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1.
V-doped ZnO nanoparticles were synthesized by heating metal acetates in organic solvent. All synthesized samples were annealed in air and reducing gas atmosphere at 600 °C for 8 h. The XRD patterns of both samples annealed in air and reducing atmosphere indicate that samples have polycrystalline wurtzite structure with increase in lattice constant with increase in V-doping. The particle sizes were calculated by using Scherrer's equation which lies in the range of 25-30 nm. The SEM images show that particles annealed in air and under reducing environment are spherical in nature. The EDX results reveal that samples contain V, Zn, and O contents only. The TPR results indicate that the system contains isolated VOx, ZnOx and bimetallic Zn: V (Ox) sites and indication of electronically excited bimetal sites. There is no signature of ferromagnetism in all samples annealed in air while room temperature ferromagnetism has been observed only under reducing atmosphere annealing. There is monotonically increase in saturation magnetization with V-doping concentration. UV-vis spectroscopy study shows that there is a linear increase in band gap energy with increase in V-doping, a direct evidence of change in magnetic properties due to V-doping and under reducing environment. 相似文献
2.
Abdub G. Ali Francis B. Dejene Hendrik C. Swart 《Central European Journal of Physics》2012,10(2):478-484
Un-doped and Mn-doped ZnO nanoparticles were successfully synthesized in an ethanolic solution by using a sol-gel method.
Material properties of the samples dependence on preparation conditions and Mn concentrations were investigated while other
parameters were controlled to ensure reproducibility. It was observed that the structural properties, particle size, band
gap, photoluminescence intensity and wavelength of maximum intensity were influenced by the amount of Mn ions present in the
precursor. The XRD spectra for ZnO nanoparticles show the entire peaks corresponding to the various planes of wurtzite ZnO,
indicating a single phase. The diffraction peaks of doped samples are slightly shifted to lower angles with an increase in
the Mn ion concentration, signifying the expansion of the lattice constants and increase in the band gap of ZnO. All the samples
show the absorption in the visible region. The absorbance spectra show that the excitonic absorption peak shifts towards the
lower wavelength side with the Mn-doped ZnO nanoparticles. The PL spectra of undoped ZnO consist of UV emission at 388 nm
and broad visible emission at 560 nm with varying relative peak intensities. The doping of ZnO with Mn quenches significantly
the green emission while UV luminescence is slightly affected. 相似文献
3.
H. Capellmann 《Zeitschrift für Physik B Condensed Matter》1977,26(1):59-62
A strong coupling theory involving excitonic instabilities and lattice distortions is developed. It is argued that this driving mechanism applies to structural transitions in a number of transition metal oxides and to the superstructures of semiconductor surfaces and layered transition metal compounds. 相似文献
4.
Sonal Singhal Japinder KaurTsering Namgyal Rimi Sharma 《Physica B: Condensed Matter》2012,407(8):1223-1226
Pure and Cu doped ZnO nanopowders (5, 10, 15, 20, 25 and 30 at% Cu) have been synthesized using co-precipitation method. Transmission Electron Microscopic analysis has shown the morphology of ZnO nanopowders to be quasi-spherical. Powder X-ray Diffraction studies have revealed the systematic doping of Cu into the ZnO lattice up to 10% Cu, though the peaks corresponding to CuO in 10% Cu are negligibly very small. Beyond this level, there was segregation of a secondary phase corresponding to the formation of CuO. Fourier Transform Infrared spectra have shown a broad absorption band at ∼490 cm−1 for all the samples, which corresponds to the stretching vibration of Zn-O bond. DC electrical resistivity has been found to decrease with increasing Cu content. The activation energy has also been observed to decrease with copper doping i.e. from ∼0.67 eV for pure ZnO to ∼0.41 eV for 30 at% Cu doped ZnO. 相似文献
5.
