Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 104
Filter
Add more filters

Publication year range
1.
Opt Express ; 32(7): 11643-11653, 2024 Mar 25.
Article in English | MEDLINE | ID: mdl-38571006

ABSTRACT

The radiation characteristics of microalgae are of great significance for the design of photobioreactors and ocean optical remote sensing. Yet the complex structure of microalgae makes it difficult to theoretically predict its radiation characteristics based on traditional Mie theory. In this work, taking Chlamydomonas reinhardtii as an example, a multi-component cell model with a complex structure is proposed, which considers the organelles and shape of microalgae, and the volume change during the production of Chlamydomonas reinhardtii lipids. The theoretical calculation is carried out using the discrete dipole approximation method, and an improved transmission method is used for experimental measurement. The experimental data are compared and analyzed with the multi-component complex structure model, the homogeneous sphere model and the coated sphere model. The results show that the calculation accuracy of the multi-component complex structure model is higher, the error of the scattering cross-section is reduced by more than 8.6% compared with the homogeneous sphere model and coated sphere model, and the absorption cross-section and the scattering phase function are in good agreement with the experimental results. With the increase of lipids, the absorption cross-section and the scattering phase function vary slightly. However, the scattering cross-section has an observed change with increasing wavelength. In addition, the theoretical calculation error can be reduced when the influence of the culture medium is taken into account.

2.
Nanotechnology ; 35(36)2024 Jun 20.
Article in English | MEDLINE | ID: mdl-38848693

ABSTRACT

Aqueous aluminum-ion batteries have many advantages such as their safety, environmental friendliness, low cost, high reserves and the high theoretical specific capacity of aluminum. So aqueous aluminum-ion batteries are potential substitute for lithium-ion batteries. In this paper, the current research status and development trends of cathode and anode materials and electrolytes for aqueous aluminum-ion batteries are described. Aiming at the problem of passivation, corrosion and hydrogen evolution reaction of aluminum anode and dissolution and irreversible change of cathode after cycling in aqueous aluminum-ion batteries. Solutions of different research routes such as ASEI (artificial solid electrolyte interphase), alloying, amorphization, elemental doping, electrolyte regulation, etc and different transformation mechanisms of anode and cathode materials during cycling have been summarized. Moreover, it looks forward to the possible research directions of aqueous aluminum-ion batteries in the future. We hope that this review can provide some insights and support for the design of more suitable electrode materials and electrolytes for aqueous aluminum-ion batteries.

3.
Opt Express ; 31(11): 18026-18038, 2023 May 22.
Article in English | MEDLINE | ID: mdl-37381521

ABSTRACT

Most of the current predictions of the radiative properties of microalgae use the homogeneous sphere approximation based on the Mie scattering theory, and the refractive indices of the model were regarded as fixed values. Using the recently measured optical constants of various microalgae components, we propose a spherical heterogeneous model for spherical microalgae. The optical constants of the heterogeneous model were characterized by the measured optical constants of microalgae components for the first time. The radiative properties of the heterogeneous sphere were calculated using the T-matrix method and were well verified by measurements. It shows that the internal microstructure has a more significant effect on scattering cross-section and scattering phase function than absorption cross-section. Compared with the traditional homogeneous models selected with fixed values as refractive index, the calculation accuracy of scattering cross-section of the heterogeneous model improved by 15%-150%. The scattering phase function of the heterogeneous sphere approximation agreed better with measurements than the homogeneous models due to the more detailed description of the internal microstructure. It can be concluded that considering the internal microstructure of microalgae and characterizing the microstructure of the model by the optical constants of the microalgae components helps to reduce the error caused by the simplification of the actual cell.

