Hierarchical Assembly of ZnO Nanostructures on SnO2 Backbone Nanowires

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E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

Figure 1.(a)SEM image of SnO 2nanowires.(b)Typtical TEM image of a single SnO 2nanowire.Inset is a HRTEM image of the wire showing its single-crystalline characteristics.

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E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

Supporting Information,Figure S2)shows lattice mismatches of 1.9and 5.6%along the b direction and direction of SnO 2,respectively.Therefore,the ZnO nanocrystals,which tend to elongate along the [0002]direction during the solution growth,prefer to nucleate

and grow on the four {101}planes of SnO 2nanowire backbones.This contributes to the formation of fold symmetry branches.

X-ray diffraction (XRD)analysis was performed investigate the crystal phase of SnO 2nanowires Figure 3.Structural characterization of the heterointerface.(a)TEM image taken near the junction.(b)HR lattice image of the junction.(c)Electron diffraction pattern taken from the ZnO nanorod branches.(d)Fast Fourier transformation pattern of the HRTEM of the SnO 2backbone in (b).The electron beam di-rections (right-bottom in c and d)are calculated based on in-dexed planes.2.Hierarchical SnO 2/ZnO nanostructures with ZnO nanorod branches on SnO 2nanowire backbones.(a)SEM image.Typical TEM image.(c,d)Energy-dispersive spectrum (EDS)recorded from the SnO 2trunk and one ZnO nanorod branch Figure 2b,respectively.Note that the oxygen peak is not present,which is arti?cial.

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E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

Figure 4.XRD patterns of the primary SnO 2nanowires (curve a)and SnO 2/ZnO hybrids with ZnO nanorods grown on SnO nanowires (curve b);?indicates the rutile phase of SnO 2,and ?indicates the wurtzite phase of ZnO.

Growth manipulation of the SnO 2/ZnO hierarchical nanostructures by using different concentrations of Zn(NO 8h:(a)0.01M,(b)0.025M,(c)0.05M,(d)0.1M.

Figure 6.Growth process of the SnO 2/ZnO hierarchical nanostructures.Top row:schematics.Bottom row:corre-sponding SEM images of the product.(a)Before the growth.The SnO 2nanowire surfaces are coated with ZnO seed nano-particles.Subsequent solution epitaxial growth of ZnO

nanorods on the four side faces of SnO 2nanowires.(b)With low Zn(NO )precursor concentration,the branches are in-D o w n l o a d e d b y D A L I A N I N S T O F C H E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

With time in-tends to grow into rodlike crystals in an aqueous sys-Figure 7.SnO 2/ZnO hierarchical structures with ZnO nano?akes grown on SnO 2nanowires by

adding trisodium citrate.(a)Low-and (b)high-magni?cation SEM images.(c)TEM image.Figure 8.Photoluminescence (PL)spectra of the primary SnO 2nanowires (curve 1)and SnO 2/ZnO hybrids with ZnO nanorod branches (curve 2)recorded at (a)room tempera-ture and (b)10K.

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E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

It is interesting to notice that the PL peaks of the SnO backbone are missing for the hybrid nanostructures.We Figure 10.Random lasing action of the SnO 2/ZnO hierarchical nanostruc-tures.(a)Room-temperature PL spectra at different excitation powers.(b)

Plot of integrated intensity versus input power intensity,showing the on-set of nonlinearity at a threshold of ?0.18MW/cm 2.(c)Emission spectra of

the sample with different excitation area.(d)Spectra radiated from 45and 60°from the sample surface.

Figure 9.Temperature-dependent PL spectra of the SnO 2ZnO hybrid nanostructures.D o w n l o a d e d b y D A L I A N I N S T O F C H E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

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E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x

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E M P H Y S I C S o n O c t o b e r 9, 2009 | h t t p ://p u b s .a c s .o r g P u b l i c a t i o n D a t e (W e b ): S e p t e m b e r 22, 2009 | d o i : 10.1021/n n 900848x