Prashant K. Sharma Ranu K. Dutta Avinash C. Pandey 《Journal of magnetism and magnetic materials》2009,321(20):3457-3461
The ZnO:Ni2+ nanoparticles of mean size 2-12 nm were synthesized at room temperature by the simple co-precipitation method. The crystallite structure, morphology and size were determined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The wurtzite structure of ZnO gradually degrades with the increasing Ni doping concentration and an additional NiO-associated diffraction peak was observed above 15% of Ni2+ doping. The change in magnetic behavior of the nanoparticles of ZnO with varying Ni2+ doping concentration was investigated using a vibrating sample magnetometer (VSM). Initially, these nanoparticles showed strong ferromagnetic behavior, however, at higher doping percentage of Ni2+, the ferromagnetic behavior was suppressed and paramagnetic nature was observed. The enhanced antiferromagnetic interaction between neighboring Ni-Ni ions suppressed the ferromagnetism at higher doping concentrations of Ni2+. 相似文献
6.
Prashant K. Sharma Ranu K. Dutta Samar Layek 《Journal of magnetism and magnetic materials》2009,321(17):2587-2591
The ZnO:Fe nanoparticles of mean size 3-10 nm were synthesized at room temperature by simple co-precipitation method. The crystallite structure, morphology and size estimation were performed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM). The wurtzite structure of ZnO gradually degrades with the increasing Fe doping concentration. The magnetic behavior of the nanoparticles of ZnO with varying Fe doping concentration was investigated using a vibrating sample magnetometer (VSM). Initially these nanoparticles showed strong ferromagnetic behavior, however at higher doping percentage of Fe, the ferromagnetic behavior was suppressed and paramagnetic nature was observed. The enhanced antiferromagnetic interaction between neighboring Fe-Fe ions suppressed the ferromagnetism at higher doping concentrations of Fe. Room-temperature Mössbauer spectroscopy investigation showed Fe3+ nature of the iron atom in ZnO matrix. 相似文献
7.
Nanocrystalline ZnO, ZnO-Zn, and ZnO-Zn-Fe powders with a specific surface area up to 45 m2/g and a low Fe concentration (no more than 0.619 wt %) have been prepared using pulsed electron beam evaporation. The crystal structure, morphology, and size of the nanoparticles have been determined using X-ray powder diffraction, transmission electron microscopy, and scanning electron microscopy. It has been found that the magnetization of the ZnO-Zn and ZnO-Zn-Fe nanopowders increases after annealing in an oxidizing atmosphere. An elemental mapping with energy-dispersive X-ray analysis has revealed the absence of Fe clusters in the ZnO-Zn-Fe sample. A thermal analysis has demonstrated that dopants of Fe in ZnO increase the temperature of complete oxidation of Zn nanoparticles to 600°C, which creates favorable conditions for an increase in the density of structural defects upon oxidation of Zn to ZnO. The absence of clusters and secondary magnetic Fe phases in pure and doped ZnO-based nanopowders indicates the intrinsic nature of ferromagnetism at room temperature in nanopowders prepared by pulsed electron beam evaporation. 相似文献
8.
I.A. Buyanova X.J. Wang W.M. Wang C.W. Tu W.M. Chen 《Superlattices and Microstructures》2009,45(4-5):413-420
Effects of Ga incorporation on electrical, structural and optical properties of ZnO epilayers are systematically studied by employing structural and optical characterization techniques combined with electrical and secondary ion mass spectrometry measurements. A non-monotonous dependence of free electron concentrations on Ga content is observed and is attributed to defect formation and phase separation. The former process is found to dominate for Ga concentrations of around 2–3×1020 cm?3. The corresponding defects are suggested to be responsible for a broad red emission, which peaks at around 1.8 eV at 4 K. Characteristic properties of this emission are well accounted for by assuming intracenter transitions at a deep center, of which the associated Huang–Rhys factor and mean phonon energy are determined. For higher Ga doping levels, the phase separation is found to be significant. It is suggested that under these conditions only a minor fraction of incorporated Ga atoms form shallow donors, which leads to the observed dramatic decrease of carrier concentration. 相似文献
9.
