Papers by Keyword: Raman Spectroscopy

Abstract: Zinc oxide has taken over modern studies for its suitability for the electronics, sensors, and optical devices industries related to its structural, optical, and electrical properties. This study tries to improve the properties of zinc oxide by doping it with some materials with distinctive properties to add their properties to zinc oxide. So, potassium has been used for its electrical properties, manganese for its high stability, and cobalt for its optical properties. Experiments were done in the same conditions using the chemical weight sol-gel synthesis method. making Zn_0.96 X _0.04O (X = K, Mn, and Co) nanoparticles (NPs). Then, checked how their growth changed the structure of zinc oxide. Using XRD to fix structure and be sure that the doped X completely dissolved in ZnO without changing the structure of the wurtzite. The diffraction patterns demonstrated that all ZnO nanoparticles had hexagonal wurtzite structures and no impurity phase. The crystal sizes using the Scherrer formula are 19.48 nm for pure ZnO, 27.49 nm for Zn_0.96 K_0.04 O, 24.6 nm for Zn_0.96 Mn_0.04 O, and 44 nm for Zn_0.96 Co _0.04 O. The SEM image shows hexagonal wurtzite structure with particles 32 nm in size for pure ZnO and 28, 34, and 54 nm in size for Zn_0.96 X _0.04O, where X = K, Mn, and Co, respectively. The intensity of the Raman spectrum goes down for all X values of Zn_0.96 X _0.04O (X = K, Mn, and Co), and the E_2H peak is found between 430 and 450 cm^-1. The peak intensities get weaker with Mn and Co doping and stronger with K doping. However, the positions of the peaks move slightly when doping, which suggests that the K, Mn, and Co added to ZnO don't change the hexagonal wurtzite structure. This fits well with the XRD patterns that were seen. Rather, it can control the size of the crystal according to the purpose of its use, whether electrical, optical, or for manufacturing sensors.

Abstract: Graphene oxide (GO) and reduced graphene oxide (rGO) were obtained from graphite foil wastes (GFWs) by oxidation with KMnO₄ in the presence of concentrated sulfuric acid at 25–50°C. The resulting GOs were compared with that obtained from flake graphite under the same conditions. The samples were investigated by UV–Vis, FTIR, and Raman spectroscopy methods. Spectroscopic data, as well as EDS and XRD analyses, have shown that the GO samples obtained in both cases are almost identical. The hydrodynamic diameter and ζ-potential of both sample suspensions were also determined. The average particles size of GO(graflex) is 321.5 nm, while the particles size of GO(graphite) reaches 252 nm. The measured ζ-potential values for GO(graflex) and GO(graphite) are –31.58 and –50.04 mV, respectively. Therefore, GFWs can serve as precursor for the production of GOs.

Abstract: Studying the spectroscopic properties of nanomaterials and nanoparticles is essential for developing nanomaterial science and nanotechnology. Spectroscopic properties of nanoparticles of biological origin, especially pathogenic nanoparticles such as viruses, became actual after the Covid-19 pandemic, causing economic, human and social harm. Known spectra of the utmost atoms, molecules, and compositions are well used for identification. In this paper, we provide a concise review of the experimental results obtained from advanced spectroscopy techniques by various scientific groups and demonstrate the possibility of using spectra of viruses to detect and identify diseases caused by pathogens. Raman, ultraviolet (UV), and infrared (IR) spectroscopy methods for experimental study of viral materials are considered.

Abstract: Raman spectroscopy is a powerful tool to analyze materials. The demand for analyzing materials in a smaller analytical region is increasing as technology advances. Tip-enhanced Raman spectroscopy (TERS) is an option. However, measuring the surface of three-dimensional bulk materials is quite challenging, since simultaneously excited micro-Raman signals hide the enhanced nano-Raman signals. In 2024, another approach of using a porous gold membrane was reported to dedicate solid surface analysis. However, this method, for example, sacrifices the lateral analytical spot size because nanopores distribute throughout the membrane. Here, 70-nm thick gold microplates with nano-through-holes in the center are fabricated. The gold microplates provide a smaller analytical spot because nano-through-holes are fabricated only in a spatially limited region. The microplates and the surrounding structures are clearly visible under optical microscopes. We moved gold microplates to another location on a silicon substrate using a manipulator and successfully demonstrated nano-Raman measurements of silicon surface via nano-through-holes. The finite-difference time-domain calculations confirmed that enhanced electric fields are available by the nano-through-holes and revealed that the nano-Raman signals come from the surface of silicon within a depth of 5.4 nm.

