Search

The development of a simple and sensitive electrochemical sensing platform for levofloxacin (LVF) analysis is of great significance to human health. In this work, a covalent organic framework (TP-COF) was in situ grown on the surface of Sn-MoC nanospheres with nanoflower-like morphology through a one-pot method to obtain the TP-COF@Sn-MoC composite. The prepared composite was used to modify a glassy carbon electrode (GCE) to realize the sensitive detection of levofloxacin. TP-COF was formed by polycondensation of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and pyromellitic dianhydride (PMDA), in which C = O and C = N groups served as double active centers for the recognition and electrocatalytic oxidation of the target molecule. Meanwhile, the introduction of Sn-MoC improved the conductivity of the electrode. The TP-COF@Sn-MoC composite produced a strong synergistic effect and showed a high electrocatalytic ability toward levofloxacin oxidation. The linear range of LVF was 0.6–1000 μM and the limit of detection (LOD) was 0.029 μM (S/N = 3). In addition, the sensor has been successfully applied for the analysis of LVF in human urine and blood serum samples with acceptable recovery rates, demonstrating that the sensor was promising in practical applications. [ABSTRACT FROM AUTHOR]

A novel electrochemical biosensor with excellent performance was fabricated for levofloxacin (LEV) detection, which adopted triangular Ag nanoplates (Tri-AgNP) confined in a poly-L-cysteine (poly-L-Cys) film and a semiconducting covalent organic framework (COF) as the electrochemical sensing material. The developed electrochemical sensor revealed excellent analytical properties because of its good electrical conductivity, fast electron transfer, and abundant bioactive site. Based on this, a linear relationship between the LEV concentration and the peak current response at 0.92 V was obtained under the optimal experimental conditions by differential pulse voltammetry (DPV), with a wide linear range of 0.05 to 600 μM and a low limit of detection (LOD) of 0.0061 μM. The prepared sensor also realized sensitive and accurate determination of LEV in human serum and urine samples by standard addition method, with satisfactory recoveries (97.1 to 104%) and a low relative standard deviation of less than 4.6%. These results indicated that the novel ternary system has a promising application in the development of electrochemical signal probe and electrochemical biosensing platform. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs), as multinuclear metal oxide clusters, possess natural multi-electron redox properties and high electrical conductivity. However, their susceptibility to leaching and agglomeration limits their application in energy storage. MOF materials provide a solution to the limitation of POMs due to their controllable pore sizes, big surface areas and strong adsorption properties. The synergistic effect between the two components greatly improves the electrochemical properties of the composites. In view of this, PMo 12 is encapsulated in ZIF-67 to form PMo 12 @ZIF-67 by in situ self-assembly, and benefitted from this unique precursor, MoSe 2 /(Ni, Co)Se 2 hollow structures assembled by nanoparticles are synthesized though Ni2+ etching and selenization process. At the same time, the PMo 12 content is optimized to get the best performance of 60-MoSe 2 /(Ni, Co)Se 2. In the three-electrode test, the developed 60-MoSe 2 /(Ni, Co)Se 2 electrode material exhibits an excellent specific capacity of 359.9 mA h g−1 at a current density of 1 A g−1, and a capacitance retention rate of 83.7 % after 10,000 cycles. In addition, the asymmetric supercapacitor (ASC) assembled with a positive electrode of 60-MoSe 2 /(Ni, Co)Se 2 and a negative electrode of activated carbon exhibits an excellent energy density of 40.3 W h kg−1 at a power density of 800.9 W kg−1. These superior electrochemical properties are attributed to the unique electronic structure of PMo 12 , which further demonstrates the feasibility of constructing hollow multicomponent selenides as energy storage materials using PMo 12 -ZIF-67 as a precursor. [Display omitted] • Successful construction of hollow MoSe 2 /(Ni, Co)Se 2 nanomaterial by in situ self-assembly. • 60-MoSe 2 /(Ni,Co)Se 2 exhibits a high specific capacitance of 359.9 mA h g−1 at 1 A g−1. • The ASC device displays a high energy density of 40.3 Wh kg−1 at 800.9 W kg−1. • The assembled ASC device keeps 89.6 % of its initial capacity after 10,000 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • FNCS@NVL multi-metal hollow heterostructure was constructed. • FNCS@NVL exhibits a high specific capacitance of 1964.4F·g−1 at 1 A·g−1. • FNCS@NVL//AC delivers an ultrahigh energy density of 71.9 Wh·kg−1 at 800.01 W·kg−1. Metal-organic framework (MOF) derivatives as supercapacitor electrodes are limited by their poor conductivity and capacitance properties. Therefore, it is crucial to improve the performance by constructing a rational structure. Here, MIL-88A is converted into a unique hollow heterostructure FeNiCoSe@NiV layered double hydroxide (FeNiCoSe@NiV-LDH, simplified as FNCS@NVL) by a simple ion-exchange combined with co-precipitation technique. The Ni-Co ratio is modulated by an intermediate optimization strategy. Owing to the multi-metal sites and the unique structure, the designed FNCS@NVL shows excellent electrochemical properties as expected. It exhibits excellent specific capacity (1964.4 F·g−1 at 1 A·g−1) and capacitance retention (82.1 % at 10,000 cycles) at three-electrode setup. In addition, the hybrid supercapacitor (HSC) assembled by FNCS@NVL as the positive electrode and activated carbon as the negative electrode also exhibits a high energy density of 71.9 W h·kg−1 at a power density of 800.01 W·kg−1. These results demonstrate that the designed FNCS@NVL complex is an excellent energy storage material and further validate the great potential of polymetallic materials in energy storage. It provides a unique idea for constructing supercapacitors with high energy density and power density. [ABSTRACT FROM AUTHOR]

