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Y. Min et al.
Thiolate-encapsulated gold NP assembled as thin films on electrodes were efficient catalysts for the electrooxidation of CO [70]. Decanethiolate was used to
produce 2 and 5 nm Au NP on glassy carbon electrodes by cross-linking with 1,9nonanedithiol. The 2 nm Au NP are more active for CO oxidation than the 5 nm Au
NP. The same authors further studied the 2 nm Au assembled NP, by investigating
the effect of the number of layers deposited (up to 20) on different supports (glassy
carbon and carbon black), in the electrooxidation of CO, MeOH and, electroreduction of oxygen [45]. Similarly, AuPt NP were used as electrocatalyst for MeOH
oxidation [71].
Azide- and alkyne-terminated groups have been used to produce covalent
networks by click chemistry and LBL, allowing the production of assemblies of Au
NPs onto several surfaces (Fig. 5.36) [111]. Alkyne-functionalized substrates (titania,
silica, tin oxide, glass, stainless steel substrates) were immersed in a 3.5 wt% solution
of azide-functionalized NP in THF for 12 h, and then immersed in an aqueous solution of copper sulfate and ascorbic acid for another 6 h to catalyze the click reaction.
To produce multilayers, the Au NP assembly was subsequently soaked in an alkynefunctionalized NP suspension as many times as required. The authors point out that
the growth rate of the monolayer was inversely proportional to the size of the NP and
the density of the particles depended on the solvent, as well as on the substrate, being
higher on TiO 2 . Cyclic voltammetry profiles (up to 150 cycles) performed during
methanol electrooxidation with the Au NP monolayers on silica, titania, ITO, and
stainless steel substrates in electrolyte solution (0.1 M NaOH + 2.5 M MeOH) have
confirmed the high stability of the catalytic systems. The same catalytic systems have
been also tested in water splitting and photocatalytic degradation of Rhodamine B
dye.
Miscellaneous Reactions
Au NP deposited onto several surfaces discussed above (Fig. 5.36) were active catalysts for the electrochemical water splitting [111]. The onset potential at approximately 0.7 V (vs. SCE) for all four monolayer Au NP assemblies on silicon, titania,
ITO, and stainless steel substrates shows the oxygen-evolution current at approximately 0.6, 11, 2.3, and 45 mA/cm
2 , respectively, which is higher than that of the
bare substrates. The authors claim that the overall current density is dependent on the
NP density, the electrocatalytic activity of the substrate, and the metal-NP support
interactions (Fig. 5.37). The comparison of these systems to other Au NP based
catalysts pointed out a positive effect of the assemblies in terms of stability.
Photocatalytic water splitting was investigated by using CdSe NP assemblies as
catalyst [203]. Capped oleylamine/thiol Au, Pd, Pt, CdSe NP can form NP assemblies
by the photo-oxidation of the capping thiol ligands. The assemblies consisted of
vesicles, the size of which could be tuned by the size of the NP, and the thickness
(number of NP layers) by the solvents used. Indeed, the type and the polarity of the
solvent are crucial in the formation of the vesicles by light. Concerning the catalytic
properties, the photocatalytic rate using the prepared CdSe nanovesicles was 1.5
times of that using individual CdSe NP, due to the enhanced light absorption of the
assembly. Also, the catalytic activity remained unchanged after 10 h of visible light
Y. Min et al.
Thiolate-encapsulated gold NP assembled as thin films on electrodes were efficient catalysts for the electrooxidation of CO [70]. Decanethiolate was used to
produce 2 and 5 nm Au NP on glassy carbon electrodes by cross-linking with 1,9nonanedithiol. The 2 nm Au NP are more active for CO oxidation than the 5 nm Au
NP. The same authors further studied the 2 nm Au assembled NP, by investigating
the effect of the number of layers deposited (up to 20) on different supports (glassy
carbon and carbon black), in the electrooxidation of CO, MeOH and, electroreduction of oxygen [45]. Similarly, AuPt NP were used as electrocatalyst for MeOH
oxidation [71].
Azide- and alkyne-terminated groups have been used to produce covalent
networks by click chemistry and LBL, allowing the production of assemblies of Au
NPs onto several surfaces (Fig. 5.36) [111]. Alkyne-functionalized substrates (titania,
silica, tin oxide, glass, stainless steel substrates) were immersed in a 3.5 wt% solution
of azide-functionalized NP in THF for 12 h, and then immersed in an aqueous solution of copper sulfate and ascorbic acid for another 6 h to catalyze the click reaction.
To produce multilayers, the Au NP assembly was subsequently soaked in an alkynefunctionalized NP suspension as many times as required. The authors point out that
the growth rate of the monolayer was inversely proportional to the size of the NP and
the density of the particles depended on the solvent, as well as on the substrate, being
higher on TiO 2 . Cyclic voltammetry profiles (up to 150 cycles) performed during
methanol electrooxidation with the Au NP monolayers on silica, titania, ITO, and
stainless steel substrates in electrolyte solution (0.1 M NaOH + 2.5 M MeOH) have
confirmed the high stability of the catalytic systems. The same catalytic systems have
been also tested in water splitting and photocatalytic degradation of Rhodamine B
dye.
Miscellaneous Reactions
Au NP deposited onto several surfaces discussed above (Fig. 5.36) were active catalysts for the electrochemical water splitting [111]. The onset potential at approximately 0.7 V (vs. SCE) for all four monolayer Au NP assemblies on silicon, titania,
ITO, and stainless steel substrates shows the oxygen-evolution current at approximately 0.6, 11, 2.3, and 45 mA/cm
2 , respectively, which is higher than that of the
bare substrates. The authors claim that the overall current density is dependent on the
NP density, the electrocatalytic activity of the substrate, and the metal-NP support
interactions (Fig. 5.37). The comparison of these systems to other Au NP based
catalysts pointed out a positive effect of the assemblies in terms of stability.
Photocatalytic water splitting was investigated by using CdSe NP assemblies as
catalyst [203]. Capped oleylamine/thiol Au, Pd, Pt, CdSe NP can form NP assemblies
by the photo-oxidation of the capping thiol ligands. The assemblies consisted of
vesicles, the size of which could be tuned by the size of the NP, and the thickness
(number of NP layers) by the solvents used. Indeed, the type and the polarity of the
solvent are crucial in the formation of the vesicles by light. Concerning the catalytic
properties, the photocatalytic rate using the prepared CdSe nanovesicles was 1.5
times of that using individual CdSe NP, due to the enhanced light absorption of the
assembly. Also, the catalytic activity remained unchanged after 10 h of visible light