The inherent amphiphilicity of the Ir−Cb ADDC provides
an opportunity for itself to self-assemble into nanoparticles in
water. To determine the size and morphology of the selfassembled nanoparticles, a dimethyl sulfoxide (DMSO)
solution of the Ir−Cb ADDC was added dropwise into water,
followed by dialysis against water to remove DMSO. A stable
and bluish solution with the final Ir−Cb conjugate concentration of 0.5 mg mL−1 was obtained. Figure 2c gives the
dynamic light scattering (DLS) curve of Ir−Cb ADDC aqueous
solution with a concentration of 0.5 mg mL−1
, indicating the
formation of aggregates with a narrow unimodal distribution
and an average hydrodynamic diameter of approximate 88.3
nm. The surface charge of the Ir−Cb ADDC solution was also
investigated by DLS. The result shows that the value of zetapotential is positive (+3.4) in phosphate buffer solution (PBS)
(pH 7.4). The morphology of the aggregates was observed by
transmission electron microscopy (TEM). The TEM image in
Figure 2d shows the spherical nanoparticles with an average
size of approximate 75.7 nm. This size is slightly smaller than
that measured by DLS due to the shrinkage of nanoparticles in
a drying state during TEM sample preparation. The inset of
Figure 2d presents a typical enlarged TEM image of one
nanoparticle, which clearly indicates that the nanoparticle
consists of a lot of small spherical domains. These small
domains are around 3.4 nm according to the statistical analysis
of 50 samples, which supports that the small domains are
conventional micelles self-assembled from Ir−Cb ADDCs since
each ADDC is around 2 nm in size through simulations. Thus,
the as-prepared nanoparticles are formed through the
secondary aggregation of small micelles from ADDCs, which
is similar to the small micelle aggregate (SMA) mechanism37,38
or multicompartment micelle mechanism.39 The detailed selfassembly mechanism is given in Supporting Information Figure
S5. The DLS measurements at different time intervals
demonstrated that the stability of Ir−Cb ADDC nanoparticles