Carbon capture is one of the important methods to achieve carbon neutrality. In this paper, a simple and reliable method for the preparation of poly(anthraquinone)/multi-walled carbon nanotube composites (PAQ/MWCNTs) for capturing carbon dioxide is proposed. Using constant magnetic stirring, 1,4-anthraquinone (1,4-AQ) was allowed to accumulate on multi-walled carbon nanotube (MWCNTs) substrates via π–π. The poly(anthraquinone)/multi-walled carbon nanotube composites were produced by this continuous process. Besides, the carbon cloth electrode prepared from PAQ/MWCNTs composites was subjected to redox potentials for carbon dioxide capture. Results showed that PAQ/MWCNTs composites had good redox reversibility, their carbon dioxide capture capacity was 7.80 mmol·g−1 while the material utilization rate reaches reached 73.4%. [ABSTRACT FROM AUTHOR]

In this paper, a polydopamine-graphene composite gel (PDA-GA) was prepared from graphene oxide by a facile in-situ reduction assembly method using ascorbic acid combined with dopamine (DA). The morphology and microstructure of PDA-GA were characterized by SEM, XRD, FTIR, BET-BJH, and MIP, and the adsorption behavior of PDA-GA for Cu2+ was studied. Furthermore, the response ability of graphene composite gel-modified glassy carbon electrode (PDA-GH-GCE) to trace Cu2+ was investigated by linear sweep anodic stripping voltammetry. Results showed that when the mass ratio of graphene oxide to DA was 1:3, the adsorption effect of PDA-GA for Cu2+ was the best, and the adsorption capacity reached 316 mg/g. PDA-GA-GCE was sensitive to trace Cu2+, and the detection limit could reach 1.6 × 10−7 mol/L. [ABSTRACT FROM AUTHOR]

It is of great significance to propose simple methods to detect DNA bases sensitively for biological analysis and medical diagnosis. Herein, a highly crystalline polyimide covalent organic framework (TAPM-COF) has been successfully synthesized via a solvothermal route using pyromellitic dianhydride (PMDA) and tris(4-aminophenyl) amine (TAPA), which possessed large specific surface area (2286 m2 g−1) and excellent thermal stability. Intriguingly, the crystallinity of the TAPM-COF improved significantly with the increase of water content in the reaction medium. To verify this phenomenon, we synthesized TPPM-COF with two pores by pyromellitic dianhydride (PMDA) and N,N,N′,N'-tetrakis(4-aminophenyl)-1,4-benzenediamine (TPDA), which bonding was similar to TAPM-COF. Furthermore, the prepared TAPM–COF–0.3 was used to construct a novel and independent electrochemical biosensor on glassy carbon electrode for simultaneously determination of adenine (A) and guanine (G) without other additives. However, to further improve signal of TAPM-COF in electrochemical sensing, the crystalline TAPM–COF–0.3 can be readily integrated with amino-functionalized multiwalled carbon nanotubes (NH 2 -MWCNT) to form core-shell TAPM–COF–0.3@NH 2 -MWCNT driven by a π–π stacking interaction for more sensitive electrochemical sensing toward purine bases. In comparison to TAPM-COF/GCE, the TAPM-COF@NH 2 -MWCNT/GCE exhibited more favorable linear range and lower limit of detection. The work provided a new strategy for amplifying signal of COF in the field of electrochemical sensors. [Display omitted] • Two highly crystalline polyimide COFs were successfully synthesized. • A novel electrochemical sensor was fabricated by TAPM-COF alone. • In situ integration of TAPM-COF with NH 2 -MWCNT formed the core-shell structure. • The TAPM–COF–0.3@NH2-MWCNT allowed preparation of a novel electrochemical sensor. [ABSTRACT FROM AUTHOR]

