共查询到20条相似文献,搜索用时 31 毫秒
1.
Leaf‐like copper oxide nanocrystals synthesized by a gas‐liquid diffusion method at room temperature
The leaf‐like copper oxide (CuO) nanocrystals have been synthesized by a gas‐liquid diffusion method in pure aqueous solution at room temperature. The structure, morphologies and related properties of the as‐prepared crystals were characterized with X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), selected area electron diffraction (SAED) and thermogravimetric analysis (TG). The influence of copper concentration was investigated, which plays an important role in the formation of nanostructured CuO crystals. Only when the copper concentration was low enough (0.005 M) that the leaf‐like CuO could be obtained directly. Additionally, a growth mechanism of CuO was also proposed based on the observed results. 相似文献
2.
Yongkui Cui Fengping Wang M. Zubair Iqbal Yan Li Arbab Mohammad Toufiq Ziya Wang Zhiyuan Wang Shujaat Ali 《Crystal Research and Technology》2015,50(3):210-214
Self‐assembling nanoflakes‐based crossed architectures of stannous oxide (SnO) were successfully synthesized via template‐free hydrothermal growth method by using SnCl2·2H2O and KOH as precursors. Crystal structures, morphology, chemical composition and optical properties were examined by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis, and Raman spectroscopy, respectively. The results indicate that the as‐synthesized product belongs to tetragonal phase SnO with crossed morphology self‐assembled by nanoflakes. Furthermore, UV‐vis spectrophotometry was used to determine optical band gap of the SnO nanostructures and the direct band gap of 2.90 eV was obtained. The photocatalysis of the product has been evaluated with methyl orange and the high degradation ratio of 87% is obtained in 240 minutes under the measuring condition which is attributed to the wide band gap and large specific surface area of the nanoflakes‐based crossed SnO architectures. A possible growth mechanism is proposed in the end. 相似文献
3.
ZnO thin films with different Mg doping contents (0%, 3%, 5%, 8%, 10%, respectively) were prepared on quartz glass substrates by a modified Pechini method. XRD patterns reveal that all the thin films possess a polycrystalline hexagonal wurtzite structure. The peak position of (002) plane for Mg‐doped ZnO thin films shifts toward higher angle due to the Mg doping. The crystallite size calculated by Debey‐Scherrer formula is in the range of 32.95–48.92 nm. The SEM images show that Mg‐doped ZnO thin films are composed of dense nanoparticles, and the thickness of Mg‐doped ZnO thin films with Mg doped at 8% is around 140 nm. The transmittance spectra indicate that Mg doping can increase the optical bandgap of ZnO thin films. The band gap is tailored from 3.36 eV to 3.66 eV by changing Mg doping concentration between 3% and 10%. The photoluminescence spectra show that the ultraviolet emission peak of Mg‐doped ZnO thin films shifts toward lower wavelength as Mg doping content increases from 3% to 8%. The green emission peak of Mg‐doped ZnO thin films with Mg doping contents were 3%, 8%, and 10% is attributed to the oxygen vacancies or donor‐acceptor pair. These results prove that Mg‐doped ZnO thin films based on a modified Pechini method have the potential applications in the optoelectronic devices. 相似文献
4.
5.
CdO nanowires were produced by calcination process using Cd(OH)2nanowires as precursors. The Cd(OH)2 nanowires were synthesized via arc discharge method submerged in de‐ionized water. Transmission electron microscopy (TEM) analysis of the as‐synthesized Cd(OH)2 nanowires revealed that nanowire morphology was abundant form with the diameters range from 5 to 40 nm. In addition to the nanowire morphology, Cd(OH)2 nanospheres and hexagonal shaped nanoparticles were also displayed. The Cd(OH)2 nanostructures were used as precursors to produce CdO nanowires and calcinated in air at 400 °C for four hours. After calcination, the structural, morphological and optical properties of the as‐synthesized CdO nanowires were characterized by means of TEM, selected area electron diffraction (SAED), X‐ray diffraction (XRD) and UV‐vis spectroscopy. The XRD and SAED techniques showed that the as‐synthesized Cd(OH)2 nanostructures could be transformed into CdO nanostructures after the calcination process. TEM results revealed that the as‐synthesized CdO nanowires were 5–30 nm in diameter and shorter than corresponding Cd(OH)2 nanowires. In addition, the diameters of the spherical or irregular CdO nanoparticles ranged from 20 nm to 50 nm. UV‐vis spectroscopy analysis was showed that the direct gap of the CdO nanowires were found to be 2.60 eV which is slightly higher than the earlier reported values of the bulk CdO for direct band gaps (2.3 eV) due to quantum size effect. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Tingting Jiang Junhan Kong Yongqian Wang Dawei Meng Dagui Wang Meihua Yu 《Crystal Research and Technology》2016,51(1):58-64
Mn‐doped CuO nanosheets were prepared through a hydrothermal method to enhance their photocatalytic property. The structural and morphological features were monitored by using X‐Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS). UV‐vis absorption spectra showed the enhance absorption performance both in UV and visible light region. The band gaps were also calculate and the minimum value was 1.25 eV. The photocatalytic activity was investigated by the degradation of methylene blue (MB), which indicated that the photoactivity of samples depended on the amount of Mn2+ incorporated into the CuO lattice. The improved performance of photocatalysts can be attributed to enhanced light absorption and lower electron‐hole recombination. 相似文献
7.
