posted on 2017-09-10, 00:00authored byWei Xue, Hengquan Yang, Zhiping Du
Pickering
emulsions exhibit outstanding stability, especially those
prepared with Janus particles, whose desorption energy is expected
to be up to 3-fold greater than emulsions of homogeneous particles
from theoretical calculations. To the best of our knowledge, however,
there remains no experimental proof of this behavior in practice.
In this study, inorganic Janus nanoparticles were fabricated by regioselective
modification of the separate side of SiO2 nanoparticles
with a judiciously selected mixture of trimethoxysilylpropyldiethylenetriamine
and n-octyltrimethoxysilane. Janus nanoparticles
demonstrated excellent interfacial activity, forming Pickering emulsions
with oil phases at oil–water interfacial tensions ranging from
6.6–52.8 mN m–1. Furthermore, as the interface
of the Janus nanoparticles was regionally functionalized with −NH2 groups, phase inversion could be realized by tuning pH. This
is the first example for the Pickering emulsions stabilized with inorganic
Janus particles. Importantly, based on the results of centrifugation
experiment, the desorption energy of Janus nanoparticles at the interface
was 3.2 times larger than that of homogeneous nanoparticles, which
is in accordance with the result from theoretical calculations. These
experimental results will substantially enrich our understanding of
Janus nanoparticle Pickering emulsions and their interfacial assembly
behavior.