Optical spectroscopy

  • Article
    | Open Access

    A complete understanding of singlet fission (SF) in molecular materials will enable the design of optimised optoelectronic devices. Here, the authors use vacancy control in acene-based blends to link coherent and incoherent SF pathways to energetics.

    • Clemens Zeiser
    • , Chad Cruz
    •  & Katharina Broch
  • Article
    | Open Access

    Existing methods for non-invasively monitoring water flow in plants have limited spatial/temporal resolution. Here, the authors report that Raman microspectroscopy, complemented by hydrodynamic modelling, can monitor hydrodynamics within living root tissues at cell- and sub-second-scale resolutions.

    • Flavius C. Pascut
    • , Valentin Couvreur
    •  & Kevin F. Webb
  • Article
    | Open Access

    The authors develop a method to build Manhattan Raman Scattering (MARS) probes based on different core atoms, conjugation ring numbers, and stable isotope substitutions. A quantitative model predicts vibrational frequencies of MARS dyes from structures, which are used in supermultiplexed vibrational imaging.

    • Yupeng Miao
    • , Naixin Qian
    •  & Wei Min
  • Article
    | Open Access

    Currently many of the time resolved serial femtosecond (SFX) crystallography experiments are done with light driven protein systems, whereas the reaction initiation for non-light triggered enzymes remains a major bottle neck. Here, the authors present an expanded Drop-on-Tape system, where picoliter-sized droplets of a substrate or inhibitor are turbulently mixed with nanoliter sized droplets of microcrystal slurries, and they use it for time-resolved SFX measurements of inhibitor binding to lysozyme and secondly, binding of a β-lactam antibiotic to a bacterial serine β-lactamase.

    • Agata Butryn
    • , Philipp S. Simon
    •  & Allen M. Orville
  • Article
    | Open Access

    Frequency-comb-based multiheterodyne spectroscopy requires that total bandwidth of the measured spectrum covers less than half the comb spacing, which is usually not the case for incoherent spectra. Here, the authors propose a technique that lifts this requirement, and demonstrate it in the microwave regime.

    • David J. Benirschke
    • , Ningren Han
    •  & David Burghoff
  • Article
    | Open Access

    Reactions at the interface between mineral surfaces and flowing liquids are ubiquitous in nature. Here the authors explore, using surface-specific sum frequency generation spectroscopy and numeric calculations, how the liquid flow affects the charging and dissolution rates leading to flow-dependent charge gradients along the surface.

    • Patrick Ober
    • , Willem Q. Boon
    •  & Mischa Bonn
  • Article
    | Open Access

    Hybrid perovskite is a promising class of material for optoelectronic applications due to the slow hot-carrier cooling, yet the process is not well-understood in material with Rashba band splitting. Here, the authors reveal spin-flipping and spin-dependent scattering of hot electrons are responsible for accelerating the cooling at longer delays.

    • Jun Yin
    • , Rounak Naphade
    •  & Omar F. Mohammed
  • Article
    | Open Access

    Super-resolution microscopy is often limited by photobleaching or uneven distribution of fluorophores. The authors present a label-free superresolution method termed VISTA, combining sample-expansion and vibrational imaging, with resolution down to 78 nm in protein-rich biological structures in cells and tissues.

    • Chenxi Qian
    • , Kun Miao
    •  & Lu Wei
  • Article
    | Open Access

    Fluorogenic RNA aptamers such as Chili display strong fluorescence enhancement upon aptamer–ligand complex formation. Here, the authors provide insights into the mechanism of fluorescence activation of Chili by solving the crystal structures of Chili with its bound positively charged ligands DMHBO+ and DMHBI+, and they reveal that Chili uses an excited state proton transfer mechanism based on time-resolved optical spectroscopy measurements.

    • Mateusz Mieczkowski
    • , Christian Steinmetzger
    •  & Claudia Höbartner
  • Article
    | Open Access

    Combining magnetic and semiconducting properties in a single material offers great technological potential, all the more so if these are coupled with good optical properties. Here, Neumann et al. present a Manganese doped Ruddlesden-Popper perovskite with this trifecta of attributes.

