Ultrafast Excited-State Dynamics in Photoprotective Compounds

Photoprotective compounds, whether derived from plants, lichens or synthetic analogues, absorb harmful ultraviolet radiation and dissipate the excess energy within femtoseconds to picoseconds. This ultrafast relaxation prevents molecular damage and underpins natural sunscreens and biomimetic filters. Key to this process are rapid non-radiative pathways such as internal conversion and photoisomerisation, often mediated by conical intersections that funnel excited-state populations back to the ground state without bond scission. Advances in femtosecond transient absorption spectroscopy, complemented by high-level electronic-structure calculations, have illuminated how structural features—such as symmetry, hydrogen bonding or embedding matrices—govern energy dissipation. By unraveling these mechanisms, researchers are now able to design next-generation UV filters with enhanced photostability, reduced photoproduct toxicity and broader spectral coverage, addressing global needs in sun care, crop protection and materials science.

Research from Nature Portfolio

Recent studies have explored symmetrically functionalised sinapate esters as novel UV-A filters. By engineering molecules bearing identical cis- and trans-isomers, researchers achieved balanced photostability and minimised genotoxic by-products. Ultrafast spectroscopy on skin-mimetic substrates revealed sub-picosecond internal conversion via a peaked conical intersection, ensuring rapid dissipation of absorbed energy. Complementary assays demonstrated low endocrine-disrupting potential and promising antioxidant capacity. This work provides a blueprint for nature-inspired sunscreen design that combines efficient energy funneling with safety and environmental compatibility.

Ultrafast Excited-State Dynamics in Photoprotective Compounds publication trend

The graph below shows the total number of articles in ultrafast excited-state dynamics in photoprotective compounds across all publications each year (not limited to Nature Index journals).

Technical terms

Excited-state dynamics: The sequence of events and structural changes a molecule undergoes after absorbing a photon.

Internal conversion: A non-radiative transition between electronic states of the same spin multiplicity, dissipating energy as heat.

Photoisomerisation: Light-induced alteration of a molecule’s geometric configuration, often between cis and trans forms.

Conical intersection: A region where two electronic potential energy surfaces meet, enabling ultrafast non-radiative decay.

Transient absorption spectroscopy: A technique that tracks changes in absorption on femtosecond to nanosecond timescales to map excited-state lifetimes.

Photostability: The ability of a molecule to withstand photoexcitation without chemical degradation.

References

1. Photoprotection: extending lessons learned from studying natural sunscreens to the design of artificial sunscreen constituents. Chemical Society Reviews (2017).
2. Towards symmetry driven and nature inspired UV filter design. Nature Communications (2019).
3. Cortical polysaccharides play a crucial role in lichen UV protection. Cell Reports Physical Science (2024).
4. Characteristic Photoprotective Molecules from the Sphagnum World: A Solution-Phase Ultrafast Study of Sphagnic Acid. Molecules (2023).
5. Understanding the Impact of Symmetrical Substitution on the Photodynamics of Sinapate Esters Using Gas-Phase Ultrafast Spectroscopy. The Journal of Physical Chemistry Letters (2023).