Sandwich-like m-Ti 3 C 2 /Fe 3 O 4 composites derived from electrostatic assembly exhibit highly effective electromagnetic (EM) wave absorption capacity. We demonstrate the influence of regulating electron hopping behaviors on EM characteristics and absorption performance.

Pyrite FeS2 now emerges as a promising anode for potassium-ion batteries (PIBs) due to its low cost and high theoretical capacity. However, the significant volume expansion, low electrical conductivity, and the ambiguous mechanism related to potassium storage severely hinder its development for PIBs anodes. Herein, FeS2 nanostructures are skillfully dispersed on the graphene surface layer by layer (FeS2@C-rGO) to form a sandwich structure by using Fe-based metal organic framework (Fe-MOF) as precursors. The unique structural design can improve the transfer kinetics of K+ and effectively buffer the volume expansion during cycling, thereby enhancing the potassium storage performance. As a result, the FeS2@C-rGO delivers a high capacity of 550 mAh/g at a current density of 0.1 A/g. At a high rate of 2 A/g, the capacity can maintain 171 mAh/g even after 500 cycles. Moreover, the electrochemical reaction mechanism and potassium storage behavior are revealed by in-situ X-ray diffractionand density functional theory calculations. This work not only provides a novel insight into the structural design of electrode materials for high-performance PIBs, but also proposes a valuable understanding of the potassium storage mechanism of the FeS2-based anode.

A sensitive and accurate chemiluminescence (CL) method was developed for one-step determination of diphenyl ether herbicides at trace level with nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) as a model analyte. Candida rugosa lipase (CRL) was immobilized on a nanocarrier of amine-linked covalent organic framework (named as COF-300-AR) through a self-assembly strategy. The formed nanocomposite of COF-300-AR@CRL owns dual enzymatic catalytic activities. It can directly catalyze luminol-dissolved oxygen reaction to produce an intense CL emission by virtue of oxidase mimic activity of COF-300-AR but also effectively decompose nitrofen to release phenolic compounds by the immobilized CRL. The released phenolic compounds own strong reducing capacity and in turn decrease the CL signal sharply. Under the optimal conditions, the decreased CL intensity presents a good linear response to nitrofen concentration in the 0.02–50.0 μM range. The limit of detection (LOD, 3sb/S) is 11 nM and the precision is 2.0

Ti3C2Tx can dissipate energy well due to its high conductivity, but at the expense of severe electromagnetic (EM) wave reflection, which is exacerbated by self-stacking. Despite various attempts to tackle this problem, the excessive isolation of Ti3C2Tx and massive high-density inorganic components render these designs unfavorable for lightweight and broadband absorption. Meanwhile, improvements in absorption performance are related to active surface and polarization interface expansion, as well as conductive path reconstruction, but the main contributing factor remains unknown. In this work, the dual-shell structured Ti3C2Tx@CNTs/Ni-HS (hollow sphere) composites are fabricated. This structure creates a confined dissipation cage, where the CNTs/Ni shell confines the electron transfer among spheres and prevents self-restacking and the tightly contacted Ti3C2Tx shell forms an uninterrupted conductive path for effective dissipation. Therefore, Ti3C2Tx@CNTs/Ni-HS-1 exhibits a broad effective absorption band of 6.1 GHz and a minimum reflection loss of -64.6 dB at a mass ratio of only 15 wt%. Importantly, when hollow structure cracks, although large active surface and polarizable interface remain, the absorption capacity of fragmented Ti3C2Tx@CNTs/Ni-HS-1 deteriorates, indicating rational conductive path in confined dissipation cage is the main factor in achieving excellent performance. This work provides new insight for the rational design of high-performance absorbers.

Intramolecular π-aromatization is a trait of many organic compounds that enhances the stability of their structures and polarizes related C-C π bonds. In contrast, rare study is focused on this phenomenon in metal clusters. Many existing homometallic clusters exhibit aromaticity, often characterized by nonpolar metal-metal bonds and a high degree of symmetry. However, synthesizing low-symmetric homometallic clusters with high-polar metal-metal bonds is challenging due to their limited thermodynamic stability. Herein, we report a facile strategy for the synthesis of [Au(μ2 -ER2 )]3 -AuPMe3 (E=Ge, Sn; R2 =1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) clusters and reveal a novel stabilization mode, intramolecular σ-aromatization. Our electronic structure analyses show that these low-symmetric clusters possess a ten-electron σ-aromatic system, which is achieved via intramolecular σ-aromatization. Moreover, the strength of σ-aromaticity gives rise to a polarity-tunable exo-Au-Au bond.