Abstract: Metal nitride and binary metal nitride coatings have been widely applied to cemented tungsten carbide (WC) cutting tools to enhance tool life and productivity in machining applications. In this study we report the use of micro-Raman spectroscopy to understand the tribological behavior of one such coating, namely, AlCrN coated cemented WC pins dry sliding on hardened steel (HCHCR) discs. The tribo-testing parameters were chosen based on a correspondence with the cutting force and the cutting speed on a specific machining application. Well-resolved lattice vibrations, arising from the acoustic and optical phonon bands of the crystalline AlCrN coatings, are clearly discernable in the Raman spectra measured on pristine pins. These characteristic signals are utilized to assess the changes occurring in the coatings after tribological experiments. Spatially-resolved, micro-Raman spectra measured on tribo-tested pins suggest that predominantly the AlCrN coatings are intact under the tribological conditions tested here, except for a small region in the middle of the wear scar where the coating appears to have worn off. These spectra also reveal that wear debris composed of iron oxides particles adhered to the pin surface during the tribological testing. Time evolution of the microscopic wear and the adhered oxide layer, were further studied by acquiring Raman spectra through stop-start tribo-tests at different intervals of time. These spectra apart from revealing the evolution of microscopic wear of the coating, also reveal the transitory nature of the iron oxides deposited during the tribo-tests. Deposits of Fe₂O₃ that are initially adhered to the pin surface appear to transform possibly into Fe₃O₄ over a period of time. These spectral observations are discussed in light of the tribological data.

Abstract: In this article, excitation independent and dependent fluorescence properties of surface functionalized carbon dots were studied. The samples were synthesized using a biomass derived Indian gooseberry as carbon precursor via microwave irradiation technique. Concentrated phosphonic acid is utilized as a surface passivator for carbon dots. The formation of spherical carbon dots in the size range of 6 to 12 nm was shown by transmission electron microscopy images. Raman and Fourier transform IR spectroscopies suggest the creation of highly disordered sp³carbon atoms including presence of surface functional groups and interaction of phosphorus with surface of carbon core. From the UV-visible absorption study, absorbance bands at 231 nm and 283 nm attributed to π-π* molecular transitions from carbon core are found. From the photoluminescence measurements, both excitation independent and excitation dependent tunable fluorescence is obtained from ultraviolet to visible (yellow) region of light respectively. The involvement of carbon core electronic states and surface modifier states are responsible for the origin of luminescence and their distinguished nature. The mechanism is discussed and emitted colour are confirmed by CIE plot. The relative quantum yield of the P-functionalized carbon dots is found to be 18.9% with reference to quinine sulfate. The fluorescence in ultra-violet and visible regions is applicable for bioimaging and potential antimicrobial activities.

Abstract: The research describes a new method for silver core-tin oxide shell nanoparticle preparation suitable for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) investigation. The two-step synthesis was performed without intermediate separation. Silver nitrate precursor, sodium citrate reducer, and diethylene glycol stabilizer were used resulting in the formation of large (80 ± 5 nm) silver nanospheres. A thin (8 – 12 nm) tin oxide shell was successfully produced in 40 minutes in an alkaline solution. The synthesized silver core-tin oxide shell nanoparticles demonstrated good stability in weakly acidic (pH 5), neutral (pH 7), and basic (pH 9) media. Long-term (2 – 4 months) stability experiments were also successfully performed in water, acetone, and ethanol. The nanoparticles were applied in the SHINERS study of the classic 4-mercaptobenzoic acid monolayer on Au, highlighting their potential for wider analytical application. The paper provides a detailed explanation of the synthesis, analysis, and application of the silver core-tin oxide shell nanoparticles based on data from UV-Vis, HR-TEM, and SHINERS.

