Open Access Nano Express

Effect of surface ligands on the optical properties of aqueous soluble CdTe quantum dots

Fernanda O Silva1, Melissa S Carvalho1, Renato Mendonça2, Waldemar AA Macedo2, Karla Balzuweit3, Peter Reiss4 and Marco A Schiavon1*

Author Affiliations

1 Grupo de Pesquisa em Química de Materiais - (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, CEP, São João Del Rei, Minas Gerais, 36301-160, Brazil

2 Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, Minas Gerais, 31270-901, Brazil

3 Departamento de Física, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, 30123-970, Brazil

4 CEA-Grenoble, INAC-SPrAM (UMR 5819 CEA-CNRS-UJF)-LEMOH, 17 Rue des Martyrs, 38054, Grenoble, Cedex 9, France

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Nanoscale Research Letters 2012, 7:536  doi:10.1186/1556-276X-7-536

Published: 27 September 2012

Abstract

We investigate systematically the influence of the nature of thiol-type capping ligands on the optical and structural properties of highly luminescent CdTe quantum dots synthesized in aqueous media, comparing mercaptopropionic acid (MPA), thioglycolic acid (TGA), 1-thioglycerol (TGH), and glutathione (GSH). The growth rate, size distribution, and quantum yield strongly depend on the type of surface ligand used. While TGH binds too strongly to the nanocrystal surface inhibiting growth, the use of GSH results in the fastest growth kinetics. TGA and MPA show intermediate growth kinetics, but MPA yields a much lower initial size distribution than TGA. The obtained fluorescence quantum yields range from 38% to 73%. XPS studies unambiguously put into evidence the formation of a CdS shell on the CdTe core due to the thermal decomposition of the capping ligands. This shell is thicker when GSH is used as ligand, as compared with TGA ligands.

Keywords:
CdTe; Surface ligands; Optical properties; Semiconductor nanocrystals