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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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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Non-invasive method to monitor molecular changes in human stratum corneum during acute barrier disruption using reflectance NIR spectroscopy
摘要： Stratum corneum is the outer most part of skin for barrier function. Disorder in stratum corneum is related with many skin diseases including acne, atopic dermatitis and psoriasis. In developed countries, about 20% of the population has disorder in the barrier function of stratum corneum. Adhesive tape stripping is a method to disrupt skin barrier function in studying disorder in stratum corneum. In this study, we obtained NIR (Near-Infrared) spectrum of human skin after tape stripping. Changes in skin spectra after barrier disruption were investigated through principal component analysis (PCA) of spectrum. PCA analysis revealed that peaks for –NH stretching and –CH vibration mainly contributed to the spectral variation caused by barrier disruption. Furthermore, second derivative of spectrum revealed that acute barrier disruption contributes to spectral changes in the region related with secondary structure of protein, lipid and water associated with lipid in stratum corneum. We demonstrated that acute barrier disruption affected features in NIR spectrum. These spectral changes revealed that acute barrier disruption affected keratin protein and ceramide in human stratum corneum. These results suggest that NIR spectroscopy can be used to monitor changes in filamentous network and lamellar structure in stratum corneum. NIR spectroscopy can provide non-invasive method to investigate skin disease related with barrier disruption by monitoring disturbance in protein and lipid structure in stratum corneum.
关键词： protein,barrier disruption,Stratum corneum,tape stripping,water,NIR spectroscopy,lipid
更新于2025-11-14 15:14:40
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Dynamics of infrared excitations in boron doped diamond
摘要： We report on the investigation of relaxation dynamics of optical excitations in IIb high pressure high temperature (HPHT) diamond doped by natural boron and isotopically enriched 11boron. The measurements were performed with a pump-probe technique using short pump pulses from a wavelength-tunable infrared free electron laser. Lifetimes of excited boron states ranging from a few picoseconds to a few hundred picoseconds, have been derived from the obtained data. The relaxation rates depend on the pumped states, the pump intensity and the diamond lattice temperature. We discuss possible contributions to the optical and nonradiative intracenter relaxation rates observed in these experiments. Theoretical simulations support ultrafast relaxation by multiple phonon emission, for the electronic states with the energy gap exceeding the energy of optical phonon.
关键词： time-resolved spectroscopy,boron-doped diamond,diamond
更新于2025-11-14 15:14:40
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Quantification of hexagonal boron nitride impurities in boron nitride nanotubes <i>via</i> FTIR spectroscopy
摘要： Preparation of high-quality boron nitride nanotubes (BNNTs) from commercially available stock is critical for eventual industry adoption and to perform comprehensive experimental studies of BNNTs. Separation of h-BN and BNNTs is a significant challenge, and equally so, quantification of h-BN content in mixed samples is a major challenge due to their nearly identical properties. This work introduces a simple method of quantifying h-BN content in BNNTs based on FTIR analysis. Quantification is achieved by 'spiking' a BNNT sample with pure nanoscale h-BN as an internal standard. To demonstrate the efficacy of the quantification technique two BNNT enrichment methods, surfactant wrapping and centrifugation, and a novel sonication-assisted isovolumetric filtration are introduced. FTIR spectra of enriched samples show clear trends throughout the processes. We propose and demonstrate that FTIR peak ratios of the Transverse and Buckling modes of mixed h-BN/BNNT samples can be used to calibrate and quantify h-BN content in any BNNT sample. Hopefully, this method enables as-received BNNTs to be quantifiably enriched from low purity commercial feedstocks, enabling future development and study of BNNTs and related technology.
关键词： FTIR spectroscopy,Boron nitride nanotubes,hexagonal boron nitride,enrichment methods,quantification
更新于2025-11-14 15:13:28
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Compositional dependence of properties in calcium substituted sodium borophosphate glasses containing $${\hbox {VO}}^{2+}$$ VO 2 + ions
摘要： Synthesis of calcium-substituted sodium borophosphate glasses with compositions xCaO ? (30 ? x)Na2O ? 35B2O3 ? 35P2O5 (x = 0, 2, 5, 7 and 10 mol%, abbreviated as CNVx) containing additional 1.0 mol% of V2O5 following a melt-quench method has been carried out. Different analytical techniques viz. wide angle X-ray diffraction (to con?rm non-crystalline nature), ultraviolet–visible spectroscopy (for optical band gap analysis), infrared absorption spectroscopy (for structural analysis) and differential thermal analysis (to evaluate characteristic temperatures) were employed to characterize the synthesized compositions. The optical band gap is calculated for both indirect allowed and indirect forbidden transitions. The values of the band gap decrease with increasing concentration of CaO (from 5 to 10 mol%) at the cost of Na2O. The cut-off wavelength and Urbach’s energy are determined from the optical absorption spectra and were related to the structural changes occurring in these glasses with an increase in CaO content. The results obtained from Fourier-transform infrared studies con?rm that V2O5 and CaO play the role of network modi?er oxides. Also, the signi?cant shifting in IR bands with an increase in CaO content in the glass matrix suggests the formation of a new boron–oxygen ring. From differential scanning calorimetry measurements it is observed that substitution leads to the increase in natural bond orbitals, high degree cross-linking and thus strengthens the glass network. Glass transition temperature (Tg) is found to increase from 483 to 522?C. Electrical and dielectric properties are analysed using dc conductivity and impedance spectroscopy. Using impedance spectroscopy, different dielectric parameters i.e. dielectric loss (ε(cid:4)), electrical modulus (M ?) and ac conductivity (σac) etc. are evaluated as a function of frequency, temperature and composition. The frequency dependence of impedance exhibits the non-Debye relaxation behaviour and the total conductivity obeys Jonscher’s power law.
