High Performance Electrocatalyst Based on MIL-101(Cr)/Reduced Graphene Oxide Composite: Facile Synthesis and Electrochemical Detections

A Dual-Functional and Efficient MOF-5@MWCNTs Electrochemical Sensing Device for the Measurement of Trace-Level Acetaminophenol and Dopamine

The design and construction of dual-functional and high-efficiency electrochemical sensors are necessary for quantitative detection. In this work, a zinc-based metal-organic framework (MOF-5) and multi-walled carbon nanotubes (MWCNTs) were combined in situ through a simple solvothermal reaction to obtain an MOF-5@MWCNTs composite. The composite exhibits a large surface area, hierarchical pore structure, excellent conductivity, and enhanced electrochemical performance in the detection of acetaminophenol (AP) and dopamine (DA). Remarkably, the synergistic effects between MOF-5 and MWCNTs enable the electrochemical sensor based on the MOF-5@MWCNTs composite to quantitatively determine AP and DA at trace levels. Under optimal conditions, the proposed sensor features relatively wide linear ranges of 0.005-600 μM and 0.1-60 μM for AP and DA, respectively, with very low detection limits (LODs) of 0.061 μM and 0.0075 μM for AP and DA. Importantly, this electrochemical sensor demonstrates excellent reproducibility, stability, and anti-interference ability, making it suitable for practical applications in the detection of AP and DA in urine and tap water samples with acceptable recoveries. The successful integration of MOF-5 with MWCNTs results in a robust and versatile electrochemical sensing platform for the rapid and reliable detection of AP and DA at trace levels.

Efficient detection of metronidazole by a glassy carbon electrode modified with a composite of a cyclotriveratrylene-based metal-organic framework and multi-walled carbon nanotubes

Constructing a sensitive and efficient sensor for determination of metronidazole (MNZ) is crucial in food field. Herein, a new cyclotriveratrylene-based metal-organic framework (MOF), namely, [Cd₆L₂(cyclen)₂(H₂O)₂] (1), was constructed by self-assembly of functionalized 5,6,12,13,19,20-hexacarboxy-propoxy-cyclotriveratrylene (H₆L), 1,4,7,10-tetraazacyclododecane (cyclen) and Cd(II) cation under solvothermal condition. In 1, adjacent Cd(II) cations are linked by L^6- to produce a 2D polymeric structure with carboxylate and phenolic oxygen atoms. To enhance conductivity of 1, it was combined with conducting carbon materials, including mesoporous carbon (MC), reduced graphene oxide (RGO) and multi-walled carbon nanotubes (MWCNT), respectively, producing a series of composite materials. Remarkably, electrochemical tests showed that 1@MWCNT(1:1) featured a much better electrochemical detection performance for metronidazole (MNZ) than 1@MC and 1@RGO. The linear range for the detection of MNZ is up to 0.4-500 μM and the limit of detection (LOD) for MNZ reached 0.25 μM. Importantly, the fabricated sensor 1@MWCNT(1:1) was employed for the detection of MNZ in honey and egg with satisfactory result. High-performance liquid chromatography (HPLC) validated the high accuracy of the electrochemical method for the determination of honey and egg.

Surfactant assisted Cr-metal organic framework for the detection of bisphenol A in dust from E-waste recycling area

Due to their highly porous structures, metal organic framework materials are widely used in analytic areas. In this paper, Cr-metal organic framework (MIL-101(Cr)) modified electrode was prepared and then was used as electrochemical sensor for the detection of bisphenol A (BPA). By using one kind of surfactant of cetyltrimethylammonium bromide (CTAB), the analytic performances of MIL-101 (Cr) towards BPA detection were greatly improved. Compared with pure MIL-101 (Cr), the differential pulse voltammetry (DPV) behavior of CTAB/MIL-101 (Cr) was improved 3.0 times in the presence of BPA. The hydrophobic long chain alkanes of CTAB can improve the enrichment and electrochemical oxidation for BPA. The CTAB/MIL-101 (Cr) sensor exhibited a linear range from 20 to 350 nM and a low detection limit of 9.95 nM (LOD = 3s_b/S) and showed good reproducibility, stability and selectivity. Finally, real samples of dusts from E-waste recycling area in South China were collected and the CTAB/MIL-101 (Cr) sensor demonstrated satisfactory results for BPA detection from these dust samples.

