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A study of phase transitions in two-dimensional halide perovskites uncovers distinct thermal and optical pathways through Ginzburg–Landau theory. The work identifies an optically driven metastable tetragonal phase, excited by Higgs phonon modes, offering insights into symmetry-breaking dynamics.

Evidence for exciton coherence in photosynthetic complexes raises questions about whether quantum processes can play a role in biological environments, which are warm and wet. Cassette et al. now demonstrate long-lived electronic coherence in colloidal nanoplatelets in solution and at room temperature.

Dissociation of excitons at the donor/acceptor interface in organic solar cells occurs on fast timescales. Here, the authors apply two-dimensional electronic spectroscopy to study the electron transfer process in a polymer blend, reporting dynamic maps for the charge-transfer pathways.

Perovskite nanocrystal LEDs featuring long-chain ammonium cations offer improved stability and efficiency.

Spectroscopists and theorists are closing in on an understanding of the origin of oscillatory features in the spectral response of light-harvesting complexes to femtosecond pulsed excitation. Now, the photosynthetic Fenna–Matthews–Olson complex is probed by femtosecond pump–probe spectroscopy and compared with a series of genetically modified mutants with distinct excitonic interactions, allowing electronic and vibrational contributions to coherence to be distinguished.

Perovskite crystals of Cs₄PbBr₆ embedded with CsPbBr₃ nanocrystals are shown to act as wideband, achromatic waveplates in the visible and near-infrared regions.

Coherence observed in chemical and biological systems suggests that even in the presence of disorder and noise the phenomenon may yield transformative ways for improving function.

Chloroplasts with extended photosynthetic activity beyond the visible absorption spectrum, and living leaves that perform non-biological functions, are made possible by localizing nanoparticles within plant organelles.

Photosynthesis starts when light is absorbed and the associated excitation energy is directed to reaction centres by antenna complexes. The principles learned from studying these complexes are described in this Review, and provide the framework from which the authors suggest how to elucidate strategies for designing light-harvesting systems that route the flow of energy in sophisticated ways.

Quantum beating has been observed in photosynthetic systems, suggesting that energy-transfer processes in natural light harvesting could involve quantum effects. Now, extensive beating is found in the light-harvesting protein of a cryptophyte alga, and shown to be electronic. The implications of these observations on the free-energy surfaces and exciton delocalization were investigated.

The detailed interplay between electronic and lattice dynamics in two-dimensional perovskite materials remains elusive. Here the authors establish the room-temperature polaronic nature of the excitons in two-dimensional Dion–Jacobson-type perovskites.

Optical spectroscopy based on nonlinear effects usually requires coherent, ultrafast light sources such as femtosecond lasers. Here Turneret al.measure coherent multidimensional optical spectra of molecular systems using incoherent light.

The role of the dielectric environment in thermally activated delayed fluorescence (TADF) is not yet fully understood. Here the authors reveal the relevance of environment–emitter interactions in gating the reverse intersystem crossing and its particular relevance in dipolar TADF emitters.

Spin-triplet energy transfer in molecular systems underlies important applications for chemistry and devices. Here, the authors investigate the triplet energy transfer in CdSe quantum dots with varying ZnS shell thicknesses to surface-anchored anthracene molecules and identify a stepwise mechanism mediated by endothermic charge-transfer states.

The synthesis of a family of plate-like semiconductor nanocrystals yields solutions of small quantum wells with excellent optical properties.

In photosynthesis, the Sun's energy is harvested and converted into biomass, greening the planet. Evidence is growing that quantum mechanics plays a part in that process. But exactly how, and why, remains to be explored.

The formation of weak chemical bonds at or near thermodynamic potential is a challenge in chemical synthesis and catalysis. A bifunctional iridium hydride catalyst has now been discovered that absorbs visible light and promotes proton-coupled electron transfer to a range of substrates—creating element–hydrogen bonds—using dihydrogen as the terminal reductant.

Expanding the biocatalysis toolbox for C–N bond formation is of great value. Now, a biocatalytic amination strategy using a new-to-nature mechanism involving nitrogen-centred radicals has been developed. The transformations are enabled by synergistic photoenzymatic catalysis, providing intra- and intermolecular hydroamination products with high yields and levels of enantioselectivity.

Understanding the photophysical properties of transition-metal complexes is paramount to advances in photocatalysis, solar energy conversion and light-emitting diodes. Now, long-lived emission via thermally activated delayed fluorescence has been demonstrated from an air- and water-stable zirconium complex featuring excited states with significant ligand-to-metal charge transfer character.

Electronic–vibrational interplay can enable electron and energy transfer processes to be regulated. Now, coherence spectroscopy has been used to disentangle two vibrational pathways that control an electron transfer reaction. It has been shown that a fast, effectively ballistic, electron transfer along one vibrational path acts like a pulse to generate a coherent wavepacket along another vibrational pathway.

Evidence is growing that quantum coherence plays a role in photosynthesis. Better understanding of this process might help us design more efficient solar cells to harness the Sun's energy.

How many pairs of electrons and 'missing electrons' can sustain collective motion in a semiconductor? The limits of this electron–hole dance are found by probing the dance floor using ultrashort laser pulses.

Regioselective chemical modification of wild-type proteins remains challenging. Now, by harnessing the varied SOMOphilicity of native tyrosine residues through photoredox catalysis, a site-selective bioconjugation method has been developed. This technology directly incorporates bioorthogonal formyl groups in one step, forming structurally defined fluorescent conjugates that can be rapidly diversified to biorelevant products.

Flavin-dependent ‘ene’-reductases have now been shown to catalyse redox-neutral radical cyclizations of α-haloamides to form enantioenriched oxindoles. Mechanistic studies indicate the reaction proceeds via the flavin semiquinone/quinone redox couple, where a ground state flavin semiquinone provides the electron for substrate reduction and flavin quinone oxidizes the radical formed after cyclization.

To what extent do photosynthetic organisms use quantum mechanics to optimize the capture and distribution of light? Answers are emerging from the examination of energy transfer at the submolecular scale.

Molecular design and synthesis, from small molecules to supramolecular assemblies, combined with new spectroscopic probes of quantum coherence and theoretical modelling, offer a broad range of possibilities to realize practical quantum information science applications in computing, communications and sensing.

Natural photosynthetic systems harvest light to perform selective chemistry on atmospheric molecules such as CO₂. This Review discusses the implementation of bioinspired concepts in engineered light harvesting and catalysis.

Lessons learned from coherent phenomena in biological photosynthetic systems may be useful to improve energy- and charge-transport in disordered materials. This Review describes coherence and its potential beneficial effects in photovoltaics.