T. Pandiyarajan R. Udayabhaskar B. Karthikeyan 《Applied Physics A: Materials Science & Processing》2012,107(2):411-419
In this report, Raman and Fourier Transform Infrared (FTIR) measurements were carried out to study the phonon modes of pure
and Fe doped ZnO nanoparticles. The nanoparticles were prepared by sol–gel technique at room temperature. The X-ray diffraction
measurements reveal that the nanoparticles are in hexagonal wurtzite structure and doping makes the shrinkage of the lattice
parameters, whereas there is no alteration in the unit cell. Raman measurements show both E2lowE_{2}^{\mathrm{low}} and E2HighE_{2}^{\mathrm{High}} optical phonon mode is shifted towards lower wave number with Fe incorporation and explained on the basis of force constant
variation, stress measurements, respectively. In addition, Fe related local vibrational modes (LVM) were observed for higher
concentration of Fe doping. FTIR spectra reveal a band at 444 cm−1 which is specific to E
1 (TO) mode; a red-shift of this mode in Fe doped samples and some surface phonon modes were observed. Furthermore, the observation
of additional IR modes, which is considered to have an origin related to Fe dopant in the ZnO nanostructures, is also reported.
These additional mode features can be regarded as an indicator for the incorporation of Fe ions into the lattice position
of the ZnO nanostructures. 相似文献
10.
Anees A. Ansari J. Labis M. Alam Shahid M. Ramay N. Ahmad Asif Mahmood 《Phase Transitions》2016,89(3):261-272
Cobalt-doped ceria nanoparticles were synthesized using the polyol method under co-precipitation hydrolysis. The structural, morphological, optical and redox properties were observed to investigate the influence of different concentration of cobalt ion doping on the prepared CeO2 nanomaterials in terms of X-ray diffraction, field-emission transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, UV/vis absorption spectroscopy and temperature program reduction techniques. The optical band gap energy was calculated from the optical absorption spectra for doped ceria nanoparticles, which have been found to be 2.68, 2.77, and 2.82 eV for the 2, 4, and 7 mol% Co ion-doped CeO2 nanoparticles, respectively. As observed, the band gap energies increases as the doping Co ion concentrations increased, which could be due to significant increased oxygen vacancies with Co doping. The synergistic interaction between Co and CeO2 was the main factor responsible for high catalytic activity of cobalt-doped CeO2 model catalysts. 相似文献
11.
Synthesis of Pr-doped ZnO nanoparticles: Their structural,optical, and photocatalytic properties
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Undoped and praseodymium-doped zinc oxide(Pr-doped ZnO)(with 2.0-mol%–6.0-mol% Pr) nanoparticles as sunlight-driven photocatalysts are synthesized by means of co-precipitation with nitrates followed by thermal annealing.The structure, morphology, and chemical bonding of the photocatalysts are studied by x-ray diffraction(XRD), scanning electron microscopy(SEM) with energy dispersive x-ray emission spectroscopy(EDS), x-ray photoelectron spectroscopy(XPS), and Fourier transform infrared spectroscopy(FTIR), respectively. The optical properties are studied by photoluminescence(PL) and UV-vis diffuse reflectance spectroscopy(UV-vis DRS). We find that Pr doping does not change the crystallinity of ZnO; but it reduces the bandgap slightly, and restrains the recombination of the photogenerated electron–hole pairs. The photocatalytic performance of the photocatalysts is investigated by the photodegradation reaction of 10-mg/L rhodamine B(RhB) solution under simulated sunlight irradiation, showing a degradation rate of 93.75% in ZnO doped with6.0-mol% Pr. 相似文献
12.
