Formation of CdS nanoclusters within LB films of calixarene derivatives and study of their size-quantization

Cadmium sulphide nanoclusters formed in Langmuir–Blodgett films of various calixarene derivatives were studied by means of UV–visible spectroscopy, AFM, TEM and electron diffraction. It has been shown that calixarene cavitands of different size yield a similar kind of CdS nanoclusters as characterised by the first exciton transition near 3.2 eV. In contrast to that, CdS clusters formed within LB films of stearic acid or formaldehyde/2,6-dihydroxybenzoic acid copolymer have much lower exciton energy of 2.7 eV, corresponding to greater CdS clusters. The value of 2 nm and 4 nm in diameter were obtained, respectively, for CdS clusters in calixarene and stearic acid LB films by using Ramakhrishnaʹs results of direct calculations of the band structure. AFM and TEM results confirm the difference in size of those CdS clusters. Electron diffraction data show that CdS nanoclusters have zinc blende structure rather than wurtzite, and the lattice parameters of 0.583±0.009 nm and 0.567±0.012 nm were obtained for the clusters formed within stearic acid and calixarene matrices, respectively.