Synergetic Effects between a Bipyridyl-Functionalized Metal-Organic Framework and Graphene for Sensitive Electrochemical Detection of Norepinephrine

Abstract

A sensitive and simple electrochemical sensor for determination of norepinephrine (NE) was developed. The electrode (ERG-UiO-67-bpy/GCE) was fabricated by modifying the glassy carbon electrode with a Zr (IV) metal-organic framework (MOF) with 2,2 -bipyridyl-5,5 -dicarboxylate (UiO-67-bpy) and graphene oxide (GO), followed by electrochemical reduction of GO to ERG (electrochemically reduced graphene). The ERG and UiO-67-bpy components of the composite electrode show a synergic electrocatalytic effect, leading to much enhanced voltammetric response to the oxidation of NE. Comparative studies indicate that the hydrogen bonds between the bipyridyl moiety of the MOF and the 2-aminoethanol moiety of NE play an important role in promoting electron transfer on the electrode surface. Differential pulse voltammetry using the composite electrode shows a wide linear-response concentration range with a submicromolar detection limit of 0.026 μM. The sensor shows good reproducibility and stability and also be used for sensitive simultaneous detection of NE and uric acid.

Insight into the Influence of Analyte Molecular Structure Targeted on MoS2-GO-Coated Electrochemical Nanosensors

“…From another aspect of molecular structure, 4-NP has a distinct benzene ring structure with less bulky active functional groups and high compatibility to GO structure. Thus, it can enhance the adsorption ability of 4-NP as well electron transport from MoS 2 -GO materials to 4-NP via direct pathways owing to the conjugation effect, synergistic effect, and π–π stacking electrostatic interactions or even electrostatic attraction of the hydroxyl groups between the electrode surface and 4-NP. ,,, This is further confirmed via the electron transfer rate constant ( k s ) calculated when the k s value of 4-NP was higher about 1.32 times than CLB.…”

“…Thus, it can enhance the adsorption ability of 4-NP as well electron transport from MoS 2 -GO materials to 4-NP via direct pathways owing to the conjugation effect, synergistic effect, and π−π stacking electrostatic interactions or even electrostatic attraction of the hydroxyl groups between the electrode surface and 4-NP. 27,34,37,38 This is further confirmed via the electron transfer rate constant (k s ) calculated when the k s value of 4-NP was higher about 1.32 times than CLB. Furthermore, the various molecular structural features between CLB and 4-NP led to large differences in the adsorption capacity (Γ) and accumulation time for CLB and 4-NP.…”

A Cu-functionalized MOF and multi-walled carbon nanotube composite modified electrode for the simultaneous determination of hydroquinone and catechol

“…The high specic surface area, adjustable pore size, customizable functions, and excellent stability endow MOFs with great opportunities in loading or blending with other raw materials, resulting in diverse and unique characteristics, including electrochemical sensing. [17][18][19] However, poor electron conductivity becomes a kinetic bottleneck impeding the electrocatalytic performances of most MOFs. 20 To improve the conductivity of MOFs and maximally retain their unique pore structure, many different approaches were proposed, including (i) introducing specic groups such as -COOH, -SO 3 H, -SH, and -NH 2 into the host framework or coordinative insertion of the functional component through pre-design or post-synthetic modication (PSM); 21 (ii) encapsulating conducting guest molecules (such as redox-active molecules, metal nanoparticles, and metal nanoclusters); 22,23 (iii) pairing metals with ligands containing chelating groups to extend conjugation.…”

Double Cationization Approach toward Ionic Metal–Organic Frameworks with a High Bromide Content for CO2 Cycloaddition to Epoxides

“…Metal–organic frameworks (MOFs) are a relatively new class of hybrid compounds that show widely tunable porosity and functions, and they are attracting multidisciplinary attention for their versatile applications. − Heterogeneous catalysis is one of the most promising applications because MOFs can be designed to bear various endo - or exogenous catalytic ingredients. − The CEC reaction has been attempted with MOFs with accessible Lewis acid and/or base sites. − However, for most of the studied MOF catalysts (and other solid catalysts), the high catalytic activity for CEC requires the simultaneous use of a homogeneous organic halide (usually tetrabutylammonium bromide (TBAB) in large excess compared to the solid catalysts). The halide cocatalyst provides the free nucleophilic anion to open the activated epoxide ring, − but its use sacrifices the heterogeneity.…”