Size dependence of photoluminescence and resonant Raman scattering from ZnO quantum dots

Cheng, Hsu-Yung; Lin, Kuo Feng; Hsu, Hsu Cheng; Hsieh, Wen‐Pin

doi:10.1063/1.2217925

Cited by 157 publications

(118 citation statements)

References 22 publications

(15 reference statements)

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“…50,51 However, we have not observed any significant change in the morphology of nanorods induced by thermal treatment. Moreover the diameter of the studied ZnO rods is about 90 nm, which is significantly too large to affect the electron-phonon coupling.…”

Section: -mentioning

confidence: 58%

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Yang

Zhao

Willander

et al. 2009

Journal of Applied Physics

128

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Vertically well-aligned ZnO nanorods on Si substrates were prepared by a two-step chemical bath deposition method. The structure and optical properties of the grown ZnO nanorods were investigated by Raman and photoluminescence spectroscopy. The results showed that after an annealing treatment at around 500°C in air atmosphere, the crystal structure and optical properties became much better due to the decrease in surface defects. The resonant Raman measurements excited by 351.1 nm not only revealed that the surface defects play a significant role in the as-grown sample, which was supported by low temperature time-resolved photoluminescence measurements, but also suggested that the strong intensity increase in some Raman scatterings was due to both outgoing resonant Raman scattering effect and deep level defect scattering contribution for ZnO nanorods annealed from 500 to 700°C.

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Section: -mentioning

confidence: 58%

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Yang

Zhao

Willander

et al. 2009

Journal of Applied Physics

128

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“…Cheng et al [12] measured the Raman spectra of ZnO nanoparticles of sizes between 3.5 and 12 nm ( using 325 nm wavelength ) and found that I 2LO /I 1LO does not vary much for this range of sizes but this ratio is much smaller than that for ~ 30 nm particle reported elsewhere [15]. Wang et al [13] studied ZnO nanowires of diameter between 20-100 nm using 325 nm wavelength.…”

Section: Introductionmentioning

confidence: 99%

“…Several resonant Raman investigation have been carried out on ZnO single crystals [11], as well as on nanoparticles [12,13] exhibiting LO-phonon overtones up to several orders.…”

Section: Introductionmentioning

confidence: 99%

Excitation energy dependence of electron–phonon interaction in ZnO nanoparticles

Sahoo

Sivasubramanian

Dhara

et al. 2008

Solid State Communications

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Raman spectroscopic investigations are carried out on ZnO nanoparticles for various photon energies. Intensities of E 1 -LO and E 2 modes exhibit large changes as the excitation energy varied from 2.41 to 3.815 eV, signifying substantially large contribution of Frohlich interaction to the Raman polarizability as compared to deformation potential close to the resonance. Relative strength of these two mechanisms is estimated for the first time in nanoparticles and compared with those in the bulk.

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“…Its production is straightforward, yielding nanoparticle of various sizes and shapes, starting from 3 nm and larger. 7,13 ZnO material properties, including a direct wide bandgap ͑3.4 eV͒ electronic structure, and high exciton energy of 60 meV ͑compare to that of 25 meV of cadmium selenide͒, are very attractive for a new generation of electrooptic devices, e.g., light-emitting diodes and lasers in the UV spectral range. The wide bandgap of ZnO requires excitation at a wavelength of 320 nm in the UV spectral range, with principle emission at 385 nm, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo

et al. 2008

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Abstract. Zinc oxide ͑ZnO-nano͒ and titanium dioxide nanoparticles ͑20 to 30 nm͒ are widely used in several topical skin care products, such as sunscreens. However, relatively few studies have addressed the subdermal absorption of these nanoparticles in vivo. We report on investigation of the distribution of topically applied ZnO in excised and in vivo human skin, using multiphoton microscopy ͑MPM͒ imaging with a combination of scanning electron microscopy ͑SEM͒ and an energy-dispersive x-ray ͑EDX͒ technique to determine the level of penetration of nanoparticles into the sub-dermal layers of the skin. The good visualization of ZnO in skin achieved appeared to result from two factors. First, the ZnO principal photoluminescence at 385 nm is in the "quiet" spectral band of skin autofluorescence dominated by the endogenous skin fluorophores, i.e., NAD͓P͔H and FAD. Second, the two-photon action cross section of ZnO-nano ͓ ZnO ͑TPEF͒ ϳ 0.26 GM; diameter, 18 nm͔ is high: ϳ500-fold of that inferred from its bulk third-order nonlinear susceptibility ͓Im ZnO ͑3͒ ͔, and is favorably compared to that of NAD͓P͔H and FAD. The overall outcome from MPM, SEM, and EDX studies was that, in humans in vivo, ZnO nanoparticles stayed in the stratum corneum ͑SC͒ and accumulated into skin folds and/or hair follicle roots of human skin. Given the lack of penetration of these nanoparticles past the SC and that the outermost layers of SC have a good turnover rate, these data suggest that the form of ZnO-nano studied here is unlikely to result in safety concerns.

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Size dependence of photoluminescence and resonant Raman scattering from ZnO quantum dots

Cited by 157 publications

References 22 publications

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Excitation energy dependence of electron–phonon interaction in ZnO nanoparticles

Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo

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