Research on Chemical Intermediates最新文献

Natural minerals as catalysts have the advantages of wide source and environmental friendliness. However, it is still challenging to develop mineral-based NH₃-SCR catalysts with high NO conversion and N₂ selectivity at low temperatures. Therefore, we use magnetic separation rare earth tailings with certain catalytic activity and acidic sites as the carrier, and introduce metal elements Mo and Ce with different valence states as active components to stimulate the catalytic activity of magnetic separation rare earth tailings by multi-element co-doping. The catalysts were tested and analyzed by XRD, XPS, BET, NH₃-TPD and other characterization methods. The results show that there is an electronic interaction between Fe, Mo and Ce on the surface of Mo-Ce/magnetic rare earth tailings catalyst. The increase of Fe³⁺, Mo⁵⁺ and Ce³⁺ promotes the adsorption of NH₃ and NO on the surface of the catalyst. With the introduction of Ce, the redox capacity and Brønsted acid strength of the catalyst at low temperature are significantly enhanced, thus accelerating the SCR reaction. The results of this study not only provide a theoretical basis for the high-value utilization of magnetic separation rare earth tailings, but also expand the raw material range of NH₃-SCR denitration catalyst.

The stainless steel mesh was covered by MOF-199 and applied in the four-component synthesis of 2-aminospiro[indeno[1,2-b]quinoxalin-11,4-pyran]-3-carbonitriles as a novel and efficient heterogeneous catalyst. The preparation of MOF-199-covered stainless steel mesh (MOF-199@SSM) was confirmed by FT-IR, FE-SEM and DEX analyses. MOF-199@SSM catalyst can be easily separated from the reaction mixture by simple forceps and reused. The stability of the catalyst was examined using a hot filtration test and no leaching occurred during the reaction. The reactions conditions were mild and the reaction times were relatively short. No by-product was produced, so, high purity and high yields of products were obtained.

A selective and efficient olefin epoxidation has been developed by Fe₃O₄@SiO₂/(TEMPO)-copolymer-(Chlorophyll b)-Co^(III) NPs as a heterogeneous magnetically recyclable nanocatalyst. The nanocatalyst was synthesized through several steps including chlorophyll b de-metallation, imine functionalization with ally amine, co-polymerization with acrylated TEMPO, re-metalation with cobalt, and immobilization on magnetite NPs. Selective catalytic epoxidation of olefins was accomplished under mild conditions and in an O₂ atmosphere. High selectivity and conversion were achieved for a variety of substrates. The results indicated a synergistic effect between TEMPO moieties and the coordinated Co^(III) centers as two active sites. The epoxide products could be separated by the heterogeneous poly(benzoic acid) with the highest possible isolated yields. Also, the heterogeneous nanocatalyst could be recycled for at least 7 consecutive cycles with a negligible reactivity loss.

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A selective and efficient olefin epoxidation with smart isolation has been developed by Fe₃O₄@SiO₂/(TEMPO)-copolymer-(Chlorophyll b)-Co^(III) NPs under mild conditions.

A mild strategy was developed for efficient preparation of acetylsalicylic acid (ASA) from the acetylation of salicylic acid (SA) and acetic anhydride (AA) assisted ultrasonic over Y-immobilized cation exchange resin (Y-CER). With this strategy, an ASA yield of 95.2% was obtained. The results showed that the increased yield was due to Lewis acidic sites (LAS) combined with ultrasonic assistance. The process reduced the AA reagent feed while lowering the reaction temperature. The characterization results showed that metal Y species were dispersedly anchored on the CER surface through S-O-Y triple-dentate bonds, resulting in abundant LAS and stable catalytic activity. Comparative experiments revealed that LAS was more favorable for the formation of ASA than Bronsted acidic sites (BAS). Furthermore, a plausible mechanism for the acetylation of SA and AA by Y-CER has been proposed. This work provided a practical protocol for improving ASA yield and reducing acid wastewater discharge, with potential application prospects.

The configurations, electronic attributes and dipole magnitudes of the TMW_n–1O_3n (TM = Mn, Fe and Co, n = 2 ~ 6) clusters have been calculated by using first–principles. The TM substitution significantly reduces the thermodynamic stability of tungsten oxide clusters. The position of tungsten atom substituted for the MnW₄O₁₅ clusters is different from those for the TMW₄O₁₅ (TM = Fe and Co) clusters. The MnW₃O₁₂, MnW₅O₁₈, FeWO₆ and FeW₅O₁₈ clusters exhibit more kinetically stable than their neighbors. The charge transfer amounts (1.066 |e|, 1.104 |e|, 1.094 |e|, 1.138 |e| and 1.137 |e|) of the MnW_n–1O_3n clusters are more than those of the TMW_n–1O_3n (TM = F e and Co) clusters. Dipole magnitudes (1.6972 Debye, 1.342 Debye and 1.5261 Debye) of the MnW₄O₁₅, FeW₃O₁₂ and CoW₃O₁₂ clusters are larger than neighboring TMW_n–1O_3n clusters.

