A flexible ascorbic acid (AA)-imprinted poly(o-phenylenediamine) (ploy(o-PD))/zeolite imidazole frameworks-67 (ZIF-67)/carbon cloth (CC) electrode was prepared for electrochemical sensing AA. The ...flexible AA-imprinted poly(o-PD)/ZIF-67/CC electrode was prepared by growing ZIF-67 on flexible CC, electropolymerization of o-PD with AA on ZIF-67/CC and eluting template molecules AA. The results showed that the spherical ZIF-67 crystals were arranged evenly and firmly on the fibers of CC surface. The diameter of spherical ZIF-67 crystals was approximately 500–600 nm, and the spherical ZIF-67 crystals catalyzed the oxidation of AA well. A layer of poly(o-PD) with AA-imprinted pores was covered on the ZIF-67/CC electrode, so the AA-imprinted poly(o-PD)/ZIF-67/CC electrode exhibited better selectivity toward AA detection and good stability. The molecularly imprinted sensor exhibits high sensitivity, and the sensitivity could reach 959.9 μA/mM
−1
cm
−2
, the detection limit was 0.019 μM, and the concentration range of AA was 0.057 μM–11.4 0 mM. The AA-imprinted poly(o-PD)/ZIF-67/CC electrode also showed higher stability and repeatability. The results proved that the spherical ZIF-67 crystals were good electrode materials for electrochemical AA biosensors.
A novel supercapacitor based on ultralight and elastic three-dimensional porous melamine foam-derived macroporous carbon /reduced graphene oxide/polyaniline nanocomposites were fabricated, which ...showed great electrical performance and cycle performance.
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A novel supercapacitor based on ultralight and elastic three-dimensional (3D) porous melamine foam (MF)-derived macroporous carbon (3DPMFDMC)/reduced graphene oxide (rGO)/polyaniline (PANI) nanocomposites (denoted as 3DPMFDMC/rGO/PANI) were fabricated. By high temperature carbonization, the commercial MF soaked in GO solution was prepared into ultralight and elastic 3DPMFDMC, the rGO were uniformly distributed into 3DPMFDMC to obtain 3DPMFDMC/rGO, and finally PANI was grown on the 3DPMFDMC/rGO by using in situ chemical oxidation polymerization method. The obtained 3DPMFDMC/rGO/PANI nanocomposites were characterized by SEM, FT-IR and Raman. The results showed the uniform distribution of rGO connected the broken fibers of 3DPMFDMC produced in the high temperature carbonization to improve the electrical conductivity and also enlarged the specific surface area of nanocomposites greatly. Lots of PANI were vertically arrayed on the surface of 3DPMFDMC/rGO. 3DPMFDMC/rGO/PANI exhibited a rapid electron/mass transport. Owing to its special structures and nanocomposites, the supercapacitor showed good electrical performance with a specific capacitance of 1870 F/g at the current density of 1 A/g. Moreover, the specific capacitance remained 95.4% after 1000 charging/discharging cycles at a current density of 5 A/g.
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•A novel Zr-DMBD MOFs/3D-KSC electrochemical sensor was developed for the removal and determination of Hg(II).•Zr-DMBD MOFs/3D-KSC integrated electrode exhibited excellent ...performances for Hg(II) removal and detection.•The selectivity and stability of the Zr-DMBD MOFs/3D-KSC Hg(II) sensor were improved greatly.•The new conceptual approach (mercaptan of MOF) propose an efficient electrochemical detection of Hg(II).
