Structural changes in nanostructured catalytic oxides monitored by Raman spectroscopy: Effect of the laser heating

Silva, Antonio N. da; L., Jose Alves; Freire, Paulo; Oliveira, Alcinéia C.; Filho, J. Mendes

doi:10.1016/j.jpcs.2016.11.005

Cited by 10 publications

(11 citation statements)

References 45 publications

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“…The phonon softening and phonon bandwidth were calculated using a model which considers the three-and four-phonon anharmonic processes. Note that an increase in the laser power leads to the same spectral evolutions by heating effect [36]. Furthermore, a reversible cubic (Fm-3m) to tetragonal (P42/nmc) phase transition was reported for nanosized (5-18 nm) ceria decreasing the temperature from 75 to -25 °C while the lattice parameter was increased [37].…”

Section: Nanocrystalline Ceomentioning

confidence: 80%

Raman spectroscopy as a powerful tool to characterize ceria-based catalysts

2021

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A review. CeO 2 is widely used and investigated as an oxide catalyst or support due to its unique redox property of oxygen storage and release. In this paper, the different opportunities offered by Raman spectroscopy for advanced characterization of ceria-based catalysts are reviewed: spectral modifications induced by nanocrystallinity, defects, doping and reduction, identification of supported molecular species, isolated atoms and nanoclusters, characterization of surface modes, hydroxyl groups, reaction intermediates such as peroxo and superoxo species. Finally, in situ/operando studies for environmental catalysis are summarized illustrating Raman spectroscopy as a powerful tool to characterize ceria-based catalysts.

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Section: Nanocrystalline Ceomentioning

confidence: 80%

Raman spectroscopy as a powerful tool to characterize ceria-based catalysts

2021

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“…Specifically, the Si-O stretching and Si-O-Si stretching absorption peaks of pure Laponite at 1,012 and 657 cm 21 shifted to 1,004, 641 cm 21 in the spectrum of the PAAm/ Laponite and 1,004, 648 cm 21 in PAAm/Laponite/TiO 2 , which suggested hydrogen bonding between PAAm and Laponite. The bands at 1,086 cm 21 ascribed to the TiO 2 network and 549 cm 21 associated with the characteristic vibrational mode of Ti-O-Ti bonds [23] shifted to lower wavenumber of 1,035 cm 21 and 478 cm 21 in the spectrum of PAAm/TiO 2 , and 1,070, 534 cm 21 in PAAm/ Laponite/TiO 2 , attributed to the presence of hydrogen bonding between PAAm chains and TiO 2 . Raman spectroscopy demonstrated the interaction between TiO 2 nanoparticle and Laponite (Fig.…”

Section: Interaction Between Laponite and Tiomentioning

confidence: 97%

Tuning morphology and mechanical property of polyacrylamide/Laponite/titania dual nanocomposite hydrogels by titania

Wang

Tan²,

et al. 2018

Polymer Composites

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The tough polyacrylamide/Laponite/titania (TiO 2 ) dual nanocomposite (NC) hydrogel was fabricated by in situ radical polymerization of acrylamide (AAm) in the dispersion of Laponite and TiO 2 . TiO 2 nanoparticles were prepared by sol-gel method and used as both the inorganic filler and multi-functional crosslinking agent. The morphology of hydrogel was tuned as functions of the sodium hydroxide (NaOH) concentration and the ratio of Ti (mmol) to clay (g) (mmol Ti/g clay). SEM and HR-TEM morphologies revealed that Laponite and TiO 2 tended to form a uniform and regular microstructure like peasecod in poly(acrylamide) (PAAm) matrix due to the synergistic effect between electrostatic interaction and covalent interaction when the concentration of NaOH used in TiO 2 hydrosol increased to 1 3 10 21 mol/L. This homogeneous microstructure enhanced mechanical properties of hydrogel. The compression strength, modulus and fracture energy reached 2,107 kPa, 247 kPa, and 1,837 J/m 2 , respectively. The gels exhibited excellent fatigue resistance and good UV protective performance. It might have potential application in optical materials, wound dressing materials and tissue engineering scaffolds. POLYM. COMPOS., 00:000-000, 2018.

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“…1122 and 1339 cm −1 indicates the existence of hematite, as found elsewhere [9] and consistent with the XRD results. Also, Raman modes at about 953,1104 and 1217 cm −1 are due to O-H vacancies [15].…”

Section: Physicochemical Features Of Mnfesi Compositementioning

confidence: 99%