S. K. Gahlaut, O. Avalos-Ovando, R. Myeong Kim, R. Hussein, S. Juergensen, S. Reich, A. O. Govorov, K. Tae Nam, and I. Bald

Amplification of Photochemical Chiroptical Activity of Chiral Gold Nanocubes

Small 2025, 2505093

Chiral plasmonic nanostructures enable exceptionally high dissymmetry factors (g-factors) compared to chiral molecules and present unparalleled opportunities in light manipulation, polarization-sensitive photochemistry, and chiral sensing. Here polarization-dependent plasmonic chemistry on chiral gold nanocubes (AuNCs) is presented, leveraging the high sensitivity of surface-enhanced Raman scattering (SERS). The AuNCs exhibit strong optical activity and localized surface plasmon resonances acting as highly efficient nanoscale light antennae. Employing the hot electron-induced dehalogenation of 8-Bromoadenine as a model reaction, it is demonstrated that circularly polarized light induces asymmetric reaction rates due to circular dichroism (CD) in hot electron generation efficiency. Astonishingly, the photochemical g-factor, quantified by the differential reaction rate coefficients under left-handed and right-handed circularly polarized light, surpasses its optical counterpart and can be further enhanced by laser intensity. Remarkably, multilayer assemblies of AuNCs exhibit a reversal in photochemical CD, which is tuneable via laser power and enables further g-factor enhancement. Comprehensive electromagnetic simulations of extinction spectra and hot electron generation maps corroborate the profound impact of particle arrangement on the optical g-factor and the g-factor for hot-electron generation. This work demonstrates a systematic approach to enhance the photochemical chiroptical response of chiral AuNCs, paving the way for extraordinary control over chemical reactions with light. 

F. Lever, D. Picconi, D. Mayer, S. Ališauskas, F. Calegari, S. Düsterer, R. Feifel, M. Kuhlmann, T. Mazza, J. Metje, M. S. Robinson, R. J. Squibb, A. Trabattoni, M. Ware, P. Saalfrank, T. J. A. Wolf, M. Gühr

Direct Observation of the ππ* to nπ* Transition in 2-Thiouracil via Time-Resolved NEXAFS Spectroscopy

The Journal of Physical Chemistry Letters, 2025, 16, 16, 4038–4046

The photophysics of nucleobases has been the subject of both theoretical and experimental studies over the past decades due to the challenges posed by resolving the steps of their radiationless relaxation dynamics, which cannot be described in the framework of the Born–Oppenheimer approximation (BOA). In this context, the ultrafast dynamics of 2-thiouracil has been investigated with a time-resolved NEXAFS study at the Free Electron Laser FLASH. Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS) can be used to observe electronic transitions in ultrafast molecular relaxation. We performed time-resolved UV-pump/X-ray probe absorption measurements at the sulfur 2s (L1) and 2p (L2/3) edges. We are able to identify absorption features corresponding to the S2 (ππ*) and S1 (nπ*) electronic states. We observe a delay of 102 ± 11 fs in the population of the nπ* state with respect to the initial optical excitation and interpret the delay as the time scale for the S2 → S1 internal conversion. We furthermore identify oscillations in the absorption signal that match a similar observation in our previous X-ray photoelectron spectroscopy study on the same molecule.

F Monticone, N. A. Mortensen, A. I. Fernández-Domínguez, Y. Luo, X. Zheng, C. Tserkezis, J. B. Khurgin, T. V. Shahbazyan, A. J. Chaves, N. M. R. Peres, G. Wegner, K. Busch, H. Hu, F. Della Sala, P. Zhang, C. Ciracì, J. Aizpurua, A. Babaze, A. G. Borisov, X.-W. Chen, T. Christensen, W. Yan, Y. Yang, U. Hohenester, L. Huber, M. Wubs, S. De Liberato, P. A. D. Gonçalves, F. J. García de Abajo, O. Hess,  et al.

Nonlocality in photonic materials and metamaterials: roadmap

Optical Materials Express 15 (7), 1544-1709 (2025)

Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally adopted in optical material modeling. The growing interest in plasmonic, polaritonic, and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials—metamaterials and metasurfaces—can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In metasurfaces, in particular, nonlocality engineering has emerged as a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials and metamaterials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward—toward new scientific discoveries and technological advancements.

