272
electroreduction in a 0.1 M H 2 SO 4 solution under several atmospheres. According
to the voltammetric data, the Au nanoparticles supported on 4-ATP_β-CDP/rGO
showed a good activity toward oxygen reduction. The catalytic activity increased
with the Au nanoparticle loading.
Immobilized gold nanoparticles (Fe 3 O 4 @Au) were synthesized through a selfassembly route between thiolated-β-cyclodextrin gold nanoparticles and ferrocenylfunctionalized iron oxide Fe 3 O 4 nanoparticles (Qu et al. 2018). This catalyst showed
a high catalytic activity in the reduction of 4-nitrophenol in comparison of control
experiments. The Fe 3 O 4 @Au ensured good recyclability by an easy recovery due to
the magnetic properties of the support and by keeping the catalytic activity even
after ten runs. The catalyst could be disassembled via redox properties by using
hydrogen peroxide. This latter oxidizes the ferrocenyl moiety, and the corresponding oxidized product could not interact with the cyclodextrin cavity, leading to the
disassembly process.
Combining the advantages of click chemistry and supramolecular assembly, Li
et al. (2016) developed a novel hybrid nanocatalyst containing a movable platinum
nanocluster encapsulated in temperature- and pH-responsive polymer brushes decorated through a template-assisted protocol. The authors studied the catalytic activity
of the inorganic-polymer nanocomposite for the reduction of 4-nitrophenol in the
presence of NaBH 4 . The results established the high catalytic activity and reusability of the catalyst. It is suggested that the hairy hybrid nanorattles which contained
the hydrophilic poly(N-vinylcaprolactam) brushes on their surface could improve
the dispersion in the aqueous media. Notably, diverse catalysts of this type could be
prepared by altering the thickness of P[MAA-co-(PMA-click-β-cyclodextrin)] shell
and the length of poly(N-vinylcaprolactam) brushes and changing the size of SiO 2
intertemplate layer during the sol-gel process into a cross-linked β-cyclodextrin
polymer network.
5.4 Conclusion
This chapter has highlighted several historical roles of the cyclodextrin in catalysis
using metal nanoparticles as active phase; whatever the nature of the catalyst, it
means solvent-dispersed nanoparticles or nanoparticles immobilized on a support.
Indeed, cyclodextrin as stabilizing agent of metal nanocatalyst has been widely
studied since the first study of Komiyama and Hirai in 1983. The stability, the catalytic activity, and the recyclability of the resulting nanoparticles have been improved
by using more complex cyclodextrin-based protective agents. From the first studies
using native cyclodextrins to cyclodextrin-based polymers or rotaxanes, native and
functionalized cyclodextrins have proven their ability to protect metal nanoparticles
against agglomeration via different stabilizing properties (electrostatic, steric, and
electrosteric). Most of the examples reported in this chapter clearly showed that
cyclodextrin-based systems have improved both the average size decrease and the
dispersion of the metal nanoparticles in comparison to their free cyclodextrin
S. Noël et al.
electroreduction in a 0.1 M H 2 SO 4 solution under several atmospheres. According
to the voltammetric data, the Au nanoparticles supported on 4-ATP_β-CDP/rGO
showed a good activity toward oxygen reduction. The catalytic activity increased
with the Au nanoparticle loading.
Immobilized gold nanoparticles (Fe 3 O 4 @Au) were synthesized through a selfassembly route between thiolated-β-cyclodextrin gold nanoparticles and ferrocenylfunctionalized iron oxide Fe 3 O 4 nanoparticles (Qu et al. 2018). This catalyst showed
a high catalytic activity in the reduction of 4-nitrophenol in comparison of control
experiments. The Fe 3 O 4 @Au ensured good recyclability by an easy recovery due to
the magnetic properties of the support and by keeping the catalytic activity even
after ten runs. The catalyst could be disassembled via redox properties by using
hydrogen peroxide. This latter oxidizes the ferrocenyl moiety, and the corresponding oxidized product could not interact with the cyclodextrin cavity, leading to the
disassembly process.
Combining the advantages of click chemistry and supramolecular assembly, Li
et al. (2016) developed a novel hybrid nanocatalyst containing a movable platinum
nanocluster encapsulated in temperature- and pH-responsive polymer brushes decorated through a template-assisted protocol. The authors studied the catalytic activity
of the inorganic-polymer nanocomposite for the reduction of 4-nitrophenol in the
presence of NaBH 4 . The results established the high catalytic activity and reusability of the catalyst. It is suggested that the hairy hybrid nanorattles which contained
the hydrophilic poly(N-vinylcaprolactam) brushes on their surface could improve
the dispersion in the aqueous media. Notably, diverse catalysts of this type could be
prepared by altering the thickness of P[MAA-co-(PMA-click-β-cyclodextrin)] shell
and the length of poly(N-vinylcaprolactam) brushes and changing the size of SiO 2
intertemplate layer during the sol-gel process into a cross-linked β-cyclodextrin
polymer network.
5.4 Conclusion
This chapter has highlighted several historical roles of the cyclodextrin in catalysis
using metal nanoparticles as active phase; whatever the nature of the catalyst, it
means solvent-dispersed nanoparticles or nanoparticles immobilized on a support.
Indeed, cyclodextrin as stabilizing agent of metal nanocatalyst has been widely
studied since the first study of Komiyama and Hirai in 1983. The stability, the catalytic activity, and the recyclability of the resulting nanoparticles have been improved
by using more complex cyclodextrin-based protective agents. From the first studies
using native cyclodextrins to cyclodextrin-based polymers or rotaxanes, native and
functionalized cyclodextrins have proven their ability to protect metal nanoparticles
against agglomeration via different stabilizing properties (electrostatic, steric, and
electrosteric). Most of the examples reported in this chapter clearly showed that
cyclodextrin-based systems have improved both the average size decrease and the
dispersion of the metal nanoparticles in comparison to their free cyclodextrin
S. Noël et al.