Research Articles

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Browsing Research Articles by Author "Chen, M."

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    A nanosystem composed of upconversion nanoparticles and N, N-diethyl-p-phenylenediamine for fluorimetric determination of ferric ion.
    (Microchimica Acta, 2018) Chen, M.; Kutsanedzie, F. Y.; Cheng, W.; Agyekum, A. A.; Li, H.; Chen, Q
    A system composed of upconversion nanoparticles (UCNPs) and N,N-diethyl-p-phenylenediamine (EPA) is shown to be a useful probe for highly sensitive and selective fluorometric determination of ferric ion. The fluorescence of the UCNPs (under the 980 nm excitation) has peaks at 546, 657, 758 and 812 nm. EPA is readily oxidized by Fe(III) to generate a dye with a peak at 552 nm. This causes an inner filter effect on the fluorescence peaks at 546 nm, whereas the emissions at 657, 758 and 812 nm remained unchanged. Therefore, the iron concentration can be quantified by measurement of the ratio of fluorescence at 546 and 758. Under optimal condition, the ratio drops linearly in the 0.25 to 50 μM. Fe(III) concentration ranges, with a detection limit of 0.25 μM. The method is highly selective and was applied to the analysis of spiked samples (wastewater) where it gave recoveries of between 100.9 and 107.3%; and RSD values between 0.8 and 1.4%. Results are approximately the same as those obtained by AAS. Graphical abstract A method is presented for fluorimetric determination of Fe(III). Fe(III) reacts with N,N-diethyl-p-phenylenediamine (EPA) to generate EPA oxide. The fluorescence peaking at 546 nm is reduced in presence of oxidized EPA via an inner filter.
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    Ratiometric fluorescence detection of Cd2+ and Pb2+ by inner filter-based upconversion nanoparticle-dithizone nanosystem.
    (Microchemical Journal, 2019) Chen, M.; Kutsanedzie, F. Y.; Cheng, W.; Li, H.; Chen, Q.
    This paper reports a fluorescence sensor based on inner filter effect (IFE) between upconversion nanoparticles (UCNPs) and dithizone for the highly selective and sensitive detection of cadmium ion (Cd2+) and lead ion (Pb2+) in black tea. The fluorescence at 546 nm, 657 nm, 758 nm and 812 nm were obtained and applied as signal indicator upon upconversion nanoparticles excitation at the single wavelength of 980 nm. With the formation of UCNPs-dithizone mixed system pH at 8, the dithizone-Cd2+ complex increases with increasing in concentration of Cd2+, which cause the bathochromic shifting in absorption bands and an upconversion fluorescence (UCF) quenching at 546 nm; at pH 6, the absorption band of dithizone shows a blue shift with addition of Pb2+, leading an upconversion fluorescence recovering at 657 nm. However, in the presence/absence of Cd2+/Pb2+, the fluorescence at 758 nm and 812 nm were not influenced. This implies the Cd2+ and Pb2+ concentration could be monitored based on the fluorescence ratio I546/I758 and I657/I758 respectively. Under optimal condition, the fluorescence show a good linear within the ranges of 0.01 μM–1.0 μM for Cd2+; and 0.025 μM–1.0 μM for Pb2+, with a detection limit of 3.7 and 8.4 nM achieved. The method was applied for Cd2+ and Pb2+ in real sample (black tea and tap water) with recoveries of 99.6% to 108% and RSD value in the range of 0.96 to 1.23 for Cd2+, with recoveries of 96% to 103.2% and RSD value in the range of 0.98 to 1.27 for Pb2+.