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arxiv: 2605.19498 · v1 · pith:D5H3XUPKnew · submitted 2026-05-19 · ⚛️ physics.optics · cond-mat.mes-hall· physics.app-ph

Near-Field Vibrational Energy Transfer for Mid-Infrared Upconversion in Plasmonic Nanogaps

Avisekh Pal , Anju Sajan , Christopher Sumner , Eman Alharbi , Wolfgang Theis , Rohit Chikkaraddy This is my paper

Pith reviewed 2026-05-20 02:44 UTC · model grok-4.3

classification ⚛️ physics.optics cond-mat.mes-hallphysics.app-ph
keywords vibrational energy transfermid-infrared upconversionplasmonic nanogapsnear-field couplinganti-Stokes emissionmolecular spacersintramolecular vibrational redistribution
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The pith

Sub-2 nm plasmonic nanogaps enable mid-infrared vibrational energy transfer that upconverts to visible light at efficiencies above 0.3%.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper establishes that extreme lateral electromagnetic confinement inside metal-molecule-metal cavities can couple directly to in-plane molecular dipoles and move vibrational energy from donor to acceptor before intramolecular redistribution dissipates it. Continuous-wave mid-infrared light selectively excites the C≡N stretch, and the resulting near-field interaction produces anti-Stokes visible emission. The observed efficiency exceeds 0.3 percent and is set by the race between the plasmon-mediated transfer rate and sub-picosecond IVR. A reader would care because the result shows plasmonic confinement can reroute molecular relaxation channels that normally prevent intermolecular vibrational coupling at room temperature. The work therefore supplies a concrete route to vibrational nanophotonics and low-power mid-infrared detection that relies on molecular degrees of freedom.

Core claim

In sub-2 nm plasmonic nanogaps formed by self-assembled molecular spacers, the extreme lateral field confinement in metal-molecule-metal ring cavities couples efficiently to in-plane molecular dipoles. Continuous-wave mid-infrared excitation populates the C≡N vibrational donors, and plasmon-enhanced near-field coupling transfers this energy to nearby electronic acceptors, generating anti-Stokes visible emission. Upconversion efficiencies exceed 0.3 percent and are limited by competition between the plasmon-mediated transfer rate and sub-picosecond intramolecular vibrational redistribution.

What carries the argument

Extreme lateral field confinement inside metal-molecule-metal ring cavities defined by self-assembled molecular spacers that couple to in-plane dipoles and enable plasmon-mediated vibrational donor-acceptor transfer.

If this is right

  • Vibrational relaxation pathways can be redirected by plasmonic confinement at low power densities.
  • Mid-infrared excitation can generate visible luminescence through intermolecular vibrational transfer.
  • Room-temperature mid-infrared detection becomes possible using molecular vibrational degrees of freedom.
  • Intermolecular vibrational interactions can be engineered for bioimaging applications.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same confinement geometry could be tested with other vibrational modes such as C-H or O-H stretches to check generality.
  • Device integration might allow on-chip conversion of weak mid-infrared signals into detectable visible photons without cryogenic cooling.
  • Polarization control of the incident field could provide a switchable handle on the transfer efficiency.

Load-bearing premise

The visible upconversion arises from plasmon-mediated near-field vibrational coupling that outcompetes sub-picosecond IVR rather than from thermal heating, direct electronic excitation, or other unaccounted processes.

What would settle it

If increasing the molecular spacer thickness beyond 2 nm or rotating the excitation polarization away from in-plane alignment eliminates the anti-Stokes visible signal while thermal signatures remain, the near-field transfer mechanism would be ruled out.

Figures

Figures reproduced from arXiv: 2605.19498 by Anju Sajan, Avisekh Pal, Christopher Sumner, Eman Alharbi, Rohit Chikkaraddy, Wolfgang Theis.