Mercury ion (Hg(II)) has serious destructive effects on organisms and environments even at extremely low concentration. Therefore, effective removal and highly sensitive determination of trace Hg(II) is very important. Herein, mercaptan functionalized metal-organic frameworks (MOFs) were prepared by the coordination between Zr (IV) and 2,5-dimercaptoterephthalic acid (Zr-DMBD MOFs) and attached to three-dimensional kenaf stem-derived carbon (3D-KSC) to form a novel nanocomposite for removal and electrochemical detection of Hg(II). The sensitivity of Hg(II) detection was 324.58 μA μM−1 cm-2, the linear range was 0.25 μM–3.5 μM and the detection limit was 0.05 μM. The good performances were because lots of Zr-DMBD MOFs were uniformly dispersed on 3D-KSC and the porous Zr-DMBD MOFs had a large number of mercaptan groups to enrich Hg(II) significantly on the electrode. The Hg(II) detection would not be interfered by other co-existing heavy metal ions, and the Zr-DMBD MOFs/3D-KSC also showed excellent stability and reproducibility. Furthermore, the Zr-DMBD MOFs/3D-KSC could effectively remove Hg(II) in real wastewater. The residues were lower than national discharge standard of industrial wastewater (GB30770-2014).
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•Using dialysis membrane promoted the spontaneous growth of 3D network TP-TD COF.•Intramolecular NH·· OC hydrogen bonding enhanced the stability of COF.•Abundant ONO in structure ...serves as the catalytic active site of heavy metal ions.•Simultaneous detecting of four HMIs with great electrochemical performance.•The sensor can be applied to the detection of heavy metal ions in river water.
The bioaccumulation of heavy metal ions (HMIs), even at low concentrations, will lead to high toxicity. So, in this work, a hydrazone-linked covalent organic framework (COF) with abundant N and O atoms was prepared for sensitive HMIs detection. Under the room temperature, terephthaloyl dihydrazide (TD) and triformylphloroglucinol (TP) reacted to form the hydrazone bond, and a new hydrazone-linked TP-TD COF was prepared. During the reaction, enole-keto tautomerism occurred, and NH···OC hydrogen bond was formed, which improved the crystallinity and chemical stability of COF. Accordingly, the hydrazone-linked TP-TD COF presented three-dimensional network morphology. The porous channels could promote the migration of HMIs, and the affinity of N and O atoms to HMI was utilized. There were abundant O·N·O sites in each unit, so the hydrazone-linked TP-TD COF was applied to the sensing of HMIs. The electrochemical sensor constructed by TP-TD COF was used to detect Cd2+, Pb2+, Cu2+ and Hg2+ simultaneously. Under optimized conditions, the electrochemical sensor based on TP-TD COF showed fast response speed, sensitive detection ability and the potential for practical sample detection.
The detection of glucose (Glu) is of great significance in medical diagnosis, food processing and biotechnology. Rapid, accurate and convenient detection technology is particularly important. Herein, ...the Co3O4-PC nanocomposite grown on biomass-derived porous carbon (PC) was prepared by hydrothermal method and subsequent air calcination. Chitosan (CS) was electrodeposited on the surface of Co3O4-PC by potentiostatic deposition with Glu as the template molecule. Finally, the template molecule was eluted by cyclic voltammetry to create specific recognition sites for Glu, and a highly selective and stable Glu sensor was constructed. The obtained MIP (molecularly imprinted polymer)-Glu-CS/Co3O4/PC nanocomposites were characterized by scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, chronoamperometry and so on. The results showed that the MIP-Glu-CS/Co3O4-PC had great catalytic performance for Glu detection with a linear range of 12.17 μM-2.3 mM, a detection limit of 4.01 μM, and a sensitivity of 407.5 μA cm−2 mM−1. The sensor has excellent selectivity and stability. This work provides a guide for improving the selectivity of nanozymes.
