Research Highlights
Ya-Ping Hsieh
Ferroelectric 2D ice under graphene confinement
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
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.
Liang-Yan Hsu
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]
Ming-Wei Lee, Yi-Ting Chuang, and Liang-Yan Hsu*
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.
Ya-Ping Hsieh
2D mechano-thermoelectric heterojunctions for self-powered strain sensors
Ying-Yu Wang, Ding-Rui Chen, Jen-Kai Wu, Tian-Hsin Wang, Chiashain Chuang, Ssu-Yen Huang, Wen-Pin Hsieh, Mario Hofmann, Yuan-Huei Chang, Ya-Ping Hsieh*
We here demonstrate the multifunctional properties of atomically thin heterojunctions that are enabled by strong interfacial interactions and their integration into ultra-high performance, self-powered sensors. Epitaxial alignment between tin diselenide and graphene through direct growth produces thermoelectric and mechanoelectric properties beyond the ability of either component. An unprecedented ZT of 2.43 originated from the synergistic combination of graphene’s high carrier conductivity and SnSe2 mediated thermal conductivity lowering. Moreover, strong interaction at the SnSe2/graphene interface produces stress localization that results in a novel 2D-crack-assisted strain sensing mechanism whose sensitivity (GF=450) is superior to all other 2D materials. Finally, the graphene-assisted growth process, permits the formation of high-quality heterojunctions directly on polymeric substrates for flexible and transparent self-powered sensors that achieve fast and reliable strain sensing from a small temperature gradient. Our work enhances the fundamental understanding of multifunctionality at the atomic scale and provide a route towards structural health monitoring through ubiquitous and smart devices.
Yang-hao Chan
Giant exciton-enhanced shift currents and direct current conduction with subbandgap photo excitations produced by many-electron interactions
Y. H. Chan, Diana Y. Qiu, Felipe H. da Jornada, and Steven G. Louie
Shift current is a direct current generated from nonlinear light–matter interaction in a noncentrosymmetric crystal and is considered a promising candidate for next-generation photovoltaic devices. The mechanism for shift currents in real materials is, however, still not well understood, especially if electron–hole interactions are included. Here, we employ a first-principles interacting Green’s-function approach on the Keldysh contour with real-time propagation to study photocurrents generated by nonlinear optical processes under continuous wave illumination in real materials. We demonstrate a strong direct current shift current at subbandgap excitation frequencies in monolayer GeS due to strongly bound excitons, as well as a giant excitonic enhancement in the shift current coefficients at above bandgap photon frequencies. Our results suggest that atomically thin two-dimensional materials may be promising building blocks for next-generation shift current devices.
Jer-Lai Kuo
Vibrational Coupling in Solvated H3O+: Interplay between Fermi Resonance and Combination Band
Qian-Rui Huang, Ying-Cheng Li, Tomoki Nishigori, Marusu Katada, Asuka Fujii,* and Jer-Lai Kuo*
Complex vibrational features of solvated hydronium ion, H3O+, in 3 μm enable us to look into the vibrational coupling among O-H stretching modes and other degrees of freedom. Two anharmonic coupling schemes have often been engaged to explain observed spectra: coupling with OH bending overtone, known as Fermi resonance (FR), has been proposed to account for the splitting of the OH stretch band at ~3300 cm-1 in H3O+…Ar3, but an additional peak in H3O+…(N2)3 at the similar frequency region has been assigned to a combination band (CB) with the low-frequency intermolecular stretches. While even stronger vibrational coupling is expected in H3O+…(H2O)3, such pronounced peaks are absent. In the present study, vibrational spectra of H3O+…Kr3 and H3O+…(CO)3 are measured to complement the existing spectra. Using ab initio anharmonic algorithms, we are able to assign the observed complex spectral features, to resolve seemingly contradictory notions in the interpretations, and to reveal simple pictures of the interplay between FR and CB.
