Boron modification promoting electrochemical surface reconstruction of NiFe-LDH for efficient and stable freshwater/seawater oxidation catalysis.

Transition metal-based electrocatalysts generally take place surface reconstruction in alkaline conditions, but little is known about how to improve the reconstruction to a highly active oxyhydroxide surface for an efficient and stable oxygen evolution reaction (OER). Herein, we develop a strategy to accelerate surface reconstruction by combining boron modification and cyclic voltammetry (CV) activation. Density functional theory calculations and in-situ/ex-situ characterizations indicate that both B-doping and electrochemical activation can reduce the energy barrier and contribute to the surface evolution into highly active oxyhydroxides. The formed oxyhydroxide active phase can tune the electronic configuration and boost the OER process. The reconstructed catalyst of CV-B-NiFe-LDH displays excellent alkaline OER performance in freshwater, simulated seawater, and natural seawater with low overpotentials at 100 mA cm-2 (η100: 219, 236, and 255 mV, respectively) and good durability. This catalyst also presents outstanding Cl- corrosion resistance in alkalized seawater electrolytes. The CV-B-NiFe-LDH||Pt/C electrolyzer reveals prominent performance for alkalized freshwater/seawater splitting. This study provides a guideline for developing advanced OER electrocatalysts by promoting surface reconstruction.

Thermal Shock Synthesis for Loading Sub-2 nm Ru Nanoclusters on Titanium Nitride as a Remarkable Electrocatalyst toward Hydrogen Evolution Reaction.

Heterogeneous catalysts embracing metal entities on suitable supports are profound in catalyzing various chemical reactions, and substantial synthetic endeavors in metal-support interaction modulation are made to enhance catalytic performance. Here, it is reported the loading of sub-2 nm Ru nanocrystals (NCs) on titanium nitride support (HTS-Ru-NCs/TiN) via a special Ru-Ti interaction using the high-temperature shock (HTS) method. Direct dechlorination of the adsorbed RuCl3, ultrafast nucleation process, and short coalescence duration at ultrahigh temperatures contribute to the immobilization of Ru NCs on TiN support via producing the Ru-Ti interfacial perimeter. HTS-Ru-NCs/TiN shows remarkable activity toward hydrogen evolution reaction (HER) in alkaline solution, yielding ultralow overpotentials of 16.3 and 86.6 mV to achieve 10 and 100 mA cm-2, respectively. The alkaline and anion exchange membrane water electrolyzers assembled using HTS-Ru-NCs/TiN yield 1.0 A cm-2 at 1.65 and 1.67 V, respectively, which validate its applicability in the hydrogen production industry. Theoretical simulations reveal the favorable formation of Ru─O and Ti─H bonds at the interfacial perimeters between Ru NCs and TiN, which accelerates the prerequisite water dissociation kinetics for enhanced HER activity. This exemplified work motivates the design of specific interfacial perimeters via the HTS strategy to improve the performance of diverse catalysis.

Unraveling the crucial contribution of additive chromate to efficient and stable alkaline seawater oxidation on Ni-based layered double hydroxides.

Seawater electrolysis to generate hydrogen offers a clean, green, and sustainable solution for new energy. However, the catalytic activity and durability of anodic catalysts are plagued by the corrosion and competitive oxidation reactions of chloride in high concentrations. In this study, we find that the additive CrO42- anions in the electrolyte can not only promote the formation and stabilization of the metal oxyhydroxide active phase but also greatly mitigate the adverse effect of Cl- on the anode. Linear sweep voltammetry, accelerated corrosion experiments, corrosion polarization curves, and charge transfer resistance results indicate that the addition of CrO42- distinctly improves oxygen evolution reaction (OER) kinetics and corrosion resistance in alkaline seawater electrolytes. Especially, the introduction of CrO42- even in the highly concentrated NaCl (2.5 M) electrolyte prolongs the durability of NiFe-LDH to almost five times the case without CrO42-. Density functional theory calculations also reveal that the adsorption of CrO42- can tune the electronic configuration of active sites of metal oxyhydroxides, enhance conductivity, and optimize the intermediate adsorption energies. This anionic additive strategy can give a better enlightenment for the development of efficient and stable oxygen evolution reactions for seawater electrolysis.