Abstract: Sintering aids play a crucial role in enhancing the properties of various ceramics, offering benefits such as increased density, lowered sintering temperatures, and changes in material electrical characteristics. This study focuses on investigating the impact of 3 wt.% additions of Bi₂O₃, B₂O₃, and V₂O₅ on the structural, morphological, and electrical properties of hexaferrite SrAlFe₁₁O₁₉ ceramics, known for their significance in microwave applications. Obtained by conventional solid-state synthesis, ceramic samples were subjected to X-ray diffraction (XRD) analysis, Raman spectroscopy, scanning electron microscopy (SEM), and resistivity measurements. Results revealed that the addition of Bi₂O₃ and V₂O₅ effectively reduced porosity in hexaferrite ceramics, which can potentially increase the magnetization values of ferrite material. Notably, the sample with 3 wt.% of B₂O₃ exhibited the highest resistivity, reaching 1.9·10⁷ Ω·cm. These findings suggest that incorporating specific sintering aids can help in achieving controlled conductivity and magnetization in hexaferrite ceramics, which is particularly beneficial for microwave components like inductors, antenna substrates, and circulators.

Abstract: Thin films of tungsten oxide were deposited on glass substrates by the radio frequency (RF) reactive sputtering from a high purity tungsten metal target (99.9%) with a diameter of 10 cm. The reactive sputtering was carried out in an argon-oxygen gas mixture containing 20% of O₂ and 80% of Ar. The used RF power is 200 W while fixing the deposition time at 120 min. Finally, the prepared films were annealed at different temperatures (350 °C, 400 °C, 450 °C, 500°C and 550 °C) for 1 hour under air and under vacuum. X-ray diffractograms showed that the deposited thin films crystallized in Hexagonal/Monoclinic WO₃ phase. It was found that the crystallite size varies with the annealing temperature and the lattice parameters is a= 7.3064Å, b = 7.5292Å, c = 7.6875Å and a=b= 7.3242Å, c= 7.6624 Å, for h-WO₃ and m-WO₃ structures, respectively. Scanning Electron Microscopy (SEM), Raman spectra confirmed the formation of WO₃ thin films. In addition, optical transmittance data revealed that the optical bandgap of the films decreases with increasing the annealing temperature. Electrical measurements revealed that annealing in air results in more resistive samples, which should be taken into account in future investigations, especially as buffer layers for efficient photovoltaic solar cells. Keywords: Vacuum, Tungsten oxide, Raman spectroscopy, RF Sputtering method, RF Power, Annealing temperature.

Abstract: Lead-free ferroelectric materials of sodium-potassium bismuth titanate, (1-x)NBT-xKBT systems were synthesized by a hydrothermal process. In this way, the appropriate conditions for the hydrothermal synthesis of NBT and KBT (i.e., concentrations of synthetic precursors, solution pH and temperature) are given graphically. Ceramics of (1-x)NBT-xKBT with (x(mol.%) = 0; 12; 16; 20; 30 and 100) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The rhombohedral-tetragonal morphotropic phase boundary (MPB) was confirmed to be in the region of 0.12 ≤ x ≤ 0.20 for (1-x)NBT-xKBT at ambient temperature. Scherrer's formula and the Williamson-Hall (W-H) analysis were used to examine the average crystallite size and lattice strain. Raman spectroscopy was effectively applied to study the structural evolution of the (1-x)NBT-xKBT phase. The ceramics exhibited a high temperature of maximum dielectric permittivity at (Tmax = 343 °C at 100 kHz) along with electromechanical coupling factors (kp = 0.34, d33 = 147 pC/N). Based on the composition of all specimens, the results indicate a diffuse phase transition, probably of second order, between ferroelectric and paraelectric phases.