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Blue/red dual color up-conversion emission from Tm3+, Yb3+ co-activated nephelline particles derived from LTA zeolites
摘要： Up-converted blue/red dual color emitting Tm3+, Yb3+ co-activated crystalline (NaAlSiO4:Tm3+, Yb3+) materials have been fabricated via a facile, highly controllable, and cost-effective method, that is, the combination of ion exchange and thermal treatment in air. Under the 980 nm excitation, the NaAlSiO4:Tm3+, Yb3+ phosphor powders showed bright visible color blue (480 am) and red(650 nm) emission，which were attributed to the 1G4 →3H6 and 1G4→3F4 transitions of Tm3+ ion，respectively. The blue/red dual color up-conversion emission from this kind of phosphor may have applications in bio-imaging and optogenetics.
关键词： nepheline,LTA zeolite,zeolite derivatives,up-conversion emission
更新于2025-09-10 09:29:36
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Operando UV-Raman study of the methanol to olefins reaction over SAPO-34: spatiotemporal evolution monitored by different reactor approaches
摘要： A molecular understanding of coke formation during the methanol to olefins (MTO) reaction is of great importance in order to adopt strategies that can improve the lifetime of the catalyst. UV-Raman has proven to be a valuable characterization tool, because of the favorable resonance conditions achieved towards key coke components, e.g. aromatic and olefinic compounds. Still, the applicability of UV-Raman in MTO is limited by the high risk of inducing sample damage under the exposure to the intense UV excitation laser. This drawback has been addressed by specific experimental setups, exploiting the concept of sample movement under the laser beam during the measurement, so that the laser-sample interaction is minimized by averaging over a wider sample surface. In this work, the impact of two different experimental setups, both relying on sample movement, are evaluated for the operando investigation of the MTO reaction over a SAPO-34. While in one case the whole catalytic bed is moved (fluidized bed), in the other case the sample is pressed into a pellet and rotated. Due to the peculiar spatial evolution of the reaction zone during MTO in a fixed-bed reactor, each method provides valuable information, but at very different spatiotemporal scales.
关键词： Raman,Zeolite,Methanol-to-hydrocarbons,Deactivation,Operando
更新于2025-09-10 09:29:36
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Highly efficient photocatalytic reduction of CO2 on surface-modified Ti-MCM-41 zeolite
摘要： Three dimensional microporous zeolites have attracted much attention in catalysis because of their large BET surface area and abundant pores. Herein, Ti-MCM-41 zeolites with different molar ratio of Si/Ti were synthesized, and the surface acidity and active sites were adjusted by the modification of basic-earth metal oxides, and noble metal nanoparticles. The photocatalytic activity and selectivity were evaluated by the reduction of CO2 to CH4 and CO. The results indicated that the efficiency and selectivity of CO2 photoreduction to CH4 of Ti-MCM-41 zeolites were 93 ppm·g-1·h-1 and 29% in the ratio Si/Ti=10 under keeping the zeolite structure, and which is much higher than that of P25 with the value of 24 ppm·g-1·h-1 and 23%. When the surface of Ti-MCM-41 zeolites was modified by different basic-earth metal oxides, the photo-reduction activity of CO2 to CH4 increased about 1.5 times with MgO modification, and the selectivity of CO2 to CH4 improved to 42%. Moreover, the photoactivity and selectivity enhanced to 8835 ppm·g-1·h-1 and 93% when the surface was further decorated by Pt nanoparticles, while the selectivity of CO2 to CO reached 94% when Pd was loaded. Our work reveal reasonably that adjusting the acidity and active site of the microporous zeolites is a highly efficient way to improve the photocatalytic efficiency of CO2 reduction.
关键词： Ti-MCM-41 zeolite,active sites,surface acidity,CO2 photoreduction
更新于2025-09-09 09:28:46
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Planar Microstrip Ring Resonator Structure for Gas Sensing and Humidity Sensing Purposes
摘要： A planar microstrip ring resonator structure on alumina was developed. It was covered with a zeolite film. The device was successfully operated at around 8.5 GHz at room temperature as a humidity sensor. In the next step, an additional planar heater will be included on the reverse side of the resonator structure to allow for testing of gas sensitive materials under sensor conditions.
关键词： zeolite in operando spectroscopy,radio frequency gas sensing (RF),microwave sensors
更新于2025-09-09 09:28:46
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Cyclic Microwave-Assisted Metathetic Synthesis and Characterization of Ag-SrWO4/Zeolite Composites
摘要： Silver incorporated SrWO4/zeolite (Ag-SrWO4/zeolite) composites were successfully synthesized by a cyclic microwave-assisted metathetic route followed by heat treatment. The crystallized Ag-SrWO4/zeolite composites were formed at 600 oC for 3 h, showing a well immobilized morphology with particle sizes of 3-5 μm. The synthesized Ag-SrWO4/zeolite composites were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The optical properties were examined using photoluminescence emission and Raman spectroscopy.