A simple and feasible strategy was developed for the preparation of fluorescent covalent organic frameworks (COFs) TpPa-1@FL. The TpPa-1-1@FL was prepared via a self-assembly strategy by soaking non-fluorescent COFs TpPa-1 into strong fluorescent fluorescein (FL) solution. A chemiluminescence resonance energy transfer (CRET) system was constructed by the combination strong fluorescent TpPa-1@FL with TCPO-hydrogen peroxide (H2O2) reaction. The chemiluminescence (CL) signal of the system was further improved by the addition of bovine serum albumin (BSA). The CRET system can determine H2O2 with a linear range response from 5.0 mmol/L to 20.0 mmol/L and a detection limit of 1.1 mmol/L. The CRET system was further exploited for indirect detection of uric acid with coupling of uricase. A good linear relationship was obtained for uric acid in the 10.0-400.0 mmol/L concentration range with a detection limit of 3.8 mmol/L. The practicability of this method was assessed by the determination of uric acid in real samples of human serum and urine. (C) 2021 Elsevier B.V. All rights reserved.

In order to promote the integration of theory and experiment teaching of titration analysis, based on the experience of online teaching mode during the epidemic period, we practiced the virtual experiment classroom teaching mode assisted by micro teaching assistant for teaching of titration analysis.This teaching mode is flexible and free from the restriction of administrative class division and theory and experiment teaching sequence, which can effectively improve the efficiency of experimental teaching and promote the integration of theory and experiment teaching.

Covalent organic frameworks (COFs) are considered to be a promising support material for catalyst due to their highly ordered porous structure. Here, a core-shell structured Fe3O4 magnetic covalent organic framework (Fe3O4@COF) was synthesized and employed to provide basic sites for immobilization of gold nanoparticles (AuNPs). The AuNPs was in-situ immobilized on the shell of Fe3O4@COF via a citrate reducing method. The Fe3O4@COF-AuNP had convenient magnetic separability and exhibited excellent mimicking peroxidase-like activity in catalyzing chemiluminescence (CL) reaction of luminol with hydrogen peroxide (H2O2). With acetylcholine chloride (ACh) as substrate of acetylcholinesterase (AChE), a CL method was exploited for sensitive detection of organophosphorus pesticide triazophos due to its irreversible inhibiting effect on the AChE activity and subsequently influences the production of H2O2 under the condition of choline oxidase (ChOx). This method gave a good linearity for triazophos in the range of 5.0-300.0 nmol L-1, and a limit of detection (LOD) of 1 nmol L-1 was acquired. The applicability of this method was verified by the determination of triazophos in different spiked vegetable samples.

A label-free chemiluminescent resonance energy transfer (CRET) platform was constructed for determination of alkaline phosphatase (ALP) activity. Luminescent metal organic frameworks (MOFs) were prepared by encapsulating terbium ion in frames of zinc-MOFs through hydrothermal synthesis and post-modification. The Tb@Zn-MOFs displays good luminescent property and can be capable of acting as an energy acceptor of chemiluminescence (CL) reaction between bis(2,4,6-trichlorophenyl)oxalate (TCPO) and hydrogen peroxide (H2O2), producing strong CL signal. Alkaline phosphatase (ALP) transforms its substrate adenosine 5 '-monophosphate into phosphate anion via enzyme catalytic reaction. The produced phosphate anion induces a noticeable blocking effect on the CL energy transfer efficiency and results in a prominent decrease in the CL signal. The CRET platform exhibits a good linear response for ALP activity from 0.1 to 70.0 mU.mL(-1), a low detection limit of 0.05 mU.mL(-1) and an acceptance precision (The relative standard deviations are less than 4% for 1.0 and 10.0 mU.mL(-1) ALP solution, n = 11). The approach was successfully applied to determination of ALP activity in human serum samples. The luminescent MOF-based CRET platform presents a feasible strategy to develop new sensors in biological fields.

A chemiluminescence (CL) sensor was constructed for the one-step determination of glucose. Glucose oxidase (GOx) was successfully encapsulated into Zn-doped zeolitic imidazolate framework-67 (Zn–ZIF–67) via a simple one-pot strategy. The as-prepared GOx@Zn–ZIF–67 nanocomposite can trigger cascade reactions of glucose oxidation to generate H2O2 and H2O2-mediated luminol reaction to give an intense CL emission. The sensor responds linearly to glucose in the 20.0–400.0 μmol·L–1 range with a limit of detection (LOD) of 4.7 μmol·L–1. Eleven replicated measurements of 200.0 μmol·L–1 glucose solution gives a relative standard deviation (RSD) of 1.7%. The sensor exhibits good selectivity and stability and was successfully applied to the determination of glucose in real human serum samples. Schematic representation of one-step determination of serum glucose with GOx@Zn–ZIF–67 nanocomposite triggering cascade reactions between luminol and glucose.

