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| Open AccessMonolithic thin-film lithium niobate broadband spectrometer with one nanometre resolution
A framework to break the inherent trade-off barrier between spectral resolution and operational bandwidth of integrated optical spectrometers is developed and demonstrated on thin-film lithium niobate without sacrificing the compact footprint.
- Giovanni Finco
- , Gaoyuan Li
- & Rachel Grange
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Article
| Open AccessUnified picture of vibrational relaxation of OH stretch at the air/water interface
Using femtosecond time-resolved heterodyne-detected vibrational sum-frequency generation spectroscopy the authors determine the vibrational relaxation (T1) time of the O-H stretch at the air/water interface by observing the decay of excited-state OH signals, providing a comprehensive picture of the interfacial vibrational relaxation process of water.
- Woongmo Sung
- , Ken-ichi Inoue
- & Tahei Tahara
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Article
| Open AccessMid-infrared supermirrors with finesse exceeding 400 000
The researchers showcase all-crystalline and hybrid mid-infrared supermirrors with the lowest optical losses ever demonstrated in this wavelength range, representing an unprecedented improvement over any existing mirrors made with any production technology.
- Gar-Wing Truong
- , Lukas W. Perner
- & Garrett D. Cole
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Article
| Open AccessDynamic construction of refractive index-dependent vibrations using surface plasmon-phonon polaritons
Molecular vibrations serve as valuable signatures for the constituent elements and bonding in compounds. Here, using Surface-Enhanced Infrared Absorption spectroscopy, the authors study refractive index dependent vibrations of surface phonon polaritons and surface plasmon platform, targeting dynamic biomonitoring.
- Hong Zhou
- , Zhihao Ren
- & Chengkuo Lee
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Article
| Open AccessVisualizing moiré ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe2 structures
Recent experiments have shown the formation of ferroelectric domains in twisted van der Waals bilayers. Here, the authors report near-field infrared nano-imaging and nano-photocurrent measurements to investigate ferroelectricity in minimally twisted WSe2 by visualizing the plasmonic and photo-thermoelectric response of an adjacent graphene monolayer.
- Shuai Zhang
- , Yang Liu
- & D. N. Basov
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Article
| Open AccessInfrared spectroscopic laser scanning confocal microscopy for whole-slide chemical imaging
Chemical imaging, including infrared spectroscopic microscopy with molecular sensitivity, is useful for label-free biomedical analyses, but is limited by slow speed and poor image quality. Here, the authors design a fast mid-infrared microscope with low noise and high spatial resolution for high-throughput imaging of whole slides.
- Kevin Yeh
- , Ishaan Sharma
- & Rohit Bhargava
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Article
| Open AccessDual-comb optomechanical spectroscopy
Spectroscopic gas sensing with high sensitivity and selectivity finds an increasing number of applications. Here, the authors report an approach to ultrasensitive multiplexed gas sensing by integrating dual-comb spectroscopy with cavity optomechanics.
- Xinyi Ren
- , Jin Pan
- & Heping Zeng
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Article
| Open AccessOver-coupled resonator for broadband surface enhanced infrared absorption (SEIRA)
Nanoresonator is proven to be an excellent platform for molecular detection, yet a set of them is necessary to identify a molecule fingerprint. Here, the authors utilise low quality resonators with large radiative losses, despite its lower quality factor, to identify molecular absorption spectrum between 5 and 10 μm.
- Laura Paggi
- , Alice Fabas
- & Patrick Bouchon
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Article
| Open AccessHigh-speed scanless entire bandwidth mid-infrared chemical imaging
The authors present a fast mid-infrared hyperspectral chemical imaging technique that uses chirped pulse upconversion of sub-cycle pulses at the image plane, with lateral resolution of 15 µm and an adjustable field of view and large spectral range. They demonstrate identification and mapping different components in a microfluidic device, plant cell, and mouse embryo.
- Yue Zhao
- , Shota Kusama
- & Takao Fuji
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Article
| Open AccessTriboelectric-induced ion mobility for artificial intelligence-enhanced mid-infrared gas spectroscopy
Isopropyl alcohol can play a significant role in anti-virus diagnosis but generally yields limited response in conventional detection. Here, authors propose a methodology of AI-enhanced ion mobility and mid-infrared spectroscopy for accurate gas identification despite presence different carbon-based gases.
