共查询到20条相似文献,搜索用时 31 毫秒
1.
Many physical, chemical, and biological processes happen in liquid-vapor interface and are profoundly influenced with the local microstructures. In contrast to the liquid bulk, molecular orientation is the remarkable one of asymmetric structural features of the interface. Here we report an experimental method, namely, electron-impact time-delayed mass spectrometry and give a brief review about our recent progresses. This brand-new method not only enables us to have more insights into the interfacial structures, as done with small-angle X-ray and neutron scatterings and vibrational sum frequency generation spectroscopy, but also provides opportunity to explore the electron-driven chemical reactions therein.
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2.
The issues of low crystallinity and slow crystallization rate of poly(lactic acid) (PLA) have been widely addressed. In this work, we find that doping PLA with Zn(Ⅱ) ions can speed up the process of crystallization of PLA. Three kinds of Zn(Ⅱ) salts (ZnCl\begin{document}$ _2 $\end{document} , ZnSt and ZnOAc) were tested in comparison with some other ions such as Mg(Ⅱ) and Ca(Ⅱ). The increased crystallinity and crystallization rate of PLA doping with Zn(Ⅱ) are reflected in FT-IR and variable temperature Raman spectroscopy. The crystallinity is further confirmed or measured with differential scanning calorimetry and X-ray diffraction. The crystallinity rate of the PLA/ZnSt-0.4 wt% material can reach 22.46% and the crystallinity rate of the PLA/ZnOAc-0.4 wt% material can reach 24.83%, as measured with differential scanning calorimetry.![]()
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3.
Advanced Techniques for Quantum-State Specific Reaction Dynamics of Gas Phase Metal Atoms?
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One of the themes of modern molecular reaction dynamics is to characterize elementary chemical reactions from "quantum state to quantum state", and the study of molecular reaction dynamics in excited states can help test the validity of modern chemical theories and provide methods to control chemical reactions. The subject of this review is to describe the recent experimental techniques used to study the reaction dynamics of metal atoms in the gas phase. Through these techniques, information such as the internal energy distribution and angular distribution of the nascent products or the three-dimensional stereodynamic reactivity can be obtained. In addition, by preparing metal atoms with specific excited electronic states or orbital arrangements, information about the reactivity of the electronic states enriches the relevant understanding of the electron transfer mechanism in metal reaction dynamics.
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4.
Ion-Neutral Photofragment Coincidence Imaging of Photodissociation Dynamics of Ionic Species
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Ze-feng Hua Yun-xiao Zhao You-qing Li Gao-ming Hu Yang Chen Dong-feng Zhao 《化学物理学报(中文版)》2021,34(1):81-86
The recently constructed cryogenic cylindrical ion trap velocity map imaging spectrometer (CIT-VMI) has been upgraded for coincidence imaging of both ionic and neutral photofragments from photodissociation of ionic species. The prepared ions are cooled down in a home-made cryogenic cylindrical ion trap and then extracted for photodissociation experiments. With the newly designed electric fields for extraction and acceleration, the ion beam can be accelerated to more than 4500 eV, which is necessary for velocity imaging of the neutral photofragments by using the position-sensitive imaging detector. The setup has been tested by the 355 nm photodissociation dynamics of the argon dimer cation (Ar\begin{document}$_2$\end{document} \begin{document}$^+$\end{document} ). From the recorded experimental images of both neutral Ar and ionic Ar\begin{document}$^+$\end{document} fragments, we interpret velocity resolutions of \begin{document}$\Delta v/v$\end{document} \begin{document}$\approx$\end{document} 4.6% for neutral fragments, and \begin{document}$\Delta v/v$\end{document} \begin{document}$\approx$\end{document} 1.5% for ionic fragments, respectively.![]()
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5.
Two-dimensional electronic spectroscopy (2DES) is a powerful method to probe the coherent electron dynamics in complicated systems. Stabilizing the phase difference of the incident ultrashort pulses is the most challenging part for experimental demonstration of 2DES. Here, we present a tutorial review on the 2DES protocols based on active phase managements which are originally developed for quantum optics experiments. We introduce the 2DES techniques in box and pump-probe geometries with phase stabilization realized by interferometry, and outline the fully collinear 2DES approach with the frequency tagging by acoustic optical modulators and frequency combs. The combination of active phase managements, ultrashort pulses and other spectroscopic methods may open new opportunities to tackle essential challenges related to excited states.
