Su, GuanwenDang, LepingLiu, GuozhaoFeng, Tingyu...
9页
查看更多>>摘要：The three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrate for trace molecule detection has recently attracted considerable interest; however, these substrates generally either show poor sensitivity or require a complex preparation process. In this work, we have fabricated a 3D ZnO/Ag substrate using porous zeolite imidazole frameworks (ZIF-8) derived ZnO nanoparticles (NPs) followed by evaporation-induced self-assembly of Ag NPs over it, which can detect multiple environmental pollutants by a facile and cost-effective method. This 3D porous substrate showed an ultra-sensitivity for detecting various types of molecules, e.g., rhodamine 6G (R6G), crystal violet (CV), tetracycline, and thiram, simultaneously suggesting its generality. Notably, the lowest detectable concentration (LDC) attained for R6G is 10(-13) M, and the enhancement factor (EF) reaches up to 1.8 x 10(8). The most important reason for ultra-sensitivity is that ZnO derived from ZIF-8 has a hierarchical porous structure and large surface area to provide more "hot spots" and absorb more probe molecules. Consequently, the ZnO/Ag nanostructures show excellent photocatalytic performance. The detected probe molecules could be completely degraded in situ within a short UV exposure time (<30 min), thereby enabling outstanding reusability of this substrate. Finite-different time-domain (FDTD) simulations were used to understand the underlying mechanism of the substrate by calculating electric fields and hot spot distributions. The simulations suggested that the widespread hot spots structures on the substrate are the main reason for its SERS ultra-sensitivity. (C) 2022 Elsevier B.V. All rights reserved.
Novikov, V. S.Kuzmin, V. V.Darvin, M. E.Lademann, J....
10页
查看更多>>摘要：Using the density functional theory (DFT), we calculated the structures and Raman spectra of trans-isomers of alpha-carotene, beta-carotene, gamma-carotene and lycopene as well as trans-isomers of modified beta-carotene and lycopene molecules with substituted end or/and side groups. The DFT calculations showed that the position of the C=C stretching band depends mainly on the number of conjugated C=C bonds and decreases with an increase in the conjugation length. The weak dependence of the position of the C=C stretching band on the structure of the carotenoid side and end groups suggests that this band can be used to evaluate the conjugation length for trans-isomers of various molecules containing polyene chains. The C-C stretching band shifts towards lower wavenumbers with growth of the conjugation length or masses of the end groups and to higher wavenumbers in the presence of the side CH3 groups. The intensities of the C-C and C=C stretching bands are enhanced with growth of the conjugation length or masses of the end groups. The presence of the side CH3 groups results in bending of the carotenoid backbone, splitting and dumping of intensities of the C-C and C=C stretching bands. (C) 2021 Elsevier B.V. All rights reserved.
Ashraf, Muhammad NaeemMajeed, Muhammad IrfanNawaz, HaqIqbal, Muhammad Adnan...
11页
查看更多>>摘要：In this study, Raman spectroscopy is employed to analyze and characterize two salts (N-heterocyclic carbene) and their respective selenium N-heterocyclic carbene compounds. The features observed as differences among Raman spectral data of two different N-heterocyclic carbene salts are called Salt-I and Salt-II and their respective Se compounds, called Compound-I & Compound-II, are used to confirm the formation covalent bond between Se atom carbon atom of carbene. Enhancement in peak intensities and shifting of peak positions is directly related with compound formation. Raman spectral data provide a detail information about bond formation, chemical and structural differences between salts and compounds. The observed Raman spectral features of both salts and compounds are in consistent with computationally calculated Raman spectral features. Raman spectral features of each salt and its respective compound was further analyzed with principal component analysis, which was found helpful for differentiating each salt from its respective compound. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Gypsophila L. taxa growing on gypsum soils have to withstand limiting and restrictive conditions for plant life. This study aims to identify functional mechanisms determine the main functional groups in the vegetative and reproductive organs of some endemic Gypsophila taxa growing in gypsum soils, as well as to understand the relationship between the hidrophobicities and their micromorphological structures of the leaves of these plants grown in arid conditions. In this context, a series of Attenuated Total ReflectionFourier Transform Infrared (ATR-FTIR), water contact angle (CA) measurements, and scanning electron microscopy (SEM) analyses were performed that may help to understand the survival mechanisms of Gypsophila eriocalyx Boiss., Gypsophila germanicopolitana Hub.