查看更多>>摘要：Nerve agents are highly toxic chemical warfare agents that are easy to synthesize and have recently been applied many times in local wars and terrorist attacks. Fluorescent probes have been widely used in life science and medical research due to their features of short reaction time, high sensitivity and good selectivity. Herein, two fluorescent compounds, NMU-1 and NMU-2, were synthesized for the selective detection of nerve agents. NMU-1 exhibited good detection performance for nerve agents. With increasing nerve agent concentration, the fluorescence signal of NMU-1 at 498 nm gradually decreased with an excellent linear relationship. NMU-1 exhibited a low LOD (4.6 mu M for DCP and 8.41 mu M for soman), a rapid response (less than 3 min) and a large Stokes shift (98 nm) along with obvious color changes. Due to its high sensitivity and good selectivity, NMU-1 was successfully applied to image nerve agents in living PC12 cells. Furthermore, NMU-1 was used as a key element to develop chemical warfare agent test paper, which exhibited significant fluorescent changes under hand-held 365-nm UV light upon contact with nerve agents. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A colorimetric and ratiometric fluorescent dual-mode assay is constructed for sensitive and specific Hg2+ sensing based on UiO-66-NH2 and Au composite (UiO-66-NH2@Au). The addition of Hg2+ stimulates the peroxidase-like activity of UiO-66-NH2@Au by the formation of Au-Hg amalgam, promoting the oxidizing of chromogenic substrate OPD to DAP with the aid of H2O2, which lead to the change of colorimetric and fluorescent signals. The absorbance of the sensing system at 450 nm is linear positive correlation with Hg2+ concentration of 30-1400 nM and the color of the solution under visible light shaded from light yellow to dark yellow. With the increase of Hg2+ concentration, the fluorescence signal at 570 nm (DAP) increased whereas that at 455 nm (intrinsic fluorescence of UiO-66-NH2) decreased due to inner filter effect (IFE), the fluorescence intensity ratio (F-455/F-570) decreasing linearly with Log [Hg2+] over the range 60-1700 nM; the fluorescence emission of sensing system under UV excitation changed from blue to yellow, which can easily be discerned visually. This assay was successfully applied to the determination of Hg2+ in tap water and river water. The results indicate that the colorimetric and ratiometric fluorescent dual-mode assay based on UiO-66-NH2@Au realized visual determination of Hg2+ rapidly and reliably, revealed application prospect in Hg2+ monitoring. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Theoretical computations have been performed on the absorption spectra of (8-R-TMB)(2) dimers with varying character of substituents at the 8 position (meso) at monomers units (R = NH2, OH, CH3, H, COH, CF3, CN). The obtained results (TD-CAM-B3LYP) show that the first four lower transitions of studied dimers (S-0 -> S-i, = 1-4) are intrinsically linked with delocalized HOMO and LUMO orbitals of the two monomers, which constitute a dimer. For all the dimers, S-0 -> S-1 and S S-0 -> S-3 transitions are strongly forbidden, whereas S-0 -> S-2 and S-0 -> S-4 are allowed. There is a good agreement between the TD-CAM-B3LYP theory and the simple model of exciton coupling for two identical chromophores with the planes of two moieties, which are stacked upon each other. Intensities of the allowed transitions depend strongly on the nature of the substituent at the meso position. For the dimers with monomer units bearing electron-donor groups, S-0 -> S-2 transitions are more intense compared with S-0 -> S-4 ones. As the donor properties of the meso substituents diminish and electron acceptor properties enlarge, the intensity of these transitions becomes lower, whereas that of S-0 -> S-4 transitions becomes higher. For the dimers with NH2 and CN substituents, the almost inverse ratio of intensities of the transitions discussed is observed (for example, f = 0.80 and 0.06 (in the case of NH2) and f = 0.09 and 0.72 (CN) for S-0 -> S-2 and S-0 -> S-4, respectively). Protonation of the tertiary amine function drastically 'switches off its electron-donating properties. As a result, the red shift of the bands and redistribution of intensities of the allowed S-0 -> S-2 and S-0 -> S-4 transitions is predicted for protonated forms of the (8-NH2-TMB) 2 dimer. This peculiarity can be of especial importance for the design of dimers with a sensor function. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In the presence of thioglycolic acid (TGA) and under the catalysis of Fe3+, a simple, rapid, sensitive, selective and effective ratiometric fluorescence sensor platform based on the mixed physically blue nitrogendoped graphene quantum dots (N-GQDs) as probe signals and orange rhodamine B as internal standard signals has been constructed for analysis of H2O2 in human serum. TGA is the key factor for fluorescence response toward H2O2 by N-GQDs and the mechanism is H2O2 reacts speedily with TGA under the catalysis of Fe3+, and produces intermediate of superoxide anions (O-center dot(2)-), which accepts electrons from N-GQDs, and generates graphene oxide, causing the fluorescence quench of N-GQDs. Compared with N-GQDs probe, the sensitivity of the ratiometric fluorescence sensor platform of N-GQDs/rhodamine B for analysis of H2O2 has been improved by nearly 5-folds. Under the optimum conditions, F-lambda=580nm/F-lambda=440nm has a good linear relationship with the concentration of H2O2 and the detection limit of H2O2 is 0.46 lmol/L with 3.5% RSD. The established sensor platform has been successfully used for probing H2O2 in human serum with satisfactory results. The superior performance of the probe lies in its high selectivity and can be directly employed in detecting H2O2 in serum samples without any sample pretreatment procedures. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Cysteine (Cys), an essential biological amino acid, participates several crucial functions in various physiological and pathological processes. The sensitive and specific detection of Cys is of great significance for understanding its biological function to disease diagnosis. Herein, we designed and synthesized a simple fluorescence sensor 2-(benzothiophen-2-yl)-4-oxo-4H-chromen-3-yl acrylate (BTCA) composed of a flavonol skeleton as the fluorophore and acrylic ester group as the recognition receptor. Probe BTCA displayed high selectivity and extremely fast response toward Cys in phosphate buffer solution in the presence of other competitive species even Homocysteine (Hcy) and Glutathione (GSH) owing to a specific conjugate addition-cyclization reaction between the acrylate moiety and Cys. The photoluminescence mechanism of probe BTCA toward Cys was modulated by excited state intramolecular proton transfer (ESIPT) process. The sensing property for Cys was studied by UV-Visible, fluorescence spectrophotometric analyses and time-dependent density functional theory (TD-DFT) calculations, those results indicated that probe BTCA possessed excellent sensitivity, higher specificity, dramatically "naked-eye" fluorescence enhancement (30-fold), high anti-interference ability, especially immediate response speed (within 40 s). Additionally, the practicability of sensor BTCA in exogenous and endogenous Cys imaging in living cells and zebrafish was elucidated as well, suggesting that it has remarkedly diagnostic significance in physiological and pathological process. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：The Metallacrowns (MCs) composed of repeated [Metal-N-O] subunits are a type of new material, but the MCs have not been developed and utilized in analytical applications. This essay reports on a new kind of terbium(III)-based Metallacrowns (Tb-MCs) with aggregation-induced emission (AIE) feature to build a sensing platform. It is first time that Tb-MCs are able to aggregate to larger aggregates in water along with a bright green emission, so that the property makes it possible to apply in biosensing. Thereafter, the AIE of Tb-MCs can be quenched effectively by Cu2+. Based on the high affinity of thiol to Cu2+, cysteine (Cys) recovers the fluorescence of Tb-MCs in the presence of Cu2+. There is a good linear range varying from 0.02 to 20 mu M with a low limit of detection (LOD) 9.67 nM of Cys. In the end, this novel probe is also successfully applied to the determination of Cys in human serum with satisfactory results. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The deposition of a layer of plasmonic metal on a surface of highly ordered nanostructured oxide is one of the important methods of preparation of substrates for surface-enhanced Raman scattering (SERS) measurements. In this contribution we describe formation of SERS substrates by the deposition of a gold layer on ordered ZrO2 nanotubes. The influence of various experimental parameters on the structure of formed composites and the achievable SERS enhancement factor has been analysed. Like commonly used SERS substrates formed by the deposition of plasmonic metals on TiO2 nanotubes, gold-covered ZrO2 nanotubes also could be used as reversible SERS platform after water rinsing: there is no any significant decrease in the SERS activity of the substrate even after 20 radiation-induced cleaning cycles. Moreover, SERS substrates formed on ZrO2 nanotubes are significantly more stable in strongly acidic media than the previously developed SERS substrates based on ordered TiO2 nanotubes. (C) 2022 Elsevier B.V. All rights reserved.
