Optical spectroscopy

  • Article
    | Open Access

    Broad uptake of smFRET has been hindered by high instrument costs and a lack of open-source hardware and acquisition software. Here, the authors present the smfBox, a cost-effective open-source platform capable of measuring precise FRET efficiencies between dyes on freely diffusing single molecules.

    • Benjamin Ambrose
    • , James M. Baxter
    •  & Timothy D. Craggs
  • Article
    | Open Access

    Multidimensional photography has traditionally been restricted by their static optical architectures and measurement schemes. Here, the authors present a tunable multidimensional photography approach employing active optical mapping, which allows them to adapt the acquisition schemes to the scene.

    • Jongchan Park
    • , Xiaohua Feng
    •  & Liang Gao
  • Article
    | Open Access

    Understanding the correlation between molecular structure and properties of 2D hybrid perovskites is crucial for material design and device performance. Here, the authors reveal that conformation of organic cations in the inorganic cages has strong effects on charge mobility and broadband emission behaviour.

    • Chuanzhao Li
    • , Jin Yang
    •  & Shuji Ye
  • Article
    | Open Access

    Spectroscopic studies of water clusters provide insight into the hydrogen bond structure of water and ice. The authors measure infrared spectra of neutral water octamers using a threshold photoionization technique based on a tunable vacuum-UV free electron laser, identifying two cubic isomers in addition to those previously observed.

    • Gang Li
    • , Yang-Yang Zhang
    •  & Ling Jiang
  • Article
    | Open Access

    Quantifying lipid and water content in tissues non-invasively is difficult, and no method exists to quantify lipids in blood non-invasively. Here the authors develop an imaging approach called shortwave infrared meso-patterned imaging (SWIR-MPI) to detect and spatially map tissue water and lipids in preclinical models.

    • Yanyu Zhao
    • , Anahita Pilvar
    •  & Darren Roblyer
  • Article
    | Open Access

    The formation dynamics of excitons in 2D transition metal dichalcogenides are challenging to probe directly because of their inherently fast timescales. Here, the authors use extremely short optical pulses to excite an electron-hole plasma, and show the formation of 2D excitons in MoS2 on the timescale of 30 fs.

    • Chiara Trovatello
    • , Florian Katsch
    •  & Stefano Dal Conte
  • Article
    | Open Access

    SERS can be unreliable for biomedical use. The authors demonstrate a metal-free nanostructure composed of porous carbon nanowires in an array as a SERS substrate. It offers 106 signal enhancement due to strong broadband charge-transfer resonance and substrate-to-substrate, spot-to-spot and time-to-time consistency in the SERS spectrum.

    • Nan Chen
    • , Ting-Hui Xiao
    •  & Keisuke Goda
  • Article
    | Open Access

    Single-cell metabolomics can offer deep insights into the metabolic reprogramming that accompanies disease states. Here, the authors use Raman spectro-microscopy for non-invasive metabolite analysis and identification of druggable metabolic susceptibilities in single live melanoma cells.

    • Jiajun Du
    • , Yapeng Su
    •  & Lu Wei
  • Article
    | Open Access

    Carbyne, a linear sp-hybridized carbon allotrope, is synthetically inaccessible and its properties are extrapolated from those of defined oligomers. Here the authors analyze weak optical bands in two series of oligoynes and reassess the optical and fundamental gap of carbyne to lower values than previously suggested.

    • Johannes Zirzlmeier
    • , Stephen Schrettl
    •  & Holger Frauenrath
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Efficient generation of phonons is an important ingredient for a prospective electrically-driven phonon laser for coherent control of quantum systems. Here, the authors report on laser-like phonon emission in a hybrid semiconductor microcavity that optomechanically couples BEC polaritons with phonons.

    • D. L. Chafatinos
    • , A. S. Kuznetsov
    •  & A. Fainstein
  • Article
    | Open Access

    Chirality of nanostructures may be determined by ensemble measurements in solution or on single immobilized nanoparticles, with loss of detail or interference from the substrate. Here the authors demonstrate that circular differential scattering intensity spectra of freely diffusing single nanoparticles provide chiroptical spectra which reflect their intrinsic chirality.

    • Johannes Sachs
    • , Jan-Philipp Günther
    •  & Peer Fischer
  • Article
    | Open Access

    Single-molecule sensing is very challenging due to weak emitted signals and environmental interference. Here the authors design a method (i-SET) for single molecule sensing with core-shell upconverting nanoparticles, which relies on signal enhancement by the activator-rich probes to quantify fluorophores attached to a single nanoparticle.

