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Published on the web January 16, 2010
Template-based In Situ Fabrication and Melamine Sensing of
Bis(8-quinolinolato)zinc(II) Complex Nanorod Arrays
Xiang-Zi Li,1,2 Rui Yu,1 and Xian-Wen Wei*1
1College of Chemistry and Materials Science, Key Laboratory of Functional Molecular Solids, Ministry of Education,
Anhui Key Laboratory of Molecule-Based Materials, Anhui Normal University, Wuhu 241000, P. R. China
2Department of Chemistry, WanNan Medical College, Wuhu 241000, P. R. China
(Received October 5, 2009; CL-090891; E-mail: xwwei@mail.ahnu.edu.cn)
Parallel polycrystalline bis(8-quinolinolato)zinc(II) complex
several times with deionized water, then it was dipped into 2 M
NaOH for 4 min to partly remove AAO membrane and for 24 h to
remove the membrane substrate completely. Finally, the product
was rinsed with deionized water 10 times. For melamine sensing,
the ZnQ2 nanorods were dispersed into deionized water by
ultrasonication and separated into several equal portions (4 mL)
to get nearly the same disperse concentration, then 0.2 mL of
aqueous melamine solution with different concentration (100-
600 ng mL¹1) was injected into each portion, and their PL
properties were checked. All the reagents used in the experiment
were of AR purity.
The morphology of the products was examined by field
emission scanning electron microscopy (FE-SEM, S4800).
Figure 1a shows a typical cross-section image of the nanorod
arrays, the products are composed of parallel, smooth, and uni-
form nanorods with length up to 25 ¯m, and the nanorod arrays
are of high-density with a high filling rate from top-view image
(Figure 1b). After the AAO being removed completely, separate
nanorods can be obtained (Figures 1c and 1d) with some shorter
length (15 ¯m) due to treatments of ultrasonic and rinsing, and
their diameters are in a range of 250-320 nm with the aspect ratio
over 80. The transmission electron microscopy (TEM, Hitachi
H800) image of the products shown in Figure 2a confirmed
that the nanorods have similar sizes as shown by SEM. The
corresponding selected-area electron diffraction (SAED) pattern
(insert of Figure 2a) shows the nanorods are polycrystalline.
X-ray powder diffraction (XRD, SHIMADZU 6000) pattern
of the products shown in Figure 2b could be indexed to poly-
crystalline ZnQ24 (JCPDS No. 48-2116), which is in accordance
with the SAED result. From which the grain size of nanorods
nanorod arrays, with diameters in the range of 250-320 nm and
length of 25 ¯m, are in situ fabricated by liquid-liquid interfacial
precipitation in the pores of porous anodic aluminum oxide
membrane. The prepared nanorods show an enhanced photo-
luminescence emission compared to submicron particles and can
be used as a good melamine probe for easy and highly sensitive
detection.
Since tris(8-quinolinolato)aluminum complex was first
reported,1 metal-8-quinolinolato (MQn, M: metal) complex
nanowires and nanorods have been investigated extensively due
to their unique properties and applications in the field of organic
light-emitting devices2,3 and photoluminescence (PL) sensing for
protein4 and glucose.5 There have been various approaches to
9
prepare nanowires of CdQCl,5 AlQ3,6-8 GaQ3 and nanorods of
AlQ3,10-12 ZnQ2,4 CdQ2,13 such as sonochemical,4,5,11 sublima-
tion,6-9 surfactant-assisted,10,12 and solvothermal routes.13,14
However, work on the hard template, in situ fabrication of one-
dimensional (1D) MQn nanostructures is rare, and it is still a
challenge to prepare parallel and uniform 1D MQn arrays with
larger aspect ratios. As is known to all, hard-template-mediated
preparation, initiated by Martin,15 has proven to be a more simple
and promising route to prepare ordered arrays of nanostructures.
Particularly, anodic aluminum oxide (AAO) membrane is
considered as an attractive template material for fabricating 1D
nanostuctures,16-19 because its pore density and aspect ratio are
high, the pore distribution is uniform, and the shape and size of
prepared 1D nanomaterials can be easily controlled.
Herein we present a simple and mild method to fabricate
ZnQ2 nanorod arrays embedded in AAO templates with a high
filling rate and uniform growth. The synthesis technique is based
on the in situ reaction of Zn2+ and 8-quinolinol through liquid-
liquid interfacial precipitation into the pores of AAO membrane
without heat and any surfactants, and the prepared nanorods are
polycrystalline and show an enhanced photoluminescence
compared to that of submicron particles. Moreover, the ZnQ2
nanorods can be developed into a fluorescence sensor for
melamine.
The AAO membranes (Anodiscµ) were purchased from
Whatman Co., the quoted pore diameter of which was ca.
200 nm. In general synthesis, the AAO membranes were put into
the middle of two silica half cells.16 The same volumes of 0.10 M
Zn(CH3COO)2 and 0.05 M 8-quinolinol in ethanol were added
into each cell, respectively. The reaction remained for 48 h at
ambient temperature. Zn2+ and 8-quinolinol would enter the
pores of the AAO membranes and form nanorods. The resulting
ZnQ2/AAO composite was polished with sand paper and washed
Figure 1. FE-SEM images of the prepared nanorod arrays (a), (b)
and separate nanorods (c), (d).
Chem. Lett. 2010, 39, 114-115
© 2010 The Chemical Society of Japan
Li, Xiang-Zi