As a kind of energy storage device, supercapacitors have attracted the attention of researchers, and the development of high-performance electrode materials is also the focus of attention. In this paper, template synthesis and pyrolysis were combined to prepare high performance porous carbon electrode materials. The carbonized electrode material effectively increased the capacitance storage capacity and charge transfer rate. The results revealed that the derivative had a relatively low charge-transfer resistance and high specific capacitance of 1059 F·g−1 at a current density of 1.0 A·g−1 in a three-electrode system. To further exploring practical application, a device based on the derivative and hemp-activated carbon asymmetric supercapacitor was assembled in 0.1 M Na 2 SO 4 neutral electrolyte, which exhibited an energy density of 20.35 Wh·kg−1 at a power density of 400 W·kg−1. Interestingly, it showed capability retention of nearly of 91.7% and columbic efficiency of 100% even after 10000 charging/discharging cycles in the neutral electrolyte. Image 1 • The aqueous NPCZ-3//HAC ASC is assembled in 0.1 M Na 2 SO 4 neutral electrolyte. • Both cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) curves of ASC display pip symmetric characteristic. • The as-assembled ASC delivers a nearly of 91.7% capability retention after 10000 cycles. • The ASC delivers has a coulomb efficiency of 100% after 10000 cycles in a neutral electrolyte. [ABSTRACT FROM AUTHOR]

Transition metal sulfides derived from metal‐organic frameworks (MOFs) have received increasing attention as a potential energy storage electrode material. Here, a series of NiS2/CoS2/NC‐T (T=temperature) have been successfully constructed by carbonizing and sulfuring the precursor of Ni/Co‐MOF. It is worth emphasizing that N‐doped carbon materials improve the conductivity of the electrode material. Moreover, NiS2/CoS2/NC‐500 maintains the rod‐like structure of the precursor and exhibits a high specific capacitance of 1325 F g−1 at a current density of 1 A g−1. Apart from high capacitance, the NiS2/CoS2/NC‐500 also demonstrated excellent cycling stability with retention rate of 75 % after 5000 cycles at a current density of 5 A g−1. The good performance could be attributed to the unique rod‐like structure and pore‐size distribution of NiS2/CoS2/NC‐500. Moreover, an assembled asymmetric supercapacitor NiS2/CoS2/NC‐500//AC displays a high energy density of 53.93 Wh kg−1 at a power density of 800 W kg−1 and good cycle stability with capacitance retention of 85.71 % after 20,000 cycles at 5 A g−1. In particular, a red LED can be illuminated by the assembled ASC, indicating that as‐synthesized NiS2/CoS2/NC‐500 hold great potential for practical applications. [ABSTRACT FROM AUTHOR]

Uric acid and dopamine are closely related to the health of the organism, so it is important to determine them simultaneously and efficiently. In this paper, the metal-organic framework DUT-67 was in situ grown on the surface of bimetallic oxide ZnCo 2 O 4 nanoflowers, and then ultrasonically compounded with multi-walled carbon nanotubes (MWCNTs) to prepare DUT-67/ZnCo 2 O 4 -MWCNTs composite. The prepared composite was characterized by XRD, SEM, XPS, FTIR, BET and other techniques. Finally, an electrochemical sensor based on DUT-67/ZnCo 2 O 4 -MWCNTs composite modified glassy carbon electrode for simultaneous detection of dopamine (DA) and uric acid (UA) was fabricated. The introduction of ZnCo 2 O 4 into the composite efficiently overcame the disadvantage of the easy aggregation of DUT-67 and produced a synergistic effect with MWCNTs. The electron transfer rate between the electrode and the electrolyte solution was accelerated, and the detection signals of the target molecules were amplified. After characterizing the electrochemical properties of the composite electrode, it was found that the constructed electrochemical sensor showed low detection limits for DA and UA, which were 12 nM and 8.7 nM, respectively, and the wide linear range of 1.0–180.0 μM. Besides, the sensor had excellent reproducibility, repeatability, anti-interference and stability. The proposed sensor was also successfully used to determine the contents of DA and UA in dopamine injection and urine samples with relatively satisfactory recovery rates. This work not only provides a new strategy for the preparation of MOF modified electrodes, but also has a potential application prospect in bioassays. [Display omitted] • DUT-67 aggregation was eliminated and SSA was enhanced by introducing ZnCo 2 O 4 nanoflower. • Synergistic effect of MWCNTs and DUT-67/ZnCo 2 O 4 improves the electrochemical performance. • DUT-67/ZnCo 2 O 4 -MWCNTs/GCE realizes simultaneous detection of DA and UA with high sensitivity. • This work provides a new strategy for preparation of MOFs based electrochemical sensor. [ABSTRACT FROM AUTHOR]

