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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 sensitive and selective electrochemical sensor for determination of dopamine (DA) was fabricated based on 3,4,9,10-perylene tetracarboxylic acid functionalized graphene sheets, multi-wall carbon nanotubes and ionic liquid modified glass carbon electrode and the properties of modified electrode were characterized by scanning electron microscopy, transmission electron microscope and electrochemical impedance spectroscopy. The modified electrode showed excellent electrocatalytic activity toward the oxidation of DA. Meanwhile, a possible reaction mechanism related to the oxidation of DA was proposed. The differential pulse voltammetry was used for the determination of DA in the presence of 500μM ascorbic acid and 330μM uric acid under the optimum conditions and a good linear relationship between peak current and the concentration of DA was obtained in the concentration range from 0.03μM to 3.82mM with a detection limit of 1.2×10−9 M (S/N=3). Moreover, the proposed method was successfully applied to determine DA in real sample and satisfactory results were obtained. The results showed that the modified electrode exhibits an excellent catalytic activity, good sensitivity, reproducibility and long-term stability. [Copyright &y& Elsevier]

[Display omitted] • Ratiometric electrochemical biosensor Cu(II)-TADH COF/MB/GCE is constructed for detection of glutathione. • Cu(II) modification improves the conductivity and electrochemical sensing performance of TADH COF. • This electrochemical platform realizes specific and ultra-sensitive detection of GSH. • The sensor is successfully used to determine GSH in real human fluid samples. • This work provides a novel strategy for constructing COF-based electrochemical biosensors. As a vital biological polypeptide molecule, glutathione (GSH) is involved in the regulation of various life activities. Accurate and sensitive detection of GSH in human body is of great significance for the preliminary diagnosis of related diseases. In this research, Cu(II) modified TADH COF, which has been prepared by Cu2+ post-synthesis modification of the COF obtained through a condensation reaction of 1,3,5-(4-aminophenyl) benzene (TAPB) and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (DHTP), and methylene blue (MB) molecules are combined to construct a ratiometric electrochemical sensor for achieving specific and ultra-sensitive detection of GSH. As a stable and active covalent organic framework material, TADH COF possesses the special O(–OH) and N(C N) binding sites, which can load and coordinate with Cu2+ effectively. The obtained Cu(II)-TADH COF serves as a sensitive electrode material for sensing GSH due to "extrusion effect" caused CuCl solid-state electrochemical signal degeneration by the specific binding of Cu and GSH while MB provides a stable electrical signal in the electrochemical sensing process as an internal reference for eliminating errors and making the detection results more accurate. The constructed electrochemical sensing platform Cu(II)-TADH COF/MB/GCE exhibited an ultrahigh sensitivity with a limit of detection (LOD) of 0.0093 nM (S/N = 3), wide linear range of 0.05 nM–40 μM and high accuracy. For the detection of GSH in real samples including human blood, serum and urine samples, the sensor also showed excellent sensing performance. This is the first research on ratiometric electrochemical sensing platform for the ultra-sensitive detection of glutathione based on covalent organic frameworks, which provides an original and novel strategy for the electrochemical detection of GSH with COF materials. [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]

The detection of acetaminophen (ACOP) and its toxic hydrolyzed product p-aminophenol (4-AP) is very significant for clinical diagnosis and quality control of drug formulation. In this study, a novel electrochemical sensor based on MoS 2 embedding triangular Ag nanoplates (Tri-AgNPs) coated MOF-808 was developed for simultaneous and sensitive detection of ACOP and 4-AP. The morphology and structure MOF-808@MoS 2 /Tri-AgNPs nanocomposite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and so on. The electrochemical and electrocatalytic properties of the composite electrode were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results demonstrated that the constructed sensor had excellent electrochemical performance for ACOP and 4-AP detection due to the synergistic interaction among MOF-808, MoS 2 and Tri-AgNPs. The proposed sensor exhibited a wide linear range (1–450 μM) and low limits of detection for detection of ACOP (0.054 μM) and 4-AP (0.046 μM). At the same time, the sensor also showed outstanding repeatability, reproducibility, stability and selectivity. In addition, MOF-808@MoS 2 /Tri-AgNPs/GCE was also employed to determine ACOP and 4-AP in acetaminophen tablets and Yellow River water samples with satisfactory recovery rates, which indicated the feasibility of the developed electrochemical sensor in the actual sample analysis. [Display omitted] • MOF-808 coating by conductive MoS 2 improves the conductivity of MOF-808 composite. • Tri-AgNPs embedding in MoS 2 disperses MoS 2 and AgNPs and enhances active sites. • Synergy of MoS 2 , Tri-AgNPs and MOF-808 ensures high detection sensitivity of ACOP and 4-AP. [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]