Figure 1
Figure 1. Figure 1: Donor-acceptor vibrational energy transfer enabling MIR upconversion. (a) Energy-level diagram illustrating MIR excitation (𝜆MIR = 4.55μm) of a BPTCN self-assembled monolayer (SAM), driving the -C≡N stretching vibration from the ground state |0⟩D to the first vibrationally excited state |1⟩𝐷. (b) The vibrational energy transfer from MIR-excited BPTCN to a nearby methylene blue (MB) molecule, leading to ele… view at source ↗
Figure 2
Figure 2. Figure 2: Donor-acceptor mediated MIR-to-visible upconversion in MIM rings. (a) Photoluminescence (PL) spectrum of MB from an individual MIM ring under direct optical excitation at 633nm (25µW/µm2 ; red trace). Compared to the absorption spectrum of MB (blue) and the PL [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
read the original abstract

F\"{o}rster energy transfer underpins modern photonics, yet establishing an analogous vibrational pathway in the mid-infrared (MIR) remains highly challenging, as sub-picosecond intramolecular vibrational redistribution (IVR) suppresses intermolecular coupling. Here we demonstrate vibrational donor--acceptor transfer in the MIR and subsequent upconversion to visible luminescence enabled by sub-2 nm plasmonic nanogaps. The extreme lateral field confinement in metal--molecule--metal ring cavities defined by self-assembled molecular spacers couples efficiently to in-plane molecular dipoles. Continuous-wave MIR excitation selectively populates $-\mathrm{C}\equiv\mathrm{N}$ vibrational donors, and plasmon-enhanced near-field coupling transfers this energy to nearby electronic acceptors, generating anti-Stokes visible emission under low power densities. Upconversion efficiencies exceeding $0.3\%$ are observed, limited by competition between the plasmon-mediated transfer rate and IVR. These results show that extreme plasmonic confinement can redirect molecular vibrational relaxation pathways, opening a route toward vibrational nanophotonics, intermolecular interactions for bioimaging, and room-temperature MIR detection based on molecular degrees of freedom.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 2 minor

Summary. The manuscript demonstrates vibrational donor-acceptor energy transfer in the mid-infrared using sub-2 nm plasmonic nanogaps in metal-molecule-metal ring cavities formed by self-assembled molecular spacers. Selective continuous-wave MIR excitation of C≡N vibrational donors enables plasmon-enhanced near-field coupling to in-plane dipoles, transferring energy to electronic acceptors and producing anti-Stokes visible luminescence with upconversion efficiencies exceeding 0.3%, by outcompeting sub-picosecond IVR.

Significance. If the central claim holds, the result is significant for establishing a vibrational analog to Förster transfer under extreme confinement, with potential applications in vibrational nanophotonics, intermolecular interactions for bioimaging, and room-temperature MIR detection. Strengths include the experimental demonstration with supporting spectra, power dependence, wavelength selectivity, and control structures that align with the proposed plasmon-mediated mechanism.

minor comments (2)
  1. The abstract and main text would benefit from explicit statements on how the upconversion efficiency (>0.3%) is defined and calculated, including any corrections for collection efficiency or quantum yield assumptions.
  2. Figure captions and legends should clearly distinguish between donor emission, acceptor upconversion, and control samples to aid reader interpretation of the spatial localization and wavelength selectivity data.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our manuscript, accurate summary of the central claims, and recommendation for minor revision. We appreciate the recognition of the experimental strengths, including the spectra, power dependence, wavelength selectivity, and control structures supporting the plasmon-mediated vibrational energy transfer mechanism.

