Cadmium and Lead Thiosemicarbazide Complexes: Precursors for the Synthesis of CdS Nanorods and PbS nanoparticles
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Cadmium and Lead Thiosemicarbazide Complexes : Precursors for the Synthesis of CdS Nanorods and PbS nanoparticles S.N. Mlondo,a N. Revaprasadu,a P. Christianb and P.O’Brienb a
Department of Chemistry, University of Zululand, Private Bag X 1001, KwaDlangezwa,3886, South Africa. b The School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL. E-mail: [email protected] ABSTRACT We report the synthesis of cadmium and lead thiosemicarbazide complexes. The single x-ray crystal structure of lead complex is reported. The cadmium thiosemicarbazide complex was thermolysed in hexadecylamine (HDA) at 140 °C and 180 °C to give CdS nanorods. The transmission electron microscopy (TEM) and XRay diffraction (XRD) measurements show that the reaction temperature has the influence on the size and shape of the nanorods. The lead thiosemicarbazide was thermolysed in tri-n-octylphosphine oxide (TOPO) at 240 °C to yield hexagonally shaped nanoparticles of PbS. The XRD confirms a face centred cubic rock salt structure.
INTRODUCTION The synthesis of nanomaterials with different morphologies is extremely important in terms of potential technological applications as the properties of nanomaterials depend primarily on the particle size and morphology. It is however a challenge to many chemists to synthesize nanoparticles with varying shapes and sizes. Recently there has been interest in the synthesis of rod-shaped nanoparticles with controllable shape and size in the quantum confinement range.1-6 The intrinsicproperties of nanoparticles mainly depend on the size, shape, composition, crystallinity and structure. Semiconductor nanoparticles with rod-like structures were prepared by Alivisatos et. al.6 who added hexylphosphonic acid (HPA), an impurity present in commercial TOPO. Peng studied various factors that influence the formation of non-spherical morphology for CdSe nanoparticles.1Their studies have shown that the nature of precursor, rate of nucleation, nature of the coordinating solvent/surfactant are the critical factors that affect the particle morphology. O’Brien et. al. have investigated the use of single-source precursors to synthesise tri-n-octylphosphine (TOPO) capped nanoparticles.7-11 The single molecular approach provides both elements within a molecule, which allows the preparation of semiconductor nanocrystals in a one-step process by the thermal decomposition of the molecular precursor in a convenient dispersing medium. This method makes use various metal complexes such as dithio-/diseleno-carbamato complexes of cadmium/zinc containing asymmetrical alkyl groups. These precursors are non-air sensitive, stable for a period of months, easy to synthesize and most of all pyrolyse cleanly to give the highest yield. Recently Nair et. al 2, reported the synthesis of TOPO capped CdS nanorods from a thiosemicarbazide complex of cadmium. In this paper we report the synthesis of CdS nanorods and PbS
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nanoparticles using thiosemicarbazide complexes of cadmium and lead respectively. The X-ray
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