Jer-Lai Kuo
Strong Fermi resonance associated with proton motions revealed by vibrational spectra of asymmetric proton bound dimers
Qian-Rui Huang, Ryunosuke Shishido, Chih-Kai Lin, Chen-Wei Tsai, Jake A. Tan, Asuka Fujii* and Jer-Lai Kuo*
Experimental infrared spectra between 2600 to 3800 cm-1 for a series of asymmetric proton bound dimers with protonated trimethylamine (TMA–H+) as the proton donor were recorded and analyzed. Based on conventional wisdom, the frequency of the N-H+ stretching mode is expected to red shift as the proton affinity of proton acceptors (Ar, N2, CO, C2H2, H2O, CH3OH, and C2H5OH) increases. The observed band, however, shows a peculiar splitting of ≈300 cm-1 with the intensity shifting pattern resembling a two-level system. Theoretical investigation based on ab initio anharmonic algorithms reveals that the observed band splitting and its extraordinarily large gap of ≈300 cm-1 is a result of strong coupling between fundamental of the proton stretching mode and overtone states of the two proton bending modes, that is commonly known as Fermi resonance (FR). We also provide a simple and general theoretical model to link the strong FR coupling to the quasi-two-level system behavior in the observed band intensity. Since the model does not depend on the molecular specification of TMA–H+, the strong coupling we observed here is an intrinsic property associated with proton motions in a wide range of molecular systems.
Liang-Yan Hsu
Large-Scale Inhomogeneous Fluorescence Plasmonic Silver Chips: Origin and Mechanism
Liang-Yan Hsu*, Hung-Chi Yen, Ming-Wei Lee, Yae-Lin Sheu, Po-Chun Chen, Hongjie Dai*, Chia-Chun Chen*
Large-scale inhomogeneous plasmonic metal chips have been demonstrated as a promisingplatform for biochemical sensing, but the origin of their strong fluorescence enhancementsand average gap dependence is a challenging issue due to the complexity of modelingtremendous molecules within inhomogeneous gaps. To address this issue, we bridgedmicroscopic mechanisms and macroscopic observations, developed a kinetic model, andexperimentally investigated the fluorescence enhancement factors of IR800-streptavidinimmobilized on metal nanoisland films (NIFs). Inspired by the kinetic model, we controlledthe distribution of IR800-streptavidin within the valleys of NIFs by regioselectivemodification and achieved the fluorescence intensity enhancement up to 488-fold. Thekinetic model allows us to qualitatively explain the mechanism of fluorescence intensityenhancements and quantitatively predict the trend of experimental enhancement factors,thereby determining the design principles of the plasmonic metal chips. Our studyprovides one key step further toward the sensing applications of large-scale plasmonicmetal chips.
Kuei-Hsien Chen
Probing the active site in nonprecious metal-macrocyclic catalysts for ORR via multimodal operando X-ray and electrochemical spectroscopic studies
Hsiang-Ting Lien, Sun-Tang Chang, Po-Tuan Chen, Deniz P. Wong, Yu-Chung Chang, Ying-Rei Lu, Chung-Li Dong, Chen-Hao Wang, Kuei-Hsien Chen & Li-Chyong Chen 
Nonnoble metal catalysts are low-cost alternatives to Pt for the oxygen reduction reactions (ORRs), which have been studied for various applications in electrocatalytic systems. Among them, transition metal complexes, characterized by a redox-active single-metal-atom with biomimetic ligands, such as pyrolyzed cobalt–nitrogen–carbon (Co–N x /C), have attracted considerable attention. Therefore, we reported the ORR mechanism of pyrolyzed Vitamin B12 using operando X-ray absorption spectroscopy coupled with electrochemical impedance spectroscopy, which enables operando monitoring of the oxygen binding site on the metal center. material design strategies for high-performance electrocatalysts for fuel cell applications. Furthermore, the charge transfer mechanism between the catalyst and reactant enables further Co–O species formation. These experimental findings, provide insight into metal active-site geometry and structural evolution during ORR, which could be used for developing material design strategies for high performance electrocatalysts for fuel cell applications.