    • Timo Neumann
    • , Sascha Feldmann
    •  & Felix Deschler
  • Article
    | Open Access

    Tip-enhanced nano-spectroscopy suffers from inconsistent signal and difficulty in polarization-resolved measurement. Here, the authors present adaptive tip-enhanced nano-spectroscopy, which enables the additional signal enhancement and near-field polarization control via dynamic wavefront shaping.

    • Dong Yun Lee
    • , Chulho Park
    •  & Kyoung-Duck Park
  • Article
    | Open Access

    Currently relatively few functional probes for Raman-based live-cell profiling exist. Here the authors build on their previous ultra-bright Raman dots to devise a 14-plexed Raman probe panel to quantify cell surface proteins, endocytosis activities and metabolic dynamics of single live cells.

    • Chen Chen
    • , Zhilun Zhao
    •  & Wei Min
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Probes with reversible fluorescence are useful in super-resolution microscopy, but lack sufficient chemical specificity. Here, the authors engineer alkyne tagged diarylethene to realize photo-switchable stimulated Raman scattering probes with high chemical resolution, for applications in living cells.

    • Jianpeng Ao
    • , Xiaofeng Fang
    •  & Minbiao Ji
  • Article
    | Open Access

    Raman optical activity (ROA) is useful for studying conformational structure and behavior of chiral molecules, but is limited by the weak signals. Here, the authors demonstrate 100x signal enhancement via an all-dielectric approach, using a silicon nanodisk array and exploiting its dark mode.

    • Ting-Hui Xiao
    • , Zhenzhou Cheng
    •  & Keisuke Goda
  • Article
    | Open Access

    Sea urchin hyperpolarization-activated cyclic nucleotide-gated (spHCN) ion channels channels are activated by membrane hyperpolarization instead of depolarization and undergo inactivation with hyperpolarization. Here authors apply transition metal ion FRET, patch-clamp fluorometry and Rosetta modeling to measure differences in the structural rearrangements between activation and inactivation of spHCN channels.

    • Gucan Dai
    • , Teresa K. Aman
    •  & William N. Zagotta
  • Article
    | Open Access

    In situ vibrational spectroscopy affords a powerful tool for probing elementary chemical processes on catalytic surfaces. Using surface enhanced Raman scattering, authors identify an array of multicarbon species formed on a Ag nanoparticle catalyst in plasmon-driven reduction of CO2 in water.

    • Dinumol Devasia
    • , Andrew J. Wilson
    •  & Prashant K. Jain
  • Article
    | Open Access

    The FRET efficiency usually predominantly depends on the proximity of donor and acceptor. Here the authors report an anisotropy-based mode of FRET detection, FRET-induced Angular Displacement Evaluation via Dim donor (FADED), to allow quantification of the relative angle between donor and acceptor.

    • Danai Laskaratou
    • , Guillermo Solís Fernández
    •  & Hideaki Mizuno
  • Article
    | Open Access

    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
  • Article
    | Open Access

    In order to develop perovskite nanocrystals as a single-photon source, there is a need to understand the complex exciton photo-physics. Here, the authors employ resonant and near-resonant excitation technique to study single CsPbI3 nanocrystal that allows them to probe the continuous and size-quantised acoustic-phonon modes.

    • Yan Lv
    • , Chunyang Yin
    •  & Min Xiao
  • Article
    | Open Access

    Optical pulses can be useful to create and control molecules in higher quantum states. Here the authors use optical pumping to create rotationally excited states of SiO+ molecular ion into super rotor ensemble.

    • Ivan O. Antonov
    • , Patrick R. Stollenwerk
    •  & Brian C. Odom
  • Article
    | Open Access

    Here, the authors use a nanoscale probe to study the photoresponse within a single moiré unit cell of minimally twisted bilayer graphene, and observe an intricate photo-thermoelectric response attributed to the Seebeck coefficient variation at AB-BA domain boundaries.

    • Niels C. H. Hesp
    • , Iacopo Torre
    •  & Frank H. L. Koppens
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Aggregation-induced emission (AIE) has proven to be a viable strategy to achieve highly efficient room temperature phosphorescence (RTP) in bulk by restricting molecular motions. Here, the authors present an RTP design strategy by combining the concept of AIE and donor-acceptor motif and demonstrate unusual thermochromic dual phosphorescence.

