Raman Spectra
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2021 ◽  
Author(s):  
Muhammad Azeem

Abstract Raman spectra are collated from the cement paste matrices of CNTs, ZnO, Gd2O3, and SiO2. The spectra show that CNTs do not take part in hydration process and therefore concentration of calcium silicate hydrate (CSH) is unchanged in CNT-OPC matrix. The metal oxides, on the other hand, have shown significant effects on the CSH concentration. The CSH concentration increases with the increase of ZnO weight percent in the matrix whereas spectra collected from Gd2O3 matrix shows the strongest CSH vibrational bands. Moreover, vibrational bands of CaCO3 also become weak in the matrices with Gd2O3. The addition of SiO2 however had opposite effects that is by increasing the weight percent of SiO2 in the matrix, the CSH concentration is decreased. Since CSH acts a glue in a binder, the study shows that its concentration can be controlled by adding foreign elements. Such binders are expected to show improved strength and durability.


2021 ◽  
Author(s):  
Yi Liu ◽  
Yu-Fan Zhang ◽  
Shan Jin ◽  
Si-Pu Li ◽  
Ming-Ming Yang ◽  
...  

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257470
Author(s):  
Till Jasper Meyer ◽  
Elena Gerhard-Hartmann ◽  
Nina Lodes ◽  
Agmal Scherzad ◽  
Rudolf Hagen ◽  
...  

Background The entity assignment of salivary gland tumors (SGT) based on histomorphology can be challenging. Raman spectroscopy has been applied to analyze differences in the molecular composition of tissues. The aim of this study was to evaluate the suitability of RS for entity assignment in SGT. Methods Raman data were collected in deparaffinized sections of pleomorphic adenomas (PA) and adenoid cystic carcinomas (ACC). Multivariate data and chemometric analysis were completed using the Unscrambler software. Results The Raman spectra detected in ACC samples were mostly assigned to nucleic acids, lipids, and amides. In a principal component-based linear discriminant analysis (LDA) 18 of 20 tumor samples were classified correctly. Conclusion In this proof of concept study, we show that a reliable SGT diagnosis based on LDA algorithm appears possible, despite variations in the entity-specific mean spectra. However, a standardized workflow for tissue sample preparation, measurement setup, and chemometric algorithms is essential to get reliable results.


Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1125
Author(s):  
Bui Thi Thuc Hien ◽  
Vu Thanh Mai ◽  
Pham Thi Thuy ◽  
Vu Xuan Hoa ◽  
Tran Thi Kim Chi

ZnSe nanoparticles (NPs) were prepared by combining both hydrothermal and mechanical milling methods. Transmission electron microscopy images show that fabricated ZnSe NPs with a sphere-like shape have an average size (d) in the range of 20–100 nm, affected by changing the milling time from 10 to 60 min. All the samples crystalize in zincblende-type structure without impurities, as confirmed by analyzing X-ray diffraction patterns, Raman spectra, and energy-dispersive X-ray spectroscopy. Carefully checking Raman spectra, we have observed the broadening and redshift of vibration modes as decreasing NP size, which are ascribed to extra appearance of disorder and defects. The photoluminescence study has found a blue emission at 462 nm attributed to the excitonic near-band edge and a broad defect-related emission around 520–555 nm. Increasing milling time leads to the decrease in the exciton-emission intensity, while the defect-related emissions increase gradually. Interestingly, as decreasing d, we have observed an improved photodegradation of Rhodamine B under UV irradiation, proving application potentials of ZnSe NPs in photocatalytic activity.


2021 ◽  
Vol 130 (10) ◽  
pp. 104302
Author(s):  
Amol Ratnaparkhe ◽  
Santosh Kumar Radha ◽  
Walter R. L. Lambrecht

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2396
Author(s):  
Valery Davydov ◽  
Eugene Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  

We present an extensive theoretical and experimental study to identify the effect on the Raman spectrum due to interface interdiffusion between GaN and AlN layers in short-period GaN/AlN superlattices (SLs). The Raman spectra for SLs with sharp interfaces and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of the random-element isodisplacement model. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, showed that the bands related to A1(LO) confined phonons are very sensitive to the degree of interface diffusion. As a result, a correlation between the Raman spectra in the range of A1(LO) confined phonons and the interface quality in SLs is obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy.


