225
the polyol process. In addition, slight red shift compared with normal vibration
wavelength indicated the coordination of β-cyclodextrin onto the surface of the Ag
nanoparticles. Interestingly, the key parameters to get small particles with a narrow
distribution (pH value, temperature, and β-cyclodextrin/Ag molar ratio) are the
same as in the study of Qi concerning the gold nanoparticles. According to the
authors, not only the cyclodextrin deprotonation led to the formation and the stabilization of the silver nanoparticles but also the insoluble silver oxide formation in
alkaline medium which allowed a better control of the growth of the silver nanoparticles. The authors also found that the optimal synthesis temperature was 35 °C. The
intensity of absorption peak increased with the temperature, but very high temperature led to Ag 2 O decomposition and the loss of the control of the particle growth.
For the catalytic results, the authors suggested that H bonding interactions between
the cyclodextrin and the substrate are the key factor. These Ag nanoparticles that
were used in the catalytic reduction of 4-nitrophenol have proven to be more active
than traditional Ag nanoparticles stabilized by sodium citrate. This better catalytic
activity was explained by hydrogen bonds between 4-nitrophenol and the hydroxyl
groups of β-cyclodextrin which allowed a better diffusion of the substrate onto the
surface of Ag nanoparticles.
Another study developed γ-cyclodextrin-capped Ag nanoparticles for the
enhancement of the antibacterial efficiency of chloramphenicol (Gannimani et al.
2016). The formation of nanoparticles was confirmed by UV-Vis spectroscopy and
the appearance of the surface plasmon resonance band at 412 nm. The formation of
inclusion complexes was studied by
1
H NMR. The observed changes in the shifts
could be considered as direct evidence of the existence of host-guest non-covalent
interactions between γ-cyclodextrin and chloramphenicol. Moreover, an increase of
the antibacterial activity of chloramphenicol was observed when it was used in
combination with γ-cyclodextrin-capped Ag nanoparticles because of supramolecular interactions leading to the immobilization of chloramphenicol onto the Ag
nanoparticle surface.
Using simple, economical thermal pyrolysis approach and tin(II) stearate as ecofriendly organometallic precursor, SnO 2 quantum dots with mean diameters less
than 10 nm were synthesized (Haw et al. 2016) and used in both aqueous and nonaqueous media thanks to β-cyclodextrin employed for surface-ligand exchange. It
was suggested that the formation of inclusion complexes between stearate- stabilized
quantum dots and β-cyclodextrin could allow the phase transfer from the nonaqueous phase to the aqueous phase. Moreover, the use of the SnO 2 quantum dots
for the photocatalytic hydrogen gas evolution was studied and compared with commercial SnO 2 nanoparticles. The results demonstrated higher photocatalytic activity
of the former compared to the latter (~31.3% higher yield of hydrogen). The higher
photocatalytic activity of SnO 2 quantum dots was attributed to their smaller size,
higher surface area, and lower rates of photogenerated e
−
/h
+
recombination.
Noteworthy, β-cyclodextrin could enhance the surface moiety and the hydrophilicity of SnO 2 particles and consequently improve their dispersion in the aqueous
solution.
5 Metal Nanoparticles and Cyclodextrins for Catalytic Applications
the polyol process. In addition, slight red shift compared with normal vibration
wavelength indicated the coordination of β-cyclodextrin onto the surface of the Ag
nanoparticles. Interestingly, the key parameters to get small particles with a narrow
distribution (pH value, temperature, and β-cyclodextrin/Ag molar ratio) are the
same as in the study of Qi concerning the gold nanoparticles. According to the
authors, not only the cyclodextrin deprotonation led to the formation and the stabilization of the silver nanoparticles but also the insoluble silver oxide formation in
alkaline medium which allowed a better control of the growth of the silver nanoparticles. The authors also found that the optimal synthesis temperature was 35 °C. The
intensity of absorption peak increased with the temperature, but very high temperature led to Ag 2 O decomposition and the loss of the control of the particle growth.
For the catalytic results, the authors suggested that H bonding interactions between
the cyclodextrin and the substrate are the key factor. These Ag nanoparticles that
were used in the catalytic reduction of 4-nitrophenol have proven to be more active
than traditional Ag nanoparticles stabilized by sodium citrate. This better catalytic
activity was explained by hydrogen bonds between 4-nitrophenol and the hydroxyl
groups of β-cyclodextrin which allowed a better diffusion of the substrate onto the
surface of Ag nanoparticles.
Another study developed γ-cyclodextrin-capped Ag nanoparticles for the
enhancement of the antibacterial efficiency of chloramphenicol (Gannimani et al.
2016). The formation of nanoparticles was confirmed by UV-Vis spectroscopy and
the appearance of the surface plasmon resonance band at 412 nm. The formation of
inclusion complexes was studied by
1
H NMR. The observed changes in the shifts
could be considered as direct evidence of the existence of host-guest non-covalent
interactions between γ-cyclodextrin and chloramphenicol. Moreover, an increase of
the antibacterial activity of chloramphenicol was observed when it was used in
combination with γ-cyclodextrin-capped Ag nanoparticles because of supramolecular interactions leading to the immobilization of chloramphenicol onto the Ag
nanoparticle surface.
Using simple, economical thermal pyrolysis approach and tin(II) stearate as ecofriendly organometallic precursor, SnO 2 quantum dots with mean diameters less
than 10 nm were synthesized (Haw et al. 2016) and used in both aqueous and nonaqueous media thanks to β-cyclodextrin employed for surface-ligand exchange. It
was suggested that the formation of inclusion complexes between stearate- stabilized
quantum dots and β-cyclodextrin could allow the phase transfer from the nonaqueous phase to the aqueous phase. Moreover, the use of the SnO 2 quantum dots
for the photocatalytic hydrogen gas evolution was studied and compared with commercial SnO 2 nanoparticles. The results demonstrated higher photocatalytic activity
of the former compared to the latter (~31.3% higher yield of hydrogen). The higher
photocatalytic activity of SnO 2 quantum dots was attributed to their smaller size,
higher surface area, and lower rates of photogenerated e
−
/h
+
recombination.
Noteworthy, β-cyclodextrin could enhance the surface moiety and the hydrophilicity of SnO 2 particles and consequently improve their dispersion in the aqueous
solution.
5 Metal Nanoparticles and Cyclodextrins for Catalytic Applications