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Tailoring chemical and physical properties of graphene-added DNA hybrid thin films
摘要： While the characteristics of DNA and graphene are well studied, the chemical and physical properties of graphene-embedded DNA and cetyltrimethyl-ammonium chloride-modified DNA (CT-DNA) hybrid thin films (HTFs) have been rarely discussed due to the limited development of fabrication methodologies. Herein, we developed a simple drop-casting method for constructing DNA and CT-DNA HTFs added with graphene nanopowder (GNP). Additionally, we demonstrated their distinct characteristics, such as their structure, elemental composition, spin states and chemical functional groups, binding interactions, vibration/stretching modes, UV-Vis absorption, PL, and electrical properties. The EDS spectra of GNP-added DNA HTFs showed C, N, O, Na, and P peaks at characteristic energies. Because of the physical adsorption of GNP on DNA, the peak shifts and suppression of the core spectra of O 1s and P 2p were observed by XPS. The intensity variation of Raman and FTIR bands indicated hybrid formation of GNP in DNA and CT-DNA through adsorption, electrostatic interaction, and π–π stacking. UV-Vis absorption and PL spectra showed the considerable influence of GNP in DNA and CT-DNA HTFs. DNA and CT-DNA HTFs with relatively higher [GNP] showed significant increases of current due to the formation of interconnected networks of GNP in the DNA and CT-DNA HTFs.
关键词： spectroscopy,DNA,electrical property,hybrid thin film,graphene
更新于2025-09-04 15:30:14
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Electron–phonon coupling in single-layer MoS2
摘要： The electron–phonon coupling strength in the spin–split valence band maximum of single-layer MoS2 is studied using angle-resolved photoemission spectroscopy and density functional theory-based calculations. Values of the electron–phonon coupling parameter λ are obtained by measuring the linewidth of the spin–split bands as a function of temperature and fitting the data points using a Debye model. The experimental values of λ for the upper and lower spin–split bands at K are found to be 0.05 and 0.32, respectively, in excellent agreement with the calculated values for a free-standing single-layer MoS2. The results are discussed in the context of spin and phase-space restricted scattering channels, as reported earlier for single-layer WS2 on Au(111). The fact that the absolute valence band maximum in single-layer MoS2 at K is almost degenerate with the local valence band maximum at Γ can potentially be used to tune the strength of the electron–phonon interaction in this material.
关键词： Density functional theory,Angle-resolved photoemission spectroscopy,Transition metal dichalcogenides,Electron-phonon coupling
更新于2025-09-04 15:30:14
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Generating highly specific spectra and identifying thermal decomposition products via Gas Chromatography / Vacuum Ultraviolet Spectroscopy (GC/VUV): Application to nitrate ester explosives
摘要： Gas chromatography/mass spectrometry (GC/MS) is a "workhorse" instrument for chemical analysis, but it can be limited in its ability to differentiate structurally similar compounds. The coupling of GC to vacuum ultraviolet (VUV) spectroscopy is a recently developed technique with the potential for increased detection specificity. To date, GC/VUV has been demonstrated in the analysis of volatile organic compounds, petroleum products, aroma compounds, pharmaceuticals, illegal drugs, and lipids. This paper is the first to report on the utility of GC/VUV for explosives analysis in general, and the first to report on thermal degradation within the VUV cell and its analytical utility. The general figures of merit and performance of GC/VUV were evaluated with authentic standards of nitrate ester explosives (e.g., nitroglycerine (NG), ethylene glycol dinitrate (EGDN), pentaerythritol tetranitrate (PETN), and erythritol tetranitrate (ETN)). In addition, the explosive analytes were thermally degraded in the VUV cell, yielding reproducible, complex and characteristic mixtures of gas phase products (e.g., nitric oxide, carbon monoxide, and formaldehyde). The relative amounts of the degradation products were estimated via spectral subtraction of library spectra. Lastly, GC/VUV was used to analyze milligram quantities of intact and burned samples of double-base smokeless powders containing nitroglycerine, diphenylamine, ethyl centralite, and dibutylphthalate.
