- 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
-
Preparation of graphene oxide with large lateral size and graphene/polyimide hybrid film via in situ “molecular welding” strategy
摘要： In this letter, we report an "ultrasonication-free" direct exfoliation method to obtain graphene oxide with large lateral size (LGO). The average size of LGO sheets is about 50 lm * 50 lm. The g-LGO film shows a superior in-plane thermal conductivity after the graphitization treatment. Furthermore, the in situ "molecular welding", using polyimide (PI) to weld up the GO sheets, is conducted to improve the performance of hybrid thermal conducting film. The thermal conductivity of g-LGO/PI film is 1053.975 ± 8.762 W m-1 K-1, superior to that of the g-LGO film and g-SGO/PI. The direct preparation method to obtain GO with large lateral size, followed by such an in situ "molecular welding" strategy by PI, provides a promising way to fabricate graphene-based film for efficient thermal management.
关键词： Molecular welding,In situ polymerization,Large lateral size,Thermal properties,Carbon material
更新于2025-09-23 15:23:52
-
Surface Plasmon Resonance Based Highly Selective Fiber Optic Dopamine Sensor Fabricated Using Molecular Imprinted GNP/SnO <sub/>2</sub> Nanocomposite
摘要： Fabrication and characterization of a highly selective fiber optic surface plasmon resonance-based dopamine sensor using molecular imprinted graphene nanoplatelets/tin oxide (SnO2) nanocomposite have been reported. The synthesis of sensing layer has been carried out using a series of optimizations and morphological studies. The effectiveness of the sensing layer over other possible probe designs has been proved by performing control experiments for a dopamine concentration range covering the suggested level of dopamine for human being. The limit of detection (LOD) of the sensor evaluated is 0.031 μM, which is lower than the LOD values of various dopamine sensors fabricated using different methods. The specificity of the sensor for dopamine has been confirmed by performing experiments using various interferands while the stability and reusability of the sensor probe have been checked by performing experiments repeatedly for a long period of time. Apart from high sensitivity, low LOD, and fast response, the sensor can be used for remote sensing and online monitoring of dopamine.
关键词： surface plasmon resonance,SnO2 nanoparticles,optical fiber sensor,GNP/SnO2 nanocomposite,graphene,Dopamine,molecular imprinting
更新于2025-09-23 15:23:52
-
Bright red-emitting highly reliable styryl probe with large stokes shift for visualizing mitochondria in live cells under wash-free conditions
摘要： Bright red-emitting pyridinium cyanine based styryl probe 2 is synthesized in good yields. Probe 2 demonstrated a large Stokes’ shift (Δλ ≈ 128 nm, 4227 cm-1 in DCM) and excellent fluorescent quantum yield (?fl ≈ 0.2 - 0.7) due to strong Intra-molecular charge transfer (ICT). Probe 2 found to exhibit exceptional selectivity for cellular mitochondria in both normal (COS-7) and cancer (A549) cell lines. Probe 2 is readily applicable as a “wash-free” dye to visualize mitochondria as it does not require post-staining washing prior to imaging. Styryl probe 2 also showed an excellent biocompatibility as the calculated LC50 (lethal concentration, 50%) value was > 20 μM. Probe 2 emission did not show any interferences from anionic species or other biological molecules. Probe 2 is readily excitable (λex ~460 and λem ~618 nm) with the available laser (454 nm) in commercial microscopes and thus it can be a useful probe for mitochondrial tracking in live cells.
关键词： Wash-free application,Biocompatibility,Intra-molecular charge transfer (ICT),Styryl dye,Large Stokes shift,Mitochondria selectivity
更新于2025-09-23 15:23:52
-
A promising family of fluorescent water-soluble aza-BODIPY dyes for in vivo molecular imaging
摘要： A new family of water-soluble and bioconjugatable aza-BODIPY fluorophores was designed and synthesized using a boron-functionalization strategy. These dissymmetric bis-ammonium aza-BODIPY dyes present optimal properties for a fluorescent probe, i.e. they are highly water-soluble, very stable in physiological medium, they do not aggregate in PBS, possess high quantum yield and finally they can be easily bioconjugated to antibodies. Preliminary in vitro and in vivo studies were performed for one of these fluorophores to image PD-L1 (Programmed Death-Ligand 1), highlighting the high potential of these new probes for future in vivo optical imaging studies.
关键词： molecular Imaging,Fluorescent probes,boron functionalization,aza-BODIPY,Water-soluble fluorophores
更新于2025-09-23 15:23:52
-
A Cationic Rectifier Based on a Graphene Oxide Covered Microhole: Theory and Experiment
摘要： Cation transport through nano-channels in graphene oxide can be rectified to give ionic diode devices for future applications for example in desalination. A film of graphene oxide is applied to a 6 μm thick poly-ethylene-terephthalate (PET) substrate with 20 μm diameter microhole and immersed in aqueous HCl solution. Strong diode effects are observed even at high ionic strength (0.5 M). Switching between open and closed states, microhole size effects, and time dependent phenomena are explained based on a simplified theoretical model focusing on the field-driven transport within the microhole region. In aqueous NaCl, competition between Na+ transport and field-driven heterolytic water splitting are observed, but shown to be significant only at low ionic strength. Therefore, nanostructured graphene oxide is demonstrated to exhibit close to ideal behavior for future application in ionic diode desalination of seawater.
