In situ anchored ternary hierarchical hybrid nickel@cobaltous sulfide on poly(3,4-ethylenedioxythiophene)-reduced graphene oxide for highly efficient non-enzymatic glucose sensing.

A ternary hierarchical hybrid Ni@CoxSy/poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (Ni@CoxSy/PEDOT-rGO) is rationally designed and in situ facilely synthesized as electrocatalyst to construct a binder-free sensing platform for non-enzymatic glucose monitoring through traditional electrodeposition procedure. The as-prepared Ni@CoxSy/PEDOT-rGO presents unique hierarchical structure and multiple valence states as well as strong and robust adhesion between Ni@CoxSy/PEDOT-rGO and GCE. Profiting from the aforementioned merits, the sensing platform constructed under optimal conditions achieved a wide detection range (0.2 µM ~ 2.0 mM) with high sensitivity (1546.32 µA cm-2 mM-1), a rapid response time (5 s), an ultralow detection limit (0.094 µM), superior anti-interference performance, excellent reproducibility and considerable stability. Furthermore, the sensor demonstrates an acceptable accuracy and appreciable recoveries ranging from 90.0 to 102.0% with less than 3.98% RSD in human blood serum samples, indicating the prospect of the sensor for the real samples analysis. It will provide a strategy to rationally design and fabricate ternary hierarchical hybrid as nanozyme for glucose assay.

Enhanced Spin-Polarized Electric Field Modulating p-Band Center on Ni-Doped CdS for Boosting Photocatalytic Hydrogen Evolution.

It is a challenge to regulate charge separation dynamics and redox reaction kinetics at the atomic level to synergistically boost photocatalytic hydrogen (H2 ) evolution. Herein, a robust Ni-doped CdS (Ni-CdS) photocatalyst is synthesized by incorporating highly dispersed Ni atoms into the CdS lattice in substitution for Cd atoms. Combined characterizations with theoretical analysis indicate that local lattice distortion and S-vacancy of Ni-CdS induced by Ni incorporation lead to an increased dipole moment and enhanced spin-polarized electric field, which promotes the separation and transfer of photoinduced carriers. In this contribution, charge redistribution caused by enhanced internal electric field results in the downshift of the S p-band center, which is conducive to the desorption of intermediate H* for boosting the H2 evolution reaction. Accordingly, the Ni-CdS photocatalyst shows a remarkably improved photocatalytic performance with an H2 evolution rate of 20.28 mmol g-1  h-1 under visible-light irradiation, which is 5.58 times higher than that of pristine CdS. This work supplied an insightful understanding that the enhanced polarization electric field governs the p-band center for efficient photocatalytic H2 evolution activity.

Effectively Modulating Oxygen Vacancies in Flower-Like δ-MnO2 Nanostructures for Large Capacity and High-Rate Zinc-Ion Storage.

In recent years, manganese-based oxides as an advanced class of cathode materials for zinc-ion batteries (ZIBs) have attracted a great deal of attentions from numerous researchers. However, their slow reaction kinetics, limited active sites and poor electrical conductivity inevitably give rise to the severe performance degradation. To solve these problems, herein, we introduce abundant oxygen vacancies into the flower-like δ-MnO2 nanostructure and effectively modulate the vacancy defects to reach the optimal level (δ-MnO2-x-2.0). The smart design intrinsically tunes the electronic structure, guarantees ion chemisorption-desorption equilibrium and increases the electroactive sites, which not only effectively accelerates charge transfer rate during reaction processes, but also endows more redox reactions, as verified by first-principle calculations. These merits can help the fabricated δ-MnO2-x-2.0 cathode to present a large specific capacity of 551.8 mAh g-1 at 0.5 A g-1, high-rate capability of 262.2 mAh g-1 at 10 A g-1 and an excellent cycle lifespan (83% of capacity retention after 1500 cycles), which is far superior to those of the other metal compound cathodes. In addition, the charge/discharge mechanism of the δ-MnO2-x-2.0 cathode has also been elaborated through ex situ techniques. This work opens up a new pathway for constructing the next-generation high-performance ZIBs cathode materials.

Intensifying Electrochemical Activity of Ti3C2Tx MXene via Customized Interlayer Structure and Surface Chemistry.

