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Evolution of nanocrystal size distribution in porous silicon nanoparticles during storage in aqueous media: X-ray diffraction analysis
摘要： X-ray diffraction studies of electrochemically prepared mesoporous and microporous silicon particles were carried out to monitor their dissolution in aqueous media. The dissolution process was found to result in either decreasing or an increasing of the mean size of silicon nanocrystallites in mesoporous and microporous samples, respectively. The evolution of nanocrystallite size was related by polydispersity of the initial size distribution and it was described by using a model of Bshrinking spheres.^ The proposed approach was used to confirm an effect of biopolymer surrounding of silicon nanocrystallites on their stability in aqueous medium. The obtained results and developed model can be useful for potential biomedical applications of porous silicon.
关键词： Biomedical applications,Oxidation,Nanoparticles,Diffraction,Silicon,X-ray
更新于2025-09-19 17:15:36
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[IEEE 2018 International Conference on Electromagnetics in Advanced Applications (ICEAA) - Cartagena des Indias (2018.9.10-2018.9.14)] 2018 International Conference on Electromagnetics in Advanced Applications (ICEAA) - Two-parameter expansions and ray representation of the fields diffracted at thin-to-thick curved dielectric layers and conducting bodies
摘要： In this study, we introduce a uni?ed approach that allows to construct the asymptotic procedure for various high-frequency electromagnetic diffraction problems at curved dielectric, conducting, and absorbing layers, and to obtain the curvature correction to solutions. The method proposed is based on the combination of ray representations and the expansions typical for the boundary-layer technique: we seek the ?eld as a ray series, whose coef?cients are the functions of a point in space, the more “stretched” along the normal to one of the boundaries, the thicker layer is. The asymptotics are derived both in 2D and 3D formulations and are validated by comparison with analytical and numerical solutions of canonical problems.
关键词： dielectric layer,curvature,conductors,higher-order diffraction
更新于2025-09-19 17:15:36
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Spectroscopic ellipsometry and morphological characterizations of nanocrystalline Hg1-xMnxO oxide diluted magnetic semiconductor thin films
摘要： The structural, optical spectroscopic ellipsometry and morphological properties of nanocrystalline Hg1-xMnxO (0 ≤ x ≤ 0.2) oxide diluted magnetic semiconductor thin films synthesized by electron beam deposition technique have been investigated by means of X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) techniques. All the deposited films crystallize in the form of a hexagonal crystal structure. The integration between X-ray and atomic force microscopy data shows a very good agreement for the nanosize nature of the deposited films. For the surface roughness, good matching between the results of SE and AFM measurements was observed. In the spectral range 200–1200 nm, the real part (ε1) and imaginary part (ε2) of the dielectric constant of nanocrystalline Hg1-xMnxO films have been extracted from SE measurements. At fixed energy value, the ε1, consequently the refractive index is found to decrease with increasing Mn2+ dopant. In contrary, the energy gap (Eg) of the deposited films determined from the ε2 is found to increase as the Mn2+ concentration increases. The variation of both the ε1 and Eg as a function of Mn2+ concentration is understood based on Lorentz-Lorenz relation and sp-d exchange interaction, respectively. The results reported here show that Mn-doped HgO nanocrystalline films could be employed in the fabrication of nanoscale optical and magneto-optical devices.
关键词： Atomic force microscope,Vapor deposition,Spectroscopic ellipsometry,Optical properties,Semiconductors,AFM,Optical materials,Nanostructured materials,Thin films,X-ray diffraction
更新于2025-09-19 17:15:36
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Studying the influence of deposition temperature and nitrogen contents on the structural, optical, and electrical properties of N-doped SnO2 films prepared by direct current magnetron sputtering
摘要： This report focuses on studying and investigating in detail the structural, electrical, and optical properties of p-type N-doped SnO2 (NTO) versus the deposition temperature and nitrogen content. P-type transparent conductive NTO films were deposited on quartz glass substrates using a direct current (DC) magnetron sputtering method. The substitution of oxygen by nitrogen in the SnO2 host lattice was verified using measurements such as X-ray photoelectron spectroscopy. The position of the N3? defect state in the band gap was determined using photoluminescence and ultra-violet-visible spectroscopy measurements. The data for the (110) to (101) rutile lattice planes changed, and the rutile (plane (101)) to cubic (plane (111)) SnO2 phase transition indicated the substitution of oxygen by nitrogen in the SnO2 host lattice. The best p-type conductive properties achieved were 8 × 10?2 Ω cm, 1.36 × 1019 cm?3, and 6.75 cm2 V?1 s?1 for the resistivity, hole concentration, and hole mobility, respectively, for film deposited at the optimum substrate temperature of 300 °C in a gas mixture of Ar and 50% N2.