关键词： molecular pump,amplifier,voltammetry,transistor,desalination,iontronics
更新于2025-09-23 15:23:52
-
High-Performance Chromatographic Characterization of Surface Chemical Heterogeneities of Fluorescent Organic–Inorganic Hybrid Core–Shell Silica Nanoparticles
摘要： In contrast to small-molar-mass compounds, detailed structural investigations of inorganic core–organic ligand shell hybrid nanoparticles remain challenging. The assessment of batch-reaction-induced heterogeneities of surface chemical properties and their correlation with particle size has been a particularly long-standing issue. Applying a combination of high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC) to ultra-small (<10 nm diameter) poly(ethylene glycol)-coated (PEGylated) fluorescent core–shell silica nanoparticles, we elucidate here previously unknown surface heterogeneities resulting from varying dye conjugation to nanoparticle silica cores and surfaces. Heterogeneities are predominantly governed by dye charge, as corroborated by molecular dynamics simulations. We demonstrate that this insight enables the development of synthesis protocols to achieve PEGylated and targeting ligand-functionalized PEGylated silica nanoparticles with dramatically improved surface chemical homogeneity, as evidenced by single-peak HPLC chromatograms. Because surface chemical properties are key to all nanoparticle interactions, we expect these methods and fundamental insights to become relevant to a number of systems for applications, including bioimaging and nanomedicine.
关键词： surface chemistry heterogeneity,high-performance liquid chromatography,nanoparticle characterization,nanoparticle surface functionalization,fluorescence correlation spectroscopy,molecular dynamics,nanoparticle heterogeneity
更新于2025-09-23 15:23:52
-
Ultrafast data mining of molecular assemblies in multiplexed high-density super-resolution images
摘要： Multicolor single-molecule localization super-resolution microscopy has enabled visualization of ultrafine spatial organizations of molecular assemblies within cells. Despite many efforts, current approaches for distinguishing and quantifying such organizations remain limited, especially when these are contained within densely distributed super-resolution data. In theory, higher-order correlation such as the Triple-Correlation function is capable of obtaining the spatial configuration of individual molecular assemblies masked within seemingly discorded dense distributions. However, due to their enormous computational cost such analyses are impractical, even for high-end computers. Here, we developed a fast algorithm for Triple-Correlation analyses of high-content multiplexed super-resolution data. This algorithm computes the probability density of all geometric configurations formed by every triple-wise single-molecule localization from three different channels, circumventing impractical 4D Fourier Transforms of the entire megapixel image. This algorithm achieves 102-folds enhancement in computational speed, allowing for high-throughput Triple-Correlation analyses and robust quantification of molecular complexes in multiplexed super-resolution microscopy.
关键词： molecular assemblies,computational algorithm,multiplexed high-density super-resolution images,Triple-Correlation function,Ultrafast data mining
更新于2025-09-23 15:23:52
-
Role of carbon-rings in polycrystalline GeSb2Te4 phase-change material
摘要： Carbon (C) is used to increase the overall performance of Ge-Sb-Te (GST) phase-change memory material. Yet the C configuration in polycrystalline GST and its microscopic role is unclear. Using the well-studied GeSb2Te4 as an example, this work unravels the microscopic C doping role based on ab initio calculations. Our results reveal that carbon prefers occupying the interstitials at very low C concentrations, while with a roughly critical C concentration of over 2%, carbon atoms will cluster at the grain boundaries, with very few carbon atoms might exist at the interstitials. With further increasing the C concentrations, C atoms tend to form ring-like configurations in the grain boundaries rather than chain-like configurations. This is due to that the covalent bonds in ring-like configurations are stronger than that in chain-like configurations. Further analysis on the lone-pair electrons and electronic densities of states show that C dopants significantly change the number of lone-pair electrons of surrounding atoms, thus affecting the electronic structure. Finally, the diffusion coefficient of C is estimated to be of the order of 10^-13 m^2/s at 400 K, indicating the good stability of C dopants in GeSb2Te4. Our work provides fundamental understanding on the microscopic role of C doping in GST phase-change materials and benefits for improving the properties of the recording materials by controlling the doping concentration.
关键词： Ab initio molecular dynamic simulations,Ab initio calculations,Phase-change materials,Grain boundary,GeSb2Te4,Carbon doping
更新于2025-09-23 15:23:52
-
The efficient photodesorption of nitric oxide (NO) ices
摘要： The study and quantification of UV photon-induced desorption of frozen molecules furthers our understanding of the chemical evolution of cold interstellar regions. Nitric oxide (NO) is an important intermediate species in both gas-phase and solid-phase chemical networks. In this work, we present quantitative measurements of the photodesorption of a pure NO ice. We used the tunable monochromatic synchrotron light of the DESIRS beamline of the SOLEIL facility near Paris to irradiate NO ices in the 6–13.6 eV range and measured desorption by quadrupole mass spectrometry. We find that NO photodesorption is very efficient, its yield being around 10?2 molecule per incident photon for UV fields relevant to the diffuse and dense interstellar medium. We discuss the extrapolation of our results to an astrophysical context and we compare photodesorption of NO to previously studied molecules.
关键词： methods: laboratory: solid state,ISM: abundances,ultraviolet: ISM,astrochemistry,ISM: molecules,molecular processes
更新于2025-09-23 15:23:52