Organic carbon in wet deposition of an urbanized coastal bay, North China: Flux, sources and biogeochemical implications.

The process of atmospheric organic carbon (OC) entering the ocean through wet deposition plays a crucial role in the global carbon cycle. To gain insights into the biogeochemical dynamics of OC at the land-sea margin, we conducted an extensive four-year investigation on precipitation OC in Jiaozhou Bay (JZB). The results showed that the volume-weighted mean concentration of particulate OC (POC) and dissolved OC (DOC) in precipitation were 0.38 and 2.06 mg C L-1 with an average wet deposition flux of OC for 2666.5 mg C m-2 yr-1. The source of POC in precipitation is predominantly by the C3 plant emission and burning and fossil fuel combustion. Wet deposition contributed 986.6 t yr-1 of OC of which 506.3 t yr-1 of bioavailable DOC, which could have significant implications for carbon cycle in the JZB. This study could enhance the understanding of the marine atmospheric OC in coastal areas.

Monometallic Ultrasmall Nanocatalysts via Different Valence Atomic Interfaces Boost Hydrogen Evolution Catalysis.

Synergistic monometallic nanocatalysts have attracted much attention due to their high intrinsic activity properties. However, current synergistic monometallic nanocatalysts tend to suffer from long reaction paths due to restricted nanoscale interfaces. In this paper, we synthesized the interstitial compound N-Pt/CNT with monometallic atomic interfaces. The catalysts are enriched with atomic interfaces between higher valence Ptδ+ and Pt0, allowing the reaction to proceed synergistically within the same component with an ideal reaction pathway. Through ratio optimization, N2.42-Pt/CNT with a suitable ratio of Ptδ+ and Pt0 is synthesized. And the calculated turnover frequency of N2.42-Pt/CNT is about 37.4 s-1 (-0.1 V vs reversible hydrogen electrode (RHE)), six times higher than that of the commercial Pt/C (6.58 s-1), which is the most intrinsically active of the Pt-based catalysts. Moreover, prepared N2.42-Pt/CNT exhibits excellent stability during the chronoamperometry tests of 200 h. With insights from comprehensive experiments and theoretical calculations, Pt with different valence states in monometallic atomic interfaces synergistically accelerates the H2O dissociation step and optimizes the Gibbs free energy of H* adsorption. And the existence of desirable hydrogen transfer paths substantially facilitates hydrogen evolution reaction kinetics.

The Superaerophobic N-Doped Carbon Nanocage with Hydrogen Spillover Effort for Enhanced Hydrogen Evolution.

Under the high current density, the excessive strong adsorption of H* intermediates and H2 accumulation the catalysts are the major obstacle to the industrial application of hydrogen evolation reaction (HER) catalysts. Herein, through experimental exploration, it is found that the superaerophobic Nitrogen (N)-doped carbon material can promote the rapid release of H2 and provide H* desorption site for the hydrogen spillover process, which makes it have great potential as the catalysts support for hydrogen spillover. Based on this discovery, this work develops the hydrogen spillover catalyst with electron-rich Pt sites loaded on N-doped carbon nanocage (N-CNC) with adjustable work function. Through a series of comprehensive electrochemical tests, the existence of hydrogen spillover effort has been proved. Moreover, the in situ tests showed that pyrrolic-N can activate adjacent carbon sites as the desorption sites for hydrogen spillover. The Pt@N-1-CNC with the minimum work function difference (ΔΦ) between Pt NPs and support shows superior hydrogen evolution performance, only needs overpotential of 12.2 mV to reach current density of 10 mA cm-2 , outstanding turnover frequency (TOF) (44.7 s-1 @100 mV) and superior durability under the 360 h durability tests at current density of 50 mA cm-2 .