[Display omitted] • TFP-DAAQ-COF modifier has high specific surface area and good electrical conductivity. • The porous WC has excellent electrical and high adsorption capacity to target molecules. • The propose sensor has wide linearity and low detection limits for detection ACOP and 4-AP. In this article, a novel and simple electrochemical sensing platform has been developed for the simultaneous and sensitive determination of acetaminophen (ACOP) and 4-aminophenol (4-AP). The porous covalent organic frameworks (COFs) material with β-ketoenamine-linkage was successfully synthesized via 1,3,5-triformylphloroglucinol (TFP) and 2,6-diaminoanthraquinone (DAAQ) and named as TFP-DAAQ-COF. High conductivity walnut shells-derived carbon (WC), amine-functionalized multi-walled carbon nanotubes (NH 2 -MWCNTs) with multiple active sites and TFP-DAAQ-COF were combined to obtain composite materials, which were used to modify bare glass carbon electrodes (GCE) and realize the electrochemical analysis of ACOP and 4-AP. The experiments showed that the composite electrode had a strong synergistic effect and exhibited a good electrocatalytic oxidation ability for the two target analytes. The linearity ranges of ACOP and 4-AP were 0.5 ∼ 200 μM and 1.0 ∼ 250 μM, respectively and the detection limits (S/N = 3) were 0.12 μM and 0.18 μM. In addition, the sensor showed acceptable reproducibility, stability and excellent selectivity. The recovery was satisfactory, when it was used to analyze the contents of ACOP and 4-AP in real samples, indicating that the sensor was feasible in practical applications. [ABSTRACT FROM AUTHOR]

In this article, a trimesic acid-mediating control synthesis strategy was proposed for preparing the NiCo-MOF composition structure of microsphere and nanosheet by substituting 1,4-dicarboxybenzene with trimesic acid. Then the pre-synthesized MOF, as a precursor and template, was further vulcanized by a facile hydrothermal method to obtain hollow microsphere and nanosheet interleaved nickel and cobalt bimetallic sulfide materials (NiCo-S) while these microspheres and nanosheets were composed of smaller nanoparticles. This unique structure endowed quick electron/ion transport and electrolyte penetration as well as abundant redox active sites, significantly facilitating electrochemical performance. The obtained NiCo-S-2 showed higher specific capacitance (1790.4 F g−1) than its precursor NiCo-MOF-2 and other molar ratios of counterparts. Using it as an positive electrode and activated carbon (AC) as negative electrode, the assembled asymmetric supercapacitor NiCo-S-2//AC also delivered a high specific capacitance of 114.4 F g−1 and big specific energy of 35.5 Wh kg−1 at 799.99 W kg−1. • A ligand mediated control synthesis strategy was used for NiCo-MOF preparation. • Hollow microsphere and nanosheet interleaved structural NiCo-S had high specific capacitance (1790.4 F g−1). • NiCo-S-2//AC ASC delivered a high energy density of 35.5 Wh kg−1 at at 799.99 W kg−1. [ABSTRACT FROM AUTHOR]

Considering the high electrical conductivity of carbon dots (CDs) and good oxidation-reduction property of polyoxometalates (POMs), a novel CDs coated POMs /metal organic frameworks (POMOFs) composition structure, CDs@PMo 12 /Ni-MOF, was prepared by hydrothermal reaction in this work. PMo 12 was encapsulated in the Ni-MOF framework to form the POMOF composite material, which realized the fixation of water-soluble [PMo 12 O 40 ]3- (PMo 12). A comparison study on the cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) of the resulting CDs@PMo 12 /Ni-MOF with different compositions revealed that 6CDs@PMo 12 /Ni-MOF was better formulation in terms of specific capacity (748.8 C·g−1 at 1 A·g−1) and rate performance (75.93 % at 10 A·g−1). Furthermore, a hybrid supercapacitor device was assembled using 6CDs@PMo 12 /Ni-MOF as positive electrode and activated carbon (AC) as negative electrode, which showed an high energy density of 39.22 Wh·kg−1 under 749.9 W·kg−1 and excellent cyclic stability (98.4 % for 20000 cycles at 5 A·g−1). [Display omitted] • Fixation of water-soluble PMo 12 was realized to form POMOF composite material. • CDs@PMo 12 /Ni-MOF has excellent rate performance and cycle stability. • 6CDs@PMo 12 /Ni-MOF exhibits high specific capacitance and energy density. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have received tremendous interest due to their structural diversity and versatility. These unique physicochemical properties make them exhibit great application potential in the field of electrochemical sensor. In this study, an imine bond-linked COF with porosity and large specific surface area was fabricated by a dehydration condensation reaction between 1, 3, 5-tris(4-formylphenyl)benzene (TFPB) and 1, 3, 5-tris(4-aminophenyl) benzene (TAPB) and combined with high electrical conductivity of oxidized multi-walled carbon nanotube (Ox-MWCNT). The structure of the COF and the resulted composite material were confirmed through a series of characterization techniques, including Fourier-transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and thermogravimetric analysis, then a co-modified glassy carbon electrode was constructed for simple, sensitive and selective electrochemical recognition of dopamine (DA) and uric acid (UA). The fabricated electrochemical sensor displayed a strong current response to both DA and UA in the phosphate buffer solution (PBS) at pH = 6.5. The synergistic effect between COFs and Ox-MWCNT effectively improved the analytical sensitivity for the target analytes. Under optimized experimental conditions, the method showed good performance for DA and UA in the concentration range of 0.6–250.0 μM with low detection limits of 0.073 μM and 0.063 μM (S/N = 3), respectively. Moreover, the proposed sensor exhibited high selectivity, longtime stability, desirable repeatability and acceptable reproducibility and can be used to analyze simultaneously DA and UA in biological and medicine samples with satisfactory results. Our work not only provides a simple way to detect DA and UA quantitatively in real samples, but also offers a new platform for COF-based composite application in electrochemical sensing. [Display omitted] • TFPB-TAPB-COF is prepared via a simple solvothermal method. • TFPB-TAPB-COF/Ox-MWCNT/GCE is fabricated for sensing of dopamine (DA) and uric acid (UA). • The sensor has low detection limits and wide linear ranges for detection DA and UA. • The sensor is successfully applied to the determination of DA and UA in real samples. [ABSTRACT FROM AUTHOR]

