Severe challenges are still remained for development of highly sensitive, selective and stable photoelectrochemical (PEC) sensing technology, albeit with its broad application for chloramphenicol ...(CAP) detection. Herein, a novel “signal-on” PEC aptasensor was fabricated based on a 3D self-supporting Z-scheme AgI/Ag/BiOI heterojunction arrays subtly integrated with in-situ formed biocatalytic precipitation (BCP) for highly sensitive and selective determination of CAP. Impressively, the HRP modified CAP aptamer (HRP-CAP aptamer) was released from the electrode by its strong affinity to the introduced CAP, and gradually terminated the BCP reaction, in turn recovering the photocurrent. By virtues of the 3D self-supporting AgI/Ag/BiOI Z-scheme heterojunction arrays and BCP signal amplification strategy, the resultant PEC sensor exhibited a wide linear range of 2–250 nM with a limit of detection (LOD) as low as 0.226 nM (S/N = 3). This work opens a new avenue for design of PEC aptasensing strategy and exhibits the marvelous potential in bioanalysis of environmental samples.
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•AgI/Ag/BiOI Z-scheme heterojunction arrays were prepared by ion-exchange and photoreduction.•A novel “signal-on” cathodic PEC aptasensor was constructed.•The BCP-based signal amplification strategy was designed for ultrasensitive analysis of CAP.•The PEC sensor exhibited highly improved analytical performance for CAP.
Transition metal catalysts are regarded as one of promising alternatives to replace traditional Pt‐based catalysts for oxygen reduction reaction (ORR). In this work, an efficient ORR catalyst is ...synthesized by confining Fe3C nanoparticles into N, S co‐doped porous carbon nanosheets (Fe3C/N,S‐CNS) via high‐temperature pyrolysis, in which 5‐sulfosalicylic acid (SSA) demonstrates as an ideal complexing agent for iron (ΙΙΙ) acetylacetonate while g‐C3N4 behaves as a nitrogen source. The influence of the pyrolysis temperature on the ORR performance is strictly examined in the controlled experiments. The obtained catalyst exhibits excellent ORR performance (E1/2 = 0.86 V; Eonset = 0.98 V) in alkaline electrolyte, coupled by exhibiting the superior catalytic activity and stability (E1/2 = 0.83 V, Eonset = 0.95 V) to Pt/C in acidic media. In parallel, its ORR mechanism is carefully illustrated by the density functional theory (DFT) calculations, especially the role of the incorporated Fe3C played in the catalytic process. The catalyst‐assembled Zn‐air battery also exhibits a much higher power density (163 mW cm–2) and ultralong cyclic stability in the charge–discharge test for 750 h with a gap increase down to 20 mV. This study provides some constructive insights for preparation of advanced ORR catalysts in green energy conversion units correlated systems.
The Fe3C/N,S‐CNS is prepared via a convenient one‐pot pyrolysis. The effective coating of Fe3C with a graphite carbon layer alleviates the carbon corrosion and metal loss, enabling the catalyst with outstanding activity and cycling stability for the acidic oxygen reduction reaction (ORR) and Zn‐air battery. According to the DFT calculations, Fe3C acts as the main active site in the catalytic process.
Transition metal‐based nitrogen‐doped carbon (M‐Nx‐C) is considered as a promising catalyst for the oxygen reduction reaction (ORR) in clean energy storage and conversion devices. Herein, ZnCo ...dual‐atomic sites are incorporated in hierarchical N‐doped carbon (HNC), with 1D nanotubes wrapped in 2D nanosheets structure (termed as 1D@2D ZnCo‐HNC), via a one‐step bio‐inspired pyrolysis. The feeding ratio of Zn to Co precursor and pyrolytic temperature are critically modulated to achieve well‐defined morphologies of the products, endowing them with the integrated merits of nanotubes and nanosheets as efficient ORR catalysts. Benefiting from the particular structure and electronic regulation of Zn on Co, the ZnCo‐Nx dual‐atomic system exhibits excellent ORR catalytic characteristics with an onset potential of 1.05 V and a half‐wave potential of 0.82 V. Density functional theory calculations further explain the regulating role of Zn, such that the adjusted Co in ZnCo‐Nx sites significantly reduces the energy cost to ultimately facilitate the ORR. Moreover, the Zn–air battery assembled with ZnCo‐HNC is capable of delivering the maximum power density of 123.7 mW cm−2 and robust stability for 110 h (330 cycles). This method provides a promising strategy for fabricating efficient transition metal‐based carbon catalysts for green energy devices.