    • Jian Zhou
    • , Changyu Li
    •  & Renren Deng
  • Article
    | Open Access

    Here, the authors show that the resolution and speed limitations in broadband photo-acoustic spectroscopy can be overcome by combining dual-comb spectroscopy with photo-acoustic detection. This enables broadband detection and allows for rapid and sensitive multi-species molecular analysis across all wavelengths of light.

    • Thibault Wildi
    • , Thibault Voumard
    •  & Tobias Herr
  • Article
    | Open Access

    The synthesis of hydrocarbons with attractive electronic structures remains challenging. Here, the authors describe the synthesis and properties of the C70 fragment as-indaceno[3,2,1,8,7,6-ghijklm]terrylene, which exhibits near-infrared (NIR) absorption.

    • Yuki Tanaka
    • , Norihito Fukui
    •  & Hiroshi Shinokubo
  • Article
    | Open Access

    Imaging zeolites in catalysis relies on the use of probe molecules or model catalysts. Here the authors show the synergy of a multiscale reaction-diffusion model and structured illumination microscopy to illustrate spatiotemporal evolution of molecules and acid sites in SAPO-34 zeolites in methanol-to-olefins reaction.

    • Mingbin Gao
    • , Hua Li
    •  & Zhongmin Liu
  • Article
    | Open Access

    Genetically encoded voltage indicators (GEVIs) allow visualisation of fast action potentials in neurons but most are bright at rest and dimmer during an action potential. Here, the authors engineer electrochromic FRET GEVIs with fast, bright and positive-going fluorescence signals for in vivo imaging.

    • Ahmed S. Abdelfattah
    • , Rosario Valenti
    •  & Eric R. Schreiter
  • Article
    | Open Access

    Most current cell sorting methods are based on fluorescence detection with no imaging capability. Here the authors generate and use Raman image-activated cell sorting with a throughput of around 100 events per second, providing molecular images with no need for labeling.

    • Nao Nitta
    • , Takanori Iino
    •  & Keisuke Goda
  • Article
    | Open Access

    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
  • Article
    | Open Access

    An out-of-plane magnetic field is expected to strongly modify exciton-phonon interactions in atomically thin transitional metal dichalcogenides. Here, the authors show that the phonon-exciton interaction in monolayer WSe2 lifts the inter-Landau-level transition selection rules for dark trions.

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

    The authors develop a first-principles workflow for calculating Raman spectra of 733 monolayers from the computational 2D materials database. After benchmarking results against experimental data for 15 monolayers, an automatic procedure for identifying a material from its Raman spectrum is proposed.

    • Alireza Taghizadeh
    • , Ulrik Leffers
    •  & Kristian S. Thygesen
  • Article
    | Open Access

    Solar-driven CO2 reduction by abundant water to alcohols is hindered by the sluggish water oxidation reaction. Here, the authors demonstrate that the microwave-synthesized carbon-dots possess unique hole-accepting nature, allowing stoichiometric oxygen and methanol production from water and CO2 with nearly 100% selectivity to methanol.

    • Yiou Wang
    • , Xu Liu
    •  & Junwang Tang
  • Article
    | Open Access

    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
  • Article
    | Open Access

    The mechanism of PARP1-dependent poly-ADP-ribosylation in response to DNA damage is still under debate. Here, the authors use ATR-FTIR spectroscopy to provide time-resolved insights into the molecular details of this process under near physiological conditions.

    • Annika Krüger
    • , Alexander Bürkle
    •  & Aswin Mangerich
  • Article
    | Open Access

    Room temperature phosphorescence (RTP) is a topic which is currently widely studied, but a study on the correlation between types of molecular solid and RTP properties is lacking. Here the authors show that RTP is enhanced in the racemic form of axial chiral molecules due to its denser R- and S- cross packing arrangement.

    • Xiugang Wu
    • , Chun-Ying Huang
    •  & Pi-Tai Chou
  • Article
    | Open Access

    TagRFP is a bright red fluorescent protein, but undergoes photoconversion to a dark state, making it undesirable for conventional fluorescence microscopy. Here, the authors introduce stabilising mutations to create super-TagRFP (stagRFP) and demonstrate its application as both a FRET acceptor and FRET donor.

    • Gary C. H. Mo
    • , Clara Posner
    •  & Jin Zhang
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Circular polarization luminescence (CPL) spectroscopy is a tool to study chiroptical systems, but the measurement process is generally very slow. The authors introduce a CPL technique with much faster acquisition, demonstrating meaningful time-dependent measurements and enabling new applications.