A covalent organic framework (COF) with aggregation-induced emission (AIE) property was successfully synthesized through in situ marriage of a commonly used AIE molecule tetraphenylethylene (TPE) with Schiff base network (SNW-1) through a simple one-pot method. The TPE@SNW-1 was characterized with different techniques of Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and nitrogen adsorption/desorption experiments. The fluorescence of the TPE@SNW-1 strongly depends on the composition of tetrahydrofuran–water binary system. The AIE property of TPE@SNW-1 was directly supported with particle size distribution by dynamic light scattering technique. With the TPE@SNW-1 as an energy acceptor, a chemiluminescence resonance energy transfer (CRET) system was constructed with bis(2,4,6-trichlorophenyl) oxalate (TCPO)–hydrogen peroxide (H2O2) reaction as an energy donor. The chemiluminescence (CL) signal displays a good linear relationship with concentration of H2O2 in the 5.0–1000.0 μmol·L−1 range, and a detection limit of 2.34 μmol L−1. The system was further exploited to determine uric acid based on the fact that equal stoichiometric amount of H2O2 can be concurrently generated under the catalysis of uricase. The procedure exhibits a linear response to uric acid concentration in the range 10.0–150.0 μmol·L−1 and a detection limit of 4.94 μmol·L−1. The practicability of the method was demonstrated  in the determination of uric acid in human serum samples.

HRP@ZIF–8 nanocomposite was prepared by in situ encapsulation of horseradish peroxidase (HRP) in the frame of zeolitic imidazolate framework–8 (ZIF–8) with a simple one-pot method. The HRP@ZIF–8 nanocomposite displays outstanding thermal stability and efficiently catalyzes the chemiluminescence (CL) reaction of luminol with hydrogen peroxide (H2O2) under near-neutral pH condition (pH 7–8). This CL system has a good response to H2O2 with a linear range of 0.1–100.0 μmol L−1. The limit of detection (LOD) is 0.06 μmol L−1 H2O2. By marriage with cholesterol oxidase, cholesterol is determined with a linear range from 0.1 to 100.0 μmol L−1 and a LOD of 0.04 μmol L−1. The relative standard deviations (RSD) are 1.7% and 2.5%, respectively, in 11 repeated measurements of 50.0 μmol L−1 solutions of H2O2 and cholesterol, indicating excellent precision of the method. The method shows good selectivity and has been applied to the determination of total cholesterol in real serum samples. No significant difference has been observed between the results obtained by this method and the cholesterol oxidase–peroxidase coupling method.

A Fe-porphyrin covalent organic framework (Fe-PorCOF) was prepared through a postmodification strategy and characterized using different techniques. Fe-PorCOF exhibits an inherent peroxidase/oxidase mimetic catalytic activity and sharply accelerates chemiluminescence (CL) reactions between luminol and hydrogen peroxide (H2 O2 ) or dissolved oxygen (O2 ) under alkaline conditions. The catalytic role was attributed to a significant increase in production of reactive oxygen species. Using the imminent peroxidase mimetic catalytic activity of Fe-PorCOF, a new CL method was developed for determination of H2 O2 over a linear range from 0.01 to 10.0 μmol·L-1 and with a limit of detection of 5.3 nmol·L-1 . The combination of the peroxidase mimetic catalytic activity of Fe-PorCOF with the catalytic activity of glucose oxidase on glucose oxidation presents a sensitive CL method for glucose assay. The linear range and the detection limit for glucose were 0.05-8.0 μmol·L-1 and 4.0 nmol·L-1 , respectively. The practicability of this method was assessed by determination of glucose in human sera. As a peroxidase/oxidase mimetic, Fe-PorCOF is easy to prepare and exhibits good catalytic efficiency in the luminol reaction. We believe that this strategy will promote the development of a CL field with functional COFs as a catalyst.

: This paper introduces the reform measures on the general chemistry principle laboratory, which is provided for the science-majored students by the chemistry laboratory center of Xi’an Jiaotong University after the admissions by categories. The reform involves many aspects, including reforming the laboratory teaching system, adopting the hybrid teaching method, blending in the course ideological element and strengthening the process evaluation, etc. These measures correspondingly enhanced the cultivation to the students’ awareness of environmental, active exploration, scientific thinking and practical and realistic scientism. The acquired results were also presented.