关键词： Thermal degradation,Nitrate ester explosives,Vacuum ultraviolet spectroscopy,Gas chromatography
更新于2025-09-04 15:30:14
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Raman thermometry in water, ethanol and ethanol/nitrogen-mixtures from ambient to critical conditions
摘要： We present investigations into remote liquid temperature sensing with Raman spectroscopy using different evaluation methods for the OH stretching vibration band. Water, ethanol and ethanol saturated with nitrogen, all as liquids or liquid-like supercritical fluids, are pumped through a heated microcapillary system at elevated pressures. Raman spectra are recorded from the liquid inside the microcapillary and are evaluated with respect to the temperature sensitivity of the OH stretching vibration. The four approaches applied are (i) to evaluate the center position of the Raman OH-band, (ii) the integrated absolute difference spectrum, (iii) the intensity ratio of two regions of the OH-band, and (iv) the intensity ratio of two fitted Gaussian peaks. The temperature range investigated covers from ambient temperature to the component’s respective boiling temperature or critical temperature at sub- and supercritical pressures. Precision and robustness of the employed methods are characterized. It is shown that two out of the four methods feature temperature deviations smaller than 5 K at all pressures, and that one method can also be applied to liquid mixtures of ethanol and nitrogen. Applicability to other liquids and mixtures is discussed.
关键词： temperature sensing,supercritical fluids,OH stretching vibration,water,Raman spectroscopy,nitrogen,microcapillary,ethanol
更新于2025-09-04 15:30:14
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A novel experimental approach for liver analysis in rats exposed to Bisphenol A by means of LC-mass spectrometry and infrared spectroscopy
摘要： An innovative complementary approach using a liquid chromatographic-mass spectrometer method and infrared spectroscopy is proposed for measuring internal biological exposure to dangerous chemical contaminants and for monitoring biochemical changes in target organs. The proposed methodologies were validated and applied in the case of rats exposed to low-doses of Bisphenol A (BPA). A liquid chromatographic method coupled to a tandem mass spectrometer was used in order to measure BPA concentration in rat livers. BPA was detected at different levels in all liver samples from BPA-treated rats, although the exposure dose was the same in all treated animals, and also from control rats, highlighting the difficulties in eliminating external uncontrolled exposure and the need for internal biological monitoring. Fourier Transform Infrared analysis was applied to detect structural changes occurring in several molecules (lipids, proteins, carbohydrates and nucleic acids) as well as the presence of specific metabolic processes. The spectroscopic analyses clearly demonstrated a different lipid composition more than an evident lipid accumulation and a glycogen accumulation decrease, revealing a metabolic disturbance in livers with a normal histological aspect. These results demonstrated the potential of an integrated approach based on mass spectrometry and infrared spectroscopy to evaluate at an early stage the hepatotoxic effect of BPA exposure in an animal model. This approach can be usefully exploited in all the investigations aimed to provide better information concerning the interrelationships between contaminant exposure, dose, and health effects.
关键词： Bisphenol A exposure,Metabolic disturbance,Rat liver,Mass spectrometry,Infrared spectroscopy
更新于2025-09-04 15:30:14
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Process Analytical Technology for Online Monitoring of Organic Reactions by Mass Spectrometry and UV–Vis Spectroscopy
摘要： Process analytical technologies (PATs) are used in the pharmaceutical and other industries to monitor chemical processes in real-time with analytical instrumentation. Each PAT analyzer brings its own advantages and disadvantages to the process, and multiplexing PAT analyzers can be advantageous as they can provide confirmatory measurements and increase the overall confidence of the analysis. In a pedagogical setting, online reaction monitoring enables the instructor to explain the fundamentals of instrumental techniques while highlighting pertinent real-world applications. Here we present a teaching laboratory exercise in which students monitor an amide bond formation reaction by flow UV?vis spectroscopy and by mass spectrometric analysis. The coupling of these two specific instruments allows students to investigate two instruments in one laboratory exercise, to explore the fundamentals behind each, and to contemplate the advantages and disadvantages of these instrumental methods. The coupling of the two instruments was aided by 3D printing which allowed students to explore how rapid prototyping can enable the development of innovative procedures.
