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The Transitional Transmittance Response of ZIF-8 Gas Adsorption Observed Using Terahertz Waves
摘要： In this study, we recorded the transitional response in terms of terahertz transmittance of zeolitic imidazole framework-8 [Zn(2-methylimidazolate)2, ZIF-8] at 2.0 THz as a function of exposure time to gaseous propane and n-butane. The transmittance at 2.0 THz increased as gas adsorbed onto the ZIF-8. Conversely, during a nitrogen purge, transmittance decreased as the alkane gas desorbed. We estimated time constants for the adsorption and desorption of the two gases by comparing the plots of their responses. We also demonstrated the potential of using a combination of ZIF materials and terahertz technology as a novel gas analyzer.
关键词： Adsorption kinetics,Terahertz vibration,Metal-organic frameworks,Porous solids,Infrared absorption spectroscopy
更新于2025-09-23 15:22:29
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Optical aptasensor based on silver nanoparticles for the colorimetric detection of adenosine
摘要： A new and straightforward optical sensor for the colorimetric determination of adenosine (AD) in human urine samples was developed. The sensor comprised silver nanoparticles (AgNPs) as colorimetric elements and anti-AD aptamer (AP) as a recognition probe. In a solution containing AD and high concentration of NaCl, due to the unique binding of AD with AP, the aggregated metal nanomaterials dispersed in the solution, and the color intensity of the solution was changed accordingly. The absorbance of the solution was monitored for AD quantification. The method was applicable for the determination of AD in the concentration range of 60–280 nM with the detection limit of 21 nM. The relative standard deviation ranged from 4.8 to 8.8% for six replicates. The method showed excellent selectivity toward AD checked over some probable interfering compounds. To investigate the performance of AgNPs, the analytical characteristics of the method including linear range, detection limit, selectivity, and precision were compared with those obtained by a common AuNPs-based aptasensor. The reliability of the method was further ascertained for the detection of AD in urine samples of two lung cancer patients with percentage recoveries in the range of 98–107%.
关键词： Adenosine,Silver nanomaterials,Colorimetric,UV–vis absorption spectroscopy,Aptamer
更新于2025-09-23 15:22:29
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Charge-state analysis of small barium-oxide clusters by X-ray absorption spectroscopy
摘要： Small barium-oxide clusters BamOn+ are studied by mass spectrometry and X-ray absorption spectroscopy to discuss stability of the clusters and oxidation state of constituent atoms. It is found that clusters with bulk composition, n = m, are stable, which can accommodate one or two excess oxygen atoms additionally as manifested by n = m + 1 and m + 2 species in the mass spectrum. XAS spectra of Ba2O2+ and Ba2O3+ reveal that the oxidation state of barium atoms stays at +2 (the bulk BaO value) even after binding excess oxygen, whereas spectral features originating from oxygen exhibit composition dependence. The present finding suggests that stoichiometric small barium-oxide clusters bind less-negatively-charged oxygen atoms without change in the charge state of barium.
关键词： X-ray absorption spectroscopy,charge state,barium-oxide clusters,oxidation number
更新于2025-09-23 15:22:29
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In situ high-pressure spectroscopic studies using moissanite (4H-SiC) anvils
摘要： We examined the Raman scattering and IR absorption spectroscopy of 4H-SiC and its performance as an anvil material for high-pressure UV-visible absorption spectroscopic measurements. The first- and second-order Raman peaks of 4H-SiC and diamond do not coincide. 4H-SiC does not have obvious signals from 2330-5000 cm-1, suggesting that 4H-SiC anvils are beneficial for high-pressure studies of samples whose Raman signals locate in the region of diamond. Above 1800 cm-1, the transmitted signal of 4H-SiC in the IR absorption spectra, measured through 4.6 mm thickness is much higher than that of type IIa diamond. An in situ high-pressure UV-visible absorption spectroscopy study on CdI2 was carried out up to 28.0 GPa using 4H-SiC anvil cells (4H-SAC) with a 400 μm culet and the acquired band gap narrowed with increasing pressure. These results show that 4H-SiC has an excellent performance in high-pressure spectroscopic studies.
