Structural and optical properties of CdS nanocrystals grown in water‐soluble diblock copolymer

Abstract

Methoxy‐capped poly(ethylene glycol) (PEG) was used to prepare ATRP initiator (PEGBr). PEGBr was copolymerised with t ‐butyl methacrylate (tBMA) by using atom transfer radical polymerization (ATRP) chemistry. tBMA residues were converted to methacrylic acid (MAA) by acidic hydrolysis under mild conditions to give well‐defined PEG–b ‐PMAA diblock copolymers. Near‐monodisperse micellization was observed by the addition of CdCl2 (1.0 wt%) into PEG–b ‐PMAA diblock copolymer solution at pH 11.0 due to complexation of MAA‐ with Cd+2 ions. After addition of thioacetamide into the micellar solution, the Cd+2 cations in the resulting micelles were converted to CdS to obtain CdS nanocrystals in the micelles. The band gap of CdS nanocrystals was obtained from the absorbance measurements in the visible range and found to be 2.4 eV. Electrical resistivity of CdS nanocrystals was found to be 0.21 Ωcm. The thickness of the CdS thin films on glass substrate was found to be 131.14 nm. XRD pattern of CdS nanocrystals has shown that (111), (110), (021), and (220) diffractions are related to the cubic CdS nanocrystals. Preferred crystallographic orientation of the CdS nanocrystals is (110). TEM results have shown that grain sizes of CdS thin films vary between 64 and 133 nm (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)