Giuseppe Maria Paternò

Functionalized nanographenes are emerging near-infrared emitters, yet the microscopic pathways underlying their ultrafast excited-state dynamics remain elusive.

Two-dimensional van der Waals materials display rich nonequilibrium physics due to their reduced dimensionality and strong light–matter interactions. Layered metal phosphorus trichalcogenides (MPX3) feature bandgaps spanning the visible to ultraviolet range and exhibit a complex interplay between excitons, phonons, and defects. Here we use static and time-resolved photoluminescence and femtosecond broadband transient reflectivity to investigate the temperature-dependent ultrafast carrier dynamics in layered HgPSe3, a semiconductor with a quasi-direct bandgap near 2 eV. We identify distinct sub-bandgap photoluminescence features that become prominent at low temperature. Their temperature and fluence dependence strongly indicate radiative recombination involving localized states. The transient reflectivity map displays three features associated with interband optical transitions in the visible range, as corroborated by density functional theory band structure calculations. These features exhibit fluence-dependent decay dynamics, indicating a competition between carrier localization into sub-bandgap states, state-filling effects that limit the available electronic phase space for hot-carrier relaxation, and phonon-bottleneck-limited carrier cooling. Our results provide new insights into the ultrafast carrier dynamics of HgPSe3 and establish a framework for understanding the role of sub-bandgap states in MPX3 semiconductors, with potential implications for broadband optoelectronic and photodetection applications.

Electron–phonon (e–ph) interactions govern photoinduced nonequilibrium dynamics of MXenes, determining hot-carrier relaxation and parasitic heat accumulation. However, strategies to deliberately modulate these interactions through chemical control, together with mechanistic understanding, remain underexplored. Here, we demonstrate the effective modulation of nonequilibrium e–ph interactions in Ti ₃ C ₂ T _x MXene via surface-anchored Mo ₃ S ₇ nanoclusters, which introduce a rapid energy harvesting pathway competing with intrinsic e–ph relaxation. Using mild ligand substitution, Mo ₃ S ₇ nanoclusters are densely and homogenously anchored onto Ti ₃ C ₂ T _x via coordination bonding between Mo centers and O-terminations. Femtosecond transient absorption and optical-pump terahertz-probe spectroscopy reveal an ultrafast, sub-100 fs nonthermal electron and/or energy extraction, with efficiency increasing from ~28.6 % at 1.55 eV to ~38.2 % at 3.88 eV. This excitation-energy-dependent enhancement is enabled by improved energetic alignment between hot electrons in Ti ₃ C ₂ T _x and the conduction-band manifold of Mo ₃ S ₇ . The competitive depletion of nonthermal electrons suppresses coherent A _1g phonon excitation, reducing effective e–ph interactions. Our study offers a viable strategy for modulating e–ph interactions in MXenes, advancing hot carrier relaxation and thermal management in next-generation optoelectronic devices.

Membrane‐targeted azobenzenes enable light‐based control of membrane‐associated cellular processes with high spatiotemporal precision. Their reversible trans–cis isomerization provides tunable control over molecular geometry and polarity, which can modulate cell membrane potential‐dependent biological functions. Despite extensive work in eukaryotes, structure–property relationships for membrane‐targeted azobenzenes remain largely unexplored in prokaryotes, where membrane electrostatics and the electrical potential component of the proton motive force are tightly coupled to bioenergetics, metabolism, and adaptive responses, including antibiotic susceptibility. Building on our previous finding that the amphiphilic azobenzene Az‐2Pyr (also known as ZIAPIN2) inserts into bacterial membranes and elicits a light‐driven response distinct from that observed in eukaryotic cells, here we show a comparative study to connect molecular design to photoswitching and bacterial outcomes. We study three amphiphilic azobenzenes with an identical core and a systematic variation in cationic pyridinium arms, from one (Az‐1Pyr) to four (2Pyr‐2Pyr), to probe the roles of charge density and molecular symmetry. We first characterize their optical properties by steady‐state and ultrafast optical spectroscopy, resolving spectral signatures and kinetics of trans–cis photoisomerization. We then quantify bacterial affinity via cellular uptake, lethality, and ζ‐potential. Finally, we show that photoswitching combined with bacterial association modulates antibiotic susceptibility.

