查看更多>>摘要：As a result of economic development, the pollution of freshwater resources in urban areas of China is becoming more and more serious. Therefore, it is urgent and necessary to develop a real-time monitoring method for the water quality of urban streams and rivers. In this study, a novel method (CFFA) Combined by peak-picking method, Fluorescence spectral indexes, Fluorescence regional integration, and Absorption spectral indexes were designed to extract wide-ranging information from the combination of the excitation-emission matrix (EEM) and absorption spectrum (Abs) of water samples. More than 600 freshwater samples were collected at 180 sections of 60 rivers in the Yangzhou urban region from April 2018 and May 2019. The CFFA inputs form was applied to establish the prediction models of water quality indexes (CODCr, CODMn, NH3-N, TP, TN, and BOD5) based on epsilon-Support Vector Regression (epsilon-SVR). To examine the performance of the prediction models, contrastive analysis among CFFA and the other three input models was carried out. Results show that CFFA input models have shorter modeling time, lower RMSE and MAPE, and higher R-2 in both training and testing sets, and each constituent part of CFFA is important to the precise prediction on the basis of the ablating analysis. Our study highlights that SVR models with the CFFA input trained by numerous and various water samples could effectively predict multiple indexes for real-time water quality monitoring. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this work, a nitrogen-doped carbon dots (CDs) was successfully synthesized by hydrothermal synthesis of polyethylenimine (PEI) and citric acid. The as-prepared CDs suffered from aggregation-caused quenching (ACQ) with a high concentration, but after adding adenosine triphosphate (ATP), the CDs aggregated. The generation of aggregates caused the rotation of the surface groups on CDs and reduced the non-radiation decay. The QY of CDs in water was 9.25 %, and increased to 16.60 % and 63.38% in the addition of 100 and 1000 mu M ATP. And then, the enhancement of the radiation rate led to the aggregation induced enhancement effect (AIEE). Moreover, we also found that the proportion of precursors for CDs synthesis was a key factor in the occurrence of AIEE. Therefore, such CDs would be excellent candidates as fluorescent probes for the label-free detection of ATP. Our proposed method exhibited simple and easy preparation of nanoprobe, quick response (3 min), wide range of linear rage (1-2000 mu M) and eco-friendly. In addition, the method performed successfully as a "turn-on " sensor for detection of ATP in the tablet with a recovery of 100.1 similar to 106.9% and RSD below 3.5%. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Raman spectra and X-ray diffraction patterns of Mg2P2O7 polymorphs (alpha- and beta-phase) were investigated at various temperatures up to 1073 K at ambient pressure. Typical Raman spectra and X-ray diffraction patterns were observed for the reversible phase transition between low-temperature alpha-Mg2P2O7 and high- temperature beta-Mg2P2O7 during heating and cooling. The effect of temperature on the Raman vibrations for the two Mg2P2O7 polymorphs was quantitatively analyzed. All the observed Raman active bands of the two Mg2P2O7 polymorphs showed linear temperature dependence with different slopes. The quantitative temperature dependences of the Raman bands are -4.01 x 10(-2) similar to 1.94 x 10(-2) and -2.31 x 10(-2) similar to -0.44 x 10(-2) cm(-1) K-1 for alpha- and beta-Mg2P2O7, respectively. The force constant evolution of [P2O7](4-) stretching vibrations and the temperature derivatives for both alpha- and beta-Mg2P2O7 were also determined. The thermal expansion coefficient of beta-Mg2P2O7 was estimated at 2.97(8) x 10(-5) K-1. Hence the isobaric mode Gruneisen parameters of beta-Mg2P2O7 were calculated. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：We have synthesized a ri-conjugated acceptor-donor-acceptor-donor (A(2)-D-2-A(1)-D-1) type of unsymmetrical squaraine dye, signified by USQ-1 based on 1-ethyl-2,3,3,8-tetramethyl-2,3-dihydro-1H-pyrrolo[3, 2-h] quinoline moiety to improve the absorption as well as emission spectra to the red-emitting region. The influence of pyridine as a subsidiary electron acceptor unit on various properties in USQ-1 dye was compared with their close relative dye (USQ-2). The synthesized dyes were examined by FT-IR, HR-MS, H-1, and C-13 NMR spectroscopy. This novel unsymmetrical squaraine dye shows a strong absorption with high molar absorptivity (>10(5) L mol(-1) cm(-1)) in the range of 676-661 nm from non-polar to polar solvents. The intramolecular charge transfer (ICT) process from donor to the acceptor moiety in a non-polar to polar solvent has been investigated with the help of oscillator strengths (f), as well as transition dipole moments (mu(eg)). These dyes showed a negative solvatochromic shift from non-polar to polar solvent. The quantitative analysis of charge transfer from the ground to the excited state of these squaraine dyes was calculated by Reichardt's E-T (30) scale plot. The comparative electrochemical, as well as the thermal study of these unsymmetrical squaraines, were studied with the aid of cyclic voltammetry and thermo-gravimetric analysis (TGA), respectively. Additionally,A(2)-D-2-A(1)-D-1 type dye (USQ-1) showed an improved