    • Tao Wang
    • , Zhubin Hu
    •  & Guoqing Zhang
  • Article
    | Open Access

    Raman-based imaging of biomarkers is often challenging due to low sensitivity. Here, the authors use a swelling-diffusion approach to develop a series of Raman probes that are both ultra-bright and compact in size, and demonstrate multiplexed imaging of specific protein targets in cells and tissue slices.

    • Zhilun Zhao
    • , Chen Chen
    •  & Wei Min
  • Article
    | Open Access

    It is currently challenging to identify protein structures at low concentrations. Here the authors report optical tweezers-coupled Raman spectroscopy to generate tunable and reproducible SERS enhancements with single-molecule level sensitivity and use the method to detect protein structural features.

    • Xin Dai
    • , Wenhao Fu
    •  & Jinqing Huang
  • Article
    | Open Access

    Vibronic coupling is a key feature of molecular electronic transitions, but its visualization in real space is an experimental challenge. Here the authors, using scanning tunneling microscopy induced luminescence, resolve the effect of vibronic coupling with different modes on the electron distributions in real space in a single pentacene molecule.

    • Fan-Fang Kong
    • , Xiao-Jun Tian
    •  & J. G. Hou
  • Article
    | Open Access

    There is a clinical need to monitor immune-related toxicities of immune checkpoint blockade therapy. Here, the authors develop a digital SERS platform for multiplexed single cytokine counting to track immune-toxicities and demonstrate the ability to use pre-screening to identify patients at higher risk.

    • Junrong Li
    • , Alain Wuethrich
    •  & Matt Trau
  • Article
    | Open Access

    Fano resonances occur in many platforms that have auto-ionizing states. Here the authors show that auto-ionizing states are not required for multi-photon Fano resonance in a Si:P system with significant screening by using a pump-probe method.

    • K. L. Litvinenko
    • , Nguyen H. Le
    •  & B. N. Murdin
  • Article
    | Open Access

    Here the authors report spectroscopy and dynamics of cavity coupled NO band of sodium nitroprusside using 2D infrared and transient spectroscopy employing pump-probe technique. They find signatures of third-order nonlinearity, incoherent and strong coupling effects of vibrational polaritons.

    • Andrea B. Grafton
    • , Adam D. Dunkelberger
    •  & Jeffrey C. Owrutsky
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Identification of neurotransmitters remains challenging for surface enhanced Raman spectroscopy (SERS) due to presence of noise. Here, the authors present spread spectrum SERS, which by encoding excited light and decoding SERS signals enables detection of unlabelled neurotransmitters at attomolar concentrations.

    • Wonkyoung Lee
    • , Byoung-Hoon Kang
    •  & Ki-Hun Jeong
  • Article
    | Open Access

    Raman spectroscopic imaging (RSI) can provide information on the chemical composition of a sample, but application to living organisms has lacked sufficient spatial resolution and signal strength. Here the authors apply confocal RSI to whole-mount zebrafish embryos to distinguish different infectious bacteria and to living zebrafish embryos to monitor the wound healing process.

    • Håkon Høgset
    • , Conor C. Horgan
    •  & Molly M. Stevens
  • Article
    | Open Access

    Polymer thin films that emit and absorb circularly polarised light are promising in achieving important technological advances, but the origin of the large chiroptical effects in such films has remained elusive. Here the authors demonstrate that in non-aligned polymer thin films, large chiroptical effects are caused by magneto-electric coupling, not structural chirality as previously assumed.

    • Jessica Wade
    • , James N. Hilfiker
    •  & Matthew J. Fuchter
  • Article
    | Open Access

    The green component of the solar spectrum can efficiently drive natural photosynthesis, but the process has been little investigated due to the complexity of the excited states involved. Here the authors utilize polarization-dependent two-dimensional electronic-vibrational spectroscopy to define the origin and dynamics of these states in light-harvesting complex II.

    • Eric A. Arsenault
    • , Yusuke Yoneda
    •  & Graham R. Fleming