Precise Interstitial Built-In Electric Field Tuning for Hydrogen Evolution Electrocatalysis.

The built-in electric field (BEF) has become an effective means of adjusting the electronic structure and hydrogen spillover to influence the adsorption of intermediates. However, the previously reported BEF cannot be tuned continuously and precisely. Herein, a series of nanocatalysts with interstitial BEF were successfully synthesized, and the effect of precisely tuned interstitial BEF on the intermediate's adsorption and hydrogen spillover was systematically investigated using changing the insertion of interstitial B. Three catalysts with different BEF strengths were obtained by changing the interstitial content (B0.22-Cu/NC, B0.30-Cu/NC, B0.41-Cu/NC), and it was demonstrated that B0.30-Cu/NC gave the best catalytic performance for hydrogen evolution reactions (HERs). The turnover frequency (TOF) value is shown to reach 0.36 s-1 at just -0.1 V vs. RHE, which is about 3 times that of Cu (0.12 s-1). For the HER, it is one of the best Cu-based catalysts reported to date (Table S3). Besides, when the catalyst was applied to the cathode of the PEM water electrolyzer, B0.30-Cu/NC exhibited long-time stability at a water-splitting current density of 500 mA cm-2. Density functional theory and in situ Raman spectroscopy suggest that a suitable interstitial BEF can not only optimize the intermediate's adsorption but also promote hydrogen spillover.

Polyhedral Au Nanoparticle/MoOx Heterojunction-Enhanced Ultrasensitive Dual-Mode Biosensor for miRNA Detection Combined with a Nonenzymatic Cascade DNA Amplification Circuit.

A novel homologous surface-enhanced Raman scattering (SERS)-electrochemical (EC) dual-mode biosensor based on a 3D/2D polyhedral Au nanoparticle/MoOx nanosheet heterojunction (PAMS HJ) and target-triggered nonenzyme cascade autocatalytic DNA amplification (CADA) circuit was constructed for highly sensitive detection of microRNA (miRNA). Mixed-dimensional heterostructures were prepared by in situ growth of polyhedral Au nanoparticles (PANPs) on the surface of MoOx nanosheets (MoOx NSs) via a seed-mediated growth method. As a detection substrate, the resulting PAMS HJ shows the synergistic effects of both electromagnetic and chemical enhancements, efficient charge transfer, and robust stability, thus achieving a high SERS enhancement factor (EF) of 4.2 × 109 and strong EC sensing performance. Furthermore, the highly efficient molecular recognition between the target and smart lock probe and the gradually accelerated cascade amplification reaction further improved the selectivity and sensitivity of our sensing platform. The detection limits of miRNA-21 in SERS mode and EC mode were 0.22 and 2.69 aM, respectively. More importantly, the proposed dual-mode detection platform displayed excellent anti-interference and accuracy in the analysis of miRNA-21 in human serum and cell lysates, indicating its potential as a reliable tool in the field of biosensing and clinical analysis.

MnOx Film-Coated NiFe-LDH Nanosheets on Ni Foam as Selective Oxygen Evolution Electrocatalysts for Alkaline Seawater Oxidation.

Compared to freshwater electrolysis, seawater electrolysis to produce hydrogen is preferable and more promising, but this technology is plagued by the electrode's corrosion and oxidative reactions of the competitive Cl- ion on the anode. To develop efficient oxygen evolution reaction (OER) catalysts for seawater electrolysis, the ultrathin MnOx film-covered NiFe-layered double-hydroxide nanosheet array is directly assembled on Ni foam (MnOx/NiFe-LDH/NF) by hydrothermal and electrodeposition in turn. This catalyst demonstrates excellent OER-selective activity in alkaline saline electrolytes. In 1 M KOH/0.5 M NaCl and 1 M KOH/seawater electrolytes, MnOx/NiFe-LDH/NF exhibits lower overpotentials at 100 mA cm-2 (η100 values of 265 and 276 mV, respectively) and Tafel slopes (73 and 77 mV decade-1, respectively) than does the NiFe-LDH/NF electrode (η100 values of 298 and 327 mV and Tafel slopes of 91 and 140 mV decade-1, respectively). In alkaline saline solutions, the stability and durability of the former are also better than those of the latter. The good OER selectivity and catalytic performance are attributed to the MnOx overlayer that selectively blocks Cl- anions from approaching catalytic centers, and the good conductivity, fast kinetics, more oxygen vacancies, and abundant active sites of MnOx/NiFe-LDH/NF. The robust stability is due to the enhanced resistance for Cl- corrosion stemming from the MnOx protective film. Hence, MnOx/NiFe-LDH/NF can act as a promising OER electrocatalyst for alkalized natural seawater electrolysis.