4.
Opt Express ; 31(8): 12357-12366, 2023 Apr 10.
Article in English | MEDLINE | ID: mdl-37157397

ABSTRACT

Ferroelectric BaTiO3 with an electric-field-switchable spontaneous polarization has attracted wide attention in photovoltaic applications due to its efficient charge separation for photoexcitation. The evolution of its optical properties with rising temperature especially across the ferroelectric-paraelectric phase transition is critical to peer into the fundamental photoexcitation process. Herein, by combining spectroscopic ellipsometry measurements with first-principles calculations, we obtain the UV-Vis dielectric functions of perovskite BaTiO3 at temperatures varying from 300 to 873 K and provide the atomistic insights into the temperature-driven ferroelectric-paraelectric (tetragonal-cubic) structural evolution. The main adsorption peak in dielectric function of BaTiO3 is reduced by 20.6% in magnitude and redshifted as temperature increases. The Urbach tail shows an unconventional temperature-dependent behavior due to the microcrystalline disorder across the ferroelectric-paraelectric phase transition and the decreased surface roughness at around 405 K. From ab initio molecular dynamics simulations, the redshifted dielectric function of ferroelectric BaTiO3 coincidences with the reduction of the spontaneous polarization at elevated temperature. Moreover, a positive (negative) external electric field is applied which can modulate the dielectric function of ferroelectric BaTiO3 blueshift (redshift) with a larger (smaller) spontaneous polarization since it drives the ferroelectric further away from (closer to) the paraelectric structure. This work sheds light on the temperature-dependent optical properties of BaTiO3 and provides data support for advancing its ferroelectric photovoltaic applications.

5.
Opt Express ; 31(24): 40765-40780, 2023 Nov 20.
Article in English | MEDLINE | ID: mdl-38041369

ABSTRACT

ß-Ga2O3 as an ultra-wide bandgap material is widely used in space missions and nuclear reactor environments. It is well established that the physical properties of ß-Ga2O3 would be affected by radiation damage and temperature in such application scenarios. Defects are inevitably created in ß-Ga2O3 upon irradiation and their dynamic evolution is positively correlated with the thermal motion of atoms as temperature increases. This work utilizes first-principles calculations to investigate how temperature influences the electronic and optical properties of ß-Ga2O3 after radiation damage. It finds that the effect of p-type defects caused by Ga vacancies on optical absorption diminishes as temperature increases. The high temperature amplifies the effect of oxygen vacancies to ß-Ga2O3, however, making n-type defects more pronounced and accompanied by an increase in the absorption peak in the visible band. The self-compensation effect varies when ß-Ga2O3 contains both Ga vacancies and O vacancies at different temperatures. Moreover, in the case of Ga3- (O2+) vacancies, the main characters of p(n)-type defects caused by uncharged Ga0 (O0) vacancies disappear. This work aims to understand the evolution of physical properties of ß-Ga2O3 under irradiation especially at high temperatures, and help analyze the damage mechanism in ß-Ga2O3-based devices.

6.
Environ Sci Technol ; 57(33): 12465-12475, 2023 08 22.
Article in English | MEDLINE | ID: mdl-37556316

ABSTRACT

The low-temperature mechanism of chabazite-type small-pore Cu-SSZ-13 zeolite, a state-of-the-art catalyst for ammonia-assisted selective reduction (NH3-SCR) of toxic NOx pollutants from heavy-duty vehicles, remains a debate and needs to be clarified for further improvement of NH3-SCR performance. In this study, we established experimental protocols to follow the dynamic redox cycling (i.e., CuII ↔ CuI) of Cu sites in Cu-SSZ-13 during low-temperature NH3-SCR catalysis by in situ ultraviolet-visible spectroscopy and in situ infrared spectroscopy. Further integrating the in situ spectroscopic observations with time-dependent density functional theory calculations allows us to identify two cage-confined transient states, namely, the O2-bridged Cu dimers (i.e., µ-η2:η2-peroxodiamino dicopper) and the proximately paired, chemically nonbonded CuI(NH3)2 sites, and to confirm the CuI(NH3)2 pair as a precursor to the O2-bridged Cu dimer. Comparative transient experiments reveal a particularly high reactivity of the CuI(NH3)2 pairs for NO-to-N2 reduction at low temperatures. Our study demonstrates direct experimental evidence for the transient formation and high reactivity of proximately paired CuI sites under zeolite confinement and provides new insights into the monomeric-to-dimeric Cu transformation for completing the Cu redox cycle in low-temperature NH3-SCR catalysis over Cu-SSZ-13.