photo-stability compared to D-2-A(1)-D-1 type dye (USQ-2). The computational (theoretical) study of these dyes was supported with the assistance of density functional theory (DFT) together with timedependent density functional theory (TD-DFT). (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：In this paper, the longitudinal plasmon mode optical properties and localized electric field distribution of a single pentagonal gold nanotube are investigated for the first time by the discrete dipole approximation. It is found that pentagonal gold nanotube has stronger electric field distribution compared with circular gold nanotubes when the incident wavelength is located at the plasmon resonance peak. Additionally, we observed that the longitudinal plasmon resonance peak can blue shift nonlinearly with increasing wall thickness, but red shifts linearly with the increase of the length of the pentagonal gold nanotube. The localized electric field analysis reveals that the longitudinal plasmon peak of the pentagonal gold nanotube originates from the dipole resonance mode. The local electric field intensity is controlled by the wall thickness and length. Notably, the effect of wall thickness on the longitudinal plasmon resonance and electric field enhancement can be attributed to the change of the plasmon coupling position and intensity. This work has enriched the theoretical research of pentagonal gold nanotubes and provided ideas for the preparation of high sensitivity nanoprobes biosensors.(C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：To predict drug acute toxicity using the binding information with human serum albumin, our research group established a new method (Carrier protein binding information-toxicity relationship, CPBITR). Unfortunately, the previous model had too few data sets which may affect the accuracy and credibility of the model. In this paper, therefore, we measured the binding modes of three carbamate pesticides, Bendiocarb, Butocarboxim and Dioxacarb with human serum albumin (HSA) to supplement the previously modeled training set. Multispectral methods and molecular docking were used to study their binding modes. We built and optimized the previous models with the combined information of three different toxicity pesticides and HSA in order to find better prediction method. The results showed that Backpropagation Artificial Neural Network model has the best fitting effect among these models. In conclusion, the proposed model effectively improves the accuracy and credibility of the existing model. It results in significant predict drug acute toxicity using the binding information with carrier protein and contribute to drug development and research. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Terahertz (THz) spectra contain chemical information, along with noise and variable backgrounds. Measurement environmental changes and spectral signal differences caused by changes in the sample state can degrade the accuracy of the calibration models. This problem obviously hinders practical applications of THz spectroscopy. To tackle this problem, a three-dimensional spectrum was first self constructed and converted into an intensity image. Zernike moments with inherently invariant properties were then used to describe the THz intensity image and extract the invariant features for further analysis. Considering the reconstruction error and computational cost, the highest order of Zernike moments and the most effective moments were selected and applied to multi-classifiers including support vector machines, naive Bayes, and regularized linear discriminant analysis. Experiments used a THz dataset collected from four chemical substances (melamine, tartaric acid, lactose, and glucose) at five thicknesses (1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm). The results confirmed the effectiveness of the proposed approach. The obtained results show that compare to traditional absorption spectrum features, Zernike moment features are less sensitive to spectral variations caused by changes in sample status. They have better feature representation ability with lower feature vector dimensions. This suggests that they can be integrated into the design of systems for THz spectral classification to increase the robustness and generalization capability of the classifier. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Simple, sensitive and accurate stability indicating spectrophotometric methods have been developed for the simultaneous determination of probenecid, colchicine as well as colchicine degradation product in their ternary mixture. Probenecid was firstly assayed using the double divisor ratio spectra derivative method. On the other hand, three spectrophotometric methods, namely: ratio difference, derivative ratio and mean centering of ratio spectra, have been suggested for the simultaneous quantification of colchicine and its degradation product. The obtained calibration curves were linear at 2.5-30.0 mu g/mL, 0.5-25.0 mu g/mL and 1.0-13.0 mu g/mL for probenecid, colchicine and colchicine degradation product, respectively. The investigated methods were validated in accordance with the International Council for Harmonisation guidelines and were effectively used for quantification of probenecid and colchicine in their bulk powders and combined pharmaceutical dosage form. (C) 2022 Elsevier B.V. All rights reserved.
