The traditional luminol–H2O2 electrochemiluminescence (ECL) sensing platform suffers from self‐decomposition of H2O2 at room temperature, hampering its application for quantitative analysis. In this ...work, for the first time we employ iron single‐atom catalysts (Fe‐N‐C SACs) as an advanced co‐reactant accelerator to directly reduce the dissolved oxygen (O2) to reactive oxygen species (ROS). Owing to the unique electronic structure and catalytic activity of Fe‐N‐C SACs, large amounts of ROS are efficiently produced, which then react with the luminol anion radical and significantly amplify the luminol ECL emission. Under the optimum conditions, a Fe‐N‐C SACs–luminol ECL sensor for antioxidant capacity measurement was developed with a good linear range from 0.8 μm to 1.0 mm of Trolox.
Boosting luminescence: The traditional luminol–H2O2 electrochemiluminescence (ECL) sensing platform suffers from self‐decomposition of H2O2 at room temperature, hampering its application for quantitative analysis. Single‐atom iron boosts luminol ECL by in situ generating reactive oxygen species, achieving sensitive detection of antioxidants.
Highlights
Secondary-atom-doped strategy was proposed to synthesize single-atom electrocatalyst.
The increase in both the density of active sites and their intrinsic activity was achieved ...simultaneously.
The resultant single-atom catalyst shows outstanding ORR activity in acidic media.
Single-atom catalysts (SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis. However, a large room for improving their activity and durability remains. Herein, we construct atomically dispersed Fe sites in N-doped carbon supports by secondary-atom-doped strategy. Upon the secondary doping, the density and coordination environment of active sites can be efficiently tuned, enabling the simultaneous improvement in the number and reactivity of the active site. Besides, structure optimizations in terms of the enlarged surface area and improved hydrophilicity can be achieved simultaneously. Due to the beneficial microstructure and abundant highly active FeN
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moieties resulting from the secondary doping, the resultant catalyst exhibits an admirable half-wave potential of 0.81 V versus 0.83 V for Pt/C and much better stability than Pt/C in acidic media. This work would offer a general strategy for the design and preparation of highly active SACs for electrochemical energy devices.
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We report a computational study of the anharmonicity of the vibrational modes of fullerenes using the “moments method” (Gao et al., 2015) with a Tersoff-style potential for carbon. We ...find that the frequencies of all vibrational modes drop systematically with temperature and that the size of the fullerene does not strongly determine the anharmonicity of its modes. Favorable comparison is made with experiments.
•The tracer agent CDs and the “drug” TP were encapsulated in ZIF-8 through a facile co-precipitation method.•Efficient loading of two signal molecules resulted in a high sensitivity of ...“sense-and-treat” ELISA.•The conception of “sense-and-treat” ELISA exhibited high sensitivity towards carcinoembryonic antigen detection.•A good linear correlation between results from the “sense” part and the “treat” part ensured the reliable accuracy of ELISA.
Enzyme-linked immunosorbent assay (ELISA) has been widely used in the area of biological analysis, while there are still some challenges getting in the way to ensure both excellent sensitivity and reliable accuracy. To overcome these obstacles, we simulated the “smart” sense-and-treat carriers in a drug delivery system to fabricate an improved ELISA, employing zeolitic imidazolate framework-8 (ZIF-8) as the carrier to deliver the tracer agent carbon dots (CDs) and the “drug” thymolphthalein (TP), which was referred to as a “sense-and-treat” ELISA. In the “sense” part, the strong fluorescence intensity of CDs could be observed directly to achieve the sensitive detection of the target. In the “treat” part, after stimulation of alkaline solution, TP was released from ZIF-8 carriers and generated a color change with an obvious absorption, which was beneficial for increasing the sensitivity of this ELISA due to the high loading of the TP. Finally, we took carcinoembryonic antigen (CEA) as a model and performed dual-modal detection using this improved “sense-and-treat” ELISA to accomplish quantitative determinations sensitively and accurately. In addition, the results indicated by the two parts kept good concordance, which could demonstrate the reliable accuracy of this ELISA.
The establishment of advanced electrocatalysts with remarkable performance and cost effectiveness for the oxygen evolution reaction (OER) is an emerging need for the production of clean hydrogen ...fuel. In this work, three-dimensional (3D) amorphous NiFeIr x /Ni core–shell nanowire@nanosheets (NW@NSs) are successfully synthesized through a facile one-step reduction process with atomically isolated Ir atoms anchored on an NiFe-based core. By taking advantage of their unique structure and composition, the resultant NiFeIr x /Ni NW@NSs have a high electrocatalytic activity for OER which can deliver current densities of 10 and 100 mA cm–2 at overpotentials as low as 200 and 250 mV in 1 M KOH, respectively. It is worth noting that NiFeIr x /Ni NW@NSs exhibit outstanding long-term stability over 12 h at a current density of 10 mA cm–2. Theoretical calculations also reveal that the intrinsic activity of the resultant NiFeIr x /Ni NW@NSs is significantly enhanced upon the addition of Ir single atoms, highlighting the critical role of the synergistic effect between Ir single atoms and the support. Due to their easy synthesis and superior electrochemical performance, the newly designed nanostructures may find promising potential applications in water splitting and other related fields.