- Jianxiong Zhu
- , Shanling Ji
- & Chengkuo Lee
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Article
| Open AccessTwo-dimensional infrared-Raman spectroscopy as a probe of water’s tetrahedrality
Direct spectroscopic probes of the impact of structure on dynamical processes in liquids remain scarce. Here, the authors use molecular dynamics simulations to show that the correlation between vibrational coupling and the local tetrahedral structure of liquid water can be studied via hybrid terahertz- and infrared-Raman spectroscopy.
- Tomislav Begušić
- & Geoffrey A. Blake
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Article
| Open AccessVibrational signature of hydrated protons confined in MXene interlayers
Intercalation of protons in 2D materials plays a major role for several applications in energy storage and conversion. Here, the authors show that protons intercalated in Ti3C2Tx MXene interlayer during electrochemical cycling have a different hydration structure than protons in bulk water.
- Mailis Lounasvuori
- , Yangyunli Sun
- & Tristan Petit
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| Open AccessMid-infrared cross-comb spectroscopy
The authors introduce and demonstrate cross-comb spectroscopy in the mid-infrared as a variant of dual-comb spectroscopy. It provides enhanced performance and allows mid-infrared spectral information to be obtained by near-infrared detection.
- Mingchen Liu
- , Robert M. Gray
- & Alireza Marandi
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Article
| Open AccessDual-comb optical activity spectroscopy for the analysis of vibrational optical activity induced by external magnetic field
Dual-comb spectroscopy was first applied to the measurement of magnetic optical activity spectroscopy, realizing Doppler-limited gas-phase molecular analysis, and was further extended to the rapid measurement of liquid-phase chiroptical activity.
- Daowang Peng
- , Chenglin Gu
- & Wenxue Li
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Article
| Open AccessMolecular polariton electroabsorption
The authors investigate whether strong light-matter coupling can alter the nonlinear optical response of molecules inside a microcavity. Focusing on electroabsorption as a model third order nonlinearity, they find that apparent discrepancies between experiment and classical transfer matrix modeling arise from dark states in the system and are not a sign of new physics in the strong coupling regime.
- Chiao-Yu Cheng
- , Nina Krainova
- & Noel C. Giebink
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| Open AccessBond-selective intensity diffraction tomography
The authors introduce Bond-selective Intensity Diffraction Tomography, a computational mid-infrared photothermal microscopy technique based on a standard bright-field microscope and an add-on pulsed light source. It recovers both mid-infrared spectra and bond-selective 3D refractive index maps based on intensity-only measurements.
- Jian Zhao
- , Alex Matlock
- & Ji-Xin Cheng
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Article
| Open AccessThe coupling of the hydrated proton to its first solvation shell
The Zundel [H(H2O)2]+ and Eigen [H(H2O)4]+ cations exhibit radicallly different infrared spectra and are the limiting dynamical structures involved in proton mobility in liquid water. Here, the authors find through quantum dynamics simulations that two polarized water molecules and a proton suffice to explain the key spectroscopic features connected to proton mobility for both species.
- Markus Schröder
- , Fabien Gatti
- & Oriol Vendrell
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Article
| Open AccessSub-optical-cycle light-matter energy transfer in molecular vibrational spectroscopy
Energy transfer between the electromagnetic field and atoms or molecules is fundamentally interesting. Here the authors demonstrate stepwise energy transfer between broadband mid-infrared optical pulses and vibrating methylsulfonylmethane molecules in aqueous solution.
- Martin T. Peschel
- , Maximilian Högner
- & Ioachim Pupeza
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Article
| Open AccessInsight into the transient inactivation effect on Au/TiO2 catalyst by in-situ DRIFT and UV–vis spectroscopy
A molecular-level understanding of the Au-catalyzed CO oxidation on a fast time-resolved scale is still lacking. Here the authors monitor the rapid dynamic changes during CO oxidation over Au/TiO2 using in situ DRIFTS and UV-Vis spectroscopy, and reveal that the catalyst undergoes a surprising structural change at the beginning of the reaction.
- Xianwei Wang
- , Arnulf Rosspeintner
- & Thomas Bürgi
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| Open AccessA mid-infrared lab-on-a-chip for dynamic reaction monitoring
Rapid investigation of chemical reactions is a challenge in bio-medical analysis. Here, the authors demonstrate sensitive in-situ real-time reaction-monitoring of conformational changes in protein solution, based on a fingertip-sized mid-IR lab-on-a-chip.
