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Communication Dans Un Congrès Année : 2022

Characteristic length scales of plasma electrochemical reactors for nanomaterials synthesis

Échelles de longueur caractéristiques des réacteurs électrochimiques à plasma pour la synthèse de nanomatériaux

Résumé

Many approaches to nanomaterials synthesis can require high temperature, strong/toxic reducing agents, or are complex/expensive. The plasma electrochemical reactor (PEC), composed of an atmospheric-pressure plasma with an aqueous electrode, may provide unique physico-chemical conditions that overcome these difficulties because non-equilibrium electrochemistry and nucleation are initiated in solution without additional heating or reducing agents. Indeed, the synthesis of graphene quantum dots (GQD) has been successfully demonstrated by PEC [1,2]. We seek to develop a detailed mechanism of GQD growth, which likely involves complex non-equilibrium plasma chemistry and interactions near the plasma-liquid interface. Up to now, the chemistry of the liquid phase has mainly been inferred from ex situ or volume-averaged measurements. Conventional experimental techniques suffer from a lack of selectivity and/or degradation of dyes, chemical probes, or spin traps/probes introduced into the liquid. Spatial resolution is often poor or inaccessible. To move beyond ex situ techniques, we have developed an in situ multi-diagnostics approach to encompass a wide range of physical and chemical properties at the plasma-water interface. In particular, this platform features in situ spontaneous Raman microspectroscopy, which is advantageous because of its non-intrusiveness, selectivity, versatility, and straightforward calibration. Using a light-sheet technique, we have probed the interfacial region with micron-scale spatial resolution. To gain insight into the effect of the plasma on the solvent, we tracked the Raman spectrum of water. In particular, from the shape of the –OH stretch band, we observe that the plasma weakens the hydrogen bonding network of water near the interface. Also, near the interface, the concentrations of aqueous H2O2 and NO3- both show an excess in concentration relative to the bulk liquid [3]. Similar interfacial layers have been modeled for radical species such as OH but not for long-lived species such as NO3-. Concerning GQDs, we tracked their production via in situ photoluminescence (PL) spectroscopy. The PL intensity reached a maximum at mm depth rather than near the interface. In addition, particle image velocimetry showed that the liquid flow field exhibits a low-velocity zone at this depth. Together, these results provide the fullest description to date of the reaction environment during GQD synthesis. Acknowledgments Financial support: ANR grants ANR-15-CE06-0007-01 and ANR-11-LABX-0017-01, PHC Orchid 40938YL, CNRS-IEA “GRAFMET”. References [1] Orrière, T., Kurniawan, D., Chang, Y. C., Pai, D. Z., & Chiang, W. H. (2020). Nanotechnology 31 (485001). [2] Yang, J. S., Pai, D. Z., & Chiang, W. H. (2019). Carbon 153, 315-319. [3] Pai, D. Z. (2021) J. Phys. D. : Appl. Phys. 54, 355201
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Dates et versions

hal-04488854 , version 1 (05-03-2024)

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  • HAL Id : hal-04488854 , version 1

Citer

David Z Pai, Wei-Hung Chiang, Darwin Kurniawan, Francesca Caielli, Karthik Thyagarajan, et al.. Characteristic length scales of plasma electrochemical reactors for nanomaterials synthesis. 11th International Symposium on Plasma Nanoscience, Sep 2022, Seville (Spain), Spain. ⟨hal-04488854⟩
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