Catechol (CC) and hydroquinone (HQ) are highly toxic organic phenolic compounds and they possess immeasurable harm to human health and the environment. Their simultaneous detection can provide valuable reference for the environment protection and human health. In this work, an imine bond-linked covalent organic framework (COF) was fabricated via a facile solvothermal method and then cooperated with multi-walled carbon nanotubes (MWCNTs) to construct a novel electrochemical sensor. The petal-shaped COF provides large specific surface area, and MWCNTs remarkably improve the conductivity of the resulted modified electrode. Co-modification of the COF and MWCNTs to glassy carbon electrode (GCE) leads to a three-dimensional structure and significant synergy. Under the optimal experimental conditions, good linear relationships are obtained over the concentration range from 4.0 to 450 μM for simultaneous determination of CC and HQ and the detection limits are 0.36 μM and 0.38 μM, respectively. The proposed electrochemical sensor shows excellent repeatability, reproducibility, stability, anti-interference and can be exploited to detect simultaneously CC and HQ in Yellow River water and tap water samples. [Display omitted] • TFPPy-BD-COF/MWCNT/GCE shows high electrocatalytic ability catechol(CC) and hydroquinone(HQ). • The prepared electrochemical sensor has low detection limit and wide linear range for detection CC and HQ. • The sensor has been successfully applied to the determination of catechol and hydroquinone in real water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] In this study, metal–organic backbone (UiO-66-NH 2) and thionyl chloride functionalized carbon nanotubes (COCl-MWCNT) were successfully synthesized, and introduced into carbon black (CB) for fabricating novel electrochemical sensor UiO-66-NH 2 /COCl-MWCNT/CB/GCE towards simultaneous determination of dihydroxybenzene isomers hydroquinone (HQ), catechol (CC) and resorcinol (RC). Due to large surface area, excellent conductivity, good electrocatalytic activity and high stability the developed composite modified electrode delivered excellent analytical performance for these three analytes. Under optimal conditions, differential pulse voltammetric (DPV) currents showed good linear relationships with the concentrations of HQ, CC and RC with low detection limits (0.24 μM, 0.11 μM, 0.47 μM) and wide detection ranges (1–1000 μM and 5–1000 μM). In addition, this sensor demonstrated favorable reproducibility, stability and good selectivity for HQ, CC and RC and possessed a great potential for selective detection of dihydroxybenzene isomers in environmental water samples. [ABSTRACT FROM AUTHOR]