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6.
Infrared Spectroscopy of Neutral Clusters Based on a Vacuum Ultraviolet Free Electron Laser?
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Gang Li Chong Wang Hui-jun Zheng Tian-tong Wang Hua Xie Xue-ming Yang Ling Jiang 《化学物理学报(中文版)》2021,34(1):51-60
Spectroscopic characterization of clusters is crucial to understanding the structures and reaction mechanisms at the microscopic level, but it has been proven to be a grand challenge for neutral clusters because the absence of a charge makes it difficult for the size selection and detection. Infrared (IR) spectroscopy based on threshold photoionization using a tunable vacuum ultraviolet free electron laser (VUV-FEL) has recently been developed in the lab. The IR-VUV depletion and IR+VUV enhancement spectroscopic techniques open new avenues for size-selected IR spectroscopies of a large variety of neutral clusters without confinement (i.e., an ultraviolet chromophore, a messenger tag, or a host matrix). The spectroscopic principles have been demonstrated by investigations of some neutral water clusters and some metal carbonyls. Here, the spectroscopic principles and their applications for neutral clusters are reviewed.
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7.
Fabrication of SERS-Active Au@Au@Ag Double Shell Nanoparticles for Low-Abundance Pigment Detection
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Au@Au@Ag double shell nanoparticles were fabricated and characterized using TEM, STEM-mapping and UV-Vis methods. Using crystal violet as Raman probe, the surface-enhanced Raman scattering (SERS) activity of the as-prepared Au@Au@Ag nanoparticles was studied by comparing to Au, Au@Ag and Au@Au core-shell nanoparticles which were prepared by the same methods. Moreover, it can be found that the SERS activity was enhanced obviously by introduction of NaCl and the concentrations of NaCl played a key role in SERS detection. With an appropriate concentration of NaCl, the limit of detection as low as 10\begin{document}$ ^{-10} $\end{document} mol/L crystal violet can be achieved. The possible enhanced mechanism was also discussed. Furthermore, with simple sample pretreatment, the detection limit of 5 μg/g Rhodamine B (RhB) in chili powders can be achieved. The results highlight the potential utility of Au@Au@Ag for detection of illegal food additives with low concentrations.![]()
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8.
Si-yu Qian Bei-bei Feng Yi-tong Zhai Wei Zhao Lei Wang Cheng-cheng Ao Yi Liu Jing Liu Li-dong Zhang 《化学物理学报(中文版)》2021,34(1):102-111
To obtain insight into the catalytic reaction mechanism of biodiesels over ZSM-5 zeolites, the pyrolysis and catalytic pyrolysis of methyl butanoate, a biodiesel surrogate, with H-type ZSM-5 (HZSM-5) were performed in a flow reactor under atmospheric pressure. The pyrolysis products were identified and quantified using gas chromatography-mass spectrometry (GC-MS). Kinetic modelling and experimental results revealed that H-atom abstraction in the gas phase was the primary pathway for methyl butanoate decomposition during pyrolysis, but dissociating to ketene and methanol over HZSM-5 was the primary pathway for methyl butanoate consumption during catalytic pyrolysis. The initial decomposition temperature of methyl butanoate was reduced by approximately 300 K over HZSM-5 compared to that for the uncatalyzed reaction. In addition, the apparent activation energies of methyl butanoate under catalytic pyrolysis and homogeneous pyrolysis conditions were obtained using the Arrhenius equation. The significantly reduced apparent activation energy confirmed the catalytic performance of HZSM-5 for methyl butanoate pyrolysis. The activation temperature may also affect some catalytic properties of HZSM-5. Overall, this study can be used to guide subsequent catalytic combustion for practical biodiesel fuels.![]()
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9.
