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A continuous-wave room-temperature maser is demonstrated by combining a cavity with a high Purcell factor with the narrow linewidth of nitrogen–vacancy defect centres in diamond. Maser quest finds ambient solution Laser is an acronym for light amplification by stimulated emission of radiation. 'Light' refers to electromagnetic radiation of any frequency, and devices based on this process were first developed for radiation at microwave and radio frequencies. For historical reasons, these are referred to as 'masers'. Despite being developed first, masers are not widely used as they usually require cryogenic refrigeration and high-vacuum systems. Room-temperature masers made using molecular crystals have poor thermal and mechanical properties and can operate only in pulses. Jonathan Breeze and colleagues now demonstrate a room-temperature maser based on nitrogen–vacancy defect centres in diamond that can operate in continuous-wave mode. Masers are already exploited for deep-space communications and radio astronomy, but this room-temperature device could expand their applications to medicine, security and quantum technologies. The maser—the microwave progenitor of the optical laser—has been confined to relative obscurity owing to its reliance on cryogenic refrigeration and high-vacuum systems. Despite this, it has found application in deep-space communications and radio astronomy owing to its unparalleled performance as a low-noise amplifier and oscillator. The recent demonstration of a room-temperature solid-state maser that utilizes polarized electron populations within the triplet states of photo-excited pentacene molecules in a p -terphenyl host 1 , 2 , 3 paves the way for a new class of maser. However, p -terphenyl has poor thermal and mechanical properties, and the decay rates of the triplet sublevel of pentacene mean that only pulsed maser operation has been observed in this system. Alternative materials are therefore required to achieve continuous emission: inorganic materials that contain spin defects, such as diamond 4 , 5 , 6 and silicon carbide 7 , have been proposed. Here we report a continuous-wave room-temperature maser oscillator using optically pumped nitrogen–vacancy defect centres in diamond. This demonstration highlights the potential of room-temperature solid-state masers for use in a new generation of microwave devices that could find application in medicine, security, sensing and quantum technologies.

The characteristic relaxation and dephasing times of the electronic spins in thin-film copper phthalocyanine are long enough that this common, low-cost organic semiconductor has potential for both quantum and classical information processing. New materials for spintronics Spintronics devices, which exploit the intrinsic spin of electrons as well as their charge, require precise control and read-out of electron spins. For organic semiconductors to find use in spintronic applications, it is desirable to identify molecules that possess long spin relaxation times. This paper establishes that copper phthalocyanine, a blue pigment commonly used in paints and dyes, appears to satisfy this requirement. It is inexpensive and can be easily processed into a thin-film form of the type used for device fabrication, making it a candidate material system for spin-based quantum information processing and other spintronic applications. Organic semiconductors are studied intensively for applications in electronics and optics 1 , and even spin-based information technology, or spintronics 2 . Fundamental quantities in spintronics are the population relaxation time ( T 1 ) and the phase memory time ( T 2 ): T 1 measures the lifetime of a classical bit, in this case embodied by a spin oriented either parallel or antiparallel to an external magnetic field, and T 2 measures the corresponding lifetime of a quantum bit, encoded in the phase of the quantum state. Here we establish that these times are surprisingly long for a common, low-cost and chemically modifiable organic semiconductor, the blue pigment copper phthalocyanine 3 , in easily processed thin-film form of the type used for device fabrication. At 5 K, a temperature reachable using inexpensive closed-cycle refrigerators, T 1 and T 2 are respectively 59 ms and 2.6 μs, and at 80 K, which is just above the boiling point of liquid nitrogen, they are respectively 10 μs and 1 μs, demonstrating that the performance of thin-film copper phthalocyanine is superior to that of single-molecule magnets over the same temperature range 4 . T 2 is more than two orders of magnitude greater than the duration of the spin manipulation pulses, which suggests that copper phthalocyanine holds promise for quantum information processing, and the long T 1 indicates possibilities for medium-term storage of classical bits in all-organic devices on plastic substrates.

Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, we achieve selective oxygen (O 2 ) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3 d orbitals of isolated copper (Cu) sites. Operando X-ray absorption spectroscopy, electron paramagnetic resonance and density-functional theory simulations are used to demonstrate that a [Cu(I)O 2 ] 3− site selectively adsorbs molecular O 2 , forming a rarely reported electrophilic η 2 -O 2 species at 298 K. Assisted by neighbouring Ce(III) cations, η 2 -O 2 is finally reduced to two O 2− , that create two Cu–O–Ce oxo-bridges at 453 K. The isolated Cu(I)/(II) sites are ten times more active in CO oxidation than CuO clusters, showing a turnover frequency of 0.028 ± 0.003 s −1 at 373 K and 0.01 bar P CO . The unique electronic structure of [Cu(I)O 2 ] 3− site suggests its potential in selective oxidation. Precise control over the energy of atomic metal sites is key to unlocking novel reaction pathways. Here, the authors achieve selective oxygen activation by the isolated copper site on ceria, due to its reduced 3 d orbital energy via cerium induced electron withdrawing effect.

The valorization of advanced biorefinery lignins remains a significant challenge, owing to the presence of residual carbohydrates. These lignin-associated carbohydrates hinder lignin purification, reduce its homogeneity, and complicate chemical modifications, ultimately limiting the efficient conversion of lignin into high-value products such as chemicals and materials. This study presents a protic ionic liquid-based lignin fractionation process developed using softwood biomass. Triethylammonium methane sulfonate ([N222H][OMS]) was used to fractionate Pinus sylvestris, yielding two distinct fractions: a low-molecular-weight lignin fraction (LF) and a high-molecular-weight lignin fraction (HF). The extracted fractions were comprehensively characterized using nuclear magnetic resonance (NMR) to quantify changes in interunit linkages (β-O-4, β-5, and β-β) and hydroxyl group distribution, whereas methanolysis gas chromatography/mass spectrometry (GC/MS) was used to quantify residual carbohydrates. The fractionation process achieved LF and HF yields of approximately 70.32% and 17.58%, respectively. Further analysis revealed that the HF contained 59.92 ± 2.12 mg/g carbohydrates, whereas the LF contained only 27.37 ± 1.13 mg/g. These findings underscore the effectiveness of the protic ionic liquid fractionation process in reducing carbohydrate impurities and enhancing lignin purity, paving the way for the more efficient utilization of lignin in value-added applications.

Lipid droplet (LD) function relies on proteins partitioning between the endoplasmic reticulum (ER) phospholipid bilayer and the LD monolayer membrane to control cellular adaptation to metabolic changes. It has been proposed that these hairpin proteins integrate into both membranes in a similar monotopic topology, enabling their passive lateral diffusion during LD emergence at the ER. Here, we combine biochemical solvent-accessibility assays, electron paramagnetic resonance spectroscopy and intra-molecular crosslinking experiments with molecular dynamics simulations, and determine distinct intramembrane positionings of the ER/LD protein UBXD8 in ER bilayer and LD monolayer membranes. UBXD8 is deeply inserted into the ER bilayer with a V-shaped topology and adopts an open-shallow conformation in the LD monolayer. Major structural rearrangements are required to enable ER-to-LD partitioning. Free energy calculations suggest that such structural transition is unlikely spontaneous, indicating that ER-to-LD protein partitioning relies on more complex mechanisms than anticipated and providing regulatory means for this trans-organelle protein trafficking. Lipid droplet (LD) function relies on protein partitioning between the endoplasmic reticulum (ER) and LD. The authors show that UBXD8 adopts distinct conformations in both membranes and undergoes structural rearrangements during ER-to-LD partitioning.