In this present work, a carboxylated multi-walled carbon nanotubes (MWCNT-COOH) and covalent triazine framework (CTF-1) co-modified glassy carbon electrode (GCE) is prepared and used for simultaneous electrochemical detection of hydroquinone (HQ) and catechol (CC). Due to the synergistic effect between the high electrocatalytic activity and good conductivity of MWCNT-COOH and large surface area of CTF-1, the prepared modified electrode exhibits good selectivity and high sensitivity for the simultaneous determination of HQ and CC. In the neutral phosphate buffer, HQ and CC produce a pair of well-defined redox peaks on the MWCNT-COOH/CTF-1/GCE. The concentrations of CC and HQ show good linearity in the range of 2–280 μM and the detection limits of HQ and CC are 0.12 μM and 0.17 μM, respectively. The prepared electrochemical sensor can be employed to determine contents of HQ and CC in real samples. [Display omitted] • The MWCNT-COOH/CTF-1 composite exhibits superior electrocatalytic performance towards hydroquinone and catechol detection. • The research paves a feasible way to unlock high performance CTF electrode materials. • The sensor showed excellent specificity, good stability, and desirable reproducibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • MoS 2 @Ni-MOF was prepared and alkalized to obtain MoS 2 /Ni(OH) 2. • MoS 2 /Ni(OH) 2 has high specific capacitance and long cycling life for supercapacitor. • MoS 2 /Ni(OH) 2 was used to construct electrochemical sensor for HQ and CC. A nickel-based metal-organic framework (Ni-MOF) layer was in situ grown on the surface of the sheet MoS 2 to synthesize MoS 2 @Ni-MOF as a precursor. In order to improve the properties of the precursor material, the final MoS 2 /Ni(OH) 2 material was obtained by alkalizing the precursor material. Supercapacitors and electrochemical sensors were prepared by MoS 2 /Ni(OH) 2 composite material. The test indicates that alkaline treatment of Ni-MOF materials is helpful to improve electrochemical performance. MoS 2 /Ni(OH) 2 material used as supercapacitor electrode has a high specific capacitance of 2192 F g−1 and excellent cyclic stability (the capacitance retention rate remains 85.19% after 10,000 charge/discharge cycles). The hybrid supercapacitor (HSC) was assembled with MoS 2 /Ni(OH) 2 as the positive electrode and activated carbon as the negative electrode. The MoS 2 /Ni(OH) 2 //AC HSC device shows an excellent energy density of 50.58 Wh kg−1 at the power density of 800 W·Kg−1. In addition, the MoS 2 /Ni(OH) 2 modified GCE electrode is an excellent electrochemical sensor for the simultaneous determination of hydroquinone (HQ) and catechol (CC). The modified electrode provides wide linear ranges of 1 ∼ 500 and 2 ∼ 400 μM and low detection limits of 0.43 and 0.48 μM for HQ and CC, respectively (S/N=3). The MoS 2 /Ni(OH) 2 material can be applied to supercapacitors and electrochemical sensors, indicating that the material has great potential application value in energy storage and biosensing. [ABSTRACT FROM AUTHOR]

• TFPB-PDA-COF is successfully synthesized. • A dual-signal amplifying sensor for adenine and guanine using the COF was prepared. • Use of NH 2 -rGO and MoS 2 strongly improves conductivity and electrocatalysis. • The biosensor is simple, fast, sensitive, reproducible as well as long-term stable. Alteration in the concentrations of guanine (G) and adenine (A) leads to various abnormalities in the metabolic process which causes various diseases. Therefore, it still remains a challenge to establish an accurate, simple and accurate method for simultaneous detection of guanine and adenine. In this paper, using covalent organic frameworks (COFs) as a carrier and the amino functionalized reduced graphene oxide as charge transfer accelerator, layer molybdenum disulfide (MoS 2) nanosheets are deposited on glassy carbon electrode (GCE) by simple physical stacking to fabricate a dual-signal amplification biosensor for simultaneous detection of adenine and guanine. Under optimized conditions, the electrochemical behaviors of guanine and adenine on the COFS/NH 2 -rG/MoS 2 modified electrode were studied by cyclic voltammetry and differential pulse voltammetry. The sensor performs well in determining G and A at the same time with wide linear ranges of 0.5–150.0 μM and 1.0–280 μM and low detection limits of 0.51 μM(S/N = 3) and 0.44 μM(S/N = 3), respectively. The sensor was successfully used to assay G and A in thermally denatured herring sperm DNA, and the G/A ratio was calculated to be 0.79. The biosensor has the advantages of simplicity, speed, high sensitivity, good reproducibility, and long-term stability. [ABSTRACT FROM AUTHOR]

