Synthesis and characteristics of ZnS/CdS composite nanocrystals in block copolymer micelle
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Synthesis and characteristics of ZnS兾CdS composite nanocrystals in block copolymer micelle Dayang Wang,a) Yaan Cao, Xintong Zhang, Xinming Qian, Xin Ai, Zhiqiang Liu, Fengqui Liu, Dejun Wang, Yubai Bai, Tiejin Li, and Xinyi Tang Department of Chemistry, Jilin University, Changchun, 130023, People’s Republic of China (Received 7 September 1998; accepted 19 January 1999)
In hydroxylated poly(styrene-b-butadiene-b-styrene) (HO–SBS) micelle, ZnS兾CdS composite nanocrystals were prepared by adding Cd21 ions and Zn21 ions to the system sequentially. The resulting composites were identified with elemental analysis, transmission electron microscopy, x-ray diffraction, surface photovoltage spectroscopy, and electric field induced surface photovoltage spectroscopy.
Currently there is considerable interest in nanocrystals for their new electronic, optical, magnetic, catalytic, and mechanical properties. The area of application that is foreseen to benefit from the small size and selforganization of nanocrystals includes nanoelectronics, nonlinear optics, catalysis, and high-density information storage and processing.1–4 Nanocomposites provide a new method to improve the processability and stability of nanocrystals.5 The general principles in the construction of nanocomposites involve the intimate mixing of nanocrystals with a processable matrix. The matrix materials can be polymers, block copolymers, polymer blends, glasses, or ceramics. Particulate phase nanocrystals can be prepared in situ or ex situ. The construction of nanocrystals using block copolymer micelle has been inspired by their nanosized self-organized structures.6–11 Recently, increasing attention has been given to composite nanocrystals because the connection of two semiconductor nanocrystals will lead to a series of novel electronic effects.3,4,12 So far, little work has been done on the preparation of composite nanocrystals in block copolymer micelle. In the present paper, based on the large stability of block copolymer micelle, we have prepared ZnS兾CdS composite nanocrystals within them and investigated the electron process of the resulting composite nanocrystals. Poly(styrene-b-butadiene-b-styrene) (SBS), a commercial block copolymer manufactured by Baling Oil Chemical Industry Company (Yueyang, People’s Republic of China), is used in this work. Its mean molecular weight is 139,000 and its weight fraction of polystyrene (PS) block is 40%. In a typical hydroxylation run,13 the double bonds of the PB blocks of the used SBS were turned into HO groups. The hydroxyl value of the resulting hydroxylated polymer (HO–SBS) was measured to be about 0.36 by the acidation method.14 HO–SBS was dissolved in toluene to form the solution with concentration of 1% (weight/volume). In a)
Address all correspondence to this author. J. Mater. Res., Vol. 14, No. 6, Jun 1999
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toluene, HO–SBS molecules formed nanosized micelle consisting of a PS block shell and a HO–PB block core.1
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