查看更多>>摘要：New Raman data are presented concerning H2O and D20 water aggregation in argon matrix having the ratio of number of argon atoms to water molecules close to 40:1. Experiments were conducted at temperatures from 8 K to 34 K allowing observation of OH and OD stretching vibrations of water monomers, dimers, trimers and higher multimers, as well as broad bands corresponding to solid amorphous water. Molecular dynamics simulations were performed for thirteen or sometimes fourteen water molecules dispersed among 500 argon atoms. Resulting final configurations included dimers, trimers, tetramers and pentamers, all in open chain configurations which upon optimization resulted in mostly cyclic conformations. Observed OH stretching vibrations were assigned by comparing calculated normal modes in harmonic approximation at the B3LYP/aug-cc-pVDZ and PBEPBEl/aug-cc-pVDZ level of theory with our data and previously observed bands from infrared matrix isolation studies and Raman jet cooled experiments. Raman bands assigned to water multimers in argon matrix are shifted 20 to 25 cm(-1) towards lower wavenumbers with respect to the positions of OH stretching vibrations of almost free water clusters. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Surface-enhanced Raman Scattering (SERS) has become a powerful analytical technique for highly sensitive detection of target molecules. Its performance, however, is heavily dependent on the substrates. Relatively low sensitivity for small molecules and poor reproducibility in quantitative analysis are often encountered in most of nanoparticle modified SERS substrate. The present work starts by theoretical investigation of the electromagnetic field enhancement by nanomaterials of coinage metals with different sizes. The finite-difference time-domain (FDTD) simulation results revealed that the Ag NPs with the size around 100 nm exhibit the strongest SERS effect and the 'Ag-Ag' gaps have shown higher electromagnetic field enhancement than that of the 'Ag-Ti' gap. Subsequently, a multilayered Ag nanoparticles SERS substrate (or other coinage metals) was prepared by a two-step electroless deposition of Ag on Ti substrate. This was achieved by in situ reduction of Ag precursor to subsequently form a Ag nanoflake (Ag NF) layer and a Ag nanoparticle (Ag NPs) layer on the Ti base (Ti/AgNF/AgNPs). The as-prepared SERS substrate showed a substantially enhanced SERS effect for small molecule detection and detection limit as low as 1.0 x 10(-17) M for picric acid (PA), 1.0 x 10(-14) M for p-nitrotoluene (PNT) and 1.0 x 10(-6) M for uric acid (UA) were obtained respectively. The facile method developed in this work should be widely applicable for in-situ preparation of other SERs substrates. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The inclusion behaviors of estradiol with beta-CD and HP-beta-CD were characterized using molecular dynamics simulation combined with multi-spectroscopic approaches. The findings revealed that estradiol enclosed into the cavity of beta-CD and HP-beta-CD and produced the estradiol-beta-CD and estradiol-HP-beta-CD complexes with the stoichiometry of 1:1. The association constants of the estradiol-beta-CD and estradiol-HP-beta-CD complexes were 3.14 x 10(4) and 3.22 x 10(4) M-1 at 298 K, respectively, which declined with rising temperature. The analysis results of thermodynamic parameters confirmed that the dominate interaction forces were the hydrophobic and hydrogen-bonding interactions for stabilizing the estradiol-beta-CD complex, and were the hydrogen bonding interaction and van der Waals forces for stabilizing the estradiol-HP-beta-CD complex. Moreover, it was confirmed from the results of molecular modeling that estradiol inserted into the hydrophobic cavity of beta-CD and HP-beta-CD and form a stable estradiol-CD complexes. And, it is also observed that the phenyl moiety in estradiol is almost parallel to the central axis of beta-CD and HP-beta-CD, and the phenyl moiety was located on wider rim of beta-CD and HP-beta-CD. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Glioblastoma multiforme (GBM) is one of the most common and aggressive brain tumors. It presents a very bad prognosis with a patients' overall survival of 12-15 months; treatment failure is mainly ascribable to tumor recurrence. The development of new tools, that could help the precise detection of the tumor border, is thus an urgent need. During the last decades, different vibrational spectroscopy techniques have been developed to distinguish cancer tissue from heathy tissue; in the present work, we compared GBM cells deriving from four patients with healthy human astrocytes using Raman spectroscopy. We have shown that the region between 1000 and 1300 cm(-1) is enough informative for this discrimination, indeed highlighting that peaks related to DNA/RNA and cytochrome c are increased in cancer cells. Finally, our model has been able to discriminate cancer cells from healthy cells with an average accuracy of 92.5%. We believe that this study might help to further understand which are the essential Raman peaks exploitable in the detection of cancer cells, with important perspectives under a diagnostic point of view. (C) 2021 The Authors. Published by Elsevier B.V.