关键词： deposition temperature,nitrogen content,p-type N-doped SnO2 thin film,X-ray photoelectron spectroscopy,DC magnetron sputtering,X-ray diffraction
更新于2025-09-19 17:15:36
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Study of expanded austenite formed in plasma nitrided AISI 316L samples, using synchrotron radiation diffraction
摘要： AISI 316L stainless steel samples nitrided at different conditions of temperature and time, showing different properties, such as nitrogen concentration (CN) and nitrided layer thickness, were studied. Expanded austenite (gN) diffraction peaks up to the (222) reflection were observed using suitable wavelength synchrotron radiation. XRD patterns were fitted by Le Bail method, using a special triclinic crystal structure (with a lattice distortion η) for gN, whose peaks were decomposed in a few subpeaks, to consider CN gradient across the nitrided layer. Our results indicate that regarding gN magnetic behavior, which was observed for the samples nitrided at 450 °C, it seems to be correlated not only to high CN (≥31at.%), but also to higher η (≥2.4°), which reaches up to 5.6°. This distortion η decreases when CN increases, consequently, with its minimum close to the surface. On the other hand, for paramagnetic samples (350 °C), η increases up to 1.4° when CN increases up to 30 at.%.
关键词： magnetic character,layer depth,AISI 316L stainless steel,expanded austenite,synchrotron diffraction,plasma nitriding
更新于2025-09-19 17:15:36
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Interaction of Zinc Oxide and Copper Oxide Nanoparticles with Chlorophyll: A Fluorescence Quenching Study
摘要： The present study aims to investigate the interactions of zinc oxide nanoparticles and copper oxide nanoparticles with the major photosynthetic pigment chlorophyll using ultraviolet-visible, steady state, and time resolved laser induced fluorescence spectroscopy. The steady state fluorescence measurements show that zinc oxide and copper oxide nanoparticles quench the fluorescence of chlorophyll in concentration-dependent manner. The Stern-Volmer plot for the chlorophyll-zinc oxide nanoparticles is linear, and the value of quenching constant has been observed to increase with temperature indicating the possibility of dynamic quenching. A decrease in the lifetime of chlorophyll with increase in the concentration of zinc oxide nanoparticles confirms the involvement of dynamic quenching in the chlorophyll–zinc oxide nanoparticle interaction. In the case of copper oxide nanoparticles, the Stern-Volmer plot deviates from linearity observed in the form of upward curvature depicting the presence of both static and dynamic quenching. In addition, the lifetime of chlorophyll decreases with increase in the concentration of copper oxide nanoparticles displaying the dominance of dynamic quenching in the chlorophyll-copper oxide nanoparticle interaction. The decrease observed in the value of binding constant with increasing temperature and negative values of change in enthalpy, entropy, and Gibb’s free energy indicates that van der Waal and hydrogen bonding are the prominent forces during the interaction of chlorophyll with both zinc oxide and copper oxide nanoparticles and that the process is spontaneous and exothermic. The interaction of zinc oxide and copper oxide nanoparticles with chlorophyll occurs through electron transfer mechanism. The obtained results are useful in understanding the sensitization processes involving chlorophyll and zinc oxide and copper oxide nanoparticles.
关键词： chlorophyll and nanoparticles,molecular interaction,ultraviolet-visible spectroscopy,laser-induced fluorescence spectroscopy,Attenuated total reflectance–Fourier transform infrared spectroscopy,steady state and time resolved fluorescence,X-ray diffraction
更新于2025-09-19 17:15:36
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Time-Domain Grating with a Periodically Driven Qutrit
摘要： Physical systems in the time domain may exhibit analogous phenomena in real space, such as time crystals, time-domain Fresnel lenses, and modulational interference in a qubit. Here, we report the experimental realization of time-domain grating using a superconducting qutrit in periodically modulated probe and control fields via two schemes: simultaneous modulation and complementary modulation. Both experimental and numerical results exhibit modulated Autler-Townes (AT) and modulation-induced diffraction (MID) effects. Theoretical results also confirm that the peak positions of the interference fringes of AT and MID effects are determined by the usual two-level relative phases, while the observed diffraction fringes, appearing only in the complementary modulation, are, however, related to the three-level relative phase. Further analysis indicates that such a single-atom time-domain diffraction originates from the correlation effect between the two time-domain gratings. Moreover, we find that the widths of the diffraction fringes are independent of the control-field power. Our results shed light on the experimental exploration of quantum coherence for modulated multilevel systems and may find promising applications in fast all-microwave switches and quantum-gate operations in the strong-driving regime.