Circularity Check

0 steps flagged

No significant circularity in experimental demonstration

full rationale

The paper presents an experimental demonstration of vibrational energy transfer in plasmonic nanogaps, supported by spectra, power dependence, control structures, wavelength selectivity, and spatial localization arguments. No mathematical derivation chain, fitted parameters renamed as predictions, or self-citation load-bearing steps are present; the central claim rests on direct observations of anti-Stokes emission and transfer rates competing with IVR rather than reducing to self-defined inputs or prior author results by construction. The work is self-contained against external benchmarks via experimental controls.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The abstract relies on established domain knowledge in molecular spectroscopy and plasmonics without introducing new free parameters, axioms beyond standard assumptions, or invented entities; full text would be needed to audit further.

axioms (1)
  • domain assumption Sub-picosecond intramolecular vibrational redistribution suppresses intermolecular coupling in the MIR.
    Invoked in the abstract to explain the challenge and why plasmonic confinement is needed to enable transfer.

pith-pipeline@v0.9.0 · 5755 in / 1328 out tokens · 60145 ms · 2026-05-20T02:44:12.906894+00:00 · methodology

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Works this paper leans on

62 extracted references · 62 canonical work pages · 1 internal anchor

  1. [1]

    10th Spiers Memorial Lecture

    Főrster, T. 10th Spiers Memorial Lecture. Transfer mechanisms of electronic excitation. Discuss. Faraday Soc. 27, 7–17 (1959)

    work page 1959

  2. [2]

    Dexter, D. L. A Theory of Sensitized Luminescence in Solids. J. Chem. Phys. 21, 836–850 (1953)

    work page 1953

  3. [3]

    Yang, F., Sambles, J. R. & Bradberry, G. W. Long -range coupled surface exciton polaritons. Phys. Rev. Lett. 64, 559–562 (1990)

    work page 1990

  4. [4]

    Andrews, D. L. & Demidov, A. A. Resonance Energy Transfer. (Wiley, 1999)

    work page 1999

  5. [5]

    Scholes, G. D. Long -Range Resonance Energy Transfer in Molecular Systems. Annual Review of Physical Chemistry 54, 57–87 (2003)

    work page 2003

  6. [6]

    Engel, G. S. et al. Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems. Nature 446, 782–786 (2007)

    work page 2007

  7. [7]

    Moerner, W. E. (William E. ). Nobel Lecture: Single -molecule spectroscopy, imaging, and photocontrol: Foundations for super -resolution microscopy. Rev. Mod. Phys. 87, 1183 –1212 (2015)

    work page 2015

  8. [8]

    Su, R. et al. FRET Materials for Biosensing and Bioimaging. Chem. Rev. 125, 9429–9551 (2025)

    work page 2025

  9. [9]

    Roy, R., Hohng, S. & Ha, T. A practical guide to single -molecule FRET. Nat Methods 5, 507–516 (2008)

    work page 2008

  10. [10]

    & Xiong, W

    Chen, T.-T., Du, M., Yang, Z., Yuen-Zhou, J. & Xiong, W. Cavity -enabled enhancement of ultrafast intramolecular vibrational redistribution over pseudorotation. Science 378, 790–794 (2022)

    work page 2022

  11. [11]

    & Hamm, P

    Fernández-Terán, R. & Hamm, P . A closer look into the distance dependence of vibrational energy transfer on surfaces using 2D IR spectroscopy. J. Chem. Phys. 153, 154706 (2020)

    work page 2020

  12. [12]

    & Wolynes, P

    Gruebele, M. & Wolynes, P . G. Vibrational Energy Flow and Chemical Reactions. Acc. Chem. Res. 37, 261–267 (2004)

    work page 2004

  13. [13]

    Nesbitt, D. J. & Field, R. W. Vibrational Energy Flow in Highly Excited Molecules: Role of Intramolecular Vibrational Redistribution. J. Phys. Chem. 100, 12735–12756 (1996)

    work page 1996

  14. [14]

    He, H. et al. Mapping enzyme activity in living systems by real -time mid-infrared photothermal imaging of nitrile chameleons. Nat Methods 21, 342–352 (2024)

    work page 2024

  15. [15]

    Yin, J. et al. Video-rate mid-infrared photothermal imaging by single-pulse photothermal detection per pixel. Science Advances 9, eadg8814 (2023)

    work page 2023

  16. [16]