Bias-Polarity Dependent Electroluminescence from a Single Platinum Phthalocyanine Molecule
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Aftab Farrukh Xiao-jun Tian Fan-fang Kong Yun-jie Yu Shi-hao Jing Gong Chen Yao Zhang Yuan Liao Yang Zhang Zhen-chao Dong 《化学物理学报(中文版)》2021,34(1):87-94
By using scanning tunneling microscope induced luminescence (STML) technique, we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine (PtPc) molecule and the electron excitation mechanisms behind. The molecule is found to emit light at both bias polarities but with different emission energies. At negative excitation bias, only the fluorescence at 637 nm is observed, which originates from the LUMO→HOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions. Strong fluorescence in region (Ⅰ) is excited by the carrier injection mechanism with holes injected into the HOMO state first; moderate fluorescence in region (Ⅱ) is excited by the inelastic electron scattering mechanism; and weak fluorescence in region (Ⅲ) is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spin-triplet relay state. At positive excitation bias, more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated. The sharp molecule-specific emission peak at ~911 nm is attributed to the anionic emission of PtPc\begin{document}$^-$\end{document} originated from the LUMO+1→LUMO transition, whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.![]()
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11.
Liang-sheng Duan Quan-ping Wu Yuan-yuan Xu Hui Wang Zhe Sun Yu Chen Song Xue 《化学物理学报(中文版)》2021,34(2):217-226
Four organic small-molecule hole transport materials ( D41 , D42 , D43 and D44 ) of tetraarylpyrrolo[3, 2-b]pyrroles were prepared. They can be used without doping in the manufacture of the inverted planar perovskite solar cells. Tetraarylpyrrolo[3, 2-b]pyrroles are accessible for one-pot synthesis. D42 , D43 and D44 possess acceptor-\begin{document}$ \pi $\end{document} -donor-\begin{document}$ \pi $\end{document} -acceptor structure, on which the aryl bearing substitutes of cyan, fluorine and trifluoromethyl, respectively. Instead, the aryl moiety of D41 is in presence of methyl with a donor-\begin{document}$ \pi $\end{document} -donor-\begin{document}$ \pi $\end{document} -donor structure. The different substitutes significantly affected their molecular surface charge distribution and thin-film morphology, attributing to the electron-rich properties of fused pyrrole ring. The size of perovskite crystalline growth particles is affected by different molecular structures, and the electron-withdrawing cyan group of D42 is most conducive to the formation of large perovskite grains. The D42 fabricated devices with power conversion efficiency of 17.3% and retained 55% of the initial photoelectric conversion efficiency after 22 days in dark condition. The pyrrolo[3, 2-b]pyrrole is efficient electron-donating moiety for hole transporting materials to form good substrate in producing perovskite thin film.
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12.
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13.
Guo-dong Wang Zhi-xing Liu Bei-bei Qiu Zhi-guo Zhang Rui Wang Xiao-yong Wang Jing Ma Yong-fang Li Min Xiao Chun-feng Zhang 《化学物理学报(中文版)》2021,34(6):751-760
14.
NH\begin{document}$ _\textbf{2} $\end{document} -MIL-53(Al) for Simultaneous Removal and Detection of Fluoride Anions
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To address the limitations of the separate fluoride removal or detection in the existing materials, herein, amino-decorated metal organic frameworks NH\begin{document}$ _2 $\end{document} -MIL-53(Al) have been succinctly fabricated by a sol-hydrothermal method for simultaneous removal and determination of fluoride. As a consequence, the proposed NH\begin{document}$ _2 $\end{document} -MIL-53(Al) features high uptake capacity (202.5 mg/g) as well as fast adsorption rate, being capable of treating 5 ppm of fluoride solution to below the permitted threshold in drinking water within 15 min. Specifically, the specific binding between fluoride and NH\begin{document}$ _2 $\end{document} -MIL-53(Al) results in the release of fluorescent ligand NH\begin{document}$ _2 $\end{document} -BDC, conducive to the determination of fluoride via a concentration-dependent fluorescence enhancement effect. As expected, the resulting NH\begin{document}$ _2 $\end{document} -MIL-53(Al) sensor exhibits selective and sensitive detection (with the detection limit of 0.31 \begin{document}$ \mu $\end{document} mol/L) toward fluoride accompanied with a wide response interval (0.5-100 \begin{document}$ \mu $\end{document} mol/L). More importantly, the developed sensor can be utilized for fluoride detection in practical water systems with satisfying recoveries from 89.6% to 116.1%, confirming its feasibility in monitoring the practical fluoride-contaminated waters.
