Capacity building in porous materials research for sustainable energy applications

The project aimed to develop porous materials for sustainable energy applications, namely, hydrogen storage, and valorization of biomass to renewable fuels. At the core of the project was a training programme for Africa-based researchers in (i) the exploitation of renewable locally available raw materials; (ii) the use of advanced state-of-the-art techniques for the design and synthesis of porous materials (zeolites and metal-organic frameworks (MOFs)) for energy storage; and (iii) the valorization of sustainable low-value feedstock to renewable fuels. We found that compaction of the UiO-66 MOF at high pressure improves volumetric hydrogen storage capacity without any loss in gravimetric uptake, and experimentally demonstrated the temperature-dependent dynamic behaviour of UiO-66, which allowed us to propose an activation temperature of ≤ 150°C for UiO-66. Co-pelletization was used to fabricate UiO-66/nanofibre monoliths as hierarchical porous materials with enhanced usable (i.e. deliverable) hydrogen storage capacity. We clarified the use of naturally occurring kaolin as a source of silica and alumina species for zeolite synthesis. The kaolin-derived zeolite X was successfully used as a catalyst for the transesterification of Jatropha curcas oil (from non-edible biomass) to biodiesel. We also prepared porous composites (i.e. carbon/UiO-66, organoclay/UiO-66 and zeolite/carbon) that were successfully applied in electrochemical sensing.

Solvothermal synthesis of organoclay/Cu-MOF composite and its application in film modified GCE for simultaneous electrochemical detection of deoxyepinephrine, acetaminophen and tyrosine

An organoclay/copper-based metal-organic framework (MOF) composite was synthesized using a solvothermal method by growing a Cu-BTC (copper(ii) benzene-1,3,5-tricarboxylate) MOF from a mixture of the MOF precursor solution in which various amounts of organoclay had been dispersed. The organoclay was obtained by intercalating a cationic dye, namely thionin, into a natural Cameroonian clay sampled in Sagba deposit (North West of Cameroon). The organoclay and the as-synthesized composites were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) techniques. From Scherrer's equation, the crystallite size of the composite was found to be between 55 and 58 nm, twice as large as the pristine MOF's crystallite size. The organoclay/Cu-MOF composite (Sa-TN₅₀/Cu₃(BTC)₂) exhibiting a BET surface area of 192 m² g^-1, about twice that of pristine clay and about one seventh that of pristine MOF, was then utilized to form a stable thin film onto glassy carbon electrodes (GCE) by drop coating (Sa-TN₅₀/Cu₃(BTC)₂/GCE). These electrodes demonstrated electrocatalytic behavior toward deoxyepinephrine (DXEP) and thus enabled selective and simultaneous sensitive detection of three analytes: DXEP, acetaminophen (AC) and tyrosine (TYR) compared with bare GCE and clay modified electrode. Under optimum conditions, Sa-TN₅₀/Cu₃(BTC)₂/GCE exhibited good performance including large calibration curves ranging from 5.0 μM to 138.0 μM for DXEP, 4.0 μM to 153.0 μM for AC and 1.0 μM to 29.4 μM for TYR. The detection limits were found to be, 0.4 μM, 0.7 μM and 0.2 μM for DXEP, AC and TYR, respectively. The developed sensors have been applied successfully in the quantification of AC in a commercial tablet of AC, and DXEP, AC and TYR in tap water.

A bibliometric analysis of graphene in acetaminophen detection: Current status, development, and future directions

Acetaminophen is a widely used analgesic throughout the world. Detection of acetaminophen has particular value in pharmacy and clinics. Electrochemical sensors assembled with advanced materials are an effective method for the rapid detection of acetaminophen. Graphene-based carbon nanomaterials have been extensively investigated for potential analytical applications in the last decade. In this article, we selected papers containing both graphene and acetaminophen. Bibliometrics was used to analyze the relationships and trends among these papers. The results show that the topic has grown at a high rate since 2009. Among them, the detection of acetaminophen by an electrochemical sensor based on graphene is the most important direction. Graphene has moved from being a primary sensing material to a substrate for immobilization of other active ingredients. In addition, the degradation of acetaminophen using graphene-modified electrodes is also an important direction. We analyzed the research history and current status of this topic through bibliometrics. Authors, institutions, countries, and key literature were discussed. We also proposed perspectives for this topic.

Ultrasensitive Electrochemical Sensor for Luteolin Based on Zirconium Metal-Organic Framework UiO-66/Reduced Graphene Oxide Composite Modified Glass Carbon Electrode

Luteolin is a kind of natural flavonoid with many bioactivities purified from a variety of natural herbs, fruits and vegetables. Electrochemical sensing has become an outstanding technology for the detection of luteolin in low concentration due to its fast response, easy operation and low cost. In this study, electroreduced graphene oxide (ErGO) and UiO-66 were successively modified onto a glassy carbon electrode (UiO-66/ErGO/GCE) and applied to the detection of luteolin. A combination of UiO-66 and ErGO showed the highest promotion in the oxidation peak current for luteolin compared with those of a single component. The factors affecting the electrochemical behavior of UiO-66/ErGO/GCE were evaluated and optimized including pH, accumulation potential, accumulation time and scan rate. Under optimum conditions, UiO-66/ErGO/GCE showed satisfactory linearity (from 0.001 μM to 20 μM), reproducibility and storage stability. The detection limit of UiO-66/ErGO/GCE reached 0.75 nM of luteolin and was suitable for testing real samples. Stable detection could be provided at least eight times by one modified electrode, which guaranteed the practicability of the proposed sensor. The fabricated UiO-66/ErGO/GCE showed a rapid electrochemical response and low consumption of materials in the detection of luteolin. It also showed satisfactory accuracy for real samples with good recovery. In conclusion, the modification using MOFs and graphene materials made the electrode advanced property in electrochemical sensing of natural active compounds.