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1.
Pulsed laser ablation in a liquid phase was successfully employed to synthesize a barium molybdate (BaMoO4) nanocolloidal suspension. The nanocolloidal suspension was composed of well-dispersed and horizontally assembled BaMoO4 aggregates. The BaMoO4 aggregates showed predominantly elliptically shaped nanorods with sizes between 100 and 200 nm. The preferential elliptical growth was rationalized from the viewpoint of the intrinsic structure of BaMoO4. The optical properties of the prepared BaMoO4 colloidal nanoparticles were investigated using Raman spectroscopy, UV–vis spectroscopy and photoluminescence (PL) spectrophotometry. The optical band gap was estimated by Tauc and Menth’s law. The PL emission feature was decomposed into several individual Gaussian components, which could be interpreted by a Jahn–Teller splitting effect on the [MoO4]2- tetrahedron of the BaMoO4 colloidal nanoparticles. PACS  42.62.-b; 82.70.Dd; 78.55.Hx; 81.07.Wx  相似文献   

2.
A simple and efficient method has been established for the selective synthesis of mesoporous and nanorod CeVO4 with different precursors by sonochemical method. CeVO4 nanorod can be simply synthesized by ultrasound irradiation of Ce(NO3)3 and NH4VO3 in aqueous solution without any surfactant or template. While mesoporous CeVO4 with high specific surface area can be prepared with Ce(NO3)3, V2O5 and NaOH in the same way. Mesoporous CeVO4 has a specific surface area of 122 m2 g−1 and an average pore size of 5.2 nm; CeVO4 nanorods have a diameter of about 5 nm, and a length of 100–150 nm. The ultrasound irradiation and ammonia in the reactive solution are two key factors in the formation of such rod-like products. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and differential thermal analyses (DTA), UV/vis absorption spectroscopy and Brunauer–Emmett–Teller (BET) were applied for characterization of the as-prepared products.  相似文献   

3.
Pure monoclinic (m-) and tetragonal (t-) LaVO4 nanorods are successfully obtained via a facile oxides-hydrothermal method, in which V2O5 and La2O3 bulk powders are directly utilized as precursors without pretreatment. It is found that ethylenediamine tetraacetic disodium salt (EDTA) is a key factor for synthesizing t-LaVO4. The as-obtained products are characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED). The FTIR spectra of VO4 around 800 cm−1 are suggested as an effective auxiliary means to identify the crystal phase of LaVO4. UV–Visible spectra of LaVO4 nanomaterials are obvious blue shift compared with the bulk m-LaVO4 materials. The different photoluminescent properties of Eu3+ doped m- and t-LaVO4 are demonstrated. A dissolution–precipitation mechanism is mainly responsible for the anisotropic morphology and phase control evolution of the LaVO4 nanocrystals. The oxides-hydrothermal system is also applicable to prepare other pure LnVO4 (Ln3+: Nd3+, Y3+, Sm3+) and doped LnVO4 nanomaterials.  相似文献   

4.
We have studied the effect of lead dopant on the optical absorption, photoluminescence, and x-ray luminescence spectra, and the scintillation characteristics of CdI2 at room temperature. The crystals for the study were grown by the Stockbarger-Bridgman method. Activation of CdI2 from the melt by the compound PbI2 leads to the appearance in the absorption spectra in the near-edge region of an activator band at 395–405 nm, which is interpreted as an A band connected with electronic transitions from the 1S0 state to the 3P1 levels in the Pb2+ ion. For x-ray excitation, CdI2:Pb2+ crystals with optimal dopant concentration (∼1.0 mol%) are characterized by a light yield with maximum in the 570–580 nm region that is an order of magnitude higher than for CdI2 crystals in the 490–500 nm band. For α excitation, the radioluminescence kinetics for cadmium iodide is characterized by a very short (∼0.3 nsec) rise time and fast decay of luminescence, with τ1 ≈ 4 nsec and τ2 = 10–76 nsec. Depending on the conditions under which the crystals were obtained, the fast component fraction is 95%–99%. The crystal is characterized by a similar scintillation pulse in the case of excitation by x-ray pulses. The radioluminescence pulse shape for CdI2:Pb in the decay stage is predominantly exponential, with luminescence decay time constants τ1 ≈ 10 nsec and τ2 = 200–250 nsec. This system is characterized by low afterglow, at the level for the Bi4G3O12 scintillator. We have demonstrated the feasibility of using CdI2:Pb as a scintillator for detecting α particles. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 825–830, November–December, 2008.  相似文献   