Kuei-Hsien Chen
Self-capping vapor-liquid-solid (VLS) growth of MoS2
Ming-Chiang Chang, Po-Hsun Ho, Mao-Feng Tseng, Fang-Yuan Lin, Cheng-Hung Hou, I-Kuan Lin, Hsin Wang, Pin-Pin Huang, Chun-Hao Chiang, Yueh-Chiang Yang, I-Ta Wang, He-Yun Du, Cheng-Yen Wen, Jing-Jong Shyue, Chun-Wei Chen, Kuei-Hsien Chen, Po-Wen Chiu & Li-Chyong Chen
In this study, a self-capping vaporliquid-solid reaction is proposed to fabricate large-grain, continuous MoS2 films. An intermediate liquid phase-Na2Mo2O7 is formed through a eutectic reaction of MoO3 and NaF,followed by being sulfurized into MoS2. The as-formed MoS2 seeds function as a capping layer that reduces the nucleation density and promotes lateral growth. By tuning the driving force of the reaction, large mono/bilayer (1.1 mm/200 μm) flakes or full-coverage films (with a record-high average grain size of 450 μm) can be grown on centimeter-scale substrates. The field-effect transistors fabricated from the full-coverage films show high mobility (33 and 49 cm2V-1s-1 for the mono and bilayer regions) and on/off ratio (1 ~ 5 × 108) across a 1.5 cm × 1.5 cm region.
Charles Pin-Kuang Lai
A multiplexed bioluminescent reporter for sensitive and non-invasive tracking of DNA double strand break repair dynamics in vitro and in vivo
Jasper Che-Yung Chien, Elie Tabet, Kelsey Pinkham, Cintia Carla da Hora, Jason Cheng-Yu Chang, Steven Lin, Christian E. Badr* and Charles Pin-Kuang Lai*
Tracking DNA double strand break (DSB) repair is paramount for the understanding and therapeutic development of various diseases including cancers. Herein, we describe a multiplexed bioluminescent repair reporter (BLRR) for non-invasive monitoring of DSB repair pathways in living cells and animals. The BLRR approach employs secreted Gaussia and Vargula luciferases to simultaneously detect homology-directed repair (HDR) and non-homologous end joining (NHEJ), respectively. BLRR data are consistent with next-generation sequencing results for reporting HDR (R2 = 0.9722) and NHEJ (R2 = 0.919) events. Moreover, BLRR analysis allows longitudinal tracking of HDR and NHEJ activities in cells, and enables detection of DSB repairs in xenografted tumours in vivo. Using the BLRR system, we observed a significant difference in the efficiency of CRISPR/Cas9-mediated editing with guide RNAs only 1–10 bp apart. Moreover, BLRR analysis detected altered dynamics for DSB repair induced by small-molecule modulators. Finally, we discovered HDR-suppressing functions of anticancer cardiac glycosides in human glioblastomas and glioma cancer stem-like cells via inhibition of DNA repair protein RAD51 homolog 1 (RAD51). The BLRR method provides a highly sensitive platform to simultaneously and longitudinally track HDR and NHEJ dynamics that is sufficiently versatile for elucidating the physiology and therapeutic development of DSB repair.
Charles Pin-Kuang Lai
Multiresolution Imaging Using Bioluminescence Resonance Energy Transfer Identifies Distinct Biodistribution Profiles of Extracellular Vesicles and Exomeres with Redirected Tropism
Anthony Yan-Tang Wu, Yun-Chieh Sung, Yen-Ju Chen, Steven Ting-Yu Chou, Vanessa Guo, Jasper Che-Yung Chien, John Jun-Sheng Ko, Alan Ling Yang, Hsi-Chien Huang, Ju-Chen Chuang, Syuan Wu, Meng-Ru Ho, Maria Ericsson, Wan-Wan Lin, Chantal Hoi Yin Cheung, Hsueh-Fen Juan, Koji Ueda, Yunching Chen, Charles Pin-Kuang Lai*
Extracellular particles (EPs) including extracellular vesicles (EVs) and exomeres play significant roles in diseases and therapeutic applications. However, their spatiotemporal dynamics in vivo have remained largely unresolved in detail due to the lack of a suitable method. Therefore, a bioluminescence resonance energy transfer (BRET)‐based reporter, PalmGRET, is created to enable pan‐EP labeling ranging from exomeres (<50 nm) to small (<200 nm) and medium and large (>200 nm) EVs. PalmGRET emits robust, sustained signals and allows the visualization, tracking, and quantification of the EPs from whole animal to nanoscopic resolutions under different imaging modalities, including bioluminescence, BRET, and fluorescence. Using PalmGRET, it is shown that EPs released by lung metastatic hepatocellular carcinoma (HCC) exhibit lung tropism with varying distributions to other major organs in immunocompetent mice. It is further demonstrated that gene knockdown of lung‐tropic membrane proteins, solute carrier organic anion transporter family member 2A1, alanine aminopeptidase/Cd13, and chloride intracellular channel 1 decreases HCC‐EP distribution to the lungs and yields distinct biodistribution profiles. It is anticipated that EP‐specific imaging, quantitative assays, and detailed in vivo characterization are a starting point for more accurate and comprehensive in vivo models of EP biology and therapeutic design.
