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Hollow ZnO Microspheres with Complex Nanobuilding Units

Hollow ZnO Microspheres with Complex Nanobuilding Units

Bin Liu†and Hua Chun Zeng*,†,‡

Department of Chemical and Biomolecular Engineering,and Minerals,Metals,and Materials Technology Center,Faculty of Engineering,National Uni V ersity of Singapore,10Kent

Ridge Crescent,Singapore119260

Recei V ed July31,2007 Re V ised Manuscript Recei V ed September30,2007 Over the past decade,hollow structures have received great attention in the general synthesis of functional materials because of their important applications in vastly different fields.1–6Among known preparative methods,1–6templating has been proven to be an effective approach to tailor-make interior spaces of hollow structures,in which both hard templates such as inorganic or organic core supports and soft templates such as vesicles and micelles in emulsions or ionic

liquids have been utilized.1–4To explore new capabilities of templating method,researchers should further investigate the self-assembly of nanobuilding units on the interface or surface of the templates,because it belongs to the general “bottom-up”paradigm adopted in nanotechnology.2In particular,several types of colloidosomes assembled from sphereical or rodlike polymeric building blocks have been fabricated with colloidal templating.2It is noted,however, that in these pioneering works,the constructional units are limited to only simple geometrical shapes.2Herein,we will use zinc oxide(ZnO,an important electronic and photonic material with a direct band gap of3.37eV7)to demonstrate that hollow spheres of metal oxides with external diameters up to several tens of micrometers can be prepared via assembly of complex nanobuilding units,which,in turn,were constructed from even smaller unidirectionally attached nanorods.

In our synthesis,0.5-1.0g of cetyl-trimethyl-ammonium-bromide(CTAB)was dissolved in30.0-60.0mL of pure ethanol under vigorous stirring.The CTAB-containing etha-nol solution became clear and was then added to3.0-6.0 mL of zinc nitrate solution(Zn(NO3)2·6H2O;[Zn2+])0.50 M,[Zn2+]:[OH-])1:10),followed by adding5.0mL of ethylenediamine(C2H4(NH2)2,EDA).The solution mixture was continuously stirred for5min and then transferred to a Teflon-lined stainless steel autoclave and kept at80-180°C for20-180min inside an electric oven.ZnO products were collected by centrifugation and thorough washings with water.Detailed synthetic conditions for all samples reported herein can be found in the Supporting Information,SI-1.The prepared ZnO samples were further characterized with powder X-ray diffraction(XRD,Shimadzu XRD-6000,Cu K R radiation),scanning electron microscopy,energy-dispersive X-ray spectroscopy(SEM/EDX,JSM-5600LV),field-emission SEM(FESEM/EDX,JSM-6700F),transmis-sion electron microscopy,selected area electron diffraction (TEM/SAED,JEM-2010F,200kV),and high-resolution TEM(HRTEM,Philips-CM200FEG,200kV).Specific surface areas of the ZnO samples were also measured with the Brunauer–Emmett–Teller method(BET,NOVA-3000). Figure1shows the general morphology of ZnO spheres prepared at the optimal conditions of80-100°C(see the

*Corresponding author.Tel:(65)6516-2896.Fax:(65)6779-1936.E-mail: chezhc@nus.edu.sg.

†Department of Chemical and Biomolecular Engineering,National University of Singapore.

‡Minerals,Metals,and Materials Technology Center,National University of Singapore.

(1)(a)Caruso,F.;Caruso,R.A.;Möhwald,H.Science1998,282,1111.

(b)Göltner,C.G.Angew.Chem.,Int.Ed.1999,38,3155.(c)Caruso,

F.Ad V.Mater.2001,13,11.

(2)(a)Dinsmore,A.D.;Hsu,M.F.;Nikolaides,M.G.;Marquez,M.;

Bausch,A.R.;Weitz,D.A.Science2002,298,1006.(b)Noble,P.F.;

Cayre,O.J.;Alargova,R.G.;Velev,O.D.;Paunov,V.N.J.Am.

Chem.Soc.2004,126,8092.

(3)(a)Sun,Y.;Xia,Y.Science2002,298,2176.(b)Sun,Y.;Mayers,

B.;Xia,Y.Ad V.Mater.2003,15,641.

(4)(a)Nakashima,T.;Kimizuka,N.J.Am.Chem.Soc.2003,125,6386.

(b)Guo,C.-W.;Cao,Y.;Xie,S.-H.;Dai,W.-L.;Fan,K.-N.Chem.

Commun.2003,700.

(5)(a)Yin,Y;Rioux,R.M.;Erdonmez,C.K.;Hughes,S.;Somorjai,

G.A.;Alivisatos,A.P.Science2004,304,711.(b)Park,S.;Lim,

J.-H.;Chung,S.-W.;Mirkin,C.A.Science2004,303,348.(c)Yang,

H.G.;Zeng,H.C.J.Phys.Chem.B2004,108,3492.(d)Liu,B.;

Zeng,H.C.J.Am.Chem.Soc.2004,126,8124.(e)Yang,H.G.;

Zeng,H.C.Angew.Chem.,Int.Ed.2004,43,5930.(f)Liu,B.;Zeng,

H.C.J.Am.Chem.Soc.2004,126,16744.

(6)(a)Goldberger,J.;He,R.;Zhang,Y.;Lee,S.;Yan,H.;Choi,H.-J.;

Yang,P.Nature2003,422,599.(b)Dai,Z.R.;Gole,J.L.;Stout, J.D.;Wang,Z.L.J.Phys.Chem.B2002,106,1274.(c)Dai,Z.R.;

Pan,Z.W.;Wang,Z.L.J.Am.Chem.Soc.2002,124,8673.

(7)(a)Tang,Z.K.;Wong,G.K.L.;Yu,P.;Kawasaki,M.;Ohtomo,A.;

Koinuma,H.;Segawa,Y.Appl.Phys.Lett.1998,72,3270.(b)Huang, M.H.;Mao,S.;Feick,H.;Yan,H.;Wu,Y.;Kind,H.;Webber,E.;

Russo,R.;Yang,P.Science2001,292,1897.(c)Huang,M.H.;Wu, Y.;Feick,H.;Tran,N.;Weber,E.;Yang,P.Ad V.Mater.2001,13, 113.(d)Johnson,J.C.;Yan,H.;Schaller,R.D.;Haber,L.H.;

Saykally,R.J.;Yang,P.J.Phys.Chem.B2001,105,11387.(e)Pan, Z.W.;Dai,Z.R.;Wang,Z.L.Science2001,291,1947.(f)Gao,P.;

Wang,Z.L.J.Phys.Chem.B2002,106,

Hollow ZnO Microspheres with Complex Nanobuilding Units

12653.

Figure1.SEM images of hollow ZnO microspheres assembled from numerous complex nanobuilding units(also see Figure3):(a–c)100°C for2h,and(d)80°C for2h(see the Supporting Information,SI-1,for more experimental details).

5824Chem.Mater.2007,19,5824–5826

10.1021/cm702121v CCC:$37.00 2007American Chemical Society

Published on Web10/12/2007