfactory recovery, rendering it as a promising candidate to current methodologies for the simple and accurate detection of chlorpyrifos. [ABSTRACT FROM AUTHOR]

• SA-Co/NC is obtained by wet chemical method combined pyrolysis process. • Theoretical calculations and experiments prove oxidase-like activity of SA-Co/NC. • A time-based visualization scheme for TAC detection is proposed. • TAC monitoring of skin care products is achieved by smartphone platform. Reactive oxygen species (ROS) are an important cause of oxidative skin aging and can be removed by adding some antioxidant ingredients to skin care products. However, total antioxidant capacity (TAC) assays generally require sophisticated laboratory equipment, which greatly limits their daily application. Fortunately, the adoption and development of portable smartphone platforms could promises to solve this challenge. Herein, we report a cobalt single atom-based portable smartphone platform which can realize dynamic-time visualization monitoring the TAC of skin care product. Theoretical calculations and specific experimental results show that single-atom cobalt catalysts (SA-Co/NC) present excellent oxidase-like activity and can effectively convert dissolved oxygen into strongly oxidizing reactive oxygen species. More interestingly, based on the unique sacrificial inhibition catalytic mechanism of ascorbic acid (AA), it can be combined with a portable smartphone platform to detect the TAC of real samples by fitting a time-color-concentration standard curve and recording the change of color RGB values during the reaction. Compared with the traditional scheme, this scheme is convenient, low cost, and can realize visual detection of mobile terminals. This work provides a new scheme for miniaturization, convenience and home-based of TAC detection. [ABSTRACT FROM AUTHOR]

Oral non-prostanoid prostacyclin receptor agonists therapies have been recommended for pulmonary arterial hypertension in many countries. We aimed to evaluate the specific impact of non-prostanoid prostacyclin receptor agonists on pulmonary hypertension and to explore the influence of study characteristics on results. PubMed, Embase, and ClinicalTrials.gov were systematically searched from inception to July 12, 2022. Randomized controlled trials comparing non-prostanoid prostacyclin receptor agonists administration with placebo for treating pulmonary hypertension were included. Two researchers independently selected eligible studies, assessed the bias risk and extracted related data. RevMan5.1 was used for performing the statistical analysis and the assessment of bias risk of the enrolled studies. PROSPERO registered number CRD42022304172. Seven trials involving 1727 patients were included. Pooled analyses indicated non-prostanoid prostacyclin receptor agonists significantly reduced clinical worsening events (risk ratio [RR], 0.63; 95% confidence interval [CI], 0.54 to 0.74), increased 6-min walk distance (mean difference [MD], 10 m; 95% CI, 3–17 m), decreased pulmonary vascular resistance (MD, −121 dyn s/cm5; 95% CI, −172 to −69 dyn s/cm5) and increased cardiac index (MD, 0.38 L/min/m2; 95% CI, 0.26–0.50 L/min/m2) compared with the control. No significant differences in all-cause mortality (RR, 0.86; 95% CI, 0.26 to 2.78), NYHA/WHO functional class (RR, 1.16; 95% CI, 0.61 to 2.18), mean pulmonary artery pressure (MD, −0.88 mmHg; 95% CI, −2.20 to 0.44 mmHg), right atrial pressure (MD, 0.66 mmHg; 95% CI, −0.59 to 1.90 mmHg) and total adverse events (RR, 1.05; 95% CI, 0.99 to 1.10) were found between non-prostanoid prostacyclin receptor agonists group and control group. Non-prostanoid prostacyclin receptor agonists treatment exerted benefits on clinical worsening, pulmonary vascular resistance, and cardiac index in pulmonary hypertension patients, without increasing the incidence of total adverse events. • Non-prostanoid prostacyclin receptor agonists significantly reduce clinical worsening events. • Non-prostanoid prostacyclin receptor agonists significantly increase cardiac index and decrease PVR. • Non-prostanoid prostacyclin receptor agonists are safe and well-tolerated. [ABSTRACT FROM AUTHOR]

The C3 selectivity of carbon-supported Au nanoparticles for glycerol electro-oxidation was significantly enhanced by the interaction of Au with electro-deposited Cu species. Notably, the C3 selectivity of supported Au nanoparticles doubled after 90 min of Cu electro-deposition at +0.015 V. This result was obtained if glycerol electro-oxidation was performed at +0.1 V for 2 h. The most selective catalysts contained an Au+ species that was generated by an interaction between Au and electro-deposited Cu2O. The presence of Au+ increased the selectivity to glycerate and tartronate and suppressed C−C bond cleavage to glycolate and formate simultaneously. [ABSTRACT FROM AUTHOR]

• Pt single-atom nanozyme (SA-Pt/CN) with oxidase-like activity is prepared. • Catalytic mechanism is discussed in detail. • SA-Pt/CN can distinguish hydroquinone from other phenolics. • Colorimetric α-glucosidase assay is designed using α-Arbutin as substrate. • Colorimetric "NAND" logic gate is constructed. Highly-efficient nanozymes and suitable substrates are the two most important breakthroughs for the construction of novel nanozyme-based enzyme activity assays with good analytical performance. In this work, we demonstrated that the single-atom Pt catalysts could exhibit superior oxidase-mimetic activity due to the fully exposure and utilization of every Pt-involved active sites. This oxidase mimic efficaciously boosts the generation of H 2 O 2 and 1O 2 species, and ultimately the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB). Fascinatingly, hydroquinone (HQ) inhibits the above reaction more sensitively than other phenolics, based on which, colorimetric HQ detection can be rationally achieved. Further, a colorimetric assay for α-glucosidase (α-Glu) detection is innovatively designed by using a robust HQ-generating phenolic, α-Arbutin, as the substrate. The wide linear range (0.01–8 U/mL) and low detection limit (0.0038 U/mL) indicate an admirable analytical performance that surpasses the vast majority of α-Glu assays previously reported. Encouragingly, the proposed colorimetric sensor has been successfully used for the detection of α-Glu in serum samples and the construction of "NAND" logic gate. This study not only provides ideas for the preparation of novel single-atom catalysts with enhanced oxidase-like activity, but also broadens the prospect for the design of new optical α-Glu assays by exploring suitable substrates. [ABSTRACT FROM AUTHOR]