- Borislav Hinkov
- , Florian Pilat
- & Gottfried Strasser
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Article
| Open AccessSpectral signatures of excess-proton waiting and transfer-path dynamics in aqueous hydrochloric acid solutions
The spectroscopic signatures of excess protons in HCl solutions are studied by ab initio simulations and THz experiments. Two contributions beyond the normal-mode scenario are identified that reflect proton-waiting and proton-transfer processes.
- Florian N. Brünig
- , Manuel Rammler
- & Roland R. Netz
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Article
| Open AccessWavelength-multiplexed hook nanoantennas for machine learning enabled mid-infrared spectroscopy
Infrared spectroscopy with plasmonic nanoantennas is limited by small overlap between molecules and hot spots, and sharp resonance peaks. The authors demonstrate spectral multiplexing of hook nanoantennas with gradient dimensions as ultrasensitive vibrational probes in a continuous ultra-broadband region and utilize machine learning for enhanced sensing performance.
- Zhihao Ren
- , Zixuan Zhang
- & Chengkuo Lee
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Article
| Open AccessRapid age-grading and species identification of natural mosquitoes for malaria surveillance
Knowing the age of malaria-transmitting mosquitoes is important to understand transmission risk as only old mosquitoes can transmit the disease. Here, the authors develop a method based on mid-infrared spectra of mosquito cuticle that can rapidly identify the species and age class of main malaria vectors.
- Doreen J. Siria
- , Roger Sanou
- & Francesco Baldini
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Article
| Open AccessUltrafast infrared nano-imaging of far-from-equilibrium carrier and vibrational dynamics
Ultrafast infrared nano-imaging has enabled the study of nanoscale dynamics, but has been limited to probing short-lived carrier lifetimes. Here, the authors present pump-probe nano-spectroscopy with enhanced sensitivity to image both carrier and vibrational dynamics associated with long-lived excitations.
- Jun Nishida
- , Samuel C. Johnson
- & Markus B. Raschke
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Article
| Open AccessNanosecond-resolution photothermal dynamic imaging via MHZ digitization and match filtering
Photothermal microscopy is limited for imaging of thermal dynamics. Here, the authors introduce a lock-in free, mid-infrared photothermal dynamic imaging system, which significantly increases SNR and imaging speed, and demonstrate metabolism analysis at single-cell level and background removal.
- Jiaze Yin
- , Lu Lan
- & Ji-Xin Cheng
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Article
| Open AccessBiomimetic CO oxidation below −100 °C by a nitrate-containing metal-free microporous system
CO oxidation is of importance both for inorganic and living systems. Here the authors demonstrate that CO can be oxidized by nitrate in small-pore SSZ-13 zeolite at a temperature below −100 °C using spectroscopy and density functional theory calculations.
- Konstantin Khivantsev
- , Nicholas R. Jaegers
- & Janos Szanyi
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Article
| Open AccessThrough bonds or contacts? Mapping protein vibrational energy transfer using non-canonical amino acids
Vibrational energy transfer (VET) is essential for protein function as it is responsible for efficient energy dissipation in reaction sites and is linked to pathways of allosteric communication. Here authors equipped a tryptophan zipper with a VET injector and a VET sensor for femtosecond pump probe experiments to map the VET.
- Erhan Deniz
- , Luis Valiño-Borau
- & Jens Bredenbeck
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Article
| Open AccessProbing subwavelength in-plane anisotropy with antenna-assisted infrared nano-spectroscopy
s-SNOM is a powerful tool, but it is less sensitive to in-plane variations. Here the authors present a method to improve this with a metallic microdisk antenna, which they demonstrate by probing in-plane phonon responses.
- Ziheng Yao
- , Xinzhong Chen
- & Mengkun Liu
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Article
| Open AccessThe molecular pH-response mechanism of the plant light-stress sensor PsbS
Photosystem II subunit S (PsbS) senses thylakoid lumen acidification when plants are exposed to excess light. Here the authors use NMR and IR spectroscopy to show that low pH causes repositioning of an amphipathic helix and folding of a loop involving critical pH sensing glutamate residues in PsbS.
- Maithili Krishnan-Schmieden
- , Patrick E. Konold
- & Anjali Pandit
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Article
| Open AccessProximity control of interlayer exciton-phonon hybridization in van der Waals heterostructures
Here, the authors demonstrate proximity-controlled strong-coupling between Coulomb correlations and lattice dynamics in neighbouring van der Waals materials (WSe2 and a gypsum layer), creating electrically neutral hybrid exciton-phonon eigenmodes called excitonic Lyman polarons.
