- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Molecular-beam resonance method with Zeeman-decelerated samples: Application to metastable helium molecules
摘要： We use a multistage Zeeman decelerator to generate slow beams (v ≈ 100 m/s) of translationally cold, spin-polarized metastable a 3Σ+u He2 molecules and perform a precision measurement of their spin-rotation fine structure. The spin polarization results from the elimination of the high-field-seeking J = N spin-rotational component of each rotational level (rotational quantum number N) by the Zeeman deceleration process. By repopulating the J = N component from the J = N ± 1 low-field-seeking components using radio-frequency radiation, we measured the spin-rotation fine structure of 13 rovibrational levels with v = 0, 1 and N = 1–21. The low beam velocity and the resulting long interaction times with the radio-frequency radiation were exploited to determine the transition frequencies with a precision of 300 Hz.
关键词： metastable helium molecules,precision spectroscopy,molecular-beam resonance,Zeeman deceleration,spin-rotation fine structure
更新于2025-09-23 15:23:52
-
A novel on-line electrochemical transmission infrared spectroscopy to?study the current efficiency of carbonates for?ethanol oxidation reactions in alkaline media
摘要： Research on the reaction mechanism of ethanol oxidation reaction (EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis of the non-volatile products. Conventional on-line electrochemical flowing transmission infrared spectroscopy (ETIRS) can only collect a part of the carbonate products of EOR in alkaline media, making the further quantitative study impossible. Herein, a new ETIRS system has been designed and prepared by employing a cation-exchange membrane (Nafion) in the sampling hood. The using of the Nafion membrane can prevent the anions crossing over by confining the generated carbonates in the sampling hood without diffusing into the bulk electrolyte. Therefore, the collection efficiency of the carbonate products as well as the test accuracy of the carbonate current efficiency has been significantly improved. The result of CO stripping reaction shows that ca. 100% of the carbonate product is able to be collected in alkaline media by this new system. The influence of the experimental temperature to the carbonate current efficiency has been further studied on Pt/C toward EOR in alkaline media.
关键词： Transmission infrared spectroscopy,Ethanol oxidation reaction,Platinum,Alkaline media
更新于2025-09-23 15:23:52
-
Electron transfer from photoexcited naphthalene-1,4:5,8-bis(dicarboximide) radical anion to Mn(bpy)(CO)3X and Re(bpy)(CO)3X CO2 reduction catalysts linked via a saturated methylene bridge
摘要： Supramolecular systems that connect a naphthalene-1,4:5,8-bis(dicarboximide) (NDI) radical anion donor to Mn(bpy)(CO)3Br or Re(bpy)(CO)3Cl CO2 reduction catalysts via a methylene bridge have been synthesized and studied by femtosecond transient visible, near-infrared and mid-infrared spectroscopy. The use of the methylene bridge to link NDI to the complexes does not affect the reduction potentials of the metal complexes. Selective photoexcitation of NDI?? to 2*NDI?? results in ultrafast reduction of the bipyridine (bpy) ligands on both the Mn and Re complexes to form Mn(I)(bpy??)(CO)3X and Re(I)(bpy??)(CO)3X in near unity quantum yield, respectively. The initial formation of Mn(I)(bpy??)(CO)3X is unexpected based on previous electrochemical data that indicates the Mn(I) center is reduced at a more positive potential than the bpy ligand. Moreover, the rate of forward electron transfer in the Mn complex was found to be faster than in the Re complex, while the rate of the back electron transfer in the Re complex was faster than in the Mn complex.