Design of highly active carbon nanozymes and further establishment of ultrasensitive biosensors remain a challenge. Herein, hierarchically porous carbon nanozymes with sulfur (S)/nitrogen (N) ...codoping (SNC) were developed. Compared with N-doped carbon (NC) nanozymes, SNC nanozymes have a smaller Michaelis–Menten constant and higher specific activities, demonstrating that the S-doping in SNC nanozymes could not only enhance their affinity toward substrates but also improve their catalytic performance. These results may be caused by the synergistic effect of heteroatoms (S and N). Because of the good enzyme-like activity, the proposed SNC nanozymes were exploited to the colorimetric detection of the total antioxidant capacity (TAC) using ascorbic acid as a typical model with a limit of detection of 0.08 mM. Because of its high sensitivity and selectivity and encouraging performance, the detection method presented practical feasibility for the TAC assay in commercial beverages. This work paves a way to design the highly active carbon nanozymes and expand their applications in the construction of high-performance biosensors.
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•CoNi LDH/Ti3C2Tx is obtained by using Ti3C2Tx/NF as support to load CoNi LDH via electrodeposition.•CoNi LDH/Ti3C2Tx displays prominent OER activity and durability in alkaline ...electrolyte.•Binding strength of intermediates is optimized by strong interaction of CoNi LDH and Ti3C2Tx.
Developing efficient nonprecious metal electrocatalysts is urgently needed to promote the sluggish kinetics of oxygen evolution reaction (OER). Transition metals-based layered double hydroxides (LDH) have been considered as highly active OER catalysts, while low conductivity and limited active site exposures hinder their further applications. Herein, CoNi LDH/Ti3C2Tx MXene is facilely constructed by using Ti3C2Tx coated nickel foam as support to load CoNi LDH through electrodeposition. Surprisingly, a significant enhancement in OER activity of pristine CoNi LDH is achieved due to the metallic conductivity and hydrophilic and electronegative surface of Ti3C2Tx. Importantly, CoNi LDH/Ti3C2Tx displays prominent OER performance and stability in alkaline medium, which exhibits a low overpotential of 257.4 mV to reach current density of 100 mA/cm2 and a small Tafel slope of 68 mV/dec. The experimental and calculated results demonstrate electron transfer from CoNi LDH to Ti3C2Tx plays a significant role in boosting OER activity by lowering the binding strength of intermediates.
Single-atom nanozymes (SAzymes), as novel nanozymes with atomically dispersed active sites, are of great importance in the development of nanozymes for their high catalytic activities, the maximum ...utilization efficiency of metal atoms, and the simple model of active sites. Herein, the peroxidase-like SAzymes with high-concentration Cu sites on carbon nanosheets (Cu–N–C) were synthesized through a salt-template strategy. With the densely distributed active Cu atoms (∼5.1 wt %), the Cu–N–C SAzymes exhibit remarkable activity to mimic natural peroxidase. Integrating Cu–N–C SAzymes with natural acetylcholinesterase and choline oxidase, three-enzyme-based cascade reaction system was constructed for the colorimetric detection of acetylcholine and organophosphorus pesticides. This work not only provides a strategy to synthesize SAzymes with abundant active sites but also gives some new insights for robust nanozyme biosensing systems.
Single‐atom catalysts (SACs) have attracted extensive attention in the catalysis field because of their remarkable catalytic activity, gratifying stability, excellent selectivity, and 100% atom ...utilization. With atomically dispersed metal active sites, Fe‐N‐C SACs can mimic oxidase by activating O2 into reactive oxygen species, O2−• radicals. Taking advantages of this property, single‐atom nanozymes (SAzymes) can become a great impetus to develop novel biosensors. Herein, the performance of Fe‐N‐C SACs as oxidase‐like nanozymes is explored. Besides, the Fe‐N‐C SAzymes are applied in biosensor areas to evaluate the activity of acetylcholinesterase based on the inhibition toward nanozyme activity by thiols. Moreover, this SAzymes‐based biosensor is further used for monitoring the amounts of organophosphorus compounds.
Fe‐N‐C single‐atom nanozymes with distributed FeN2 active sites possessing oxidase‐like activity are reported. Based on the inhibition mode by thiols, the Fe‐N‐C single‐atom nanozymes show promising application for evaluating the activity of acetylcholinesterase and constructing sensitive biosensors to detect mercapto molecules and organophosphorus compounds.
Noble metal-based nanomaterials have been a hot research topic during the past few decades. Particularly, self-assembled porous architectures have triggered tremendous interest. At the forefront of ...porous nanostructures, there exists a research endeavor of noble metal aerogels (NMAs), which are unique in terms of macroscopic assembly systems and three-dimensional (3D) porous network nanostructures. Combining excellent features of noble metals and the unique structural traits of porous nanostructures, NMAs are of high interest in diverse fields, such as catalysis, sensors, and self-propulsion devices. Regardless of these achievements, it is still challenging to rationally design well-tailored NMAs in terms of ligament sizes, morphologies, and compositions and profoundly investigate the underlying gelation mechanisms. Herein, an elaborate overview of the recent progress on NMAs is given. First, a simple description of typical synthetic methods and some advanced design engineering are provided, and then, the gelation mechanism models of NMAs are discussed in detail. Furthermore, promising applications particularly focusing on electrocatalysis and biosensors are highlighted. In the final section, brief conclusions and an outlook on the existing challenges and future chances of NMAs are also proposed.
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