PEO-PPO-PEO induced holey NiFe-LDH nanosheets on Ni foam for efficient overall water-splitting and urea electrolysis.

Exploring the transition-metal-based bifunctional electrocatalysts with high performance for efficient water-splitting and urea electrolysis is significant but challenging. This work presents the in situ preparation of holey NiFe-LDH nanosheets on Ni foam (H-NiFe-LDH/NF) via a one-step hydrothermal method in the presence of PEO-PPO-PEO as the soft template. The holey NiFe-LDH nanosheets provide a high electrochemical surface area, more edge catalytic sites, and abundant oxygen vacancies. Consequently, H-NiFe-LDH/NF exhibits excellent catalytic activity to oxygen evolution, urea oxidation, and hydrogen evolution reactions (OER, UOR, and HER) with good stability in alkaline electrolytes. This electrode requires an overpotential of 261 mV for the OER, a potential of 1.480 V for the UOR to achieve a current density of 100 mA cm-2 in alkaline solutions. By employing the self-supported electrode as both the anode and cathode, this electrolysis cell (H-NiFe-LDH/NF||H-NiFe-LDH/NF) gains current densities of 10 and 100 mA cm-2 at low cell voltages of 1.575 and 1.933 V in the 1.0 M KOH solution. After adding 0.33 M urea, the voltages to deliver 10 and 100 mA cm-2 respectively decrease to 1.418 and 1.691 V. The H-NiFe-LDH/NF electrode also shows excellent stability for water-splitting and urea electrolysis. This work not only contributes to developing a low-cost, high-efficiency, bifunctional electrocatalyst but also provides a practically feasible approach for urea-rich wastewater electrolysis.

Polyaniline functionalized CoAl-layered double hydroxide nanosheets as a platform for the electrochemical detection of carbaryl and isoprocarb.

The preparation of the polyaniline/CoAl-layered double hydroxide composite (PANI/CoAl-LDH) is presented by ultrasonic mixing the uniform PANI- and CoAl-LDH-building blocks, both of which are synthesized in a microemulsion system. Due to the improved surface area, increased adsorptive and catalytic sites, and enhanced conductivity, the PANI/CoAl-LDH-modified glassy carbon electrode (GCE) delivers rapid electron-transfer and mass-transfer between the substrate electrode and analytes. Consequently, PANI/CoAl-LDH/GCE demonstrates outstanding electrocatalytic activity toward carbaryl and isoprocarb with good selectivity, stability, and reproducibility. The amperometric sensor gives rise to a wide linear range of 0.1 ~ 150 µM for both carbaryl and isoprocarb at 0.19 and 0.39 V (vs. SCE), respectively. Their limits of detection are respectively 6.8 and 8.1 nM. This sensor is successfully used for the determination of carbaryl and isoprocarb pesticides in real vegetable samples with a relative standard deviation below 4%.

Mixture Phases Engineering of PtFe Nanofoams for Efficient Hydrogen Evolution.