D. Tainoff B. Masenelli A. Belsky D. Amans N. Fedorov 《Journal of luminescence》2009,129(12):1798-1801
This study deals with the influence of the excitation (UV-lamp, UV-laser and VUV synchrotron radiation) on the 3.31 eV band of ZnO microcrystals and of variously treated nanoparticles. The nanoparticles are synthesized in ultra high vacuum condition and their stoichiometry and crystallinity can be controlled. This provides an efficient way to probe the influence of these factors on the excitonic emission. The energy and intensity of the excitation have a strong influence on the excitonic luminescence and particularly on the 3.31 eV emission band. The result of these experiments are used to probe the origins of this band which is found to be not linked to any surface phenomena. Indeed, the only way to fully explain our results is to consider that the 3.31 eV band involve the superposition of two emissions features: the first due to acceptor defects and the other originates form the LO phononic repliqua of the free exciton. 相似文献
13.
Changzhen Liu Dawei Meng Haixia Pang Xiuling Wu Jing Xie Xiaohong Yu Long Chen Xiaoyang Liu 《Journal of magnetism and magnetic materials》2012
Zn1–xFexO (x=0–0.05) nanoparticles were synthesized without a catalyst by a two-step method. Fe was doped into ZnO by a source of metallic Fe sheets in a solid–liquid system at 80 °C, and the Zn1−xFexO nanoparticles were obtained by annealing at 300 °C. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy were used to characterize the structural properties of the as-grown Zn1−xFexO. The optical properties were determined by Infrared and Ultraviolet–visible spectroscopy. The results confirm that the crystallinity of the ZnO is deteriorated due to Fe-doping. XPS results show that there is a mixture of Fe0+ and the Fe3+ in the representative Zn0.95Fe0.05O sample. The optical band gap of Zn1−xFexO is enhanced with increasing of Fe-doping. Room temperature ferromagnetism was observed in all the Fe-doped ZnO samples. 相似文献
14.
Zinc oxide nanoparticles were synthesized using chemical method in alcohol base. During synthesis three capping agents, i.e. triethanolamine (TEA), oleic acid and thioglycerol, were used and the effect of concentrations was analyzed for their effectiveness in limiting the particle growth. Thermal stability of ZnO nanoparticles prepared using TEA, oleic acid and thioglycerol capping agents, was studied using thermogravimetric analyzer (TGA). ZnO nanoparticles capped with TEA showed maximum weight loss. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for structural and morphological characterization of ZnO nanoparticles. Particle size was evaluated using effective mass approximation method from UV-vis spectroscopy and Scherrer's formula from XRD patterns. XRD analysis revealed single crystal ZnO nanoparticles of size 12-20 nm in case of TEA capping. TEA, oleic acid and thioglycerol capped synthesized ZnO nanoparticles were investigated at room temperature photoluminescence for three excitation wavelengths i.e. 304, 322 and 325 nm, showing strong peaks at about 471 nm when excited at 322 and 325 nm whereas strong peak was observed at 411 for 304 nm excitation. 相似文献
15.
We present a comprehensive analysis of the Raman spectra of pure and zirconium‐doped anatase TiO2 nanoparticles. To account for the wavenumber shifts of the Eg(ν6) mode as a function of particle size (L) and dopant concentration (x), a modification of the standard phonon confinement model (PCM) is introduced, which takes into account the contribution of surface stress by means of the Laplace–Young equation. Together with X‐ray diffraction (XRD) and transmission electron microscopy data, our analysis shows that the surface stress contribution to the observed blue shift of the Raman wavenumber is of the same magnitude as the spatial phonon confinement effect. Annealing experiments show that Zr‐doped nanoparticles exhibit retarded grain growth and delayed anatase‐to‐rutile phase transition by up to 200 K compared to pure anatase TiO2. XRD shows that Zr doping leads to a unit cell expansion of the anatase structure. Applying the modified PCM to the x‐dependent variations of the Eg(ν6) Raman mode, the mode‐Grüneisen parameter is found to increase abruptly at x > 0.07 with a concomitant mode softening. This coincides with the x range over which the Zr cations are reported to be displaced from their position in the tetrahedral lattice, and where Zr precipitation occurs upon annealing. The results have implications for the interpretation of Raman spectra of ionic metal oxide nanoparticles and how these are modified upon cation doping. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
16.