- Philipp Merkl
- , Chaw-Keong Yong
- & Rupert Huber
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Article
| Open AccessStability of person-specific blood-based infrared molecular fingerprints opens up prospects for health monitoring
Health status transitions are reflected as characteristic changes in molecular composition of biofluids. Here, the authors apply infrared molecular fingerprinting and reveal that blood-based phenotypes are sufficiently stable over time, providing the basis for time- and cost-effective health monitoring.
- Marinus Huber
- , Kosmas V. Kepesidis
- & Mihaela Žigman
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Article
| Open AccessUnravelling the structural complexity of glycolipids with cryogenic infrared spectroscopy
Glycolipids are glycoconjugates with important biological functions, but techniques for their analysis are deficient. Here, the authors report the use of cryogenic gas-phase infrared spectroscopy to investigate isomerism in a set of immunologically relevant glycolipids, and show that their structural features can be accurately resolved based on a narrow spectral fingerprint region.
- Carla Kirschbaum
- , Kim Greis
- & Kevin Pagel
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Article
| Open AccessGiant topological longitudinal circular photo-galvanic effect in the chiral multifold semimetal CoSi
Quantized circular photogalvanic effect (CPGE) is predicted in chiral topological semimetals, but the experimental observation remains challenging. Here, Ni et al. observe a large topological longitudinal photocurrent in CoSi, which is much larger than the photocurrent in any other chiral crystals, indicating quantized CPGE within reach upon doping and increase of the hot-carrier lifetime.
- Zhuoliang Ni
- , K. Wang
- & Liang Wu
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Article
| Open AccessObservation of nanoscale opto-mechanical molecular damping as the origin of spectroscopic contrast in photo induced force microscopy
Existing high-dimensional optical imaging techniques that record space and polarization cannot detect the photon’s time of arrival due to the limited speeds of electronic sensors. Here, the authors develop a single-shot ultrafast imaging modality to record light-speed high-dimensional events with picosecond resolution.
- Mohammad A. Almajhadi
- , Syed Mohammad Ashab Uddin
- & H. Kumar Wickramasinghe
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| Open AccessProbing the heterogeneous structure of eumelanin using ultrafast vibrational fingerprinting
Eumelanin protects cells from sun damage and is promising for energy conversion applications, but its structure and excited state dynamics are elusive. Here the authors shed light on both aspects combining selective excitation of UV- and visible-absorbing chromophores with time-resolved infrared spectroscopy.
- Christopher Grieco
- , Forrest R. Kohl
- & Bern Kohler
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| Open AccessSubsurface chemical nanoidentification by nano-FTIR spectroscopy
Nano-FTIR spectroscopy allows chemical characterization of composite surfaces, but its capability in subsurface analysis is not much explored. The authors show that spectra from thin surface layers differ from those of subsurface layers of the same organic material, and establish a method for distinguishing them in experiments.
- Lars Mester
- , Alexander A. Govyadinov
- & Rainer Hillenbrand
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| Open AccessClosed-loop atomic force microscopy-infrared spectroscopic imaging for nanoscale molecular characterization
Atomic force microscopy-infrared (AFM-IR) spectroscopic imaging techniques offer a non-perturbative, molecular contrast for characterization of nanomaterials; however, data are often complicated by the measurement apparatus, sample preparation conditions and low signal-to-noise ratio. Here, the authors demonstrate a closed-loop controlled AFM-IR instrument design to address measurement artifacts and reduce noise up to 5x compared to previous methods.
- Seth Kenkel
- , Shachi Mittal
- & Rohit Bhargava
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Article
| Open AccessSingle molecule secondary structure determination of proteins through infrared absorption nanospectroscopy
While infrared nanospectroscopy methods based on thermomechanical detection (AFM-IR) enables the acquisition of absorption spectra at the nanoscale, single molecule detection has not been possible so far. Here, the authors present off-resonance, low power and short pulse infrared nanospectroscopy (ORS-nanoIR), which allows measuring infrared absorption spectra at the single molecule level in a time scale of seconds with high throughput and demonstrate that the secondary structure of single protein molecules can be determined with this method.
- Francesco Simone Ruggeri
- , Benedetta Mannini
- & Tuomas P. J. Knowles
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Article
| Open AccessA self-operating broadband spectrometer on a droplet
Compact spectrometers can be useful in many applications and many sophisticated architectures have been proposed. In this work, the authors show that with an evaporating droplet on a fiber tip, spectrometry can be robustly and accurately performed with a simple and passive microfluidic system.
