Water oxidation, an essential step in photosynthesis, has attracted intense research attention. Understanding the reaction pathways at the electrocatalyst/water interface is of great importance for ...the development of water oxidation catalysts. How the water is oxidized on the electrocatalyst surface by the positive charges is still an open question. This review summarizes current advances in studies on surface chemistry within the context of water oxidation, including the intermediates, reaction mechanisms, and their influences on the reaction kinetics. The Tafel analyses of some electrocatalysts and the rate-laws relative to charge consumption rates are also presented. Moreover, how the multiple charge transfer relies on the intermediate coverage and the accumulated charge numbers is outlined. Lastly, the intermediates and rate-determining steps on some water oxidation catalysts are discussed based on density functional theories.
High-quality, thickness-controlled CdS nanosheets (NSs) have been obtained through the thermal decomposition of cadmium diethyldithiocarbamate in octadecene. Ensembles with discrete thicknesses of ...1.50, 1.80, and 2.16 nm have been made with corresponding lateral dimensions on the order of 90 nm × 20 nm. These latter values make the 1–3 nm NSs the largest 2D CdS specimens made to date using colloidal chemistry. Associated Ni nanoparticle decorated counterparts have been made through the photodeposition of Ni onto NSs with an average nanoparticle diameter of 6 nm. Subsequent photocatalytic hydrogen generation measurements have compared the performance of CdS NSs with that of their Ni NP decorated counterparts in water/ethanol mixtures. Apparent quantum yields as large as 25% have been seen for Ni NP decorated NSs with transient yields as large as 64% within the first 2 h of irradiation. Results from ensemble femtosecond transient differential absorption spectroscopy reveal that the origin of this high efficiency stems from efficient electron transfer from CdS to Ni. In this regard, the CdS/Ni semiconductor/metal heterojunction acts to dissociate strongly bound excitons in CdS NSs, creating free carriers needed to carry out relevant reduction chemistries.
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How to effectively and efficiently reduce carbon dioxide (CO2) to value-added chemicals represent a frontier in catalysis research. Due to the high activation energy needs and the ...endothermic nature of CO2 reduction, the reactions are difficult to carry out. When H2O is present, hydrogen evolution reactions (HER) often compete favorably with CO2 reduction reactions. For these reactions, catalysts are of critical importance to CO2 reduction. In this article, we review the various metal nanocatalysts for electrochemical CO2 reduction (ECR) reactions. In recognition of the importance of H2O to CO2 reduction, we focus our discussions on systems in aqueous solutions. Nanostructured metal catalysts are chosen for the discussions because they represent the most effective catalysts for ECR. After a brief introduction of the fundamental principles of ECR, we devote the rest of the article on the discussions of various types of nanostructured metallic catalysts, which are categorized by their compositions and working mechanisms. Lastly, strategies for improving reaction efficiency and selectivity are discussed.
•Acetyled and carboxymethylated derivatives of polysaccharide were prepared.•Their antioxidant and immunomodating activities were studied and compared.•The acetyled derivative with proper DS was ...superior to other derivatives.•The bioactivities are affected by the types of substitution groups and their DS.
A water-soluble polysaccharide extracted from Ganoderma atrum was chemically modified to obtain its acetyled and carboxymethylated derivatives. The results of chemical analysis, Fourier-transform infrared and 13C nuclear magnetic resonance spectroscopy showed that these modifications were successful, although the molecular weight of these derivatives decreased due to slight degradation during the reaction. The antioxidant and immunomodulating activities of these derivatives were then investigated to determine the structure–bioactivity relationship. Results showed that the acetyled derivative with appropriate degree of substitution and lower molecular weight exhibited stronger antioxidant abilities on scavenging DPPH radical, and inhibitory effects in β-carotene–linoleic acid systems compared with the native polysaccharide. In addition, it also enhanced the macrophage phagocytosis capacity and tumor necrosis factor-α secretion, whereas the carboxymethylated derivative was shown to be slightly less effective. These results indicated that the type of substitution group and their degree of substitution play a decisive role in the bioactivities of the derivatives.
