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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]

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]

Creatinine (Cre) measurement in biological fluids is an increasingly important clinical measure for evaluating renal insufficiency, thyroid dysfunction, and muscle injury. Therefore, a simple, fast, and reliable Cre analysis method is of great significance to human health. Herein, a novel ratiometric fluorescence sensor, Ag-Eu-MOF-808-EDTA, was synthesized by introducing ethylenediaminetetraacetic acid (EDTA), Ag+, and Eu3+ into the framework of MOF-808 through three steps of post-synthesis modification, and was used to detect Cre in PBS buffer of pH 7.2 at 35 °C with a "turn-on" ratio response in the presence of various interfering ions and several biomolecules. In this strategy, the characteristic emission of Eu3+ at 551 nm can be turned on due to coordination between Cre and Ag+, while emission at 613 nm is independent of Cre, which produces a significant ratio response change throughout the cycle. Experimental results showed that the ratio fluorescence sensor displayed a wide linear range for Cre from 0.5 to 350 μM with a low detection limit of 0.42 μM. Finally, a good recovery rate (96.7–102.9%) and appropriate relative standard deviation (RSD <2.39%, n = 3) were obtained during the determination of creatinine in real urine and serum. This work provides additional insights into the detection of creatinine in clinical blood samples. [Display omitted] • Ag-Eu-MOF-808-EDTA was prepared by three-step post-synthetic modification. • The material was used for a ratiometric fluorescence sensing of creatinine. • The ratiometric sensor showed a wide linear range and low detection limit for Cre. [ABSTRACT FROM AUTHOR]

A new two-dimensional covalent organic framework (DBT-MA-COF) is designed and synthesized via Carbon–Nitrogen coupling reaction by using 2,5-dibromothiophene (DBT) and melamine (MA) as the monomers. The C−Hˑ N intralayer hydrogen bonding exists in the structure of DBT-MA-COF so that a plane rigid structure can be maintained. The material exhibits a quasi-reversible redox process caused by triazine units and the transformation of the quinone and aromatic structures to make the DBT-MA-COF possess pseudocapacitive characteristics. DBT-MA-COF has high heteroatom content for the existence of triazine and thiophene units, which can accelerate the transfer of electrolyte ions on the surface of DBT-MA-COF electrode and improve the solution conductivity of the material. The assembled asymmetric supercapacitor DBT-MA-COF//C-CTS ASC has a high energy density of 32.1 W h kg−1 with the power density of 800 W kg−1. The cycle life of the device is excellent which can reach 83% even after 30,000 continuous galvanostatic charge-discharge cycles. The strategy in this work provides a line of thinking to design and prepare new COFs used as long life and pseudocapacitive supercapacitor materials. Image 1 • A novel covalent organic framework(DBT-MA-COF) is synthesized via Carbon-Nitrogen coupling reaction. • C-H...N intralayer hydrogen bonding existed in DBT-MA-COF leads to a plane rigid structure. • The COF has pseudocapacitive characteristics for a transformation of quinone and aromatic structures in triazine unit. • The existence of triazine and thiophene units improves the conductivity of the resulting material. • Assembled asymmetric supercapacitor shows a high energy density of 32.1Wh kg-1 and the long life of 83% after 30000 cycles. [ABSTRACT FROM AUTHOR]