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15.
Min Zhao Zhen-xing Li Ting Xie Yao Chang Fu-yan Wu Qin Wang Wen-tao Chen Tao Wang Xing-an Wang Kai-jun Yuan Xue-ming Yang 《化学物理学报(中文版)》2021,34(1):95-101
We study the photodissociation dynamics of CS\begin{document}$_2$\end{document} in the ultraviolet region using the time-sliced velocity map ion imaging technique. The S(\begin{document}$^3$\end{document} P\begin{document}$_J$\end{document} )+CS(\begin{document}$X^1\Sigma^+$\end{document} ) product channels were observed and identified at four wavelengths of 201.36, 203.10, 204.85 and 206.61 nm. In the measured images of S(\begin{document}$^3$\end{document} P\begin{document}$_{J=2, 1, 0}$\end{document} ), the vibrational states of the CS(\begin{document}$X^1\Sigma^+$\end{document} ) co-products were partially resolved and the vibrational state distributions were determined. Moreover, the product total kinetic energy releases and the anisotropic parameters were derived. The relatively small anisotropic parameter values indicate that the S(\begin{document}$^3$\end{document} P\begin{document}$_{J=2, 1, 0}$\end{document} )+CS(\begin{document}$X^1\Sigma^+$\end{document} ) channels are very likely formed via the indirect predissociation process of CS\begin{document}$_2$\end{document} . The study of the S(\begin{document}$^3$\end{document} P\begin{document}$_{J=2, 1, 0}$\end{document} )+CS(\begin{document}$X^1\Sigma^+$\end{document} ) channels, which come from the spin-orbit coupling dissociation process of CS\begin{document}$_2$\end{document} , shows that nonadiabatic process plays a role in the ultraviolet photodissociation of CS\begin{document}$_2$\end{document} .![]()
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16.
The photophysical and photochemical behaviors of thioxanthen-9-one (TX) in different solvents have been studied using nanosecond transient absorption spectroscopy. A unique absorption of the triplet state \begin{document}$ ^3 $\end{document} TX\begin{document}$ ^* $\end{document} is observed, which involves two components, \begin{document}$ ^3 $\end{document} n\begin{document}$ \pi $\end{document} \begin{document}$ ^* $\end{document} and \begin{document}$ ^3 $\end{document} \begin{document}$ \pi\pi^* $\end{document} states. The \begin{document}$ ^3 $\end{document} \begin{document}$ \pi\pi^* $\end{document} component contributes more to the \begin{document}$ ^3 $\end{document} TX\begin{document}$ ^* $\end{document} when increasing the solvent polarity. The self-quenching rate constant \begin{document}$ k_{ \rm{sq}} $\end{document} of \begin{document}$ ^3 $\end{document} TX\begin{document}$ ^* $\end{document} is decreased in the order of CH\begin{document}$ _3 $\end{document} CN, CH\begin{document}$ _3 $\end{document} CN/CH\begin{document}$ _3 $\end{document} OH (1:1), and CH\begin{document}$ _3 $\end{document} CN/H\begin{document}$ _2 $\end{document} O (1:1), which might be caused by the exciplex formed from hydrogen bond interaction. In the presence of diphenylamine (DPA), the quenching of \begin{document}$ ^3 $\end{document} TX\begin{document}$ ^* $\end{document} happens efficiently via electron transfer, producing the TX\begin{document}$ ^\cdot $\end{document} \begin{document}$ ^- $\end{document} anion and DPA\begin{document}$ ^{\cdot} $\end{document} \begin{document}$ ^+ $\end{document} cation radicals. Because of insignificant solvent effects on the electron transfer, the electron affinity of the \begin{document}$ ^3 $\end{document} n\begin{document}$ \pi $\end{document} \begin{document}$ ^* $\end{document} state is proved to be approximately equal to that of the \begin{document}$ ^3 $\end{document} \begin{document}$ \pi\pi^* $\end{document} state. However, a solvent dependence is found in the dynamic decay of TX\begin{document}$^{{ \cdot ^ - }}$\end{document} anion radical. In the strongly acid aqueous acetonitrile (pH = 3.0), a dynamic equilibrium between protonated and unprotonated TX is definitely observed. Once photolysis, \begin{document}$ ^3 $\end{document} TXH\begin{document}$ ^{+*} $\end{document} is produced, which contributes to the new band at 520 nm.![]()
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17.