Zhen Li Yaoguo Fang Liwei Peng Dengyu Pan Minghong Wu 《Crystal Research and Technology》2010,45(10):1083-1086
Rose‐like ZnO nanostructures were prepared by a low‐temperature solution route with assistance of ethylenediaminetetraacetic acid disodium (EDTA‐2Na). The morphology of ZnO nanostructures was found to change from nanowire arrays to rose‐ and tower‐like architectures with increasing the molar ratio of EDTA‐2Na/Zn2+. Also, the shape evolution of ZnO nanostructures with time was observed from flat nanosheets to wrinkled nanosheets and to rose‐like nanostructures. EDTA‐2Na as a strong complexing agent was found to play a key role in the shape evolution. Photoluminescence spectra show that the rose‐like ZnO architectures have more defects than the nanowire arrays. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Shinho Cho 《Crystal Research and Technology》2016,51(12):718-722
Sm‐doped CaNb2O6 (CaNb2O6:Sm) phosphor thin films were prepared by radio‐frequency magnetron sputtering on sapphire substrates. The thin films were grown at several growth temperatures and subsequently annealed at 800 °C in air. The crystallinity, surface morphology, optical transmittance, and photoluminescence of the thin films were investigated by X‐ray diffraction, scanning electron microscopy, ultraviolet‐visible spectrophotometry, and fluorescence spectrophotometry, respectively. All of the thin films showed a main red emission radiated by the transition from the 4G5/2 excited state to the 6H9/2 ground state of the Sm3+ ions and several weak bands under ultraviolet excitation with a 279 nm wavelength. The optimum growth temperature for depositing the high‐quality CaNb2O6:Sm thin films, which was determined from the luminescence intensity, was found to be 400 °C, where the thin film exhibited an orthorhombic structure with a thickness of 370 nm, an average grain size of 220 nm, a band gap energy of 3.99 eV, and an average optical transmittance of 85.9%. These results indicate that the growth temperature plays an important role in controlling the emission intensity and optical band gap energy of CaNb2O6:Sm thin films. 相似文献
9.
S. S. Hussaini N. R. Dhumane G. Rabbani P. Karmuse V. G. Dongre M. D. Shirsat 《Crystal Research and Technology》2007,42(11):1110-1116
Non linear optical (NLO) materials have acquired new significance with the advent of a large number of devices utilizing solid‐state laser sources. Several NLO materials have been used for this kind of technological applications. The Potassium di‐hydrogen phosphate (KDP) one of NLO material having superior non linear optical properties has been exploited for variety of applications. In the present investigation we have grown KDP crystals from aqous solution with thiourea, an organic non linear optical material. We could enhance the SHG efficiency of thiourea doped KDP crystal. It was 1.99 times more that of pure KDP. We observed more enhancements in nonlinearity for low concentration of thiourea.The crystal structure and cell parameters of grown crystal were determined from Powder XRD.The incorporation of thiourea in the grown crystals was qualitatively analyzed from FT‐IR study. The absorption spectra of pure and thiourea doped KDP crystal reveal that thiourea doped KDP crystals would be a better nonlinear optical (NLO) material for second harmonic generation (SHG) than pure KDP. The thermal decomposition and weight loss of pure and thiourea doped KDP crystal was observed by thermogravimetric (TGA) analysis and Differential Scanning Calorimetry (DSC). The high frequency dielectric study of pure KDP crystal, thiourea doped KDP crystals and organic additive thiourea was carried out using X‐band at frequency 8GHZ and 12GHZ by transmission line wave guide method. We observed low dielectric constant of thiourea doped KDP crystal when it is doped with 2mole% of thiourea. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
10.
