- 标题
- 摘要
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Formation and Evolution of Ultrathin Silica Polymorphs on Ru(0001) Studied with Combined in Situ, Real-Time Methods
摘要： Silica mono- and bilayer films on Ru(0001) can be physisorbed or chemisorbed, with ordered or vitreous structures, depending on the particular preparation procedures applied. Using the SMART spectro-microscope at BESSY-II with its capabilities for μ-spectroscopy, μ-diffraction, and LEEM imaging with lateral resolution below 5 nm, in situ and in real time and applied to identical areas, we have investigated the formation of these layers, defined and characterized their properties and their connected morphology, and followed their evolution. Two distinct chemisorbed monolayers and three bilayers (physisorbed crystalline and vitreous, and chemisorbed zigzag phases), and some transitions between them, have been studied. We found that, apart from the deposited silicon amount, the most important parameter for steering the evolution to a particular well-defined layer is the oxygen content at the Ru interface. Nucleation and growth of all layers are homogeneous on the scale of our resolution, leading to rather small domains (20 – 40 nm), mostly of the same phase, separated by defect lines. We discuss these and other basic findings in context and point out open questions. We also offer alternative recipes for the preparation of some phases, to obtain more homogeneous layers on a mesoscopic scale.
关键词： Silica films,SMART spectro-microscope,real-time methods,in situ,LEEM,chemisorbed,physisorbed,polymorphs,Ru(0001),μ-spectroscopy,μ-diffraction
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Analysis of Over-the-Counter Drugs Using Raman Spectroscopy
摘要： Commercial over-the-counter drugs such as Advil?, Aleve?, Tylenol?, Mucinex?, Excedrin?, and aspirin were analyzed with a portable handheld Raman spectrometer. The peaks from their Raman spectra were determined, and common peaks were observed in all samples. Unique peaks were also noticed and used as identifying markers to identify a particular drug. Theoretical calculations of active ingredients present in drugs were also performed, compared with experimental Raman spectra, and used to assign the functional groups responsible for the peaks. In addition, Raman spectra obtained from a benchtop instrument were also compared with that from a portable Raman spectrometer. Different forms and brands of the drugs were also analyzed to determine the effect of other materials on the active ingredient. Results showed that the dosage of active ingredients has a direct impact on the signals exhibited in Raman spectra. Lastly, different degradation processes (exposure to microwaves, UV light, and high temperature) were tested on Tylenol? and results showed peak changes in certain regions and more fluorescence background.
关键词： active ingredients,Raman spectroscopy,over-the-counter drugs,degradation processes,portable handheld Raman spectrometer
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Quantitative Analysis of Xylene Mixtures Using a Handheld Raman Spectrometer
摘要： Xylene isomers (meta-xylene, ortho-xylene, and para-xylene) have been extensively analyzed by different instrumental methods. In this chapter, xylene isomers and their mixtures were analyzed qualitatively and quantitatively by Raman spectroscopy. First, we identified peaks that discriminated each isomer along with peaks that remain unchanged regardless of isomeric form. We used theoretical calculations to aid in the peak assignments. Then, we tested the efficacy of the technique in qualitatively and quantitatively apportioning isomeric mixtures of xylenes.
关键词： Xylene isomers,DFT calculations,Raman spectroscopy,quantitative analysis,handheld Raman spectrometer
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Integration of Raman Spectroscopy in Undergraduate Instruction and Research at Pace University
摘要： The integration of Raman spectroscopy into undergraduate instruction and research at Pace University is discussed in this chapter. This includes the introduction of the principle of Raman instrumentation, first by theory through the use of Gaussian calculations and interpretation of readily available spectra and then using the instrument after the acquisition of a B&W Tek Miniram in 2012. The availability of the instrument allows students to expand their research in sol-gel, ionic liquid, pharmaceuticals, and biodiesel. The development of simple experiments to incorporate into laboratory classes and side-by-side comparisons of experimental results and theoretical calculations are also presented. The challenges and successes of having this instrument in our teaching facility are also described.
关键词： undergraduate instruction,ionic liquid,research,Raman spectroscopy,pharmaceuticals,sol-gel,B&W Tek Miniram,biodiesel,Pace University
更新于2025-09-04 15:30:14
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Chiral Analysis || Chiroptical Spectroscopic Studies on Soft Aggregates and Their Interactions
摘要： The word “aggregation” can encompass several situations ranging from two molecules coming together to form a dimeric structure [1] to several molecules coming together to form an organized assembly. Soft aggregates belong to the latter case where the varying number of molecules can come together to form a supramolecular assembly. This situation often occurs for surfactants (also popularly referred to as amphiphiles) [2], which contain both hydrophilic and hydrophobic groups in their chemical structures. Although there are a number of peptides that are known to aggregate, our focus in this chapter is limited to aggregates formed by surfactants. For a surfactant forming regular micellar structure in water, its molecules initially stay at the air–water interface because the hydrophobic part of surfactant molecules do not have enough affinity to mingle with water molecules. However, at a certain concentration, known as critical micelle concentration (CMC) or critical aggregation concentration (CAC), the air–water interface would have been filled up and surfactant molecules are forced to go into the water solvent. As a consequence, the surfactant molecules assemble together, inside the water solvent, in such a way that the hydrophobic portions of the surfactant molecules form their own interior surface facing away from water molecules. One classic example of these cases is sodium dodecyl sulfate (SDS), which when placed in water forms, above CMC, micellar structures with hydrophilic head groups pointing towards water and hydrophobic tails pointing away from water forming their own interior surface. A different example is Bis(2-ethylhexyl) sulfosuccinate sodium salt (also known as Aerosol-OT and abbreviated as AOT), which when dissolved in nonpolar solvents forms, above CMC, reverse micellar structures with hydrophobic tails pointing towards nonpolar solvent molecules and hydrophilic groups pointing away from the solvent forming their own interior surface. AOTs are known to encapsulate polar molecules, such as water, protecting them from unfavorable repulsive interactions with nonpolar solvent molecules. The assemblies, including micelles, reverse micelles, along with other possibilities such as lamellar, vesicles, ribbon, and rod-like structures [2] are referred to as soft aggregates.
