156
Y. Min et al.
amino groups is established depending on the pH. To carry out the cross-linking
reaction, the Au NP have to be brought close enough to one another. To do so, the
Au NP are transferred from the bulk aqueous phase to the oil–water interface that
takes place only at specific (basic) pH levels. This technique allows the formation of
freestanding monolayer of covalently bonded Au NP at the water–oil interface.
Azo (–N=N–) or amido (CONH) linkages were also used to covalently attach gold
and CdS NPs (Fig. 5.20a) [118]. These reactions were carried out under very dilute
conditions to control the assembly and avoid the polymerization. Indeed, at high
ligand concentrations, the NP formed a network of chains for both amido- and azofunctionalized particles. Gold NP (1.2 nm)-CdSe–ZnS quantum dots (5.6, 6.8, and
7.8 nm) assemblies were formed via covalent coupling of carboxyl-functionalized
Au NP, which were activated with N-hydroxysuccinimide, with amine-functionalized
quantum dots [119].
Esterification reactions were used for the covalent binding of OH-terminated
(polyvinylalcool, PVA) Ag NP (10.4 nm) by means of dicarboxylic acids (oxalic,
l-(+)-tartaric, d-glucaric acid and sebacic acid) with a defined molecular length [98].
PVA plays a key role in this reaction because it is the reducing agent of Ag
I , the
surface stabilizer of the resulting NP, and acts as a mild Lewis acid that can exhibit
oxophilic character toward the carbonyl group, which forms the basis for the catalysis
Fig. 5.20 a Azo and amido linkage. Reproduced with permission from Ref. [118]. b Ester coupling.
Reproduced with permission from Ref. [120]. c Oxidative acetylene coupling for the assembly of
Au NP. Reproduced with permission from Ref. [94]
Y. Min et al.
amino groups is established depending on the pH. To carry out the cross-linking
reaction, the Au NP have to be brought close enough to one another. To do so, the
Au NP are transferred from the bulk aqueous phase to the oil–water interface that
takes place only at specific (basic) pH levels. This technique allows the formation of
freestanding monolayer of covalently bonded Au NP at the water–oil interface.
Azo (–N=N–) or amido (CONH) linkages were also used to covalently attach gold
and CdS NPs (Fig. 5.20a) [118]. These reactions were carried out under very dilute
conditions to control the assembly and avoid the polymerization. Indeed, at high
ligand concentrations, the NP formed a network of chains for both amido- and azofunctionalized particles. Gold NP (1.2 nm)-CdSe–ZnS quantum dots (5.6, 6.8, and
7.8 nm) assemblies were formed via covalent coupling of carboxyl-functionalized
Au NP, which were activated with N-hydroxysuccinimide, with amine-functionalized
quantum dots [119].
Esterification reactions were used for the covalent binding of OH-terminated
(polyvinylalcool, PVA) Ag NP (10.4 nm) by means of dicarboxylic acids (oxalic,
l-(+)-tartaric, d-glucaric acid and sebacic acid) with a defined molecular length [98].
PVA plays a key role in this reaction because it is the reducing agent of Ag
I , the
surface stabilizer of the resulting NP, and acts as a mild Lewis acid that can exhibit
oxophilic character toward the carbonyl group, which forms the basis for the catalysis
Fig. 5.20 a Azo and amido linkage. Reproduced with permission from Ref. [118]. b Ester coupling.
Reproduced with permission from Ref. [120]. c Oxidative acetylene coupling for the assembly of
Au NP. Reproduced with permission from Ref. [94]