With the unique 1D@2D structure and abundant ZnCo dual‐atomic sites, bio‐inspired ZnCo‐HNC exhibits excellent catalytic performances for the oxygen reduction reaction and a home‐assembled Zn–air battery. Density functional theory calculations further demonstrate that Co is the main active center in the ZnCo‐Nx system, while Zn serves as the charge adjuster.
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•The ultrathin RhIr NSs/NF was prepared by a simple and mild one-pot aqueous strategy at room temperature.•The unique sheet-like architectures provided large ECSA and exposed ...high-density active sites.•The self-supported RhIr NSs/NF had excellent HER activity and stability for the HER over a wide pH range.
The development of low-cost and high-efficiency electrocatalysts is very important for electrocatalytic hydrogen evolution reaction (HER) in water splitting system. Herein, ultrathin rhodium-iridium nanosheets were facilely in-situ grown on nickel foam (RhIr NSs/NF) by a one-pot aqueous strategy at room temperature. The sheet-like structures with the film thickness of 78 nm were identified by scanning electron microscopy and transmission electron microscopy. The catalyst showed greatly high HER features in both 1.0 M KOH and 0.5 M H2SO4 with the overpotentials of 15 and 14 mV to achieve 10 mA cm−2, respectively, surpassing most Pt-free catalysts. Also, the RhIr NSs/NF exhibited amazing catalytic stability during the long-term operation. This study offers a facile and rational pathway for design and synthesis of advanced HER electrocatalysts for energy conversion devices.
Bright green fluorescent GCNQDs were facilely prepared by a simple, rapid and eco-friendly microwave synthesis method. The GCNQDs with low cytotoxicity were used for vitro bioimaging of HeLa cells.
...•Bright green fluorescent GCNQDs doped with oxygen and sulfur were prepared.•The microwave synthesis method was simple, rapid, economical and eco-friendly.•The fluorescent quantum yield was up to 31.67%.•The GCNQDs with low cytotoxicity were used for vitro bioimaging of HeLa cells.
Herein, bright green luminescent graphitic carbon nitride quantum dots (GCNQDs) doped with oxygen and sulfur are prepared simply by microwave treatment of citric acid and thiourea. The as-obtained GCNQDs show excitation wavelength and pH dependent luminescence behaviors in the visible range. Besides, the GCNQDs exhibit high fluorescence quantum yield (31.67%), strong resistance to the interference of high ionic strength environment, and good biocompatibility as demonstrated by the cell viability assay. Thus, the resulting GCNQDs can be used as a promising fluorescent probe for HeLa cell imaging with low cytotoxicity, and have great potential in bioanalysis and related fields.
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Construction of high-efficiency, low cost and stable non-noble metal catalyst on air cathode is of great importance for design and assembly of rechargeable Zn-air battery. Eriochrome ...black T (EBT) has phenolic hydroxyl and -N=Ν- groups, which provides multiple coordination sites for metal ions. Herein, Co9S8 nanoclusters implanted in Co/Mn-S,N multi-doped porous carbon (Co9S8@Co/Mn-S,N-PC) are fabricated with the mixture (i.e. EBT, metal precursors and dicyandiamide) by a coordination regulated pyrolysis strategy. Specifically, EBT effectively chelates with the Co and Mn ions, resulting in multiple incorporation and fine modulation of the carbon electronic structures. Meanwhile, its sulfonic acid groups are reduced at such high temperature, accompanied by simultaneously embedding S element in the carbon, ultimately in situ forming Co9S8 nanoclusters. The Co9S8@Co/Mn-S,N-PC performs as an effective bifunctional oxygen catalyst, displaying a positive half-wave potential of 0.85 V and a large limiting current density of 5.89 mA cm−2 for oxygen reduction reaction (ORR) in alkaline media, coupled with a small overpotential of 320 mV at 10 mA cm−2 towards oxygen evolution reaction (OER), outperforming commercial Pt/C and RuO2 catalysts, respectively. Furthermore, the assembled rechargeable Zn-air battery with Co9S8@Co/Mn-S,N-PC exhibits the much better charge/discharge performance and long-term durability (210 h, 630 cycles). This research opens an instructive avenue to develop high-efficient and stable bifunctional oxygen electrocatalysts in energy transformation and storage devices.