Benzothiazole, hydrazine/ammonia and salicylaldehyde were selected as basic unit for constructing of bis-Schiff base molecules with excited state intramolecular proton transfer (ESIPT) property. Herein, “turn-on” fluorescent performance and highly sensitive multifunctional fluorescence probes were developed to stably and efficiently detect Pb²⁺, Mg²⁺ and Al³⁺ in biological and environmental samples. Among them, BF-SJ could distinguish Pb²⁺ and Mg²⁺ ions under different pH conditions, while BF-SO could separate Pb²⁺ and Al³⁺ by different emission wavelength. More important, target ions could be distinguished by naked eyes with color change of solution under sun light and ultraviolet lamp. The LOD values of BF-SJ and BF-SO for Pb²⁺/Mg²⁺ and Pb²⁺/Al³⁺ were as low as 31.23 μM, 25.95 μM, 59.57 μM and 1.38 μM, respectively. Ideally, they showed low cytotoxicity and were successfully used for imaging of exogenous Pb²⁺/Mg²⁺ and Pb²⁺/Al³⁺ in HeLa cells. Also, BF-SJ exhibited satisfactory performance in detection of Mg²⁺ in seawater and test paper experiment.

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Ternary I-III-VI quantum dots, unlike traditional binary counterparts, offer advantages like low toxicity, cadmium-free composition, tunable electronic properties, and near-infrared light emission, making them increasingly popular for their cost-effectiveness and versatile applications in light emission. In this study, monodispersive, water-soluble, highly emissive CuInS₂@ZnS quantum dots were synthesized using cysteine and threonine as ligands by a simple one-pot solution method. By adjusting, the ratio of cysteine to threonine to 1:5 and the heating time during the synthesis process to 40 min, CuInS₂@ZnS quantum dots achieved the highest fluorescence intensity. Then, CuInS₂@ZnS quantum dots were applied for ciprofloxacin (CIP) detection in food sample, showing a linear range of 2–18 μg/ml and a lowest detection limit of 0.28 μg/ml. The fluorescent probe was successfully established by quenching process as CIP concentration increasing, due to photoinduced electron transfer. Experimental results demonstrated the detection method has high sensitivity and good selectivity. We, then utilized smartphones to visually distinguish CIP concentrations based on the colors emitted by the CuInS₂@ZnS quantum dots under UV light. The method was finally effectively to detect residual CIP in porcine kidneys, with recoveries of 92%–98%. This approach has promising potential for enhancing food safety testing.

A series of Ni-substituted LaCu_1-xNi_xO₃ (x = 0, 0.1, 0.3, 0.5 and 0.7) catalysts were prepared by a mechanochemical synthesis method and the prepared samples were used in catalytic combustion of methane. The catalytic results indicated that the partial substitution of Ni affected the catalytic performance and the increase in nickel content increased the catalytic activity and among the prepared catalysts the LaCu_0.5Ni_0.5O₃ sample possessed the highest catalytic activity and thermal stability. The results showed that methane conversion reached from 7.8 to 73.8% at 500 °C with the substitution of Ni in the amount of x = 0.5. Also, the addition of Ni instead of Cu in the LaCu_1-xNi_xO₃ led to an increase in total pore volume and specific surface area and a decrease in average crystalline size. According to O₂-TPD profiles of the LaCu_1-xNi_xO₃ catalysts, mobility of lattice oxygen (O²⁻) has a crucial role in determining the performance of these catalysts. The H₂-TPR results indicated that the addition of Ni slightly improved the reducibility of catalysts. Furthermore, a decrease in calcination temperature of LaCu_0.5Ni_0.5O₃ catalyst resulted in an increase in the catalytic activity due to the enhancement in the concentration of oxygen vacancy and specific surface area. Also, the results revealed that the increase in feed ratio (CH₄/O₂) leads to an increment in methane conversion.

New nitrobenzyl-pyridyl ether ligands were synthesized by reacting nitrobenzyl bromide (2-, 3- and 4-nitro) and halogen-substituted hydroxy pyridine (2-chloro-3-hydroxy-pyridine, 2-bromo-3-hydroxy-pyridine) compounds in DMF. By interacting the obtained ligands (L1, L3, L4 and L6) with silver (I) nitrate, transition metal complexes were prepared (AgL1, AgL3, AgL4 and AgL6). The structures of the synthesized ligands and complexes were characterized using FTIR, HRMS, ¹H-NMR and ¹³C-NMR spectroscopic techniques. In addition, fluorescence spectra of the ligands (L1-L6) were detected in the presence of different metal cations (Li⁺, Na⁺, Mg²⁺, Al³⁺, K⁺, Ca²⁺, Cr³⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Ag⁺). In addition, the thermal behavior of all compounds were examined by TGA-DTA methods and the data of silver complexes and ligands were compared. Within the scope of the study, the antibacterial activities of all compounds were investigated against 4 pathogens, 2 of which were plant-borne (Xanthomonas vesicotoria, Clavibacter michiganensis subsp. Michiganensis) and 2 were food-borne (Escherichia coli, Listeria monocytogenes).

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Carbon quantum dots (CQDs), as a novel type of carbon nanomaterial, are widely used in fields such as drug delivery, biosensing, fluorescent probes, and photocatalysis, benefiting from their excellent photostability, water solubility, biocompatibility, fluorescence, low-cost, and green non-toxicity. Meanwhile, due to the conjugated π structure of CQDs and surface defects generated by sp² hybridization, they possess unique optoelectronic properties, including tunable fluorescence, good upconversion photoluminescence, and efficient photoelectron transfer. These properties are key to the role of CQDs in the field of photocatalysis. This review summarises CQDs’ research progress and reaction mechanisms in photocatalysis, including their optical properties and synthesis strategies. Emphasis was placed on the application of CQDs in the field of photocatalysis, including photocatalytic CO₂ conversion, degradation of organic and heavy metal pollutants, hydrogen production, and nitrogen fixation. In addition, the challenges and prospects of CQDs in the field of photocatalysis are discussed, providing new ideas for studying CQDs photocatalytic materials.

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