Subject(s)
Zeolites , Density Functional Theory , Zeolites/chemistry , Oxidation-Reduction , Spectrophotometry, Infrared , Catalysis , Ammonia/chemistry
7.
Environ Sci Technol ; 57(42): 16121-16130, 2023 10 24.
Article in English | MEDLINE | ID: mdl-37842921

ABSTRACT

Ammonia-mediated selective catalytic reduction (NH3-SCR) is currently the key approach to abate nitrogen oxides (NOx) emitted from heavy-duty lean-burn vehicles. The state-of-art NH3-SCR catalysts, namely, copper ion-exchanged chabazite (Cu-CHA) zeolites, perform rather poorly at low temperatures (below 200 °C) and are thus incapable of eliminating effectively NOx emissions under cold-start conditions. Here, we demonstrate a significant promotion of low-temperature NOx reduction by reinforcing the dynamic motion of zeolite-confined Cu sites during NH3-SCR. Combining complex impedance-based in situ spectroscopy (IS) and extended density-functional tight-binding molecular dynamics simulation, we revealed an environment- and temperature-dependent nature of the dynamic Cu motion within the zeolite lattice. Further coupling in situ IS with infrared spectroscopy allows us to unravel the critical role of monovalent Cu in the overall Cu mobility at a molecular level. Based on these mechanistic understandings, we elicit a boost of NOx reduction below 200 °C by reinforcing the dynamic Cu motion in various Cu-zeolites (Cu-CHA, Cu-ZSM-5, Cu-Beta, etc.) via facile postsynthesis treatments, either in a reductive mixture at low temperatures (below 250 °C) or in a nonoxidative atmosphere at high temperatures (above 450 °C).


Subject(s)
Zeolites , Zeolites/chemistry , Copper , Ammonia/chemistry , Nitrogen Oxides/chemistry , Temperature , Catalysis
8.
Phys Chem Chem Phys ; 25(9): 6746-6756, 2023 Mar 01.
Article in English | MEDLINE | ID: mdl-36807438

ABSTRACT

Nanoscale thermal transport at solid-liquid interfaces plays an essential role in many engineering fields. This work performs deep potential molecular dynamics (DPMD) simulations to investigate thermal transport across copper-water interfaces. Unlike traditional classical molecular dynamics (CMD) simulations, we independently train a deep learning potential (DLP) based on density functional theory (DFT) calculations and demonstrated its high computational efficiency and accuracy. The trained DLP predicts radial distribution functions (RDFs), vibrational densities of states (VDOS), density curves, and thermal conductivity of water confined in the nanochannel at a DFT accuracy. The thermal conductivity decreases slightly with an increase in the channel height, while the influence of the cross-sectional area is negligible. Moreover, the predicted interfacial thermal conductance (ITC) across the copper-water interface by DPMD is 2.505 × 108 W m-2 K-1, the same order of magnitude as the CMD and experimental results but with a high computational accuracy. This work seeks to simulate the thermal transport properties of solid-liquid interfaces with DFT accuracy at large-system and long-time scales.