Photo-electrochemical detection of dopamine in human urine and calf serum based on MIL-101 (Cr)/carbon black

A new photo-electrochemical sensor based on MIL-101(Cr) MOF/carbon black (CB) is fabricated and characterized. By using differential pulse voltammetry, dopamine (DA) can be effectively detected using a photo-electrochemical MIL-101(Cr)/CB sensor under visible light. The CB acts as the electron bridge to combine with the large specific surface area and photo-catalytic feature of MOF, which contribute to the improvements of sensitivity of DA detection. The concentration of the catalyst, pH value, accumulation potential, and accumulation time were also optimized. Furthermore, the electrochemical performances of MIL-101(Cr)/CB sensor was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scan rate, electrochemically active surface area (ECSA), and amperometric responses. A detection limit of 0.38 nM (LOD = 3 s_b/S, s_b = 0.028) and a working range of 1 nM to 2.22 μM has been achieved. The MIL-101(Cr)/CB sensor exhibits excellent reproducibility, stability, and selectivity and also has satisfactory recovery rate for the analysis of real samples including calf serum and human urine. Graphical abstract.

Recent Advances in Porphyrin-Based Materials for Metal Ions Detection

Porphyrins have planar and conjugated structures, good optical properties, and other special functional properties. Owing to these excellent properties, in recent years, porphyrins and their analogues have emerged as a multifunctional platform for chemical sensors. The rich chemistry of these molecules offers many possibilities for metal ions detection. This review mainly discusses two types of molecular porphyrin and porphyrin composite sensors for metal ions detection, because porphyrins can be functionalized to improve their functional properties, which can introduce more chemical and functional sites. According to the different application materials, the section of porphyrin composite sensors is divided into five sub-categories: (1) porphyrin film, (2) porphyrin metal complex, (3) metal–organic frameworks, (4) graphene materials, and (5) other materials, respectively.

Sensing organic analytes by metal–organic frameworks: a new way of considering the topic

In this review, our goal is comparison of advantageous and disadvantageous of MOFs about signal-transduction in different instrumental methods for detection of different categories of organic analytes.

Graphite paste electrodes modified with a sulfo-functionalized metal-organic framework (type MIL-101) for voltammetric sensing of dopamine

The metal-organic frameworks MIL-101 and sulfo-MIL-101 were used to modify graphite paste electrodes (GPEs) to obtain sensors for determination of dopamine (DA). Taking advantage of the catalytic activity of metal-organic frameworks (MOFs) and of the electrical conductivity of graphite, the modified GPEs show enhanced voltammetric responses, and the GPE modified with the sulfo-MOF displays superior sensitivity when operated at a working potential of -0.4 to 0.8 V (vs. Ag/AgCl). The sensor works in the 0.07 to100 μM DA concentration range and has a 43 nM detection limit. It is concluded that the sulfo group provides open sites for efficient electrostatic and hydrogen bonding interactions, which facilitates electron transfer. Graphical abstractSchematic representation of the structure of the sulfo-functionalized MOF (sulfo-MIL-101) and the different voltammetric signals of dopamine at the graphite paste electrodes (GPEs) modified with sulfo-MIL-101 and the parent MOF (MIL-101).

Chemically modified electrodes with MOFs for the determination of inorganic and organic analytes via voltammetric techniques: a critical review

Current status on MOF-modified electrodes for voltammetric analyses of inorganic/organic species is critically discussed. We provide future research directions and specific criteria that MOFs should satisfy prior to their use as electrode modifiers.