Optical spectroscopy

  • Article
    | Open Access

    Although polarized Raman microscopy is sensitive to orientation changes, quantitative information has been missing. Here, the authors use simultaneous registration of multiple Raman scattering spectra obtained at different polarizations and show quantitative orientation mapping

    • Oleksii Ilchenko
    • , Yuriy Pilgun
    •  & Anja Boisen
  • Article
    | Open Access

    Probing inevitable defects in two- dimensional materials is challenging. Here, the authors tackle this issue by using tip-enhanced Raman spectroscopy (TERS) to obtain distinctly different Raman features of edge defects in atomically thin MoS2, and further probe their unique electronic properties as well as identify the armchair and zigzag edges.

    • Teng-Xiang Huang
    • , Xin Cong
    •  & Bin Ren
  • Article
    | Open Access

    Sensing DNA bases by surface-enhanced Raman spectroscopy (SERS) in plasmonic nanopores has suffered from rapid flow through of molecules. Here, the authors attach DNA molecules to gold nanoparticles which, due to electro-plasmonic trapping, allow for controlled residence times and discrimination of single nucleotides.

    • Jian-An Huang
    • , Mansoureh Z. Mousavi
    •  & Francesco De Angelis
  • Article
    | Open Access

    Manipulation of charge carriers is promising for tuning electronic, optical and magnetic properties in two-dimensional materials, but mechanistic details are not fully understood. Here, the authors report that ambient redox reactions govern charge transfer doping in graphene and tungsten disulfide.

    • Kwanghee Park
    • , Haneul Kang
    •  & Sunmin Ryu
  • Article
    | Open Access

    The use of Raman spectroscopy for pathogen identification is hampered by the weak Raman signal and phenotypic diversity of bacterial cells. Here the authors generate an extensive dataset of bacterial Raman spectra and apply deep learning to identify common bacterial pathogens and predict antibiotic treatment from noisy Raman spectra.

    • Chi-Sing Ho
    • , Neal Jean
    •  & Jennifer Dionne
  • Article
    | Open Access

    Nanoconfinement effects on changing molecular transport and reaction kinetics in heterogeneous catalysis have been widely recognized. Here, the authors design a core-shell nanocatalyst with aligned linear nanopores to uncover nanoconfinement effects on catalytic activity and adsorption strength by single molecule imaging.

    • Bin Dong
    • , Yuchen Pei
    •  & Ning Fang
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Weak electron-phonon scattering that can enable long-lived hot electrons in semiconductors is of interest in hot carrier solar cells. Here, the authors report copper-doped colloidal cadmium-selenide quantum dots with hot electron lifetime extended by more than 30-fold compared to undoped dots.

    • Lifeng Wang
    • , Zongwei Chen
    •  & Kaifeng Wu
  • Article
    | Open Access

    In normal dispersion, modulation instability, which is a precursor of Kerr combs, is forbidden due to phase mismatch. Here, the authors show the compensation of such phase mismatch by introducing frequency-dependent loss using a notch filter, hence leading to effective parametric gain and comb formation.

    • Florent Bessin
    • , Auro M. Perego
    •  & Arnaud Mussot
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Ultrafast photo-induced processes in complex systems require theoretical models and their experimental validation which are still lacking. Here the authors investigate singlet fission in a pentacene dimer by a combined experimental and theoretical approach providing a real-time visualisation of the process.

    • Christoph Schnedermann
    • , Antonios M. Alvertis
    •  & Andrew J. Musser
  • Article
    | Open Access

    The speed of surface-enhanced Raman spectroscopy (SERS) imaging is generally limited due to low Raman signals. Here, the authors develop bright gap-enhanced Raman tags with external hot spots and demonstrate their use in fast near-infrared bioimaging.

    • Yuqing Zhang
    • , Yuqing Gu
    •  & Jian Ye
  • Article
    | Open Access

    Coherent anti-Stokes Raman Scattering (CARS) accesses the vibrational properties of a material via nonlinear four-wave mixing (FWM); CARS in graphene has not been observed to date despite its high nonlinear third-order susceptibility. Here, the authors devised a FWM scheme to perform stimulated Raman spectroscopy in single and multi-layer graphene through CARS.

    • A. Virga
    • , C. Ferrante
    •  & T. Scopigno
  • Article
    | Open Access

    Fluorescence correlation spectroscopy is widely used for in vivo and in vitro applications, yet extracting information from experiments still requires long acquisition times. Here, the authors exploit Bayesian non-parametrics to directly analyze the output of confocal fluorescence experiments thereby probing physical processes on much faster timescales.

    • Sina Jazani
    • , Ioannis Sgouralis
    •  & Steve Pressé
  • Article
    | Open Access

    Spin-information transport or transfer is essential for spintronics applications and often relies on high purity and quality materials. Here, the authors report on the defect-tolerant solution-processed Ruddlesden–Popper halide perovskites, where a spin propagation length of 600 nm was achieved via spin funneling.

