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As a typical class of single‐atom catalysts (SACs) possessing prominent advantages of high reactivity, high selectivity, high stability, and maximized atomic utilization, emerging metal‐nitrogen‐doped carbon (M‐N‐C) materials, wherein dispersive metal atoms are coordinated to nitrogen atoms doped in carbon nanomaterials, have presented a high promise to replace the conventional metal or metal oxides‐based catalysts. In this work, recent progress in M‐N‐C‐based materials achieved in both theoretical and experimental investigations is summarized and general principles for novel catalysts design from electronic structure modulating are provided. Firstly, the applications and mechanisms on the advantages and challenges of M‐N‐C‐based materials for a variety of sustainable fuel generation and bioinspired reactions, including the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), and nanozyme reactions are reviewed. Then, strategies toward enhancing the catalytic performance by engineering the nature of metal ion centers, coordinative environment of active centers, carbon support, and their synergistic cooperation, are proposed. Finally, prospects for the rational design of next generation high‐performance M‐N‐C‐based catalysts are outlined. It is expected that this work will provide insights into high‐performance catalysts innovation for sustainable and environmental technologies. The rational design of metal‐nitrogen‐doped carbon (M‐N‐C) materials is at the cutting‐edge of materials research. Herein, the recent progress of M‐N‐C in sustainable fuel generation and biological applications is reviewed. General principles toward designing high‐performance M‐N‐C based nanocatalysts by engineering the nature of metal ion centers, the coordinative environment of active centers, the carbon support, and beyond are outlined.

A novel colorimetric immunoassay for the detection of Staphylococcus aureus ( S. aureus ) based on a combination of immunomagnetic separation and signal amplification via etching-enhanced peroxidase-like catalytic activity of gold nanoparticles (AuNPs) was developed. Nanoconjugates composed of gold and iron oxide nanoparticles were synthesized and further modified with anti S. aureus immunoglobulin Y (IgY), which was used for the selective enrichment and rapid separation of target bacteria in complex matrices. AuNPs functionalized with anti S. aureus aptamer were used as an artificial enzyme which has peroxidase-like catalysis activity. Catalytic activity of AuNPs is inhibited by modifying aptamer. However, catalysis of modified AuNPs remarkably enhanced by hydrogen peroxide etching. Based on collecting unbound modified AuNPs in the supernatant and 3,3′,5,5′-tetramethylbenzidine-hydrogen peroxide reporting system, the yellow color of solution decreases linearly with increasing the concentration of S. aureus ranging from 10 to 10 6  cfu/mL. The limit of detection is 10 cfu/mL, and total detection time is 65 min. The recoveries of the S. aureus spiked in food samples are 88.2–119.8%. Schematic illustration of colorimetric method for detection of S. aureus based on the IgY-Fe 3 O 4 /Au nanocomposites as capture probes and apt-AuNPs as artificial enzyme with etching-enhanced peroxidase-like catalytic activity.

The production of biodiesel through chemical production processes of transesterification reaction depends on suitable catalysts to hasten the chemical reactions. Therefore, the initial selection of catalysts is critical although it is also dependent on the quantity of free fatty acids in a given sample of oil. Earlier forms of biodiesel production processes relied on homogeneous catalysts, which have undesirable effects such as toxicity, high flammability, corrosion, by‐products such as soap and glycerol, and high wastewater. Heterogeneous catalysts overcome most of these problems. Recent developments involve novel approaches using biomass and bio‐waste resource derived heterogeneous catalysts. These catalysts are renewable, non‐toxic, reusable, offer high catalytic activity and stability in both acidic and base conditions, and show high tolerance properties to water. This review work critically reviews biomass‐based heterogeneous catalysts, especially those utilized in sustainable production of biofuel and biodiesel. This review examines the sustainability of these catalysts in literature in terms of small‐scale laboratory and industrial applications in large‐scale biodiesel and biofuel production. Furthermore, this work will critically review natural heterogeneous biomass waste and bio‐waste catalysts in relation to upcoming nanotechnologies. Finally, this work will review the gaps identified in the literature for heterogeneous catalysts derived from biomass and other biocatalysts with a view to identifying future prospects for heterogeneous catalysts.