关键词： Cyclic microwave-assisted metathetic synthesis,Ag-SrWO4/zeolite composite,Raman spectroscopy,Photoluminescence
更新于2025-09-09 09:28:46
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TiO <sub/>2</sub> /zeolite Bifunctional (Photo)catalysts for a Selective Conversion of Methanol to Dimethoxymethane: On the Role of Br?nsted Acidity
摘要： In the present work, we report the first example of one-step selective methanol photooxidation to dimethoxymethane (DMM) at room temperature over TiO2/zeolite bifunctional catalysts. The effects of the porosity, basicity/acidity of the zeolites on the selectivity of the reaction are discussed. The role of TiO2 active sites and zeolitic Br?nsted acid sites on the DMM production is reported. As the photocatalytic reaction occurs at room temperature, the influence of the reaction temperature is also investigated to extrapolate the results to thermal catalysis. This study demonstrates a clear synergetic effect of the zeolites on the selectivity of the reaction. They can display an important impact on the selectivity of the photocatalytic reaction even at a low temperature (e.g. room temperature). Based on the obtained results, the reaction mechanism of methanol conversion to DMM is elucidated.
关键词： Br?nsted acidity,dimethoxymethane (DMM),selective conversion,methanol photooxidation,TiO2/zeolite bifunctional catalysts
更新于2025-09-09 09:28:46
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Preparation and Characterization of Zeolite/TiO2 Cement-Based Composites with Excellent Photocatalytic Performance
摘要： A zeolite/TiO2 composite (ZTC) was applied to prepare a high-quality photocatalytic cement-based material (PCM). The acetone degradation experiment and micro measurements including XRD(X-Ray Diffractometer), SEM-EDS(Scanning Electron Microscope-Energy Dispersive Spectrometer), BET(BET Speci?c Surface Area Tester), FTIR(Fourier Transform Infrared Spectrometer) were conducted to characterize the photocatalytic ef?ciency and physicochemical properties of PCM, respectively. Results show that TiO2 particles disperse on the surface of a PCM homogeneously and provide abundant active sites for photocatalytic reactions. Compared to a normal photocatalytic cement-based material (NPCM), the TiO2 content of a PCM is lower and its photocatalytic ef?ciency is higher. The ZTC frees TiO2 particles from the impacts of cement hydration products and increases the adsorption volume of acetone. The photocatalytic performance of the PCM was stable after repeated tests. Using the ZTC as a photocatalyst has a prominent effect on the photocatalytic performance of the PCM.
关键词： photocatalytic cement-based material,photocatalytic ef?ciency,Zeolite/TiO2 composite
更新于2025-09-04 15:30:14
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Photodegradation of Methyl Orange Over CdS–TiO2/L-zeolite Composite Photocatalyst
摘要： A stable and active composite photocatalyst CdS–TiO2/L-zeolite has been synthesized through sol–gel method. The composite photocatalyst exhibits enhanced light harvesting in visible region indicating the improved photoresponsive ability because of CdS dopant. Photocatalytic conditions, such as the doping quantity of CdS, the concentration of photocatalyst, initial pH values and concentrations of methyl orange solutions have been systematically studied to obtain the highest photocatalytic efficiency. Photocatalytic kinetics of the composite photocatalyst is proved to conform to the first-order equation. The mechanism of the photocatalytic process is proposed in this work. L-zeolite support and CdS dopant could prevent the undesired electron/hole recombination and promote charge separation aiding for the continuous generation of active radicals. The novel composite photocatalyst shows good promise for applications in degrading environmental pollutants.
关键词： TiO2,Composite photocatalyst,Stability,CdS doping,L-zeolite
更新于2025-09-04 15:30:14
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Structure and luminescence of extraframework TiCl62? in Cs+-containing zeolite LTA
摘要： 2? ions were introduced into zeolite LTA at extraframework positions by allowing TiCl4(g) to react with Octahedral TiCl6 dehydrated Cs,Na-A. The structure of the product, Ti,Cl,Cs,Na-A, was determined by single-crystal crystallographic technique in the space group Pm?3m (a = 12.228(1) ?) and refined to the error index R1 = 0.046. Its composition was confirmed 2? ion is stabilized by by energy-dispersive X-ray analysis. Octahedral TiCl6 6+ cluster. Each of these Cl? ions bonds further to an 8-ring Cs+ ion. These eight surrounding Cs+ ions to form a Cs8TiCl6 9+ continuum in the surface volume 2? ions of adjacent unit cells to form a Cs11TiCl6 8-ring Cs+ ions bridge between TiCl6 of the crystal. The X-ray induced luminescence spectrum of the product is a broad band from 360 to 700 nm, peaking at 475 nm. The emission is red-shifted and less intense than those of M,Cl,Cs,Na-A, M = Zr and Hf, but appears to occur by the same self-trapped exciton (STE) mechanism. 2? ions center 8% of the large cavities. The TiCl6
关键词： Vapor-phase reaction,Luminescence,TiCl6 2?,Zeolite A,Crystal structure,Extraframework Ti4+
更新于2025-09-04 15:30:14
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Ethiopian natural zeolites for photocatalysis
摘要： The combination of zeolites and photochemistry has recently shown excellent results due to the special structure of the zeolites that helps a better use of the solar energy improving the selectivity of the chemical reactions carried out. There are several reports on the preparation of TiO2 confined nanoparticles in synthetic zeolites. However, very few reports are found on the use of natural zeolites. Zeolites are a vast natural resource in Ethiopia that remains unexploited. Their microporous structure can accommodate a wide variety of cations such as sodium, potassium and magnesium among others. The main objective of our work was to test the potential use of the naturally occurring zeolites, with high content in titanium, as photocatalysts. The samples have been characterized by X-ray diffraction (XRD), chemical analysis (ICP-OES), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV-Vis) and photocatalytic activities of the samples were tested in photocatalytic degradation of methyl orange (MO).
关键词： Natural zeolite,Photocatalysis,Methyl orange,Band gap energy,TiO2 loading
更新于2025-09-04 15:30:14