Colloidal Superparticles From Artificial Atoms - Molecular Self-Assembly: Advances and Applications - page 425

Figure 13.5 UV

−

vis spectral evolution for the 2 -mediated assembly of 1 /

Au ([ 1 /Au] = 0.1

µ

M,) with different r of 1 (A), 50 (B), 100 (C),

±

600 (D). ( 0.9 nm). The spectral evolutions were

recorded within the time frame of 30 min, and the arrows
shown in the graphs indicate the directions of the spectral
evolution versus time. From Ref. [28] with permission.

1 /Au) 5.1

13.3.3 Dipole-Dipole Interactions

−

Using dipole developed a

light-controlled synthesis for making colloidal superparticles.

dipole interactions, Grzybowski et al.

22,36

In this synthesis, gold nanocrystals were stabilized in

toluene/methanol solutions with excess dodecylamine and

didodecyldimethyl

−

ammonium, and then a photoactive trans-

′

azobenzene bis(11-mercaptoundecanoxy)

azobenzene, ADT) was added as a cross-linker to induce the
aggregation of gold nanocrystals and the formation of superparticles.
UV irradiation caused trans

dithiol ligand (4,4

−

cis isomerization of the ADT molecules
and induced a molecular dipole on the azobenzene unit. As a
consequence of the induction of cis-ADT dipoles, ADT-functionalized
gold nanocrystals aggregated and formed superparticles (Fig.
13.6). Interestingly, no particle aggregation was observed without
UV irradiation. This result suggests that dithiol cross-linking is
not a kinetically favored process, which is consistent with the
observation of Zhong

28

In addition, solvophobic interactions
induced by methanol were found important in the formation of
gold superparticles, which should be responsible for their spherical
shape that has a minimized surface energy.

et al.