关键词： Organic Chemistry,Mass Spectrometry,UV?Vis Spectroscopy,Laboratory Instruction,Instrumental Methods,Hands-On Learning/Manipulatives,Upper-Division Undergraduate,Analytical Chemistry,Reactions
更新于2025-09-04 15:30:14
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Photoelectron Spectroscopy and Theoretical Study of Cr <sub/><i>n</i> </sub> Si <sub/> 15– <i>n</i> </sub><sup>–</sup> ( <i>n</i> = 1–3): Effects of Doping Cr Atoms on the Structural and Magnetic Properties
摘要： CrnSi15?n? (n = 1?3) clusters were investigated by using size-selected anion photoelectron spectroscopy combined with density functional theory calculations. The results show that the most stable structure of CrSi14? is of C2v symmetry with the Cr atom encapsulated in a Si14 cage which can be viewed as a boat-shaped Si10 unit capped by four additional silicon atoms. A large HOMO?LUMO gap of neutral CrSi14 is confirmed based on the photoelectron spectrum of CrSi14?. Cr2Si13? has two isomers nearly degenerate in energy: one can be characterized as one Si atom interacting with a Cr2Si12 hexagonal prism while the other can be viewed as one Si atom capping a distorted Cr2Si12 hexagonal antiprism. Cr3Si12? has a D6d symmetric wheel structure in which three Cr atoms form an axle surrounded by 12 Si atoms. The magnetic moments of CrSi14?, Cr2Si13?, and Cr3Si12? increase from 1 to 3 μB and then to 7 μB with the increasing number of Cr atoms in the clusters. The magnetic moments of Cr2Si13? and Cr3Si12? are mainly contributed by the surface Cr atoms.
关键词： Photoelectron spectroscopy,Silicon clusters,Chromium doping,Density functional theory,Magnetic properties
更新于2025-09-04 15:30:14
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Combined Raman- and AFM-based detection of biochemical and nanomechanical features of endothelial dysfunction in aorta isolated from ApoE/LDLR?/? mice
摘要： Endothelial dysfunction is recognized as a critical condition in the development of cardiovascular disorders. This multifactorial process involves changes in the biochemical and mechanical properties of endothelial cells leading to disturbed release of vasoprotective mediators. Hypercholesterolemia and increased stiffness of the endothelial cortex are independently shown to result in reduced release of nitric oxide and thus endothelial dysfunction. However, direct evidence linking these parameters to each other is missing. Here, a novel method combining Raman spectroscopy for biochemical analysis and Atomic Force Microscopy (AFM) for analysing the endothelial nanomechanics was established. Using this dual approach, the same areas of native ex vivo aortas were investigated, either derived from mice with endothelial dysfunction (ApoE/LDLR-/-) or wild type mice. In particular an increased intracellular lipid content and elevated cortical stiffness/elasticity was shown in ApoE/LDLR-/- aortas, demonstrating a direct link between endothelial dysfunction, the biochemical composition and the nanomechanical properties of endothelial cells.
关键词： Atomic Force Microscopy,Endothelial dysfunction,hypercholesterolemia,endothelial nanomechanics,Raman spectroscopy
更新于2025-09-04 15:30:14
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Three-channel filter-based non-imaging passive ranging system based on oxygen absorption
摘要： A three-channel ?lter-based non-imaging passive ranging system based on oxygen absorption is proposed and demonstrated. This system utilizes three band pass ?lters to quickly estimate the oxygen band-average transmission near 762 nm, and uses three simultaneous spectral measurement channels which are de?ned by the di?erent band pass ?lters to capture the three band pass signals of the target. A short range experiment from 100 m to 300 m and a long range experiment at 1945 m are conducted with a 1000 W halogen lamp, and the measured band-average oxygen transmission of the both experiments are compared to the predicted curve derived from the line-by-line transmission model to estimate the range. Averaged range error of 2.14% is achieved in the short range experiment and range error of 6.72% is obtained in the long range experiment.
关键词： Passive ranging,Oxygen spectroscopy,Atmospheric absorption,Three-channel,Filter-based
更新于2025-09-04 15:30:14
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Charge transport layers manage mobility and Carrier density balance in light-emitting layers influencing the operational stability of organic light emitting diodes
摘要： Organic light emitting diodes (OLEDs) consist of several organic layers, including the charge injection layer, charge transport layer, and light emitting layer (EML). Of these layers, the charge transport layer is crucial for ensuring device longevity, but its overall effects on charge transport and corresponding device stability are poorly understood. Herein we report the factors influencing differences in lifetime between two OLEDs with different hole transporting layers (HTLs). Comprehensive electrical analysis of the materials and the devices reveals that the mobility, accumulation, trapping, and the transport path of holes in the EML are totally changed by the HTLs. The charge transport layers affect mobility and carrier density balance in the EML through the modification of the charge transport path and the energetic barrier. This results in a reduction of overbalanced polaron density, which is critical for bond dissociation in excitonic interactions. Consequently, device lifetime is increased sevenfold through modification of the HTL structure without any alteration of the EML. These results imply that the analysis of polaronic transport through impedance spectroscopy is a crucial step in determining the requisite electrical properties for charge transport layers, with a view to maximizing the operational stability of OLEDs.
关键词： charge transport,Organic light-emitting diodes,device stability,impedance spectroscopy
更新于2025-09-04 15:30:14