9.
Phys Chem Chem Phys ; 25(26): 17257-17263, 2023 Jul 05.
Article in English | MEDLINE | ID: mdl-37340828

ABSTRACT

The discovery of ferroelectricity in the fluorite-structure HfO2 has attracted much interest in various applications including electro-optic devices and nonvolatile memories. Doping and alloying not only induce ferroelectricity in HfO2, but also significantly impact the thermal conduction which plays an essential role in the heat dissipation and thermal stability of ferroelectric devices. To understand and regulate the heat transfer in ferroelectric HfO2, it is crucial to investigate the thermal conduction properties of related fluorite-structure ferroelectrics so as to establish the structure-property relationship. In this work, using first-principles calculations, we investigate the thermal transport in twelve fluorite-structure ferroelectrics. We find an overall satisfactory agreement between the calculated thermal conductivities and those predicted by the simple theory of Slack. Among the family of fluorite-structure ferroelectrics, the transition-metal oxides HfO2 and ZrO2 have the highest thermal conductivities due to the strong interatomic bonding. We demonstrate that the spontaneous polarization, a feature specific to ferroelectrics, is positively correlated with the thermal conductivity, namely, the larger the spontaneous polarization, the larger the thermal conductivity. This is of chemical origin, namely, both the spontaneous polarization and the thermal conductivity are positively correlated to the "ionicity" of the ferroelectrics. We further find that the thermal conductivity is several times lower in the ferroelectric solid solution Hf1-xZrxO2 than in its pure counterparts, especially in the thin films where the finite size effect further suppresses thermal conduction. Our findings suggest the spontaneous polarization as a specific criterion for identifying ferroelectrics with desired thermal conductivities, which may promote the design and application of ferroelectrics.

10.
Phys Chem Chem Phys ; 25(14): 10175-10183, 2023 Apr 05.
Article in English | MEDLINE | ID: mdl-36976635

ABSTRACT

The exfoliated two-dimensional (2D) Ga2O3 opens new avenues to fine-tune the carrier and thermal transport properties for improving the electro-thermal performance of gallium oxide-based power electronics with their enhanced surface-to-volume ratios and quantum confinement. Yet, the carrier transport in 2D Ga2O3 has not been fully explored, especially considering their large Fröhlich coupling constants. Herein, we mainly investigate the electron mobility of monolayer (ML) and bilayer (BL) Ga2O3 from first-principles by adding polar optical phonon (POP) scattering. The results show that POP scattering is the dominant factor limiting the electron mobility for 2D Ga2O3, accompanied by a large 'ion-clamped' dielectric constant Δε. The value of Δε is 3.77 and 4.60 for ML and BL Ga2O3, respectively, indicating a large change in polarization in the external field. The electron mobility of 2D Ga2O3 enhances with increasing thickness despite the enhanced electron-phonon coupling strength and Fröhlich coupling constant. The predicted electron mobility for BL and ML Ga2O3 at a carrier concentration of 1.0 × 1012 cm-2 is 125.77 cm2 V-1 s-1 and 68.30 cm2 V-1 s-1 at room temperature, respectively. This work aims to unravel the scattering mechanisms beneath engineering electron mobility of 2D Ga2O3 for promising applications in high-power devices.

11.
Arch Insect Biochem Physiol ; 113(2): e22005, 2023 Jun.
Article in English | MEDLINE | ID: mdl-36802092

ABSTRACT

N6-methyladenosine (m6A) is a ubiquitous reversible epigenetic RNA modification that plays an important role in regulating many biological processes, especially embryonic development. However, regulation of m6A methylation during silkworm embryonic development and diapause remains to be investigated. In this study, we analyzed the phylogeny of subunits of methyltransferases BmMettl3 and BmMettl14, and detected the expression patterns of BmMettl3 and BmMettl14 in different tissues and at different developmental stages in silkworm. To investigate the function of m6A on the development of silkworm embryo, we analyzed the m6A/A ratio in diapause and diapause termination eggs. The results showed that BmMettl3 and BmMettl14 were highly expressed in gonads and eggs. Moreover, the expression of BmMettl3 and BmMettl14 and the m6A/A ratio were significantly increased in diapause termination eggs compared with diapause eggs in the early stage of silkworm embryonic development. Furthermore, in BmN cell cycle experiments, the percentage of cells in the S phase increased when lacking BmMettl3 or BmMettl14. This work contributes to understanding the role of m6A methylation during insect embryogenesis and gametogenesis. It also provides a research orientation to further analyze the role of m6A methylation in diapause initiation and termination during insect embryonic development.


