جستجوی مقالات مرتبط با کلیدواژه « raman spectroscopy » در نشریات گروه « علوم پایه »

In this research, micro-Raman spectroscopy has been used for gemstone characterization as a non-destructive and fast method. Afghanistan9s Gemstones such as lapis lazuli, lal, ruby, emerald, and garnet have been used in this research. Afghanistan is one of the most important centers of gems in the world. Non-destructive identification of gems is so important. The samples were collected from different regions of Afghanistan including Badakhshan, Panjshir, Kabul and Nuristan. Then, their microRaman spectra were obtained and analyzed. The main peaks of the Raman spectrum of each sample were determined. Raman spectrum results show that lapis lazuli, lal, ruby, emerald, and garnet have main peaks in the range of 536cm-1, 4208cm-1, 4409cm-1, 4120cm-1, and 907cm-1, respectively. At the end, to compare and confirm the results, XRD characterization of the garnet sample powder, which was possible to crush, was performed. Finally, it can be concluded that the above-mentioned gems can be characterize by micro-Raman spectroscopy, rapidly.

Ferrites are one of the magnetic ceramics that, due to their wide application in various industries, scientists have always tried to optimize their structural, magnetic, electrical, etc. properties. One of the analyzes that scientists use for structural characterization is Raman spectroscopy. In this research, cobalt ferrite nanoparticles doped with cadmium, as well as cadmium-chromium were synthesized. In order to confirm the spinel structure and obtain the structural parameters, X-ray diffraction analysis was performed. The particle size obtained between 53 and 59 nm and the lattice parameter between 8.39 and 8.52 angstroms. The photographs obtained from the Field Emission-Scanning Electron Microscope (FE-SEM) showed that the structure of nanoparticles consists of multi-particle aggregates consisting of spherical nanometer particles. Then the synthesized nanoparticles were subjected to Raman analysis, in addition to determining the spinel type of the samples, the changes in the cations distribution in the spinel lattice were investigated. In this analysis, it was observed that in addition to the five active Raman modes (A1g, Eg, 3T2g) that are characteristic of the spinel structure, other peaks that are characteristic of the mixed spinel structure are also visible in the Raman spectrum of the samples.

Fe3O4 nanoparticles were fabricated by co-precipitation method with stoichiometric and non-stoichiometric ratios in air atmosphere and temperature of 78 °C. Structural analysis of the samples was performed by X-ray diffraction pattern (XRD). The magnetic properties of the nanoparticles were investigated using an alternating force gradient magnetometer (AGFM) and Faraday scale. The XRD patterns indicated that the specimens were single phase and the cubic phase of the magnetic spinel was formed. The diffraction peaks of the XRD pattern are consistent with the reference card 0866-088-01 for the magnetite phase. For non-stoichiometric ratios,  by increasing Fe2+/Fe3+, the Cure temperature decreases compare to the bulk sample (585 °C), due to the decrease in particle size. As the particle size decreases, the number of super-exchange interactions between the sites of the spinel crystal structure decreases. Therefore, by increasing the ratio of divalent iron cation to its trivalent cation, nanoparticles with saturated magnetism and similar coercive force and different Curie temperature can be produced and with less heat energy, the order of the spins is disturbed and the transition from the ferromagnetic phase to the paramagnetic phase occurs. The Raman spectra for the  samples showed specific peaks related to the magnetite structure at 336 cm-1 and 490 cm-1 wave number. Comparison of the Raman spectroscopy of the samples after applying the magnetic field indicated an increase in the number and height of the peaks, which was due to the orientation of the nanoparticles in the direction of the magnetic field.