• The Ni-ZIF-8/N S-CNTs/CS/GCE sensor exhibited superior properties for the simultaneous determination of DA, UA and L-Trp. • The synergistic effect between the Ni-ZIF-8 and N S-CNTs significantly enhanced the peak current response of DA, UA and L-Trp. • Ni-ZIF-8/N S-CNTs/CS/GCE electrochemical sensing platform showed excellent reproducibility and stability. • The fabricated sensor held great potential for the DA, UA and L-Trp detection in human urine, amino acid injection and human serum sample. The accurate simultaneous determination and quantification of biological small molecules including dopamine (DA), uric acid (UA) and L-tryptophan (L-Trp) are necessary to diagnose or monitor possible disease, which further provide important information about the interaction between these analytes during the physiological processes. In this present work, a novel and rapid electrochemical sensor toward the simultaneous determination of dopamine (DA), uric acid (UA) and L-tryptophan (L-Trp) was prepared based on modification of Ni-ZIF-8/N S-CNTs/CS composite upon the bare glassy carbon electrode. The electrochemical response of DA, UA and L-Trp on the Ni-ZIF-8/N S-CNTs/CS/GCE was explored via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronocoulometry (CC) and differential pulse voltammetry (DPV) techniques. The results illustrated that these three analytes displayed the well-resolved and intense electrochemical signals on the designed electrode, owing to the synergic effect originating from Ni-ZIF-8 with highly porous framework structure and N S-CNTs with excellent conductivity. The voltammetric response of Ni-ZIF-8/N S-CNTs/CS/GCE indicated its outstanding electrocatalytic performance for the electrochemical reaction of DA, UA and L-Trp with a wide linear ranges of 8∼500 μM, 1∼600 μM and 5∼850 μM and low detection limits of 0.93, 0.41 and 0.69 μM, respectively. More importantly, the proposed sensor was successfully applied to measure DA, UA and L-Trp in the real samples, meaning that the present method delivered great potential in the field of routine sensing applications. [ABSTRACT FROM AUTHOR]

In this work, the in-situ growth of covalent organic framework materials on polyaniline (TFAB-COF@PANI) was accomplished using a facile one-pot approach. For the microanalysis of sulfamethoxazole (SMX), a highly sensitive electrochemical sensor based on the TFAB-COF@PANI complex modified glassy carbon electrode (GCE) was constructed. The X-ray powder diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and nitrogen desorption test were used to characterize the materials. The electrochemical performance of the sensor was investigated by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance. Strong synergy was generated by the in-situ growth of TFAB-COF with a large specific surface area on PANI, which not only provides a large number of active sites but also amplifies the response signal of SMX. The resulted sensor displays a broad linear range (1–450 μM) and a low detection limit (0.107 μM) for SMX under optimal conditions. The sensor has been effectively utilized for reliable analysis of environmental water samples because of its high repeatability, reproducibility, stability, and interference resistance. [Display omitted] • For the first time, the in-situ growth of TFAB-COF on polyaniline (PANI) was reported. • TFAB-COF@PAIN had homogeneous morphology and strong electrical conductivity. • TFAB-COF@PAIN/GCE had sensitive and selective responses for sulfamethoxazole (SMX). • The sensor may be employed to monitor SMX in real samples. [ABSTRACT FROM AUTHOR]

Herein, covalent organic framework (COF) and covalent triazine framework (CTF) have been successfully combined for electrochemical sensing via carboxylated multi-walled carbon nanotubes (COOH-MWCNTs). The COF was synthesized from 1,3,5-tris-(4-formylphenyl) benzene (TFPB) and benzidine (BD), named TFPB-BD-COF. Meanwhile, CTF was synthesized by 1, 4-dicyanobenzene (DCB), then chemically activated with KOH at 700 °C to obtained chemically activated porous product, caCTF-1–700. A novel electrochemical sensor based on TFPB-BD-COF/caCTF-1–700/COOH-MWCNT composite was constructed for simultaneous detection of acetaminophen (ACOP) and 4-aminophenol (4-AP). The electrochemical behaviors of the ACOP and 4-AP on the TFPB-BD-COF/caCTF-1–700/COOH-MWCNT electrode were explored via differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The fabricated TFPB-BD-COF/caCTF-1–700/COOH-MWCNT composite modified glassy carbon electrode (GCE) possessed outstanding electrocatalytic performance for the electro-oxidation of acetaminophen (ACOP) and 4- aminophenol (4-AP). Under optimal conditions, the linear ranges were 0.6–150 μM for ACOP and 4-AP, respectively, with the low detection limits of 0.053 μM and 0.075 μM, respectively. In addition, it also showed excellent selectivity, repeatability, reproducibility and stability. The proposed modified electrode was applied for the determination of ACOP and 4-AP in acetaminophen tablet and Yellow river water and obtained satisfactory recovery between 96.31~103.96% and 97.2~101.6%, respectively. [Display omitted] • Imine COF and triazine CTF are combined for electrochemical sensing for the first time. • Hierarchical porous composite provides large surface area for improved sensitivity. • COOH-MWCNT connecting two COFs improved electrocatalytic activity and conductivity. • The sensor shows high sensitivity for simultaneous determination of ACOP and 4-AP. [ABSTRACT FROM AUTHOR]