Phase engineering is a promising but challenging approach to construct PtFe-based catalysts with efficient hydrogen evolution reaction (HER) performance. Herein, the authors successfully synthesize PtFe nanofoams with face center cubic (fcc) phase, with simple cubic crystalline (scc) phase and with the mixture phases of fcc and scc phases (PtFe-mix) by hydrogen-assisted calcination for the first time. By benchmarking the HER activity, PtFe-mix exhibits excellent activity in 1.0 m KOH, requiring an overpotential of 28 mV to achieve 10 mA cm-2 , which is better than the commercial Pt/C (34 mV). PtFe-mix also possesses remarkable stability up to 24 h. Density functional theory calculations further verify that PtFe-mix shows a more suitable d-band center and lower energy barrier for the initial water dissociation, facilitating the HER process. This work provides a meaningful strategy to design PtFe-based catalysts with efficient activity for hydrogen evolution.

Electrodeposition of NiFe-layered double hydroxide layer on sulfur-modified nickel molybdate nanorods for highly efficient seawater splitting.

Developing high-efficiency and earth-abundant electrocatalysts for electrochemical seawater-splitting is of great significance but remains a grand challenge due to the presence of high-concentration chloride. This work presents the synthesis of a three-dimensional core-shell nanostructure with an amorphous and crystalline NiFe-layered double hydroxide (NiFe-LDH) layer on sulfur-modified nickel molybdate nanorods supported by porous Ni foam (S-NiMoO4@NiFe-LDH/NF) through hydrothermal and electrodeposition. Benefiting from high intrinsic activity, plentiful active sites, and accelerated electron transfer, S-NiMoO4@NiFe-LDH/NF displays an outstanding bifunctional catalytic activity toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in both simulated alkaline seawater and natural seawater electrolytes. To reach a current density of 100 mA cm-2, this catalyst only requires overpotentials of 273 and 315 mV for OER and 170 and 220 mV for HER in 1 M KOH + 0.5 M NaCl freshwater and 1 M KOH + seawater electrolytes, respectively. Using S-NiMoO4@NiFe-LDH as both anode and cathode, the electrolyzer shows superb overall seawater-splitting activity, and respectively needs low voltages of 1.68 and 1.73 V to achieve a current density of 100 mA cm-2 in simulated alkaline seawater and alkaline natural seawater electrolytes with good Cl- resistance and satisfactory durability. The electrolyzer outperforms the benchmark IrO2||Pt/C pair and many other reported bifunctional catalysts and exhibits great potential for realistic seawater electrolysis.

Solvent-free microwave synthesis of ultra-small Ru-Mo2C@CNT with strong metal-support interaction for industrial hydrogen evolution.

Exploring a simple, fast, solvent-free synthetic method for large-scale preparation of cheap, highly active electrocatalysts for industrial hydrogen evolution reaction is one of the most promising work today. In this work, a simple, fast and solvent-free microwave pyrolysis method is used to synthesize ultra-small (3.5 nm) Ru-Mo2C@CNT catalyst with heterogeneous structure and strong metal-support interaction in one step. The Ru-Mo2C@CNT catalyst only exhibits an overpotential of 15 mV at a current density of 10 mA cm-2, and exhibits a large turnover frequency value up to 21.9 s-1 under an overpotential of 100 mV in 1.0 M KOH. In addition, this catalyst can reach high current densities of 500 mA cm-2 and 1000 mA cm-2 at low overpotentials of 56 mV and 78 mV respectively, and it displays high stability of 1000 h. This work provides a feasible way for the reasonable design of other large-scale production catalysts.

Cu2Se nanowires shelled with NiFe layered double hydroxide nanosheets for overall water-splitting.