MXene, a new intercalation pseudocapacitive electrode material, possesses a high theoretical capacitance for supercapacitor application. However, limited accessible interlayer space and active sites are major challenges to achieve this high capacitance in practical application. In order to stimulate the electrochemical activity of MXene to a greater extent, herein, a method of hydrothermal treatment in NaOH solution with reducing reagent-citric acid is first proposed. After this treatment, the gravimetric capacitance of MXene exhibits a significant enhancement, about 250% of the original value, reaching 543 F g-1 at 2 mV s-1. This improved electrochemical performance is attributed to the tailoring of an interlayer structure and surface chemistry state. An expanded and homogenized interlayer space is created, which provides enough space for electrolyte ions storage. The -F terminations are replaced with O-containing groups, which enhances the hydrophilicity, facilitating the electrolyte's accessibility to MXene's surface, and makes MXene show stronger adsorption for electrolyte ion-H+, providing sufficient electrochemical active sites. The change in terminations further leads to the increase in Ti valence, which becomes more prone to reduction. This work establishes full knowledge of the rational MXene design for electrochemical energy storage applications.

Phosphorus Doping Strategy-Induced Synergistic Modification of Interlayer Structure and Chemical State in Ti3C2Tx toward Enhancing Capacitance.

Heteroatom doping is considered an effective method to substantially improve the electrochemical performance of Ti3C2Tx MXene for supercapacitors. Herein, a facile and controllable strategy, which combines heat treatment with phosphorous (P) doping by using sodium phosphinate (NaH2PO2) as a phosphorus source, is used to modify Ti3C2Tx. The intercalated ions from NaH2PO2 act as "pillars" to expand the interlayer space of MXene, which is conducive to electrolyte ion diffusion. On the other hand, P doping tailors the surface electronic state of MXene, optimizing electronic conductivity and reducing the free energy of H+ diffusion on the MXene surface. Meanwhile, P sites with lower electronegativity owning good electron donor characteristics are easy to share electrons with H+, which is beneficial to charge storage. Moreover, the adopted heat treatment replaces -F terminations with O-containing groups, which enhances the hydrophilicity and provides sufficient active sites. The change in surface functional groups increases the content of high valence-stated Ti with a high electrochemical activity that can accommodate more electrons during discharge. Synergistic modification of interlayer structure and chemical state improves the possibility of Ti3C2Tx for accommodating more H+ ions. Consequently, the modified electrode delivers a specific capacitance of 510 F g-1 at 2 mV s-1, and a capacitance retention of 90.2% at 20 A g-1 after 10,000 cycles. The work provides a coordinated strategy for the rational design of high-capacitance Ti3C2Tx MXene electrodes.

Janus Z-scheme heterostructure of ZnIn2S4/MoSe2/In2Se3 for efficient photocatalytic hydrogen evolution.

Artificial manipulation of charge separation and transfer are central issues dominating hydrogen evolution reaction triggered via photocatalysis. Herein, through elaborate designing on the architecture, band alignment, and interface bonding mode, a sulfur vacancy-rich ZnIn2S4-based (Vs-ZIS) multivariate heterostructure ZnIn2S4/MoSe2/In2Se3 (Vs-ZIS/MoSe2/In2Se3) with specific Janus Z-scheme charge transfer mechanism is constructed through a two-step hydrothermal process. Steering by the Janus Z-scheme charge transfer mechanism, photogenerated electrons in the conduction band of MoSe2 transfer synchronously to the valence band of Vs-ZIS and In2Se3, resulting in abundant highly-active photogenerated electrons reserved in the conduction band of Vs-ZIS and In2Se3, therefore significantly enhancing the photocatalytic activity of hydrogen evolution. Under visible light irradiation, the optimized Vs-ZIS/MoSe2/In2Se3 with the mass ratio of MoSe2 and In2Se3 to ZnIn2S4 at 3 % and 30 %, respectively, performs a high hydrogen evolution rate of 124.42 mmol·g-1·h-1, about 43.5-folds of the original ZIS photocatalyst. Besides, an apparent quantum efficiency (AQE) of 22.5 % at 420 nm and favorable durability are also achieved over Vs-ZIS/MoSe2/In2Se3 photocatalyst. This work represents an important development in efficient photocatalysts and donates a sound foundation for the design of regulating charge transfer pathways.

Graphene oxide membrane chemically modified by electron-transfer diazonium chemistry for efficient dye separation.