A triazole‐bridged bis(β‐cyclodextrin) was synthesized via a high‐yield Click Chemistry reaction between 6‐azido‐β‐cyclodextrin and 6‐propynylamino‐β‐cyclodextrin, and then it was bonded onto ordered ...silica gel SBA‐15 to obtain a novel triazole‐bridged bis(β‐cyclodextrin)–bonded chiral stationary phase (TBCDP). The structures of the bridged cyclodextrin and TBCDP were characterized by the infrared spectroscopy, mass spectrometry, elemental analysis, and thermogravimetric analysis. The chiral performance of TBCDP was evaluated by using chiral pesticides and drugs as probes including triazoles, flavanones, dansyl amino acids and β‐blockers. Some effects of the composition in mobile phase and pH value on the enantioseparations were investigated in different modes. The nine triazoles, eight flavanones, and eight dansyl amino acids were successfully resolved on TBCDP under the reversed phase with the resolutions of hexaconazole, 2′‐hydroxyflavanone, and dansyl‐DL‐tyrosine, which were 2.49, 5.40, and 3.25 within 30 minutes, respectively. The ten β‐blockers were also separated under the polar organic mode with the resolution of arotinolol reached 1.71. Some related separation mechanisms were discussed preliminary. Compared with the native cyclodextrin stationary phase (CDSP), TBCDP has higher enantioselectivity to separate more analytes, which benefited from the synergistic inclusion ability of the two adjacent cavities and bridging linker of TBCDP, thereby enabling it a promising prospect in chiral drugs and food analysis.
The facile solution-processability of methylammonium lead halide (CH3NH3PbI3) perovskites has catalyzed the development of inexpensive, hybrid perovskite-based optoelectronics. It is apparent, ...though, that solution-processed CH3NH3PbI3 films possess local emission heterogeneities, stemming from electronic disorder in the material. Herein we investigate the spatially resolved emission properties of CH3NH3PbI3 thin films through detailed emission intensity versus excitation intensity measurements. These studies enable us to establish the existence of nonuniform trap density variations wherein regions of CH3NH3PbI3 films exhibit effective free carrier recombination while others exhibit emission dynamics strongly influenced by the presence of trap states. Such trap density variations lead to spatially varying emission quantum yields and correspondingly impact the performance of both methylammonium lead halide perovskite solar cells and other hybrid perovskite-based devices. Of additional note is that the observed spatial extent of the optical disorder extends over length scales greater than that of underlying crystalline domains, suggesting the existence of other factors, beyond grain boundary-related nonradiative recombination channels, which lead to significant intrafilm optical heterogeneities.
•The study utilizes chemometrics and metabolomics to screen for flavonoids.•It uses chromatography-mass spectrometry to target and quantify the flavonoids.•There are significant differences in rutin ...and isorhamnetin at different stages.•Isorhamnetin is in the same metabolic branching pathway as narirutin or tangeretin.•It elucidates the relationship between the structure and performance of flavonoids.
Plant-based food intake is essential for health promotion, especially in preventing chronic diseases. Flavonoids, as important bioactive substances found in citrus fruits, have a variety of health benefits, including antioxidant, anti-inflammatory, and cancer-inhibiting properties. This study used ultra-high performance liquid chromatography tandem quadrupole time of flight mass spectrometry to determine the flavonoids in the flavedo of navel oranges at different growth stages. Combined with chemometric methods to distinguish flavonoids at different growth stages, 15 differential flavonoids were deduced. In addition, the biomarker flavonoids in navel orange flavedo were quantified by high performance liquid chromatography mass spectrometry. The results showed that the contents of rutin, isosinensetin, and isorhamnetin all showed a trend of increasing and then decreasing during the growing period, while the contents of tangeretin and nobiletin would gradually decrease with the increase of fruit maturity. In addition, the analysis also revealed that the content of isorhamnetin was negatively correlated with the content of both narirutin and tangeretin, and it was hypothesized that isorhamnetin was in the same metabolic branching pathway as narirutin or tangeretin. The results of this study support the practical application of orange peel as a nutritional resource in functional foods.