Jyhpyng Wang
Photon deceleration in plasma wakes generates single-cycle relativistic tunable infrared pulses
Zan Nie, Chih-Hao Pai, Jie Zhang, Xiaonan Ning, Jianfei Hua, Yunxiao He, Yipeng Wu, Qianqian Su, Shuang Liu, Yue Ma, Zhi Cheng, Wei Lu1, Hsu-Hsin Chu, Jyhpyng Wang, Chaojie Zhang, Warren B. Mori, and Chan Joshi
Availability of relativistically intense, single-cycle, tunable infrared sources will open up newareas of relativistic nonlinear optics of plasmas, impulse IR spectroscopy and pump-probeexperiments in the molecular fingerprint region. However, generation of such pulses is still achallenge by current methods. Recently, it has been proposed that time dependent refractiveindex associated with laser-produced nonlinear wakes in a suitably designed plasma densitystructure rapidly frequency down-converts photons. The longest wavelength photons slipbackwards relative to the evolving laser pulse to form a single-cycle pulse within the nearlyevacuated wake cavity. This process is called photon deceleration. Here, we demonstrate thisscheme for generating high-power (~100 GW), near single-cycle, wavelength tunable(3–20 μm), infrared pulses using an 810 nm drive laser by tuning the density profile of theplasma. We also demonstrate that these pulses can be used to in-situ probe the transient andnonlinear wakes themselves.
Jung-Chi Liao
Super-resolution microscopy reveals coupling between mammalian centriole subdistal appendages and distal appendages
Subdistal appendages (sDAPs) are centriolar elements observed proximal to the distal appendages (DAPs) in vertebrates. Despite their obvious presence, structural and functional understanding of sDAPs remains elusive. Here, by combining super-resolved localization analysis and CRISPR-Cas9 genetic perturbation, we find that, although DAPs and sDAPs are primarily responsible for distinct functions in ciliogenesis and microtubule anchoring respectively, the presence of one element actually affects the positioning of the other. Specifically, we find dual layers of both ODF2 and CEP89, where their localizations are differentially regulated by DAP and sDAP integrity. DAP depletion relaxes longitudinal occupancy of sDAP protein ninein to cover the DAP region, implying a role of DAPs in sDAP positioning. Removing sDAPs alter the distal border of centrosomal γ-tubulins, illustrating a new role of sDAPs. Together, our results provide an architectural framework of sDAPs to shed light on functional understanding, surprisingly revealing the coupling between DAPs and sDAPs.
Chia-Lung Hsieh
Monovalent and Oriented Labeling of Gold Nanoprobes for the High-Resolution Tracking of a Single-Membrane Molecule
Yi-Hung Liao, Chih-Hsiang Lin, Ching-Ya Cheng, Wai Cheng Wong, Jz-Yuan Juo, Chia-Lung Hsieh*
Single-molecule tracking is a powerful method to study molecular dynamics in living systems including biological membranes. High-resolution single-molecule tracking requires a bright and stable signal, which has typically been facilitated by nanoparticles due to their superb optical properties. However, there are concerns about using a nanoparticle to label a single molecule because of its relatively large size and the possibility of cross-linking multiple target molecules, both of which could affect the original molecular dynamics. In this work, using various labeling schemes, we investigate the effects using nanoparticles to measure the diffusion of single-membrane molecules. We demonstrate a simple and robust strategy for the monovalent and oriented labeling of a single lipid molecule with a AuNP by using naturally dimeric rhizavidin (rAv) as a bridge, thus connecting the biotinylated nanoparticle surface and biotinylated target molecule. The rAv–AuNP conjugate shows fast and free diffusion in supported lipid bilayers (2–3 μm2/s for rAv–AuNP sizes of 10–40 nm), which is comparable to the diffusion of dye-labeled lipids, indicating that the adverse size and cross-linking effects are successfully avoided. Our work shows that the measured diffusion of the membrane molecule is highly sensitive to the molecular design of the cross-linker for labeling. The demonstrated approach of monovalent and oriented AuNP labeling provides the opportunity to study single-molecule membrane dynamics at much higher spatiotemporal resolutions and, most importantly, without labeling artifacts.This work is selected as 2019 Significant Research Achievement of Academia Sinica and reported by ACS Nano Perspective (Yanqi Yu, Miao Li, Yan Yu. Tracking Single Molecules in Biomembranes: Is Seeing Always Believing?. ACS Nano 2019, 13 (10) , 10860-10868.)
