The synthesis of carbon quantum dots (CQDs) with high added value from a wide range of renewable biowaste sources holds utmost significance in addressing environmental and economic concerns. Herein, we present a simple and environmentally friendly method for synthesizing high-quality fluorescent nitrogen-doped CQDs (NCQDs) using orange peel. The obtained N-CQDs were employed as an efficient on-off-on fluorescent sensor for sequential ferric ions (Fe3+) and ascorbic acid (AA) detection. The linear range for the determination of Fe3+ was observed to be 2-150 mu M, with a limit of detection (LOD) of 0.253 mu M. Additionally, within the concentration range of 30-130 mu M, the recovery fluorescence exhibited a favorable linearity with the concentration of AA. The calculated LOD for this range was found to be 1.57 mu M. In addition, the prepared N-CQDs have been readily applied as information encryption. Besides, the paper based N-CQDs sensor, combined with the RGB/HSV analysis software, provides a cost-effective and portable solution for on-site fluorescence detection. To our knowledge, it is the first time that the CQDs derived from orange peel have been utilized in the domains of anticounterfeiting and smartphone-assisted portable detection. These findings highlight the significant and diverse applications of biomass-derived CQDs.

In this work, the ultrasound-assisted hydrothermal synthesis method offers a facile method to synthesize highly efficient photoluminescence sulfur quantum dots (SQDs). Impressively, a switchable fluorescent "on-off-on" sensor was developed using the acquired SQDs, which are capable of sequentially detecting iron ions (Fe3+) and ascorbic acid (AA) with exceptional sensitivity and selectivity. Meanwhile, SQDs and Fe3+ formed complexes through coordination, causing the fluorescence quenching of SQDs because of the static quenching effect. Upon the addition of AA into the SQDs/Fe3+ system, a redox-reaction-mediated mechanism leads to the recovery of fluorescence. The fluorescence intensity of SQDs exhibits a linear relationship with the concentrations of Fe3+ and AA in the ranges 5-30 and 20-100 μM, respectively. Notably, the detection limits achieved are 14.31 nM for Fe3+ and 0.64 μM for AA. Moreover, the chemosensor was successfully employed for monitoring Fe3+ in real water samples and AA in fruits. These results demonstrate the excellent analysis and detection capabilities of SQDs in the complex environment.

Two effective flame retardant additives hsalaminopyridine phosphaphenanthrene (HAD) and methoaminopyridine phosphaphenanthrene (MAD) were respectively prepared with DOPO, aminopyridine, salicylaldehyde and 3-Methoxysalicylaldehyde. Subsequently, HAD and MAD was added into epoxy resin (EP) respectively, and flame retardancy of EP/HAD and EP/MAD thermosets were dramatically enhanced. The result of cone calorimeter (CC) test revealed that both HAD and MAD showed perfect smoke suppression performance. In respect of transmittance and mechanical properties, there was a huge difference between HAD and MAD. The introduction of HAD dramatically harmed transmittance and mechanical properties of EP, while, EP/10%MAD was transparent and nearly possessed the same mechanical properties with pure EP.

A novel intumescent flame retardant, PPMD, was designed from phosphaphenanthrene and nitrogen heterocycles through the two-step gut reactions of 1,4-phthalaldehyde and 3-methyl-1-phe-nylpyrazol-5-ylamine. After determination of its structure by nuclear magnetic resonance and Fourier-transform infrared analyses, PPMD was added to an epoxy resin (EP) to facilitate a curing process. Thus, EP/PPMD samples with excellent transparency and flame retardancy were acquired. For example, the EP sample satisfied the UL-94 V-0 standard and achieved a limiting oxygen index value of 30.5% because of the incorporation of 5 wt% PPMD. The cone calorimeter test of the EP/5% PPMD sample revealed that its total smoke production (TSP) and total heat release (THR) values of EP/5% PPMD was only 22.5% and 56.4% of the control group, respectively. Moreover, the average effective heat of combustion (av-EHC) value of EP/5% PPMD was reduced by 34.1%, indicating that PPMD possessed high flame-inhibition activity and smoke suppression efficiency. The flame-retardant mechanisms of PPMD were also investigated in gas phase by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and in condensed phase by XPS and IR.

Two new Cu(II)/Co(II) coordination polymer (CPs) namely, [Co-2(H2O)(2)(L)(2)(2,2'-bipy)(2)center dot H2O] (1) and [Cu-2(L)(2)(bbi)] (2) (H2L= 3,3'-(1,2-phenylenebis(methyleneoxy)) dibenzoic acid, bbi = 1,1'-(1,4-butanediyl)bis(imidazole), 2,2,'-bipy=2,2,'-bipyridine), have been designed and synthesized. 1 has 1D helical structure built by the connectivity of Co atoms and phenolic-oxygen containing branches of the flexible dicarboxylate linkages, which was further form a 2D supramolecular sheet through the strong pi center dot center dot center dot pi stacking interactions and H-bonded interactions. 2 exhibits 2D layer constructed by the double [Cu4L2] chains and anti-conformational bbi ligands. The current results illustrated that the N-donor ligand may play a distinct effect in the formation of these mortifies. The photocatalytic performances to degrade methyl violet (MV) and Rhodamine B (Rh B) under UV irradiation were studied. (C) 2021 Elsevier B.V. All rights reserved.

