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Hybridizing engineering strategy of non-lacunary (nBu4N)4W10O32 by carbon quantum dot with remarkably enhanced visible-light-catalytic oxidation performance
摘要： This paper discloses an e?cient strategy for the preparation of carbon quantum dot (CQD)- hybridized (nBu4N)4W10O32 (TBADT). A key step in this strategy is to hydrothermally treat CQD with TBABr solution to form the TBA+ micelle-encapsulated CQD, which acts as a cationized hybridizer to combine with the W10O32 anion to yield the target catalyst. XPS, UV–vis, PL and CV characterizations indicated that CQD hybridizer plays unique roles in improving the structural stability, redox capacity and visible light response of TBADT, especially in enhancing the stability of its photo-excited state. In the visible light-triggered selective oxidation of cyclohexane, toluene, ethylbenzene and benzyl alcohol with dioxygens in acetonitrile, the optimized hybrid containing 3% CQD shows much higher photo-catalytic activity than pure TBADT, a?ording ca. 21.7% conversion and 84.8% cyclohexanone selectivity in cyclohexane photo-oxidation, Additionally, the additive 2 M HCl further enhances the above hybridization e?ects, thereby signi?cantly promoting the current photo-catalytic oxidations.
关键词： Selective oxidation of organic compounds,Hybridizing molecular engineering,Decatungstates,Molecular oxygen,Carbon quantum dot,Visible-light-catalysis
更新于2025-09-12 10:27:22
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Decoration of plasmonic Mg nanoparticles by partial galvanic replacement
摘要： Plasmonic structures have attracted much interest in science and engineering disciplines, exploring a myriad of potential applications owing to their strong light-matter interactions. Recently, the plasmonic concentration of energy in subwavelength volumes has been used to initiate chemical reactions, for instance by combining plasmonic materials with catalytic metals. In this work, we demonstrate that plasmonic nanoparticles of earth-abundant Mg can undergo galvanic replacement in a nonaqueous solvent to produce decorated structures. This method yields bimetallic architectures where partially oxidized 200–300 nm Mg nanoplates and nanorods support many smaller Au, Ag, Pd, or Fe nanoparticles, with potential for a stepwise process introducing multiple decoration compositions on a single Mg particle. We investigated this mechanism by electron-beam imaging and local composition mapping with energy-dispersive X-ray spectroscopy as well as, at the ensemble level, by inductively coupled plasma mass spectrometry. High-resolution scanning transmission electron microscopy further supported the bimetallic nature of the particles and provided details of the interface geometry, which includes a Mg oxide separation layer between Mg and the other metal. Depending on the composition of the metallic decorations, strong plasmonic optical signals characteristic of plasmon resonances were observed in the bulk with ultraviolet-visible spectrometry and at the single particle level with darkfield scattering. These novel bimetallic and multimetallic designs open up an exciting array of applications where one or multiple plasmonic structures could interact in the near-field of earth-abundant Mg and couple with catalytic nanoparticles for applications in sensing and plasmon-assisted catalysis.
关键词： galvanic replacement,sensing,plasmon-assisted catalysis,plasmonic,Mg nanoparticles,multimetallic,bimetallic
更新于2025-09-12 10:27:22
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Synthesis of plasmonic gold nanoparticles supported on morphology-controlled TiO2 for aerobic alcohol oxidation
摘要： In the present research study, we report the synthesis of nano-sized gold (Au) particles immobilized on TiO2 support material. The morphologies of TiO2 support material was tailored and tuned to be rod, tube and microporous materials. The effect of plasmonic gold nanoparticles (NPs) deposited on different morphologies of TiO2 was studied. The prepared catalysts were characterized by various characterization techniques in order to have a detailed insight on the textural properties, morphology and electronic state of the material via UV–vis spectroscopy, N2 physisorption analysis, Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). We tested the controlled oxidation of benzyl alcohol to benzaldehyde using molecular oxygen at 373 K under atmospheric pressure. The results obtained from the thermal reaction conditions were compared with those performed under visible light irradiation (λ > 420 nm) at 373 K. Among all, Au/TiO2 nanorod catalyst displayed the superior performance of 33% yield in the absence of light and 55% yield of benzaldehyde with an external quantum efficiency of 3.4% under visible light irradiation (λ ≥ 420 nm) at 373 K for 4 h. The enhanced catalytic performances were attributed to the Au-LSPR phenomenon and a plausible reaction pathway has been discussed involving the generation of hot electrons during the course of reaction.