    • David Giovanni
    • , Jia Wei Melvin Lim
    •  & Tze Chien Sum
  • Article
    | Open Access

    Transition metals are at the basis of key processes in chemistry and biology but their complex electronic structures make understanding of their properties a challenge. Here the authors resolve individual spectral lines of Cu2 in the deep UV region by two-colour resonant four-wave mixing.

    • M. Beck
    • , P. Bornhauser
    •  & P. P. Radi
  • Article
    | Open Access

    Molecular systems displaying aggregation-induced emission (AIE) have important biomedical and optoelectronic applications. Here the authors report a further mechanism for AIE, through aromaticity reversal from the ground state to the excited state, in the non-aromatic annulene derivative of cyclooctatetrathiophene.

    • Zheng Zhao
    • , Xiaoyan Zheng
    •  & Ben Zhong Tang
  • Article
    | Open Access

    Chemical defects endow materials with unique properties but their investigation is challenging due to their small footprint. Here the authors develop a high throughput shortwave infrared spectroscopy method enabling spectral identification and quantitative counting of fluorescent chemical defects at the single defect level.

    • Xiaojian Wu
    • , Mijin Kim
    •  & YuHuang Wang
  • Article
    | Open Access

    Despite recent advances in simulations of tip-enhanced Raman spectroscopy (TERS) under highly confined fields, a simply physical mechanism has remained elusive. Here, the authors show that single molecule TERS images can be explained by local sub-molecular density changes induced by the confined near-field during the Raman process.

    • Xing Chen
    • , Pengchong Liu
    •  & Lasse Jensen
  • Article
    | Open Access

    The long lifetime and spin properties of dark excitons in atomically thin transition metal dichalcogenides offer opportunities to explore light-matter interactions beyond electric dipole transitions. Here, the authors demonstrate that the coupling of the dark exciton and an optically silent chiral phonon enables the intrinsic photoluminescence of the dark-exciton replica in monolayer WSe2

    • Zhipeng Li
    • , Tianmeng Wang
    •  & Su-Fei Shi
  • Article
    | Open Access

    The unique valley and spin texture of atomically thin transition metal dichalcogenides (TMDs) allows the observation of the valley Zeeman effect for neutral and charged excitons. Here, the authors unveil the underlying physics of the magneto-optical response and valley Zeeman splitting of trions in tungsten-based TMDs.

    • T. P. Lyons
    • , S. Dufferwiel
    •  & A. I. Tartakovskii
  • Article
    | Open Access

    Acyl carrier proteins (ACPs), a universal and highly conserved carrier of acyl intermediates during fatty acid and polyketide synthesis, are difficult to visualise. Here, the authors developed a facile, Raman spectroscopy-based method to detect ACP-substrate interactions.

    • Samuel C. Epstein
    • , Adam R. Huff
    •  & Louise K. Charkoudian
  • Article
    | Open Access

    The bacterial protein Cnu together with the transcription repressor H-NS regulate expression of virulence factors in an osmo-sensitive manner. Here authors show that the structure of Cnu swells with decreasing ionic strength driving the oligomerization of H-NS and regulating osmo-sensory response.

    • Abhishek Narayan
    • , Soundhararajan Gopi
    •  & Athi N. Naganathan
  • Article
    | Open Access

    Optical clock networks have many applications from precision time keeping, sensing to fundamental physics. Here the authors demonstrate robust and free-space femtosecond time synchronization of optical clocks via a moving quadcopter.

    • Hugo Bergeron
    • , Laura C. Sinclair
    •  & Nathan R. Newbury
  • Article
    | Open Access

    The mechanism of the non-radiative recombination in halide perovskite nanocrystals has not been fully understood. Here Gerhard et al. resolve the contributions of individual recombination centers by photoluminescence blinking measurements and identify ion migration as the underlying mechanism.

    • Marina Gerhard
    • , Boris Louis
    •  & Ivan G. Scheblykin
  • Article
    | Open Access

    The electronic and photonic contributions to the power conversion efficiency in solar cell devices are often hard to disentangle. Here Bercegol et al. develop a purely optical method to quantitatively decouple and assess the electronic and photonic processes in halide perovskite solar cells.

    • Adrien Bercegol
    • , Daniel Ory
    •  & Laurent Lombez
  • Article
    | Open Access

    The link between how the stiffness of the cornea affects stem cells is unclear. Here, the authors use Brillouin spectro-microscopy to show that mechanical properties of the cornea affect epithelial stem cells and after injury, treating the cornea with collagenase suppresses YAP activation, assisting in regeneration.