Quantitative monitoring of motility in biological microswimmers is an essential instrument for understanding how microorganisms perceive, process, and translate external stimuli into dynamic behavioural responses. However, tactical responses emerge from complex biophysical mechanisms that operate simultaneously at the individual and collective levels, giving rise to intra-population heterogeneity that can be difficult to quantify with population-averaged approaches: when the trajectories of kinematically distinct subgroups are aggregated, coherent responses may appear weak or confused even in the presence of organised subpopulations. In this work, we present a single-cell tracking-based method for the rigorous kinematic characterisation of the phototactic response of Chlamydomonas reinhardtii , with the aim of resolving behavioural variability and its temporal evolution within heterogeneous populations. The workflow integrates automated large-scale tracking, detailed trajectory reconstruction, single-cell and population-level kinematic analysis, segmentation into coherent behavioural subpopulations (stationary, confined/circling, and directional) via clustering in circular feature space, and characterisation of dynamic motion regimes through time-windowed mean squared displacement (MSD) analysis. By explicitly decomposing the population into coherent kinematic components and quantifying their relative contributions, the method provides “behavioural resolution” of mixed phototactic responses. Based exclusively on open-source software and robust mathematical analysis, the method is highly reproducible and easily extendable to the study of other biological or synthetic microswimmers subjected to controlled external stimuli.

Fifteen years after the first optical recordings of fast cell membrane-potential (“Vm”) transients in Escherichia coli using a genetically encoded rhodopsin-based reporter, bacterial bioelectricity has matured from a provocative observation into a quantitative, multi-scale research program. Early work established that bacterial Vm is dynamic and can exhibit spike-like events correlated with rapid ion efflux, suggesting that electrical state participates in regulating transport and stress responses. Subsequent studies revealed that ion channels can mediate long-range electrical communication in Bacillus subtilis biofilms via propagating K ⁺ waves that coordinate metabolic states across millimeter scales. In parallel, theory and experimental work formalized how community heterogeneity and spatial organization determine signal transmission, and how electrical dynamics can influence cell behaviors such as motility and recruitment into biofilms. Most recently, the field has entered a “perturb-and-measure” phase: optical, bioelectronic, and impedance-based platforms now enable controlled stimulation and more mechanistic tests of causality in bacterial electrophysiology, with emerging translational directions in antimicrobial control. Here we review these developments, highlight competing interpretations of bacterial “excitability,” identify key measurement and mechanistic gaps (especially absolute Vm quantification and causal linking to phenotype), and outline future opportunities at the interface of photobiology, bioelectronics, and microbial physiology.

Correction for ‘Electrospun polymeric scaffolds enable 3D tissue-like functionality and efficient photoinduced contraction’ by Giulia Simoncini et al. , J. Mater. Chem. B , 2026, 14 , 2832–2842, https://doi.org/10.1039/D5TB02640G.

Zinc oxide (ZnO) is a wide-band gap semiconductor with high exciton binding energy and is promising for future optoelectronics. Degenerate doping in ZnO quantum dots (QDs) enables tunable localized surface plasmon resonance (LSPR) in the IR region, but its impact on exciton dynamics remains unexplored. Here, we employ transient absorption spectroscopy to probe exciton dynamics in aluminum-doped ZnO (AZO) QDs. Excitation above the band gap generates hot excitons that relax via thermalization, Auger recombination, and stimulated emission, along with band gap renormalization. The presence of free charge carriers in the conduction band (CB) due to degenerate doping screens Coulomb exciton interactions that leads to suppression of biexciton formation and reduction in Auger recombination lifetime. Despite complete bleaching of ground-state absorption, reminiscent of zero-threshold gain in precharged QDs, no optical gain is achieved in AZO QDs due to doping-induced nonradiative pathways. Our findings highlight how the Burstein–Moss (BM) effect shapes exciton dynamics in degenerately doped wide-band gap QDs.

Large polycyclic aromatic hydrocarbon (PAH) imides are promising candidates for optoelectronic applications in view of their narrow optical gaps and/or excited state charge transfer character. Diels–Alder (D–A) reactions of PAHs at bay regions can enable simultaneous extension of the aromatic structure and introduction of the imide moieties, but the actual use of this strategy has been limited. Herein, we demonstrate the D–A cycloaddition of dibenzo[ hi , st ]ovalene, one of the largest PAHs functioning as bisdiene, with maleimides to afford circumpyrene tetracarboxydiimides. Notably, efforts to optimize the yield of di-adduct revealed that the fully aromatized mono-adduct is inert toward further D–A reaction, and density functional theory (DFT) calculations instead indicated a partially dehydrogenated mono-adduct as the key intermediate enabling the second cycloaddition. The resulting product represents a rare example of PAH diimide featuring an acceptor-donor-acceptor type structure. Detailed spectroscopic and theoretical studies, including transient absorption and two-dimensional electronic spectroscopy, revealed the emergence of a bright intramolecular charge transfer state that could be directly excited to demonstrate distinct photophysical dynamics. These findings provide deep mechanistic insights into the D–A reactivity of large PAHs and underscores the potential of such PAH imides for advanced optoelectronic and photonic applications.

Free-standing, aligned electrospun PVA nanofiber membranes create a quasi-3D scaffold for C2C12 alignment. With Ziapin2 infiltration, visible light paces macroscopic contractions up to ∼460 µN (∼3.3 kPa) without genetics in vitro .