关键词： TiO2,Plasmonic catalysis and controlled oxidation,Gold nanoparticles
更新于2025-09-12 10:27:22
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Colloidally Stable CdS Quantum Dots in Water with Electrostatically Stabilized Weak‐Binding, Sulfur‐Free Ligands
摘要： Colloidal quantum dot (QD) photocatalysts have the electrochemical and optical properties to be highly effective for a range of redox reactions. QDs are proven photo-redox catalysts for a variety of reactions in organic solvents but are less prominent for aqueous reactions. Aqueous QD photocatalysts require hydrophilic ligand shells that provide long-term colloidal stability but are not so tight-binding as to prevent catalytic substrates from accessing the QD surface. Common thiolate ligands, which also poison many co-catalysts and undergo photo-oxidative desorption, are therefore often not an option. This paper describes a framework for the design of water-solubilizing ligands that are in dynamic exchange on and off the QD surface, but still provide long-term colloidal stability to CdS QDs. The binding affinity and inter-ligand electrostatic interactions of a bifunctional ligand, aminoethyl phosphonic acid (AEP), are tuned with the pH of the dispersion. The key to colloidal stability is electrostatic stabilization of the monolayer. This work demonstrates a means of mimicking the stabilizing power of a thiolate-bound ligand with a zwitterionic tail group, but without the thiolate binding group.
关键词： catalysis,nanotechnology,ligand design,quantum dots,water chemistry
更新于2025-09-11 14:15:04
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TEM Sample Preparation of Patterned Quantum Dots
摘要： Electrochemistry and heterogeneous catalysis continue to attract enormous interest. In situ surface analysis is a dynamic research field capable of elucidating the catalytic mechanisms of reaction processes. Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) is a non-destructive technique that has been cumulatively used to probe and analyze catalytic-reaction processes, providing important spectral evidence about reaction intermediates produced on catalyst surfaces. In this perspective, we review recent electrochemical- and heterogeneous-catalysis studies using SHINERS, highlight its advantages, summarize the flaws and prospects for improving the SHINERS technique, and give insight into its future research directions.
关键词： Catalytic mechanisms,In situ surface analysis,SHINERS,Heterogeneous catalysis,Reaction intermediates,Electrochemistry,Shell-isolated nanoparticle-enhanced Raman spectroscopy
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Nanoparticle Structure and Dynamics Studied Using Controlled Atmosphere Transmission Electron Microscopy
摘要： Nanoparticle and catalysis research makes extensive use of transmission electron microscopy (TEM). In particular, environmental transmission electron microscopy (ETEM) has attracted considerable attention in recent years. This technique allows us to expose samples to gaseous environments at elevated temperatures in order to investigate local structural changes at the atomic level as the environment changes. Recently, the technique has also been used in nanowire, graphene and electron optical lithography research among others. Recent developments in TEM instrumentation include monochromation of the electron source and aberration correction of both condenser and objective lenses. These developments have now been introduced onto the ETEM column. The improved spatial resolution and interpretability provided by these additions are beneficial for imaging the surface structure and dynamics of catalyst nanoparticles and provides exciting new possibilities for investigating chemical reactions. In order to take full advantage of this, an understanding of both the interaction of fast electrons with gas molecules and the effect of the presence of gas on high-resolution imaging is necessary. Using an FEI Titan ETEM equipped with a monochromator and an aberration corrector on the objective lens, we have investigated sintering of supported metal nanoparticles often used in catalysis. A model system consisting of supported gold nanoparticles were prepared by sputter-depositing the metal onto graphene and boron nitride substrates. These samples were imaged under hydrogen at increasing temperatures. Gas was introduced into the environmental cell using digitally controlled mass flow controllers providing accurate and stable control of the pressure in the cell. As the temperature was increased, migrating particles were observed on the support. As they came into contact, a neck was formed between the particles and subsequently, the particles coalesced entirely (Fig. 1). Growth patterns have also been investigated for platinum and palladium nanoparticles supported on silicon oxide substrates. Here, anomalously large particles were observed as the particles were sintered in oxygen atmospheres at temperatures at elevated temparatures. Such large particles have also been observed for industrial catalysts. In this study, we will try to elucidate the mechanisms of metal nanoparticle sintering. The analytical capabilities of the microscope can be further augmented by adding stimuli such as optical or electrical though the sample holder. Using a holder capable of exposing the sample to light, the redox properties of cuprous oxide have been investigated. Cuprous oxide has been identified as an active catalyst for the water splitting and hydrogen evolution from an ethanol solution. However, Cu2O suffers from photocorrosion. This phenomenon was investigated using controlled atmosphere transmission electron microscopy. Fig. 2 shows how the photoinduced degradation of cuprous oxide to metallic copper under an aqueous atmosphere using bright-field imaging, electron diffraction and electron energy-loss spectroscopy. All three techniques show the transformation from oxide to metal. Effects of imaging in various elemental as well as di-molecular gases and their effect on imaging and spectroscopy in the environmental transmission electron microscope will also be discussed.
