Yushina, I. D.Krylov, A. S.Rakitin, O. A.Bartashevich, E., V...
4页
查看更多>>摘要：The insight into the behavior of polyiodides under non-ambient conditions can enrich the practical applications due to obtaining materials with adjustable and tunable conducting properties. In this work Raman spectroscopy study in the range 0 - 6.5 GPa has been performed for dithiazolylidenedithiazolium zigzag polyiodide with N-H center dot center dot center dot N hydrogen bond. Variations of band positions in the lowwavenumber region of Raman spectra have been attributed to the changes in the anionic part of the unit cell. The association of different interacting polyiodide subunits at pressure above 1.5 GPa leads to the emergence of the bands at 98 and 115 cm(-1) due to consistent vibrations in the I(8)(2-)zigzag. The emergence of the band at 159 cm(-1) above 0.28 GPa can be assigned to N-H center dot center dot center dot N hydrogen bond vibration. The obtained results depict undergoing structure transformations: the stronger are cation.. .cation and anion.. .anion interactions the more likely is the observation of conducting properties due to the formation of polyiodide zigzag and strongly-bound hydrogen-bonded fragment. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Effects of magnesium (Mg2+) ions on the stability and structural properties of double-stranded DNA are vitally important for DNA folding and functional behavior. Complementing our previous study on highly hydrated thin films of DNA with sodium counterions, with no buffer (pH approximate to 6) and surrounded with Mg2+ cations, here we use Fourier transform infrared spectroscopy and band shape analysis to explore in detail the vibrational signatures of DNA-magnesium interaction in the case when DNA charges are neutralized solely by Mg2+ cations, hereafter called MgDNA. Ion atmosphere has been controlled by the magnesium to phosphate molar concentration ratio r which varied between 0.0067 and 10. For r = 0 we find that spectral features in the base region remain similar as in DNA, whereas changes in the backbone region indicate that the B conformation becomes fully stabilized. With increasing r a pronounced structural reshaping occurs in the phosphate backbone region indicating a blue shift of the asymmetric band, while the symmetric band does not show any displacement in frequency. The band shape analysis of overlapping peaks in the respective phosphate regions demonstrates that the number of constituent modes as well as their positions in frequency do not change, whereas their intensities and bandwidths display disparate changes. The results reflect a variety of local environments at the DNA backbone due to a heterogeneous ion atmosphere with randomly distributed magnesium ions and local patterns of hydrogen bonds which change with increasing r. Remarkably, after crowded r = 10 ion atmosphere is depleted, Mg induced spectral changes vanish and structural features of MgDNA (r approximate to 0) are fully restored. Overall results strongly suggest that in MgDNA on highly hydrated thin films the hydrogen-base pairing remains preserved and that Mg2+ ions, similar to sodium ions, retain their mobility and interact with double helix via water-mediated electrostatic forces. (C) 2021 The Authors. Published by Elsevier B.V.
查看更多>>摘要：Silver ion pollution is a great threat to global environment and public healthcare today. Thus, quick, portable and sensitive assays for Ag+ tracing are highly needed. Herein, a reliable fluorescent and colorimetric dual-channel assay has been constructed for Ag+ detection by utilizing a terbium-based fluorescent nanomaterial (named as Tb-DPA) and a Pt/Pd nanoflower (Pt/Pd NF)-triggered reaction between N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt (TOPS) and 4-amino-antipyrine (4-AAP). Initially, in the sensing system containing 4-AAP, TOPS, Tb-DPA and Pt/Pd NF, TOPS and 4-AAP is catalyzed by Pt/Pd NF to produce a purple compound (called as PC1), which endows a broad UV absorption that can fully cover the emission band of Tb-DPA. Thus, the system exhibits a high UV absorption (originating from PC1) and a low fluorescence intensity (originating from Tb-DPA) which has been quenched by PC1 through a filtering effect. However, when the system meets Ag+, the oxidase-like activity of Pt/Pd NF will be inhibited, leading less amount of PC1. As a result, the system exhibits a decreased UV absorption and a recovered fluorescence intensity, both of which can be used for Ag+ detection, reporting low detection limits of 3.63 nM and 1.63 nM, respectively. Specially, results from the dual-channel assay can mutually validate each other, improving the detection reliability. Moreover, this dual-mode assay shows good capability toward Ag+ detection in real samples, illustrating the potential for practical applications. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Herein, we established a fluorescent detection platform for baicalein (Bai) based on copper nanoclusters, which were prepared by using copper sulfate as the precursor, trypsin (Tryp) as the template and hydrazine hydrate as the reducing agent. The entire preparation and testing process were rapid, facile and green. Many characterization methods, such as UV-vis absorption spectroscopy, fluorescence spectroscopy, fourier transform infrared spectroscopy (FT-IR), fluorescence lifetime, transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS), were applied for the analysis of trypsin-templated copper nanoclusters (Cu NCs@Tryp). The Cu NCs@Tryp released green fluorescence at maximum emission wavelength of 457 nm under maximum excitation wavelength of 377 nm. More importantly, the fluorescence of Cu NCs@Tryp was efficiently quenched by Bai. According to this phenomenon, a facile, rapid and selective turn-off fluorescence probe for Bai sensing was developed. Under the optimized testing conditions, the In(F-0/F) value and concentration of Bai displayed excellent linear relationship changing from 0.5 to 60 mu M (R-2 = 0.9969), and the detection limit was 0.078 mu M. Furthermore, the Cu NCs@Tryp has been successfully employed to measure the amount of Bai in bovine serum samples with satisfactory recoveries. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Feature selection plays a vital role in the quantitative analysis of high-dimensional data to reduce dimensionality. Recently, the variable selection method based on mutual information (MI) has attracted more and more attention in the field of feature selection, where the relevance between the candidate variable and the response is maximized and the redundancy of the selected variables is minimized. However, multicollinearity often is a serious problem in linear models. Collinearity can cause unstable parameter estimation, unreliable models, and weak predictive ability. In order to address this problem, the variance inflation factor (VIF) was introduced for feature selection. Therefore, a variable selection method based on MI combined with VIF was proposed in this paper, called Mutual Information-Variance Inflation Factor (MI-VIF). By calculating the MI between the independent variable and the response variable, the variable with greater MI was selected to maximize the correlation between the independent variable and the response variable. By calculating the VIF between the independent variables, the multicollinearity test was performed. The variables that cause the multicollinearity of the model were eliminated to minimize the collinearity between the independent variables. The proposed method was tested based on two high-dimensional spectral datasets. The regression models (PLSR, MLR) were established based on feature selection through MI-VIF and MI-based methods (MIFS, MMIFS) to compare the prediction accuracy of the models. The results showed that under two datasets, the MI-VIF showed a good prediction performance. Based on the tea dataset, the established MI-VIF-MLR model achieved accuracy with Rp(2) of 0.8612 and RMSEP of 0.4096, the MI-VIF-PLSR model achieved accuracy with Rp(2) of 0.8614 and RMSEP of 0.4092. Based on the diesel fuels dataset, the established MI-VIF-MLR model achieved accuracy with Rp(2) of 0.9707 and RMSEP of 0.6568, the MI-VIF-PLSR model achieved accuracy with Rp(2) of 0.9431 and RMSEP of 0.9675. In addition, the MI-VIF was compared with the Successive projections algorithm (SPA), which is a method to reduce the collinearity between variables in the wavelength selection of the near-infrared spectrum. It was found that MI-VIF also had a good predictive effect compared to SPA. It proves that the MI-VIF is an effective variable selection method. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：A series of WO3-x thin films with defects were obtained by thermal treatments from laser irradiation and annealing, respectively. The corresponding tunability of localized surface plasmon resonance properties and the enhancement of Raman scattering intensity were realized due to the defects in the WO3-x thin films after thermal treatments. With the changes of either laser power or annealing temperature, the crystalline quality of WO3-x thin film was declined with a red shift of the surface plasmon resonance wavelength from 464 nm to 482 nm. The as-treated WO3-x film shows good uniformity and reproducibility in Surface-enhanced Raman spectroscopy measurement, the detection limit for dye methylene blue can reach 10(-8) mol/L, and enhancement factor is 1.38 x 10(6). Furthermore, the simulation result of finite-difference time-domain showed a substantial agreement with experimental results. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Herein bulk phenyl- and carbon-modified graphitic carbon nitride (PCCN) powders with tunable fluorescent emission from green-color to yellow-color were prepared by copolymerization of 2,4-diamino-6-phe nyl-1,3,5-triazine and 2,2,6-triaminopyrimidine. The corresponding nanosheets with blue-color to green-color fluorescence were obtained by the oxidation of their bulk powders in sulfuric or nitric acid and then ultrasonic exfoliation. The typical PCCN0.6 nanosheets not only displayed strong green-color fluorescence but also exhibited photocatalytic oxidase-like activity, which can catalyze the oxidation of substrates 3,3',5,5'-tetramethylbenzidine and Amplex UltraRed by O-2 to produce blue-color colorimetric product and pink-color fluorescent product, respectively. By taking advantage of green-color fluorescence and photocatalytic activity of PCCN0.6 nanosheets, a prototype for high-level anti-counterfeiting application was demonstrated by using the mixture of PCCN0.6 nanosheets and Amplex UltraRed as the fluorescent ink. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Ring-opening reaction of rhodamine spirolactam has been widely applied to construct fluorescent probes. The fluorescence properties of the probe were finely tuned for specific purpose through changing the rhodamine fluorophore. However, the influence on response range and kinetic parameters of the probe during the change has been seldom discussed. Herein, we took pH detection as an example and constructed spirolactam based probes (RLH A-C) with Rhodamine 6G, Rhodamine B and Rhodamine 101. The pK(a) values and observed rate constant k(obs) of RLH A-C were determined and found to negatively correlated with the calculated Gibbs free energy differences Delta G(C-O) and Delta G(TS) respectively. The potential applications of RLH A-C in imaging acidic microenvironment were also investigated in cells. We expect the comparison of rhodamine fluorophores will facilitate the quantitative optimization of rhodamine spirolactam based fluorescent probes. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A simple and feasible strategy was developed for the preparation of fluorescent covalent organic frameworks (COFs) TpPa-1@FL. The TpPa-1-1@FL was prepared via a self-assembly strategy by soaking non-fluorescent COFs TpPa-1 into strong fluorescent fluorescein (FL) solution. A chemiluminescence resonance energy transfer (CRET) system was constructed by the combination strong fluorescent TpPa-1@FL with TCPO-hydrogen peroxide (H2O2) reaction. The chemiluminescence (CL) signal of the system was further improved by the addition of bovine serum albumin (BSA). The CRET system can determine H2O2 with a linear range response from 5.0 mmol/L to 20.0 mmol/L and a detection limit of 1.1 mmol/L. The CRET system was further exploited for indirect detection of uric acid with coupling of uricase. A good linear relationship was obtained for uric acid in the 10.0-400.0 mmol/L concentration range with a detection limit of 3.8 mmol/L. The practicability of this method was assessed by the determination of uric acid in real samples of human serum and urine. (C) 2021 Elsevier B.V. All rights reserved.
Zapata, FelixOrtega-Ojeda, Fernando E.Garcia-Ruiz, Carmen
10页
查看更多>>摘要：Vibrational spectroscopic techniques have shown to be highly suitable for the identification and comparison of textile fibres and clothing fabrics. On the other hand, new chemical imaging modes based on these spectroscopic techniques are becoming useful in multiple fields. This is particularly important to, for instance, chemically visualize and screen different samples including forensic evidence (crime scene investigation), chemical and food products (quality control), biological tissues and living beings (medical imaging), among others. This study explores the forensic examination and selective chemical visualization of textile fibres and clothing fabrics using Raman imaging. Four experiments were performed, which were focused on the screening of (i) white different materials made of 100 % cotton (gauze, cotton wool, t-shirt, and swab), (ii) polyester and cotton fabrics evidence of the same colour, (iii) five different coloured cotton fabrics, and (iv) textile fibres of different materials (acrylic, cotton, nylon, polyester, and silk). Several methods of multivariate chemometric analysis including principal component analysis (PCA), multivariate analysis of variance (MANOVA), and multivariate curve resolution (MCR) were applied to enhance the limited visual comparison of the spectra accomplished with the unaided eye. The results evidenced the suitability of Raman imaging to statistically discriminate textile fibres and fabrics due to the chemical composition of both the clothing material and the dyestuff. (C) 2021 The Author(s). Published by Elsevier B.V.
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