Subject(s)
Bombyx , Methyltransferases , Animals , Methyltransferases/genetics , Methyltransferases/metabolism , Bombyx/metabolism , RNA/metabolism , Epigenesis, Genetic , Embryonic Development/genetics , Gene Expression Regulation, Developmental , Ovum/metabolism
12.
J Chem Phys ; 159(14)2023 Oct 14.
Article in English | MEDLINE | ID: mdl-37811827

ABSTRACT

Water dissociation on TiO2 surfaces has been known for decades and holds great potential in various applications, many of which require a proper understanding of thermal transport across the TiO2-H2O interface. Molecular dynamics (MD) simulations play an important role in characterizing complex systems' interfacial thermal transport properties. Nevertheless, due to the imprecision of empirical force field potentials, the interfacial thermal transport mechanism involving water dissociation remains to be determined. To cope with this, a deep potential (DP) model is formulated through the utilization of ab initio datasets. This model successfully simulates interfacial thermal transport accompanied by water dissociation on the TiO2 surfaces. The trained DP achieves a total energy accuracy of ∼238.8 meV and a force accuracy of ∼197.05 meV/Å. The DPMD simulations show that water dissociation induces the formation of hydrogen bonding networks and molecular bridges. Structural modifications further affect interfacial thermal transport. The interfacial thermal conductance estimated by DP is ∼8.54 × 109 W/m2 K, smaller than ∼13.17 × 109 W/m2 K by empirical potentials. The vibrational density of states (VDOS) quantifies the differences between the DP model and empirical potentials. Notably, the VDOS disparity between the adsorbed hydrogen atoms and normal hydrogen atoms demonstrates the influence of water dissociation on heat transfer processes. This work aims to understand the effect of water dissociation on thermal transport at the TiO2-H2O interface. The findings will provide valuable guidance for the thermal management of photocatalytic devices.

13.
J Chem Phys ; 159(2)2023 Jul 14.
Article in English | MEDLINE | ID: mdl-37428055

ABSTRACT

The vibrationally excited reaction O(1D) + CHD3(ν1 = 1) has been investigated by crossed-molecular-beam experiments with a time-sliced velocity map imaging technique. Detailed and quantitative information is extracted on the C-H stretching excitation effects on the reactivity and dynamics of the title reaction, with the help of preparation of C-H stretching excited CHD3 molecules by direct infrared excitation. Experimental results show that the vibrational stretching excitation of the C-H bond almost does not affect the relative contributions between different dynamical pathways for all product channels. For the OH + CD3 product channel, the vibrational energy of the C-H stretching excited CHD3 reagent is channeled exclusively into the vibrational energy of the OH products. The vibrational excitation of the CHD3 reactant changes the reactivities for the ground-state and umbrella-mode-excited CD3 channels very modestly, while it significantly suppresses the corresponding CHD2 channels. For the CHD2(ν1 = 1) channel, the stretching excited C-H bond of the CHD3 molecule acts almost as a pure spectator.

14.
J Chem Phys ; 158(1): 014301, 2023 Jan 07.
Article in English | MEDLINE | ID: mdl-36610966

ABSTRACT

Structural characterization of neutral water clusters is crucial to understanding the structures and properties of water, but it has been proven to be a challenging experimental target due to the difficulty in size selection. Here, we report the size-specific infrared spectra of confinement-free neutral water nonamer (H2O)9 based on threshold photoionization, using a tunable vacuum ultraviolet free-electron laser. Distinct OH stretch vibrational fundamentals in the 3200-3350 cm-1 region are observed, providing unique spectral signatures for the formation of an unprecedented (H2O)9 structure evolved by adding a ninth water molecule onto a hydrogen bond-unbroken edge of the (H2O)8 octamer with D2d symmetry. This nonamer structure coexists with the five previously identified structures that can be viewed as derived by inserting a ninth water molecule into a hydrogen bond-broken edge of the D2d/S4 octamer. These findings provide key microscopic information for systematic understanding of the formation and growth mechanism of dynamical hydrogen-bonding networks that are responsible for the structure and properties of condensed-phase water.