关键词： Dynamics,ETEM,Nanoparticles,Morphology,Catalysis
更新于2025-09-11 14:15:04
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Hybrid 0D/2D Ni2P quantum dot loaded TiO2(B) nanosheet photothermal catalysts for enhanced hydrogen evolution
摘要： The development of low cost, stable, robust photocatalysts to convert solar energy into hydrogen energy is an important challenge. Here, we describe a simple solvothermal method to successfully fabricate a catalyst with a hybrid 0D/2D Ni2P quantum dot/TiO2(B) nanosheet architecture. HRTEM shows that Ni2P quantum dots about 5 nm in size were dispersed on ultrathin TiO2(B) nanosheets. The optimum photocatalytic H2 evolution rate with 10 wt% Ni2P/TiO2(B) (3.966 mmol g?1 h?1), which was 15 times higher than pure TiO2(B) nanosheets. Significantly, the new catalyst shows high stability and reusability in multiply cycled H2 production runs for a 30 h period. The H2 production rate can be considerably increased furthered by using synergistic photothermal H2 evolution (20.129 mmol g?1 h?1 at 90 °C).
关键词： TiO2(B) nanosheets,Photocatalytic H2 evolution,Ni2P quantum dots,0D/2D architecture,Synergistic photothermal catalysis
更新于2025-09-11 14:15:04
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The chemical potential of plasmonic excitations
摘要： By the photoexcitation of localized surface plasmon resonances of metal nanoparticles, one can generate reaction equivalents for driving redox reactions. We show that, in such cases, there is a chemical potential contributed by the plasmonic excitation. This chemical potential is a function of the concentration of light, as we determine from the light intensity-dependent activity in plasmon-excitation-driven CO2 reduction on Au nanoparticles. Our finding allows the treatment of plasmonic excitation as a reagent in chemical reactions; the chemical potential of this reagent is tunable by the light intensity.
关键词： hot electron,catalysis,CO2 reduction,photocatalysis,LSPR
更新于2025-09-11 14:15:04
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Preparation and Characterization of Water-soluble ZnSe: Fe/ZnSe Quantum Dots
摘要： A chiral phosphoric acid-catalyzed kinetic resolution and desymmetrization of para-quinols operating via oxa-Michael addition was developed and subsequently subjected to mechanistic study. Good to excellent s-factors/enantioselectivities were obtained over a broad range of substrates. Kinetic studies were performed, and DFT studies favor a hydrogen bonding activation mode. The mechanistic studies provide insights to previously reported chiral anion phase transfer reactions involving chiral phosphate catalysts in combination with boronic acids.
关键词： directed reactivity,oxa-Michael addition,kinetics,asymmetric catalysis,chiral phosphoric acid,reaction mechanisms
更新于2025-09-11 14:15:04
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[IEEE 2019 28th Wireless and Optical Communications Conference (WOCC) - Beijing, China (2019.5.9-2019.5.10)] 2019 28th Wireless and Optical Communications Conference (WOCC) - Crosstalk Prediction of Cables Based on Cosserat Elastic Rod Theory
摘要： A rhodium(III)-catalyzed domino annulation of simple olefins with diazo oxindoles to give spirooxindole pyrrolone products is described. This reaction can be formally viewed as the result of an anomalous tandem C(cid:2)H activation, carbene insertion, Lossen rearrangement, and a nucleophilic addition process. The potential utility of this reaction was further demonstrated by the late-stage diversification of drug molecules.
关键词： Lossen rearrangement,olefins,rhodium catalysis,oxindoles,C(cid:2)H activation
更新于2025-09-11 14:15:04