By chemical modification of the graphene oxide (GO) surface via diazonium chemistry, we introduce nitrobenzene groups as new interlayer pillars to GO memebranes like the surface oxygen-containing functional groups. The larger pillar can finely enlarge the interlayer space of the GO membrane. The filtration performance of modified GO membranes with different mass ratios of nitrobenzene diazonium tetrafluoroborate (NDT) were tested for EB, DR81, and MB. Notably, when the GO : NDT ratio is 1 : 1, it is found that the water flux can be enhanced by more than twice and by nearly 1.4 times its value for EB and DR81, respectively, while maintaining a high rejection (92% for EB and 95% for DR81). In conclusion, the chemical modification of GO through the dediazonization reaction of NDT can indeed improve the separation efficiency of the dye.

An Equivalent Substitute Strategy for Constructing 3D Ordered Porous Carbon Foams and Their Electromagnetic Attenuation Mechanism.

Three-dimensional (3D) ordered porous carbon is generally believed to be a promising electromagnetic wave (EMW) absorbing material. However, most research works targeted performance improvement of 3D ordered porous carbon, and the specific attenuation mechanism is still ambiguous. Therefore, in this work, a novel ultra-light egg-derived porous carbon foam (EDCF) structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process. Based on an equivalent substitute strategy, the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres. As a primary attenuation mode, the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band, and the value is dominated by polarization loss in X band and Ku band, which is obviously greater than that of conduction loss. Furthermore, in all samples, the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%, covering the whole Ku band. Meanwhile, the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss (RLmin) of - 58.08 dB at 16.86 GHz while the thickness is 1.27 mm. The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments.

Interfacial Engineering and a Low-Crystalline Strategy for High-Performance Supercapacitor Negative Electrodes: Fe2P2O7 Nanoplates Anchored on N/P Co-doped Graphene Nanotubes.

Developing novel hybrid negative electrode materials with high specific capacity, rate capacitance, and long-term cycle stability is a key factor for pushing large-scale application of supercapacitors. However, construction of robust interfaces and low-crystalline active materials plays a crucial role in realizing the target. In this paper, a one-step phosphorization approach was employed to make low-crystalline Fe2P2O7 nanoplates closely bonded to N/P-co-doped graphene nanotubes (N/P-GNTs@b-Fe2P2O7) through interfacial chemical bonding. The N and P heteroatoms as substitutions for C in GNT skeletons can introduce rich electronic centers, which induces Fe2P2O7 to fix the surface of N/P-GNTs through Fe-N and Fe-P bonds as confirmed by the characterizations. Moreover, the low-crystalline active materials own a disordered internal structure and numerous defects, which not only endows with excellent conductivity but also provides many active sites for redox reactions. Benefiting from the synergistic effects, the prepared N/P-GNTs@b-Fe2P2O7 can not only deliver a high capacity of 257 mA h g-1 (927 F g-1) at 1 A g-1 but also present an excellent rate capability of 184 mA h g-1 (665 F g-1) at 50 A g-1 and outstanding cycle stability (∼90.6% capacity retention over 40,000 cycles). Furthermore, an asymmetric supercapacitor was assembled using the obtained N/P-GNTs@b-Fe2P2O7 as electrode materials, which can present the energy density as high as 83.3 W h kg-1 at 791 W kg-1 and long-term durability. Therefore, this strategy not only offers an effective pathway for achieving high-performance negative electrode materials but also lays a foundation for further industrialization.

Curly fish scales-like Ni2.5Mo6S6.7 electrodeposited on PEDOT-rGO with uneven surface as ultrafast response electrode for electrocatalytic glucose, nitrite and hydrogen peroxide.

The difficulty to achieve rapid detection is the limitation of many enzyme-free sensors today. Thus, designing tri-functionalsensors with ultra-fast and efficientdeterminationis a challenging taskin biological science. Herein, curly fish scales-like Ni2.5Mo6S6.7 active materials was anchored on poly (3,4-ethylenedioxythiophene)-reduced graphene oxide (PEDOT-rGO) hybrid membranes with uneven surface (Ni2.5Mo6S6.7/PEDOT-rGO) as a high-performance tri-functional catalyst for glucose, nitrite and hydrogen peroxide determination.The sensor constructed under optimal conditions exhibited ultrafast response performance towards glucose and nitrite within 2 s, and hydrogen peroxide within 1 s. Meanwhile, it provided the wide linear range with a low detection limit towards glucose (as low as 0.001 mM and up to 15.000 mM, and 0.33 µM), nitrite (as low as 0.001 mM and up to 10.000 mM, and 0.33 µM) and hydrogen peroxide (from 0.010 mM to 7.000 mM, and 0.79 µM), respectively. In addition, the sensor demonstrated satisfied selectivity, repeatability, reproducibility and stability. Furthermore, the sensor has potential application in real samples. This study may provide a new strategy for the construction of tri-functional electrode materials with the ultra-fast response.

