Degradation and detoxification mechanisms of organophosphorus flame retardant tris(1,3-dichloro-2-propyl) phosphate (TDCPP) during electrochemical oxidation process

Electrochemical oxidation of aqueous tris(1,3-dichloro-2-propyl) phosphate (TDCPP) by using Ti/SnO₂-Sb/La-PbO₂ as anode was investigated for the first time, and the degradation mechanisms and toxicity changes of the degradation intermediates were further determined. Results suggested that electrochemical degradation of TDCPP followed pseudo-first-order kinetics, and the reaction rate constant (k) was 0.0332 min⁻¹ at the applied current density of 10 mA/cm² and Na₂SO₄ concentration of 10 mmol/L. There was better TDCPP degradation performance at higher current density. Free hydroxy radical (^•OH) was proved to play dominant role in TDCPP oxidation via quenching experiment, with a relative contribution rate of 60.1%. A total of five intermediates (M1, C₆H₁₁Cl₄O₄P; M2, C₃H₇Cl₂O₄P; M3, C₉H₁₆Cl₅O₅P; M4, C₉H₁₄Cl₅O₆P; M5, C₆H₁₀Cl₃O₆P) were identified, and the intermediates were further degraded prolonging with the reaction time. Flow cytometer results suggested that the toxicity of TDCPP and degradation intermediates significantly reduced, and the detoxification efficiency was achieved at 78.1% at 180 min. ECOSAR predictive model was used to assess the relative toxicity of TDCPP and the degradation intermediates. The EC₅₀ to green algae was 3.59 mg/L for TDCPP, and the values raised to 84, 574, 54.6, 391, and 8920 mg/L for M1, M2, M3, M4, and M5, respectively, indicating that the degradation intermediates are less toxic or not toxic. Electrochemical advanced oxidation process is a valid technology to degrade TDCPP and pose a good detoxification effect.     

The introduction of cobalt element into nickel-organic framework for enhanced supercapacitive performance

Metal-organic frameworks (MOFs) as promising electrodes for supercapacitors are attracting increasing research interest. Herein, we report an effective strategy to improve the electrochemical performance of Ni-MOF for supercapacitor by introducing a secondary Co ion. The Co substitution of Ni in Ni-MOF can improve the intrinsic reactivity and stability. As a result, the bimetallic Co/Ni-MOF-1:15 with an optimal Co/Ni ratio delivers high specific capacitance (359 F/g at 0.5 A/g), good rate performance (81.5% retention at 5 A/g) and cycling stability (81% retention after 5000 cycles). These results demonstrate that the bimetallic synergistic strategy is an effective way to improve the pseudocapacitive performance of MOFs.     

Synergistic Pd/Cu-catalyzed regio- and stereoselective cascade Heck cyclization/borylation/cross-coupling

A cooperative Pd/Cu-catalyzed three-component cross-coupling reaction of alkynes, B₂Pin₂ and alkene-tethered aryl halides is reported. This reaction proceeds under mild conditions and shows broad substrate scope, providing a variety of heterocycles containing tetrasubstituted alkenylboronate moieties in synthetically useful yields with excellent chemoselectivity and regioselectivity. This transformation features the catalytic generation of β-borylalkenylcopper intermediates and their use in Pd-catalyzed Heck cyclization/cross-couplings. An enantioselective cascade cyclization/cross-coupling process has also been developed for the synthesis of enantiomerically enriched oxindole bearing a tetrasubstituted alkenylboronate moiety.     

Durable Electrocatalytic Reduction of Nitrate to Ammonia over Defective Pseudobrookite Fe2TiO5 Nanofibers with Abundant Oxygen Vacancies

We propose the pseudobrookite Fe₂TiO₅ nanofiber with abundant oxygen vacancies as a new electrocatalyst to ambiently reduce nitrate to ammonia. Such catalyst achieves a large NH₃ yield of 0.73 mmol h⁻¹ mg⁻¹_cat. and a high Faradaic Efficiency (FE) of 87.6 % in phosphate buffer saline solution with 0.1 M NaNO₃, which is lifted to 1.36 mmol h⁻¹ mg⁻¹_cat. and 96.06 % at −0.9 V vs. RHE for nitrite conversion to ammonia in 0.1 M NaNO₂. It also shows excellent electrochemical durability and structural stability. Theoretical calculation reveals the enhanced conductivity of this catalyst and an extremely low free energy of −0.28 eV for nitrate adsorption at the presence of vacant oxygen.     

Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co9S8/Co3S4/Cu2S Nanohybrids

The rational design of advanced nanohybrids (NHs) with optimized interface electronic environment and rapid reaction kinetics is pivotal to electrocatalytic schedule. Herein, we developed a multiple heterogeneous Co₉S₈/Co₃S₄/Cu₂S nanoparticle in which Co₃S₄ germinates between Co₉S₈ and Cu₂S. Using high-angle annular-dark-field imaging and theoretical calculation, it was found that the integration of Co₉S₈ and Cu₂S tends to trigger the interface phase transition of Co₉S₈, leading to Co₃S₄ interlayer due to the low formation energy of Co₃S₄/Cu₂S (−7.61 eV) than Co₉S₈/Cu₂S (−5.86 eV). Such phase transition not only lowers the energy barrier of oxygen evolution reaction (OER, from 0.335 eV to 0.297 eV), but also increases charge carrier density (from 7.76×10¹⁴ to 2.09×10¹⁵ cm⁻³), and creates more active sites. Compared to Co₉S₈ and Cu₂S, the Co₉S₈/Co₃S₄/Cu₂S NHs also demonstrate notable photothermal effect that can heat the catalyst locally, offset the endothermic enthalpy change of OER, and promote carrier migrate, reaction intermediates adsorption/deprotonation to improve reaction kinetics. Profiting from these favorable factors, the Co₉S₈/Co₃S₄/Cu₂S catalyst only requires an OER overpotential of 181 mV and overall water splitting cell voltage of 1.43 V to driven 10 mA cm⁻² under the irradiation of near-infrared light, outperforming those without light irradiation and many reported Co-based catalysts.     

Nafion covered core–shell structured Fe3O4@graphene nanospheres modified electrode for highly selective detection of dopamine

Nafion covered core–shell structured Fe₃O₄@graphene nanospheres (GNs) modified glassy carbon electrode (GCE) was successfully prepared and used for selective detection dopamine. Firstly, the characterizations of hydro-thermal synthesized Fe₃O₄@GNs were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Then Fe₃O₄@GNs/Nafion modified electrode exhibited excellent electrocatalytic activity toward the oxidations of dopamine (DA). The interference test showed that the coexisted ascorbic acid (AA) and uric acid (UA) had no electrochemical interference toward DA. Under the optimum conditions, the broad linear relationship was obtained in the experimental concentration from 0.020 μM to 130.0 μM with the detection limit (S/N = 3) of 0.007 μM. Furthermore, the core–shell structured Fe₃O₄@GNs/Nafion/GCE was applied to the determination of DA in real samples and satisfactory results were got, which could provide a promising platform to develop excellent biosensor for detecting DA.     

Surface‐Enhanced Raman Scattering Based on Controllable‐Layer Graphene Shells Directly Synthesized on Cu Nanoparticles for Molecular Detection

Graphene shells with a controllable number of layers were directly synthesized on Cu nanoparticles (CuNPs) by chemical vapor deposition (CVD) to fabricate a graphene‐encapsulated CuNPs (G/CuNPs) hybrid system for surface‐enhanced Raman scattering (SERS). The enhanced Raman spectra of adenosine and rhodamine 6G (R6G) showed that the G/CuNPs hybrid system can strongly suppress background fluorescence and increase signal‐to‐noise ratio. In four different types of SERS systems, the G/CuNPs hybrid system exhibits more efficient SERS than a transferred graphene/CuNPs hybrid system and pure CuNPs and graphene substrates. The minimum detectable concentrations of adenosine and R6G by the G/CuNPs hybrid system can be as low as 10^?8 and 10^?10 M , respectively. The excellent linear relationship between Raman intensity and analyte concentration can be used for molecular detection. The graphene shell can also effectively prevent surface oxidation of Cu nanoparticles after exposure to ambient air and thus endow the hybrid system with a long lifetime. This work provides a basis for the fabrication of novel SERS substrates.     

Simultaneous photoelectrochemical detection of dual microRNAs by capturing CdS quantum dots and methylene blue based on target-initiated strand displaced amplification

Herein,we propose a novel photoelectrochemical(PEC) biosensor for dual microRNAs(miRNAs) highly sensitive and simultaneous biosensing based on strand displaced amplification(SDA) reaction.The recognition of H_(miR-21) and H_(let-7 a) by microRNA-21 and let-7 a leads to their change in hairpin structures,subsequently initiating the immobilization of abundant CdS quantum dots(CdS QD s) and methylene blue(MB) based on SDA reaction.The immobilized CdS QDs and MB produce both high PEC currents under430 nm light and 627 nm light illumination,respectively,and the generated PEC currents are closely relied on target miRNAs amounts.Thus,highly sensitive and simultaneous detection of microRNA-21 and let-7 a was readily achieved with detection limit at 6.6 fmol/L and 15.4 fmol/L based on 3σ,respectively.Further,this PEC biosensor was applied in simultaneous analysis of miRNA-21 and let-7 a in breast cancer patient's serum with acceptable results.We expect this biosensor will find more useful application in diagnosis of miRNA-related diseases.