Synthesis and Morphology Control of AM‐6 Nanofibers with Tailored ‐V‐O‐V‐ Intermediates

Guo, Meiling; Feng, Zhaochi; Hofmann, Jan P.; Weckhuysen, Bert M.; Fan, Fengtao; Li, Can

doi:10.1002/chem.201301812

Cited by 5 publications

(4 citation statements)

References 36 publications

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“…The reduction of 4-nitrophenol to 4-aminophenol with NaBH 4 is known to be catalyzed by silver nanopartilces and shows a strong size-dependent effect, with smaller Ag nanoparticles exhibiting higher rate constants. − Figure shows that the apparent rate constant is maximum for the 2 h sample. The lower apparent rate constant with the sample beyond 2 h is due to increasing size of silver particles (dissociated from the zeolite and mostly in the bulk).…”

Section: Discussionmentioning

confidence: 95%

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Evolution of Silver Nanoparticles within an Aqueous Dispersion of Nanosized Zeolite Y: Mechanism and Applications

Severance

Dutta

2014

J. Phys. Chem. C

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Stable aqueous dispersion of silver ion-exchanged nanozeolite Y was reacted with the three common dihydroxyphenols, hydroquinone, catechol and resorcinol. With hydroquinone and catechol, there was rapid reduction of the intrazeolitic silver to form metallic silver with complete destruction of the zeolite framework. Resorcinol, the weakest reducing agent amongst the group behaved differently. The formation of metallic silver was considerably slower, and the zeolite framework was mostly intact. This made it possible to examine the evolution of silver cluster formation with optical spectroscopy and transmission electron microscopy. In the first 135 min of reaction, extinction/fluorescence spectroscopy indicates the formation of Ag n<4 and Ag n>4 clusters. The smaller clusters disappear more rapidly with time. For the 1 hr reduced sample, transmission electron microscopy showed uniform distribution of 1.4 nm Ag particles throughout the zeolite.After 2 hr of reduction, the average size of the particles was 2.5 nm, and a fraction of these particles appeared on the zeolite surface. With further time of reduction (3-24 hr), more of the intrazeolitic Ag migrated to the surface, and Ostwald ripening into larger nanoparticles (> 3 nm) was observed at the zeolite-solution interface. We propose that the slow growth of the silver prevented the destruction of the zeolite framework. Two factors are considered important for the slow growth of silver with resorcinol. First, resorcinol is a weak reducing agent. Second, and more importantly, the intrazeolitic pH drops upon initial silver reduction, as measured by an acidochromic dye, which raises the reduction potential of resorcinol, thereby arresting further reduction and particle growth. By removing the resorcinol at any stage of the reduction, stable Ag nanoparticles on nanozeolite samples can be isolated. Such samples were investigated as SERS substrates as well as a heterogeneous

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Section: Discussionmentioning

confidence: 95%

“…[61][62][63] Figure 9 shows that the apparent rate constant is maximum for the 2 hr sample. [61][62][63] Figure 9 shows that the apparent rate constant is maximum for the 2 hr sample.…”

Section: Properties Of Silver Loaded Zeolite As a Function Of Nanoparmentioning

confidence: 97%

Evolution of Silver Nanoparticles within an Aqueous Dispersion of Nanosized Zeolite Y: Mechanism and Applications

Severance

Dutta

2014

J. Phys. Chem. C

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“…Since the active centers in catalysis often possess the dimension feature of nanometer to atomic scale, imaging catalysts at working condition has attracted much attention nowadays [120,121]. As a powerful technique, Raman imaging has been used for the preparation and characterization of catalysts [122][123][124]. However, the spatial resolution is still too low owing to the diffraction limit.…”

Section: Uv Raman Spectroscopic Study On the Phase Transformation Of mentioning

confidence: 99%

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

et al. 2014

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UV Raman spectroscopy has been demonstrated to be a powerful technique in catalysis because it can avoid the fluorescence interference occurring in visible Raman spectroscopy and concurrently enhance the Raman scattering intensity owing to the short wavelength of the excitation laser and resonance Raman effect. This article briefly reviews the recent advances in the study on heterogeneous catalysis by UV Raman spectroscopy, including the identification of isolated transition metal ions in molecular sieves, in situ study of zeolite assembly mechanisms and catalytic reaction mechanisms, and the monitoring of the surface phase transformation of metal oxide photocatalysts. UV (resonance) Raman spectroscopy, with the power of resonance enhancement for Raman signal and the advantage of high sensitivity for surface structure, coupling with in situ methodology, can provide the information about the active sites/phase and their assembling mechanisms, which are helpful for the understanding of heterogeneous catalysis and the rational design of highly active and selective catalysts.

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“…Among them, vanadosilicate AM-6, isostructural with ETS-10, is a 3-D, 12-membered microporous zeo-type material, consisting of SiO 4 tetrahedra and VO 6 octahedra [9]. Unlike ETS-10, AM-6 has 1-D VO 3 2-quantum wires instead of TiO 3 2-with narrower band gap compared to titanosilicate ETS-10 (i.e., *3.8 vs. *4.3 eV, for AM-6 and ETS-10, respectively) [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Secondary growth of microporous vanadosilicate AM-6 films

2016

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Oriented vanadosilicate AM-6 thin films with an average thickness of 1-2 lm were prepared on the ITO coated glass substrates using secondary growth method with a partial a(b)-out-of-plane preferred crystal orientation for the first time. In secondary growth method, titanosilicate ETS-10 crystals were deposited on the substrate from a colloidal suspension to form seed layers. Then, the hydrothermal growth of the seed crystals was conducted to form AM-6 films. It was observed that the AM-6 films formed possess similar 1-D VO 3 2-quantum wires as also observed in powder AM-6 crystals. Afterward, the effect of reaction temperature and amount of water in the secondary growth gel on crystal morphology and a(b)-out-of-plane crystallographic preferred orientation (CPO) were investigated to gain a better understanding of the secondary growth mechanism of vanadosilicate AM-6 films. The results suggested that the increased amount of water leads to increased CPO in the AM-6 films, whereas an increase in reaction temperature from 503 to 528 K leads to more c-oriented AM-6 films with a decreased CPO value. Furthermore, an increase in the reaction temperature led to a decrease in the reaction time, resulting in the formation of quartz impurity. Accordingly, well intergrown a(b)-out-of-plane oriented vanadosilicate films were grown for the first time using ETS-10 seed crystals and it is believed that this work provides an effective pathway for controlling the synthesis of AM-6 films expanding the possible range of applications of these materials possessing 1-D quantum wires.

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Synthesis and Morphology Control of AM‐6 Nanofibers with Tailored ‐V‐O‐V‐ Intermediates

Cited by 5 publications

References 36 publications

Evolution of Silver Nanoparticles within an Aqueous Dispersion of Nanosized Zeolite Y: Mechanism and Applications

Evolution of Silver Nanoparticles within an Aqueous Dispersion of Nanosized Zeolite Y: Mechanism and Applications

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

Secondary growth of microporous vanadosilicate AM-6 films

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