- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Asphaltenes dissolution mechanism study by <i>in-situ</i> Raman characterization of a packed-bed microreactor with HZSM-5 aluminosilicates
摘要： Asphaltenes, the most aromatic component of heavy oil, are responsible for the fouling and impairment in flow lines, wellbores, and other production facilities in the petroleum industry. Aromatic solvents such as xylenes are commonly used for the asphaltenes’ cleaning process. Understanding the mechanism of asphaltenes’ dissolution in aromatic solvents is significant for the development of a remediation strategy. The reduction of a reactor’s characteristic length scale leads to the decrease in experimental period while providing high throughput information. Microfluidic systems with in-situ spectroscopy is an excellent platform for time-effective studies of the molecular behavior of asphaltenes in simulated sandstone reservoirs. Here, we injected the HZSM-5 zeolite nanoparticles (707 nm ·aggregate-1 in isopropanol solution) with varying Al2O3/SiO2 ratios (from 0 to 1/26) into the quartz porous media to represent reservoirs with different characteristic acidity. In-line UV-Vis spectroscopy enabled the direct measurement of the dissolution percentage, while in-situ Raman spectroscopy revealed where the dissolution took place within the porous media. In addition to bed occupancy, sheet sizes of asphaltenes molecules can also be determined by in-situ Raman spectroscopy. Our results show that the average sheet size of deposited asphaltenes molecules decreased from 2.97 ± 0.25 nm to 2.74 ± 0.26 nm after cleaning the porous media with xylenes. This trend is confirmed with the fluorescence emission spectra of dissolved asphaltenes molecules, where a 10-30 nm red-shift is present when referenced to asphaltenes source samples. These results provide an explanation to why the dissolution percentage of asphaltenes in aromatic solvents increases from 20.15 wt% to 51.00 wt% as the Al2O3 content increases. We can speculate that this increase in weight percentage is attributed to the differences in deposited asphaltenes molecules’ sheet size. These results reveal the importance of π-π interactions during asphaltenes dissolution process in the aromatic solvent. Our results provide the fundamental understanding of asphaltenes dissolution, which otherwise would be challenging to observe using any other analytical methods.
关键词： in situ Raman spectroscopy,Asphaltenes dissolution,Porous media
更新于2025-09-23 15:21:01
-
Optical properties of diamond-like carbon films prepared by pulsed laser deposition onto 3D surface substrate
摘要： It is difficult to grow uniform film by pulsed laser deposition because the spatial distribution of the laser-induced plume is a forward-directed cone-shape. A 3D-motional deposition setup was founded, and the correlative mathematical model of the film thickness on the 3D curved surface was deduced. Based on simulation and optimization, the diamond-like carbon (DLC) film was grown onto the large curved silicon substrate. According to the infrared transmittance spectra, the optical constants of the DLC film samples at different regions on the curved substrate were similar, indicating that the DLC film prepared onto the curved surface was homogeneous. Meanwhile, the deviation of average transmittance in the medium infrared band was below 2.3%, which could improve the imaging performance of the infrared detection. This research is useful to expand the application of the pulsed laser deposition in the optical field.
关键词： uniform transmittance,Raman spectroscopy,3D curved surface,Pulsed laser deposition,DLC film,infrared spectrum
更新于2025-09-23 15:21:01
-
Artificial Intelligence Algorithm Enabled Industrial-Scale Graphene Characterization
摘要： No characterization method is available to quickly perform quality inspection of 2D materials produced on an industrial scale. This hinders the adoption of 2D materials for product manufacturing in many industries. Here, we report an artificial-intelligence-assisted Raman analysis to quickly probe the quality of centimeter-large graphene samples in a non-destructive manner. Chemical vapor deposition of graphene is devised in this work such that two types of samples were obtained: layer-plus-islands and layer-by-layer graphene films, at centimeter scales. Using these samples, we implemented and integrated an unsupervised learning algorithm with an automated Raman spectroscopy to precisely cluster 20,250 and 18,000 Raman spectra collected from layer-plus-islands and layer-by-layer graphene films, respectively, into five and two clusters. Each cluster represents graphene patches with different layer numbers and stacking orders. For instance, the two clusters detected in layer-by-layer graphene films represent monolayer and bilayer graphene based on their Raman fingerprints. Our intelligent Raman analysis is fully automated, with no human operation involved, is highly reliable (99.95% accuracy), and can be generalized to other 2D materials, paving the way towards industrialization of 2D materials for various applications in the future.