It is imperative but challenging to develop non-noble metal-based bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Our work reports a core-shell nanostructure that is constructed by the electrodeposition of ultrathin NiFe-LDH nanosheets (NiFe-LDHNS) on Cu2Se nanowires, which are obtained by selenizing Cu(OH)2 nanowires in situ grown on Cu foam. The obtained Cu2Se@NiFe-LDHNS electrocatalyst provides more exposed edges and catalytic active sites, thus exhibiting excellent OER and HER electrocatalytic performance in alkaline electrolytes. This catalyst needs only an overpotential of 197 mV for OER at 50 mA cm-2 and 195 mV for HER at 10 mA cm-2. Besides, when employed as a bifunctional catalyst for overall water-splitting, it requires a cell voltage of 1.67 V to reach 10 mA cm-2 in alkaline media. Furthermore, the corresponding water electrolyzer demonstrates robust durability for at least 40 h. The excellent performance of Cu2Se@NiFe-LDHNS might be ascribed to the synergistic effect from the ultrathin NiFe-LDHNS, the Cu2Se nanowires anchored on the Cu foam, and the formed core-shell nanostructure, which offers large surface area, ample active sites, and sufficient channels for gas and electrolyte diffusion. This work provides an efficient strategy for the fabrication of self-supported electrocatalysts for efficient overall water-splitting.

Electrochemical sensing for naphthol isomers based on the in situ growth of zeolitic imidazole framework-67 on ultrathin CoAl layered double hydroxide nanosheets by a reaction-diffusion technique.

It is established that ultrathin layered double hydroxide nanosheets (LDHNS) and zeolitic imidazole frameworks (ZIF) are desirable electrochemical sensing modifiers owing to their large surface area and abundant catalytic sites. Integration of them is thus an effective solution to maximize their electrocatalytic activity. Herein, a novel reaction-diffusion framework (RDF) technique is applied for the in situ growth of ZIF-67 on ultrathin CoAl-LDHNS (CoAl-LDHNS@ZIF-67). In a confined space of the agar gel matrix of RDF, the coordination reaction between organic ligands and CoAl-LDHNS without an additional Co2+ source achieves the controllable growth of ZIF-67 crystals through a long vertical diffusion. The prepared composite comprises both CoAl-LDHNS and ZIF-67 components with a certain ratio and provides a large surface area and amply catalytic sites, thus realizing a rapid transfer of electron and mass. The CoAl-LDHNS@ZIF-67 modified electrode is employed for the simultaneous detection of naphthol isomers by differential pulse voltammetry. Naphthol isomers display anodic reactions with a wide peak potential difference, allowing their simultaneous detection feasible. Voltammetric responses of α-naphthol and ß-naphthol follow good linearity against the concentration in a wide range from 0.3 to 150 µM with limits of detection of 54 and 82 nM, respectively. The proposed sensor also demonstrates excellent selectivity, stability, reproducibility, and practicability for the simultaneous detection of naphthol isomers.

Size-dependent light scattering of CoOOH nanoflakes for convenient and sensitive detection of alkaline phosphatase in human serum.

As a natural enzyme, alkaline phosphatase (ALP) plays an essential role in clinicopathological examinations and biomedical research, and is capable of hydrolyzing the phosphate group of l-ascorbic acid-2-phosphate (AAP) to yield l-ascorbic acid (L-AA). L-AA reduced cobalt oxyhydroxide (CoOOH) nanoflakes to Co2+ , leading to a smaller size and weaker light scattering, which could be monitored by electron microscopic images and optical spectra. The indirect detection of ALP was achieved by the reduced light scattering signal of CoOOH nanoflakes. Under optimal conditions, the decrease in scattering intensity was proportional to the ALP concentration over the range 0.1-160 U/L and the detection limit was 0.034 U/L (3σ/k). Compared with other assays, this proposed light scattering method was more convenient and economic for ALP sensing. The method was successfully applied to ALP analysis in human serum samples, and was similar to the results obtained by commercial kits.

Size-modulated optical property of gold nanorods for sensitive and colorimetric detection of thiourea in fruit juice.

