CdS and ZnS Nanoparticles Growth in Different Reaction Media: Synthesis and Characterization
- PDF / 476,364 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 81 Downloads / 186 Views
Z3.32.1
CdS and ZnS Nanoparticles Growth in Different Reaction Media: Synthesis and Characterization F. Antolinia, c, E. Traveb, L. Mirenghia, M. Rea, G. Matteib, L. Tapfera and P. Mazzoldib a ENEA, UTS-MAT, CR Brindisi, Strada Statale Appia, 72100 Brindisi, Italy b Dip. Fisica “G. Galilei”, Università di Padova, via Marzolo 8, 35131 Padova, Italy c present address: UTS-MAT, CR Faenza, Via Ravegnana 186,48018 Faenza, Italy ABSTRACT In this work we report on the growth of cadmium sulfide and zinc sulfide nanocrystals by thermolysis, starting from a metal thiolate in a (i) solventless way, (ii) by a novel route in tryoctilphosphine oxide (TOPO), and (iii) by direct synthesis in a polystyrene matrix. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the nanocrystals fabricated by the different methods are under optimized growth conditions single crystals of zincblende structure and of regular spherical shape. The average size was estimated to be between 2.0-3.0 nm with a size dispersion that depends on the synthesis route and is in the range between 10% and 20%. The XPS results indicate that for the nanoparticles obtained via solventless strategy the sulfur is present both as bonded to the metal atom and to the organic residue, while in the TOPO synthesized nanoparticles the sulfur signal has only one component associated to the metal-sulfide bond. The photoluminescence spectroscopy (PL) analysis of CdS crystals clearly evidences the typical emissions of nanosized zincblende CdS monocrystalline particles. Furthermore, the optical spectroscopy data indicate that the size distribution of the Cdsulfide - TOPO nanoparticles seems to be generally larger than that ones grown directly in polymer matrix. For all the CdS samples, the metal-sulfide nanocrystals exhibit a trap-related radiative transition at about 2eV that can be attributed to the hole-electron recombination at particle surface defect-center. INTRODUCTION Semiconductor quantum dots (QDs) are of great interest due to their potential application in the fabrication and design of novel light-emitting diodes [1] and photovoltaic devices [2]. The QDs, in fact, present a narrow fluorescence bands and optical purity that, coupled with an extremely high photostability, allow them to be advantageous over conventional dyes [3]. Their unique electrical and optical properties are due to the quantum confinement of electron and hole states within the particle [4]. Considering these properties a strong effort in chemical synthesis of nanoparticles [5] has been carried out in order to find synthetic strategies allowing their narrow size distributions, size tuning and an easy way to scale up the synthesis itself. The use of single source precursors for the QDs synthesis of metal sulfides fulfills these requirements. In this reaction scheme the first step is represented by the synthesis of the single source precursor i.e. the metal-(bis)thiolate [6]. This product is stable under normal conditions and easy to prepare without the use of intrinsic highl
Data Loading...