Synergy Strategy of Electrical Conductivity Enhancement and Vacancy Introduction for Improving the Performance of VS4 Magnesium-Ion Battery Cathode.

The development of cathode materials with a high electric conductivity and a low polarization effect is crucial for enhancing the electrochemical properties of magnesium-ion batteries (MIBs). Herein, Mo doping and nitrogen-doped tubular graphene (N-TG) introduction are carried out for decorating VS4 (Mo-VS4/N-TG) via the one-step hydrothermal method as a freestanding cathode for MIBs. The results of characterizations and density functional theory (DFT) reveal that rich sulfur vacancies are induced by Mo doping, and N-TG as a high conductive skeleton material serves to disperse the active material and forms a tight connection, all of which collectively improved the electrical conductivity of electrode and increased the adsorption energy of Mg2+ (-6.341 eV). Furthermore, the fast reaction kinetics is also confirmed by the galvanostatic intermittent titration technique (GITT) and the pesudocapacitance-like contribution analysis. Benefiting from the synergistic effect of electrical conductivity enhancement and rich vacancy introduction, Mo-VS4/N-TG delivers a steady Mg2+ storage specific capacity of about 140 mAh g-1 at 50 mA g-1, outstanding cycle stability (80.6% capacity retention ratio after 1200 cycles under 500 mA g-1), and excellent rate capability (specific capacity reaches 77.1 mAh g-1 when the current density reaches 500 mA g-1). In addition, the reversible reaction process, intercalation mechanism, and structural stability during the Mg2+ insertion/extraction process are confirmed by a series of ex situ characterizations. This research provides a sustainable and scalable strategy to spur the development of MIBs.

Interfacial chemical bond and internal electric field modulated Z-scheme Sv-ZnIn2S4/MoSe2 photocatalyst for efficient hydrogen evolution.

Construction of Z-scheme heterostructure is of great significance for realizing efficient photocatalytic water splitting. However, the conscious modulation of Z-scheme charge transfer is still a great challenge. Herein, interfacial Mo-S bond and internal electric field modulated Z-scheme heterostructure composed by sulfur vacancies-rich ZnIn2S4 and MoSe2 was rationally fabricated for efficient photocatalytic hydrogen evolution. Systematic investigations reveal that Mo-S bond and internal electric field induce the Z-scheme charge transfer mechanism as confirmed by the surface photovoltage spectra, DMPO spin-trapping electron paramagnetic resonance spectra and density functional theory calculations. Under the intense synergy among the Mo-S bond, internal electric field and S-vacancies, the optimized photocatalyst exhibits high hydrogen evolution rate of 63.21 mmol∙g-1·h-1 with an apparent quantum yield of 76.48% at 420 nm monochromatic light, which is about 18.8-fold of the pristine ZIS. This work affords a useful inspiration on consciously modulating Z-scheme charge transfer by atomic-level interface control and internal electric field to signally promote the photocatalytic performance.

Molybdenum sulfide-modified metal-free graphitic carbon nitride/black phosphorus photocatalyst synthesized via high-energy ball-milling for efficient hydrogen evolution and hexavalent chromium reduction.

Improving the photocatalytic property of metal-free photocatalyst is still a challenging work. Herein, a novel high-efficiency molybdenum sulfide (MoS2)-modified metal-free graphitic carbon nitride (g-C3N4)/black phosphorus (BP) photocatalyst (MCN/BP/MS) was synthesized on a large scale via high-energy ball milling process. The optimized MCN/BP/MS exhibits the excellent hydrogen evolution rate of 2146.8 µmol·g-1·h-1, and hexavalent chromium (Cr(Ⅵ)) reduction activity with an apparent rate constant of 0.1464 min-1 and a degradation rate of 100% in 25 min. Detailed characterizations and mechanism research verified that the significantly improved photocatalytic activity of MCN/BP/MS mainly profited from the matched band structure, enhanced light absorption, intense interface contact, as well as the type-Ⅰ/Z hybrid charge transfer mechanism, which gave rise to a consecutive multistep charge migration, thus the photocarriers transfer and separation can be greatly promoted, and the photogenerated electrons with high reducing capacity can be preserved. This work not only provides a high-efficiency g-C3N4-based noble-metal-free photocatalyst, but also affords a beneficial inspiration for improving the photocatalytic property of the metal free photocatalyst.

Nickel sulfide nanoworm network architecture as a binder-free high-performance non-enzymatic glucose sensor.