A new three dimensional Cd(II)-based MOF with composition {Cd-10(btc)(8)((bpp)(4)(Hbpp)(4)]center dot 2bpp center dot H2O} (WAU-1) has been synthesized by reaction of Cd(II) salt with 1,3,5-benzenetricarboxylic acid (H3BTC) ligand and 2,5-bis (pyrid-4-yl)pyridine (bpp) co-ligand. The single crystal X-ray analysis showed that the WAU-1 shows 3D pillar-supported framework constructed by bpp co-ligands and [Cd-3(btc)(2)] layers and exhibited typical 6-node pcu-like topology with the point symbol of{4(12).6(3)}. The sensing studies have been performed on WAU-1 which suggested that the MOF can be used as highly sensitive fluorescent sensor to detect pymetrozine (PYM) a new class of pesticide through fluorescence quenching. Furthermore, the plausible fluorescence quenching mechanism which WAU-1 displayed against PYM and other insecticides has been proposed using theoretical calculations.

The objective of this study was to develop a multi-steps infrared macro-fingerprint method to discriminate Dendrobium huoshanense “Fengdou” (DHS FD) produced under different toasting and soaking conditions as well as to examine the effect of production conditions on the total polyphenol content, total water soluble polysaccharide content, and antioxidant activities. The results showed that though the Fourier transform infrared and second derivative infrared (SD-IR) spectra of the DHS FD processed under different conditions were similar visually, the DHS FDs could be discriminated by their characteristic peaks in the range of 1800–600 cm–1 from their IR and SD-IR files and the cross-peaks in the region of 1280–950 cm–1 in their two-dimensional correlation spectroscopy IR spectra. The total polyphenol content increased and the total water soluble polysaccharide content decreased in the DHS FDs toasted at temperatures from 110°C to 190°C for 30 min. Soaking process showed variable effects on the total polyphenol content and total water soluble polysaccharide content. The total polyphenol content of the DHS FDs toasted below 150°C increased as the soaking temperatures increased while the total water soluble polysaccharide content showed an opposite trend. Both the total polyphenol content and total water soluble polysaccharide content of the DHS FDs toasted at 170°C and 190°C showed little difference when soaking temperatures varied from 4°C to 100°C. The investigation of the 2,2-Diphenyl-1-picrylhydrazyl cleaving activity revealed that toasting and soaking process might increase the antioxidant activity of the DHS while too high toasting temperatures would decrease their activity. The multi-steps infrared macro-fingerprint analysis with high resolution and excellent macroscopic fingerprint features could effectively discriminate the DHS produced under different conditions without involving any separation and extraction. Consequently, the use of this method is recommended for quality control of the DHS FD.

A rapid, green, low cost and nondestructive attenuated total reflection near infrared (ATR NIR) method was developed to quantify the total polysaccharide and the main monosaccharides mannose and glucose in Dendrobium huoshanense. Total 100 D. huoshanense samples from different places were analyzed using ATR NIR method. Potential outlying samples were initially removed from the collected NIR data using the PCA-Mahalanobis distance method. Spectral data preprocessing was studied in the construction of a partial least squares (PLS) model and six different signal pretreatment methods, including multiplicative scattering correction (MSC), standard normal transformation (SNV), first and second derivatives, the combination of MSC with the first derivative, and the combination of SNV with the first derivative, were compared. The results showed that the best signal pretreatment method was the spectral data pretreated by SNV combined with the first derivative due to it showed the lowest root-mean-square error of cross-validation (RMSECV), highest R-2 for both the polysaccharide and its main monosaccharides. In order to improve the performance of the model, the pretreated full spectrum was calculated by different wavelength selection method. The results showed that the optional wavelength selection model was the one simultaneously selecting the NIR wavelength ranges 7500-5750 cm(-1),5250-4700 cm(-1), 4450-4300 cm(-1) and 4200-4100 cm(-1) because of the lowest RMSECV and the highest R-2 among the ten wavelength selection models. The external validation and the complete external validation confirmed the robustness and reliability of the developed NIR model. The contents of the total polysaccharide and the main monosaccharides are the essential quality assessment criterion for plant medicines while their traditional quantification methods involved sample destruction, tedious sample processing and non-environmentally friendly pretreatment, therefore, our study might provide an efficient technique tool for the rapid, green and nondestructive quantification of the total polysaccharide and the main monosaccharides for D. huoshanense and other rich-in-polysaccharide plant medicines. (C) 2018 Published by Elsevier B.V.

The FTIR method was applied to evaluate the similarity of tissue-cultured and wild Dendrobium huoshanense C.Z. Tang et S.J. Cheng, Dendrobium officinale Kimura et Migo and Dendrobium moniliforme (Linn.) Sw and discriminate different Dendrobium species, especially D. huoshanense and its main goldbrick Dendrobium henanense J.L. Lu et L.X. Gao. Despite the general pattern of the IR spectra, different intensities, shapes and peak positions were found in the IR spectra of these samples, especially in the range of 1800–600cm−1, which could be used to discriminate them. The methanol, aqueous extracting procedure and the second derivative transformation obviously enlarged the tiny spectral differences among these samples. The similarity evaluation based on the IR spectra and the second derivative IR spectrum revealed that the similarity of the methanol extracts between tissue-cultured and wild Dendrobiums might be lower than that between different Dendrobium species. The similarities of the powders and aqueous extracts between tissue-cultured and wild Dendrobiums were higher than those between different Dendrobium species. The further principal component analysis showed that the first three components explained 99.7%, 87.7% and 85.1% of data variance for powder, methanol extract and aqueous extract, respectively, demonstrating a good discrimination between samples. Our research suggested that the variations of secondary metabolites between different origins of the investigated Dendrobiums might be higher than what we had supposed. Tissue culture techniques were widely used in the conversation of rare and endangered medicinal amedica, however, our study suggested that the chemical constituents of tissue-cultured plants might be quite different from their wild correspondences.