关键词： Electrochemistry,CO2 reduction,Electron transfer,Radical anions,Femtosecond spectroscopy,Solar energy
更新于2025-09-23 15:23:52
-
Role of solvent H-bonding and polarity on photophysical properties of a benzothiazole-based ratiometric amyloid fibril sensor
摘要： Detailed photophysical properties of 2-[2′-Me,4′-(dimethylamino)-phenyl]benzothiazole (2Me-DABT), a potential ratiometric amyloid fibril sensor, have been investigated in different solvents and solvent mixtures using steady state and time-resolved spectroscopic techniques. Our studies show that emission properties of 2Me-DABT are significantly modulated by polarity of solvent media. Extent of solvatochromism (3585 cm?1) shown by 2Me-DABT is quite large and can be used to monitor micropolarity of different complex media. Further, Stokes’ shift (> 10,000 cm?1) shown by 2Me-DABT in all studied solvents is also much larger than most common molecular probes. It has also been shown that hydrogen bonding with solvent molecules results in large modulation in photophysical properties of 2Me-DABT. The H-bonding with water molecules induces a large change (39°) in the dihedral angle between benzothiazole and aniline moieties resulting large changes in photophysical properties of 2Me-DABT in polar protic solvents. Photophysical properties reported herein are used to explain observed amyloid sensing behaviour of 2Me-DABT. Detailed quantum chemical calculations are performed to support the experimental results.
关键词： Amyloid sensor,H-bonding,Photophysics,Time-resolved spectroscopy,Fluorescence
更新于2025-09-23 15:23:52
-
[IEEE 2018 IEEE Biomedical Circuits and Systems Conference (BioCAS) - Cleveland, OH, USA (2018.10.17-2018.10.19)] 2018 IEEE Biomedical Circuits and Systems Conference (BioCAS) - Monitoring Red Blood Cell Aggregation Dynamics in Stasis and Under Flow Using a Microfluidic Dielectric Sensor
摘要： This paper reports on monitoring the red blood cell (RBC) aggregation dynamics under flow and in static condition using a microfluidic dielectric sensor. The sensor employs a three-dimensional (3D), parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel with a height of 50μm. Using an impedance analyzer, the sensor is shown to measure the real part of complex relative dielectric permittivity of human whole blood in a frequency range of 10kHz–100MHz under flow and in static condition. The dielectric permittivity of human whole blood at 1MHz indicates the formation of RBC aggregate structures called rouleaux under static condition and their complete breakdown under a physiological shear flow rate of 500s-1. This work also demonstrates that the kinetics of RBC aggregation is dependent on fibrinogen concentration of the blood sample and establishes that the sensor is capable of distinguishing this difference in the aggregation process even under physiological shear flow rates. This work demonstrates the potential of dielectric spectroscopy in obtaining information on RBC aggregation dynamics using μL-volumes of whole blood under flow and in stasis.
关键词： red blood cells,capacitive sensor,dielectric spectroscopy,Aggregation,rouleaux formation,microfluidics
更新于2025-09-23 15:23:52
-
Investigation of ultrafast energy transfer mechanism in BODIPY–Porphyrin dyad system
摘要： Novel β-fused BODIPY-Porphyrin compounds that contain free base porphyrin (TPP2BDP) and its Ni(II) complex (NiTPP2BDP) were synthesized to investigate intramolecular energy transfer mechanisms of β-fused BODIPY-porphyrin dyads and effect of the unfilled d shell metal ion on energy transfer mechanism. Fluorescence spectra of compounds exhibited that BODIPY emission was diminished upon excitation of the BODIPY unit because of the energy transfer from BODIPY to porphyrin unit. Femtosecond pump-probe spectroscopy measurements revealed that energy transfer of investigated compounds are faster than previous studies in literature. Rapid energy transfer (about 500 fs) from BODIPY to porphyrin was observed for both compounds when BODIPY unit is excited due to direct linkage of BODIPY to porphyrin unit. Intersystem crossing mechanism was also observed for the compound that contains free base porphyrin (TPP2BDP), whereas d-d transition was observed for the compound that contains metalloporphyrin (NiTPP2BDP) due to unfilled d orbital of Ni(II) ion.
关键词： Fast energy transfer,Borondipyrromethene,Porphyrin,Ultrafast pump-probe spectroscopy
更新于2025-09-23 15:23:52
-
Realization of a infrared detector free of bandwidth limit based on quartz crystal tuning fork
摘要： A new type of photoelectric detector based on a standard quartz crystal tuning fork (QCTF) with resonant frequency of ～32 kHz is developed for infrared spectroscopy applications. Analogous to the photoelectric effect of traditional semiconductor detectors, we utilize the piezoelectric effect of the QCTF to gauge the light intensity. To demonstrate this technique, the spectral absorption features of C2H2 molecule have been recorded and compared with a commercial mercury cadmium-telluride (MCT) detector. The proposed detection technique may pave a new way towards developing a new type of photodetector without bandwidth limit and complicated cryogenic cooling.