Single‐crystal ZnO torch‐like nanostructure arrays were synthesized using a simple two‐step pressure controlled thermal evaporation method without any catalyst. The nanostructures had a hierarchical morphology, with well‐hexagonal faceted holders and needle‐like flames on them. The diameter of each single flame was about 20–40nm at the base and 10nm at the tip. Both the holders and flames were found to grow along the [0001] direction. The morphology of the structures could be effectively controlled by varying the growth temperature and vacuum pressure. The experimental results and analysis provided easy strategies to control the morphology of nanostructures and also enhanced the understanding of the growth mechanism. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
Baodan Liu Tao Hu Zaien Wang Lizhao Liu Fuwen Qin Nan Huang Xin Jiang 《Crystal Research and Technology》2012,47(2):207-212
In this work, P‐doped GaN nanowires were synthesized in a co‐deposition CVD process and the effects of P‐doping on the microstructure and cathodoluminescence (CL) of GaN nanowires were studied in details. SEM observation and CL measurments demonstrated that P‐doping has led to a rough morphology evolution and a depression of the band‐gap emission of GaN nanowires, whereas the visible emission of GaN nanowires was obviously enhanced. Finally, the corresponding morphology transition and optical properties of GaN nanowires with P‐doping were discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
D. D. Wang J. H. Yang L. L. Yang Y. J. Zhang J. H. Lang M. Gao 《Crystal Research and Technology》2008,43(10):1041-1045
ZnO nanostructures were grown on Au‐coated Si (100) substrates by carbonthermal reduction method with the help of Ar at the beginning of growth. The structural and optical properties of ZnO nanostructures strongly depended on the supply time of Ar. When the given time of Ar gas current was 90s, sample was ZnO nanowires with hexagonal morphology. The Raman spectroscopy revealed the low level of oxygen vacancies and Zn interstitials in samples. Room temperature photoluminescence (PL) spectra exhibited the intensity of green emission increased on the condition of rich oxygen (decrease given time of Ar) and the nanowire had strongest intensity of UV emission compared with other nanostructures. Green emission is ascribed to the electron transition from the bottom of the conduction band to the antisite defect OZn level. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
An‐Qi Zhang Lu Zhang Li Sui Dong‐Jin Qian Meng Chen 《Crystal Research and Technology》2013,48(11):947-955
Flower‐like ZnO nanostructures assembled by nanorods with bimodal size distribution have been synthesized by a solvothermal process in NaOH‐Et system. Various effects of the solvothermal parameters and assistant additives on the morphologies of ZnO nanostructures have been investigated. The directing effect of chloride ions have been observed in the formation of highly symmetrical 3D ZnO nanostructures. A possible mechanism has been proposed to explain the formation of ZnO nanoflowers in NaOH‐Et system. A strong near‐UV emission band centered at around 396 nm is observed in the photoluminescence spectrum of flower‐like ZnO nanostructures, indicating of their high crystal quality. 相似文献
14.
Nanocrystalline 1%, 2% and 4% Cobalt-doped TiO2 were prepared by sol–gel technique, followed by freeze-drying treatment at ?30 °C temperature for 12 h. The obtained gels were thermally treated at 200, 400, 600 and 800 °C. X-ray Powder Diffraction (XRD), Scanning Electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDAX) were used to study its structural properties. The XRD pattern shows the coexistence of anatase phase and minor brookite phase. UV–vis Spectroscopy and Photoluminescence (PL) were used to study its optical properties. Optical band gap was calculated with the incorporation of different concentrations of cobalt. UV–visible spectroscopy shows variation in band gap for the sample treated at different temperatures for same concentration. All Cobalt doped TiO2 nanostructures show an appearance of Red shift relative to the bulk TiO2. The determination of magnetic properties was also carried out by Gouy balance method. 相似文献
15.
WS2由于其优异的物理和光电性质引起了广泛关注。本研究基于第一性原理计算方法,探索了本征单层WS2及不同浓度W原子替位钇(Y)掺杂WS2的电子结构和光学特性。结果表明本征单层WS2为带隙1.814 eV的直接带隙半导体。进行4%浓度(原子数分数)的Y原子掺杂后,带隙减小为1.508 eV,依旧保持着直接带隙的特性,随着Y掺杂浓度的不断增大,掺杂WS2带隙进一步减小,当浓度达到25%时,能带结构转变为0.658 eV的间接带隙,WS2表现出磁性。适量浓度的掺杂可以提高材料的导电性能,且掺杂浓度增大时,体系依旧保持着透明性并且在红外光和可见光区对光子的吸收能力、材料的介电性能都有着显著提高。本文为WS2二维材料相关光电器件的研究提供了理论依据。 相似文献
16.