5.
We present the characteristics of an optical parametric oscillator based on a KTP crystal, pumped with noncritical phase matching by a pulsed Ti3+:Al2O3 laser, tunable in the range 677–970 nm. Tunable generation of signal and idler waves is obtained in the ranges 1030–1390 nm and 2690–3050 nm respectively. The efficiency of conversion of the pump to the signal wave is ≈23%, which for pulses of duration ≈8 nsec ensures an energy in the range 1.0–11.5 mJ. The width of the emission spectrum for the signal wave is within the range 0.8–1.8 nm and is predominantly determined by the linewidth of the Ti3+:Al2O3 pump laser. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 351–356, May–June, 2007.  相似文献   

6.
The reverse micelle system composed of four phases of Hexamethylene/Triton-100/n-pentanol/water (containing 1 ml 0.1 M Sb3+ or 1 ml 0.1 M S2−), which ratio is 28:3:1:1, is prepared. Sb2S3 quasi-nanospheres with diameters between 160 and 240 nm are synthesized by above reverse micelle soft-template system. The result shows that the fluorescence peaks have a blue shift about 19 nm when it is excited at 219 nm, and the UV–Vis absorption peaks shift about 453 nm (2.74 eV).  相似文献   

7.
M RIAZIAN  A BAHARI 《Pramana》2012,78(2):319-331
TiO2 Nano rods can be used as dye-sensitized solar cells, various sensors and photocatalysts. These nanorods are synthesized by a hydrothermal corrosion process in NaOH solution at 200°C using TiO2 powder as the source material. In the present work, the synthesis of TiO2 nanorods in anatase, rutile and Ti7O13 phases and synthesis of TiO2 nanorods by incorporating SiO2 dopant, using the sol–gel method and alkaline corrosion are reported. The morphologies and crystal structures of the TiO2 nanorods are characterized using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) study. The obtained results show not only an aggregation structure at high calcination temperatures with spherical particles but also Ti–O–Si bonds having four-fold coordination with oxygen in SiO4 − .  相似文献   

8.
The exploration of novel synthetic methodologies that control both size and shape of functional nanostructure opens new avenues for the functional application of nanomaterials. Here, we report a new and versatile approach to synthesize SnO2 nanocrystals (rutile-type structure) using microwave-assisted hydrothermal method. Broad peaks in the X-ray diffraction spectra indicate the nanosized nature of the samples which were indexed as a pure cassiterite tetragonal phase. Chemically and physically adsorbed water was estimated by TGA data and FT-Raman spectra to account for a new broad peak around 560 cm−1 which is related to defective surface modes. In addition, the spherical-like morphology and low dispersed distribution size around 3–5 nm were investigated by HR-TEM and FE-SEM microscopies. Room temperature PL emission presents two broad bands at 438 and 764 nm, indicating the existence of different recombination centers. When the size of the nanospheres decreases, the relative intensity of 513 nm emission increases and the 393 nm one decreases. UV–Visible spectra show substantial changes in the optical absorbance of crystalline SnO2 nanoparticles while the existence of a small tail points out the presence of localized levels inside the forbidden band gap and supplies the necessary condition for the PL emission.  相似文献   

9.
Pure tetragonal and monoclinic phases BiVO4 were prepared from aqueous Bi (NO3)3 and NaVO3 solutions by a rapid microwave-assisted method that employed accurate controlling of microwave irradiation time and power. The highly crystalline phase converted irreversibly from tetragonal to monoclinic BiVO4 with gradually elongated irradiation time gradually, which is further proved by X-ray diffraction, UV–vis and Raman measurements. These variations of phase structures led to different photocatalytic properties under visible light.  相似文献   

