Chirality strong promise for further developments in chiral

Chirality is a very significant factor in molecular recognition processes, which have many uses in chemical and biological systems. Chiral
compounds are extremely important in chemistry, biology and medicine and
discovering new efficient methods to produce, control, identify and
separate pure chiral compounds is critical for further developments in many fields such as pharmaceuticals and agrochemicals. (refs) The
synthesis and separation of chiral compounds are a significant challenge in
chemical processing, playing key roles in chemical industry. In recent years, the
research on chirality at the nanoscale has been very relevant. (refs) It was shown that different nano-systems, such as chiroptical
molecular switches, (ref) chiral nanosurfaces,1,2 chiral nanoparticles, (ref)
and chiral mesoporous materials3–5 can be useful in chirality. Overall, the areas
of chiral nanotechnology show an exceptionally strong promise for further developments
in chiral catalysts, bio-recognition and chiral separation processes. Inorganic chiral systems?

In this article, we present for the first time the synthesis and
application of a new class of chiral nanosystem based on
chiral silica colloidosomes. Colloidosomes are capsules (micro or
nanosized) whose shells consist of coagulated or fused colloid particles. In
recent years, colloidosomes received extensive attention mainly because of
their great potential significance in many areas and particularly in chemical
and biological microencapsulation. The use of colloidosomes for
microencapsulation allows the controlled release of active ingredients in
various applications such as agrochemicals, medicine,6 cosmetics, food, and polymers.7 (refs) Generally, the preparation of colloidosomes is based on the self-assembly
of inorganic colloidal particles, mostly silica, at the interface between two
immiscible liquids, typically oil and water. This self-assembled process is
known as Pickering emulsion and has been used for several purposes. (refs) For example, Zhu et al. showed the use of silica
colloidosomes for the microencapsulation of hydrophobic liquids,8 and synthesized colloidosomes with a particle-bilayer shell in a
w/o Pickering emulsion.9 The interfacial assembly of the particles is driven by a decrease
in the total free energy upon the placement of a particle at the fluid/fluid
interface.10–14 The droplet template defines the size of the colloidosome and the
pores between the particles determine its permeability.14 Moreover, the mechanical properties of the colloidosome
shell depend on the morphology and the nature of the colloidal particles
assembling it.15,7 The synthesis of colloidosomes in Pickering emulsion is simple and
low-cost. Colloidosomes are appropriate for various microencapsulation
applications, such as formulations of smart coatings in food and pharma
industries.16

In this article, we introduce a new design
for chiral colloidosomes that is based on the
use of chiral silica nanoparticles for the preparation of chiral colloidosomes. The overall process for the synthesis of chiral colloidosomes is shown in Figure 1.  In the first step we
prepared chiral silica nanoparticles by combine 85%
tetraethyl
orthosilicate (TEOS) and 15% chiral (S)-N-1-phenylethyl-N’-triethoxysilylpropylurea
(PEPU) as the silica precursors in order to produce chiral silica nanoparticles.
In the
next step, we used o/w Pickering emulsion process for the formation of the colloidosomes that are stabilized
by chiral silica nanoparticles, with polydiethoxysiloxane (PDEOS) as silica
precursor polymer for binding the chiral nanoparticles to the interface of the colloidosomes.

Combining chiral recognition with
the beneficial properties of colloidosomes can be highly pertinent for
enantioselective processes, such as catalysis and production of
enantiomerically pure. Colloidosomes formed by Pickering emulsions have great
potential in chiral applications because of their high surface area and degree
of control increasing the chiral surface accessibility for enantioselective
objectives.

Chiral silica colloidosomes could
be useful in the encapsulation of aggressive chiral fluids because of the high
chemical and thermal stability of silica.