Quartz-crystal microbalance and spectrophotometric assessments of inter-core and inter-shell reactivities in nanoparticle thin film formation and growth
L. Han et al., Quartz-crystal microbalance and spectrophotometric assessments of inter-core and inter-shell reactivities in nanoparticle thin film formation and growth, J MAT CHEM, 11(4), 2001, pp. 1258-1264
Spontaneous core-shell and shell-shell reactivities of thiolate-capped nano
particles are exploited for assembling nanoparticle network thin films via
an exchange-crosslinking-precipitation route. Gold nanoparticles of two dif
ferent core sizes (2 and 5 nm) capped with decanethiolates and alkylthiols
of two different functionalities, 1,9-nonanedithiol (NDT) and 11-mercaptoun
decanoic acids (MUA), were studied as the assembly components. The film for
mation and growth involve inter-core covalent Au-thiolate bonding at both e
nds of NDT, or inter-shell non-covalent hydrogen-bonding at carboxylic acid
terminals of MUA shells. The present work focuses on a kinetic assessment
of the controlling factors based on UV-Visible spectrophotometric and quart
z-crystal microbalance measurements. These measurements probe the evolution
of the surface plasmon resonance band of nanoparticles and monitor the mas
s loading of the assembled films, respectively. Both qualitative and quanti
tative insights have been obtained for understanding the dependences of exc
hange, nucleation and crystallization processes on core size and shell stru
cture. The implication of the results for designing nanostructured assembli
es using core-shell nanoparticles as building blocks is discussed in terms
of binding site, core size and shell structure.