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The influence of particle size on the intensity and reproducibility of Raman spectra of compacted samples
摘要： Given the growing interest in the application of Raman spectroscopy for quantitative purposes in solid pharmaceutical preparations, a revision of the effect of particle size on Raman spectra of compacted samples is presented. For this purpose, a set of tablets of potassium hydrogen phthalate (KHP) of different particle size were prepared. KHP was used because of its purity and stability, which allow to consider that samples will not be altered during measurements; but also because of its chemical structure (aromatic ring and carboxylic groups), that are present in many active pharmaceutical ingredients (API). The latter makes possible to consider KHP as a model pseudo-API. As KHP tablets only contain a pure compound, the mapping strategy that was considered for measuring our samples will not be affected by subsampling issues. The spectra variance can be attributed to the intrinsically reproducibility in recording the spectra (which mainly depends on the instrument set-up) and the site-to-site differences in elastic scattering properties. Two different instrumental optics have been studied: a macro-Raman system and a Raman microscope (500 μm and 50 μm laser spot size, respectively). The effect of the spectra preprocessing is also evaluated. The overall results demonstrate raw Raman intensity increases with particle size up to a value that depends on tablet width and that the applied spectral preprocessing (baseline correction and a unit vector normalization), reduces the differences in Raman intensities due to the particle size, but does not completely eliminate it for the lower particle sizes (< 20 μm). For tablets containing particles with predefined sizes, it corrects the mapping site-to-site differences in elastic scattering.
关键词： Raman spectroscopy,Peak intensity,Reproducibility of a raman spectrum,Particle size
更新于2025-11-14 15:16:37
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Red-light Emission of Li-doped Ga2O3 One-dimensional Nanostructures and the Luminescence Mechanism
摘要： Li-doped Ga2O3 one-dimensional nanostructures were synthesized by thermal evaporation. The observation results of morphology show that there are plenty of one-dimensional nanostructures in the sample. Raman spectra of samples show excellent crystallinity and the Raman peaks of the Li-doped Ga2O3 have red-shifted compared to the “undoped” Ga2O3 in the low wavenumber section. Comparing the photoluminescence behavior of the two samples at room temperature, they were found to have blue light emission peaks, but the emission peak of Li-doped Ga2O3 is blue-shifted. Additionally, there is a strong red light emission peak centered at 692 nm in the spectrum of Li-doped Ga2O3.
关键词： Li-doped,Nanostructures,Photoluminescence,Ga2O3,Raman spectrum
更新于2025-09-23 15:23:52
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Raman spectrum of nanocrystals: Phonon dispersion splitting and anisotropy
摘要： The effects of anisotropy and splitting of the phonon dispersions in the Raman spectrum of nanocrystals are investigated. We describe the different branches of the optical phonon dispersion curves along each high-symmetry direction by fitting a simple empirical model to experimental data. These curves are then used to calculate the Raman spectrum in the framework of the phonon confinement model and the results are compared with a wide range of available experimental data as well as with the spectra predicted by currently available models based on a single isotropic dispersion curve. We show that by considering the anisotropy and splitting of rigorously obtained optical phonon dispersions, the commonly observed deviations between experimental and theoretical data are strongly reduced. Our work enables the extraction of significantly more accurate information about relevant physical properties of nanocrystals from Raman spectroscopy.
