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•Hydrophobicity of Bmim2CuCl4 was reported.•Hygroscopic process of Bmim2CuCl4 was monitored in situ by time-dependent IR.•Hydrogen bond in Bmim2CuCl4 was analyzed by IR bands position ...shift.•Water molecules aggregation states in Bmim2CuCl4 was discussed.
By dissolving copper chloride in BmimCl (1-butyl-3-methylimidazolium chloride), chloride ions can coordinate with copper ions and form CuCl42−, thereby inducing the solution being hydrophobic. In the present work, hydrogen bonds between Bmim+ and anions are analyzed and discussed by two-dimensional correlation spectroscopy. Time-dependent attenuated total reflection spectroscopy (ATR-FTIR) is introduced to monitor the hygroscopic process of Bmim2CuCl4 and BmimCl in situ. Hygroscopic capacity and rate of Bmim2CuCl4 shrink compared with BmimCl. The change of water molecular clusters has been studied by second-derivative spectra in the hygroscopic process. The behaviors of water molecular in the two ionic liquids are also distinctive.
It is difficult to distinguish the Pterocarpus santalinus in the furniture wood market, since it is similar to other tree species such as Dalbergia louuelii and Pterocarpus tinctorius. Moreover, the ...features of the wood are usually covered with the beeswax on the surface, making it even harder to be identified the tree species. Extractive is important components of wood and plays a significant role in the color of wood. Benzene-alcohol extractives contain specific chemical components of wood, which is an important part to distinguish tree species. Color parameters show that the color is obviously deepened when the sample is covered with beeswax. As shown in the SEM examination, beeswax appears on the wood surface in a large area and is immersed in the vessels of wood. In this paper, with the infrared spectrum three-step identification, the differences of the chemical composition of benzene-alcohol extractive are analyzed to distinguish tree species. The results show that the functional groups of the compounds contained in beeswax are mainly composed of long-chain methyl -CH3, methylene –CH2- and ester carbonyl CO, carboxyl C–O stretching at 2956, 2917, 2850, 1740, 1468, 1378 and 721cm-1. The absorption peaks of beeswax are so strong that they weaken the peaks of benzene-alcohol extractives from three tree species. In the FT-IR and SD-IR spectra, P. santalinus and P. tinctorius have strong peaks at 1736 cm−1, 1590 cm−1, 1151 cm−1 (1149 cm−1), 1067 cm−1 (1064 cm−1), 1033 cm−1, 958 cm−1 (959 cm−1), and 835 cm-1 (833 cm-1), while D. louvelii has a weak broad peak at 1630 cm-1 and 1602 cm-1, and there is no absorption peak at other wave numbers. At 754 cm-1 and 700 cm-1, no absorption peaks are found in the other two tree species. In the Synchronous 2DCOS-IR spectra in the ranges of 900–1200cm-1,1200-1425 cm-1, and 1480-1700cm-1, the sensitivity of some functional groups in P. santalinus and D. louvelii for the temperature perturbation tends to be the same. The main difference between them is that more functional groups of P. santalinus are sensitive to temperature disturbance. For P. tinctorius, it is sensitive to temperature perturbation, in which, the ester groups C–O stretching vibration at 1151, 1168, 1202 cm-1 and aromatic ring skeleton stretching belongs to flavonoids and lignin at 1511 and 1594 cm-1. The above results indicate that the three-step identification by the infrared spectroscopy can accurately and quickly distinguish tree species.
•In this manuscript, based on Pterocarpus santalinus as the starting point, two confusing species were selected as the research object (Dalbergia louuelii and Pterocarpus tinctorius). In order to achieve accurate discrimination of three kinds of hardwood between blank and covered with beeswax, chromaticity test were used to determinate color differences; SEM were used to determinate microstructure; FTIR, SD-IR and 2DCOS-IR were used to discriminate the chemical characteristics.•When the wood surfaces of three tree species were covered with beeswax, the visual differences were small in color parameters. The SEM micro-topography showed that the beeswax appeared on the wood surface in a large area and was immersed in the vessels of wood.•The functional groups of the compounds contained in beeswax were mainly composed of long-chain methyl -CH3, methylene –CH2- and ester carbonyl CO, carboxyl C–O stretching at 2956, 2917, 2850, 1740, 1468, 1378 and 721cm-1. These absorption peaks were identical simultaneously in the spectrum of three tree species. Meanwhile, the characteristic peak intensity of them was significantly reduced, which increased the difficulty of differentiation, but the three species can still be distinguished at the characteristic peaks with strong intensity.