    Wang, H. et al. Bond-selective fluorescence imaging with single-molecule sensitivity. Nat. Photon. 17, 846–855 (2023)

    work page 2023

  17. [17]

    & Zeng, H

    Huang, K., Fang, J., Yan, M., Wu, E. & Zeng, H. Wide-field mid-infrared single-photon upconversion imaging. Nat Commun 13, 1077 (2022)

    work page 2022

  18. [18]

    J., Meng, L., Pedersen, C

    Barh, A., Rodrigo, P . J., Meng, L., Pedersen, C. & Tidemand-Lichtenberg, P . Parametric upconversion imaging and its applications. Adv. Opt. Photon., AOP 11, 952–1019 (2019)

    work page 2019

  19. [19]

    Wang, Y . et al. Mid-Infrared Single-Photon Edge Enhanced Imaging Based on Nonlinear Vortex Filtering. Laser & Photonics Reviews 15, 2100189 (2021)

    work page 2021

  20. [20]

    Gemmell, N. R. Loss -Compensated and Enhanced Midinfrared Interaction -Free Sensing with Undetected Photons. Phys. Rev. Appl. 19, (2023)

    work page 2023

  21. [21]

    Yao, J. et al. Giant single-step upconversion via sub–35-fs phonon dynamics in the nonlinear optical regime. Science Advances 11, eadx1686 (2025)

    work page 2025

  22. [22]

    Quan, J. et al. On-site enhancement and control of spin -forbidden dark excitons in a plasmonic heterostructure. Nat. Photon. 20, 49–54 (2026)

    work page 2026

  23. [23]

    Chikkaraddy, R., Arul, R., Jakob, L. A. & Baumberg, J. J. Single-molecule mid-infrared spectroscopy and detection through vibrationally assisted luminescence. Nat. Photon. 1–7 (2023) doi:10.1038/s41566-023-01263-4

    work page doi:10.1038/s41566-023-01263-4 2023

  24. [24]

    J., Aizpurua, J., Mikkelsen, M

    Baumberg, J. J., Aizpurua, J., Mikkelsen, M. H. & Smith, D. R. Extreme nanophotonics from ultrathin metallic gaps. Nature Materials 18, 668–678 (2019)

    work page 2019

  25. [25]

    Li, Y . et al. Boosting Light−Matter Interactions in Plasmonic Nanogaps. Advanced Materials 36, 2405186 (2024)

    work page 2024

  26. [26]

    Xomalis, A. et al. Detecting mid -infrared light by molecular frequency upconversion in dual - wavelength nanoantennas. Science 374, 1268–1271 (2021)

    work page 2021

  27. [27]

    Lee, J. et al. Extraordinary optical transmission and second harmonic generation in sub –10-nm plasmonic coaxial aperture. Nanophotonics 9, 3295–3302 (2020)

    work page 2020

  28. [28]

    Yoo, D. et al. High-Contrast Infrared Absorption Spectroscopy via Mass -Produced Coaxial Zero - Mode Resonators with Sub-10 nm Gaps. Nano Lett. 18, 1930–1936 (2018)

    work page 1930

  29. [29]

    Jiang, K. et al. Large-Scale Fabrication of 5 nm Plasmonic Hybrid Nanoslit Arrays. Nano Lett. 25, 8636–8643 (2025)

    work page 2025

  30. [30]

    Beesley, D. J. et al. Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography. Nat Commun 5, 3933 (2014)

    work page 2014

  31. [31]

    Namgung, S., Koester, S. J. & Oh, S. -H. Ultraflat Sub -10 Nanometer Gap Electrodes for Two - Dimensional Optoelectronic Devices. ACS Nano https://doi.org/10.1021/acsnano.0c10759 (2021) doi:10.1021/acsnano.0c10759

    work page doi:10.1021/acsnano.0c10759 2021

  32. [32]

    Yoo, D. et al. Modeling and observation of mid-infrared nonlocality in effective epsilon-near-zero ultranarrow coaxial apertures. Nat Commun 10, 4476 (2019)

    work page 2019

  33. [33]