关键词： unsupervised learning,graphene,two-dimensional materials,Raman spectroscopy
更新于2025-09-23 15:21:01
-
Spatially resolved covalent functionalization patterns on graphene
摘要： Spatially resolved functionalization of 2–D materials is highly demanded but very challenging to achieve. The chemical patterning is typically tackled by preventing contact between the reagent and material, with various accompanying challenges. Photochemical transformation on the other hand inherently provides remote high spatiotemporal resolution using the cleanest reagent – a photon. Here, we combine two competing reactions on a graphene substrate to create functionalization patterns on a micrometre scale via the Mitsunobu reaction. The mild reaction conditions allow introduction of covalently dynamic linkages, which can serve as reversible labels for surface- or graphene-enhanced Raman spectroscopy characterization of the patterns prepared. The proposed methodology thus provides a pathway for local introduction of arbitrary functional groups on graphene.
关键词： patterned functionalization,Mitsunobu reaction,photochemistry,graphene,Raman spectroscopy
更新于2025-09-23 15:21:01
-
Facile synthesis of La-doped CdS nanoparticles by microwave assisted co-precipitation technique for optoelectronic application
摘要： Low-cost microwave assisted technique has been applied to produce La-doped CdS nanoparticles and their structural, morphological, optical, Raman, dielectric and electrical studies were carried out. Broad XRD peaks revealed the growth of low-dimension La-doped CdS nanoparticles with wurtzite structure. Spherical shape morphology of synthesized nanostructures was confirmed by SEM analysis. SEM mapping and EDAX analysis showed the elemental composition and successful incorporation of La in CdS matrix. Diffused reflectance spectroscopy was used to determine the energy gaps and it was observed to be reduced from 2.47 to 2.3 eV upon La doping. Vibrational studies on La:CdS nanoparticles displayed longitudinal optical modes. PL studies exhibited improved luminescence for the band to band transition of the CdS nanoparticles. The ε’ values are enhanced in general; though it displayed reduced ε’ values at some concentration owing to reduction of polarization. Enhancement in AC conductivity was observed with increasing La concentration and the studies on the involved conduction mechanism revealed that the hopping motion in prepared nanostructures is translation motion with a quick hopping and the behavior is that of ionic conduction.
关键词： FT-Raman spectroscopy,optical properties,dielectric and electrical properties,X-ray diffraction,SEM/EDX,La:CdS
更新于2025-09-23 15:21:01
-
Rapid and Low-Cost Detection of Thyroid Dysfunction Using Raman Spectroscopy and an Improved Support Vector Machine
摘要： This study presents a rapid and low-cost method to detect thyroid dysfunction using serum Raman spectroscopy combined with support vector machine (SVM). The serum samples taken from 34 thyroid dysfunction patients and 40 healthy volunteers were measured in this study. Tentative assignments of the Raman bands in the measured serum spectra suggested specific biomolecular changes between the groups. Principal component analysis (PCA) was used for feature extraction and reduced the dimension of high-dimension spectral data; then, SVM was employed to establish an effective discriminant model. To improve the efficiency and accuracy of the SVM discriminant model, we proposed artificial fish coupled with uniform design (AFUD) algorithm to optimize the SVM parameters. The average accuracy of 30 discriminant results reached 82.74%, and the average optimization time was 0.45 s. The results demonstrate that the serum Raman spectroscopy technique combined with the AFUD-SVM discriminant model has great potential for the detection of thyroid dysfunction. This technique could be used to develop a portable, rapid, and low-cost device for detecting thyroid function to meet the needs of individuals and communities.
关键词： Raman spectroscopy,support vector machine (SVM),optical diagnosis,thyroid dysfunction,parameter optimization
更新于2025-09-23 15:21:01
-
Coexistence of pressure-induced structural phases in bulk black phosphorus: a combined x-ray diffraction and Raman study up to 18 GPa
摘要： We report a study of the structural phase transitions induced by pressure in bulk black phosphorus by using both synchrotron x-ray diffraction for pressures up to 12.2 GPa and Raman spectroscopy up to 18.2 GPa. Very recently black phosphorus attracted large attention because of the unique properties of few-layers samples (phosphorene), but some basic questions are still open in the case of the bulk system. As concerning the presence of a Raman spectrum above 10 GPa, which should not be observed in an elemental simple cubic system, we propose a new explanation by attributing a key role to the non-hydrostatic conditions occurring in Raman experiments. Finally, a combined analysis of Raman and XRD data allowed us to obtain quantitative information on presence and extent of coexistences between different structural phases from ~5 up to ~15 GPa. This information can have an important role in theoretical studies on pressure-induced structural and electronic phase transitions in black phosphorus.