•Dynamic interaction mechanism of A. flavus-maize was explored by SWIR-HSI and SR-FTIR.•Spatio-temporal pattern of infected maize with incremental damage for 0–96 h was studied.•Feature extraction ...and quantitative prediction of AFB1 were achieved by SWIR-HSI.•SR-FTIR with 2DCOS reveals nutrient loss and AFB1 biosynthesis in micron-level.•Macro- and micro-scopic chemical imaging techniques verified the dynamic process.
The dynamics mechanisms regulating the growth and AFB1 production of Aspergillus flavus during its interactions with maize kernels remain unclear. In this study, shortwave infrared hyperspectral imaging (SWIR-HSI) and synchrotron radiation Fourier transform infrared (SR-FTIR) microspectroscopy were combined to investigate chemical and spatial–temporal changes in incremental damaged maize kernels induced by A. flavus infection at macroscopic and microscopic levels. SWIR-HSI was employed to extract spectral information of A. flavus growth and quantitatively detect AFB1 levels. Satisfactory full-spectrum models and simplified multispectral models were obtained respectively by partial least squares regression (PLSR) for three types of samples. Furthermore, SR-FTIR microspectroscopy coupled with two-dimensional correlation spectroscopy (2DCOS) was utilized to reveal the possible sequence of dynamic changes of nutrient loss and trace AFB1 in maize kernels. It exhibited new insights on how to quantify the spatio-temporal patterns of fungal infection and AFB1 accumulation on maize and provided theoretical basis for online sorting.
Distribution and transport of MPs carrying DOM in ice provide important theoretical support for lake pollution management in the northern cold dry zone.
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•Ice traps and accumulates ...MPs, contributing to pollution in ice-covered lakes.•Dominance of humus-like DOM aligns with MPs distribution in ice and water layers.•Anthropogenic factors must be considered when managing MPs pollution in ice-covered lakes.•Ice’s adsorption mechanism is vital for future research, which is linked to MPs/DOM distribution.
Due to the characteristics of low density, light weight, and strong hydrophobicity, microplastics (MPs) can adsorb dissolved organic matter (DOM) in lake water to jointly accomplish migration and transformation in the ice/water medium, which causes serious pollution to the lake during the ice period through accumulation. In this study, the distribution of Daihai Lake MPs and DOM was studied by fluorescence excited emission matrix (EEM) and micro-infrared spectroscopy, and the relationship between them was examined by two-dimensional correlation spectroscopy (2DCOS) and structural equation modelling (SEM) to obtain the influencing factors of pollution. The results indicate that the concentration of MPs in the surface ice layer is 1.35 times more than in the water and in the surface and bottom ice layers 1–2 times more than the middle layer. DOM in the ice cover is mainly protein-like (73.33%), and humus-like DOM (44.8%) is dominant in the water under the ice that is consistent with the distribution of MPs in the ice and water layer. As a result, MPs are more prospective to adsorb humus-like substances into the ice during migration. Through SEM analysis, it was concluded that human activities and the degree of economic development seriously affect the pollution level and the type of MPs and DOM in lakes. One of the most important factors in winter is the ice cover, and there is a strong correlation between the MPs and DOM in different ice layers. Combined with experimental data, it was concluded that the ice layer influences the distribution characteristics of the pollutants in lakes as well as the direction of migration. However, the adsorption mechanism of the ice is not clear, which will be a key direction for future research on microplastics in ice-covered lakes.