Nalan iek Bezir Atilla Evcin Refik Kayal Murivet Kakc
zen Aye Oktay 《Crystal Research and Technology》2016,51(1):65-73
Pure and 1, 2, and 3 wt% Ag doped TiO2 nanofibers were prepared by electrospinning method at different applied voltages and heights at a constant flow rate of 2 mL/h. Characterization of the prepared samples was performed by x‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microcopy (AFM),four point probe method (FPPM), the differential scanning calorimetry/the thermal gravimetric analysis (DSC/TGA), ultraviolet/visible spectrometry (UV/VIS), and energy dispersive X‐ray spectrometer (EDX). It was found that the thermally untreated pure TiO2 nanofibers and thermally treated (at 500 °C) samples have the crystalline phase of anatase (A), and mixed anatase and rutile (A+R) phases, respectively. It was also observed that the content of the silver does not affect the crystal structure, but plays strengthening role in the rutile structure. SEM micrographs showed that all fabricated nanofiber samples have uniform morphologies, and AFM measurements indicated that the nanofibers were formed in three‐dimensional coils. The band gap values of the nanofiber samples obtained from UV/VIS measurements revealed that band gap values of the nanofiber samples decrease while the diameter of the nanofiber increases. 相似文献
17.
采用第一性原理计算方法,对本征Mn4Si7以及P和As掺杂的Mn4Si7的电子结构和光学性质进行计算解析。计算结果表明本征Mn4Si7是带隙值为0.810 eV的间接带隙半导体材料,P掺杂Mn4Si7的带隙值增大为0.839 eV,As掺杂Mn4Si7的带隙值减小为0.752 eV。掺杂使得Mn4Si7的能带结构和态密度向低能方向移动,同时使得介电函数的实数部分在低能区明显增大,虚数部分几乎全部区域增加且8 eV以后趋向于零。此外掺杂还增加了高能区的消光系数、吸收系数、反射系数以及光电导率,明显改善了Mn4Si7的光学性质。 相似文献
18.
Al‐doped ZnO nanoparticle thin films were prepared on glass substrate at the optimum temperature of (410±10) °C by spray pyrolysis technique using zinc nitrate as a precursor solution and aluminium chloride as a dopant. The dopant concentration (Al/Zn at%) was varied from 0 to 2 at%. Structural analysis of the films shows that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure. The films exhibit variation in peak intensities corresponding to (100), (002) and (101) reflection planes on Al‐doping. The crystallite size calculated by Scherrer formula has been found to be in the range of 35‐65 nm. The optical absorption study shows that the optical band gap in the Al‐doped films varies in the range of 3.11 – 3.22 eV. The width of localized states in the band gap estimated by the Urbach tail analysis has been found to be minimum in case of the 1 at% Al‐doped zinc oxide thin film. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
针对AgSnO2触头材料存在的不足,采用基于密度泛函理论的第一性原理对SnO2、Ni单掺杂、Mo单掺杂以及Ni-Mo共掺杂SnO2材料进行了电性能与力学性质的研究,计算了各体系的形成能、能带结构、态密度、弹性常数等各项参数。结果表明,掺杂后的材料可以稳定存在,且仍为直接带隙半导体材料。与未掺杂相比,掺杂后体系的能带结构带隙值减少,其中Ni-Mo共掺杂时的带隙值最小,载流子跃迁所需能量减少,极大地改善了SnO2的电性能;由弹性常数计算了剪切模量、体积模量、硬度等参数,其中Ni-Mo共掺杂时的硬度大幅降低,韧性增强,有利于AgSnO2触头材料后续加工成型,且其普适弹性各向异性指数最小,不易形成裂纹。综合各项因素,Ni-Mo共掺杂能够很好地改善SnO2的性能,为触头材料的发展提供了理论指导。 相似文献
20.
L. Kumari W. Z. Li C. H. Vannoy R. M. Leblanc D. Z. Wang 《Crystal Research and Technology》2009,44(5):495-499
Vertically aligned and well interconnected NiO nanowalls with thin nanodiscs of cubic NiO as the in situ formed building blocks were fabricated via a template‐free approach. The alkaline solution of ammonium hydroxide was used as a reductant and Ni foil as both source material and substrate for the nanowall synthesis. Surface morphology analysis confirmed the formation of 15 nm thick and 0.2–1.5 μm wide nanowalls. The nanowalls had the crystal structure of cubic NiO with their growth plane along the [111] direction. An optical band gap of about 3.8 eV for the NiO nanowalls was obtained from the optical absorption measurement. NiO nanowalls exhibited a broad UV emission band centered at around 390 nm. This simple, but efficient synthesis technique can facilitate the growth of well aligned 2D nanostructures with large surface area for possible applications in nanoscale devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献