Research Highlights
Pei-Ling Luo* and I-Yun Chen
Analytical Chemistry, 94, 5752 (2022)
A novel spectrometer has been developed based on synchronized two-color time-resolved dual-comb spectroscopy (TRDCS), enabling high-resolution hyperspectral measurements. The proposed approach with TRDCS exhibits great potential in quantitative diagnostics of multispecies and opens opportunities to decipher key reaction mechanisms in atmospheric chemistry. In this work, we perform simultaneous measurements in two distinct molecular fingerprint regions near 2.9 and 7.8 μm by employing the new approach with synchronized two-color TRDCS. Upon flash photolysis of CH2I2/O2/N2 gas mixtures, multiple reaction species, involving the simplest Criegee intermediates (CH2OO), formaldehyde (CH2O), hydroxyl (OH) and hydroperoxy (HO2) radicals are simultaneously detected with microsecond time resolution. The concentration of each molecule can be determined based on high-resolution rovibrational absorption spectroscopy. With quantitative detection and simulation of temporal concentration profiles of the targeted molecules at various conditions, the underlying reaction mechanisms and pathways related to the formation of the HOx radicals, which can be generated from decomposition of initially energized and vibrationally excited Criegee intermediates, are explored.
Cheng-Chieh Lin, Shing-Jong Huang, Pei-Hao Wu, Tzu-Pei Chen, Chih-Ying Huang, Ying-Chiao Wang, Po-Tuan Chen, Denitsa Radeva, Ognyan Petrov, Vladimir Gelev, Raman Sankar, Chia-Chun Chen,
Chun-Wei Chen*, Tsyr-Yan Yu*
Nature Communications, 13, 1513 (2022).
Limited methods are available for investigating the reorientational dynamics of A-site cations in two-dimensional organic–inorganic hybrid perovskites (2D OIHPs), which play a pivotal role in determining their physical properties. Here, we describe an approach to study the dynamics of A-site cations using solid-state NMR and stable isotope labelling. 2H NMR of 2D OIHPs incorporating methyl-d3-ammonium cations (d3-MA) reveals the existence of multiple modes of reorientational motions of MA. Rotational-echo double resonance (REDOR) NMR of 2D OIHPs incorporating 15N- and 13C-labeled methylammonium cations (13C,15N-MA) reflects the averaged dipolar coupling between the C and N nuclei undergoing different modes of motions. Our study reveals the interplay between the A-site cation dynamics and the structural rigidity of the organic spacers, so providing a molecular-level insight into the design of 2D OIHPs.
Dr. Chia-Lung Hsieh
(2022)
Yi-Teng Hsiao, Chia-Ni Tsai, Te-Hsin Chen, Chia-Lung Hsieh*
ACS Nano, 16(2): 2774-2788 (2022)
Chromatin is a DNA–protein complex that is densely packed in the cell nucleus. The nanoscale chromatin compaction plays critical roles in the modulation of cell nuclear processes. However, little is known about the spatiotemporal dynamics of chromatin compaction states because it remains difficult to quantitatively measure the chromatin compaction level in live cells. Here, we demonstrate a strategy, referenced as DYNAMICS imaging, for mapping chromatin organization in live cell nuclei by analyzing the dynamic scattering signal of molecular fluctuations. Highly sensitive optical interference microscopy, coherent brightfield (COBRI) microscopy, is implemented to detect the linear scattering of unlabeled chromatin at a high speed. A theoretical model is established to determine the local chromatin density from the statistical fluctuation of the measured scattering signal. DYNAMICS imaging allows us to reconstruct a speckle-free nucleus map that is highly correlated to the fluorescence chromatin image. Moreover, together with calibration based on nanoparticle colloids, we show that the DYNAMICS signal is sensitive to the chromatin compaction level at the nanoscale. We confirm the effectiveness of DYNAMICS imaging in detecting the condensation and decondensation of chromatin induced by chemical drug treatments. Importantly, the stable scattering signal supports a continuous observation of the chromatin condensation and decondensation processes for more than 1 h. Using this technique, we detect transient and nanoscopic chromatin condensation events occurring on a time scale of a few seconds. Label-free DYNAMICS imaging offers the opportunity to investigate chromatin conformational dynamics and to explore their significance in various gene activities.Link to the paper: https://pubs.acs.org/doi/10.1021/acsnano.1c09748Recommended in Faculty Opinion: https://facultyopinions.com/prime/741388510Reported by Science Promotion & Engagement Center: https://spec.ntu.edu.tw/20220322-research-chem/
Hao-Ting Chin, Jiri Klimes, I-Fan Hu, Ding-Rui Chen, Hai-Thai Nguyen, Ting-Wei Chen, Shao-Wei Ma, Mario Hofmann, Chi-Te Liang & Ya-Ping Hsieh
Nature Communications, 12:6291 (2021).
We here report on the direct observation of ferroelectric properties of water ice in its 2D phase. Upon nanoelectromechanical confinement between two graphene layers, water forms a 2D ice phase at room temperature that exhibits a strong and permanent dipole which depends on the previously applied field, representing clear evidence for ferroelectric ordering. Characterization of this permanent polarization with respect to varying water partial pressure and temperature reveals the importance of forming a monolayer of 2D ice for ferroelectric ordering which agrees with ab-initio and molecular dynamics simulations conducted. The observed robust ferroelectric properties of 2D ice enable novel nanoelectromechanical devices that exhibit memristive properties. A unique bipolar mechanical switching behavior is observed where previous charging history controls the transition voltage between low-resistance and high-resistance state. This advance enables the realization of rugged, non-volatile, mechanical memory exhibiting switching ratios of 106, 4 bit storage capabilities and no degradation after 10,000 switching cycles.
Ming-Wei Lee, Yi-Ting Chuang, and Liang-Yan Hsu*
Journal of Chemical Physics 155, 074101 (2021); https://doi.org/10.1063/5.0057018
![Representative picture of Theory of molecular emission power spectra. II. Angle, frequency, and distance dependence of electromagnetic environment factor of a molecular emitter in plasmonic environments [Special Issue: 2021 JCP Emerging Investigators Special Collection]](../image/research/org/research-251.jpg "Representative picture of Theory of molecular emission power spectra. II. Angle, frequency, and distance dependence of electromagnetic environment factor of a molecular emitter in plasmonic environments [Special Issue: 2021 JCP Emerging Investigators Special Collection]")
Our previous study [S. Wang et al., J. Chem. Phys. 153, 184102 (2020)] has shown that in a complex dielectric environment, molecular emission power spectra can be expressed as the product of the lineshape function and the electromagnetic environment factor (EEF). In this work, we focus on EEFs in a vacuum–NaCl–silver system and investigate molecular emission power spectra in the strong exciton–polariton coupling regime. A numerical method based on computational electrodynamics is presented to calculate the EEFs of single-molecule emitters in a dispersive and lossy dielectric environment with arbitrary shapes. The EEFs in the far-field region depend on the detector position, emission frequency, and molecular orientation. We quantitatively analyze the asymptotic behavior of the EFFs in the far-field region and qualitatively provide a physical picture. The concept of EEF should be transferable to other types of spectra in a complex dielectric environment. Finally, our study indicates that molecular emission power spectra cannot be simply interpreted by the lineshape function (quantum dynamics of a molecular emitter), and the effect of the EEFs (photon propagation in a dielectric environment) has to be carefully considered.
Institute of Atomic and Molecular Sciences Academia Sinica
