Metal sulfide sub-nanometer clusters formed within calix(8)arene Langmuir-Blodgett films
Özet
This work describes the construction of layered Langmuir-Blodgett (LB) films of a calixarene and the use of these
as matrices for the synthesis of a range of metal sulfide nanoparticles. CuS, CdS, HgS, and PbS nano-clusters were
formed within LB films of an octa-tertbutyl-calix(8)arene substituted with carboxylic acid groups deposited on
different substrates (glass, quartz, and silicon) from either: (i) aqueous sub-phases containing 0.5 mM of the
respective metal chloride salt (e.g. CuCl2, CdCl2, HgCl2, PbCl2), or (ii) by soaking the LB films in 10 mM solutions
of the above salts for 1 h. The formation of metal-sulfide (MeS) nanoparticles was then achieved by exposing
samples to H2S gas for 10–12 h.
Deposition from salt containing subphases was more reliable and resulted in stoichiometric metal sulfides
(CdS, HgS, PbS) being formed within LB films of the calix(8)arene carboxylic acid whereas Cu tended to form
polysulfides. UV–vis absorption spectroscopy showed the presence of multiple absorption bands corresponding to
electron transitions between energy levels in nanoclusters formed as result of quantum confinement of electrons
and holes. The MeS clusters obtained by this process are amongst the smallest reported for LB films, being of the
range 0.6–1.2 nm.
