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Formation and characterization of charge coupled structure of polyoxometalate particles and a GaAs-based nanowire for readout of molecular charge states
摘要： To investigate the molecular charge dynamics of polyoxometalate (POM) molecules, we formed and characterized a charge coupled structure with POM molecular particles and a GaAs-based nanowire. In our system, the charge sensitivity was locally increased by capacitive coupling between a metal tip and the POM particle. Surface dispersion of POM particles on the GaAs nanowire was carried out in a controlled manner by choosing an appropriate solvent and POM concentration. We found that, after POM surface dispersion, the current in the GaAs nanowire remarkably increased by charging the POM particles using a conductive atomic force microscopy tip. The current change strongly depended on humidity of the measurement environment. The nanowire current under capacitive coupling between the conductive tip and the POM particle on the nanowire surface showed steps with a height of approximately 70 nA, suggesting that multiple hole charging and discharging occurred in the particle in a synchronized manner.
关键词： conductive atomic force microscopy,GaAs-based nanowire,molecular charge states,charge coupled structure,polyoxometalate
更新于2025-09-11 14:15:04
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Study of Bi-directional detection for ascorbic acid and sodium nitrite based on Eu-containing luminescent polyoxometalate
摘要： Eu-containing polyoxometalate K13Eu(SiMoW10O39)2·28H2O (Eu-SiMoW) owns the stimu-chromic and photo-luminescence properties. An ingenious test of ascorbic acid (AA) and sodium nitrite (NaNO2) was carried out based on the dual properties of Eu-SiMoW in solutions. First, the redox reaction of Eu-SiMoW and AA generated the blue reduced Eu-SiMoW, accompanied by fluorescence quenching; then the redox reaction of the reduced Eu-SiMoW and NaNO2 made Eu-SiMoW back to its original pale yellow state with red luminescence. Accordingly, the content of AA and NaNO2 could be measured by the reversible change of color and luminescence of Eu-SiMoW. This bi-directional detection method is first discovered and proven to be a simple and effective method for the detection of AA and NaNO2. The proposed method exhibited a linear response range (LRR) from 0.1 to 0.9 mmol L?1 with a limit of detection (LOD) of 0.53 μmol L?1 in UV–vis spectra and 4.67 μmol L?1 in luminescence spectra for AA as well as a LRR from 0.05 to 0.4 mmol L?1 with a LOD of 1.16 μmol L?1 in UV–vis spectra and 5.39 μmol L?1 in luminescence spectra for NaNO2. Moreover, the fluorescence switching of Eu-SiMoW could be realized by reacting with reductant and oxidant through the redox reaction. The detection mechanism is considered as a fluorescence resonance energy transfer process between discolor component SiMoW and luminescence component Eu in Eu-SiMoW.
关键词： Ascorbic acid,Sodium nitrite,Bi-directional detection,Eu-polyoxometalate,Luminescence switching
更新于2025-09-10 09:29:36
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Interface Engineering of Hematite with Nacre-like Catalytic Multilayers for Solar Water Oxidation
摘要： An efficient water oxidation photoanode based on hematite has been designed and fabricated by tailored assembly of graphene oxide (GO) nanosheets and cobalt polyoxometalates (Co-POM) water oxidation catalysts into a nacre-like multilayer architecture on a hematite photoanode. The deposition of catalytic multilayers provides a high photocatalytic efficiency and photoelectrochemical stability to underlying hematite photoanodes. Compared to the bare counterpart, the catalytic multilayer electrode exhibits a significantly higher photocurrent density and large cathodic shift in onset potential (~ 369 mV) even at neutral pH conditions due to the improved charge transport and catalytic efficiency from the rational and precise assembly of GO and Co-POM. Unexpectedly, the polymeric base layer deposited prior to the catalytic multilayers improves the performance even more by facilitating the transfer of photogenerated holes for water oxidation through modification of the flat band potential of the underlying photoelectrode. This approach utilizing polymeric base and catalytic multilayers provides an insight into the design of highly efficient photoelectrodes and devices for artificial photosynthesis.
关键词： photocatalysis,graphene oxide,layer-by-layer assembly,artificial photosynthesis,polyoxometalate
更新于2025-09-10 09:29:36
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Preyssler-based nanocomposite as a magnetic photocatalyst: synthesis, characterisation and its photocatalytic activity for decolourisation of rhodamine B
摘要： In this work, the authors prepared a novel magnetic photocatalyst by grafting of Preyssler-type polyoxometalate, H14 [NaP5 W30 O110] onto Fe3O4 nanoparticles via an internal layer of silver nanoparticles. The obtained nanocomposite has been characterised by electron dispersive X-ray, transmission electron microscopy and scanning electron microscopy. The activity of the synthesised nanomagnetic photocatalyst was tested by the photocatalytic decolourisation of rhodamine B under UV light irradiation in the study’s designed reactor. It was found that, compared to pure Preyssler, decolourisation of rhodamine B was occurred four times faster using the synthesised magnetic nanocomposite with easy separation. The magnetic nanocatalyst was separated after ending the reaction and recycled. It just showed 2–3% decrease in catalytic activity after four recycling.
关键词： Preyssler-type polyoxometalate,Fe3O4 nanoparticles,photocatalytic decolourisation,rhodamine B,magnetic photocatalyst,silver nanoparticles
更新于2025-09-09 09:28:46
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Effect of substituting molybdenum atoms with tungsten on photocatalyst activity of cesium salt of keggin type polyoxometalates decorated magnetic ceria
摘要： Herein the potential use of cesium salts of polyoxometalate incorporated ceria and magnetic ceria as a photocatalyst for the photodegradation of Congo red was studied. Polyoxometalates salts (cesium salts of tungestophosphoric acid (H3PW12O40), molybdophosphoric acid (H3PMo12O40), and 6-molybdo tungestophosphoric acid (H3PW6Mo6O40)), having Keggin structure with large cations like Cs+, are porous materials. The morphological and structural studies of synthesized nanocomposites were carried out using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Results indicated that the Fe3O4@CeO2/Cs-PMoyW12-yO40 and CeO2/Cs-PMoyW12-yO40 (y=0, 6, 12) nanocomposites are successfully synthesized. UV-vis diffuse reflectance spectroscopy determined the absorption edge and band gap energies of the prepared nanocomposites as a direct semiconductor. All the obtained structures were applied as photocatalys for degradation of Congo red dye in aqueous solutions under visible light. The Fe3O4@CeO2/Cs-PMo6W6O40 photocatalyst exhibited the highest photocatalytic activity under visible light.
关键词： Photocatalyst,Ceria,Polyoxometalate,Congo red,Nanocomposite,Magnetic
更新于2025-09-04 15:30:14