    Shi, J. et al. A room -temperature polarization -sensitive CMOS terahertz camera based on quantum-dot-enhanced terahertz-to-visible photon upconversion. Nat. Nanotechnol. 17, 1288– 1293 (2022)

    work page 2022

  34. [34]

    Baiz, C. R. et al. Vibrational Spectroscopic Map, Vibrational Spectroscopy, and Intermolecular Interaction. Chem. Rev. 120, 7152–7218 (2020)

    work page 2020

  35. [35]

    Rubtsova, N. I. & Rubtsov, I. V. Vibrational Energy Transport in Molecules Studied by Relaxation - Assisted Two-Dimensional Infrared Spectroscopy. Annual Review of Physical Chemistry 66, 717– 738 (2015)

    work page 2015

  36. [36]

    Chikkaraddy, R. et al. Mapping Nanoscale Hotspots with Single-Molecule Emitters Assembled into Plasmonic Nanocavities Using DNA Origami. Nano Lett. 18, 405–411 (2018)

    work page 2018

  37. [37]

    Kongsuwan, N. et al. Suppressed Quenching and Strong -Coupling of Purcell -Enhanced Single - Molecule Emission in Plasmonic Nanocavities. ACS Photonics 5, 186–191 (2018)

    work page 2018

  38. [38]

    Horton, M. J. et al. Nanoscopy through a plasmonic nanolens. PNAS 117, 2275–2281 (2020)

    work page 2020

  39. [39]

    Rocchetti, S. et al. Amplified Plasmonic Forces from DNA Origami -Scaffolded Single Dyes in Nanogaps. Nano Lett. 23, 5959–5966 (2023)

    work page 2023

  40. [40]

    Griffiths, J. et al. Resolving sub-angstrom ambient motion through reconstruction from vibrational spectra. Nat Commun 12, 6759 (2021)

    work page 2021

  41. [41]

    Carnegie, C. et al. Room-Temperature Optical Picocavities below 1 nm3 Accessing Single -Atom Geometries. J. Phys. Chem. Lett. 9, 7146–7151 (2018)

    work page 2018

  42. [42]

    Kang, J. F. et al. Self-Assembled Rigid Monolayers of 4‘-Substituted-4-mercaptobiphenyls on Gold and Silver Surfaces. Langmuir 17, 95–106 (2001)

    work page 2001

  43. [43]

    & Gallego, J

    Otero, R., Miranda, R. & Gallego, J. M. A Comparative Computational Study of the Adsorption of TCNQ and F4-TCNQ on the Coinage Metal Surfaces. ACS Omega 4, 16906–16915 (2019)

    work page 2019

  44. [44]

    & Armstrong, N

    Patterson, T., Pankow, J. & Armstrong, N. Tetracyanoquinodimethane thin films on copper, gold, platinum, and tin (IV) sulfide: characterization by x-ray photoelectron spectroscopy. Langmuir 12, 3160–6 (1991)

    work page 1991

  45. [45]

    Whaley-Mayda, L., Guha, A., Penwell, S. B. & Tokmakoff, A. Fluorescence -Encoded Infrared Vibrational Spectroscopy with Single -Molecule Sensitivity. J. Am. Chem. Soc. 143, 3060 –3064 (2021)

    work page 2021

  46. [46]

    Chikkaraddy, R., Xomalis, A., Jakob, L. A. & Baumberg, J. J. Mid -infrared-perturbed molecular vibrational signatures in plasmonic nanocavities. Light Sci Appl 11, 19 (2022)

    work page 2022

  47. [47]

    Liang, L., Wang, C., Chen, J., Wang, Q. J. & Liu, X. Incoherent broadband mid -infrared detection with lanthanide nanotransducers. Nat. Photon. 16, 712–717 (2022)

    work page 2022

  48. [48]