: The applied chemistry major of Xi’an Jiaotong University adheres to undergraduate education, emphasizes the intersection of science and engineering, and strives to construct a first-class applied chemistry major. By innovatively teaching students in all aspects, including subject orientation, talent training concept, curriculum and teaching material reform, teacher team construction, and teaching and research integration, it has cultivated the leading talents with strong patriotism, solid scientific and mathematical foundation, in-depth interdisciplinary, outstanding innovation ability, and the ability to inherit the “westward relocation spirit”.

A luminescent metal organic frameworks (MOFs)-based chemiluminescence resonance energy transfer (CRET) platform was constructed for turn-on detection of fluoride ion. A hybrid MOFs was prepared by encapsulating strong fluorescence 2',7'-dichlorofluorescein (DCF) into the frames of NH2-MIL-101(Al) MOFs, which led to a significant suppression of fluorescence signal of DCF. In the presence of fluoride ion, it destroyed the structure of the hybrid MOFs and released DCF molecules from the frames due to the formation of more stable aluminum hexafluoride complex ions [AlF63-] between fluoride ion and aluminum ion. The released DCF molecules accepted the energy originating from the chemical reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide (H2O2), producing a strong chemiluminescence (CL) emission. The CL signal was strong dependent on the concentration of fluoride ion presented and showed a linear response in the range of 0.5-80.0 μmol L-1 (9.5 μg L-1-1.52 mg L-1). The detection limit was 0.05 μmol L-1 (about 0.95 μg L-1) fluoride ion and the relative standard deviations was 2.3% for 40.0 μmol L-1 fluoride ion solution (n = 11). This MOFs-based CRET method was successfully applied to the determination of fluoride ion in drinking water samples, demonstrating its potential application in analysis of real samples.

It is found that a covalent triazine framework (CTF–1) (that was prepared from 1,4–dicyanobenzene) exhibits oxidase–like activity toward the oxidation of luminol with dissolved oxygen in alkaline condition to produce intense blue chemiluminescence (CL). The reaction follows Michaelis–Menten kinetics and shows strong specificity for luminol. Reactive oxygen species including 1O2, •OH and O2•− are testified to be involved in the reaction and responsible for the CL. The reaction was applied to the determination of the radical–scavenging activity of antioxidants, with rutin, kaempferol and ferulic acid serving as model scavengers. A sensitive CL method was developed for the determination of rutin based on its inhibitory effect on the reaction. The CL system gave a linear response to the concentration of rutin in the range of 0.03–0.25 μmol·L−1 with a limit of detection of 0.015 μmol·L−1. The practicability of the method was demonstrated by successful determination of rutin in tablets and in Flos Sophorae Immaturus.

Direct chemiluminescence (CL) of fluorescent gold nanoclusters was observed for the first time upon oxidation with classic oxidants. The CL mechanism was investigated by the studies of CL spectrum, UV–vis absorption spectra and X-ray photoelectron spectra before and after the reaction. The excited state Mn(II)∗, originating from the reduction of permanganate with gold nanoclusters, was suggested as the possible luminophor for the reaction. The potential analytical application was demonstrated by using hydrogen peroxide as an example, based upon the fact that hydrogen peroxide decreased the CL signal significantly. The decreased CL intensity was proportional to the concentration of hydrogen peroxide in the range 1.0×10−6–1.0×10−4molL−1. The detection limit was 5×10−7molL−1 and the relative standard deviation was 1.4% for 1.0×10−5molL−1 hydrogen peroxide in 11 replicated measurements. This method was applied to the determination of hydrogen peroxide in water samples with satisfactory results.

介绍了大学化学课程思维导图的制作方式、制作思路和制作步骤,探讨了将思维导图用于大学化学课程各章节学习的具体表现形式,以及如何利用思维导图学好大学化学课程.采用思维导图学习方法后,学生对大学化学知识的掌握程度明显提升,学习的主动性得到增强,学习效率得以提高,尤其提高了学生的归纳总结能力.

The authors describe a colorimetric method for the determination of the activity of acetylcholinesterase (AChE). Manganese dioxide (MnO2) nanosheets directly reacts with 3,3′,5,5′–tetramethylbenzidine (TMB) in the absence of hydrogen peroxide (H2O2). This leads to the formation of a blue product (oxTMB) with an absorption peak at 652 nm. If AChE hydrolyzes its substrate acetylthiocholine chloride, thiocholine is formed which blocks the oxidative power of the MnO2 nanosheets. Hence, oxTMB will not be formed. The decreased absorbance is directly related to the AChE activity in the 0.01–1.0 mU·mL−1 range. The detection limit is 0.01 mU·mL−1 and the relative standard deviation is 1.2% (for n = 11 at 0.5 mU·mL−1). The method was also applied to screen for inhibitors of AChE.