15.
Angew Chem Int Ed Engl ; 62(30): e202304282, 2023 Jul 24.
Article in English | MEDLINE | ID: mdl-37159106

ABSTRACT

Sulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single-metal-site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self-recovery are first presented on an industrialized single-Rh-site catalyst (Rh1 /POPs). A decreased turnover frequency of Rh1 /POPs from 4317 h-1 to 318 h-1 was observed in a 1000 ppm H2 S co-feed for ethylene hydroformylation, but it self-recovered to 4527 h-1 after withdrawal of H2 S, whereas the rhodium nanoparticles demonstrated poor activity and self-recovery ability. H2 S reduced the charge density of the single Rh atom and lowered its Gibbs free energy with the formation of inactive (SH)Rh(CO)(PPh3 -frame)2 , which could be regenerated to active HRh(CO)(PPh3 -frame)2 after withdrawing H2 S. The mechanism and the sulfur-related structure-activity relationship were highlighted. This work provides an understanding of heterogeneous ethylene hydroformylation and sulfur-poisoned regeneration in the science of single-atom catalysts.

16.
BMC Cancer ; 22(1): 584, 2022 May 27.
Article in English | MEDLINE | ID: mdl-35624419

ABSTRACT

BACKGROUND: B7 molecules play significant roles in regulating tumor immunity, but their expression patterns and immuno-biological correlations in pancreatic cancer (PaCa) have not been fully discussed. METHODS: RNA-sequencing data of B7 molecules of PaCa samples in the Cancer Genome Atlas (TCGA) dataset was downloaded from the UCSC Xena to assess the expression, correlation, and mutation of the B7 family in PaCa. Next, two PaCa tissue microarrays (TMAs, Cat. HPanA150CS02 and HPanA120Su02) were obtained from Outdo BioTech (Shanghai, China). To detect the expression levels of PD-L1, B7-H3 and B7-H4, immunohistochemistry (IHC) staining was performed on these TMAs. RESULTS: Most B7 molecules, including B7-1, B7-2, PD-L1, B7-DC, B7-H2, and B7-H5 exhibited similar expression patterns, but B7-H3, B7-H4, B7-H6, and B7-H7 showed outlier expression patterns compared with other B7 molecules. Besides, B7 molecules were genetically stable and exhibited low alteration frequency. IHC staining indicated PD-L1, B7-H3, and B7-H4 were up-regulated in PaCa tissues and showed uncorrelated expression patterns. Furthermore, high expression of PD-L1 and B7-H3 indicated poor-differentiated grades in PaCa. PD-L1 was positively, but B7-H4 was negatively correlated with CD8+ TILs infiltration in PaCa. Moreover, combined PD-L1 and B7-H4 expression was a novel subtyping strategy in PaCa, namely patients with both high PD-L1 and B7-H4 expression exhibited decreased CD8+ TILs infiltration in tumor tissues. CONCLUSION: Overall, we systemically analyzed the expression patterns of B7 molecules and proposed a novel subtyping strategy in PaCa. Patients with both high PD-L1 and B7-H4 expression exhibited the immuno-cold phenotype, which may be not suitable for immunotherapy.


Subject(s)
B7-H1 Antigen , Pancreatic Neoplasms , B7 Antigens/genetics , B7 Antigens/metabolism , B7-H1 Antigen/genetics , B7-H1 Antigen/metabolism , Biomarkers, Tumor/genetics , China , Humans , Pancreatic Neoplasms/genetics , Toll-Like Receptor 1 , Pancreatic Neoplasms
17.
Chemphyschem ; 23(9): e202200060, 2022 May 04.
Article in English | MEDLINE | ID: mdl-35294798

ABSTRACT

A neutral boron carbonyl complex B4 (CO)3 is generated in the gas phase and is characterized by infrared plus vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy and quantum chemical calculations. The complex is identified to have a planar C2v structure with three CO ligands terminally coordinated to a rhombus B4 core. It has a closed-shell singlet ground state that correlates to an excited state of B4 . Bonding analyses on B4 (CO)3 as well as the previously reported B4 and B4 (CO)2 indicate that the electronic structure of rhombus tetraboron cluster changes from a close-shell singlet to an open-shell singlet in B4 (CO)2 and to a close-shell singlet in B4 (CO)3 , demonstrating that the electronic structures of boron clusters can be effectively tuned via sequential CO ligand coordination.