- P. Malara
- , A. Giorgini
- & G. Gagliardi
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Article
| Open AccessThe optical conductivity of few-layer black phosphorus by infrared spectroscopy
For many two-dimensional semiconductors, such as MoS2, the exciton absorption increases with thickness. Here, the authors show that, in black phosphorus, less material absorbs more light due to exciton resonances.
- Guowei Zhang
- , Shenyang Huang
- & Hugen Yan
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Article
| Open AccessSpectroscopic-network-assisted precision spectroscopy and its application to water
Precision-spectroscopy techniques can accurately measure lines in constrained frequency and intensity ranges. The authors propose a spectroscopic-network-assisted precision spectroscopy method by which transitions measured in a narrow range provide information in other, extended regions of the spectrum.
- Roland Tóbiás
- , Tibor Furtenbacher
- & Wim Ubachs
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Article
| Open AccessPolycyclic aromatic hydrocarbon formation chemistry in a plasma jet revealed by IR-UV action spectroscopy
Polycyclic aromatic hydrocarbons (PAHs) are present in the interstellar medium but their origin is unclear. Here the authors investigate large PAH formation from smaller PAHs in a plasma jet by mass-selective IR and UV laser spectroscopy, uncovering diacetylene radical addition as formation mechanism.
- Alexander K. Lemmens
- , Daniël B. Rap
- & Anouk M. Rijs
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Article
| Open AccessQuadruple bonding between iron and boron in the BFe(CO)3− complex
While main group elements possess four valence orbitals that are accessible for bonding, quadruple bonding to main group elements is very rarely observed. Here the authors report that boron is able to form four bonding interactions with iron in the BFe(CO)3- anion complex.
- Chaoxian Chi
- , Jia-Qi Wang
- & Jun Li
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Article
| Open AccessComplementary vibrational spectroscopy
Generally infrared and Raman spectroscopic methods are needed to study the symmetric and asymmetric molecular vibrational modes. Here the authors demonstrate complementary vibrational spectroscopy to organic molecules by simultaneously measuring their symmetric and anti-symmetric vibrations with one setup.
- Kazuki Hashimoto
- , Venkata Ramaiah Badarla
- & Takuro Ideguchi
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Article
| Open AccessInfrared-pump electronic-probe of methylammonium lead iodide reveals electronically decoupled organic and inorganic sublattices
It has been challenging to probe whether dynamically disordered organic cations affect optical properties of CH3NH3PbI3. Here, Guo et al. employ infrared-pump electronic-probe spectroscopy and show that pump-induced atomic motions of the organic cations do not substantially alter optoelectronic properties.
- Peijun Guo
- , Arun Mannodi-Kanakkithodi
- & Richard D. Schaller
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Article
| Open AccessVibrational fingerprint of localized excitons in a two-dimensional metal-organic crystal
Long-lived excitons in a two-dimensional metal-organic crystal can be produced by visible light and detected by infrared radiation. Here, the authors show that the excitonic state of a biomimetic macrocycle can be ‘read’ by measuring the vibrations of an adsorbed ligand.
- M. Corva
- , A. Ferrari
- & E. Vesselli
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Article
| Open AccessUnravelling the structure of glycosyl cations via cold-ion infrared spectroscopy
Glycosyl cations are key intermediates in glycosylation reactions, but their structure has remained elusive due to their transient nature. Here, the authors perform an in-depth structural analysis and report that C2-participating protective groups induce acetoxonium cations with distinct ring conformations.
- Eike Mucha
- , Mateusz Marianski
- & Kevin Pagel
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Article
| Open AccessSounding-rocket microgravity experiments on alumina dust
Alumina is thought to be the main condensate to form in the gas outflow from oxygen-rich evolved stars. Here, the authors perform a condensation experiment with alumina in a low-gravity environment, and find spectroscopic evidence for a sharp feature at a wavelength of 13.55 μm.
- Shinnosuke Ishizuka
- , Yuki Kimura
- & Yuko Inatomi
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Article
| Open AccessTropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance
Large peatlands exist at high latitudes because flooded conditions and cold temperatures slow decomposition, so the presence of (sub)tropical peat is enigmatic. Here the authors show that low-latitude peat is preserved due to lower carbohydrate and greater aromatic content resulting in chemical recalcitrance.
- Suzanne B. Hodgkins
- , Curtis J. Richardson
- & Jeffrey P. Chanton