Building efficient triplet-harvesting layers for photovoltaic applications requires a deep understanding of the microscopic properties of the components involved and their dynamics. Singlet fission is a particularly appealing mechanism as it generates two excitons from a single photon. However, the pathways of the coupled triplets into free species, and their dependence on the intermolecular geometry, has not been fully explored. In this work, we produce highly ordered dilute pentacene films with distinct parallel and herringbone dimers and aggregates. Using electron paramagnetic resonance spectroscopy, we provide compelling evidence for the formation of distinct quintet excitons in ambient conditions, with intrinsically distinctive electronic and kinetic properties. We find that the ability of quintets to separate into free triplets is promoted in the parallel dimers and this provides molecular design rules to control the triplets, favouring either enhanced photovoltaic efficiency (parallel) or strongly bound pairs that could be exploited for logic applications (herringbone). Singlet fission results in the formation of a pair of triplets, known as a quintet. Here, the authors identify long-lived quintets in dilute pentacene films at room temperature, with lifetimes influenced by intermolecular geometry having implications for the design of triplet-harvesting films.

Element-element bonded multiply charged cationic species are well known as dimers or small cyclic oligomers in the condensed phase. However, the smallest acyclic version, a trinuclear unit possessing greater than a monocationic charge, has remained elusive. Here we introduce a bis(phosphine) supported low valent triantimony-based tricationic compound as a new entrant in this field. Structural elucidation and electronic understanding reveal a W-shaped tricationic unit comprising of a three-center four-electron sigma-bonded triantimony moiety that is terminally capped by bis(phosphine) ligands, with the central antimony atom having two lone pairs of electrons. The unique counter trianion [Sb(O) 2 (OTf) 4 ] 3– (OTf = CF 3 SO 3 ) possesses reactive polar Sb δ+ –O δ– bonds, the structure of which is determined from single crystal X-ray diffraction analysis. The ensemble of reactive molecular fragments found in this highly charged antimony-based compound makes it thermally unstable. Nonetheless, this fully characterized fleeting species shows a diverse reactivity profile, advancing the isolation of various novel antimony compounds, including the formation of a distinct low-valent antimony-cobalt carbonyl cluster. Element-element bonded multiply charged cationic species are well known as dimers or small cyclic oligomers in the condensed phase but the smallest acyclic version, a trinuclear unit possessing greater than a monocationic charge, has remained elusive. Here the authors report a bis(phosphine) supported low valent triantimony-based tricationic compound.

Type 1 pili are the archetypal representative of a widespread class of adhesive multisubunit fibres in Gram-negative bacteria. During pilus assembly, subunits dock as chaperone-bound complexes to an usher, which catalyses their polymerization and mediates pilus translocation across the outer membrane. Here we report the crystal structure of the full-length FimD usher bound to the FimC–FimH chaperone–adhesin complex and that of the unbound form of the FimD translocation domain. The FimD–FimC–FimH structure shows FimH inserted inside the FimD 24-stranded β-barrel translocation channel. FimC–FimH is held in place through interactions with the two carboxy-terminal periplasmic domains of FimD, a binding mode confirmed in solution by electron paramagnetic resonance spectroscopy. To accommodate FimH, the usher plug domain is displaced from the barrel lumen to the periplasm, concomitant with a marked conformational change in the β-barrel. The amino-terminal domain of FimD is observed in an ideal position to catalyse incorporation of a newly recruited chaperone–subunit complex. The FimD–FimC–FimH structure provides unique insights into the pilus subunit incorporation cycle, and captures the first view of a protein transporter in the act of secreting its cognate substrate. Pilus structure of pathogenic E. coli Gram-negative bacteria express appendages known as pili on their outer surfaces that are used for attachment and invasion of host cells. The chaperone–usher pili are assembled at the outer membrane by a periplasmic chaperone and an outer-membrane, pore-forming protein called the usher. Gabriel Waksman and colleagues present a high-resolution crystal structure of the usher (FimD) from uropathogenic Escherichia coli bound to a translocating substrate (FimH adhesin). The structure provides insight into the activation mechanism of an archetypal protein transporter, and may inform the design of drugs capable of disrupting type 1 pilus formation and potentially inhibiting cystitis.