18.
Phys Chem Chem Phys ; 24(5): 3207-3215, 2022 Feb 02.
Article in English | MEDLINE | ID: mdl-35044393

ABSTRACT

During the past few years, there has been a flurry of investigations on the lattice thermal transport of three-dimensional (3D) graphene, however, few studies have detailed how to adjust this property effectively using the presently available engineering technologies. In this work, the thermal transport properties of a porous single layer carbon honeycomb (SL-dCHC-2) and its mechanical response are systematically studied. We show that the thermal conductivity of SL-dCHC-2 can be adjusted effectively by varying the tensile strain, and its value is enhanced by up to 11.3 times with 8% strain as compared to the unstrained case. This value is significantly larger than what was observed for other two-dimensional (2D) materials such as silicene (∼7 times larger). This outstanding behavior is explained by the phonon mode level, indicating that a profound increase of the thermal conductivity under tensile strain is attributed to the enhancement of the phonon lifetime. In addition, the trend for the root mean squared displacement, which is closely related to the phonon anharmonic effect, correlates with the non-monotonic response of the dimerized C-C bonds at the linkage of the structure. These investigations and obtained results provide important guidance to develop 3D carbon honeycombs for several different purposes, such as for use as molecular sieves and in water purification applications.

19.
Phys Chem Chem Phys ; 24(27): 16484-16492, 2022 Jul 13.
Article in English | MEDLINE | ID: mdl-35771196

ABSTRACT

A vacuum ultraviolet free electron laser (VUV-FEL) photoionization aerosol mass spectrometer (AMS) has been developed for online measurement of neutral compounds in laboratory environments. The aerosol apparatus is mainly composed of a smog chamber and a reflectron time-of-flight mass spectrometer (TOF-MS). The indoor smog chamber had a 2 m3 fluorinated ethylene propylene film reactor placed in a temperature- and humidity-controlled room, which was used to generate the aerosols. The aerosols were sampled via an inlet system consisting of a 100 µm orifice nozzle and aerodynamic lenses. The application of this VUV-FEL AMS to the α-pinene ozonolysis under different concentrations reveals two new compounds, for which the formation mechanisms are proposed. The present findings contribute to the mechanistic understanding of the α-pinene ozonolysis in the neighborhood of emission origins of α-pinene. The VUV-FEL AMS method has the potential for chemical analysis of neutral aerosol species during the new particle formation processes.

20.
J Chem Phys ; 156(5): 054302, 2022 Feb 07.
Article in English | MEDLINE | ID: mdl-35135268

ABSTRACT

The vacuum ultraviolet (VUV) photodissociation of CO2 is important to understand the primary photochemical processes of CO2 induced by solar VUV excitation in the Earth's atmosphere. Here, we report a detailed study of vibrational-state-specific photodissociation dynamics of the CO(X1Σ+) + O(1D2) channel via the 3P1Πu state by using the time-sliced velocity-mapped ion imaging apparatus combined with the single VUV photoionization detection scheme. By recording the sliced images of the O(1D2) photoproducts formed by VUV photoexcitation of CO2 to the individual vibrational structure of the 3P1Πu state, both the vibrational state distributions of the counterpart CO(X1Σ+) photoproducts and the vibrational-state-specific product anisotropy parameters (ß) are determined. The experimental results show that photodissociation of CO2 at 108.22, 107.50, 106.10, and 104.76 nm yields less anisotropic (ß > 0) and inverted distributed CO(X1Σ+, v) photoproducts. The possible dissociation mechanism for the CO(X1Σ+) + O(1D2) channel may involve the non-adiabatic transition of excited CO2* from the initially prepared state to the 31A' state with potential energy barriers. While at 108.82 and 107.35 nm, the vibrational distributions are found to have the population peaked at a low vibrational state, and the anisotropy parameters turn out to be negative. Such variation indicates the possibility of another non-adiabatic dissociation pathway that may involve Coriolis-type coupling to the low-lying dissociative state. These observations show sclear evidence of the influence of the initially vibrational excitations on the photodissociation dynamics of CO2 via the 3P1Πu state.

SELECTION OF CITATIONS
SEARCH DETAIL