Yolk nanostructures

A single Au nanoparticle inside the pNIPAM shell catalytic system, a so-called hybrid yolk-shell nanostructure, was synthesised as shown in Fig. 13.9 (Wu et al, 2012). This system showed catalytic activity in the reduction of 4-nitrophenol and nitrobenzene with NaBH, in which the selectivity of hydrogenation depended on temperature. The reduction of 4-nitrophenol was much faster at lower temperature, whereas nitrobenzene reacted faster at higher temperature. Both compounds are of similar size thus the changes in pNIPAM core conformation from a swollen to a shrunken state could not affect the diffusion of the reactants through the pNIPAM core. However, 4-nitrophenol is more hydrophilic than nitrobenzene. The interaction of the reactants with pNIPAM in its hydrophilic and hydrophobic state could be a reason for the temperature dependence of the selectivity of catalysis. 

Fig. 5.1 Schematic representations of three types of stable nanocatalysts (a) core-shell and (b) yolk-shell nanostructures, (c) Supported catalysts covered with a shell layer...

The yolk-shell nanostructure is a modified form of the core-shell configuration. The yolk-shell structure is distinguished from the core-shell structure in that the former has a hollow inner space between the core and the shell layers. Compared to... 

Fig. 5.13 (a) Schematic representation of the growth procedure, (b) SEM and (c, d) TEM images for the nanocrystal ZIF-8 yolk-sheU nanostructures. The cores are Pd octahedra with edge sizes of 60 nm, and the shells are microporous ZlF-8 with a thickness of 100 nm. (e) Schematic sketch of the final yolk-sheU nanostructure. Adapted from ref. [63]... 

Yin Y, Rioux RM, Erdonmez CK, Hughes S, Somoijai GA, Alivisatos AP (2(X)4) Formation of hollow nanocrystals through the nanoscale KirkendaU effect. Science 304 711-714 Park JC, Song HJ (2010) Metal silica yolk-shell nanostructures as versatile bifunctional... 

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