Flexible electrodes with advantageous architectures have emerged as an urgent necessity. Herein, we demonstrate a novel approach to designing and fabricating porous nickel cobalt sulfide sheets anchored on thermally activated carbon cloth (NiCoS/ACC) for use as a flexible anode in supercapacitors. The thermally activated carbon cloth with functional groups provides a framework for the growth of the nickel cobalt aluminum layered double hydroxide (NiCoAl LDH) precursor, which provides an excellent rate of utilization for the active material. Through hydrothermal sulfuration, NiCoAl LDH precursor can be transformed into porous NiCoS nanosheets, yielding NiCoS/ACC, which shows excellent electrochemical performance in a three-electrode system. Excellent electrical conductivity and the enriched redox-active site provided by ACC together with the high porosity, abundant active sites, and large electrode-electrolyte contact area provided by thin NiCoS nanosheets are believed to account for the enhanced electrochemical properties. Moreover, the flexible supercapacitor can exhibit high energy density and excellent cycling stability when equipped with a NiCoS/ACC positive electrode and an activated carbon cloth negative electrode. [Display omitted] • NiCoAl LDHs are utilized as precursors to obtain porous NiCoS nanostructure. • Thermally activated carbon cloth functions as conductive substrate. • The ion exchange/etching method is used to prepare NiCoS. • The supercapacitor exhibits excellent flexibility and practicability. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel and convenient electrochemical sensor based on stacked graphene nanofibers (SGNF) and gold nanoparticles (AuNPs) composite modified glassy carbon electrode (GCE) was developed for the determination of bisphenol A (BPA). The AuNPs/SGNF modified electrode showed an efficient electrocatalytic role for the oxidation of BPA, and the oxidation overpotentials of BPA were decreased significantly and the peak current increased greatly compared with bare GCE and other modified electrode. The transfer electron number (n) and the charge transfer coefficient (α) were calculated with the result as n =4, α =0.52 for BPA, which indicated the electrochemical oxidation of BPA on AuNPs/SGNF modified electrode was a four-electron and four-proton process. The effective surface areas of AuNPs/SGNF/GCE increased for about 1.7-fold larger than that of the bare GCE. In addition, the kinetic parameters of the modified electrode were calculated and the apparent heterogeneous electron transfer rate constant (k s) was 0.51s−1. Linear sweep voltammetry was applied as a sensitive analytical method for the determination of BPA and a good linear relationship between the peak current and BPA concentration was obtained in the range from 0.08 to 250μM with a detection limit of 3.5×10−8 M. The modified electrode exhibited a high sensitivity, long-term stability and remarkable reproducible analytical performance and was successfully applied for the determination of BPA in baby bottles with satisfying results. [Copyright &y& Elsevier]

Abstract: A graphene sheets (GS), ionic liquid (IL) and chitosan (CS) modified electrode was fabricated and the modified electrode displayed excellent electrochemical catalytic activities toward guanine and adenine. The transfer electron number (n) and the charge transfer coefficient (α) were calculated with the result as n =2, α =0.58 for guanine, and n =2, α =0.51 for adenine, which indicated the electrochemical oxidation of guanine and adenine on GS/IL/CS modified electrode was a two-electron and two-proton process. The oxidation overpotentials of guanine and adenine were decreased significantly compared with those obtained at the bare glassy carbon electrode and multi-walled carbon nanotubes modified electrode. The modified electrode exhibited good analytical performance and was successfully applied for individual and simultaneous determination of guanine and adenine. Low detection limits of 0.75μM for guanine and 0.45μM for adenine were obtained, with the linear calibration curves over the concentration range 2.5–150μM and 1.5–350μM, respectively. At the same time, the proposed method was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfying results. Moreover, the GS/IL/CS modified electrode exhibited good sensitivity, long-term stability and reproducibility for the determination of guanine and adenine. [Copyright &y& Elsevier]

• A simple ultrasound-assisted method was used to synthesize nitrogen-containing p - π conjugated-organic ligands. • Nitrogen-containing conjugated organic ligands have good conductivity. • Carbon-enriched MOFs and derived porous carbon have excellent electrochemical performance. • The change law of electrochemical performance was explored with gradient temperature. • The MOF-B-600//AC ASC device exhibits a high energy density of 63.62 Wh·kg−1 at power density of 400 W·kg−1. [Display omitted] This article aims to use nitrogen-doped metal p - π conjugated-organic frameworks and derived carbon-rich electrode materials for high-performance electrode materials. Nitrogen-doped contributes to the energy storage performance, and the p-π conjugated-organic ligands of the conjugated system can not only improve the stability of the structure, but increase the conductivity of the material. Gradient carbonization can explore the maximum electrochemical potential of MOF-B, from which the previous 1271.0 increased to 2727.5 F·g−1 at a current density of 1.0 A·g−1. The excellent capacitance retention rate is 86.67% of the initial value at a high current density after 20,000 cycles. Besides, the MOF-B-600//AC also shows a high energy density of 63.62 Wh·kg−1 at a power density of 400 W·kg−1 and good coulomb efficiency of 90.7%. As a result, the excellent electrochemical performance of the nitrogen-doped and carbon-enriched MOF-B-600 has potential application prospects in energy storage devices. [ABSTRACT FROM AUTHOR]