A novel self-probing, gate-controlled, molecularly imprinted electrochemical sensor for ultrasensitive and highly selective determination of p -nonylphenol was prepared, based on a GCE electrode modified with Au nanoparticles and multiwalled carbon nanotubes/reduced graphene oxide nanoribbons (MWCNTs@rGONRs). The molecularly imprinted film was produced using p -aminothiophenol as the functional monomer, p -nonylphenol as the template molecule and tetrabutylammonium perchlorate as the supporting electrolyte. The modified electrode had specific recognition for the template molecule and very high electrocatalytical activity for electroreduction of the target molecule. The resulting sensor has been successfully used to determine p -nonylphenol using cyclic voltammetry and cathodic stripping different pulse voltammetry with detection limits of 0.73 pM ( S / N  = 3) and 4.8 fM ( S / N  = 3), respectively. The method demonstrated extremely high sensitivity and selectivity as well as a wide linear range and could be used to detect p -nonylphenol in environmental and food samples. [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]

[Display omitted] • S-CTFs nanospheres was prepared and used to build an electrochemical sensor. • Nickel cobaltite (NiCo 2 O 4) nanoflowers were in situ formed on S-CTFs. • S-CTFs@NiCo 2 O 4 modified electrode exhibited the outstanding synergetic effect of S-CTFs and NiCo 2 O 4. • The sensor showed high sensitivity for simultaneous detection of ACOP and 4-AP. Owing to the high toxicity of acetaminophen (ACOP) and 4-aminophenol (4-AP) when they are overused, the simultaneous determination of ACOP and 4-AP is crucial. In this present paper, an electrochemical sensor based on the nanocomposite of sulfurbridged covalent triazine frameworks (S-CTFs) and in situ formed nickel cobaltite (NiCo 2 O 4) nanoflowers on S-CTFs, denoted as S-CTFs@NiCo 2 O 4 , was fabricated for the first time for sensitive detection of ACOP and 4-AP. S-CTFs@NiCo 2 O 4 modified electrode exhibited the outstanding synergetic effects of S-CTFs (prominent enrichment ability and large surface area) and NiCo 2 O 4 (excellent electrocatalytic activity). The developed electrode had the advantages of high reproducibility, repeatability, anti-interference and stability, and it exhibited a wide linear concentration range (2 ∼ 360 μM) and a low limit of detection (0.18 μM and 0.35 μM) for ACOP and 4-AP, respectively. In addition, the designed electrochemical sensor was evaluated towards the detecting ACOP and 4-AP in real samples with satisfactory recovery, illustrating that electrode has a broad prospect in the clinical application. [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]

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]