-Mor. and Gypsophila simonii Hub.-Mor. growing in gypsum habitats. Our results showed the presence of O-H and C-O stretching bands belong to gypsum and calcium oxalate in the roots, stems, leaves and flowers of Gypsophila taxa is thought to be a way of tolerating the excess Ca and sulphate in the extreme habitat where these species grow. Leaves of Gypsophila taxa showed CAs above 90 degrees, which indicates that G. eriocalyx, G. germanicopolitana, and G. simonii were hydrophobic. This study offers new approaches to understanding the adaptation of Gypsophila taxa to the extreme conditions typical of gypsum soils. The characterization of gypsum plants such as Gypsophila taxa, whose mechanisms for competition and survival on gypsum are still not fully understood, is very important in terms of shedding light on the adaptation of endemic plants to gypsum habitats. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Mycotoxins, including zearalenone, are important natural products produced by fungi that occasionally contaminate agricultural commodities and pose serious health risks to consumers of food and feed. Zearalenone and its metabolite, alpha-zearalanol, are of significant concern due to their estrogenic and anabolic steroid activity. Several governments have regulatory standards and advisory guidelines for zearalenone and alpha-zearalanol. Raman and ultraviolet spectroscopy were employed with density functional theory methods to evaluate spectroscopic properties to distinguish between zearalenone and azearalanol systematically. Raman bands were assigned based on vibrational frequency calculations. A portable Raman spectroscopy instrument (785 nm laser) distinguished between zearalenone and alpha-zearalanol in a label-free manner. Many vibrational bands of zearalenone and alpha-zearalanol are similar, including high-intensity peaks at 1315 cm(-1) and 1650 cm(-1). However, the intensities in the Raman spectra at 1465 cm(-1), 1495 cm(-1), and 1620 cm(-1) enabled the identification of zearalenone. The Raman peak at 1450 cm(-1) is associated with alpha-zearalanol. These vibrational bands serve as spectral indicators to differentiate between the structurally similar zearalenone and alpha-zearalanol. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Near-infrared (NIR) emitting BiVO4:Yb3+,Tm3+ nanoparticles are synthesized by a new solvothermal strategy using solvents of oleic acid and methanol. The obtained BiVO4:Yb3+,Tm3+ samples show an average particle size of approximate to 164 nm and exhibit an asymmetry monoclinic crystal structure of BiVO4. At NIR excitation of 980 nm, the BiVO4:Yb3+,Tm3+ sample exhibits a nearly single NIR emission at approximate to 796 nm with extremely weak blue emissions from Tm3+ ions. These high-energy visible emissions are absorbed by the semiconducting host of BiVO4 that possesses a bandgap of approximate to 2.2 eV. Therefore, the NIR excitation to a single intense NIR emission fluorescent BiVO4 materials could be a potential ideal probe for deep-tissue high-resolution bioimaging. To validate the ability of BiVO4 materials for bio-applications, we conduct the cytotoxicity experiments. The results show that the cytotoxicity of HeLa cells is negligible at a concentration of 0.2 mg/ml of BiVO4:Yb3+,Tm3+, and the cell viability approaches 90% at a high dosage of 0.5 mg/ml. The Daphnia magna and Zebrafish treated with nanoparticles (0.5 mg/ml) display bright NIR emission without any background, indicating the excellent in vivo fluorescent imaging capacity of BiVO4:Yb3+,Tm3+ nanoparticles. Our findings offer an environment-friendly strategy to synthesize BiVO4 UCL nanophosphors and provide a promising new class of fluorescent probes for biological applications. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In the determination of chlorophyll with the fluorescence method in the natural water, the suspended particles and colloids will seriously interfere with the incident light and the fluorescence. Based on the analysis of the interaction between light and the measured substances, a high sensitivity, wide range of chlorophyll-a concentration measurement strategy, which combines optical information of fluorescence and absorbance with the CCD integration time transformation method, is proposed. Correspondingly, a novel algorithm, which can significantly correct the attenuation of incident light due to the absorption of suspended particles and the deviation of detected fluorescence caused by the scattered light and reflected light, is proposed to realize turbidity compensation. For verification, a self-designed compact optical experimental device consisting of a single LED and a linear CCD was set up to obtain the fluorescence spectrum and absorbance spectrum simultaneously. The experimental results demonstrate that the compensation strategy can commendably compensate for the impact of the suspended particles. The relative error of chlorophyll-a measurement is less than 5%, even in a high turbidity environment. Furthermore, the minimum detection limit is significantly reduced from conventional 0.01 mu g/L, to 0.0025 mu g/L, in the range of 0.0025-130 mu g/L, with the CCD integration time transformation method, which improves the measurement sensitivity. This device and method have the potential to be applied to the in situ online measurement of chlorophyll-a concentration in natural water. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：As an essential factor in quality assessment of maize seeds, variety purity profoundly impacts final yield and farmers' economic benefits. In this study, a novel method based on Raman hyperspectral imaging system was applied to achieve variety classification of coated maize seeds. A total of 760 maize seeds including 4 different varieties were evaluated. Raman spectral data of 400-1800 cm(-1) were extracted and preprocessed. Variable selection methods involved were modified competitive adaptive reweighted sampling (MCARS), successive projections algorithm (SPA), and their combination. In addition, MCARS was proposed for the first time in this paper as a stable search technology. The performance of support vector machine (SVM) models optimized by genetic algorithm (GA) was analyzed and compared with models based on random forest (RF) and back-propagation neural network (BPNN). Same models based on Vis-NIR spectral data were also established for comparison. Results showed that the MCARS-GA-SVM model based on Raman spectral data obtained the best performance with calibration accuracy of 99.29% and prediction accuracy of 100%, which were stable and easily replicated. In addition, the accuracy on the independent validation set was 96.88%, which proved that the model can be applied in practice. A more simplified MCARS-SPA-GA-SVM model, which contained only 3 variables, had more than 95% accuracy on each data set. This procedure can help to develop a real-time detection system to classify coated seed varieties with high accuracy, which is of great significance for assessing variety purity and increasing crop yield. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A quinoline-based small molecular probe, H2L was designed, synthesized and characterized by different spectroscopic methods. It was utilized as a multi-responsive probe for the detection of Fe3+, Al3+, Cu2+ and PPi. It showed very selective instant turn-on fluorimetric response towards Fe(3+ )and Al3+ with a detection limit in nanomolar range. Solutions of H2L containing Fe3+ or Al3+ could sequentially sense PPi by a turnoff mechanism. Also, H2L could determine the presence of Cu' very selectively among a series of other metal ions by a sharp change in colour. Detection of Cu2+ through colorimetry was further investigated by systematic UV-Vis studies and the potential of H2L to act as a potential colorimetric sensor for Cu2+ was suitably established. Filter-paper strip experiments were conducted to demonstrate the practical utility of the proposed sensor. Potential applications of H2L as a sensor for pH in the acidic range has also been explored. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Dextran sulfate sodium (DSS) is a heparin polysaccharide, whose overuse would cause many adverse effects, such as stiff and painful joints and loss of hair. It is crucial to search after a rapid and accurate approach for the determination of DSS in the clinical treatment and diagnosis. Regrettably, there are few literatures about analytical methods for detecting DSS at present. In this research, a sensitive and selective method for detecting DSS based on the hydrosoluble perylene diimide (PDI) derivative was established in pure aqueous solution. The sensing mechanism and performance of PDI-PdEC were systematically investigated by ultraviolet and fluorescence spectroscopy. Non-covalent interactions between DSS and PDI-PdEC, like p-p stacking, electrostatic and hydrophobic interaction, promote the aggregation of PDI-PdEC and form supramolecular aggregates, which realize the sensitive and rapid detection of DSS in aqueous system. The detection limit for DSS is as low as 5.51 ng/mL and the linear range is 20-500 ng/mL. Furthermore, this probe was triumphantly applied in the detecting of DSS in serum. To the best of our knowledge, this is the first fluorescent probe for detecting DSS in aqueous media. We consider that our study will not only broaden the range of applications of perylene diimide fluorescent sensors, but also provide valuable reference for the design of new sensors for the rapid determination method of DSS. (C) 2021 Elsevier B.V. All rights reserved.
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