Temperature-induced phase transition in h-MoO3: Stability loss mechanism uncovered by Raman spectroscopy and DFT calculations

Moura, João Victor Barbosa; Silveira, J. V.; Filho, J.G. da Silva; Filho, A. G. Souza; Luz-Lima, C.; Freire, Paulo

doi:10.1016/j.vibspec.2018.07.008

Cited by 42 publications

(28 citation statements)

References 38 publications

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“…However, the relative peak intensities reveal that the {100} plane family is more intense when compared to the standard ICSD card, suggesting an anisotropic crystalline growth of the h-MoO3 phase [10,19]. Raman active modes identified in Figure 1b confirm the metastable hexagonal phase of MoO3 [29]. The bands located at 985-974 cm −1 and 912-880 cm −1 are assigned to the symmetrical and asymmetrical stretching modes, respectively, of the Mo=O double bond.…”

Section: Resultsmentioning

confidence: 92%

“…The bands located at 985-974 cm −1 and 912-880 cm −1 are assigned to the symmetrical and asymmetrical stretching modes, respectively, of the Mo=O double bond. The several bands appearing between 550-200 cm −1 are mainly related to the Mo-O-Mo vibrations (rocking and scissoring), while the modes below 200 cm −1 are associated to the MoO 6 octahedral vibrations in the h-MoO 3 phase [29].…”

Section: Resultsmentioning

confidence: 99%

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Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

2020

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Hexagonal molybdenum trioxide (h-MoO3) was synthesized by microwave-assisted hydrothermal method, allowing an ultrafast growth of unidimensional microrods with well-faceted morphology. The crystalline structure of this metastable phase was confirmed by X-ray diffraction (XRD) and Raman spectroscopy. Scanning electron microscopy (SEM) showed that hexagonal microrods can be obtained in one minute with well-defined exposed facets and the fine control of morphology. Sensing tests of the acetone biomarker revealed that the h-MoO3 microrods exhibit, at low ppm level, good sensor signal, fast response/recovery times, selectivity to different interferent gases, and a lower detection limit of 400 ppb.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

2020

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“…Figure 4 illustrates the Raman (Figure 4A) and FTIR (Figure 4B) vibrational spectra of MoO 3 catalysts synthesized in this work. The attributions observed in the Raman spectra (Figure 4A) were based on those described in the literature 41‐44 . The vibrational modes that appeared around 600 to 1000 cm −1 correspond to the stretching vibrations of the MoO 6 octahedron, and the modes between 200 and 400 cm −1 originate from the bending vibrations of the MoO 6 octahedron, while the modes below 200 cm −1 are assigned to lattice deformation the MoO 6 octahedron modes 41,44 .…”

Section: Resultsmentioning

confidence: 53%

“…The attributions observed in the Raman spectra (Figure 4A) were based on those described in the literature. [41][42][43][44] The vibrational modes that appeared around 600 to 1000 cm À1 correspond to the stretching vibrations of the MoO 6 octahedron, and the modes between 200 and 400 cm À1 originate from the bending vibrations of the MoO 6 octahedron, while the modes below 200 cm À1 are assigned to lattice deformation the MoO 6 octahedron modes. 41,44 The bands observed in the 968 to 884 cm À1 range, seen as a differential in the h/α-MoO 3 sample, possibly corresponding to the elastic vibrations of the MoO 6 octahedron in the MoO 3 hexagonal crystal structure, corroborating the studies by Lopez et al 44 Such behavior was also mentioned by Zhang et al, 43 confirming the XRD results (Figure 2B), which indicated that two crystalline phases form the catalyst.…”

Section: Characterization Of Catalysts Synthesized By Combustion Reac...mentioning

confidence: 99%

Synthesis of MoO ₃ by pilot‐scale combustion reaction and evaluation in biodiesel production from residual oil