Huan-Cheng Chang
Nitrogen-Vacancy Centers in Diamond for High-Performance Detection of Vacuum Ultraviolet, Extreme Ultraviolet, and X‑rays

Hsiao-Chi Lu,†,* Jen-Iu Lo, Yu-Chain Peng, Sheng-Lung Chou, Bing-Ming Cheng,†,* and Huan-Cheng Chang‡,*

National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 300, Taiwan
Institute of Atomic and Molecular Sciences, Academia Sinica, 1 Section 4, Roosevelt Road, Taipei 106, Taiwan

Fluorescent nanodiamond (FND) containing nitrogen-vacancy (NV) centers as built-in fluorophores exhibits a nearly constant emission profile over 550 – 750 nm upon excitation by vacuum-ultraviolet (VUV), extreme ultraviolet (EUV), and X- radiations from a synchrotron source over the energy (wavelength) range of 6.2 – 1450 eV (0.86 – 200 nm).  The photoluminescence (PL) quantum yield of FND increases steadily with the increasing excitation energy, attaining a value as great as 1700% at 700 eV (1.77 nm).  Notably, the yield curve is continuous, having no gap in the VUV to X-ray region.  In addition, no significant PL intensity decreases were observed for hours.  Applying the FND sensor to measure the absorption cross sections of gaseous O2 over 110 – 200 nm and comparing the measurements with the sodium-salicylate scintillator, we obtained results in agreement with each other within 5%.  The superb photostability and broad applicability of FND offer a promising solution for the long-standing problem of lacking a robust and reliable detector for VUV, EUV, and X- radiations.
Pei-Ling Luo
Simultaneous determination of transient free radicals and reaction kinetics by high-resolution time-resolved dual-comb spectroscopy
Pei-Ling Luo* & Er-Chien Horng
Quantitative determination of multiple transient species is critical in investigating reaction mechanisms and kinetics under various conditions. Dual-comb spectroscopy, a comb-laser-based multi-heterodyne interferometric technique that enables simultaneous achievement of broadband, high-resolution, and rapid spectral acquisition, opens a new era of time-resolved spectroscopic measurements. Employing an electro-optic dual-comb spectrometer with central wavelength near 3 µm coupled with a Herriott multipass absorption cell, here we demonstrate simultaneous determination of multiple species, including methanol, formaldehyde, HO2 and OH radicals, and investigate the reaction kinetics. In addition to quantitative spectral analyses of high-resolution and tens of microsecond time-resolved spectra recorded upon flash photolysis of precursor mixtures, we determine a rate coefficient of the HO2 + NO reaction by directly detecting both HO2 and OH radicals. Our approach exhibits potential in discovering reactive intermediates and exploring complex reaction mechanisms, especially those of radical-radical reactions.