A series of α-, β-unsaturated ketone derivatives of four substituted pyrazoles were synthesised using Claisen-Schmidt condensation reaction and were characterised using Fourier-transform infrared (FTIR) spectroscopy, 1 H nuclear magnetic resonance (NMR) and 13 C NMR spectroscopy. Further, these derivatives were studied under application as an oxidising agent in a compost-based microbial fuel cell (cMFC) to enhance its reduction efficiency. Characterisation methods of cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chrono-amperometry (CS) were employed to analyse the behaviour of the coin-cell device with and without pyrazoles at the cathode. Concentration dependence of the best pyrazole out of the series was studied to optimise the device performance. The results indicate the enhancement in bio-electro-catalytic activity and output power density when the cathode of the cMFC is laced with pyrazoles. In addition, sustainability and stability of the device was also investigated, and study to confirm the role of micro-organisms in the compost was also performed.

A dual-channel probe was developed, based on a novel composite metal organic frameworks (ZnMOF-74@Al-MOF) for glyphosate determination through ratio fluorescence and colorimetric methods . The prepared probe can not only recognize and combine glyphosate by introducing copper ion into the MOF, but also possess peroxidase-like catalytic activity. The recognition of target glyphosate brought about changes relative to its concentration on fluorescence intensity and ultraviolet absorption. And, the high specific surface area and porosity of porphyrin MOF provides the developed probe with more response opportunities to afford a better detection performance for glyphosate. Under optimum conditions, the copper ion-mediated method exhibited good detection performance for glyphosate with low detection limits (0.070 and 0.092 μg mL −1 for fluorescence and colorimetric techniques, respectively). Furthermore, the possible mechanisms of the fluorescence quenching and the peroxidase-like catalytic of the probe were also explored. This dual-channel method was applied to monitor glyphosate degradation in environmental samples and satisfactory results were obtained. Graphical abstract

Pt-free dye-sensitized solar cells (DSSCs) have emerged as cost-effective alternatives in energy storage technologies, attracting considerable research interest over the past two decades. In this study, we successfully fabricated a NiSe/Co 3 Se 4 hybrid counter electrode (CE) using a facile ultrasonic-assisted hydrothermal method, demonstrating its potential for enhancing the performance and stability of DSSCs. X-ray diffraction (XRD) investigation showed hexagonal NiSe and monoclinic Co 3 Se 4 phases in the composite, with smaller crystallite sizes indicating better interfacial contacts. SEM and TEM micrographs show a well-defined nanostructure with spherical NiSe particles and rod-like Co 3 Se 4 particles. This results in a large surface area and improved porosity, as validated by BET analysis. Electrochemical studies, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization, show that the NiSe/Co 3 Se 4 composite has superior electro catalytic activity compared to individual NiSe and Co 3 Se 4 electrodes, closely matching the performance of the Pt electrode. When integrated into DSSCs, the NiSe/Co 3 Se 4 composite CE obtained an energy conversion efficiency of 9.01%, with notably enhanced short-circuit current density ( J sc ) and open-circuit voltage ( V oc ). The NiSe/Co 3 Se 4 combination is a good contender for large-scale DSSC applications due to its strong photovoltaic performance and stability over 42 days under one-sun illumination.

Understanding the surface chemistry of target gases on sensing materials is essential for designing high-performance gas sensors. Here, we report the effect of Pt-loading on the sensing of volatile organic compounds (VOCs) with ZnO gas sensors, demonstrated by diffuse reflection infrared Fourier transform (DRIFT) spectroscopy. Pt-loaded ZnO nanocrystals (NCs) of 13~22 nm are synthesized using the hot soap method. The synthesized powder is deposited on an alumina substrate by screen-printing to form a particulate gas sensing film. The 0.1 wt% Pt-loaded ZnO NC sensor shows the highest sensor response to acetone and ethanol at 350 °C, while the responses to CO and H2 are small and exhibit good selectivity to VOCs. The gas sensing mechanism of ethanol with Pt-ZnO NCs was studied by in situ DRIFT spectroscopy combined with online FT-IR gas analysis. The results show that ethanol reacts with small Pt-loaded ZnO to produce intermediate species such as acetaldehyde, acetate, and carbonate, which generates a high sensor response to ethanol in air.