Taha, Ashraf M.Said, Ragab A. M.Mousa, Ibrahim S.Elsayed, Tarek M....
9页
查看更多>>摘要：Four simple, precise, accurate and validated spectrophotometric methods have been developed for the simultaneous determination of ofloxacin (OFL) and bromfenac sodium (BROM). Firstly, first and second derivative spectrophotometric methods (D-1 & D-2) using a zero-crossing technique utilizing 309.3 and 257.5 nm for OFL and 290.7 and 246.5 nm for BROM as optimum working wavelengths in a binary mixture, respectively. Secondly, the first derivative ratio spectrophotometric method (1DD) in which peak amplitudes at 297.3 nm and 260.7 nm were chosen to simultaneously estimate OFL and BROM, respectively. Thirdly, dual wavelength (DW) method based on two selected wavelengths for each drug in such a way that the difference in absorbance is zero for the second one. At wavelengths 296.4, 348.4 nm BROM has equal absorbance values, therefore, these two wavelengths have been used to determine OFL. Similarly, 271.7 nm and 313.1 nm were selected to determine BROM in the combined formulation. Finally, the fourth method depends on ratio difference spectrophotometry (RDSM), in which the difference between amplitudes at 305.6 nm and 326.5 nm on the ratio spectrum of the mixture was directly proportional to the concentration of OFL; independent of the interfering components. Similarly, the difference between amplitudes at 265.1 nm and 275.4 nm on the ratio spectrum was used for the determination of BROM. The linearity was confirmed in the range of 4 - 18 mg/ml for OFL and BROM for the four methods. The proposed methods were used to determine both drugs in their laboratory prepared mixture and combined formulation with mean percentage recoveries of 99.41 +/- 1.35% for OFL and 99.98 +/- 1.30 % for BROM in method (A). In method (B), the mean percentage recoveries were 101.70 +/- 1.61% for OFL and 101.90 +/- 1.45% for BROM. In method (C) OFL was 99.57 +/- 1.61% and 100.90 +/- 1.62% for BROM. Finally, in method (D) the mean percentage recoveries were 99.37 +/- 1.67% for OFL and 100.70 +/- 1.59% for BROM. The developed methods were successfully employed for determination of OFL and BROM in laboratory prepared mixtures and combined formulation showing satisfactory recoveries. Methods validation was performed according to the International Conference on Harmonization (ICH) guidelines. The obtained results conformed to the accepted ranges of recovery, precision and repeatability. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：We have presented a hydrothermal approach for synthesizing fluorescent silicon nanoparticles (F-SiNPs) with yellow-green emission. The obtained F-SiNPs exhibited excellent stability and good biocompatibility. By virtue of the specific reaction between S2- and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), colorimetric assay of S2- was realized with a good linear range of 0-100 mu M. The colorimetric detection system could be further combined with F-SiNPs to construct a probe for fluorescence turn-off sensing S2- in aqueous solution due to inner filter effect. In the fluorescent detection system, a good linearity with S2- concentration in the range of 0-50 mu M was accomplished. And as low as 0.1 mu M S2- was successfully detected. Moreover, the F-SiNPs displayed low cytotoxicity and good biocompatibility, and was further utilized for cell imaging. These results demonstrated the promising applications of F-SiNPs in S2- analysis and bioimaging. (C) 2022 Elsevier B.V. All rights reserved.
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