March 2024

Anisotropic materials with oppositely signed dielectric tensors support hyperbolic polaritons, displaying enhanced electromagnetic localization and directional energy flow. *

However, the most reported hyperbolic phonon polaritons are difficult to apply for active electro-optical modulations and optoelectronic devices. *

In the nature communications letter “Manipulating hyperbolic transient plasmons in a layered semiconductor”, Rao Fu, Yusong Qu, Mengfei Xue, Xinghui Liu, Shengyao Chen, Yongqian Zhao, Runkun Chen, Boxuan Li, Hongming Weng, Qian Liu, Qing Dai and Jianing Chen report a dynamic topological plasmonic dispersion transition in black phosphorus (BP) via photo-induced carrier injection, i.e., transforming the iso-frequency contour from a pristine ellipsoid to a non-equilibrium hyperboloid. *

They introduce a promising approach to optically manipulate robust transient hyperbolic plasmons in the layered semiconductor black phosphorus using a dedicated ultrafast nanoscopy scheme. Optical pumping allows the BP’s IFCs to topologically transit from the pristine ellipsoid to the non-equilibrium hyperboloid, exhibiting exotic non-equilibrium hyperbolic plasmon properties, such as the optically tunable plasmonic dispersion and the coexistence of different transient plasmonic modes. *

Their work also demonstrates the peculiar transient plasmonic properties of the studied layered semiconductor, such as the ultrafast transition, low propagation losses, efficient optical emission from the black phosphorus’s edges, and the characterization of different transient plasmon modes. *

The results that Rao Fu et al. present may be relevant for the development of future optoelectronic applications. *

NanoWorld® ARROW-NCPt AFM probes with a Pt/Ir coating were used for the characterization with ultrafast nanoscopy. The pump and probe pulses were spatially overlapped on the Platinum/Iridium coated Arrow probe through a parabolic mirror of a commercial scattering-type scanning near-field optical microscope. *

Fig. 4 from Rao Fu et al. “Manipulating hyperbolic transient plasmons in a layered semiconductor”:Dynamic analysis of the transient plasmons. a Normalized near-field amplitude s3/s3,Si of a 280-nm-thick BP slab for twelve delay times τ. Scale bar, 1 µm. b Near-field amplitude curves for the corresponding twelve different delay times τ in a. c Dynamics of the relative near-field intensity of the first (∆S1) and the second bright strip (∆S2) in b. Opened circles are the experimental data, and solid lines are bi-exponential fitting for ∆S1 and exponential fitting for ∆S2, respectively. d Dynamics of the near-field amplitude s3 from the black circle in a. The inset displays the s3 at τ = −2 to 6 ps, and the dashed line marks the s3 level of the pristine state. NanoWorld® ARROW-NCPt AFM probes with a Pt/Ir coating were used for the characterization with ultrafast nanoscopy. The pump and probe pulses were spatially overlapped on the Pt/Ir coated Arrow probe through a parabolic mirror of a commercial scattering-type scanning near-field optical microscope. — Fig. 4 from Rao Fu et al. “Manipulating hyperbolic transient plasmons in a layered semiconductor”:
Dynamic analysis of the transient plasmons.
a Normalized near-field amplitude s3/s3,Si of a 280-nm-thick BP slab for twelve delay times τ. Scale bar, 1 µm. b Near-field amplitude curves for the corresponding twelve different delay times τ in a. c Dynamics of the relative near-field intensity of the first (∆S1) and the second bright strip (∆S2) in b. Opened circles are the experimental data, and solid lines are bi-exponential fitting for ∆S1 and exponential fitting for ∆S2, respectively. d Dynamics of the near-field amplitude s3 from the black circle in a. The inset displays the s3 at τ = −2 to 6 ps, and the dashed line marks the s3 level of the pristine state.