Silva

Farias

Melo

et al. 2022

Intl J of Energy Research

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Summary The MoO3 was synthesized on a pilot scale by combustion reaction and their catalytic performance was investigated to obtain biodiesel from residual oil by simultaneous reactions of transesterification and esterification (TES). The catalyst was characterized by X‐ray diffraction with respective Rietveld refinement, Fourier transform infrared, and RAMAN spectroscopies, scanning electron microscopy, determination of the specific surface area by the method of N2 adsorption (Brunauer, Emmett, and Teller), and acidity test by temperature‐programmed desorption of ammonia molecule. The catalytic properties were evaluated through catalytic tests while the products of the TES reactions were characterized by gas chromatography, kinematic viscosity, and acidity index. Such results indicated that single‐phase catalysts (α‐MoO3‐100%) and biphasic (h/α‐MoO3‐hexagonal 56.80% and orthorhombic 43.20%) were synthesized, which presented crystalline fraction and crystal size of 88% to 90% and 33 to 84 nm, respectively. The crystalline phases (α‐MoO3 and h/α‐MoO3) showed typical morphologies of microplate agglomerates, irregular rods, the surface area of 1.5 to 4.7 m2 g−1, and total acidity equivalent to 30 to 84 μmol g−1 NH3. The MoO3 was successfully synthesized by pilot‐scale combustion reaction and showed promising results, with high conversions to ethyl esters (between 93% and 99%), maintaining activity (useful life) after five consecutive reuse cycles. Thus, the catalysts studied have the potential to enable positive impacts on the environment and society in general.

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“…Another method is the addition of a metal oxide injection layer such as MoO 3 , which can reduce the contact resistance of both BCBG and TCBG devices of several p-type organic semiconductors. − MoO 3 has a high phase transition temperature and thus is much more suitable than thiol SAMs for high-temperature applications. BCBG devices of IID-C1 with an MoO x (5 nm)/Au (25 nm) electrode, patterned by vacuum evaporation on top of OTS-modified SiO 2 substrates, were fabricated.…”

Section: Resultsmentioning

confidence: 99%

Contact Effect in High-Temperature Conjugated Polymer Transistors

Tran

Luo

Mei

2020

ACS Appl. Electron. Mater.

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Organic field-effect transistors (OFETs) are usually unstable at high temperature (above 150 °C), reportedly due to the disrupting charge transport pathways in the channel. Here, we demonstrate that the charge injection process at the contact region, which is rarely discussed, also could be the reason for the instability of OFETs at high temperature. Two common device structures, top-contact-bottom-gate (TCBG) and bottom-contactbottom-gate (BCBG), of an isoindigo-based polymer (IID-C1) are used for comparison. Their temperature-dependent in situ OFET characterization and contact resistance measurements show the vastly superior thermal stability of TCBG devices. While the TCBG structure has small and relatively stable contact resistance (R C ) across the scanned temperature, BCBG devices' contact region degrades significantly and raises the R C dramatically at 180 °C. For mitigating such effects, a thin layer of MoO 3 is added under the Au electrode to improve the charge injection, thus helping the BCBG devices function stably at up to 220 °C. This study emphasizes the significance of contact resistance and device architecture on fabricating high-temperature organic electronic devices and providing an insight into the charge transport in conjugated polymers at elevated temperature.

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Temperature-induced phase transition in h-MoO3: Stability loss mechanism uncovered by Raman spectroscopy and DFT calculations

Cited by 42 publications

References 38 publications

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

Synthesis of MoO ₃ by pilot‐scale combustion reaction and evaluation in biodiesel production from residual oil

Contact Effect in High-Temperature Conjugated Polymer Transistors

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Temperature-induced phase transition in h-MoO3: Stability loss mechanism uncovered by Raman spectroscopy and DFT calculations

Cited by 42 publications

References 38 publications

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

Ultrafast Growth of h-MoO3 Microrods and Its Acetone Sensing Performance

Synthesis of MoO 3 by pilot‐scale combustion reaction and evaluation in biodiesel production from residual oil

Contact Effect in High-Temperature Conjugated Polymer Transistors

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Product

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Synthesis of MoO ₃ by pilot‐scale combustion reaction and evaluation in biodiesel production from residual oil