Surfactant nucleation and orientation of crystals in the syntheses of metal sulfides in a polymer matrix

Fabrication of PbS microstructures with different shapes in aqueous solutions of amphiphilic triblock copolymer

“…The above results indicate that the size of F127 micelles is significantly increased after the addition of Pb(Ac) 2 . The resulting large spherical aggregates could be ascribed to the complexation of Pb 2+ with the EO units, as confirmed by the fact that the EO units of poly (ethylene oxide) (PEO, M w ¼ 200.000) can form hydrogen bond with Pb 2+ in a PEO film [34,35]. It is noted that the presence of Pb(Ac) 2 is unnecessary for the formation of micelles, and the TEM image of complex F127 micelles with Pb 2+ is only used to characterize the formation process.…”

“…With increasing F127 concentration, the average size of the branch-like structures reduces, but their compactness degree increases. It has been revealed that Pb 2+ ions can bind to the EO chains of the monomolecular F127 by hydrogen bonds [35,36]. The reaction of Pb 2+ ions with the S 2À ions results in the formation of a monomeric Pb 2+ -F127 aggregate, then the aggregation and growth of PbS nuclei, based on the hydrophilic interaction of EO chains and the hydrophobic interaction of PO chains, result in the formation of branch-like structures.…”

“…The chain conformation of block copolymer monomers can be adjusted by changing the experimental conditions, such as the block copolymer concentration, reaction temperature, which may provide rich structure-directing matrixes for the shape control of functional materials. Furthermore, the metal ions with low degree of hydration, such as Pb 2+ , have less strong binding by EO units in comparison with those with high degree of hydration, such as Zn 2+ , and Cd 2+ [34,35], it is therefore difficult to form various sulfide microstructures by block copolymer micelles with relatively short EO chains. On these grounds, we proposed a controlled synthesis of PbS in F127 solutions.…”

Formation of Metastable Vaterite Crystals in a Polymer Matrix by Gaseous Diffusion

“…There are reports where crystallizing an inorganic phase inside a polymer has produced high-pressure phases of cadmium sulfide 19 , novel and high-pressure phases of lead sulfide 20 and in one instance the formation of crystalline lithium niobate without the application of heat 21 . It is suggested that "the density or rigidity of the matrix regulates the phase of the crystals that form, predominantly by a "solid state" densification effect, whereby the solid state of the polymer matrix acts to confine growth spatially such that the growing crystal is forced to adopt a more dense form than it would in solution growth, resulting in the formation of high-pressure phases" 22 . In this work, however, this is unlikely to be the explanation for vaterite formation, for two reasons.…”

Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides

“…Cates et al . reported a biomimetic in situ synthesis of metal sulfides/polymer composites [ 85 ]. The surfactants used were suggested to mimic the soluble proteins found in biological systems, which have been shown to assemble at the surfaces of the polymer composite films, significantly affect nucleation and orientation of the growing crystals within the solid polymer composite films.…”