查看更多>>摘要：Urgent identification of COVID-19 in infected patients is highly important nowadays. Forster or fluorescence resonance energy transfer (FRET) is a powerful and sensitive method for nanosensing applications, and quantum dots are essential materials in FRET-based nanosensors. The QDs are conjugated to DNA or RNA and used in many applications. Therefore, in the present study, novel fluorescence DNA-conjugated CdTe/ZnS quantum dots nanoprobe designed for detection of Covid-19 after extracting their RNA from saliva of hesitant people. For achieving this purpose, the water-soluble CdTe/ZnS QDs-DNA prepared via replacing the thioglycolic acid (TGA) on the surface of QDs with capture DNA (thiolated DNA) throw a ligand-exchange method. Subsequently, by adding the different concentrations of complementary (target DNA) in a mixture of quencher DNA (BHQ(2) -labeled DNA) and the QDs-DNA conjugates at different conditions, sandwiched hybrids were formed. The results showed that the fluorescence intensity was decreased with increasing the concentration of target DNA (as a positive control). The linear equation and regression (Y = 40.302 X + 1 and R-2 = 0.98) were obtained by using the Stern-Volmer relationship. The Limit of detection (LOD) was determined 0.000823 mu M. The achieved results well confirm the outcomes of the RT-PCR method in real samples. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Direct-contact ultrasonic drying is a novel approach to dehydrate fruits and vegetables to reduce microbial growth and post-harvest loss while preserving nutrients and the quality of the final product. Moisture content is a critical component for food behavior during drying, and its accurate evaluation in real-time is essential for food quality control. This study conveys the potential implementation of portable near-infrared spectroscopy (NIRS) combined with multivariate analysis for real-time assessment of moisture content in apple slices during direct-contact ultrasonic drying. Partial least squares regression (PLSR) and Gaussian process regression (GPR) models were developed, and their performances for different pre-treatments methods and data partitioning algorithms were evaluated with both internal crossvalidation and an external dataset. Three wavelengths were selected by SPA (1359, 1517, and 1594 nm) which were then used to introduce a closed-form equation for moisture content prediction with R-p(2) = 0.99 and RMSEP = 3.32%. The results revealed that portable NIRS combined with multivariate analysis is quite promising for monitoring and evaluating the moisture content during ultrasonic drying. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：This research innovatively combines FT-IR, Raman spectroscopy and their first-derivative spectroscopy to develop a rapid diagnosis method for renal cell carcinoma (RCC). After measuring the Raman spectra and FT-IR spectra of 45 cases of control subjects and 28 cases of RCC, the first derivative of the infrared spectra and the Raman spectra were calculated respectively. Principal component analysis (PCA) was used to extract the features of the infrared spectra, first-derivative infrared spectra, Raman spectra and first-derivative Raman spectra. Then the four feature matrices were merged as fused spectral feature matrices. The fused matrices were used as the input of AlexNet and MCNN. The fused spectral feature matrices were used as the input of AlexNet and MCNN. The adjusted AlexNet model performed better, and the classification accuracy of the fused spectral data is 93%. Compared with the classification results of infrared spectra (74%), Raman spectra (75%) and the fusion of infrared and Raman spectra (79%) combined with the adjusted AlexNet model, the classification result of the fusion of infrared spectra, Raman spectra and their first-derivative was significantly improved. The experimental results show that infrared spectroscopy, Raman spectroscopy and their first-derivative fusion technology combined with deep learning algorithms has great potential in the diagnosis of RCC. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The formation of associates between single- or double-charged anions of bromocresol purple (3,3'-dime thyl-5,5'-dibromophenolsulfonephthalein) and single-charged cations of cyanines (quinaldine blue, quinaldine red) has been investigated. The equilibrium constants of the association have been determined on the basis of UV-Vis spectroscopy data. The energy of the cation-anion interaction (the standard enthalpy of formation of ions and associates), as well as the probable structure of associates, were established using the PM7 semiempirical method. The presented results can be useful in the development of new spectroscopic methods for the detection of organic additives in water (e.g. acetone) due to the spectral properties of dissimilar associates. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Isofuranodiene (IFD) is a sesquiterpene occurring in several plant species, which proved to have multiple anticancer activities. IFD has a lipophilic nature and, hence, a very low water solubility and a poor bioavailability; moreover, it is not stable, undergoing the "Cope rearrangement" to the less active curzerene. The use of appropriate delivery systems can thus be considered as a valid tool to enhance IFD bioavailability, solubility, stability and at the same time also to improve its intracellular uptake and pharmacological activity. Within this frame, monoolein (GMO) nanoparticles loaded with IFD were prepared and their enhanced anticancer activity, compared to pristine IFD, was assessed. In this study, for the first time, an in vitro Fourier Transform Infrared and Raman Microspectroscopy approaches were exploited to evaluate the effects of IFD, alone and loaded in GMO nanoparticles, on MDA-MB 231 breast cancer cell line. The anti-cancer effects of IFD were evidenced by both the spectroscopic techniques and discriminated from the GMO-induced changes in the culture environment; moreover, a synergistic effect of IFD and GMO administration can be envisaged by the experimental results. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The rapid and non-destructive detection of moisture in withering leaves is an unsolved problem because the leaves are stacked together and have random orientation. To address this issue, this study aimed to establish more robust and accurate models. The performance of front side, back side and multi-region models were compared, and the front side model showed the worst transferability. Therefore, five effective wavelength (EW) selection algorithms were combined with a successive projection algorithm (SPA) to select EWs. It was found that the shuffled frog leaping algorithm (SFLA) combined with SPA was the best method for the front side model for moisture analyses. Based on the selected EWs, the extreme learning machine (ELM) became the model with the best self-verification result. Subsequently, moisture distribution maps of withering leaves were successfully generated. Considering the processing demand of withering leaves, local region models developed based on partial least squares and the SFLA-SPA method were applied to predict the moisture of withering leaves in the local and stacked region. The results showed that the RPD, R-cv and R-p values were above 1.6, 0.870 and 0.897, respectively. These results provide a useful reference for the non-destructive detection of moisture in withering leaves. (C) 2021 Elsevier B.V. All rights reserved.
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