The Anjir Khajeh area is located in the southern part of Sanandaj-Sirjan metamorphic belt in northwest of Golgohar iron mine. The rock units of the region include metabasites, metasediments, igneous and sedimentary rocks. Metasedimentary rocks containing mica-schist, garnet schist, and garnet staurolite schist, having metamorphosed into greenschist facies and amphibolite facies. Garnet mineral is the most abundant porphyroblasts in metasedimentary rocks which is present in the form of  amorphous to semi-amorphous with the large to medium sizes. Electron Microprobe results show the solid dissolution evidences of garnets with the highest frequency in almandine type. Based on petro-fabric analysis, three generations of garnets are identified that have different chemical and Raman spectral characteristics too. These three generations include Almandine rich, Grossular rich and Pyrope rich  garnets that have been analyzed and classified based on petrography, mineral chemistry and Raman spectroscopy. Almandine rich type with higher Iron content and lowest peak wavenumber under 320 cm-1, Grossular rich type with relatively lower Fe and higher Ca content and highest peak wavenumber between moderate frequencies of 400 to 650 cm-1 and Pyrope rich type with higher Mg and lower Fe content and highest peak wavenumber more than 800 cm-1 can be seen. The petrogenetic investigations of the Anjir Khajeh garnetschists classifies their protholites as shale and sandstone that geodynamicaly formed in a continental island arc setting.

In this paper, the finite difference time domain (FDTD) method is used to estimate the intensity and distribution of localized electric field enhancement in tip-enhanced Raman spectroscopy (TERS) in the vicinity of a conical tip with a diameter of 10 nm. While comparing the enhancement of electric field in two configurations with and without substrate, the effect of using different tip materials in the vicinity of the substrate and also the effect of different thin film coatings on the tip in the amount of electric field enhancement have been investigated. Tips in TERS systems are made of materials such as gold, silver, aluminum, copper, and silicon, as well as a combination of these materials as a coating. Our simulation results can be used to predict the intensity and distribution of a localized electric field enhancement using a suitable geometric and physical structure design for the experimental implementation of TERS.

Regarding the rapid development of optical communication, finding and preparing new materials with very fast and large optical responses are essential for making optical switches and processing equipment. Recently the use of materials smaller than micrometers and nanometers has been studied by researchers for a wide range of applications. The most important of these materials are nanofibers. Also, titanium dioxide is used as one of the most important materials in the field of optical communication. In this research, titanium dioxide nanoparticles with anatase phase were prepared using the sol-gel method and transformed into nanofibers using the electrospinning technique. To improve the performance of these nanofibers, they were also doped with silver nanoparticles. Raman spectroscopy was performed to ensure the purity of the particles of this material. It was found that the samples are all pure titanium dioxide (TiO2) powder in nanoscale and there are no impurities in their structure. The particle distribution of these nanomaterials showed that their size is in the range of 10-20 nm. Conditions for nanofiber electrospinning are: 10 cm distance between the needle and the collector, the feed rate of 2 mL/h, and the maximum voltage used was 15.5 kV. Also, silver colloidal nanoparticles were prepared by Li and Masil experimental method. The structure of fibers was studied in terms of material type using Raman spectroscopy and morphology with an optical microscope and fiber conductivity by FT-IR spectroscopy by determining optical coefficients. Optical microscopy showed that the surface of the nanofibers was smooth and flat and without beads. The diameter distribution of nanofibers was also very narrow (155±5 nm). FT-IR spectroscopy showed that on the surface of nanofibers, there were hydroxyl functional groups that were formed during the preparation of nanofibers. Finally, Raman spectroscopy showed the presence of impurities of silver nanoparticles (15±2 nm).

Masjed daghi ore is located within the magmatic-metallogenic zone of Arasbaran and within the division of structural zones in Iran in Alborz-Azerbaijan zone.The vastest rocks in mineralization area are andesite to trachyandesite. There are latite tuff, agglomerate andesite, and hornblende porphyry basalt in eastern hills and Eocene flysch in south of the regionThe host intrusive rocks of the mineralization are diorite porphyry are diorite porphyry and alterations include potassic, phyllic, argillic and silicification.The most prevalent mineralization texture is the dispersive texture and other open-space-filling texture, vein and veinlets, have been common either.In addition to stock work zones and thick silicate veins, the presence of diorite and maffic dikes, mineralized grey silicate veins, white silicate, silicate-barite, sulfide, gypsum and calcity are among important phenomena Masjed daghi ore.Petrography studies in 26 doubly polished thin sections and the measurement of geothermometry parameters of 105 primary fluid inclusions were carried out in 6 boreholes in four groups of grey silicate, white silicate, white-grey silicate, and silicate-barite veins.The presence of unknown solid phases, opaque solid phases along with salt phases and eutectic temperature (average of -40.86 Co) of fluid inclusions in Masjed daghi reinforced the necessity of recognizing all phases within fluid inclusions. 10 fluid inclusions were selected based on petrography studies and analyzed by laser Raman spectroscopy method. Laser Raman Spectroscopy was utilized and based on the main peaks of Raman intensity of the minerals such as magnetite, anglesite, malachite, serussite, corundum, orthoclase, anhydriteparagonite, hematite, within fluid inclusions in Masjed daghi area was investigated