In this article, an electrochemical sensor for the sensitive detection of guanine and adenine was constructed, which was modified only by nitrogen-rich covalent organic framework (TQBQ-COF) without other conductive additives. TQBQ-COF was synthesized by a condensation reaction of triquinoyl (TQ) and tetramino-benzoquinone (TABQ). Its rich nitrogen content and porosity provided a strong enrichment ability for guest molecules and full conjugated structure ensured high electrical conductivity, which allowed it to be employed as an electrochemical sensing material for sensitive detection of guanine and adenine. The conductivity of TQBQ-COF was 6.06 × 10−3 S/cm (301 K, 45%) by using four-terminal method ST2722-SD with a ST2643 high resistance meter. The electrochemical performances of the COF/GCE were verified by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The detection limits of guanine and adenine on COF/GCE were 0.20 μM and 0.33 μM, and the linear ranges were 1.5–150 μM and 0.6–150 μM, respectively. Moreover, the suggested sensor had remarkable stability and anti-interference performance, as well as excellent repeatability. It displayed a high accuracy when analysing the real sample. Therefore, TQBQ-COF with semiconducting property becomes a simple and effective candidate in the field of electrochemical sensing. [Display omitted] • A simple electrochemical sensor based on a full conjugated nitrogen-rich COF without conductive additive was reported. • TQBQ-COF had high conductivity and rich nitrogen content. • COF/GCE had sensitive and selective responses for guanine (G) and adenine (A). • The sensor could be used to detect G and A in actual 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 COF based electrochemical sensor is successfully fabricated by employing TFPB-BD-COF prepared through condensation reaction of 1, 3, 5-tris-(4-formylphenyl) benzene (TFPB) and benzidine (BD), in-situ reduced platinum nanoparticles (PtNPs) and amino functionalized multi-walled carbon nanotubes (NH 2 -MWCNTs) as modified materials for sensitive electrochemical determination of catechol (CC), hydroquinone (HQ) and resorcinol (RS) simultaneously. The obtained TFPB-BD-COF/PtNPs/NH 2 -MWCNTs/GCE exhibits superior electrochemical performance compared with those modified by individual components. The oxidation peaks of CC, HQ and RS show good linear response in the concentration ranges of 0.2–360 μM, 0.2–360 μM and 4–360 μM, respectively. The corresponding limits of detection (LODs) of CC, HQ and RS were 0.015 μM, 0.022 μM and 0.26 μM (S/N = 3). In addition, it possesses outstanding selectivity, repeatability, reproducibility and stability. The proposed modified electrode has been successfully applied for the determination of HQ, CC and RS in tap water, Yellow River water and domestic wastewater with satisfactory. [Display omitted] [ABSTRACT FROM AUTHOR]

In this present paper, a novel electrochemical sensor based on a covalent organic framework (COF) and lanthanum oxide (La 2 O 3) and multi-wall carbon nanotubes (MWCNT S) was prepared for sensitive and selective detection of dopamine (DA) and uric acid (UA). The sensor demonstrated excellent analytical performance for DA and UA owing to the synergistic effect among large surface area of COF, highly conducting MWCNTs and highly catalytic La 2 O 3. Particularly, the COF with a BET surface area of 1396.04 m2/g prepared by the Schiff base reaction between 2, 5-dibromobenzene-1, 4-dicarbaldehyde (DBTA) and 2, 4, 6-tris(4-aminophenyl)− 1, 3, 5-triazine (TAPT), significantly enhanced the adsorption and enrichment ability of the resulted modified electrode toward the target molecules. The constructed electrochemical sensor possessed low detection limits (0.039 μM for DA and 0.024 μM for UA) and wide linear ranges (2 ~ 450 μM for DA and 0.4 ~ 450 μM for UA) and could be employed to detect simultaneously the contents of DA and UA in biological and medicine samples with outstanding reproducibility, high stability as well as strong anti-interference property. [Display omitted] [ABSTRACT FROM AUTHOR]