A comprehensive survey review of new and noteworthy developments of 2D correlation spectroscopy (2DCOS) and its applications for the last two years is compiled. This review covers not only journal ...articles and book chapters but also books, proceedings, and review articles published on 2DCOS, numerous significant new concepts of 2DCOS, patents and publication trends. Noteworthy experimental practices in the field of 2DCOS, including types of analytical probes employed, various perturbation methods used in experiments, and pertinent examples of fundamental and practical applications, are also reviewed.
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•Comprehensive survey on new and noteworthy developments and experimental practices in 2D correlation spectroscopy.•2D codistribution spectroscopy, scaling MW2D, projection MW2D, 2D heteronuclear correlation NMR spectra, pre-modeling analysis method.•Probes, like IR, Raman, NIR, fluorescence, NMR, X-ray, Mass spectrometry, etc.•Perturbation methods, like temperature, time, concentration, pH, etc., fields of applications, and types of analytical probes.•Applications, like polymers, proteins, composites, solution mixtures, etc.
Different species of bolete have different nutritional and medicinal value, which leads to the phenomenon of shoddy in the market from time to time. Therefore, consumers need a fast and effective ...detection method to identify their species. In this paper, different data pretreatment was carried out for the Fourier transform near infrared (FT-NIR) spectra, and the modeling results of partial least squares discrimination analysis (PLS-DA), support vector machines (SVM) and residual neural network (ResNet) were compared. The results show that PLS-DA and SVM models need a suitable combination of pretreatment for spectral data. The purpose is to improve the accuracy of the model and avoid over fitting. After spectral pretreatment, the accuracy of PLS-DA model were improved to 99.63% and 97.38% respectively. In order to ensure that the SVM model does not have the risk of over fitting, the accuracy of the SVM model after pretreatment were reduced to 98.5% and 93.63%. The ResNet model was established based on the original spectrum. The accuracy of the model was 100%, and there is no over fitting phenomenon, which is one of the advantages of the model. Comparing the above three models, ResNet is the best model for bolete species identification.
•The spectral modeling results of different pretreatment were compared.•ResNet model was used to accurately identify 801 fruiting bodies of bolete.•Synchronous 2DCOS spectral model has good discrimination performance.•ResNet model has good performance and does not have the problem of over fitting.
Residues of harmful dyes such as Auramine O (AO) in herb and food products threaten the health of people. So, fast and sensitive detection techniques of the residues are needed. As a powerful tool ...for substance detection, terahertz (THz) spectroscopy was used for the quantitative determination of AO by combining with an improved partial least-squares regression (PLSR) model in this paper. Absorbance of herbal samples with different concentrations was obtained by THz-TDS in the band between 0.2THz and 1.6THz. We applied two-dimensional correlation spectroscopy (2DCOS) to improve the PLSR model. This method highlighted the spectral differences of different concentrations, provided a clear criterion of the input interval selection, and improved the accuracy of detection result. The experimental result indicated that the combination of the THz spectroscopy and 2DCOS-PLSR is an excellent quantitative analysis method.
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•Terahertz spectroscopy was applied for quantitative determination of harmful dyes in herbs.•2DCOS-SPLSR (partial least squares regression based on two-dimensional correlation spectroscopy) was presented for model optimization.•2DCOS-SPLSR highlighted the spectral differences of different concentrations, provided a clear criterion of the input interval selection, and improved the accuracy.•Terahertz spectroscopy combined with 2DCOS-SPLSR is a fast, accurate and sensitive method of quantitative determination.
Undissolved humic acid (HA) has a great retention effect on the migration of hexavalent chromium Cr(VI) in soil, and HA functional groups play a predominant role in this process. However, the coupled ...mode between Cr(VI) retention and HA functional groups reaction is still unclear. In this study, it was found that a fair amount of Cr on HA existed in the forms of ion exchangeable and binding Cr(VI) during the reaction resulting from the ion exchange adsorption and complexation of Cr(VI). According to the results of two-dimensional correlation spectroscopic analysis (2DCOS), HA functional groups participated in the reaction with Cr(VI) in the order of carboxyl ≈ chelated carboxyl > phenol > polysaccharide > methyl, and all the functional groups were more likely to be located at aromatic domains. Based on the results of XPS spectra, rather than to be oxidized by Cr(VI), carboxyl more tended to be complexed by chromium, which is regarded as the precondition for Cr(VI) reduction. Phenol, polysaccharide and methyl with distinct reaction activities successively acted as major electron donors for Cr(VI) reduction in different reaction stages. Consequently, it was determined that the retention of Cr(VI) by undissolved HA followed an adsorption-complexation-reduction mechanism, and based on this, a multi-step kinetic model with multiple types of complexation/reduction sites was developed to simulate the retention processes resulting in a much better fitting effect (R2 > 0.99) compared with traditional first-order and second-order kinetic models (R2 < 0.95). This demonstrated that the multi-step kinetic model is of great potential in accurately simulating the migration and transformation of Cr(VI) in soil environment.