关键词： Infrared detector,Piezoelectric effect,QCTF,Laser spectroscopy
更新于2025-09-23 15:23:52
-
Tunable white-light emission from Pr3+/Dy3+ co-doped B2O3 - TeO2 PbO - ZnO Li2O - Na2O glasses
摘要： In this paper, structural and optical analysis of boro-tellurite based glasses co-doped with Dy3+ and Pr3+ ions has been carried out. The glasses were fabricated by traditional melt quenching technique. XRD results confirm the amorphous-like nature of the glasses. FTIR spectroscopy was applied to explore the functional groups and interactions for the samples. The transition temperatures of glasses were identified by TGA/DSC analysis. Optical absorption and emission spectra of all the glasses have been recorded in the UVe Vis- NIR spectral range. Tauc's method was applied to determine the direct and indirect optical band gaps. Luminescence spectra show intense emission bands at ～482 nm and ～574 nm wavelengths under λexc = 388 nm corresponding to Dy3+: 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions. Decay time data revealed the occurrence of a non-radiative energy transfer from Dy3+ to Pr3+ ions. Intense emission bands are identified at ～602 nm (orange), ～487 nm (blue) and ～574 nm (yellow) observed upon λexc = 437 nm, corresponding to Pr3+:1D2→3H4, Pr3+:3P0,1,2 → 3H4/Dy3+: 4F9/2 → 6H13/2 and Dy3+: 4F9/2 → 6H13/2 transitions, respectively, where the Dy3+ emissions are due to energy transfer from Pr3+ to Dy3+ ions. The CIE chromaticity results confirm that different colors can be generated by tuning the exciting wavelength, where all the glasses are capable to emit white light under λexc = 388 nm, while at λexc = 437 nm the samples (S2eS4) emit reddish orange light. Accordingly, it is plausible to suggest these glasses for white LED and SSL applications.
关键词： Optical absorption,Photoluminescence,W-LEDs,Raman spectroscopy,Borotellurite glass,Energy transfer
更新于2025-09-23 15:23:52
-
Inspecting human colon adenocarcinoma cell lines by using terahertz time-domain reflection spectroscopy
摘要： Techniques to inspect and analyze human colorectal cancer cell lines by using terahertz time-domain attenuated total reflection spectroscopy (THz TD-ATR) were investigated. The characteristics of THz absorption spectra of two colorectal cancer cell lines DLD-1 and HT-29 in aqueous solutions with different concentrations were studied. Different spectral features were observed compared to normal cell line. Identification results based on different parameters including absorption coefficient, refractive index, real and imaginary parts of complex permittivity, dielectric loss tangent were discussed. This research may be promising for quick and instant inspection of liquid samples by using THz time-domain spectroscopy in medical applications.
关键词： Absorption coefficient,Dielectric loss tangent,Terahertz time-domain attenuated total reflection spectroscopy,DLD-1 cell line,Cancer identification,HT-29 cell line
更新于2025-09-23 15:23:52
-
Precision mapping the topological bands of 2D spin-orbit coupling with microwave spin-injection spectroscopy
摘要： To investigate the band structure is one of the key approaches to study the fundamental properties of a novel material. We report here the precision band mapping of a 2-dimensional (2D) spin-orbit (SO) coupling in an optical lattice. By applying the microwave spin-injection spectroscopy, the band structure and spin-polarization distribution are achieved simultaneously. The band topology is also addressed with observing the band gap close and re-open at the Dirac points. Furthermore, the lattice depth and the Raman coupling strength are precisely calibrated with relative errors in the order of 10?3. Our approach could also be applied for exploring the exotic topological phases with even higher dimensional system.
关键词： Topological band,Microwave spin-injection spectroscopy,Spin polarization,Topological phase transition,2D spin-orbit coupling
更新于2025-09-23 15:23:52