关键词： IR absorption spectroscopy,high-pressure,UV-visible absorption spectroscopy,Raman spectroscopy,4H-SiC
更新于2025-09-23 15:21:21
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Pseudo-Continuous Flow FTIR System for Glucose, Fructose and Sucrose Identification in Mid-IR Range
摘要： In this paper, we present a new FTIR-based micro?uidic system for Glucose, Fructose and Sucrose detection. The proposed micro?uidic system is based on a pseudo-continuous ?ow coupled to a microscope-FTIR instrument. The detection and characterization of sugar samples were performed by recording their absorption spectrum in the wavelength range 700–1000 cm?1 of the Mid-IR region. The proposed pseudo-continuous ?ow system is designed to improve the uniformity of the sample distribution in the analyzed area versus conventional systems. The obtained results for different sugars concentrations, show a very low measurement error of 4.35% in the absorption peak intensity, which is ten times lower than the error obtained using the conventional measurements.
关键词： mid-IR absorption spectroscopy,absorption spectrum,FTIR spectroscopy,microscopy-FTIR spectrometer,sugars detection and quanti?cation,Glucose,Fructose,Sucrose,pseudo-continuous ?ow
更新于2025-09-23 15:21:21
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Ultrafast X-ray Transient Absorption Spectroscopy of Gas-Phase Photochemical Reactions: A New Universal Probe of Photoinduced Molecular Dynamics
摘要： Time-resolved spectroscopic investigations of light-induced chemical reactions with universal detection capitalize recently on single-photon molecular probing using laser pulses in the extreme ultraviolet or X-ray regimes. Direct and simultaneous mappings of the time-evolving populations of ground-state reactants, Franck?Condon (FC) and transition state regions, excited-state intermediates and conical intersections (CI), and photoproducts in photochemical reactions utilize probe pulses that are broadband and energy-tunable. The limits on temporal resolution are set by the transit- or dwell-time of the photoexcited molecules at specific locations on the potential energy surface, typically ranging from a few femtoseconds to several hundred picoseconds. Femtosecond high-harmonic generation (HHG) meets the stringent demands for a universal spectroscopic probe of large regions of the intramolecular phase-space in unimolecular photochemical reactions. Extreme-ultraviolet and soft X-ray pulses generated in this manner with few-femtosecond or sub-femtosecond durations have enormous bandwidths, allowing the probing of many elements simultaneously through excitation or ionization of core?electrons, creating molecular movies that shed light on entire photochemical pathways. At free electron lasers (FELs), powerful investigations are also possible, recognizing their higher flux and tunability but more limited bandwidths. Femtosecond time-resolved X-ray transient absorption spectroscopy, in particular, is a valuable universal probe of reaction pathways that maps changes via the fingerprint core-to-valence resonances. The particular power of this method over valence-ionization probes lies in its unmatched element and chemical-site specificities. The elements carbon, nitrogen, and oxygen constitute the fundamental building blocks of life; photochemical reactions involving these elements are ubiquitous, diverse, and manifold. However, table-top HHG sources in the “water-window” region (280?550 eV), which encompasses the 1s-absorption edges of carbon (284 eV), nitrogen (410 eV), and oxygen (543 eV), are far from abundant or trivial. Recent breakthroughs in the laboratory have embraced this region by using long driving-wavelength optical parametric amplifiers coupled with differentially pumped high-pressure gas source cells. This has opened avenues to study a host of photochemical reactions in organic molecules using femtosecond time-resolved transient absorption at the carbon K-edge. In this Account, we summarize recent efforts to deploy a table-top carbon K-edge source to obtain crucial chemical insights into ultrafast, ultraviolet-induced chemical reactions involving ring-opening, nonadiabatic excited-state relaxation, bond dissociation and radical formation. The X-ray probe provides a direct spectroscopic viewport into the electronic characters and configurations of the valence electronic states through spectroscopic core-level transitions into the frontier molecular orbitals of the photoexcited molecules, laying fertile ground for the real-time mapping of the evolving valence electronic structure. The profound detail and mechanistic insights emerging from the pioneering experiments at the carbon K-edge are outlined here. Comparisons of the experimental methodology with other techniques employed to study similar reactions are drawn, where applicable and relevant. We show that femtosecond time-resolved X-ray transient absorption spectroscopy blazes a new trail in the study of nonadiabatic molecular dynamics. Despite table-top implementations being largely in their infancy, future chemical applications of the technique will set the stage for widely applicable, universal probes of photoinduced molecular dynamics with unprecedented temporal resolution.