2021 ◽  
Vol 8 ◽  
Author(s):  
Yi-Feng Zhao ◽  
Zhao Guan ◽  
Ni Zhong ◽  
Fang-Yu Yue ◽  
Ping-Hua Xiang ◽  
...  

Raman spectra play a significant role in the study of polar materials. Herein, we report the influence of strain and interlayer shift on vibration responses in bulk and few-layer ferrovalley material GeSe in different polarization states (ferroelectric/FE and antiferroelectric/AFE) based on density functional theory and density functional perturbation theory calculations. We find Ag1 mode shifts by about 10 cm−1 from monolayer to bilayer and trilayer due to the interlayer coupling. The Ag3 mode on behalf of FE mode is observed that is consistent with the experiments in bulk and few-layer GeSe. Meanwhile, in our calculations, with the transition between AFE and FE state in the bilayer and trilayer, the Raman frequency of Ag2 and Ag3 mode decrease obviously whereas that of Ag1 mode increases. Interestingly, the Raman peaks shifted a lot due to the strain effect. We expect these variations in the Raman spectroscopy can be employed to identify the status of GeSe films, e.g., the AFE or FE state, and the number of layers in experiments.


2021 ◽  
Vol 11 (18) ◽  
pp. 8358
Author(s):  
Maria Połomska ◽  
Leszek Kubisz ◽  
Jacek Wolak ◽  
Dorota Hojan-Jezierska

The development of regenerative medicine turns attention toward native collagen as a biocompatible material. Particularly interesting is fish skin collagen, which is relatively easy to extract comparing mammalian tissues and free of some pathogens that are dangerous to humans. The paper presents results of IR Raman spectroscopy studies of silver carp (Hypophthalmichthys molitrix) skin collagen. As collagen properties result from its structure and conformation, both sensitive to temperature, FT NIR Raman spectroscopy is an excellent tool to characterize the molecular structure of fish skin collagen, particularly in temperature range typical for the manufacturing processes of biomedical products. Therefore, the Raman spectra were recorded in a temperature range of 300 to 403 K. The analysis of Raman spectra of prepared collagen films, particularly in the range of the bands related to amide I and amide III entities, showed a high content of α-helix and α-helix type molecular organization in fish skin collagen. Additionally, the secondary structure of the studied fish skin collagen is stable up to ~358 K. Heating to 403 K leads to irreversible changes in the molecular structure of fish skin collagen. It was found that the Raman spectrum of fish skin collagen preheated in this manner becomes similar to the spectrum of the collagen obtained from bovine Achilles tendon, whose secondary structure does not change up to 403 K.


Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5484
Author(s):  
Rangsan Panyathip ◽  
Sukrit Sucharitakul ◽  
Surachet Phaduangdhitidhada ◽  
Athipong Ngamjarurojana ◽  
Pisist Kumnorkaew ◽  
...  

Graphene Quantum dots (GQDs) are used as a surface-enhanced Raman substrate for detecting target molecules with large specific surface areas and more accessible edges to enhance the signal of target molecules. The electrochemical process is used to synthesize GQDs in the solution-based process from which the SERS signals were obtained from GQDs Raman spectra. In this work, GQDs were grown via the electrochemical process with citric acid and potassium chloride (KCl) electrolyte solution to obtain GQDs in a colloidal solution-based format. Then, GQDs were characterized by transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy, respectively. From the results, SERS signals had observed via GQDs spectra through the Raman spectra at D (1326 cm−1) and G (1584 cm−1), in which D intensity is defined as the presence of defects on GQDs and G is the sp2 orbital of carbon signal. The increasing concentration of KCl in the electrolyte solution for 0.15M to 0.60M demonstrated the increment of Raman intensity at the D peak of GQDs up to 100 over the D peak of graphite. This result reveals the potential feasibility of GQDs as SERS applications compared to graphite signals.


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