Y.Pfeifer, T. Stensitzki, J. Dostál, E. Titov, M. Kloz, P. Saalfrank and H. Müller-Werkmeister

pH-dependent ultrafast photodynamics of p-hydroxyphenacyl: deprotonation accelerates the photo-uncaging reaction

Physical Chemistry Chemical Physics, 2025, Advance Article

Photolabile protecting groups (PPGs) possess broad application potential as they allow spatially and temporally controlled release of the protected group. While the photochemistry of many PPGs has been studied in detail, data under aqueous conditions or depending on the pH are extremely rare. However, for applications under biological conditions in water, knowledge about the photochemistry under these is critical. Here, we studied the pH-dependent reaction dynamics of para-hydroxyphenacyl (pHP), one prominent example of PPGs, by ultrafast transient absorption spectroscopy and quantum chemical simulation. At neutral pH, the para-hydroxyl group of pHP is protonated and photoproduct formation occurs within less than 1 ns from a triplet state. At basic pH, the main scaffold gets deprotonated leading to a bathochromic shift of the characteristic absorption. Upon deprotonation the substrate release occurs directly from a singlet state, shortcutting the rate determining step of intersystem crossing (ISC) in the neutral case, resulting in an acceleration of the photochemical reaction with photoproduct formation observed at ∼1 ps.

V. Tkachenko, T. Wu, A. Heraji Esfahani, J. Gurke, M. Hartlieb

Choice of photo-excitation conditions in xanthate-supported photo-iniferter (XPI) RAFT polymerization

Polym. Chem., 2025, Advance Article

The use of photo-controlled reversible deactivation radical polymerization (RDRP) techniques offers several advantages regarding the control of polymerization processes and material synthesis. Reversible addition-fragmentation chain-transfer (RAFT) polymerization is particularly interesting in this context as the chain transfer agent (CTA) used in these processes can be activated by light directly in a photo-iniferter (PI) process. We have recently introduced a method where a xanthate (a particularly active iniferter) is combined with a second CTA resulting in a xanthate supported (X)PI-RAFT process. Herein conducted DFT calculations suggest a significant difference in orbital contributions to the β-scission process when comparing xanthates and trithiocarbonates (TTC), offering an explanation for the improved performance of xanthate. Experimentally, we investigate how the choice of wavelength, light intensity and irradiation setup influences the control over the polymerization and in particular its livingness (end group fidelity). This is probed via the synthesis of multiblock and diblock copolymers where livingness is essential and can be accessed via deconvolution of the SEC traces. While a change in wavelength to more selectively activate the xanthate while not exciting the π-π* transition of the TTC does not seem to improve livingness, the light intensity was found to have a tremendous impact, with oversaturation being detrimental for chain end fidelity. Also using a flow-chemistry setup did not help to overcome this limitation. As such, the choice of light intensity was isolated as a tremendously important factor in XPI-RAFT polymerization.

C. Henkel

Quantum borderlines – Fluctuation energies in ultracold Bose gases

Europhysics Letters, 150, 56001, 2025

Ultracold Bose gases are many-body systems with well-defined particle interactions that may serve as models for interacting quantum fields. The impact of virtual excitations is studied in the spatial transition zone created by a soft confinement potential that separates a degenerate ideal gas from a dense quasi-condensate. We compute within Bogoliubov theory the contribution of quasi-particles to the surface energy at zero temperature.

M. Reifarth, M. Sperling, R. Grobe, P. Akarsu, F. Schmitt, M. Schmette, S. Tank, K. M. Arndt, S. Chiantia, M. Hartlieb, A. Böker

Regioselective and Anisotropic Multi-Patching of Small Microparticles via a Polymer Brush-Assisted Microcontact Printing (µCP)

Advanced Functional Materials, 2025, 2423495

A method for fabricating anisotropic monodisperse silicon dioxide (SiO₂) patchy microspheres is developed. In the protocol, we utilize a modified microcontact printing (µCP) technique, employing a polydimethylsiloxane (PDMS) elastomer with a regularly grooved surface topography as a stamp. The stamp's microscale channels create a confined environment for the SiO₂ microspheres, as they match the particle dimensions (≈4 µm). The solid-phase µCP routine allows for the transfer of functional trialkoxysilanes from the stamp to the particles exclusively at their contact faces. By applying a second stamp to the exposed side of the particles, a fourth patch with different chemical information is added, resulting in particles with four equidistant patches along the particle equator. This fabrication process, compatible with a manifold follow-up chemistry, adds patches with adjustable characteristics. Consequently, a polymeric material containing the nucleobase adenine, is successfully added to the patches, which enables interactions with materials that possess its complementary base uracil. The method is suitable to fabricate particles possessing a C_4v and C_2v symmetry. Importantly, the protocol is easily adaptable to other particle dimensions and surface chemistry, possessing significant potential in the field of anisotropically functionalized spherical colloidal particles.