Tsyr-Yan Yu
Biophysical characterization and modulation of Transthyretin Ala97Ser
Yo-Tsen Liu, Yueh-Jung Yen, Frans Ricardo, Yu Chang, Pei-Hao Wu, Shing-Jong Huang, Kon-Ping Lin*,Tsyr-Yan Yu*
Objective: Ala97Ser (A97S) is the major transthyretin (TTR) mutation in Taiwanese patients of familial amyloid polyneuropathy (FAP), characterized by a late-onset but rapidly deteriorated neuropathy. Tafamidis can restore the stability of some mutant TTR tetramers and slow down the progression of TTR-FAP. However, there is little understanding of the biophysical features of A97S-TTR mutant and the pharmacological modulation effect of tafamidis on it. This study aims to delineate the biophysical characteristics of A97S-TTR and the pharmacological modulation effect of tafamidis on this mutant.Method: The stability of TTR tetramers was assessed by urea denaturation and differential scanning calorimetry. Isothermal titration calorimetry (ITC) was used to measure the binding constant of tafamidis to TTR. Nuclear magnetic resonance spectroscopy (NMR) titration experiment was used to map out the tafamidis binding site.Results: Chemical and thermal denaturation confirmed the destabilization effect of A97S. In consistent with other amyloidogenic mutant, A97S-TTR has slightly lower conformational stability. NMR revealed the binding site of A97S-TTR with tafamidis is at the thyroxine binding pocket. The ITC experiments documented the high affinity of the binding which can effectively stabilize the A97S-TTR tetramer.Interpretation: This study confirmed the structural modulation effect of tafamidis on A97S-TTR and implied the potential therapeutic benefit of tafamidis for A97S TTR-FAP. This approach can be applied to investigate the modulation effect of tafamidis on other rare TTR variants and help to make individualized choices of available treatments for FAP patients.
Kaito Takahashi
Odd-Even Reactivity Variation due to Dynamical Effects around the Roaming Saddle Point of the Reaction Between Cn- Chain (n =2-8) and H2
Daisuke Yoshida*, and Kaito Takahashi*
Unsaturated carbon cluster chains often have chemical properties depending on the cluster size. While carbon cluster cation chains show odd−even variation in the reactivity with hydrogen, thechemistry of the carbon anion chain has been poorly understood even for the bimolecular reaction with hydrogen. We present a systematic theoretical study based on transition state calculations and molecular dynamics trajectory simulations for the reaction of Cn (n = 2−8) + H2. We show that carbon cluster chain anion also has an odd−even variation in reactivity where the even ones are more reactive. In addition, dynamics trajectory shows that while odd n only resulted in the CnH2 product with direct H insertion similar to the static reaction pathway, even n had a more complex product branching producing not only CnH2 but also CnH + H and HCnH with the roaming of an H atom. The flexibility of the carbon’s valence electrons plays an important role to form different isomers of the double H adducts HCnH− and CnH− from the roaming condition.
Wen-Bih Tzeng
Rydberg state mediated multiphoton ionization of (η7-C7H7)(η5-C5H5)Cr: DFT-supported experimental insights into the molecular and electronic structures of excited sandwich complexes
Sergey Yu. Ketkov*, Sheng Yuan Tzeng, Elena A. Rychagova, Lyubov’V. Kalakutskaya, Marco Fuss, Holger Braunschweig and Wen-Bih Tzeng*
The resonance-enhanced multiphoton ionization (REMPI) of a mixed sandwich complex has been achieved for the first time when exciting (η7-C7H7)(η5-C5H5)Cr via the Rydberg 4pz state. The REMPI spectrum is indicative of unexpectedly small changes of the sandwich geometry on excitation. Time- dependent DFT calculations reveal fine effects of the ligand nature on the molecular and electronic structure variations accompanying electronic excitation. Different trends are predicted for the sandwich geometry transformations in the mixed sandwich complex and its symmetric isomer, (η6-C6H6)2Cr, both on Rydberg excitation and ionization.
Jim Jr-Min Lin
Water Vapor Does Not Catalyze the Reaction between Methanol and OH Radicals
Wen Chao, Jim Jr-Min Lin, Kaito Takahashi, Alexandre Tomas, Lu Yu, Yoshizumi Kajii, Sébastien Batut, Coralie Schoemaecker and Christa Fittschen
Recent reports [Jara‐Toro et al., Angew. Chem. Int. Ed. 2017, 56, 2166 and PCCP 2018, 20, 27885] suggest that the rate coefficient of OH reactions with alcohols would increase by up to two times in going from dry to high humidity. This finding would have an impact on the budget of alcohols in the atmosphere and it may explain differences in measured and modeled methanol concentrations. The results were based on a relative technique carried out in a small Teflon bag, which might suffer from wall reactions. The effect was reinvestigated using a direct fluorescence probe of OH radicals, and no catalytic effect of H2O could be found. Experiments in a Teflon bag were also carried out, but the results of Jara‐Toro et al. were not reproducible. Further theoretical calculations show that the water‐mediated reactions have negligible rates compared to the bare reaction and that even though water molecules can lower the barriers of reactions, they cannot make up for the entropy cost.