Growth dynamics of polyamidoamine dendrimer encapsulated CdS nanoparticles

Determination of the energetics of formation of semiconductor/dendrimer nanohybrid materials: implications on the size and size distribution of nanocrystals

“…For the G2 dendrimer with a succinamic acid surface group, the K and DH values for the zone I are respectively 1 Â 10 4 M À1 and À70.1 kJ mol À1 for zone I, whereas for zone II the values are 3.8 Â 10 2 M À1 and À15.6 kJ mol À1 . The observed results show that the formation of particles in phase II is dominated at zone II, which supports the mechanism proposed by Mendez et al 27 In order to look into the role of the dendrimer core in nanocrystal formation, the thermodynamic parameters were determined for ZnS particle formation with G4 having an ethylenediamine core and G4 with a cystamine core. In the case of variation of the core of the dendrimer, the zone I values varied signicantly, whereas the zone II values remained almost the same.…”

“…2 and 3). In view of the different diffusion coefficients of S 2À ions across the two different structural zones (the internal core and external surface structure), the reactions of sulde with M(II)-dendrimer lead to the formation of CdS or ZnS nanoclusters inside the dendrimer in phase I, while in the second phase, the particles form on the outer surface of the dendrimer molecule, as proposed by Mendez et al 27 Furthermore, it has been pointed out that the growth process is controlled by mass transport of the counterion S 2À across the region of the internal and peripheral dendrimer sites. Under the synthesis conditions, following the mechanism proposed by Yamamoto et al, 28 it is assumed that nanoparticles grow both inside and outside dendrimer for generation 4 to a comparable extent, whereas in generation 5 and 2, the particles preferentially grow inside and outside, respectively.…”

“…Under the synthesis conditions, following the mechanism proposed by Yamamoto et al, 28 it is assumed that nanoparticles grow both inside and outside dendrimer for generation 4 to a comparable extent, whereas in generation 5 and 2, the particles preferentially grow inside and outside, respectively. As shown by Mendez et al, 27 we consider that formation of particles in zone I of the dendrimer involves the -CONHsite, while that in zone II occurs with the amine or succinamic acid terminal site. Thus, binding of sulde ions on the Cd(II) or Zn(II)-dendrimer site is assumed to be an interaction through a single type of site.…”

On the incorrect use and interpretation of the model for colloidal, spherical crystal growth

“…Nanocrystals or chemically grown quantum dots have a wealth of uses, such as in solar cells, light emitting diodes, biological markers, optoelectronic devices and nanoelectronics [5,10,15]. It is estimated that semiconductor quantum dots may have a market value of over $4 billion by 2020 [2].…”

“…Peng et al [13] focus solely on the context of nanocrystal growth. In several nanocrystal studies [1,[3][4][5]10,15,17] the kinetic model is typically solved, subject to various assumptions, to obtain an expression for tðrÞ (the change of time with radius, since the function cannot be inverted to rðtÞ) and then the diffusion and surface kinetic coefficients obtained via comparison with experimental data. All are able to obtain good agreement to the data despite the fact different driving mechanisms (diffusion/surface kinetics) are assumed to dominate and distinct growth regimes are observed.…”