Well-dispersed undoped and Mg-doped ZnO nanoparticles with different doping concentrations at various annealing temperatures are synthesized using basic chemical solution method without any capping agent. To understand the effect of Mg doping and heat treatment on the structure and optical response of the prepared nanoparticles, the samples are characterized using X-ray diffraction (XRD), energy-dispersive X-ray (EDX), UV–Vis optical absorption, photoluminescence (PL), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. The UV–Vis absorbance and PL emission show a blue shift with increasing Mg doping concentration with respect to bulk value. UV–Vis spectroscopy is also used to calculate the band-gap energy of nanoparticles. X-ray diffraction results clearly show that the Mg-doped nanoparticles have hexagonal phase similar to ZnO nanoparticles. TEM image as well as XRD study confirm the estimated average size of the samples to be between 6 and 12 nm. Furthermore, it is seen that there was an increase in the grain size of the particles when the annealing temperature is increased. 相似文献
17.
A serial of FePtNi nanoparticles were investigated on their crystal structure and magnetic properties. The FePtNi nanoparticles were synthesized simultaneously by the reduction of iron (III) acetylacetonate, platinum (II) acetylacetonate and nickel (II) acetylacetonate with 1,2-hexadecanediol as the reducing agent. The X-ray diffraction patterns indicate that the addition of 8, 12, 17 at% Ni in FePt nanoparticles suppressed the transformation of the particles from disorder face-centered cubic to order face-centered tetragonal L10-phase under annealing treatment. However, further increasing Ni contents to 21 at%, the nanoparticle transformed to L12 phase. Doping of Ni into the FePt compound system may decrease coercivity and crystal anisotropy energy. A maximum coercivity of 7 KOe at room temperature was obtained for (Fe52Pt48)92Ni8 nanoparticles after annealing at 600 °C for 30 min. 相似文献
18.
Rosari Saleh Suhendro Purbo PrakosoAdel Fishli 《Journal of magnetism and magnetic materials》2012,324(5):665-670
We report the results of an investigation of Fe-doped nanocrystalline ZnO particles synthesized using the co-precipitation method with doping concentrations from 5 up to 31 at%. To understand how the dopant influenced the structural, magnetic and optical properties of nanocrystalline ZnO particles, X-ray diffraction, energy dispersive X-ray spectroscopy, infrared absorption spectroscopy, UV-vis spectroscopy, electron spin resonance spectroscopy (ESR) and vibrating sample magnetometer were employed. From the analysis of X-ray diffraction, our Fe-doped nanocrystalline ZnO particles are identified as having the wurtzite crystal structure and the unit cell volume increases with increasing doping concentrations. However, impurity phases are observed for Fe contents higher than 21 at%. Sample structures were further studied by infrared spectra, from which a broad and strong absorption band in the range of 400-700 cm−1 and -OH stretching vibrational mode at approximately 3400 cm−1 were observed. Ultraviolet-visible measurements showed a decrease in the energy gap with increasing Fe content, probably due to an increase in the lattice parameters. Magnetic measurements showed a ferromagnetic behavior for all samples. ESR results indicate the presence of Fe in both valence states Fe2+ and Fe3+. 相似文献
19.
20.
Hui Li Yongzhe Zhang Xiaojun Pan Hongliang Zhang Tao Wang Erqing Xie 《Journal of nanoparticle research》2009,11(4):917-921
The Mg- and In-doped zinc oxide (Mg
x
Zn1−x
O, In
y
Zn1−y
O) nanoparticles were successfully prepared by flame spray synthesis method. According to the results obtained from X-ray
diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis absorption spectra,
it was concluded that the Mg or In doping induced the lattice constants to change to some extent; the band gap of Mg
x
Zn1−x
O also increased with respect to the decreasing band gap of In
y
Zn1−y
O. Moreover, the strong UV emission and weak visible emission were investigated by photoluminescence spectra, while the mechanisms
of Mg or In doping on PL spectra have been discussed in detail. 相似文献