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  • 1
    In: Materials, MDPI AG, Vol. 13, No. 21 ( 2020-10-31), p. 4894-
    Abstract: Less toxic, environmentally safe green-mediated iron (III) oxide nanoparticles (Fe3O4-NP) synthesized using Callistemon viminalis (C. viminalis) leaf (Fe3O4-NPL) and flower (Fe3O4-NPF) extracts is reported in this work for the first time. Total flavonoids and phenols present in the plant extracts were determined. Characterization of the nanoparticles was carried out using Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible spectroscopy (UV–VIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Malvern zeta sizer. Other properties of the nanoparticles were investigated using the thermogravimetric analyser and cyclic voltammetry. The average particle sizes obtained for Fe3O4-NPL and Fe3O4-NPF were 17.91 nm and 27.93 nm, respectively. Fe3O4-NPL exhibited an excellent electrochemical activity when compared with Fe3O4-NPF based on a stability study using cyclic voltammetry and regression value. Additionally, Fe3O4-NPF displayed excellent antimicrobial activity against Bacillus cereus, Salmonella enteritidis, and Vibrio cholerae with zones of inhibition of 13, 15, and 25 mm, respectively. Simple, cheap, and less toxic green-mediated iron (III) oxide nanoparticles synthesized from C. viminalis leaf (Fe3O4-NPL) and flower (Fe3O4-NPF) extracts hold the potential of being used to control the activity of pathogenic bacteria of health importance and as an electrochemical sensor for both biological and environmental analytes.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2487261-1
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  • 2
    Online Resource
    Online Resource
    MDPI AG ; 2021
    In:  Molecules Vol. 26, No. 21 ( 2021-10-28), p. 6512-
    In: Molecules, MDPI AG, Vol. 26, No. 21 ( 2021-10-28), p. 6512-
    Abstract: Choline is an officially established essential nutrient and precursor of the neurotransmitter acetylcholine. It is employed as a cholinergic activity marker in the early diagnosis of brain disorders such as Alzheimer’s and Parkinson’s disease. Low levels of choline in diets and biological fluids, such as blood plasma, urine, cerebrospinal and amniotic fluid, could be an indication of neurological disorder, fatty liver disease, neural tube defects and hemorrhagic kidney necrosis. Meanwhile, it is known that choline metabolism involves oxidation, which frees its methyl groups for entrance into single-C metabolism occurring in three phases: choline oxidase, betaine synthesis and transfer of methyl groups to homocysteine. Electrocatalytic detection of choline is of physiological and pathological significance because choline is involved in the physiological processes in the mammalian central and peripheral nervous systems and thus requires a more reliable assay for its determination in biological, food and pharmaceutical samples. Despite the use of several methods for choline determination, the superior sensitivity, high selectivity and fast analysis response time of bioanalytical-based sensors invariably have a comparative advantage over conventional analytical techniques. This review focuses on the electrocatalytic activity of nanomaterials, specifically carbon nanotubes (CNTs), CNT nanocomposites and metal/metal oxide-modified electrodes, towards choline detection using electrochemical sensors (enzyme and non-enzyme based), and various electrochemical techniques. From the survey, the electrochemical performance of the choline sensors investigated, in terms of sensitivity, selectivity and stability, is ascribed to the presence of these nanomaterials.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2008644-1
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  • 3
    Online Resource
    Online Resource
    MDPI AG ; 2021
    In:  Molecules Vol. 26, No. 17 ( 2021-09-03), p. 5357-
    In: Molecules, MDPI AG, Vol. 26, No. 17 ( 2021-09-03), p. 5357-
    Abstract: Reported here is the design of an electrochemical sensor for dopamine (DA) based on a screen print carbon electrode modified with a sulphonated polyether ether ketone-iron (III) oxide composite (SPCE-Fe3O4/SPEEK). L. serica leaf extract was used in the synthesis of iron (III) oxide nanoparticles (Fe3O4NPs). Successful synthesis of Fe3O4NP was confirmed through characterization using Fourier transform infrared (FTIR), ultraviolet–visible light (UV–VIS), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). Cyclic voltammetry (CV) was used to investigate the electrochemical behaviour of Fe3O4/SPEEK in 0.1 M of phosphate buffer solution (PBS) containing 5 mM of potassium ferricyanide (III) solution (K3[Fe(CN)6]). An increase in peak current was observed at the nanocomposite modified electrode SPCE-Fe3O4/SPEEK) but not SPCE and SPCE-Fe3O4, which could be ascribed to the presence of SPEEK. CV and square wave voltammetry (SWV) were employed in the electroxidation of dopamine (0.1 mM DA). The detection limit (LoD) of 7.1 μM and 0.005 μA/μM sensitivity was obtained for DA at the SPCE-Fe3O4/SPEEK electrode with concentrations ranging from 5–50 μM. LOD competes well with other electrodes reported in the literature. The developed sensor demonstrated good practical applicability for DA in a DA injection with good resultant recovery percentages and RSDs values.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2008644-1
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  • 4
    Online Resource
    Online Resource
    IOP Publishing ; 2021
    In:  Materials Research Express Vol. 8, No. 5 ( 2021-05-01), p. 055403-
    In: Materials Research Express, IOP Publishing, Vol. 8, No. 5 ( 2021-05-01), p. 055403-
    Abstract: Choline is employed as cholinergic activity marker in brain tissue in the field of clinical detection of diseases. Although, chromatographic methods and biosensors are the most commonly used techniques for choline detection, there is also an interest in exploring the efficacy of a cost effective non-enzyme based sensor for choline detection. Here, electrochemical sensors based on green synthesized metal oxides (iron (III) oxide nanoparticles) from Callistemon viminalis leaves and flowers extract (Fe 3 O 4 NPL and Fe 3 O 4 NPF) in combination of functionalized multi-walled carbon nanotube (f-MWCNT) supported on glassy carbon electrodes (GCE/f-MWCNT/Fe 3 O 4 NPL and GCE/f-MWCNT/Fe 3 O 4 NPF) were fabricated for choline detection. Morphological, structural and optical analysis of the nanocomposites were studied using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and ultra violet-visible (UV–vis) spectroscopy accordingly. In contrast, electron transport properties on bare glassy carbon electrode (GCE) and nanocomposite modified electrodes (GCE/f-MWCNT/Fe 3 O 4 NPL and GCE/f-MWCNT/Fe 3 O 4 NPF) was examined through electrochemical characterization using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical oxidation of choline was also studied through CV, EIS, square wave voltammetry (SWV) and chronoamperometry (CA). The result proved that f-MWCNT enhanced the reactivity of Fe 3 O 4 NP towards choline oxidation with voltammetric limit of detection (0.83 and 0.36 μ M) for choline at GCE/f-MWCNT/Fe 3 O 4 NPL and GCE/f-MWCNT/Fe 3 O 4 NPF electrodes respectively. Designed sensors proved selective, reproducible, stable and applicable for real sample sensing in choline dietary supplements.
    Type of Medium: Online Resource
    ISSN: 2053-1591
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 2760382-9
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  • 5
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2022
    In:  Journal of Cluster Science Vol. 33, No. 3 ( 2022-05), p. 1035-1043
    In: Journal of Cluster Science, Springer Science and Business Media LLC, Vol. 33, No. 3 ( 2022-05), p. 1035-1043
    Type of Medium: Online Resource
    ISSN: 1040-7278 , 1572-8862
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2016762-3
    SSG: 11
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