10.
Diluted magnetic semiconductor (DMS) nanoparticles of Sn1−x Er x O2 (x = 0.0, 0.02, 0.04, and 0.1) were prepared by sol–gel method. The X-ray diffraction patterns showed SnO2 rutile structure for all samples with no impurity peaks. The decrease in crystallite size with Er concentration was confirmed from TEM measurements (from 12 to 4 nm). The UV–Visible absorption spectra of Er-doped SnO2 nanoparticles showed blue shift in band gap compared to undoped SnO2. The electron spin resonance analysis of Er-doped SnO2 nanoparticles indicate Er3+ in a rutile lattice and also decrease in intensity with Er concentration above x = 0.02. Temperature-dependent magnetization studies and the inverse susceptibility curves indicated increased antiferromagnetic interaction with Er concentration.  相似文献   

11.
A series of nanosized Bi2WO6 catalysts was synthesized using various starting materials, and they were characterized by X-ray diffractometry, transmission electron microscopy, and diffuse reflectance spectroscopy. Rhodamine-B (RhB) photodegradation in aqueous medium was employed as a probe reaction to test the photoactivity of the as-prepared samples. Dependence of the photocatalytic activities on different contents of the starting materials was examined under visible irradiation (λ > 400 nm). The sample prepared in the following conditions: reaction time 24 h, the pH of the solution 7, the Bi3+ amount in the start precipitates 5 mmol — exhibited the highest photochemical activity when the hydrothermal temperature was settled at 180°C. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 243–249, Martch–April, 2009.  相似文献   

12.
Solid and hollow YF3:Eu3+ spheres assembled by nanorods have been successfully synthesized via a facile arginine-assisted hydrothermal method and followed by a subsequent heat-treatment process. The experimental results reveal that the as-prepared YF3:Eu3+ spheres are composed of the nanorods with a diameter of 20–50 nm and a length of 200–500 nm, the morphologies of YF3:Eu3+ have been changed from solid to hollow spheres assembled by nanorods. With increase of hydrothermal temperature and time, the diameter of YF3:Eu3+ spheres can be controlled from 300 to 800 nm. The solid and hollow spheres show an intense orange red emission peak near 595 nm, corresponding to the 5D0 → 7F1 transition of Eu3+. The possible formation mechanism for the hollow spheres has been presented in detail. This amine acid-assisted method is very simple, economic and environmental friendly for organic-free solvent, which would be potentially used in synthesizing other hollow materials.  相似文献   

13.
An anti-Stokes luminescence band with λmax = 515 nm of microcrystals of solid AgCl0.95I0.05 solutions excited by a radiation flux of density 1013–1015 quanta/cm2·sec in the range 600–800 nm at 77 K was detected. It is shown that the intensity of this luminescence and the frequency of its excitation depend on the prior UV-irradiation of samples. Analysis of the stimulated-photoluminescence spectra and the anti-Stokes luminescence excitation spectra of the indicated microcrystals has shown that to the centers of anti-Stokes luminescence excitation correspond local levels in the forbidden band of the crystals. These states are apparently due to the atomic and molecular disperse silver particles that can be inherent in character or formed as a result of a low-temperature photochemical process. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 738–742, November–December, 2005.  相似文献   

14.
The laws of fluorine nuclear spin polarization in the Si/CaF2 nanostructure under optical excitation of the charge carriers in it has been considered theoretically. It has been shown that maximum values (up to 3% of the concentration of nuclei in the lattice) are attained under a high rate of optical excitation (>10−9 sec−1) when the nuclear spin diffusion process and the Auger recombination prevail. In this case, the nuclear relaxation time in an individual layer reaches 100–300 sec and the spin diffusion radius decreases to 0.3 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 397–403, May–June, 2005.  相似文献   

15.
A model of electron transfer by tunneling between trapped electron and hole centers in crystals with hydrogen bonds under the conditions of thermostimulated mobility of one carrier type in the recombination process has been developed. The proposed model describes all features in the kinetics of induced optical density relaxation observed in nonlinear optical crystals of KH2PO4 (KDP) and NH4H2PO4 (ADP) on a wide temporal scale (10−8–10 s) under pulsed irradiation. The results of model calculations have been compared with experimental data on the photoinduced transient optical absorption (TOA) in KDP and ADP crystals in the visible and UV ranges. The nature of the radiation-induced defects, which account for the TOA, and the dependence of the TOA decay kinetics on the temperature, excitation power, and other experimental conditions have been considered.  相似文献   