This study was performed to investigate the chemical composition of the caudal spine in Hemitrygon bennettii (Muller and Henle, 1841) as a source for hydroxyapatite (HA) extraction. Therefore, the chemical structure of caudal spines of fish sampled from the mangrove swamps at Chabahar Bay was determined at calcined (baked at high temperature) and uncalcined conditions. The Raman spectroscopy and ICP-OES were used for structural and elemental analyses, respectively. The sharpest peaks in the Raman were observed at 962cm-1 which was probably due to the symmetric stretching vibrations of apatite phosphates. The adsorbed OH ions also indicated peaks at 3400-3500cm-1 of both calcined and uncalcined samples. The presence of organic residue in uncalcined samples was highlighted by several peaks at 2700-3050 and 1300-1500cm-1 which may be due to both stretching and bending vibrations of CH, CH2 and CH3 groups. Some peaks at 1200-1800cm-1 may also be related to amine residues of proteins. In terms of ion concentrations, high amounts of sodium and magnesium contents in the spine structure (compared to other natural resources of HA extraction) may improve the biocompatibility of extracted HA.

This article deals with evaluate the purity and detection of peppermint essential oil compositions using different spectrometry and refraction spectrometry methods and to compare them with chromatography. The conventional method for identifying and analyzing essential oils is a costly gas chromatography-coupled mass spectrometer. For this purpose, peppermint essential oil extract was first extracted and its main constituents were identified by chromatogram, menthol and menthon. Then using fast and low cost Raman spectroscopy method with three different spectrometers, two compounds of menthon and menthol were determined. Refractometry and FTIR spectroscopy were used to evaluate the purity of peppermint essential oil. Concentrations of 20, 30, 40, 60, 80 and 90 peppermint essential oils were manually made by cyclohexane solvent. These different concentrations and sample were tested by Refractometry and FTIR spectroscopy. As the results show, infrared spectroscopy is not capable of quantitatively identifying the essence of pure peppermint and its diluted concentrations and is only capable of qualitatively identifying different molecules, but can be clearly distinguishable by the use of refractive index analysis of different concentrations and pure samples. Therefore, Raman spectroscopy and refractive analysis is a fast and inexpensive method capable of identifying the major constituents and determining the purity of the essential oils.

The Seh Qaleh agates, located at 120 km NW Birjand, are parts of Central Iranian (Lut block) (Aghanabati, 2004) with geographic coordinates of 58˚ 00′ to 58˚ 30′ longitudes and 33˚ 00′ to 34˚ 00′ latitudes. The host rocks of the agates are Eocene-Oligocene tuff, andesite and basalt. Silica mineralization in the area has occurred inside the volcanic units in the form of filling cavity and fractures. Here, the agates have very attractive textures such as concentric, flow and dogtooth textures that are accompanied with jasper, amethyst, opal, calcite and gypsum.Although Seh Qaleh agates are attractive and delightful, with high economical values, there is no scientific research about them. Therefore, their petrography, geochemistry and Raman spectroscopic characteristics are reported in the present paper for the first time.

More than 400 samples of agates have been collected for this research study and five of these samples were in yellow, white, green, red and black colors. Moreover, four of these rocks were selected for major and trace elements analysis by XRF and ICP-MS. The samples were powdered in Tehran University by a tungsten carbide mill and analyzed in the Zarazma Company (Mashhad). XRD analyses and Raman spectroscopic studies on the agate of the Seh Qaleh area were done in Damghan and Shahrood University of Technology, respectively.

