Developing a coordination chemistry of intact quantum dots: The preparation of novel nanocomposites of PbS with CdS or C
- PDF / 113,449 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 145 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Developing a coordination chemistry of intact quantum dots: The preparation of novel nanocomposites of PbS with CdS or CdSe Tito Trindade Department of Chemistry, University of Aveiro, 3810 Aveiro, Portugal
Paul O’Briena) Department of Chemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, United Kingdom
Xiao-mei Zhang Interdisciplinary Research Centre for Semiconductor Materials, Blackett Laboratory, Imperial College of Science, Technology and Medicine, London SW7 2BZ, United Kingdom (Received 22 May 1998; accepted 3 August 1999)
In this communication a new kind of nanocomposite is reported in which a bridging coordination ligand, 2,2⬘-bipyrimidine, is used to bind quantum dots of CdS or CdSe (4–6 nm) to larger PbS nanoparticles.
There are several reports of nanostructures consisting of more than one semiconducting phase in which a quantum dot of one material is coated with a shell of another semiconductor.1–5 Another kind of nanostructure can be built from extended arrays of spheres of a semiconductor6 and the linking of similar quantum dots by thiolates has been reported.7 In this communication we report a novel approach to the synthesis of nanostructures comprising two different semiconducting phases in which a molecular bridging ligand is used to support the composite. The bridging ligand 2,2⬘-bipyrimidine (BPM; Scheme 1) has been used to promote binding between intact nanocrystallites of PbS and CdE (E ⳱ S, Se).
SCHEME 1.
Nanodispersed tri-n-octylphosphine oxide (TOPO)– passivated CdS or CdSe (40–60 Å) were prepared by the thermolysis of mixed alkyl cadmium dichalcogenocarbamates in TOPO, as described previously.8,9 Nanoparticles of PbS were prepared by the thermolysis of dithiocarbamato lead (II) compounds in TOPO.10 The novel nanocomposites were prepared by mixing nanodispersed CdE and PbS, in toluene, in the presence of an excess of BPM and stirring for 24 h. a)
Address all correspondence to this author. Present address: The Manchester Materials Science Centre and the Chemistry Department, Manchester University, Oxford Road, Manchester M13 1PL, United Kingdom. 4140
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 11, Nov 1999 Downloaded: 15 Mar 2015
The CdE/BPM/PbS nanocomposites were synthesized using CdE and PbS nanocrystallites that had distinct and different morphologies. The CdE nanoparticulates used are close to spherical (4–6 nm) whereas the PbS nanoparticulates had larger dimensions and cubic particles predominated. A typical high-resolution electron microscopy (HREM) image of the CdS/BPM/PbS nanocomposite is shown in Fig. 1; many such images were analyzed in the course of the study. The larger PbS nanocrystals were always observed to be surrounded by smaller nanocrystallites of CdS. The latter were somewhat obscured by a cloudy and noncrystalline background (distinct from the graphite background), which is probably associated with the presence of BPM in the final nanocomposite. Several images showed large da
Data Loading...