    • Ricardo M. Gouveia
    • , Guillaume Lepert
    •  & Che J. Connon
  • Article
    | Open Access

    Upon photoactivation the Orange Carotenoid Protein (OCP) binds to the phycobilisome and prevents damage by thermally dissipating excess energy. Here authors use an Anti-Brownian ELectrokinetic trap to determine the photophysics of single OCP-quenched phycobilisomes and observe two distinct OCP-quenched states with either one or two OCPs bound.

    • Allison H. Squires
    • , Peter D. Dahlberg
    •  & W. E. Moerner
  • Article
    | Open Access

    The characterization of biomacromolecule structural vibrations has been impeded by a broad continuous vibrational density of states obscuring molecule specific vibrations. A terahertz microscopy system using polarization control produces signatures to dynamically fingerprint proteins and a RNA G-quadruplex.

    • Katherine A. Niessen
    • , Mengyang Xu
    •  & Andrea G. Markelz
  • Article
    | Open Access

    Distinguishing electronic and vibrational coherences helps to clarify the near-unity efficiency of primary electron transfer in reaction centres. Here, the authors report their respective correlation with the electron transfer rate by comparing the 2D electronic spectra of three mutant reaction centres.

    • Fei Ma
    • , Elisabet Romero
    •  & Rienk van Grondelle
  • Article
    | Open Access

    Electrochromic technology has diverse cutting-edge applications, but it has never been used to overcome the critical problems in the field of surface-enhanced Raman scattering (SERS). Here, the authors demonstrate a generic electrochromic strategy for ensuring the reproducibility and renewability of SERS substrates.

    • Shan Cong
    • , Zhen Wang
    •  & Zhigang Zhao
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Ice-VII, the densest phase of ice, has been expected to exist only under extreme conditions, such as in Earth’s deep mantle. Shin et al. show spectroscopic evidence that ice-VII-like structures can also be found in water confined in the nanomeniscus between packed nanoparticles at ambient conditions.

    • Dongha Shin
    • , Jonggeun Hwang
    •  & Wonho Jhe
  • Article
    | Open Access

    Materials exhibiting room temperature phosphorescence (RTP) with short afterglow are desirable for bio-medical applications. Here the authors synthesise a library of compounds with tunable RTP properties, embedding carbon nanodots in non-toxic alkaline-earth carbonate, sulphate and oxalate hosts.

    • David C. Green
    • , Mark A. Holden
    •  & Fiona C. Meldrum
  • Article
    | Open Access

    Understanding the pH changes at cell surfaces is important for understanding the mechanisms of different physiological processes. Here, the authors report on the development of a cell membrane anchored gold nanoparticle for surface enhanced Raman spectroscopy determination of pH.

    • Leonardo Puppulin
    • , Shigekuni Hosogi
    •  & Yoshinori Marunaka
  • Article
    | Open Access

    Here, the authors explore the ultrafast photodynamics of methyl anthranilate. From the quantum beat behavior, the authors find evidence for ultrafast energy redistribution processes which hinder excited state relaxation, making methyl anthranilate a poor choice for a sunscreen chemical filter.

    • Natércia d. N. Rodrigues
    • , Neil C. Cole-Filipiak
    •  & Vasilios G. Stavros
  • Article
    | Open Access

    Alignment and orientation of the molecules allows studying the photon-molecule interactions in greater detail. Here the authors demonstrate the three-dimensional orientation of SO2 molecules in using COLTRIMS and orthogonally polarized laser pulses but in the absence of DC field.

    • Kang Lin
    • , Ilia Tutunnikov
    •  & Jian Wu
  • Article
    | Open Access

    Molecular aggregation is a widespread and important process in physiological metabolism, but details regarding conformational changes during the process are hard to probe. Here, the authors use circular dichroism to monitor in-situ the conformational changes occurring during molecular aggregation.

    • Haoke Zhang
    • , Xiaoyan Zheng
    •  & Ben Zhong Tang
  • Article
    | Open Access

    The short exciton life time in atomically thin transition metal dichalcogenides poses limitations to efficient control of the valley pseudospin and coherence. Here, the authors manipulate the exciton coherence in a WSe2 monolayer embedded in an optical microcavity in the strong light-matter coupling regime.

    • S. Dufferwiel
    • , T. P. Lyons
    •  & A. I. Tartakovskii
  • Article
    | Open Access

    Molecular details that underlie mechanical properties of spider silk are of great interest to material scientists. Here, the authors report a previously unknown three-state mechanism of folding and an expanded structure of a spider silk protein that may contribute to elasticity of spider silk.

    • Charlotte Rat
    • , Julia C. Heiby
    •  & Hannes Neuweiler
  • Article
    | Open Access

    Fourier transform spectrometers are generally limited to slow scanning rates at high resolution. Here the authors demonstrate highly efficient Fourier transform spectroscopy using a dynamic phase-control technique that enables fast acquisition without compromising bandwidth or resolution.

    • Kazuki Hashimoto
    •  & Takuro Ideguchi