As a new kind of porous organic material, covalent organic framework materials (COFs) have many advantages and have been widely used in catalysis, sensing, drug delivery, gas separation and other fields. In this paper, A COF was successfully prepared based on Schiff base reaction of 1, 3, 6, 8-tetrakis(4-formyl phenyl) pyrene (TFPPy) and 1, 3, 6, 8-tetrakis(4-amino phenyl) pyrene (PyTTA) named as TF-Py COF, and its structure was characterized in detail. By physically combining a pre-prepared three-dimensional carbon material containing nitrogen (3D NCNF-T) and TF-Py COF, followed by deposition of AuNPs, relatively poor conductivity of TF-Py COF was efficiently overcome and a novel electrochemical sensing platform with high sensitivity and high selectivity for simultaneous detection of acetaminophen (ACOP) and 4-aminophenol (4-AP) was successfully constructed. The synergistic effect between TF-Py COF, 3D NCNF-T and AuNPs effectively improves the analytical sensitivity of target analytes. Under optimized experimental conditions, the electrochemical sensing platform has a sensitive volt-ampere response and a wide linear range to both ACOP and 4-AP, and the detection limits are 0.13 μM and 0.05 μM (S/N = 3), respectively. The sensor has been successfully applied to the determination of ACOP and 4-AP in acetaminophen tablets and Yellow River water samples, with high recovery rate, good selectivity and reproducibility, and strong anti-interference ability. It is expected to be widely used in the actual sample detection. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, a novel sensor based on gold nanoparticle-modified zirconium-metal-organic frameworks (MOF-801) and carboxyl-functionalized carbon nanotube (MWCNT-COOH) composite material was built successfully for electrochemical detection of guanine and adenine in DNA sample, which exhibits diverse advantages such as fast, convenience and high efficiency. Guanine and adenine were detected by the cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimal conditions, MOF-801/MWCNT-COOH/ AuNPs/GCE delivered linear DPV responses to guanine in the range of 0.8 ~ 60, 60 ~ 180 μM and the adenine in the range of 0.8 ~ 60, 60 ~ 180 μM with the low detection limit of 0.09 μM for guanine and 0.08 μM for adenine, respectively. The advantages of this method include simplicity, rapidity, high sensitivity, good selectivity as well as low cost. The modified GCE was successfully applied to the analysis of guanine and adenine in DNA samples. [Display omitted] • A new electrochemical sensor MOF-801/MWCNT-COOHs/AuNPs/GCE is prepared to simultaneously detecting guanine and adenine. • MWCNT-COOHs and AuNPs greatly improve the conductivity of the sensor and the resulted sensitivity. • This electrochemical sensor has good selectivity and sensitivity. [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] • CNT/MOF-74 materials are prepared and their electrochemical properties compared. • CNT/Ni-MOF-74 derived 0.2CNT/NiSe x has excellent electrochemical performance. • 0.2CNT/NiSe x is used for not only supercapacitors but also electrochemical sensors. • CNTs improve specific capacitance and conductivity of the composite simultaneously. Selenides derived from MOFs have attracted attention as the materials with excellent electrochemical properties. CNT/MOF-74 composites are successfully synthesized by a simple hydrothermal method. Then CNT/Ni-MOF-74 materials are selected as the precursors for further selenization to prepare CNT/NiSe x. The results show that 0.2CNT/NiSe x derived from CNT/Ni-MOF-74 prepared in the presence of 0.2 g CNTs has the best electrochemical performance as electrochemical capacitor electrode, which exhibits the highest specific capacitance of 2136 F·g−1 at a current density of 1 A·g−1. In addition, a hybrid electrochemical capacitor (HEC) is assembled with 0.2CNT/NiSe x and activated carbon (AC). The obtained 0.2CNT/NiSe x //AC HEC shows a high energy density of 59 Wh·kg−1 at a power density of 800 W·kg−1. In order to expand the application of the composition material, a 0.2CNT/NiSe x /GCE electrochemical sensor is prepared. The results show that 0.2CNT/NiSe x /GCE electrochemical sensor can be used for simultaneous determination of acetaminophen (AMP) and dopamine (DA). [ABSTRACT FROM AUTHOR]