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Transition metal and nitrogen (N) doped carbon materials are regarded as promising alternatives to expensive Pt-based catalysts for oxygen reduction reaction (ORR), thanks to their ...natural abundance, good stability and high energy conversion efficiency. Herein, a facile efficient pyrolysis approach was developed to prepare graphene-encapsulated Co nanoparticles (NPs) embedded in porous nitrogen-doped graphitic carbon nanosheets (Co@G/N-GCNs), in which g-C3N4 served as C and N sources, and cobalt phthalocyanine (CoPc) as the Co- and N-sources. The as-obtained catalyst exhibited exceptional ORR activity (E1/2 = 0.86 V vs. RHE), good durability (12 mV negative shift of E1/2 after 2000 cycles), and strong methanol resistance, surpassing those of commercial Pt/C catalyst in alkaline conditions. The pyrolysis temperature and entrapped contents of metal NPs had critical impacts on the ORR features. This work offers a feasible strategy for designing low-cost non-noble-metal catalysts for energy storage and conversion.
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Design of efficient and durable oxygen reduction reaction (ORR) electrocatalysts still remains challenge in sustainable energy storage and conversion devices. To achieve sustainable ...development, it is of importance to prepare high-quality carbon-derived ORR catalysts from biomass. Herein, Fe5C2 nanoparticles (NPs) were facilely entrapped in Mn, N, S-codoped carbon nanotubes (Fe5C2/Mn, N, S-CNTs) by a one-step pyrolysis of the mixed lignin, metal precursors and dicyandiamide. The resulting Fe5C2/Mn, N, S-CNTs had open and tubular structures, which exhibited positive shifts in the onset potential (Eonset = 1.04 V) and high half-wave potential (E1/2 = 0.85 V), showing excellent ORR characteristics. Further, the typical catalyst-assembled Zn-air battery showed a high power density (153.19 mW cm−2) and good cycling performance as well as obvious cost advantage. The research provides some valuable insights for rational construction of low-cost and environmentally sustainable ORR catalysts in clean energy field, coupled by offering some valuable insights for reusing biomass wastes.
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Rational synthesis of cost-effectiveness, ultra-stable and high-efficiency bifunctional oxygen catalysts are pivotal for Zn-air batteries. Herein, fine Co2P/FeCo nanoparticles (NPs) ...anchored on Mn, N, P-codoped bamboo-like carbon nanotubes (Co2P/FeCo/MnNP-BCNTs) are constructed in the coexistence of melamine, poly(4-vinylpyridine) and adenosine-5′-diphosphate disodium salt (ADP) by convenient pyrolysis and follow-up acid treatment. The as-prepared catalyst exhibits the higher onset potential (Eonset = 0.97 V vs. RHE) and half-wave potential (E1/2 = 0.88 V vs. RHE) for oxygen reduction reaction (ORR), coupled with excellent oxygen evolution reaction (OER) with the lower overpotential of 324 mV at 10 mA cm−2. Notably, the home-made Zn-air battery delivers the greater peak power density of 220 mW cm−2, together with the outstanding cycling stability. The excellent performances of Co2P/FeCo/MnNP-BCNTs catalyst are mainly attributed to the highly conductive carbon nanotubes and the synergistic effects between carbon nanotubes and Co2P/FeCo NPs. This work offers a novel strategy to explore advanced bifunctional oxygen catalysts for high-efficiency metal-air batteries.