*Rao Fu, Yusong Qu, Mengfei Xue, Xinghui Liu, Shengyao Chen, Yongqian Zhao, Runkun Chen, Boxuan Li, Hongming Weng, Qian Liu, Qing Dai and Jianing Chen
Manipulating hyperbolic transient plasmons in a layered semiconductor
Nature Communications volume 15, Article number: 709 (2024)
DOI: https://doi.org/10.1038/s41467-024-44971-3

Please follow this external link to read the full article: https://rdcu.be/dBD85

The article “Manipulating hyperbolic transient plasmons in a layered semiconductor” by Rao Fu, Yusong Qu, Mengfei Xue, Xinghui Liu, Shengyao Chen, Yongqian Zhao, Runkun Chen, Boxuan Li, Hongming Weng, Qian Liu, Qing Dai and Jianing Chen is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third-party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

The nature of the electrolyte cation is known to have a significant impact on electrochemical reduction of CO2 at catalyst|electrolyte interfaces. An understanding of the underlying mechanism responsible for catalytic enhancement as the alkali metal cation group is descended is key to guide catalyst development. *

In the article “Studying the cation dependence of CO2 reduction intermediates at Cu by in situ VSFG spectroscopy” Liam C. Banerji, Hansaem Jang, Adrian M. Gardner and Alexander J. Cowan use in situ vibrational sum frequency generation (VSFG) spectroscopy to monitor changes in the binding modes of the CO intermediate at the electrochemical interface of a polycrystalline Cu electrode during CO2 reduction as the electrolyte cation is varied. *

Three alkali metal cations have been chosen for analysis: K+, which is the most commonly used electrolyte cation for eCO2R, Cs+, which has been shown to give the greatest enhancement for C2+ products, and Na+, which shows poorer eCO2R performance than K+ whilst maintaining appreciable levels of C-based products. The ability of VSFG to study catalyst|electrolyte interfaces without the need for modifications, as required in the spectroelectrochemical studies mentioned in the article, which can fundamentally alter the electrodes activity, makes it an important tool to assess the mechanisms occurring on the pc-Cu electrodes routinely employed for eCO2R. *

A CObridge mode is observed only when using Cs+, a cation that is known to facilitate CO2 reduction on Cu, supporting the proposed involvement of CObridge sites in CO coupling mechanisms during CO2 reduction. Ex situ measurements show that the cation dependent CObridge modes correlate with morphological changes of the Cu surface. *

The results presented in the article suggest that a high level of bridge site formation is related to, or facilitated by, the Cu restructuring that happens as a result of the use of the Cs+ cations in the supporting electrolyte. Recent reports have indicated that multiple (bridge) bound CO may be electrochemically inert but this work builds on the emerging evidence that CObridge sites are a key intermediate in the CO–CO coupling step that is required for C2+ formation during eCO2R. *

NanoWorld Pointprobe® CONTR AFM probes for contact mode atomic force microscopy (AFM) were used to characterize the morphology of the CU electrode surface before bulk electrolysis and after bulk electrolysis.*

Fig. 5 from Liam C. Banerji et al. “Studying the cation dependence of CO2 reduction intermediates at Cu by in situ VSFG spectroscopy”: AFM images showing surface morphology of the Cu electrode surface (a) before bulk electrolysis, after bulk electrolysis in CO2 purged 0.5 M (b) NaHCO3, (c) KHCO3 and (d) CsHCO3 and also in (e) CO purged 0.5 M CsHCO3. Image analysis methods are described in the Experimental section.NanoWorld Pointprobe® CONTR AFM probes for contact mode atomic force microscopy (AFM) were used to characterize the morphology of the CU electrode surface before bulk electrolysis and after bulk electrolysis. — Fig. 5 from Liam C. Banerji et al. “Studying the cation dependence of CO2 reduction intermediates at Cu by in situ VSFG spectroscopy”: AFM images showing surface morphology of the Cu electrode surface (a) before bulk electrolysis, after bulk electrolysis in CO2 purged 0.5 M (b) NaHCO3, (c) KHCO3 and (d) CsHCO3 and also in (e) CO purged 0.5 M CsHCO3. Image analysis methods are described in the Experimental section of the original article.

*Liam C. Banerji, Hansaem Jang, Adrian M. Gardner and Alexander J. Cowan
Studying the cation dependence of CO2 reduction intermediates at Cu by in situ VSFG spectroscopy
Chemical Science 2024, 15, 2889-2897
DOI: https://doi.org/10.1039/D3SC05295H

The article “Studying the cation dependence of CO2 reduction intermediates at Cu by in situ VSFG spectroscopy” by Liam C. Banerji, Hansaem Jang, Adrian M. Gardner and Alexander J. Cowan is licensed under a Creative Commons Attribution 3.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third-party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/3.0/.