关键词： micelles,critical micelle concentration,aggregation,surfactants,chiroptical spectroscopy
更新于2025-09-04 15:30:14
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[Advances In Atomic, Molecular, and Optical Physics] Volume 67 || Radio-Frequency Spectroscopy as a Tool for Studying Coherent Spin Dynamics and for Application to Radio-Frequency Magnetometry
摘要： The technique of radio-frequency spectroscopy was introduced more than 50 years ago, but is continuing to evolve and is being used as an ever-more versatile tool. We describe the underlying processes that govern the various contributions to the spectroscopic signals, considering the atom-light couplings. We then apply this understanding to demonstrate how the coherent dynamics can be manipulated with different configurations of optical pumping. Finally, we discuss how to implement rf spectroscopy to give optimized sensitivity in atomic magnetometers.
关键词： radio-frequency spectroscopy,atom-light couplings,atomic magnetometry,optical pumping,coherent spin dynamics
更新于2025-09-04 15:30:14
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Methods of improving spatial resolution for IR spectroscopy in atmospheric-pressure plasma systems
摘要： High-temperature, atmospheric pressure plasma systems operated in molecular gases present complex diagnostic challenges. Infrared spectroscopy has been used to make measurements of the absorbance spectrum of complex molecular gas mixtures and thereby calculate the concentrations and species temperatures in these systems. For atmospheric-pressure systems, high spatial gradients arise and high spatial-resolution measurements are thus desirable. Some systems have achieved increased spatial resolution by reducing the beam diameter. However, this increase in spatial resolution comes at the expense of the optical throughput. Here we propose modifying a commercial Fourier Transform, Infrared spectrometer system with a set of simple optical elements. This design allows for scannable, high spatial resolution absorbance spectrum measurements of a complex molecular gas mix. We analyze the signal-to-noise ratio for this design and compare it with the diameter reduction method. For sufficiently low plasma radiation levels, this design improves the signal-to-noise ratio relative to reducing the beam diameter size while transmitting nearly all of the beam power. However, whether this design can achieve the desired sub-mm spatial resolution depends on the radiating area of the infrared light source in the spectrometer.
关键词： Fourier Transform Infrared spectrometer,IR spectroscopy,spatial resolution,atmospheric-pressure plasma systems,signal-to-noise ratio
更新于2025-09-04 15:30:14
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Towards on-chip mid infrared photonic aerosol spectroscopy
摘要： We propose an on-chip mid-infrared (MIR) photonic spectroscopy platform for aerosol characterization to obtain highly discriminatory information on the chemistry of aerosol particles. Sensing of aerosols is crucial for various environmental, climatic, warfare threat detection, and pulmonary healthcare applications. Currently, chemical characterization of aerosols is performed using FTIR spectroscopy, yielding chemical ?ngerprinting because most of the vibrational and rotational transitions of chemical molecules fall in the IR range, and Raman spectroscopy. Both techniques use free space bench-top geometries. Here, we propose miniaturized on-chip MIR photonics-based aerosol spectroscopy consisting of a broadband spiral-waveguide sensor that signi?cantly enhances the particle-light interaction to improve sensitivity. The spiral waveguides are made of a chalcogenide glass material (Ge23Sb7S70) which shows a broad transparency over the IR range (1–10 lm). We demonstrate the sensing of N-methyl aniline-based aerosol particles with the device. We anticipate that the sensor will readily complement existing photonic resonator-based particle sizing and counting techniques to develop a uni?ed framework for on-chip integrated photonic aerosol spectroscopy.
关键词： N-methyl aniline,chalcogenide glass,on-chip mid-infrared photonic spectroscopy,aerosol characterization,spiral-waveguide sensor
更新于2025-09-04 15:30:14
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In-doped As2Se3 thin films studied by Raman and X-ray photoelectron spectroscopies
摘要： Amorphous In-doped As2Se3 films with nominal indium contents x up to 7 at. % were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with a surface roughness near 5 nm, noticeably higher than for similarly prepared undoped As2Se3 film. X-ray photoelectron spectroscopy (XPS) studies enabled the chemical composition of the films to be examined. As follows from the XPS data, the In content in the film strongly decreases with the film depth. For films with x ≥ 2 at.%, Raman features attributed to transverse and longitudinal optical phonons of InAs are revealed in the Raman spectra as an evidence for the formation of InAs nanocrystallites in the As2Se3:In film under laser illumination.
关键词： X-ray photoelectron spectroscopy,amorphous,film,Raman scattering,atomic force microscopy,semiconductor nanocrystals
更新于2025-09-04 15:30:14
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Hydrogen intercalation of CVD graphene on Germanium (001) – strain and doping analysis using Raman spectroscopy
摘要： We report a study of structural properties of graphene grown on germanium (001) when subjected to hydrogen intercalation during cooling, using chemical vapor deposition method. The systematic statistical analysis of the Raman spectra indicated that hydrogen increased the number of structural defects in graphene and caused the increase of the compressive strain. Interestingly, it was also found that hydrogen impacted on charge doping. This findings offer a new insight into the nature of graphene-germanium interaction and constitutes an important step towards graphene integration into modern electronics.
关键词： hydrogen intercalation,raman spectroscopy,graphene on germanium
更新于2025-09-04 15:30:14