Petrography and Raman spectroscopy:

The combination of different analytical techniques such as polarizing microscope, XRD and Raman spectroscopy provided information about the distribution of silica phases in the Seh Qaleh agates. Polarizing microscopy was used here to distinguish between the chalcedony and quartzine fibrous varieties. Moganite has similar optical properties with chalcedony, whose presence in agate is difficult to reveal. Thus, Raman studies were used to investigate these structural disparities. Raman spectroscopic studies showed that moganite and chalcedony can be distinguished based on their different spectral characteristics (Fig. 4, B, C). The use of a focused laser beam (diameter 1 μm) enabled us to analyze the variations in phase composition in the μm-range.The measurement of Seh Qaleh agates by Raman spectroscopy provided an overview of the quantitative distribution of moganite in the studied samples, in which the fibrous chalcedonies contain more moganite in comparison with nodule chalcedonies (Fig. 4, B, C). The presence and spatial distribution of different silica phases in the Seh Qaleh agates is a result of the primary crystallization processes such as temperature and chemistry conditions (Götze, 2011). Moreover, the presence of moganite and calcite in the Seh Qaleh, confirmed by petrography and XRD studies suggest that the agates had formed in an arid, alkaline environment.

Geochemistry of the agates:

Major and trace elements can be incorporated into the agates by substitution of Si by Al, Fe, Na, and Ca and as inclusions or fluid inclusions. The substitution of these elements are limited due to the small number of ions that have similar ionic radii and valence and can substitute for Si4+ in the crystal structure. The Seh Qaleh agates have 95.78 to 98.9 wt.% SiO2 with minor amounts of Al2O3 (0.01-0.34 wt.%), Fe2O3 (0.01-1.07 wt.%), Na2O (0.11-0.15 wt.%), and CaO (0.01-0.4 wt.%), supplied from alteration of the volcanic host rocks.The high concentrations of U in some of the agates of the study area (especially ~ 38 ppm in the red one) are surprising and propose the operation of specific processes for mobilization, transport and deposition. These processes caused concentrations of U in quartz and chalcedony that can exceed the concentration of U in the Seh -Qaleh volcanic rocks (Table 1).Zielinski (1979) observed a parallel accumulation of Si and U and investigated the mobility of U during the alteration of volcanic rocks. Based on the theory that the transport of chemical compounds is mainly realized by diffusion processes in aqueous fluids (e.g. Si as monomeric silicic acid Si(OH)4), Porter and Weber (1971) inferred for the uranyl ion a complex with monomeric silica UO2SiO(OH)3+. In addition, the presence of calcite, as associated mineral with silica polymorphs and the concentration of Na, K and Ca elements in agates, indicate that volatile chloride compounds might play a role in the alteration of volcanic rocks as well as the mobilization and transport of SiO2 and other chemical compounds (Götze et al. 2012).

Newly minerals could be formed as a result of oxidation, hydrolysis, precipitation and dehydration processes in acid mine drainage (AMD) environment. The occurrence of secondary minerals within the dump No. 7 from Miduk copper mine was studied using mineralogical approaches including X-ray diffraction (XRD), Scanning Electron Microscope (SEM-EDS) and Raman Spectroscopy (RS). Geochemical invetigations, including saturation index and speciation, were conducted on pore water of the dump which simulated from paste pH test. Acidic pH value (ranges from 1.47 to 4.23), a high concentration of SO42- (ranges from 3.95 to 286 g/L) and a high level of Fe (varies from 120.9 to 70860 mg/L) of the waste leached indicate that sulphide oxidation especially pyrite occurs within the dump. Complex FeSO4+ was dominant species of ferric iron in the leached solution phase. According to mineralogical and geochemical studies, newly formed minerals including coquimbite, ferricopiapite, plumbojarosite, rozenite, alunogen and brochantite were identified within the dump. Retention of As, Pb and Cu by iron sulphate, especially coquimbite, were confirmed in the dump. The results of the present study could be employed to develop a comperehensive environmental management program at the mining sites.