关键词： splitting,anisotropy,nanocrystals,phonon dispersion,Raman spectrum
更新于2025-09-23 15:21:01
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Studies on As-synthesized Graphene Oxide Flakes
摘要： Background: Due to the single atomic layer, flexible material, easily tuned of band gap, easily reduced to reduced graphene oxide, graphene oxide (GO) have a lot of application for Electronics, Biosensors, Biomedical application. Objective: The goal of the present work is to study the electrochemical properties of graphene oxide flakes. Method: In the present work, we synthesis of graphene oxide using modified hummer techniques. The morphological and structural characterization of as-prepared GO was investigated with the help of XRD, SEM, FTIR, UV, CV. Results: The XRD patterns of As-prepared graphene oxide (GO) flakes shows a peak at 11.2°, and the calculated value of lattice parameter comes out to be 15.56 A°. The peaks in the Raman spectrum are observed at 1599 cm-1 and 1349 cm-1, which confirms the lattice distortion in the graphene oxide (GO). The peaks in the FTIR spectrum of graphene oxide (GO) observed at, 3636 cm-1, 1753 cm-1, 1649 cm-1, 1456 cm-1, and 1177 cm-1 are attributed to O-H, C=O, C=C, C-OH, C-O bonds, respectively. The electrochemical studies of graphene oxide (GO) modified ITO electrode shows an improvement in the electrochemical parameters. Conclusion: We have prepared the graphene oxide by modified Hummers method. According to the electrochemical studies, graphene oxide (GO) modified ITO electrode is an excellent medium for the fast electron transfer between an electrode surface and electrolyte. On the basis of these studies, it is suggested that graphene oxide may be a best material for the fabrication of biosensors.
关键词： electrochemical studies,FTIR spectrum,Graphene oxide,raman spectrum,Biosensors,Biomedical application
更新于2025-09-19 17:15:36
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Electro-optic evolution driven by static and relaxational nano ferroelectric domains in KTa <sub/>1a??x</sub> Nb <sub/>x</sub> O <sub/>3</sub>
摘要： Polar nano-regions (PNRs), whose evolution and response mechanism are unclear, were identified to be responsible for the pivotal large electro-optic (EO) coe?cients near the TC in KTa1(cid:2)xNbxO3 (KTN) crystals. To investigate this phenomenon, the temperature dependence of its Raman spectrum, and of its linear e?ective and quadratic EO coe?cients, were investigated. Our results showed that both the relaxational nano-domains driven by biased electric fields under ordered static domains and strong anisotropy determined by the deformation of the NbO6/TaO6 realize enhancements of EO properties in the vicinity of Tf. We expect this understanding of the dynamic EO characteristics to be valuable for developing photonic devices and for providing a basis for exploring the origin of giant EO and piezoelectric e?ects in disordered ferroelectrics and relaxors.
关键词： KTa1(cid:2)xNbxO3,Ferroelectrics,Polar nano-regions,Raman spectrum,Electro-optic
更新于2025-09-19 17:13:59
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Effect of Potassium Nitrate in ZnO Nanoparticle Synthesis to Study the Performance of Dye Sensitized Solar Cell
摘要： X-ray diffraction, Raman investigations, band gap energy of zinc oxide nanoparticles (ZnO NPs) along with current-voltage characteristic curves of an assembled dye-sensitized solar cell (DSSC) are presented in this article. ZnO NPs were first synthesized with and without potassium nitrate (KNO3) salt by precipitation method from precursor solutions of zinc acetate and sodium hydroxide. Then, their thin films were deposited on FTO substrates from the paste made with acetic-acid glacial, and Triton X-100 in ethanol by doctor blade method. The X-ray diffraction (XRD) pattern of ZnO NPs prepared without KNO3 annealed at 500 °C showed a hexagonal wurtzite structure with preferred orientation along (101) planes and crystallite size of 25 nm. Very similar XRD pattern was found for ZnO NPs prepared with KNO3. The crystallite size was found decreased to 17 nm for ZnO NPs made with KNO3 salt. Raman spectrum of ZnO NPs showed the presence of E2 high or E2(2) peak at 437 cm-1. The optical band gaps of the ZnO thin films prepared from ZnO NPs with and without KNO3 were measured to be of 3.16 eV and 3.26 eV, respectively. After sensitizing the above-prepared ZnO films by dye extract of Artocarpus lakoocha, the dye-sensitized solar cells were prepared, and their performance was tested by measuring I-V curves under light illumination of the power density of 1000 W/m2. The measurement showed highest Isc and Voc of 44 μA and 326 mV, respectively.
关键词： Dye-sensitized solar cell,Band gap energy,ZnO nanoparticles,X-ray diffraction,Raman spectrum
更新于2025-09-16 10:30:52