An elevated concentration of MoS<sub>2</sub> lowers the efficacy of liquid-phase exfoliation and triggers the production of MoO<sub>x</sub> nanoparticles

Bodík, Michal; Annusova, Adriana; Hagara, Jakub; Mičušík, Matej; Omastová, Mária; Kotlár, Mário; Chlpík, Juraj; Cirák, J.; Švajdlenková, Helena; Anguš, Michal; Marín-Roldán, A.; Veis, P.; Jergel, M.; Majková, E.; Šiffalovič, Peter

doi:10.1039/c9cp01951k

Cited by 17 publications

(21 citation statements)

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“…After 50 min of laser treatment, the LSPR peaks vanish as the majority of the particles were transformed to MoO 3 nanobelts, as shown in the SEM (Figure 2d) and supported by the GIXRD pattern (Figure S1d) and Raman spectrum (Figure 3a). Additionally, the PL spectra (Figure S4a) show that the intensity of the PL peak at around 400 nm, which is attributable to MoO X , 14,32 increases with laser treatment time. The Tauc plot of the sample after 50 min of laser treatment is presented in Figure S4b.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Two-Dimensional Plasmonic Molybdenum Oxide Nanomaterials by Femtosecond Laser Irradiation

Chang

Ayub

et al. 2021

Chem. Mater.

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A novel process to synthesize plasmonic MoO3–X nanosheets is demonstrated, in which MoS2 powders suspended in ethanol/water are irradiated with pulses from a femtosecond laser, resulting in simultaneous Coulomb explosion, photoexfoliation, and oxidation. The oxidation process is found to start with the formation of hydrogen-bonded molybdenum oxide (H X MoO3), followed by the release of −OH2 groups to create oxygen vacancies, and finally, MoO3–X is oxidized to MoO3 after extended irradiation. The formation of H X MoO3 is the critical step to create enough oxygen vacancies for localized surface plasmon resonance (LSPR), and this step is attributed to H3 + dissociated from ethanol under femtosecond laser irradiation. It is found that 80–90% ethanol is the optimal concentration to synthesize plasmonic MoO3–X , where the balance of water facilitates the release of the −OH2 groups to create the required vacancies. It is shown that different organic solvents like methanol, 1-propanol, and isopropyl alcohol that were reported to generate large amounts of H3 + under femtosecond laser irradiation can also oxidize MoS2 into plasmonic MoO3–X . The LSPR properties of the synthesized MoO3–X are evaluated by UV–vis spectroscopy and photothermal conversion measurements. A photothermal conversion efficiency of 33% is observed under near-infrared irradiation, suggesting a potential application in photothermal cancer therapy.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Two-Dimensional Plasmonic Molybdenum Oxide Nanomaterials by Femtosecond Laser Irradiation

Chang

Ayub

et al. 2021

Chem. Mater.

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“…SoMs are not limited to MoS 2 but are found in all Group IV–VII LTMDs, indicating a general hydrolytic decomposition pathway. − Therefore, as-received powders, depending on storage conditions, contain a broad compositional and structural distribution of SoMs. Many research groups have reported − blue discolorations during sonication assisted exfoliation of MoS 2 (in NMP, H 2 O/surfactant) and recommended a pretreatment step to remove undefined “surface impurities” before LTMDs can enter the liquid phase. − Recent literature indicates that these impurities affect the colloidal stability of surfactant based exfoliation protocols due to their highly ionic character . To our knowledge, there have been no efforts to analyze these corrosion products.…”

Section: Results and Discussionmentioning

confidence: 99%

Mechanism for Redox Exfoliation of Layered Transition Metal Dichalcogenides

2020

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“…As for the subphase, we used acidic water. The pH value was lowered to 4 to decrease the solubility of the MoS 2 in the subphase , by adding 5 mL of HCl to 500 mL of UPW. The surface of the subphase was carefully cleaned with a suction pump before applying the colloidal solution of the FL MoS 2 flakes.…”

Section: Methodsmentioning

confidence: 99%

Collapse Mechanism in Few-Layer MoS₂Langmuir Films

et al. 2020

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Recent advances in the liquid-phase exfoliation enabled large-scale production of two-dimensional (2D) materials, including few-layer graphene and transition metal dichalcogenides. The exfoliated flakes of 2D materials allow cost-effective deposition of continuous films for various applications ranging from optoelectronics to lubrication technology. The self-assembly of 2D materials on water subphase and subsequent transfer of such a Langmuir film onto a solid substrate offers an unprecedented layer quality in terms of spatial homogeneity as it proceeds in thermodynamic equilibrium. However, while the formation of conventional organic molecular Langmuir films has been widely studied, the application of the Langmuir technique to rigid inorganic 2D materials is still rather unexplored.Here, we study the underlying mechanism behind the formation and collapse at the critical surface pressure of the Langmuir film composed of few-layer MoS 2 flakes. The in situ wide-angle X-ray scattering measured in real time and other supportive techniques applied ex situ after the film transfer onto a Si/SiO 2 substrate were employed. We identify all principal compression stages up to the Langmuir monolayer collapse and beyond, relying on the texture, surface pressure, and elastic modulus temporal evolution. The results obtained and the conclusions drawn can be extended to a large family of the inorganic Langmuir films of other 2D materials to optimize the deposition process for envisaged application.

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An elevated concentration of MoS₂ lowers the efficacy of liquid-phase exfoliation and triggers the production of MoO_x nanoparticles

Abstract: The oxidation of MoS2 with a simultaneous decrease of MoS2 content.

Cited by 17 publications

References 67 publications

Synthesis of Two-Dimensional Plasmonic Molybdenum Oxide Nanomaterials by Femtosecond Laser Irradiation

Synthesis of Two-Dimensional Plasmonic Molybdenum Oxide Nanomaterials by Femtosecond Laser Irradiation

Mechanism for Redox Exfoliation of Layered Transition Metal Dichalcogenides

Collapse Mechanism in Few-Layer MoS₂Langmuir Films

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An elevated concentration of MoS2 lowers the efficacy of liquid-phase exfoliation and triggers the production of MoOx nanoparticles

Abstract: The oxidation of MoS2 with a simultaneous decrease of MoS2 content.

Cited by 17 publications

References 67 publications

Synthesis of Two-Dimensional Plasmonic Molybdenum Oxide Nanomaterials by Femtosecond Laser Irradiation

Synthesis of Two-Dimensional Plasmonic Molybdenum Oxide Nanomaterials by Femtosecond Laser Irradiation

Mechanism for Redox Exfoliation of Layered Transition Metal Dichalcogenides

Collapse Mechanism in Few-Layer MoS2Langmuir Films

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An elevated concentration of MoS₂ lowers the efficacy of liquid-phase exfoliation and triggers the production of MoO_x nanoparticles

Collapse Mechanism in Few-Layer MoS₂Langmuir Films