In this work, cost-effective reduced graphene oxide/copper oxide (rGO/CuO) nanocomposite was synthesized by the reduction of GO to rGO and deposition of CuO on the surface of rGO using single step simple chemical method. The prepared nanocomposite was characterized using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) and Fourier-transform infrared (FT-IR) spectroscopy. The appearance of peak at 2θ = 11.03° confirmed the synthesis of GO and peaks at 25.65°, 36.14°, 43.09°, 49.91° and 69.52° indicated the synthesis of the nanocomposite. It was found that the normal particulate size of the prepared nanocomposite was in range of 30 to 50 nm. SEM analysis was done to demonstrate the external morphology of the prepared GO and the nanocomposite. The prepared rGO/CuO nanocomposite was analyzed towards photo-catalytic activity for the degradation of methylene blue (MB) and for the catalytic reduction of 4-nitrophenol (4-NP) to 4- aminophenol (4-AP). It was found that about 81% of MB was degraded in 240 min under UV light and complete conversion of 4-NP to 4-AP was done in only 2 min. The prepared rGO/CuO nanocomposite was also analyzed for anti-microbial activity. It was found that the rGO/CuO nanocomposite exhibits better anti-bacterial and anti-fungal activities than GO. The results indicated the increased biocompatibility of the rGO/CuO nanocomposites than GO.

Single-atom catalyst (SAC) is one of the newest catalysts, and attracts people’s wide attention in cancer therapy based on their characteristics of maximum specific catalytic activity and high stability. We designed and synthesized a Fe-N decorated graphene nanosheet (Fe-N 5 /GN SAC) with the coordination number of five. Through enzymology and theoretical calculations, the Fe-N 5 /GN SAC has outstanding intrinsic peroxidase-like catalytic activity due to single-atom Fe site with five-N-coordination structure. We explored its potential on lung cancer therapy, and found that it could kill human lung adenocarcinoma cells (A549) by decomposing hydrogen peroxide (H 2 O 2 ) into toxic reactive oxygen species (ROS) under acidic microenvironment in three-dimensional (3D) lung cancer cell model. Our study demonstrates a promising application of SAC with highly efficient single-atom catalytic sites for cancer treatment.

Bromelain is a unique enzyme-based bioactive complex containing a mixture of cysteine proteases specifically found in the stems and fruits of pineapple (Ananas comosus) with a wide range of applications. MD2 pineapple harbors a gene encoding a small bromelain cysteine protease with the size of about 19 kDa, which might possess unique properties compared to the other cysteine protease bromelain. This study aims to determine the expressibility and catalytic properties of small-sized (19 kDa) bromelain from MD2 pineapple (MD2-SBro). Accordingly, the gene encoding MD2-SBro was firstly optimized in its codon profile, synthesized, and inserted into the pGS-21a vector. The insolubly expressed MD2-SBro was then resolubilized and refolded using urea treatment, followed by purification by glutathione S-transferase (GST) affinity chromatography, yielding 14 mg of pure MD2-SBro from 1 L of culture. The specific activity and catalytic efficiency (kcat/Km) of MD2-SBro were 3.56 ± 0.08 U mg−1 and 4.75 ± 0.23 × 10−3 µM−1 s−1, respectively, where optimally active at 50 °C and pH 8.0, and modulated by divalent ions. The MD2-SBro also exhibited the ability to scavenge the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) with an IC50 of 0.022 mg mL−1. Altogether, this study provides the production feasibility of active and functional MD2-Bro as a bioactive compound.