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•Cr(VI) retention by undissolved HA was determined to follow an adsorption-complexation-reduction mechanism.•The role of different HA functional groups for Cr(VI) retention was revealed.•The coupled mode of Cr(VI) retention and HA functional groups reaction was established.•An adsorption-complexation-reduction multi-step kinetic model with an excellent performance was proposed.
The coupled mode between Cr(VI) retention and HA functional groups reaction was established, and an adsorption-complexation-reduction multi-step kinetic model with an excellent performance was proposed.
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•A method of 2DCOS combined with deep learning to identify the storage duration of porcini is proposed.•The 2DCOS combined with deep learning method is better than the traditional ...HPLC method.•As the storage duration increases, the content of uridine and adenosine in porcini increases.•2DCOS can reflect the changes in the content of uridine and adenosine.
Quick and accurate identification of the storage duration of food is essential to food safety. Herein, two methods reported for analyzing the storage duration of porcini were two-dimensional correlation spectroscopy (2DCOS) combined with deep learning method and HPLC method. 2DCOS combined with deep learning improves the resolution of one-dimensional FT-NIR spectrum and enhances the ability to extract features to obtain a high accuracy model (100%). Used HPLC to detect the changes of chemical components in porcini, the content of uridine and adenosine increased with the increase of storage duration, and the content of guanosine did not change significantly. The accuracy of the PLS-DA model test set based on the HPLC data matrix was 55.56–80%. The results show that 2DCOS combined with deep learning is an effective tool to identify the storage duration of porcini. In addition, by analyzing the influence of uridine and adenosine content changes on the 2DCOS image, we found that the intensity of the autocorrelation peak at 5000 cm−1 can reflect the trend of content changes. It shows that 2DCOS has the potential ability to predict the changing trend of uridine and adenosine content. The 2DCOS combined with deep learning method may promote the non-destructive rapid detection and identification of the storage duration of edible mushrooms without complicated samples or data preprocessing.
•2DCOS with ResNet for the identification of Paris species was first proposed.•Multiple feature bands fusion strategy of 2DCOS was first proposed for modeling.•A total of 5040 2DCOS images were ...produced for identification analysis.•Synchronous 2DCOS has better identification performance in complex systems.
Spectral analysis has the characteristics of fast and nondestructive. In order to conform to the development of the times, a practical method beyond the traditional spectral analysis was established. For the first time, the two-dimensional correlation spectroscopy (2DCOS) images of Fourier-transform mid-infrared spectroscopy combined with the Residual Neural Network (ResNet) was used for the identification and analysis of 12 Paris species, and the second derivative 2DCOS rarely involved in previous researchers was established. Besides, the fusion strategy of 2DCOS images based on feature bands was first proposed for modeling analysis. From the results, (1) 2DCOS combined with ResNet can successfully identify 12 Paris species. (2) 2DCOS is a powerful tool for identification, whether it is used for image visual analysis or modeling analysis. (3) Compared with asynchronous 2DCOS, synchronous 2DCOS is more suitable for the identification and analysis of complex mixed systems such as traditional Chinese medicine. (4) The modeling based on feature bands fusion strategy of 2DCOS has better model performance and is also suitable for the analysis of small samples. To sum up, what we proposed is an innovative and feasible method with wide applicability, which can not only solve the problem of identifying Paris, provide ideas and methods for the selection of spectral types and feature bands, but also provide practical reference for the research in analytical chemistry and other related fields.