关键词： time-resolved spectroscopy,photochemical reactions,high-harmonic generation,X-ray transient absorption spectroscopy,nonadiabatic molecular dynamics
更新于2025-09-23 15:21:21
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Soft X-ray Absorption Spectroscopy Study of Spin Crossover Fe-Compounds: Persistent High Spin Configurations under Soft X-ray Irradiation
摘要： Metal-organic complex exhibiting spin crossover (SCO) behavior has drawn attention for its functionality as a nanoscale spin switch. The spin states in the metal ions can be tuned by external stimuli such as temperature or light. This article demonstrates a soft X-ray–induced excited spin state trapping (SOXEISST) effect in Hofmann-like SCO coordination polymers of FeII(4-methylpyrimidine)2[Au(CN)2]2 and FeII(pyridine)2[Ni(CN)4]. A soft X-ray absorption spectroscopy (XAS) study on these polymers showed that the high spin configuration (HS; S = 2) was prevalent in Fe2+ ions during the measurement even at temperatures much lower than the critical temperatures (>170 K), manifesting HS trapping due to the X-ray irradiation. This is in strong contrast to the normal SCO behavior observed in FeII(1,10-phenanthroline)2(NCS)2, implying that the structure of the ligand chains in the polymers with relatively loose Fe-N coordination might allow a structural adaptation to stabilize the metastable HS state under the soft X-ray irradiation.
关键词： soft X-ray induced excited spin state trapping,X-ray absorption spectroscopy,high spin,spin crossover
更新于2025-09-23 15:21:21
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Sensitive dual sensing system for oxygen and pressure based on deep ultraviolet absorption spectroscopy
摘要： In this study, a highly sensitive monitoring system for dual sensing of oxygen and pressure has been developed. The absorption of oxygen in the wavelength range of 186–196 nm was observed and the corresponding absorption cross-section of oxygen in this band was achieved. An approach based on differential optical absorption spectroscopy was used to describe the concentration of oxygen. The detection limit of oxygen was determined to be 150 ppm per meter. No relation between pressure and oxygen absorption line shape in the related wavelength band was confirmed. Based on the absorption of oxygen, pressure detection was realized and a detection limit of 180 Pa was obtained. A dual sensing system for oxygen and pressure was constructed.
关键词： Pressure,Oxygen,Absorption spectroscopy,Ultraviolet,Dual sensing
更新于2025-09-23 15:21:21
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Frequency shift of an optical frequency standard as a function of probe modulation of the radiation frequency, pressure, and gas temperature in an absorbing cell
摘要： Frequency shifts of an optical Nd : YAG/I2-standard are measured in a pressure range of molecular iodine 5 – 22 mTorr and deviation of probe modulation frequency 480 kHz – 4 MHz for the hyperfine structure component a1 of the molecular iodine absorption line R(56) 32 – 0. The frequency shift of the optical standard is estimated under varied temperatures of a cell and cell finger, which determines the pressure of the molecular iodine vapour. The requirements are defined to temperature stability of the cell and its finger for obtaining high long-term frequency stability of the optical frequency standard.
关键词： molecular iodine,optical frequency standards,saturation absorption spectroscopy,acousto-optical modulator,lasers,luminescence
更新于2025-09-23 15:21:21
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Fluorinating ??a??Extended Molecular Acceptors Yields Highly Connected Crystal Structures and Low Reorganization Energies for Efficient Solar Cells
摘要： The synthesis and characterization of new semiconducting materials is essential for developing high-efficiency organic solar cells. Here, the synthesis, physiochemical properties, thin film morphology, and photovoltaic response of ITN-F4 and ITzN-F4, the first indacenodithienothiophene nonfullerene acceptors that combine π-extension and fluorination, are reported. The neat acceptors and bulk-heterojunction blend films with fluorinated donor polymer poly{[4,8-bis[5-(2-ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]-dithiophene-2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF, also known as PM6) are investigated using a battery of techniques, including single crystal X-ray diffraction, fs transient absorption spectroscopy (fsTA), photovoltaic response, space-charge-limited current transport, impedance spectroscopy, grazing incidence wide angle X-ray scattering, and density functional theory level computation. ITN-F4 and ITzN-F4 are found to provide power conversion efficiencies greater and internal reorganization energies less than their non-π-extended and non-fluorinated counterparts when paired with PBDB-TF. Additionally, ITN-F4 and ITzN-F4 exhibit favorable bulk-heterojunction relevant single crystal packing architectures. fsTA reveals that both ITN-F4 and ITzN-F4 undergo ultrafast hole transfer (<300 fs) in films with PBDB-TF, despite excimer state formation in both the neat and blend films. Taken together and in comparison to related structures, these results demonstrate that combined fluorination and π-extension synergistically promote crystallographic π-face-to-face packing, increase crystallinity, reduce internal reorganization energies, increase interplanar π–π electronic coupling, and increase power conversion efficiency.
关键词： impedance spectroscopy,organic solar cells,crystal structures,femtosecond transient absorption spectroscopy,computational chemistry
更新于2025-09-23 15:21:01