Nguyen, Linh PhuongLuu, Phuong DucVu, Thai QuocNguyen, Hoa Quynh...
9页
查看更多>>摘要：Potato is one of the most important food crops worldwide in terms of human consumption. However, potato farmers employ a variety of pesticides to protect crops from harmful insects and illnesses, and difenoconazole is a commonly used one that has severe effects on human health and the environment. Therefore, detecting difenoconazole quickly and correctly is critical. In this work, we fabricated AgNPs/cicada wing substrates using natural cicada segments, decorated with silver nanoparticles for surface-enhanced Raman scattering (SERS) measurements to detect trace amounts of difenoconazole in potatoes. Results indicated that a linear relationship with the coefficient of detection (R-2) of 0.987 and the detection limit (LOD) of 0.016 ppm was observed by targeting a distinctive peak at 808 cm(-1) and logarithmic difenoconazole concentrations of 0.1 to 100 ppm. In addition, difenoconazole LODs in potatoes were 63 mu g/kg, lower than those specified by the EU (0.1 mg/kg) and Vietnam (4 mg/kg) utilizing this new technique. Therefore, this proposed SERS method could be used to detect difenoconazole in potatoes at trace levels. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：As one of the most commonly used organic fluorescent dyes, recently rhodamines have been successfully employed in temperature sensing. However, few works have been reported on their temperature-sensitive properties, which inevitably limiting their further applications. In order to solve such problem, we investigated temperature-sensitive properties of rhodamine 110, 123, 19, 6G, B and 3B focusing on their fluorescence emission spectra; and analyzed them in the molecular structure perspective. It is demonstrated that the fluorescence emission intensities of all studied rhodamines decreased with higher temperature, which inevitably enhances the probability of collisions among molecules, thus definitely leads to energy loss in fluorescence emission. While these rhodamines still have various temperature sensitivities mainly due to the substitutes: the substitute on the benzene carboxylate has little effect; the amino substituents of the three-ring xanthene enhance the temperature sensitivity due to their rotation weakening the rigidity of the three-ring xanthene; and the methyl substituents on the three-ring xanthene reduce the temperature sensitivity by enhancing the rigidity and stability of the three-ring xanthene as well as hindering the rotation of ethylamino. These findings can also be extended to other organic fluorescent dyes proved by coumarins comparable to rhodamines. The results provided by this work can be useful reference and guidance to further develop organic fluorescent dyes especially for temperature sensing. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In accordance with the Beer-Lambert law, absorbance is proportional to concentration and optical path length of the absorbers in the sample, and in a linear relationship with total column concentration (product of concentration and optical path length) at a single wavelength. However, limitation of spectral resolution will result in linear deviation with the Beer-Lambert law in actual measurement. Regarding additivity of polychromatic light intensity as the theoretical basis, this paper attributed linear deviation with the Beer-Lambert law to spectral resolution, concentration and light intensity, and verified this explanation by measuring sulfur dioxide at various total column concentrations using spectrometers with different spectral resolutions in the waveband range of 216-230 nm. It was found that linear deviation with the Beer-Lambert law was in negative correlation with spectral resolution, and in positive correlation with total column concentration, and absorbance could be considered to be linear with total column concentration (below 171.4 mg/m(2)) of sulfur dioxide in the wavelength range of 216-230 nm. In addition, it was also proved that linear deviation increases with decreasing light intensity at a fixed sulfur dioxide column concentration. (C) 2022 Elsevier B.V. All rights reserved.
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