Synthesis of cadmium sulphide in pure and mixed Langmuir-Blodgett films of n -octadecylsuccinic acid |
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Authors: | G Hemakanthi Balachandran Unni Nair and Aruna Dhathathreyan |
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Institution: | (1) Chemical Laboratory, Central Leather Research Institute, 600 020 Adyar, Chennai, India |
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Abstract: | Cadmium sulphide (CdS) nanoparticles were grown by the reaction of sodium sulphide (Na2S) with Langmuir-Blodgett (LB) films of cadmium salts ofn-octadecylsuccinic acid (ODSU) and with LB films of ODSU in mixtures of octadecylamine and octadecyl alcohol. The results
indicate that heterogeneous nucleation and aggregation in the pure ODSU LB films due to processes like Ostwald ripening are
destabilized by the presence of the long-chain amine and alcohol in mixed systems. CdS nanoparticles in the LB films were
monitored by UV-visible absorption spectra, which allow an estimation of the size of the particles. The morphology, size and
nature of the nanocrystallites formed depend on whether the sulphidation was done on the pure film or in the mixed films.
It is seen that particles of size around 1.6 nm were formed in ODSU/octadecylalcohol and ODSU/ octadecylamine mixed LB films
while in pure ODSU films the size was about 2.7 nm. These films showed typical needle-shaped structures, as observed by the
optical microscopic technique. Mean size and morphology were confirmed by transmission and scanning electron microscopy, while
selective area electron diffraction patterns showed six-fold symmetry and indicated that the CdS crystals grow epitaxially
with respect to the monolayer. Further, the crystallisation enhanced in the mixed LB films showed a characteristic zinc oxide
(Wurtzite) structure compared with the pure ODSU matrix. |
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Keywords: | CdS LB films octadecylsuccinic acid epitaxy |
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