As an important sulfur compound, thiourea (TU) has caused great concern because of its wide application as well as its serious toxicity and hazard to the environment. Thus, it is necessary to develop a sensitive and selective method for TU analysis. In this work, gold nanorods (AuNRs) acted as an optical probe to realize the sensitive and colorimetric detection of TU. In HCl medium, Fe3+ at low concentration was difficult to oxide Au0 to form Au+ because of the high redox potential or the positive Gibbs free energy change. However, this process was possible when TU was present since the association constant between Au+ and TU is great enough to bind with TU to form a stable complex to further promote the etching of AuNRs, resulting in the lower aspect ratio of AuNRs with the blue shift and intensity decrease in extinction spectra, accompanied by the divisive colors of AuNRs solution or colorful dark-field light scattering imaging of single AuNR. The blue-shift of AuNRs longitudinal plasmon resonance absorption (LPRA) band was proportional to the concentration of TU in the range of 1-250 nM and the limit of detection (3σ/k) was as low as 0.4 nM. In addition, the colorimetric method was proven with high selectivity in the presence of potential interfering compounds, which was successfully applied to the detection of TU in fruit juice samples. This proposed colorimetric method provides a simple, sensitive yet selective measurement tool for TU sensing, which may offer new opportunities in the development of colorimetric sensors for food safety in the future.

Electrochemical sensing platform for naphthol isomers based on in situ growth of ZIF-8 on reduced graphene oxide by a reaction-diffusion technique.

Enhancing the dispersibility and conductivity is an effective solution to develop the application zeolitic imidazole frameworks (ZIF) in the electrochemical field. This work thus employs a novel reaction-diffusion framework (RDF) technique for the in situ growth of ZIF-8 crystals on graphene oxide (GO@ZIF-8) matrixes. In detail, the outer electrolyte of 2-methyl imidazole naturally diffuses into the inner agar gel matrix containing Zn2+ cations and GO nanosheets. The long reaction-diffusion makes the growth of ZIF-8 crystals controllable in a vertical gradient. After thermal treatment, the title product of ZIF-8 in situ grown on reduced graphene oxide (rGO@ZIF-8) is obtained and thus exhibits good dispersibility, high conductivity, large surface area, and more catalytic sites. The glassy carbon electrode (GCE) was modified by casting the rGO@ZIF-8 suspension. The obtained rGO@ZIF-8/GCE displays excellent catalytic activity toward naphthol (NAP) isomers. Under the optimal conditions, the amperometric currents of 1-NAP and 2-NAP demonstrate the good linear relationship in wide ranges of 0.05-12 µM and 0.02-15 µM, respectively. Their limits of detection are as low as 15 and 17 nM, respectively. The fabricated modified electrode exhibits excellent selectivity, stability, and reproducibility. The sensor is also utilized to detect NAP molecules in real water samples and indicates good accuracy and reliability.

Aqueous photodegradation of okadaic acid and dinophysistoxin-1: Persistence, kinetics, photoproducts, pathways, and toxicity evaluation.

Diarrhetic shellfish poisoning (DSP) toxins are a class of natural organic contaminants that pose a serious threat not only to marine ecosystems and fisheries but also to human health. They are widely distributed in coastal and offshore waters around the world. However, the persistence and photochemical degradation characteristics of DSP in an aqueous environment are still unclear. This study aimed to elucidate the photochemical fate of two representative DSP toxins, namely, okadaic acid (OA) and dinophysistoxin-1 (DTX1). Results showed that photo-mediated chemical reactions play a crucial role in eliminating DSP toxins in seawater. However, the degradation of OA and DTX1 was relatively slow under natural solar radiation, with a removal efficiency of 90.0% after exposure for more than 20 days. When the reaction solutions of OA and DTX1 were exposed to Hg lamp radiation, their degradation followed pseudo-first-order kinetics, and was remarkably influenced by seawater pH and metal-ion concentration. A total of 24 tentative transformation products (TPs) of OA and DTX1 were identified via liquid chromatography high-resolution mass spectrometry. C12 (C43H66O11) and C24 (C44H68O11) were the main TPs. The following possible photodegradation pathways were proposed: decarboxylation, photoinduced hydrolysis, chain scission, and photo-oxidation. Toxicity assays via protein phosphatase 2A inhibition proved that photochemical processes could significantly reduce the DSP toxicity of irradiated solutions by approximately 88%. This work provides an enhanced understanding of the fate of DSP toxins in the aqueous environment, allowing for an improved assessment of their environmental impacts.