16.
Vacuum ultraviolet luminescence of Er3+ ions in LiYF4 and BaY2F8 crystals has been investigated. It is revealed that under excitation by 193 nm radiation from an ArF excimer laser the interconfigurational 5d–4f radiative transitions in Er3+ ions are observed. It is shown that from the LiYF4:Er crystal only the spin-forbidden luminescence (λ = 165 nm) is detected, whereas both the spin-forbidden (λ = 169 nm) and spin-allowed (λ = 160.5 nm) components are observed from the BaY2F8:Er crystal.  相似文献   

17.
We have studied photoluminescence and thermoluminescence (PL and TL) in CaGa2Se4:Eu crystals in the temperature range 77–400 K. We have established that broadband photoluminescence with maximum at 571 nm is due to intracenter transitions 4f6 5d–4f7 (8S7/2) of the Eu2+ ions. From the temperature dependence of the intensity (log I–103/T), we determined the activation energy (E a = 0.04 eV) for thermal quenching of photoluminescence. From the thermoluminescence spectra, we determined the trap depths: 0.31, 0.44, 0.53, 0.59 eV. The lifetime of the excited state 4f6 5d of the Eu2+ ions in the CaGa2Se4 crystal found from the luminescence decay kinetics is 3.8 μsec. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 112–116, January–February, 2009.  相似文献   

18.
LiCoO2 thin films were prepared by electron beam evaporation technique using LiCoO2 target with Li/Co ratio 1.1 in an oxygen partial pressure of 5 × 10−4 mbar. The films prepared at substrate temperature T s < 573 K were amorphous in nature, and the films prepared at T s > 573 K exhibited well defined (104), (101), and (003) peaks among which the (104) orientation predominates. The X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP) data revealed that the films prepared in the substrate temperature range 673–773 K are nearly stoichiometric. The grain size increases with an increase of substrate temperature. The Co–eg absorption bands, are empty and their peak position lies at around 1.7 eV above the top to the Co–t2g bands. The fundamental absorption edge was observed at 2.32 eV. The films annealed at 1,023 K in a controlled oxygen environment exhibit (104) out plane texture with large grains. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006  相似文献   

19.
The third order nonlinear optical properties of 4-methoxy chalcone and its derivatives have been investigated using a single-beam Z-scan technique with nanosecond laser pulses at 532 nm. The 4-methoxy chalcone and its derivatives are donor–acceptor–acceptor (D–A–A) and donor–acceptor–donor (D–A–D) type intramolecular charge transfer molecules. The nonlinear response in these molecules was found to increase with increase in (a) the electron acceptor strength in D–A–A type and (b) the donor strength of the substituted group in D–A–D type molecules. The χ(3) value in these molecules is found to be of the order of 10-13 esu. The observed increase in the third order nonlinearity in these molecules clearly indicates the electronic origin. The compounds exhibit good optical limiting at 532 nm. The best optical limiting behavior was observed with the molecule substituted by a strong electron donor. PACS 42.65.An; 42.70.Nq  相似文献   

20.
By controlling the oxygen pressure, single-phase CuO and Cu2O thin films have been obtained on quartz substrates using a pulsed laser deposition technique. The structure properties and linear optical absorption of the films were characterized by X-ray diffraction and UV–VIS spectroscopy. By performing z-scan measurements using a femtosecond laser (800 nm, 50 fs), the real and imaginary parts of the third-order nonlinear susceptibility, Re χ (3) and Im χ (3), of the films were determined. Both CuO and Cu2O films exhibited large optical nonlinearities, which is comparable to those in some representative semiconductor films such as ZnO and GaN films using femtosecond laser excitation. Compared with Cu2O films, the CuO films showed larger third-order nonlinear optical effects under off-resonance excitation. Furthermore, the mechanisms of the optical nonlinearities in CuO and Cu2O films are explained in the main text. It was suggested that the reasons of the difference in their nonlinear refractive effects may be related to the different electronic structure in CuO and Cu2O materials.  相似文献   

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