A novel Cu–Co-zeolite imidazole framework (Cu–Co-ZIF)-derived CuCo2O4@carbon nanocomposites supported on three-dimensional porous carbon (3D-KSC) were prepared to develop molecularly imprinted ...electrochemical sensors for sensing dopamine (DA). Firstly, polyhedral Cu–Co-ZIF was synthesized at room temperature and uniformly arrayed on 3D-KSC, and then the CuCo2O4@carbon nanostructure was obtained by high-temperature carbonization under nitrogen atmosphere. Finally, the molecularly imprinted polymer (MIPs) DA-imprinted chitosan was covered by potentiostatic electrodeposition to obtain the MIPs/CuCo2O4@carbon/3D-KSC integrated electrode. The results showed 15 μm-sized polyhedral Cu–Co-ZIF crystals were transformed into smaller irregular porous CuCo2O4@carbon nanocomposites with rough surface by calcination. Here, the produced 5 nm-sized CuCo2O4 crystals were uniformly embedded into the N-doped porous carbon frameworks. Various experimental conditions including the amount of Cu–Co-ZIF grew on 3D-KSC, calcination temperature, electrodepositing time of MIPs, the eluted time of template molecule and the pH of electrolyte were explored. The as-prepared MIPs/CuCo2O4@carbon/3D-KSC integrated electrode exhibited excellent anti-interference ability and good stability. The sensitivity for DA detection was 720.8 μA mM−1cm−2, the detection range was 0.51 μM–1.95 mM, and the detection limit was 0.16 μM.
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•A novel MIPs/CuCo2O4@carbon/3D-KSC electrochemical sensor was developed for DA detection.•The molecularly imprinted polymer was prepared by using DA as a template and chitosan as a linking agents.•The MIPs/CuCo2O4@carbon/3D-KSC integrated electrode exhibited excellent performances for DA detection.•The selectivity and stability of the MIPs/CuCo2O4@carbon/3D-KSC DA sensor were improved greatly.
Three-dimensional kenaf stem-derived macroporous carbon (3D-KSC)/reduced graphene oxide (rGO) integrated electrode were constructed as conductive support substrate to electrodeposit polyaniline ...(PANI) for building high-performance supercapacitors. Scanning electron microscopy (SEM), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and electrochemical methods were used to characterize the 3D-KSCs/rGO/PANI electrode. It was found by SEM that lots of well-dispersed rGO uniformly grew on 3D-KSC based on covalent bond, which effectively avoided the aggregation of rGO on the electrode surface. FTIR and Raman spectroscopy confirmed that PANI arrays were polymerized on the 3D-KSCs/rGO surface vertically and uniformly. Constant current charging/discharging test was used to investigate the electrochemical properties of 3D-KSCs/rGO/PANI electrode. These test results showed that as-obtained 3D-KSCs/rGO/PANI supercapacitor electrode had gravimetric capacitance of 1224 mF g-1 at the current density of 0.3 A g−1, far larger than most other electrodes. In addition, the gravimetric capacitance remained 87% after 5000 charging/discharging cycles. The good performances of 3D-KSCs/rGO/PANI integrated electrode proved that the resulted supercapacitor electrode had wide prospect in energy storage application.
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•A novel 3D-KSCs/rGO/PANI nanocomposites was prepared for supercapacitors.•The rGO grown on 3D-KSC can effectively avoid aggregation of rGO.•3D-KSC with macroporous structure loaded layered rGO to improve efficiency of rGO and 3D-KSCs.•The 3D-KSCs/rGO/PANI electrode shows good rate capability, excellent cycling stability, and high gravimetric capacitance.
Novel Cu nanospheres@porous carbon firmly arrayed on three-dimensional kenaf stem-derived macroporous carbon (3D-KSCs) integrated electrodes were prepared by simple thermolysis of Cu metal-organic ...framework (HKUST-1) formed on 3D-KSCs for nonenzymatic glucose sensor. The morphology and catalytic activities of as-obtained Cu nanospheres@porous carbon/3D-KSCs were investigated in detail by various techniques. The results confirmed that some octahedral HKUST-1 were intactly transformed into Cu nanospheres@porous carbon nanocomposites and some HKUST-1 were broken into many uniform small Cu nanospheres@porous carbons on the wall of 3D-KSCs upon thermolysis. The spherical nanostructures were consisted of many Cu nanoparticles embedded into 3D porous carbon frameworks. Since the Cu nanospheres@porous carbon/3D-KSCs integrated electrode has hierarchical pores originated from 3D-KSCs and the porous carbon for mass transfer, excellent electrocatalytic activity resulted from hierarchical and uniformly dispersed Cu nanospheres@porous carbon, the nonenzymatic glucose sensor based on Cu nanospheres@ porous carbon/3D-KSC integrated electrode showed an acceptable linear range of 0.15 μM−5.62 mM, a low detection limit of 0.48 μM and with a sensitivity of as high as 28.67 μA mM-1 cm-2. The easy and low-cost preparation, hierarchical nanostructures and good electrocatalytic activity of Cu nanospheres@porous carbon/3D-KSCs rendered it promising candidate for sensors and other applications.