Nickel sulfide nanoworm (Ni3S2 NW) network architecture was directly grown on the poly (3,4-ethylenedioxythiophene)-reduced graphene oxide hybrid films (PEDOT-rGO HFs) modified on glassy carbon electrode (GCE), acting as a binder-free sensor for high-performance non-enzymatic glucose monitoring. The sensor exhibited the satisfactory sensitivity (2123 µA mM-1 cm-2), wide linear range (15~9105 µM), low detection limit (0.48 µM), and rapid response time (< 1.5 s) at a potential of 0.5 V (vs. SCE) in 0.1 M NaOH and possessed good selectivity, reproducibility, and stability. The enhanced electrocatalytic activity of the sensor towards glucose oxidation was attributed to the particular morphology, satisfying hydrophilic nature, strong combination between Ni3S2 NWs, PEDOT-rGO, and bare GCE. Moreover, it can be used for assaying glucose in human serum samples without dilution, indicating potential for clinical diagnostic applications. Graphical abstract Nickel sulfide nanoworms (Ni3S2 NWs)/poly (3,4-ethylenedioxythiophene)-reduced graphene oxide hybrid films (PEDOT-rGO HFs) were used to construct a binder-free high-performance non-enzymatic glucose sensor with satisfactory sensitivity, wide linear range, low detection limit, good selectivity, amazing reproducibility, and stability.

Sulfur vacancies and morphology dependent sodium storage properties of MoS2-x and its sodiation/desodiation mechanism.

Creating rich vacancies and designing distinct micro-morphology are considered as effective strategies for boosting the electrochemical performances of sodium ion battery (SIB) electrode materials. In this paper, a variety of MoS2 nanostructures with different sulfur vacancies concentration and morphologies are successfully constructed by a hydrothermal method combined with various-temperature calcination treatment in a Ar/H2 mixed atmosphere. Employed as a free-standing anode for SIBs, the flower-like MoS2-x microspheres assembled by the intertwined nanosheet arrays (MoS2-x-800) delivers highest specific capacity of 525.3 mAh g-1 and rate capability, as well as extraordinarily stable cycle life with almost no loss of capacity after 420 cycles. The favorable sodium storage properties are mainly ascribed to the cooperated effects of superior intrinsic conductivity and richer active sites generated by sulfur vacancies, and numerous interspace achieved by the intersection of neighbouring nanosheets. Meanwhile, through ex situ analyses, the reversible charge/discharge mechanism of the obtained MoS2-x-800 is revealed reasonably. This work not only brings new insights into the design of high-performance electrode materials for SIBs, but also makes a great step forward in the practical applications of transition metal sulfides in energy storage systems.

Amorphous nickel sulfide nanoparticles anchored on N-doped graphene nanotubes with superior properties for high-performance supercapacitors and efficient oxygen evolution reaction.

The rational design of a novel material system with superior properties of energy storage and conversion is a significant work. In this paper, amorphous nickel sulfide nanoparticles anchored on N-doped graphene nanotubes (N-GNTs@NSNs) were firstly synthesized by a facile electrochemical-deposition method, which can serve as free-standing robust supercapacitor electrode materials and electrocatalysts. Stemming from the disordered structure of amorphous active materials and the synergy of novel N-GNT framework materials, the as-prepared N-GNT@NSN electrode unveils prominent capacitive behaviors, including a large specific capacity of 240 mA h g-1 (2160 F g-1), decent rate capability, and outstanding cycling stability (95.8% of capacity retention after 12 000 cycles). An asymmetric supercapacitor with N-GNTs@NSNs as the positive electrode and active carbon (AC) as the negative electrode is further assembled, which shows a maximum energy density of 49.5 W h kg-1 at a power density of 800 W kg-1 and robust stability (96.6% capacity retention after 12 000 cycles). Moreover, the electrode also possesses high activities in the oxygen evolution reaction (OER), namely it can attain a current density of 10 mA cm-2 at an overpotential of 284 mV in 1 M KOH. This finding is not only important for significantly enhancing the electrochemical performances of supercapacitor electrode materials and electrocatalysts, but also lays the solid foundation for their further industrial applications in energy storage and conversion systems.

Porous Nanofibers Formed by Heterogeneous Growth of ZnO/Ag Particles and the Enhanced Photocatalysis.

