Revealing the correlation between adsorption energy and activation energy to predict the catalytic activity of metal oxides for HMX using DFT

Traditional selection of combustion catalysis is time-consuming and labor-intensive.Theoretical calculation is expected to resolve this problem.The adsorption energy of HMX and O atoms on 13 metal oxides was calculated using DMol3,since HMX and O are key substances in decomposition process.And the relationship between the adsorption energy of HMX,O on metal oxides(TiO_(2),Al_(2)O_(3),PbO,CuO,Fe_(2)O_(3),Co_(3)O_(4),Bi_(2)O_(3),NiO)and experimental T30 values(time required for the decomposition depth of HMX to reach 30%)was depicted as volcano plot.Thus,the T30 values of other metal oxides was predicted based on their adsorption energy on volcano plot and validated by previous experimental data.Further,the adsorption energy of HMX on ZrO_(2)and MnO_(2)was predicted based on the linear relationship between surface energy and adsorption energy,and T30 values were estimated based on volcano plot.The apparent activation energy data of HMX/MgO,HMX/SnO_(2),HMX/ZrO_(2),and HMX/MnO_(2)obtained from DSC experiments are basically consistent with our predicted T30 values,indicating that it is feasible to predict the catalytic activity based on the adsorption calculation,and it is expected that these simple structural properties can predict adsorption energy to reduce the large quantities of computation and experiment cost.

Atomic-level coupled RuO_(2)/BaRuO_(3) heterostructure for efficient alkaline hydrogen evolution reaction

The slow water dissociation is the rate-determining step that slows down the reaction rate in alkaline hydrogen evolution reaction(HER).Optimizing the surface electronic structure of the catalyst to lower the energy barrier of water dissociation and regulating the binding strength of adsorption intermediates are crucial strategy for boosting the catalytic performance of HER.In this study,RuO_(2)/BaRuO_(3)(RBRO)heterostructures with abundant oxygen vacancies and lattice distortion were in-situ constructed under a low temperature via the thermal decomposition of gel-precursor.The RBRO heterostructures obtained at 550℃ exhibited the highest HER activity in 1 M KOH,showing an ultra-low overpotential of 16 mV at 10 mA cm^(-2)and a Tafel slope of 33.37 m V dec^(-1).Additionally,the material demonstrated remarkable durability,with only 25 mV of degradation in overpotential after 200 h of stability testing at 10 mA cm^(-2).Density functional theory calculations revealed that the redistribution of charges at the heterojunction interface can optimize the binding energies of H*and OH*and effectively lower the energy barrier of water dissociation.This research offers novel perspectives on surpassing the water dissociation threshold of alkaline HER catalysts by means of a systematic design of heterogeneous interfaces.

Comparison of Polysaccharides Content among Common Fruits

[Objectives]Polysaccharides in common fruits were determined and compared.[Methods]Polysaccharides in fresh bananas,apples,grapes and strawberries purchased from local markets were extracted using water extraction-alcohol precipitation method and determined using 3,5-dinitrosalicylic acid(DNS)method.[Results]The content of polysaccharides in banana was relatively high.The optimal conditions for DNS colorimetry were as follows:measurement wavelength of 510 nm,color developer of 1.0 mL,color development temperature of 90℃,color development time of 5min and stabilization time within 30 min.[Conclusions]The reproducibility and recovery rate of this method are ideal.It shows that the method is highly precise and is helpful for the research of fruit polysaccharides.This study provides a certain reference value for the development and application research of fruit polysaccharide resources in China.

Vacancy engineering induced reaction kinetics enhancement of cobalt metaphosphate for pH-universal hydrogen evolution

Developing efficient pH-universal hydrogen evolution reaction(HER)catalysts is critical in the field of water electrolysis,however,which is severely hampered by the sluggish kinetics in alkaline media.Herein,a ruthenium(Ru)incorporation induced vacancy engineering strategy is firstly proposed to precisely construct oxygen vacancy(V_(O))-riched cobalt-ruthenium metaphosphate(CRPO)for high-efficiency pH-universal HER.The V_(O) modifies the electronic structure,improves the superficial hydrophilic and gas spillover capacity,it also reduces the coordination number of Ru atoms and regulates the coordination environment.Theoretical calculations indicate that Ru tends to adsorb H_(2)O and H^(*),whereas V_(O) tends to adsorb OH^(-),which greatly promotes the H_(2)O adsorption and the dissociation of HO-H bond.Ultimately,CRPO-2 exhibits remarkable HER performance,the mass activity is about 18.34,21.73,and 38.07 times higher than that of Pt/C in acidic,neutral,and alkaline media,respectively,at the same time maintain excellent stability.Our findings may pave a new avenue for the rational design of electrocatalysts toward pH-universal water electrolysis.

One-pot synthesis of interconnected Pt95Co5 nanowires with enhanced electrocatalytic performance for methanol oxidation reaction

Shape- and composition-controlled synthesis of platinum-based nanocrystals （NCs） is critical for the development of electrocatalysts that have high activity toward the methanol oxidation reaction （MOR） in direct methanol fuel cells （DMFCs）. We report one-pot surfactant-free synthesis of interconnected PtgsCo5 nanowires （NWs） via an oriented attachment process, which has distinct advantages over conventional template- and surfactant-assisted approaches. Enhanced electrochemical activities toward MOR were confirmed through comparison with pure Pt NWs and commercial Pt/C catalyst. Pt95Co5 NWs demonstrated the highest current density during the long-term stability test. These results reveal that the introduction of the 3d-transition metal Co can reduce the catalyst cost and contribute to the improvement of electrochemical performance. The integrated design of interconnected NW structure, bimetallic composition, and clean surfaces in the present system may open a new way to the development of excellent electrocatalysts in DMFCs.