    • Lewis E. MacKenzie
    • , Lars-Olof Pålsson
    •  & Robert Pal
  • Article
    | Open Access

    Knowing compositional motifs of nanoparticle catalysts in operando conditions is crucial towards understanding their catalytic behavior. Here, the authors develop a physics-driven machine learning approach to predict adsorption sites for a CO molecule over platinum nanoparticles in a multitude of coordination environments.

    • Joshua L. Lansford
    •  & Dionisios G. Vlachos
  • Article
    | Open Access

    Disentangling the radiative and non-radiative plasmon mode contributions to the total photonic density of states is a challenge. Here, the authors report a procedure to eliminate the electronic-structure factors from scanning tunnelling microscope luminescence spectra to isolate the radiative component.

    • Alberto Martín-Jiménez
    • , Antonio I. Fernández-Domínguez
    •  & Roberto Otero
  • Article
    | Open Access

    Light pulses with controllable parameters are desired for studying the fundamental properties of matter. Here the authors generate and use phase-manipulated and highly time-stable XUV pulse pairs to probe the coherent evolution and dephasing of XUV electronic coherences in helium and argon.

    • Andreas Wituschek
    • , Lukas Bruder
    •  & Frank Stienkemeier
  • Article
    | Open Access

    Typically, the performance of the state-of-the-art laser sensors is insufficient for many high precision applications. Here, the authors report mode-phase-difference photothermal spectroscopy with a dual-mode anti-resonant hollow-core optical fiber and demonstrate acetylene detection with ultra-high sensitivity.

    • Pengcheng Zhao
    • , Yan Zhao
    •  & Pu Wang
  • Article
    | Open Access

    Two-dimensional hybrid perovskites are promising excitonic materials; however, there currently lacks understanding on exciton diffusion and annihilation. Here Deng et al. employ transient absorption microscopy to disentangle quantum-well-thickness-dependent exciton transport and annihilation in these materials.

    • Shibin Deng
    • , Enzheng Shi
    •  & Libai Huang
  • Article
    | Open Access

    Physical unclonable functions with inherent randomness are promising candidates for secure labeling systems. Here the authors demonstrate such a function using gap-enhanced Raman tags to create high-capacity and high-security labels for anticounterfeiting.

    • Yuqing Gu
    • , Chang He
    •  & Jian Ye
  • Article
    | Open Access

    Hydrated protons are always present in aqueous solution, but their molecular structure remains under debate. Here the authors use vibrational sum frequency spectroscopy to show that at negatively charged liquid–vapor interfaces, protons adopt a specific configuration characteristic of Eigen-like species.

    • Eric Tyrode
    • , Sanghamitra Sengupta
    •  & Adrien Sthoer
  • Article
    | Open Access

    The determination of the speciation of ions and molecules in supercritical aqueous fluids under pressure is key to understanding their mass transport in the Earth’s interior. Here the authors present a strategy based on ab-initio molecular dynamics to determine the speciation of carbonates in aqueous fluids.

    • Ding Pan
    •  & Giulia Galli
  • Article
    | Open Access

    Diffuse optical flowmetry is widely used to assess blood flow dynamics, but has remained difficult to interpret. Here, the authors use interferometric near-infrared spectroscopy, revealing additional information about optical phase and time-of-flight, and observe the Brownian nature of blood flow dynamics in humans.

    • Oybek Kholiqov
    • , Wenjun Zhou
    •  & Vivek J. Srinivasan
  • Article
    | Open Access

    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
  • Article
    | Open Access

    Raman probes which operate in the cellular silent region are of interest for live cell imaging. Here, the authors report on the development of a water soluble polydiacetylene Raman probe with enhanced Raman signal in the silent region which can be functionalised for organelle targeting and demonstrate application.

    • Sidan Tian
    • , Haozheng Li
    •  & Liang Luo
  • Article
    | Open Access

    In analogy to the coupling of atoms into molecules, the authors fuse colloidal semiconductor nanocrystals into quantum dot dimers. These nanocrystal ‘molecules’ exhibit significant quantum coupling effects, making them promising for applications in devices and potential quantum technologies.

    • Jiabin Cui
    • , Yossef E. Panfil
    •  & Uri Banin
  • Article
    | Open Access

    Here, the authors report parametric down-conversion of X-rays into long wavelength radiation in gallium arsenide and lithium niobate crystals, with efficiencies about 4 orders of magnitude stronger than the efficiencies measured in any material studied previously. They explore the lack of inversion symmetry as a possible physical mechanism.

    • S. Sofer
    • , O. Sefi
    •  & S. Shwartz