    Meng, Z.-D. et al. Colocalized Raman and IR Spectroscopies via Vibrational-Encoded Fluorescence for Comprehensive Vibrational Analysis. J. Am. Chem. Soc. 147, 16309–16318 (2025)

    work page 2025

  49. [49]

    Zhang, Y . et al. Fluorescence-Detected Mid-Infrared Photothermal Microscopy. J. Am. Chem. Soc. 143, 11490–11499 (2021)

    work page 2021

  50. [50]

    Wang, C. W. et al. Mid-infrared detection through ligand-driven local heating in lanthanide-doped nanoparticles. Nat Commun https://doi.org/10.1038/s41467-026-70900-7 (2026) doi:10.1038/s41467-026-70900-7

    work page doi:10.1038/s41467-026-70900-7 2026

  51. [51]

    Wang, H. et al. Room-Temperature Single-Molecule Infrared Imaging and Spectroscopy through Bond-Selective Fluorescence. Angewandte Chemie International Edition 63, e202413647 (2024)

    work page 2024

  52. [52]

    & Min, W

    Qian, N., Xiong, H., Wei, L., Shi, L. & Min, W. Merging Vibrational Spectroscopy with Fluorescence Microscopy: Combining the Best of Two Worlds. Annual Review of Physical Chemistry 76, 279–301 (2025)

    work page 2025

  53. [53]

    L., Gray, T

    Puro, R. L., Gray, T. P ., Kapfunde, T. A., Richter-Addo, G. B. & Raschke, M. B. Vibrational Coupling Infrared Nanocrystallography. Nano Lett. 24, 1909–1915 (2024)

    work page 1909

  54. [54]

    Dows, D. A. Intermolecular Coupling of Vibrations in Molecular Crystals. J. Chem. Phys. 32, 1342– 1347 (1960)

    work page 1960

  55. [55]

    Wilcken, R. et al. Antenna-coupled infrared nanospectroscopy of intramolecular vibrational interaction. Proceedings of the National Academy of Sciences 120, e2220852120 (2023)

    work page 2023

  56. [56]

    Jakob, L. A. et al. Optomechanical Pumping of Collective Molecular Vibrations in Plasmonic Nanocavities. ACS Nano 19, 10977–10988 (2025)

    work page 2025

  57. [57]

    Addressing intramolecular vibrational redistribution in a single molecule through pump and probe surface-enhanced vibrational spectroscopy

    Loirette-Pelous, A., Boto, R. A., Aizpurua, J. & Esteban, R. Addressing intramolecular vibrational redistribution in a single molecule through pump and probe surface -enhanced vibrational spectroscopy. Preprint at https://doi.org/10.48550/arXiv.2601.02117 (2026)

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2601.02117 2026

  58. [58]

    Shalabney, A. et al. Coherent coupling of molecular resonators with a microcavity mode. Nat Commun 6, (2015)

    work page 2015

  59. [59]

    B., Cogdell, R

    Hildner, R., Brinks, D., Nieder, J. B., Cogdell, R. J. & Van Hulst, N. F. Quantum coherent energy transfer over varying pathways in single light -harvesting complexes. Science 340, 1448 –1451 (2013)

    work page 2013

  60. [60]

    Ghenuche, P . et al. Matching Nanoantenna Field Confinement to FRET Distances Enhances Förster Energy Transfer Rates. Nano Lett. 15, 6193–6201 (2015)

    work page 2015

  61. [61]

    O., Viscomi, F

    Hamza, A. O., Viscomi, F. N., Bouillard, J.-S. G. & Adawi, A. M. Förster Resonance Energy Transfer and the Local Optical Density of States in Plasmonic Nanogaps. J. Phys. Chem. Lett. 12, 1507–1513 (2021)

    work page 2021

  62. [62]

    Xie, X. et al. Plasmonic Nanocavity-Assisted Long-Range Dipole–Dipole Interactions for Rare-Earth Ions. Nano Lett. 26, 2877–2885 (2026)

    work page 2026