Intra- and Intermolecular Rovibrational States of HCl-H\begin{document}$ _\textbf{2} $\end{document} O and DCl-H\begin{document}$ _\textbf{2} $\end{document} O Dimers from Full-Dimensional and Fully Coupled Quantum Calculations
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18.
19.
Imaging HNCO Photodissociation at 201 nm: State-to-State Correlations between CO (\begin{document}$X^1{\Sigma}^+$\end{document} ) and NH (\begin{document}${a}^1{\Delta}$\end{document} )
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Zhi-guo Zhang Min Xin Yan-ning Wu Shu-tao Zhao Yi-jia Tang Yang Chen 《化学物理学报(中文版)》2018,31(6):735-740
The NH(\begin{document}$a^1$\end{document} \begin{document}$\Delta$\end{document} )+CO(\begin{document}$X^1$\end{document} \begin{document}$\Sigma^+$\end{document} ) product channel for the photodissociation of isocyanic acid (HNCO) on the first excited singlet state S\begin{document}$_1$\end{document} has been investigated by means of time-sliced ion velocity map imaging technique at photolysis wavelengths around 201 nm. The CO product was detected through (2+1) resonance enhanced multiphoton ionization (REMPI). Images were obtained for CO products formed in the ground and vibrational excited state (\begin{document}$v$\end{document} =0 and \begin{document}$v$\end{document} =1). The energy distributions and product angular distributions were obtained from the CO velocity imaging. The correlated NH(\begin{document}$a^1\Delta$\end{document} ) rovibrational state distributions were determined. The vibrational branching ratio of \begin{document}$^1$\end{document} NH (\begin{document}$v$\end{document} =1/\begin{document}$v$\end{document} =0) increases as the rotational state of CO(\begin{document}$v$\end{document} =0) increases initially and decreases afterwards, which indicates a special state-to-state correlation between the \begin{document}$.1$\end{document} NH and CO products. About half of the available energy was partitioned into the translational degree of freedom. The negative anisotropy parameter \begin{document}$\beta$\end{document} indicates that it is a vertical direct dissociation process. 相似文献
20.
In this work, we used time-sliced ion velocity imaging to study the photodissociation dynamics of MgO at \mbox{193 nm}. Three dissociation pathways are found through the speed and angular distributions of magnesium. One pathway is the one-photon excitation of MgO(X\begin{document}$^1\Sigma^+$\end{document} ) to MgO(G\begin{document}$^1\Pi$\end{document} ) followed by spin-orbit coupling between the G\begin{document}$^1\Pi$\end{document} , 3\begin{document}$^3\Pi$\end{document} and 1\begin{document}$^5\Pi$\end{document} states, and finally dissociated to the Mg(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{u}$\end{document} )+O(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{g}$\end{document} ) along the 1\begin{document}$^5\Pi$\end{document} surface. The other two pathways are one-photon absorption of MgO(A\begin{document}$^1\Pi$\end{document} ) state to MgO(G\begin{document}$^1\Pi$\end{document} ) and MgO(4\begin{document}$^1\Pi$\end{document} ) state to dissociate into Mg(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{u}$\end{document} )+O(\begin{document}$^3$\end{document} P\begin{document}$_\textrm{g}$\end{document} ) and Mg(\begin{document}$^1$\end{document} S\begin{document}$_\textrm{g}$\end{document} )+O(\begin{document}$^1$\end{document} S\begin{document}$_\textrm{g}$\end{document} ), respectively. The anisotropy parameters of the dissociation pathways are related to the lifetime of the vibrational energy levels and the coupling of rotational and vibronic spin-orbit states. The total kinetic energy analysis gives \begin{document}$D_0$\end{document} (Mg\begin{document}$-$\end{document} O)=21645\begin{document}$\pm$\end{document} 50 cm\begin{document}$^{-1}$\end{document} . 相似文献