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Microwave cavity perturbation of nitrogen doped nano-crystalline diamond films
摘要： Non-contact and non-destructive electrical conductivity measurements of nitrogen doped nano-crystalline diamond films have been demonstrated using a microwave cavity perturbation system. The conductivity of the films was controlled by simply varying the CH4 gas concentration during microwave plasma assisted chemical vapour deposition, thereby promoting the formation of sp2 carbon at the grain boundaries. The presence of sp2 carbon is verified through Raman spectroscopy, x-ray photoelectron spectroscopy and electron energy loss spectroscopy, while scanning electron microscopy confirms an increasing surface area for sp2 to form. The microwave cavity perturbation results show that the measured cavity quality factor varies with CH4 concentration. The extraction of conductivity is achieved through a depolarisation model, which must be considered when the sample is smaller than the cavity and through both electric and magnetic field perturbations. The microwave measurements are comparable to contacting and damaging measurements when the film conductivity is greater than the substrate, thus demonstrating an invaluable method for determining conductivity without the need for depositing any electrodes on the film.
关键词： non-contact,microwave dielectric spectroscopy,nano-crystalline diamond,electrical conductivity
更新于2025-09-04 15:30:14
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Time-resolved photoluminescence of pH-sensitive carbon dots
摘要： Time-resolved photoluminescence emission were performed to study the ? 100 ps time-scale photophysics of water soluble carbon dots (CDs) dispersed in different pH solutions. Excitation of the core and high-energy edge states at excitation wavelengths λex ￡ 350 nm produce hole-electron excitonic charge-carriers but do not yield any photoluminescence emission, implying efficient non-radiative recombination mechanisms for the charge-carriers. Using λex ~ 375 nm, surface fluorophores as well as low-lying edge-states are excited, producing emission over a broad range. However, the emission characteristics vary strongly depending on the pH condition and the choice of excitation wavelength. In particular, the edge state emission is abruptly extinguished at pH ≥ 5, which also marks the onset of deprotonation of surface-bound -COOH groups of the CDs, indicating that the -COO- anionic centers promote quenching of edge-state emission. Using λex ~ 450 nm, only the surface fluorophores are excited. The deprotonation of phenolic -OH group at pH>9 causes a sharp red-shift in the emission spectra at all excitation wavelengths. The pH-sensitive emission behavior of the CDs enable them to serve as optical pH sensors.
关键词： time-resolved spectroscopy,carbon dots,photoluminescence,pH-sensitive,optical pH sensors
更新于2025-09-04 15:30:14
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Review on multi gas detector using infrared spectral absorption technology
摘要： To provide some references for researchers engaged in infrared multi gas detection, this study introduced the infrared multi gas detection system thoroughly from infrared light source, infrared detector, optical multiplexing structure, and detection method. Currently, the coherent source represented by quantum cascade laser has replaced the traditional incoherent source like thermal radiant infrared light source and became the dominant light source in infrared multi gas detection. Accordingly, the infrared photodetector is widely used. The optical multiplexing structure based on the “multiplexing thought” is the core of infrared multi gas detection system. It mainly includes the single-source multiplex detection structure and multi-source multiplexing detection structure. Nondispersive infrared spectroscopy, long optical distance spectroscopy, wavelength/frequency modulation spectroscopy, cavity enhancement spectroscopy, and photoacoustic spectroscopy are major detection methods used in the infrared multi gas detection. This has important significance to many fields, such as industrial and agriculture production, environmental monitoring, life science, etc.
关键词： optical multiplexing structure,infrared spectroscopy,infrared detector,Multi gas detection,infrared light source
更新于2025-09-04 15:30:14
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Dataset of single Mycobacterium tuberculosis bacteria cells with different antibiotic susceptibility obtained by Raman spectroscopy
摘要： This data article contains Raman experimental data, obtained with Horiba Jobin-Yvon LabRam HR800 spectrometer (Japan), which can be used for rapid identification of Mycobacterium tuberculosis (MbT) bacteria (Beijing clade) in vitro. Data present analyzed Raman spectra of bacterial cells with various drug resistances obtained from pulmonary and extra pulmonary samples. Data can provide information about characteristic maxima of different structures in biological cell.
关键词： sensitive drug (SD) strains,multidrug resistance (MDR) strains,spectral data,Mycobacterium tuberculosis,Raman spectroscopy
更新于2025-09-04 15:30:14
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Echo Spectroscopy in Multilevel Quantum-Mechanical Rotors
摘要： We study the dynamics of rotational echoes in gas phase molecular ensembles and their dependence on the delay and intensity of the excitation pulses. We explore the unique dynamics of alignment echoes that arise from the multilevel nature of the molecular rotors and impose severe difficulties in utilizing echo responses for rotational spectroscopy. We show experimentally and theoretically that judicious control of both the delay and intensity of the second pulse enables multilevel “rotational echo spectroscopy.” The proposed methodology paves the way to rotational spectroscopy in high-density gas samples.