The fertilization process is a critical step in plant reproduction. However, the mechanism of action and mode of regulation of the fertilization process in gymnosperms remain unclear. In this study, ...we investigated the molecular regulatory networks involved in the fertilization process in Korean pine ovules through anatomical observation, physiological and biochemical assays, and transcriptome sequencing technology. The morphological and physiological results indicated that fertilization proceeds through the demise of the proteinaceous vacuole, egg cell division, and pollen tube elongation. Auxin, cytokinin, soluble sugar, and soluble starch contents begin to decline upon fertilization. Transcriptomic data analysis revealed a large number of differentially expressed genes at different times before and after fertilization. These genes were primarily involved in pathways associated with plant hormone signal transduction, protein processing in the endoplasmic reticulum, fructose metabolism, and mannose metabolism. The expression levels of several key genes were further confirmed by qRT-PCR. These findings represent an important step towards understanding the mechanisms underlying morphological changes in the Korean pine ovule during fertilization, and the physiological and transcriptional analyses lay a foundation for in-depth studies of the molecular regulatory network of the Korean pine fertilization process.
► NIR spectroscopy was attempted to quantify the main compositions in Ganderma. ► Two quantification models, PLS and RBF network, were optimised respectively. ► Final results confirm the good ...predictability of the two models.
Two chemometrics, the partial least-squares (PLS) and radial basis function (RBF) network were performed to develop a quantification method for total polysaccharides and triterpenoids in Ganoderma lucidum and Ganoderma atrum from different origins based on near infrared reflectance spectroscopy (NIR). The influences of spectral window and spectral pre-treatments were initially studied in the construction of PLS model. The best result was obtained when the standard normal transformation (SNV) +1st derivative spectrum over 4100–7750cm−1 was used for the modelling. Then based on each principle, both of the two models were optimised respectively. The final results with high determination coefficient (R2) (higher than 0.973, 0.989 for PLS and RBF, respectively) and low root mean square errors of prediction (RMSEP) (low to 0.1109 and 0.01298 for polysaccharides and triterpenoids, respectively) confirm the good predictability of the two models. The overall results show that NIR spectroscopy combined with chemometrics can be efficiently utilised for accurate analysis of routine chemical compositions in G. lucidum and G. atrum.
•A deeper analysis of changes in compounds during navel oranges growth is conducted.•A total of 63 metabolites were identified during navel orange growth by UPLC-QTOF/MS.•Flavonoids were main ...differential metabolites, exhibiting high correlation.•KEGG highlighted the flavonoid biosynthes was a major pathway.•The inhibition rate of α-glucosidase activity exhibited ongoing reduction.
Metabolites changes during fruit growth are currently being studied intensively. In this experiment, Ultra-high performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry was used to identify metabolites during the growing phase of navel oranges. A total of 63 metabolites were identified, and monitored changes in amino acid content. Principal component analysis and Partial least-squares-discriminate analysis were used to construct a cluster analysis model among navel orange metabolites. Among the 19 differential metabolites, flavonoids were the main metabolic markers during the growth of navel oranges. Correlation cluster analysis was used to fit the correlation between the characteristic components, and it was found that many flavonoids were highly correlated. Finally, combined with Kyoto Encyclopedia of Genes and Genomes enrichment analysis, the key metabolic pathway was identified as flavonoid synthesis. The α-glucosidase inhibition experiment showed that with the growth of navel orange, the inhibition rate of the metabolites to α-glucosidase activity decreased continuously. This study provides a necessary basis for exploring the metabolic mechanism of navel orange growth.
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