256
90R4 solution at 40 °C leading to the formation of Au nanoparticles where poloxamine played the role of the reducing agent. After heating of this solution,
α-cyclodextrin was added to the colloidal suspension, and after cooling down to
room temperature, Au nanoparticles were incorporated into α-cyclodextrin/
Tetronic
®
90R4 hydrogel. The addition of α-cyclodextrin was very important
because it allowed the formation of the supramolecular hydrogel coming from the
sliding of α-cyclodextrin along the copolymer chain. Moreover, by repeating heating/cooling cycles, the authors clearly showed that the presence of α-cyclodextrin
improved the long-term stability of the Au nanoparticles by additional steric stabilization effects. Colloidal suspensions were synthesized considering Au concentration ranging from 0.1 mM to 2 mM. No significant influence of the Au concentration
was noticed on the final mean diameters of Au nanoparticles always centered around
7 nm. The catalytic activity of the colloidal suspension prepared with Au concentration of 0.5 mM was particularly studied in the hydrogenation of terminal and internal alkenes and also alkynes under mild experimental conditions. Conversions were
ranging from 5% to 54% depending on the nature of the substrate. The recyclability
study was also realized in the styrene hydrogenation, and Au nanoparticles could be
reused during five successive runs without any loss of activity, showing as well the
robustness of this kind of catalytic system.
Ag nanoparticles were synthesized into thermosensitive poly(NIPAAm-coAMPS) hydrogels by chemical reduction of silver nitrate with sodium borohydride
(Wang et al. 2016c). Small-sized Ag nanoparticles were homogeneously dispersed
into this hydrogel with a mean diameter centered on 3.5 nm. In this study, the silver
colloidal suspensions were used in the catalytic reduction of 4-nitrophenol, and
α-cyclodextrin was added before the catalytic test. The catalytic activity of Ag
nanoparticles was better in the presence of α-cyclodextrin, and it was explained by
the formation of an inclusion complex between the cyclodextrin and the substrate
and a decrease of the activation energy.
Jia et al. (2015) reported a simple method for the immobilization of catalytically
active gold nanoparticles in acrylate α-cyclodextrin-modified poly(Nvinylcaprolactam) microgels. According to transmission electron microscopy
images, monodispersed gold nanoparticles with an average diameter of 5–6 nm
were obtained without addition of any reducing agent. The reduction of the gold
ions can be explained by the presence of the hydroxyl groups of poly(Nvinylcaprolactam) microgels. The homogeneous distribution of the particles could
be attributed to the acrylate α-cyclodextrin through the capping efficiency on the
surface of the gold particles due to the carboxylate-gold interactions. The immobilization of the gold particles did not influence the swelling-deswelling properties of
the microgels. The poly(N-vinylcaprolactam)-α-cyclodextrin gold composite particles showed efficient catalytic activity for the reduction of aromatic nitro compounds. The host-guest capacity of cyclodextrin was proven through the reduction
of p-nitrophenol, and the catalytic activity was much higher than in the case of
dimethyl-p-nitrophenol.
In the same way, a thermosensitive catalytic system based on silver nanoparticles
immobilized into a network of poly(NIPAAm-co-AMPS) hydrogels was studied
S. Noël et al.
90R4 solution at 40 °C leading to the formation of Au nanoparticles where poloxamine played the role of the reducing agent. After heating of this solution,
α-cyclodextrin was added to the colloidal suspension, and after cooling down to
room temperature, Au nanoparticles were incorporated into α-cyclodextrin/
Tetronic
®
90R4 hydrogel. The addition of α-cyclodextrin was very important
because it allowed the formation of the supramolecular hydrogel coming from the
sliding of α-cyclodextrin along the copolymer chain. Moreover, by repeating heating/cooling cycles, the authors clearly showed that the presence of α-cyclodextrin
improved the long-term stability of the Au nanoparticles by additional steric stabilization effects. Colloidal suspensions were synthesized considering Au concentration ranging from 0.1 mM to 2 mM. No significant influence of the Au concentration
was noticed on the final mean diameters of Au nanoparticles always centered around
7 nm. The catalytic activity of the colloidal suspension prepared with Au concentration of 0.5 mM was particularly studied in the hydrogenation of terminal and internal alkenes and also alkynes under mild experimental conditions. Conversions were
ranging from 5% to 54% depending on the nature of the substrate. The recyclability
study was also realized in the styrene hydrogenation, and Au nanoparticles could be
reused during five successive runs without any loss of activity, showing as well the
robustness of this kind of catalytic system.
Ag nanoparticles were synthesized into thermosensitive poly(NIPAAm-coAMPS) hydrogels by chemical reduction of silver nitrate with sodium borohydride
(Wang et al. 2016c). Small-sized Ag nanoparticles were homogeneously dispersed
into this hydrogel with a mean diameter centered on 3.5 nm. In this study, the silver
colloidal suspensions were used in the catalytic reduction of 4-nitrophenol, and
α-cyclodextrin was added before the catalytic test. The catalytic activity of Ag
nanoparticles was better in the presence of α-cyclodextrin, and it was explained by
the formation of an inclusion complex between the cyclodextrin and the substrate
and a decrease of the activation energy.
Jia et al. (2015) reported a simple method for the immobilization of catalytically
active gold nanoparticles in acrylate α-cyclodextrin-modified poly(Nvinylcaprolactam) microgels. According to transmission electron microscopy
images, monodispersed gold nanoparticles with an average diameter of 5–6 nm
were obtained without addition of any reducing agent. The reduction of the gold
ions can be explained by the presence of the hydroxyl groups of poly(Nvinylcaprolactam) microgels. The homogeneous distribution of the particles could
be attributed to the acrylate α-cyclodextrin through the capping efficiency on the
surface of the gold particles due to the carboxylate-gold interactions. The immobilization of the gold particles did not influence the swelling-deswelling properties of
the microgels. The poly(N-vinylcaprolactam)-α-cyclodextrin gold composite particles showed efficient catalytic activity for the reduction of aromatic nitro compounds. The host-guest capacity of cyclodextrin was proven through the reduction
of p-nitrophenol, and the catalytic activity was much higher than in the case of
dimethyl-p-nitrophenol.
In the same way, a thermosensitive catalytic system based on silver nanoparticles
immobilized into a network of poly(NIPAAm-co-AMPS) hydrogels was studied
S. Noël et al.