关键词： rotational echoes,echo spectroscopy,gas phase molecular ensembles,multilevel quantum-mechanical rotors
更新于2025-09-04 15:30:14
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Onset Classification in Hemodynamic Signals Measured during Three Working Memory Tasks Using Wireless Functional Near-Infrared Spectroscopy
摘要： Wireless wearable functional near-infrared spectroscopy (fNIRS) has attracted growing attention as a candidate for real-life brain monitoring systems. It is important to determine the onsets at which neuronal activation is evoked by cognitive status in real-time analysis. We propose a machine learning approach for the classification of cognitive event onsets (CogEOs) in hemodynamic signals during three cognitive tasks. The approach does not require a threshold to be set or additional measurement for the rest state. A support vector machine is trained by labeled features obtained from the mean amplitude of hemodynamic changes and then predicts the type of onset points. The problems caused by the imbalance between CogEOs and non-event onsets (NonEO) are solved by oversampling the feature samples labeled by cognitive events. By oversampling, the classification accuracy from an average of five classification scores reaches 74%, 77%, and 75% for the simple arithmetic, 1-back and 2-back tasks. We achieve the best onset classification performance when the NonEOs are randomly distributed and when the subject is performing the 1-back task. Our study extends fNIRS to real-life applications by detecting the time point when brain activation starts among random observations using machine learning without additional triggers or threshold settings.
关键词： functional near-infrared spectroscopy,onset classification,and working memory,classification accuracy
更新于2025-09-04 15:30:14
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Archaeological applications of spectroscopic measurements. Compatibility of analytical methods in comparative measurements of historical Polish coins
摘要： The ED-XRF (energy-dispersive X-ray fluorescence) compact system was used to analyze selected Polish historical coins. The compact X-ray tube developed in the National Centre for Nuclear Research (NCBJ) was used as an X-ray source in the system designed for the ED-XRF studies. The XRF spectra were recorded with the Amptek SDD spectrometer. The elemental compositions of the coins have been determined using above mentioned system and the results were compared to those obtained with WD-XRF method. Other techniques such as SEM-EDX and XRD were also included into this work for comparison. The experimental data show that the X-ray system with transmission type X-ray tube with silver anode operating at 50 kV/30 mA which was developed in NCBJ together with the Amptek SDD spectrometer is an effective tool for chemical composition analyze of historical coins and can be successfully used in archaeometry.
关键词： Elemental composition,Energy-dispersive X-ray fluorescence,X-ray powder diffraction,Scanning electron microscope with Energy Dispersive X-Ray Spectroscopy,Wavelength-dispersive X-ray fluorescence
更新于2025-09-04 15:30:14
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Synthesis, characterization and photocatalytic activity of boron-doped titanium dioxide nanotubes
摘要： Two-step hydrothermal method was used to prepare undoped and boron-doped one-dimensional titanium dioxide (TiO2) nanotubes. Structural properties, thermal stability and microstructural features of the fabricated undoped titanium dioxide nanotubes (TNTs) and boron-doped titanium dioxide nanotubes (BTNTs) were characterized by Xeray diffraction, Raman, Fourieretransform infrared spectroscopy, nitrogen adsorption-desorption isotherms, scanning and transmission electron microscopy techniques. The photocatalytic activity of the fabricated nanotubes was evaluated by using methylene blue degradation. Boron addition to the titanium dioxide nanotubes up to 5% increased the photocatalytic methylene blue degradation ef?ciency. The achieved highest degradation ef?ciency was 81% and it was determined that higher (>5%) boron doped into the titanium dioxide nanotubes resulted in a decreased degradation ef?ciency.
关键词： Titanium dioxide nanotubes,Photocatalyst,Boron,Hydrothermal synthesis,Spectroscopy
更新于2025-09-04 15:30:14
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Photoluminescence Imaging for Buried Defects Detection in Silicon: Assessment and Use-cases
摘要： In this work, the innovative photoluminescence imaging technique is described for applications to buried defect detection in silicon devices. The validity of this emerging technique is first assessed in comparison with well-established characterization techniques (defect selective etching of silicon, X-Ray diffraction topography, cross-sectional transmission electron microscopy imaging and photoluminescence spectroscopy). The paper then describes specific applications illustrating the use of the photoluminescence imaging technique for common processes of the CMOS semiconductor industry. The benefit of this fast, high resolution and non-destructive technique is demonstrated: this includes industrial use of the technique for in-line production control on product wafers.
关键词： photoluminescence imaging,dislocations,non-visual defects,X-Ray diffraction topography,photoluminescence spectroscopy,buried defects
更新于2025-09-04 15:30:14
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Structural, dielectric, and impedance study on ZnO doped Sr(Fe0.5Nb0.5)O3 ceramics
摘要： SrFe0.5Nb0.5O3 (SFN) ceramics doped with ZnO were synthesized via a conventional mixed oxide technique. Phase formation investigation by X-ray diffraction technique (XRD) revealed that all ceramic samples exhibited pure perovskite phase. Grain size as observed by an electron microscopy (SEM), was found to decrease with increasing the additive concentration. Dielectric properties and other related properties of the ceramics were also investigated. Very high dielectric constants > 3.3×105 (at temperature 250 °C and 1 kHz) were found for the 3 vol% doped samples. The impedance spectroscopy analysis suggested that the dielectric behavior of the samples could be linked with the Maxwell - Wagner polarization mechanism.
关键词： Perovskite,High dielectric constant,Ceramics,Maxwell - Wagner polarization,Impedance spectroscopy,SrFe0.5Nb0.5O3
更新于2025-09-04 15:30:14