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•A novel Cu nanospheres@porous carbon firmly arrayed on 3D-KSCs integrated electrode was prepared.•The spherical nanostructures were consisted of many Cu nanoparticles embedded into 3D porous carbon frameworks.•The glucose sensor based on the Cu nanospheres@porous carbon/3D-KSCs showed good performances.
A novel Ni@carbon nanocomposites/three-dimensional kenaf stem-derived macroporous carbon (3D-KSCs)-integrated electrode was prepared by calcinating Ni-benzenetricarboxylic acid (Ni-BTC) metal–organic ...frameworks (MOFs) grown on 3D-KSCs under N
2
atmosphere for electrochemical glucose sensor. Both Ni-BTC MOFs/3D-KSCs and Ni@carbon nanocomposites/3D-KSCs-integrated electrode were studied by scanning electron microscopy and X-ray powder diffraction. These results showed that many flowerlike Ni-BTC MOFs which were composed of sticklike nanostructures were grown on the surface of 3D-KSCs. After calcination under N
2
atmosphere, lots of pearl chain-like nanostructures were formed and uniformly arrayed on 3D-KSC electrode. XRD results confirmed that the Ni-BTC MOFs were successfully transformed into pearl chain-like Ni@carbon nanocomposites. Both electrochemical behaviors and electrocatalytic performances of Ni@carbon nanocomposites/3D-KSCs-integrated electrode were explored. Thanks to its large specific surface area, 3D macropores and special structures, the Ni@carbon nanocomposites/3D-KSCs-integrated electrode showed wide linear range (0.024–1.2 mM) and low detection limit (7.85 μM,
S
/
N
= 3) for glucose sensing. Noteworthily, the MOFs/3D-KSCs might be proposed to prepare other nanocomposites for electrochemical biosensing.
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In our work, we reported a novel hollow spherical EH-SiO2@COFTFP-AMPD based on the real-time visual ratiometric fluorescent sensor for the detection of ENR residues in fish scales by ...simple making test strips, gels and smartphones Colorcoll App methods, ENR can inhibit the protons of hydroxyl groups in the system, which acquires great application potential in food health and safety aspects.
•Hollow spherical nanospheres were prepared without HF or strong alkali etching.•Structural tautomeric and hydrogen bond effect can inhibit ACQ of COFTFP-AMPD.•A visualized ratiometric fluorescent probe with wide range and low LOD for ENR.•Real-time visual detection of ENR residues in scales using test strips and gels.•Smartphones can identify and quantify to monitor food safety.
Covalent organic frameworks (COFs) are porous crystalline polymers. Due to aggregation caused quenching (ACQ) effect caused by the strong π-π interactions in stacked layers, weak fluorescence or no luminescence is caused. Here, a series of core–shell structure of SiO2@COFTFP-AMPD (2,4,6-triformylphloroglucinol: TFP, 2,2′-azobis(2-methylpropionamidine) dihydrochloride: AMPD) with different morphologies was prepared by changing temperature and time using –NH2-SiO2 nanospheres (NPs) as templates. Without the need to be prepared by adding HF or strong alkali, the hollow spherical EH-SiO2@COFTFP-AMPD not only inhibited ACQ of COFTFP-AMPD, but also achieved dual emission at 438 and 550 nm. The structure served as ratiometric fluorescent probe for visual detection of Enrofloxacin (ENR) with a detection range of 2.41 nM-0.48 μM and a detection limit as low as 0.80 nM. The concentration of ENR in unknown samples can be detected not only by stripe and gel. Moreover, with the RGB numerical analysis function of smartphone App, real-time visual detection of ENR can be realized, which possesses potential in food health and safety.
