238
aqueous colloidal suspensions under reaction conditions was established, indicating
that RaMe-β-cyclodextrin bearing optically active moieties acted as an efficient protective agent around the nanoparticle surface. In addition, the catalytic data showed
that, whatever the strategy, Ru nanoparticles stabilized by RaMe-β-cyclodextrin-trzLeu were more active than those capped by RaMe-β-cyclodextrin- trz-Ala (respectively, 100% vs. 54% of ethyl-2-hydroxypropanoate). However, no significant
enantiomeric excess was measured probably due to the weak or deficient interaction
between the chirally modified cyclodextrin and the nanoparticle surface.
The first work of Malta on the synthesis of palladium nanoparticles stabilized by
hydroxypropyl-α-cyclodextrin for catalytic applications was reported in 2009
(Senra et al. 2009). Interestingly, the authors reported that hydroxypropyl-αcyclodextrin could play several roles such as capping agent like the randomly methylated cyclodextrins or thiolated cyclodextrins but also as reducing agent. A black
precipitate was obtained after the addition of hydroxypropyl-α-cyclodextrin in an
aqueous PdCl 2 solution. The nanoparticles were characterized by several physicochemical techniques that revealed the formation of spherical particles in the size
range of 2–7 nm. Further analyses by FTIR spectroscopy and
1
H NMR did not show
covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that
hydroxypropyl-α-cyclodextrin was only physically adsorbed on the metal surface.
These observations were presumably due to hydrophobic interactions enabling the
limitation of the mutual coalescence of nanoclusters. The catalytic activity of these
colloids was evaluated in several Pd-catalyzed C-C coupling reactions, such as
Suzuki, Heck, and Sonogashira reactions, in water with good yields, and Pd
nanoparticles stabilized by hydroxypropyl-α-cyclodextrin were reused during four
consecutive runs without any significant loss of activity. More recently, the influence of the size of the hydroxypropyl cyclodextrin (α, β, γ) and the Pd-to-cyclodextrin
ratio was studied to observe eventual changes in the particle size of the resulting
particles and to exploit the surface/cavity effects in the Suzuki-Miyaura reaction
(Senra et al. 2016). The differences in catalytic activities between the Pd nanoparticles stabilized by different cyclodextrins were explained by the formation of inclusion complex, and the best activities were obtained with hydroxypropyl-βcyclodextrin which had the strongest complexation capacity.
The use of hydroxypropyl cyclodextrin as capping agent for the synthesis of silver nanoparticles was reported for the first time in 2013 (Devi and Mandal 2013). A
series of hydroxypropyl-cyclodextrin-capped Ag nanoparticles was synthesized by
the reduction of silver nitrate in alkaline aqueous medium at 60 °C. The resulting
nanoparticles were tested in the reduction of p-nitrophenol using sodium borohydride. The catalytic activity of hydroxypropyl-cyclodextrin-stabilized Ag nanoparticles was much higher than other cyclodextrin-capped nanoparticles. These
catalytic results were correlated with the size and morphology of the particles.
Whereas native α-cyclodextrin and β-cyclodextrin seemed to form aggregated nanostructures, hydroxypropyl cyclodextrin (α and β) formed a chain-like assembly.
A novel hybrid nanocomposite prepared from hydroxypropyl-β-cyclodextrin and
alginate was used as stabilizer to synthesize Ag nanoparticles (Nguyen et al. 2018).
Aqueous extract of J. subtriplinerve leaves was used as reducing agent in order to
S. Noël et al.
aqueous colloidal suspensions under reaction conditions was established, indicating
that RaMe-β-cyclodextrin bearing optically active moieties acted as an efficient protective agent around the nanoparticle surface. In addition, the catalytic data showed
that, whatever the strategy, Ru nanoparticles stabilized by RaMe-β-cyclodextrin-trzLeu were more active than those capped by RaMe-β-cyclodextrin- trz-Ala (respectively, 100% vs. 54% of ethyl-2-hydroxypropanoate). However, no significant
enantiomeric excess was measured probably due to the weak or deficient interaction
between the chirally modified cyclodextrin and the nanoparticle surface.
The first work of Malta on the synthesis of palladium nanoparticles stabilized by
hydroxypropyl-α-cyclodextrin for catalytic applications was reported in 2009
(Senra et al. 2009). Interestingly, the authors reported that hydroxypropyl-αcyclodextrin could play several roles such as capping agent like the randomly methylated cyclodextrins or thiolated cyclodextrins but also as reducing agent. A black
precipitate was obtained after the addition of hydroxypropyl-α-cyclodextrin in an
aqueous PdCl 2 solution. The nanoparticles were characterized by several physicochemical techniques that revealed the formation of spherical particles in the size
range of 2–7 nm. Further analyses by FTIR spectroscopy and
1
H NMR did not show
covalent bonds between cyclodextrins and palladium nanoparticles, suggesting that
hydroxypropyl-α-cyclodextrin was only physically adsorbed on the metal surface.
These observations were presumably due to hydrophobic interactions enabling the
limitation of the mutual coalescence of nanoclusters. The catalytic activity of these
colloids was evaluated in several Pd-catalyzed C-C coupling reactions, such as
Suzuki, Heck, and Sonogashira reactions, in water with good yields, and Pd
nanoparticles stabilized by hydroxypropyl-α-cyclodextrin were reused during four
consecutive runs without any significant loss of activity. More recently, the influence of the size of the hydroxypropyl cyclodextrin (α, β, γ) and the Pd-to-cyclodextrin
ratio was studied to observe eventual changes in the particle size of the resulting
particles and to exploit the surface/cavity effects in the Suzuki-Miyaura reaction
(Senra et al. 2016). The differences in catalytic activities between the Pd nanoparticles stabilized by different cyclodextrins were explained by the formation of inclusion complex, and the best activities were obtained with hydroxypropyl-βcyclodextrin which had the strongest complexation capacity.
The use of hydroxypropyl cyclodextrin as capping agent for the synthesis of silver nanoparticles was reported for the first time in 2013 (Devi and Mandal 2013). A
series of hydroxypropyl-cyclodextrin-capped Ag nanoparticles was synthesized by
the reduction of silver nitrate in alkaline aqueous medium at 60 °C. The resulting
nanoparticles were tested in the reduction of p-nitrophenol using sodium borohydride. The catalytic activity of hydroxypropyl-cyclodextrin-stabilized Ag nanoparticles was much higher than other cyclodextrin-capped nanoparticles. These
catalytic results were correlated with the size and morphology of the particles.
Whereas native α-cyclodextrin and β-cyclodextrin seemed to form aggregated nanostructures, hydroxypropyl cyclodextrin (α and β) formed a chain-like assembly.
A novel hybrid nanocomposite prepared from hydroxypropyl-β-cyclodextrin and
alginate was used as stabilizer to synthesize Ag nanoparticles (Nguyen et al. 2018).
Aqueous extract of J. subtriplinerve leaves was used as reducing agent in order to
S. Noël et al.