关键词： qutrit,Autler-Townes effect,modulation,quantum coherence,time-domain grating,modulation-induced diffraction
更新于2025-09-19 17:15:36
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Coordination Polymeric Ensemble of Silver with Nitrate and 4-(Aminomethyl)benzoate: Synthesis, Crystal Structure, and Luminescence Properties
摘要： Prismatic crystals of Ag3(4-Amba)2(NO3)2 (I) and Ag(4-AmbaH)NO3 (II) are isolated from the reaction mixture of aqueous solutions of 4-aminomethylbenzoic acid (4-AmbaH) and AgNO3 at Т ≈ 70°C. The crystal structure of compound I (СIF file CCDC no. 1851513) and the luminescence properties of compounds I and II are studied. The structure of compound I contains two crystallographically nonequivalent silver atoms Ag(1) and Ag(2) with the octahedral coordination mode (with allowance for Ag···Ag contacts) with different compositions of the internal spheres of the central atoms. Owing to the contacts, the silver atoms are joined into in?nite cluster ribbons (Ag···Ag 3.06?3.27 ?). The carboxylate group of the 4-Amba anion exhibits the bridging properties and binds the silver atoms of both types. The Ag(2) atoms also contact with the oxygen atom of the NO3– ion and coordinate the NH2 group of 4-Amba. The photoluminescence spectra of compounds I and II are of the same type and show the presence of two groups of emission bands with centers at 484 and 543 nm shifted to the red range of the spectrum relative to the band of 4-AmbaH.
关键词： polynuclear silver compounds,X-ray diffraction analysis,luminescence spectra
更新于2025-09-19 17:15:36
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Photoluminescence in <i>m</i> -carborane–anthracene triads: a combined experimental and computational study
摘要： New hybrids synthesized by linking two anthracenyl units to the Ccluster atoms of a non- (4), a mono- (5) and a di-iodinated (6) m-carborane fragment through CH2 spacers, along with their full characterization, are reported. Noticeably, bonding the m-carborane fragment to the anthracene moieties produces a significant increase of more than two-fold in the intrinsic fluorescence quantum yield (fF) of the anthracene itself, with values of fF 4 60% in THF and fF 4 48% in toluene, although it does not alter the absorption and emission patterns of the fluorophore in solution. A red-shift of the emission maximum with respect to the solution is observed in the aggregate state (THF/H2O, 1 : 99 v/v), along with moderate quantum yields; compounds 4 and 5 show fF = 22 and 19%, respectively, whereas 6 has a lower value (fF = 8%). The di?erence between the fF values in the aggregate state has been attributed to the arrangement of dimers for each compound in the solid state structures. X-ray crystal structures of compounds 4 and 5 show the anthracene units to be roughly parallel, whereas such an arrangement is clearly disrupted in compound 6. Such di?erences have been analyzed by Hirshfeld surfaces, decomposed fingerprint plots for the three compounds and DFT calculations. The combined results from the supramolecular analyses and DFT studies support the idea that a less delocalized system in the case of 6 can be explained by the di?erent packing in the aggregate or solid state for this di-iodo-derivative. The observed arrangement of molecules of 6 seems to be related to a larger number of H(cid:2) (cid:2) (cid:2)I contacts, with respect to the non-iodinated or mono-iodinated compounds, 4 or 5. According to this assumption, there is a direct relationship between the structure in the solid state and the PL properties; in the m-carborane derivatives, small changes in their structures have caused variations in the photophysical properties, especially in the quantum e?ciency.
关键词： X-ray diffraction,anthracene,m-carborane,Hirshfeld surfaces,photoluminescence,DFT calculations,fluorescence quantum yield
更新于2025-09-19 17:15:36
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The Double-Slit Electron Diffraction Experiment with Aharonov-Bohm Phase Effect Revisited and the Divergence in its Asymptotic Form
摘要： In this work, we consider the experiment of diffraction and interference of electrons through a double slit added to the Aharonov-Bohm phase effect. We applied the asymptotic Fresnel functions to one term of the interference process obtaining an expression for the intensity with divergence for certain values of the flow parameter. This led us to an expression incapable of recovering the asymmetry effects of the diffraction pattern arising from the AB phase, as might be expected, since purely quantum effects cannot be classically reproduced.
关键词： Aharonov-Bohm effect,Diffraction,Path integrals,Fresnel functions
更新于2025-09-19 17:15:36