Dichloro (bis[diphenylthiourea]) cadmium complex as a precursor for HDA-capped CdS nanoparticles and their solubility in water

Makwena J Moloto,Tshinyadzo R Tshikhudo,Manuel Fernandes,Poslet M Shumbula

doi:10.4102/sajs.v106i7/8.311

Abstract

A single-source precursor route has been explored by using the diphenylthiourea cadmium complex as the source of cadmium sulphide (CdS) nanoparticles. The reaction was carried out using hexadecylamine (HDA) as the solvent and stabilising agent for the particles. The phenylthiourea complex was synthesised and characterised by means of a combination of spectroscopic techniques, microanalysis and X-ray crystal structural analysis. The diphenylthiourea complex was thermolysed in HDA at 120 °C for 1 h to produce CdS nanoparticles. The CdS nanoparticles prepared were made water-soluble via a ligand exchange reaction involving the use of pyridine to displace HDA. The pyridine was, in turn, replaced by glucose and glucuronic acid. The absorption and emission spectra showed the typical features of quantum confinement for the nanoparticles for both HDA-capped and glucose- or glucuronic acid-capped CdS nanoparticles. The change in the capping groups, from HDA to glucose and glucuronic acid, resulted in absorption and emission features that were almost similar, with only slight red-shifting and tailing.

Highlights

Thiourea and its alkyl derivatives are important precursors for the preparation of metal sulphide nanoparticles
The cadmium complex contains the central atom in a distorted tetrahedral geometry, the edges of which are shared by two sulphur atoms of the diphenylthiourea and two chlorine atoms of the metal source
The C-S (1.7142[16]) and C-N (1.3322[6]) bonds in diphenylthiourea ligands show intermediate character between a single and a double bond length. These bond distances/lengths are in good agreement with those on the thiourea molecules reported in the Cambridge structural database (CSD) by Allen et al.[30], that is, 1.726 Å (C-S) and 1.322 Å (C-N)

Summary

Introduction

Thiourea and its alkyl derivatives are important precursors for the preparation of metal sulphide nanoparticles. Semiconductor nanoparticles, which are known as quantum dots (QDs) or nanocrystals, are small clusters of atoms of a length in the range of 1 nm – 100 nm They exhibit properties that are different from those of the bulk/macrocrystalline material.[4] Some of the fundamental factors (related to size of the individual nanocrystal) that distinguish semiconductor nanoparticles from their corresponding macrocrystalline material are, (1) a high dispersity (large surface-to-volume ratio) associated with the particles, with both physical and chemical properties of the semiconductor being sensitive to surface structure and (2) the actual size of the particle, which can determine the electronic and physical properties of the material.[5] Over the past decades, semiconductor nanoparticles have been found to be an interesting subject in both research and technical applications, because of their unique size-dependent optical and electronic properties. Scientists worldwide are interested in the quantum size effect[6,7] and the promising applications of semiconductor nanoparticles therein, through their use in light-emitting diodes, solar cells, biological labelling and diagnostic, catalysis, photovoltaic devices and lasers.[8,9] The most significant aspect of the research and manipulation of semiconductor nanoparticles lies in the synthesis of high-quality nanocrystals with a uniform shape and size

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Conclusion