关键词： high pressure,black phosphorus,x-ray diffraction,Raman spectroscopy,phase transitions
更新于2025-09-23 15:21:01
-
Predicted bandgap opening in highly-oriented wrinkles formed in chemical vapour deposition grown graphene
摘要： We present a combined atomic force microscopy and Raman spectroscopy study of wrinkle formation in chemical vapour deposition graphene. Graphene was grown on copper and repeatedly transferred onto a SiO2 substrate to form a four-layer graphene stack. By means of depositing two electrodes with a small gap of 1μm on top of graphene, we can generate a long wrinkle along the channel. Such a wrinkle is pronounced and seems to form at the expense of other wrinkles otherwise present. Along the wrinkle, the strain measured by both atomic force microscopy and polarized Raman is revealed to be of a biaxial type, which is shown, through atomistic modelling, is predicted to produce a sizeable bandgap opening of up to 0.4 eV. Since graphene is normally a zero bandgap material, its applications as an electronic material for devices can be limited. The approach presented in this work could lead to graphene exhibiting a controllable bandgap similar to a semiconductor material that could, therefore, be exploited for the fabrication of graphene-based electronic devices.
关键词： DFT,AFM,Raman spectroscopy
更新于2025-09-23 15:21:01
-
Body Fluids and Spectroscopic Techniques in Forensics: A Perfect Match?
摘要： Human body fluids are of great interest in forensics, due to the possibility to extract their genetic information. At the moment, there is the need to develop a non-destructive, rapid and user-friendly method for the detection and identification of the body fluids usually found at crime scenes: blood, semen, vaginal fluid, saliva, sweat and urine. In this review, the spectroscopic techniques used or being researched on this topic are discussed, taking into account their advantages, limitations and advances. Although, UV-Vis light sources are used worldwide in forensic laboratories for the location of body fluids, they are not selective enough to be confirmatory. HSI, FTIR and Raman spectroscopy seem to be suitable for the identification and discrimination of body fluids, though comprehensive research about some unsolved aspects must be performed first.
关键词： Semen,IR,Saliva,Raman spectroscopy,HSI,Vaginal fluid,UV-Vis,Blood,Body fluids
更新于2025-09-23 15:21:01
-
Microwave Sol-Gel Derived PbY2(MoO4)4:Er3+/Yb3+ Double Molybdate and Their Up-Converted Optical Properties
摘要： PbY2-x(MoO4)4:Er3+/Yb3+ double molybdate phosphors with the correct doped concentrations of Er3+ and Yb3+ (x = Er3+ + Yb3+, Er3+ = 0, 0.05, 0.1, 0.2 and Yb3+= 0, 0.2, 0.45) were precisely prepared using the sol-gel method assisted by the microwave technique; their up-converted optical properties were studied. The particles showed well-crystallized morphology after heat-treated at 900 °C for 16 h. They had a homogeneous and fine morphology with grain sizes of 2-5 μm. After excitation at 980 nm, the PbY1.7(MoO4)4:Er0.1/Yb0.2 and PbY1.5(MoO4)4:Er0.05/Yb0.45 double molybdates provided a strong up-converted emission band of 525 nm, a weak up-converted emission band of 550 nm in the green region and a very weak up-converted emission band of 655 nm in the red region. The spectroscopic spectra of Raman for the doped molybdates showed the presence of strong peaks at higher and lower frequencies. It was induced by highly modulated structures of PbY2-x(MoO4)4 by the incorporation of the Er3+ and Yb3+ ions into the crystal lattice. These results were attributed to the unit cell shrinkage as well as the anion deficient of the MoO4-x group.
关键词： PbY2-x(MoO4)4:Er3+/Yb3+,Sol-gel,Up-converted photoluminescence,Raman spectroscopy,Microwave
更新于2025-09-23 15:21:01