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Aryl diazonium modification for improved graphite fiber brush in microbial fuel cell

Siti Farah Nadiah Rusli, Mimi Hani Abu Bakar, Loh Kee Shyuan, Mohd Shahbudin Mastar, Seratul Jemiah Abdul Rani, Mohd Shahbudin Mastar

Sains Malaysiana, 2018;47:3017-3023.

Aryl diazonium salts are coupling agents that assist in molecules attachment to interfaces for sensing purposes. Despite
not being fully explored and not yet widely applicable for cell-based sensors, the high stability of aryl diazonium salt
formed sensing system is highly favorable in biological applications. Carbon-based electrodes are the most commonly
used in aryl diazonium modification due to its post grafting stable C-C bond formation. Here, salt bridge based microbial
fuel cells (MFCs) were used to study on the effect of aryl diazonium modification on the anode graphite fibre brush. Aryl
diazonium salts were in situ generated by the diazonation of p-phenylenediamine with NaNO2 in HCl solution. The
electrochemical performance of the aryl diazonium modified graphite brush MFC was measured and compared with the
unmodified graphite brush MFC. The power output of the modified graphite brush bioanode was higher (8.33 W/m3
)
than the unmodified graphite brush (7.60 W/m3
) after 20 days of operation with ferricyanide as the catholyte. After 70
days of operation using phosphate buffer solution as the catholyte, the Pmax of modified brush was three times higher
(0.06 W/m3
) than of the unmodified brush (0.02 W/m3
), which indicates an enhanced binding towards the substrate that
facilitates a better electron transfer between the microbial and electrode surface.

Matched MeSH terms: Ferricyanides
Fulltext Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

Basirun WJ, Sookhakian M, Baradaran S, Mahmoudian MR, Ebadi M

Nanoscale Res Lett, 2013;8(1):397.
PMID: 24059434 DOI: 10.1186/1556-276X-8-397

Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.

Matched MeSH terms: Ferricyanides
Fulltext Structural correlation of some heterocyclic chalcone analogues and evaluation of their antioxidant potential

Kumar CS, Loh WS, Ooi CW, Quah CK, Fun HK

Molecules, 2013 Sep 26;18(10):11996-2011.
PMID: 24077177 DOI: 10.3390/molecules181011996

A series of six novel heterocyclic chalcone analogues 4(a-f) has been synthesized by condensing 2-acetyl-5-chlorothiophene with benzaldehyde derivatives in methanol at room temperature using a catalytic amount of sodium hydroxide. The newly synthesized compounds are characterized by IR, mass spectra, elemental analysis and melting point. Subsequently; the structures of these compounds were determined using single crystal X-ray diffraction. All the synthesized compounds were screened for their antioxidant potential by employing various in vitro models such as DPPH free radical scavenging assay, ABTS radical scavenging assay, ferric reducing antioxidant power and cupric ion reducing antioxidant capacity. Results reflect the structural impact on the antioxidant ability of the compounds. The IC₀ values illustrate the mild to good antioxidant activities of the reported compounds. Among them, 4f with a p-methoxy substituent was found to be more potent as antioxidant agent.

Matched MeSH terms: Ferricyanides/chemistry
Identification of Novel Sesamol Dimers with Unusual Methylenedioxy Ring-Opening Skeleton and Evaluation of Their Antioxidant and Cytotoxic Activities

Murthy S, Hazli UHAM, Kong KW, Mai CW, Leong CO, Rahman NA, et al.

Curr Org Synth, 2019;16(8):1166-1173.
PMID: 31984923 DOI: 10.2174/1570179416666191003095253

BACKGROUND: Sesamol is a widely used antioxidant for the food and pharmaceutical industries. The oxidation products of this compound may be accumulated in foods or ingested. Little is known about its effect on human health.
OBJECTIVE: It is of great interest to identify the oxidation products of sesamol that may be beneficial to humans. This study was undertaken to identify the oxidation products of sesamol and investigate their antioxidant and cytotoxic activities.
MATERIALS AND METHODS: Using the ferricyanide oxidation approach, four oxidation products of sesamol (2, 3, 20 & 21) have been identified. Structural elucidation of these compounds was established on the basis of their detailed NMR spectroscopic analysis, mass spectrometry and x-ray crystallography. Additionally, a formation mechanism of compound 20 was proposed based on high-resolution mass spectrometry-fragmentation method. The antioxidant activities of these compounds were determined by the DPPH, FRAP, and ABTS assays. The in vitro antiproliferative activity of these compounds was evaluated against a panel of human cancer cell lines as well as non-cancerous cells.
RESULTS: Two oxidation products of sesamol were found to contain an unusual methylenedioxy ring-opening skeleton, as evidenced by spectroscopic and x-ray crystallographic data. Among all compounds, 20 displayed impressive antiproliferative activities against a panel of human cancer cell lines yet remained non-toxic to noncancerous cells. The antioxidant activities of compound 20 are significantly weaker than sesamol as determined by the DPPH, FRAP, and ABTS assays.
CONCLUSION: The oxidation products of sesamol could be a valuable source of bioactive molecules. Compound 20 may be used as a potential lead molecule for cancer studies.

Matched MeSH terms: Ferricyanides/chemistry