In situ formation of fluorescent silicon-containing polymer dots for alkaline phosphatase activity detection and immunoassay

The discovery and application of analyte-triggered fluorophore generation or fluorogenic reaction are significant and beneficial to the development of novel fluorescence(FL) analysis method. In this study, for the first time, we have reported a fluorogenic reaction to prepare fluorescent silicon-containing polymer dots(Si-PDs) by simply mixing N-[3-(trimethoxysilyl)propyl]ethylenediamine(DAMO) and hydroquinone(HQ) in aqueous solution at ambient temperature. Inspired by the alkaline phosphatase(ALP)-catalyzed hydrolysis of the substrate sodium 4-hydroxyphenyl phosphate(4-HPP) into HQ and the resultant HQcontrolled intense green Si-PDs generation, we have established a straightforward ALP activity assay by innovatively employing commercially available 4-HPP as the substrate. More significantly, the specific preparation method, clear formation mechanism and excellent performance enable the Si-PDs as well as its generation process to develop facile and attractive FL immunoassay.With the help of the universal ALP-based enzyme-linked immunosorbent assay(ELISA) platform and corresponding antibody, a convenient and conceptual ALP-based fluorescent ELISA has been constructed and applied in sensing cardiac troponin Ⅰ(cTnI),a well-known biomarker of acute myocardial infarction. Our research via in situ formation of fluorescent nanomaterials has great potential application in ALP activity assay, inhibitor screening, and disease diagnosis.

A pH-regulated stimuli-responsive strategy for RNA-cleaving DNAzyme

RNA-cleaving DNAzymes possess important roles in DNAzymes and have been widely used in the biosensors,DNA nanomachines owing to their ion-specific dependence.However,there are still challenges in constructing universal but versatile stimuli-responsive strategies of RNA-cleaving DNAzymes.Herein,a stimuli-responsive strategy for RNA-cleaving DNAzyme is proposed by the artful design of hairpin nanostructure,in which the activities of DNAzyme(Pb2+-dependent DNAzyme as a model)in the hairpin’s loop are p H-regulated by using the triplex stem as the"lock".Upon introducing the"key",p H values,the DNAzyme will be activated and fragment the substrate of it in the presence of Pb2+,accompanied by the turn-on of the fluorescence quenched by fluorescence resonance energy transfer(FRET).The regulation ability of p H can be controlled by the length and sequence of the triplex stem,and the wide p H regulation range may be helpful for the application of DNAzymes in biological medicine delivery systems.

Tunable catalytic activity of FeWO_(4) nanomaterials for sensitive assays of pyrophosphate ion and alkaline phosphatase activity

Alkaline phosphatase(ALP)activity and pyrophosphate ion(PPi)levels are remarkable for the human body functions such as signal transduction pathways and metabolism.Current quantitative methods mainly focus on developing complicated organic substrates or employing unstable metal ions as signal-regulated medium.Herein,we have developed a facile hydrothermal method for preparing Fe WO_(4)nanomaterials with intrinsic peroxidase-like activity and further confirmed that such a catalytic activity could be significantly enhanced by adjusting the size and oxygen vacancy content.More encouragingly,PPi can easily inhibit the catalytic activity of Fe WO_(4),whereas orthophosphate ions(Pi)cannot.Therefore,we constructed an Fe WO_(4)-based colorimetric assay for sensing PPi by means of the classical 3,3′,5,5′-tetramethylbenzidine-peroxidase chromogenic reaction.A facile and reliable ALP activity assay was also designed and developed because of the logical regulation of the peroxidase-like activity of Fe WO_(4)through the ALP-catalyzed hydrolysis of PPi into Pi.Based on the clear mechanism and mimetic-enzyme Fe WO_(4)-catalyzed amplification,the sensing system exhibited excellent performance and was able to evaluate ALP activity in real serum samples and screen for potential ALP inhibitors.The proposed mimetic enzyme-involved colorimetric assay provides an alternative pathway,and Fe WO_(4)nanomaterials with excellent performance have great potential for further biosensing and biomedical applications.

Fluorescence immunoassay based on alkaline phosphatase-induced in situ generation of fluorescent non-conjugated polymer dots

Alkaline phosphatase(ALP) activity assay is not only significant to the clinical diagnosis of some related disease, but also momentous to the construction of ALP-based enzyme-linked immunosorbent assay(ELISA). Herein, for the first time, we have discovered that ascorbic acid(AA) can specially react with N-methylethylenediamine(N-MEDA) to generate fluorescent non-conjugated polymer dots(NCPDs) under mild conditions. On the basis of the AA-responsive emission and ALP-catalyzed hydrolysis of ascorbic acid 2-phosphate(AA2P) to AA, we have exploited a fluorometric ALP activity assay with high sensitivity and selectivity. Furthermore, by means of conventional ALP-based ELISA platform, a conceptual fluorescent ELISA has been constructed and applied in the potential clinical diagnosis, during which cardiac troponin I(cTnI), a well-established biomarker of acute myocardial infarction, has been chosen as the model target. We envision that such original fluorescent NCPDs generation-enabled ELISA could become a versatile tool in biochemical sensing and medical diagnosis in the future.