M. A. Beres, C. Boyer, M. Hartlieb, D. Konkolewicz, G. G. Qiao, B. S. Sumerlin and S. Perrier

RAFT with Light: A User Guide to using Thiocarbonylthio Compounds in Photopolymerizations

ACS Polymers Au 2025, 5, 3, 184–213

This perspective offers an in-depth guide to photopolymerizations mediated with thiocarbonylthio compounds, with a particular focus on photoiniferter and photoinduced energy/electron transfer RAFT (PET-RAFT) polymerizations, focusing on practical considerations. It is designed to provide both newcomers and experts with the practical knowledge needed to harness light-mediated polymerizations for innovative applications. The discussion begins with an overview of conventional RAFT polymerization and proceeds to highlight the distinctive advantages of the photomediated processes. The photochemical behavior of thiocarbonylthio compounds, along with the selection of appropriate light wavelengths, is critically examined for its impact on polymerization kinetics and optimization of polymer properties. Key parameters influencing polymerization success─such as catalyst selection, solvent choice, light intensity, and temperature─are explored in detail. The importance of oxygen tolerance and end-group fidelity is also addressed, as these factors are essential for achieving well-defined polymers. Additionally, reactor configurations are reviewed, focusing on the roles of light sources, reactor geometry (batch versus flow systems), and temperature control in optimizing the reaction efficiency. The article concludes by integrating these concepts into a comprehensive framework for optimizing photoiniferter and PET-RAFT polymerizations.

D. Vinci, K. Ridier, F. Qi, F. Ardana-Lamas, P. Zalden, L. Chung Liu, T. Eklund, M. Sielemann Jakobsen, R. Schubert, D. Khakhulin, C. Deiter, N. Bottin, H. Yousef, D. von Stetten, P. Łaski, R. Kamiński, K. N. Jarzembska, R. F. Wallick, T. Stensitzki, R. M. van der Veen, H. Müller-Werkmeister, G. Molnár, D. Xiang, C. Milne, M. Lorenc and Y. Jiang

Capturing ultrafast molecular motions and lattice dynamics in spin crossover film using femtosecond diffraction methods

Nature Communications, 2025, 16, 2043

A comprehensive insight into ultrafast dynamics of photo-switchable materials is desired for efficient control of material properties through light excitation. Here, we study a polycrystalline spin crossover thin film as a prototypical example and reveal the sequential photo-switching dynamics, from local molecular rearrangement to global lattice deformation. On the earliest femtosecond timescale, the local molecular structural rearrangement occurs within a constant unit-cell volume through a two-step process, involving initial Fe−ligand bond elongation followed by ligand rotation. The highly-oriented structure of the nanocrystalline films and the experimental geometry enables resolving the full anisotropic lattice structural dynamics in and out of the sample plane separately. While both molecular switching and lattice heating influence lattice volume, they exert varying degrees of impact at disparate time scales following photoexcitation. This study highlights the opportunities provided by Mega-electron-volt electron and X-ray free electron laser to advance the understanding of ultrafast dynamics of photo-switchable materials.

E. W. Fischer, P. Saalfrank

A theoretical chemistry approach to vibro-polaritonic chemistry with application to infrared spectroscopy and reaction kinetics

Chemical Modelling: Volume 18

The emerging interdisciplinary research field of vibro-polaritonic chemistry exploits the concept of vibrational strong coupling (VSC) to shape chemical reactivity and molecular properties. Vibro-polaritonic chemistry employs optical Fabry–Pérot cavities as a novel light source, which provide access to VSC between confined infrared (IR) radiation modes and molecular (ro)vibrational degrees of freedom. VSC induces the formation of light–matter hybrid states known as vibrational polaritons, which are experimentally characterized by a paradigmatic doublet signature in linear IR spectra. Mechanistically even more intriguing is the experimentally reported observation of VSC-modified ground state chemistry. From a conceptual perspective, vibro-polaritonic chemistry differs from traditional laser-based light–matter interaction scenarios: While the latter commonly rely on a semiclassical approach subject to a classical description of the electromagnetic field, in vibro-polaritonic chemistry the entire light–matter hybrid system is described quantum mechanically. This chapter provides a contemporary overview of vibro-polaritonic chemistry from the perspective of a theoretical chemist. Theoretical concepts extending the common quantum chemical perspective towards molecular interactions with quantized cavity radiation fields are presented in an introductory fashion. Applications to linear IR spectroscopy and reaction kinetics in the VSC regime are illustratively discussed for selected model problems.