• The work employing MWCNTs-COOH, MCOFs and CoNPs to build a sensor was first reported. • The sensor displayed high sensitivity and wide linear range for the simultaneous determination of guanine and adenine. • MCOFs can serve as a promising candidate as modified electrode material. Covalent organic frameworks (COFs) offer high surface area, ordered π conjugation system, tunable pore size and structure which are useful for developing electrochemical sensor. However, most COFs were poor conductivity and slow charge transfer rate which restrict their application in electrochemical sensor. Metal-covalent organic frameworks (MCOFs) possess the good electroconductivity and catalytic activity. In addition, the periodic arrays of π clouds of layered 2D structure facilitate charge transport. Here we propose a new strategy to construct a novel electrochemical sensor employing MCOFs (CuP-SQ COF). The fabricated sensor MWCNTs-COOH/CuP-SQ COF/Co NPs/GCE exhibits the excellent performance for the simultaneous determination of DNA base (guanine and adenine) with high sensitivity which can be attributed to the outstanding properties, unique structure and synergistic effect of composites. The wider concentration range of simultaneous quantitive analysis were 0.04 to 130 μM for guanine and 0.06 to 130 μM for adenine. The lower detection limits were 5.5 nM and 7.2 nM (S/N = 3), respectively. This work proves MCOFs can serve as a promising candidate as modified electrode material for developing electrochemical sensor. [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]

An electrochemical sensing platform for simultaneous determination of dopamine (DA) and uric acid (UA) is constructed based on covalent organic framework materials (IL COF-1), aminofunctionalized carbon nanotubes (MWCNT-NH 2), and gold nanoparticles (AuNPs). The prepared sensor shows a good performance in detection of DA and UA due to porosity, large specific surface area, high conductivity and more active sites of the composite modified material. Under optimized experimental conditions, the constructed electrochemical sensor has sensitive response and good linearity to both DA and UA. Their wide linear ranges are 0.7–108 μM and 0.97–200 μM, and the detection limits are 0.21 μM and 0.29 μM (S/N = 3), respectively. The developed method has been successfully employed to determine the contents of DA and UA in dopamine injection and human urine samples. It has a satisfactory recovery rate, and the relative standard deviations (RSD) of three parallel determinations are all below 5.0%. In comparison, the constructed sensor platform has superior performance including low cost, simple structure, wide linear range and high sensitivity than some traditional methods, which is expected to be widely used in real sample analysis. Unlabelled Image • The electrochemical sensor based on IL COF-1 is used to simultaneously detect dopamine(DA) and uric acid (UA). • The porous IL COF-1 with pyrene groups effectively increases binding sites on the electrode surface. • MWCNT-NH 2 and AuNPs greatly improve the conductivity and sensitivity of the sensor platform. [ABSTRACT FROM AUTHOR]

• The prepared procedure of the composite material is simple, mild and efficient. • ZIF-67/MWCNT-COOH/Nafion/GCE shows good analytical performance for 4-AP and AMP. • The synergy of the ZIF and MWCNT-COOH improved the current response of the targets. • The obtained sensor possessed remarkable stability and interference. • The sensing platform showed feasibility and reliability of real sample determination. Herein, a novel electrochemical sensor based on ZIF-67/MWCNT-COOH/Nafion composite was designed and prepared for simultaneous detection of 4-aminophenol (4-AP) and acetaminophen (AMP). The electrochemical behaviors of the 4-AP and AMP on the ZIF-67/MWCNT-COOH/Nafion electrode were explored via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results exhibited that the designed electrochemical sensor possessed superior electrocatalytic activity for 4-AP and AMP, which was attributed to the highly ordered porous structure of ZIF-67, the outstanding electrical conductivity and high electrocatalytic activity of MWCNT-COOH. Under optimization conditions, the DPV response of the prepared electrode depicted a wider linear response concentration range of 0.2 to 200 μM for 4-AP, and 0.1 to 100 μM for AMP, respectively. And the lower detection limits (LOD) of 0.01 and 0.07 μM were obtained for 4-AP and AMP, respectively. More importantly, the acquired electrode was applied to Yellow river water and Paracetamol tablets for analysis of 4-AP and AMP, which exhibited satisfying recovery of 98.2% ~ 106.7% for 4-AP and 94.7% ~ 99.6% for AMP, respectively. In a word, the constructed electrochemical sensing platform delivered a promising potential in real application. [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]