Porous ZnO/Ag nanofibers with unique multi-interface contact structures have been synthesized by an electrospinning method. The composite nanofibers with the length of several hundred micrometers are composed of uniformly distributed ZnO and Ag nanoparticles in the size range 10~30 nm. Notably, a heterogeneous growth in the interface of ZnO and Ag particles occurs. The MO degradation rate of ZnO/Ag nanofibers with Ag content of 18 wt.% is 100% in 10 min under UV-vis irradiation and that of ZnO/Ag nanofibers with Ag content of 15 wt.% is 92% in 40 min under simulated day light, which is two times that of the pure ZnO. It is attributed to a special structure that improves the generation and separation efficiency of the photo-generated charges by the expansion of the absorption edges, the utilization efficiency of the surface plasmon resonance (SPR) oscillations of Ag, and the effective transferring of electrons from ZnO through the heterogeneous-growth interface. No obvious loss of the photocatalytic activity is observed after five cycles, indicating the excellent photostability of ZnO/Ag nanofibers. The work sheds light on the structure design of highperformance composite photocatalysts.

Synthesis of Ag/AgCl modified anhydrous basic bismuth nitrate from BiOCl and the antibacterial activity.

Novel nanocomposite of Ag/AgCl and a single phase of anhydrous basic bismuth nitrate (ABBN)-Bi6O4.46(OH)3.54(NO3)5.54 with efficient antibacterial activity was prepared from BiOCl. Microstructure was characterized as AgCl nanotubes and Ag nanoparticles mixed with Bi6O4.46(OH)3.54(NO3)5.54 nanosheets in nanometer scale. Antibacterial activity of the composite was tested by agar disc diffusion and agar dilution methods using Escherichia coli as target bacteria. The diameter of inhibition zone of Ag/AgCl/ABBN is 17.0 mm while that of bulk BBN is 8.1 mm. The MIC value of Ag/AgCl/ABBN is ascertained as 35 µg mL-1. Results prove that Ag/AgCl/ABBN nanocomposite has much higher antibacterial activity in comparison with bulk basic bismuth nitrate.

A glassy carbon electrode modified with graphene oxide, poly(3,4-ethylenedioxythiophene), an antifouling peptide and an aptamer for ultrasensitive detection of adenosine triphosphate.

An antifouling aptasensor is described for voltammetric determination of adenosine triphosphate (ATP). A glassy carbon electrode (GCE) was modified with a graphene oxide and poly(3,4-ethylenedioxythiophene) (GO-PEDOT) composite film by electrodeposition. Next, the zwitterionic peptide (EKEKEKE) was attached. It forms an antifouling layer on the modified GCE and serves as the support for subsequent aptamer immobilization. The resulting aptasensor typically is operated at a potential of 0.18 V (vs. SCE) using hexacyanoferrate as the electrochemical probe. It has a linear response in the 0.1 pM to 1.0 µM ATP concentration range, a 0.03 pM detection limit and a sensitivity of 2674.7 µA·µM-1·cm-2. It has outstanding selectivity, satisfactory reproducibility and desired stability. It was used to quantify ATP in ATP-spiked 10% serum solutions. Graphical abstract Schematic presentation of the construction of the aptamer based electrode for voltammetric determination of ATP.

Fast Removal of Methylene Blue by Fe3O4 Magnetic Nanoparticles and Their Cycling Property.

The fast removal of dyes from aqueous solution and the recycling of adsorbents are currently popular topics in the study of adsorbents. Fe3O4 magnetic nanoparticles (MNPs) are usually applied in the preparation of composite adsorbents as magnetic carriers. Therefore, it is significant if single Fe3O4 MNPs can quickly remove dyes from aqueous solution with good cycling stability. Here, we report the preparation of Fe3O4 MNPs through an improved co-precipitation method, which has the inherent advantage of fast, inexpensive and without requiring the protection of nitrogen or an inert gas. The as-prepared Fe3O4 MNPs were used as an adsorbent to remove of methylene blue (MB) under alkaline condition, and then they were characterized by different measurements. The adsorption process was studied by various parameters, such as solution pH, initial MB concentration and contact time. The adsorption of MB over Fe3O4 MNPs reached equilibrium in 5 min, and it was observed to obey the pseudo-second-order kinetics model and Langmuir isotherm with a maximum adsorption capacity of 45.43 mg/g at pH = 12 and T = 298 K. Furthermore, two simple methods for desorption and chemical oxidation were used to the regenerate Fe3O4, and it turned out that Fe3O4 magnetic nanoparticles were able to maintain a high adsorption capacity (36 mg/g for desorption and 36.9 mg/g for chemical oxidation, respectively) after 4 circulations.