Ultrafast Spectroscopy of Proton Transfer Dynamics

Ultrafast spectroscopy has emerged as a powerful tool for dissecting the mechanisms and time scales of proton transfer in chemical and biological systems. By employing light pulses on the femtosecond (10⁻¹⁵ s) to picosecond (10⁻¹² s) time scale, researchers capture transient species, hydrogen‐bond rearrangements and energy redistribution associated with excited‐state proton transfer (ESPT). Such techniques reveal how protons hop along hydrogen‐bond networks, how solvent shells reorganise to accommodate charge separation and how protein environments guide directional proton movement. Insights gleaned from these studies underpin our understanding of energy conversion in photoactive proteins, the design of light‐driven catalysts and the development of responsive materials. Advancements in spectral resolution, electronic resonance enhancement and coherent Raman detection have collectively extended the reach of ultrafast probes, allowing direct observation of structural dynamics and vibrational signatures that accompany proton release, transfer and recombination.

Research from Nature Portfolio

Recent method developments in broadband stimulated Raman spectroscopy have significantly enhanced the capacity to monitor proton transfer dynamics. Coherent stimulation of molecular vibrations under electronic resonance conditions can now be achieved with ultrashort, spectrally tailored pulses, enabling selective amplification of vibrational modes linked to proton movement while suppressing fluorescence background. A quantum‐mechanical treatment of the third‐order nonlinear response has provided protocols to disentangle overlapping field interactions and retrieve excitation profiles of specific chromophores. In parallel, advances in time-resolved Raman techniques have been applied to chromophores undergoing structural reorganisation after excitation, demonstrating how coupling between high-frequency and low-frequency vibrational motions can influence the rate and pathway of charge or proton transfer. These foundational studies have laid the groundwork for directly resolving proton‐transfer events in more complex environments by enhancing temporal and spectral precision.

Ultrafast Spectroscopy of Proton Transfer Dynamics publication trend

The graph below shows the total number of articles in ultrafast spectroscopy of proton transfer dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Ultrafast Spectroscopy: A suite of techniques employing laser pulses of femtosecond to picosecond duration to probe rapid molecular processes.

Excited-State Proton Transfer (ESPT): The transfer of a proton following electronic excitation of a molecule, often mediated by transient hydrogen-bond networks.

Femtosecond Stimulated Raman Spectroscopy (FSRS): A time-resolved vibrational spectroscopy method that uses ultrashort Raman pump and probe pulses to capture structural changes in excited states.

Photoacid/Photobase: A molecule whose acidity or basicity increases markedly upon electronic excitation, facilitating proton donation or uptake.

Solvation Dynamics: The time-dependent reorganisation of solvent molecules around a solute or reactive intermediate, critical in stabilising charge separation.

References

1. Photocurrent Generation and Polarity Switching in Electrochemical Cells through Light‐induced Excited State Proton Transfer of Photoacids and Photobases**. Angewandte Chemie International Edition (2023).
2. Observing Aqueous Proton-Uptake Reactions Triggered by Light. Journal of the American Chemical Society (2023).
3. Modeling Excited-State Proton Transfer to Solvent: A Dynamics Study of a Super Photoacid with a Hybrid Implicit/Explicit Solvent Model. Journal of Chemical Theory and Computation (2020).
4. Electronic resonances in broadband stimulated Raman spectroscopy. Scientific Reports (2016).
5. Spectrally tailored narrowband pulses for femtosecond stimulated Raman spectroscopy in the range 330-750 nm.. Optics Express (2013).
6. Two-Dimensional Impulsively Stimulated Resonant Raman Spectroscopy of Molecular Excited States. Physical Review X (2020).