关键词： Jonscher’s power law,impedance spectroscopy,Band gap,differential thermal analysis
更新于2025-11-14 14:48:53
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Nd3+ as effective sensitizing and deactivating ions for the 2.87?μm lasers in Ho3+ doped LaF3 crystal
摘要： The efficient 2.87 μm emission of Ho3+: 5I6 → 5I7 transition via Nd3+ sensitization in Nd,Ho:LaF3 crystal was obtained under 808 nm LD excitation for the first time. The lifetime of Ho3+:5I7 decreases dramatically from 26.28 ms to 6.41 ms via Nd3+ co-doping. The mechanism of sensitization and deactivation by Nd3+ was investigated compared with the Ho:LaF3 crystal. The absorption cross-section, emission cross-section, and fluorescence quantum efficiency were estimated and discussed. All the results indicate Nd,Ho:LaF3 crystal an attractive gain medium for solid-state lasers around 2.87 μm under an 808 nm LD pump.
关键词： Spectroscopy,Energy transfer,Nd,Ho:LaF3
更新于2025-10-22 19:40:53
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GaxSe10-x based solar cells: Some alternatives for the improvement in their performance parameters
摘要： We report on strategies that improve Se-derivative based solar cells performance. With this aim, a compact thin film based on ZnO nanoparticles is deposited onto fluorine doped tin oxide (FTO) as an electron-transport layer, in thermally evaporated GaxSe10-x based solar cells. ZnO nanoparticles films are synthesized by sol-gel process whereas GaxSe10-x material is obtained by mechanical alloying. Using current-voltage measurements, impedance spectroscopy, and capacitance-voltage profiling, device characteristics and performance limiting factors are revealed and discussed. Particularly, the use of ZnO nanoparticles results in improved device performance as well as long-term stability. In comparison to Se-only devices with the structure FTO/Se/Au (power conversion efficiency of 0.98%), under 100 mW/cm2 AM 1.5 G illumination the devices achieved a power conversion efficiency of 2.7% with the structure FTO/ZnO/GaSe9/Au (open circuit voltage of 0.71 V, short-circuit current of 7.9 mA/cm2). Hence, an increase of around 175% in the power conversion efficiency is obtained in comparison to Se-only devices. In addition, the effect of others parameters, like thickness of the active layer as well as the gallium contents in the alloy, are discussed.
关键词： Gallium selenide,Solar cells,ZnO nanoparticles,Electric modulus spectroscopy
更新于2025-10-22 19:40:53
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Spectroscopic and theoretical studies of potassium sodium l-(+)-tartrate tetrahydrate and l-tartaric acid used as precursors for in situ laser-induced deposition of the catalytically active copper microstructures
摘要： In this work we study the influence of l-(+)-КNaC4H4O6 × 4H2O (KNaT) and l-H2C4H4O6 (H2T) on the complexation processes occurring during in situ laser-induced catalytic destruction of the organic components of the aqueous solutions with formation of the unsaturated hydrocarbons. For that purpose, ATR-FTIR, Raman, IR, and NIR spectroscopy as well as quantum chemical calculations were implemented. It was observed that hydration of T2? anion via carboxylate groups is stronger than that via hydroxyl groups. We also established the changes in the spectral characteristics of the absorption bands corresponding to vibrations of T2?, HT?, and H2T, at solid state-liquid and acid-salt transitions, depending on concentration of the solution components and the [OH?]/[H2T] ratio. Finally, it was shown that ethylene is a main product of the catalytic destruction of the copper tartrate complexes.
关键词： IR,Laser-induced copper deposition,DFT calculations,Tartaric acid,ATR-FTIR,Catalysis,NIR,Raman spectroscopy,Sodium potassium tartrate tetrahydrate
更新于2025-10-22 19:40:53
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Structural, electronic and optical properties of pulsed laser deposited Cu2SnS3 photo absorber thin films: A combined experimental and computational study
摘要： Pulsed laser deposited thin films of Cu2SnS3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm?1 at 1.5 eV which is comparable to other CuS based materials like CuInS2 and Cu2ZnSnS4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications.
关键词： Annealing,Raman spectroscopy,Thin films,Density functional theory,Pulsed laser deposition,Optical properties
更新于2025-10-22 19:40:53
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Layer-by-layer MoS2:GO composite thin films for optoelectronics device applications
摘要： With reference of our previous report (Appl. Surf. Sci. 2018, ASAP), the molybdenum disulphide (MoS2) thin film were prepared by the dip-coating technique at different temperatures (4000C – 4500C) using methanolic solution of ammonium molybdate and ammonium thiocyanate that are used as bare-substrate for the deposition of graphene oxide (GO) thin films. For the deposition of graphene oxide (GO), commercially purchased GO (0.5 mg in 10 mL aqueous solution) was deposited by dip-coating technique on dip-deposited MoS2 thin film to make layer-by-layer MoS2:GO composite thin films and hence studied their electronic and electrical behaviours. The micro-structural and surface morphology were studied using Raman spectroscopy and field emission scanning electron microscopy, whereas optical band estimated from the optical absorption spectra. The electronic structure and their bonding properties were studied using x-ray photoelectron spectroscopy and the electrical behaviours were observed from the current-voltage (I-V) characteristic curve. The formation of different phases of MoS:GO thin films show an enhanced electronic and electrical performance due to their unique-structure and the synergetic effect of MoS2:GO nanosheets when compared to those of bare MoS2.
关键词： XPS Spectroscopy,Layer-by-layer MoS2:GO composite thin films,I-V curve
更新于2025-10-22 19:40:53