2 research outputs found
Using Prenucleation Aggregation of Caffeine-Benzoic Acid as a Rapid Indication of Co-crystallization from Solutions
Co-crystal
design is a convenient way to remedy the poor biopharmaceutical
properties of drugs. Most studies focus on experimental co-crystal
screening or computational prediction, but hardly any work has been
done toward fast, efficient, and reliable prediction of solution crystallization
for co-crystal formation. Here, we study the caffeine-benzoic acid
co-crystal system, due to its reported difficulty to crystallize from
the solution phase. With this work, we investigate whether there is
a link between prenucleation aggregation in solution and co-crystal
formation and how to harness this for crystallization prediction. 1H and 13C NMR spectroscopy is used to study the
prenucleation interaction between caffeine and benzoic acid in methanol,
acetone, and acetonitrile as examples of common solvents. In this
system, crystallization from methanol leads to no co-crystallization,
from acetone to concomitant crystallization of co-crystal and caffeine,
and from acetonitrile to pure co-crystal formation from solution.
Strong heteromeric dimers were found to exist in all three solvents.
Ternary phase diagrams were defined and a solution-accessible co-crystal
region was found for all solvents. For this system, the prenucleation
clusters found in solution could be linked to the crystallization
of the co-crystal. Crystallization from DMSO did not yield the co-crystal
and there were no detectable prenucleation aggregates. NMR spectroscopy
to probe dimers in solution can thus be used as a fast, reliable,
and promising tool to predict co-crystallization from specific solvents
and to screen for suitable solvents for manufacturing and scale-up
Thylakoid-Inspired Multishell g‑C<sub>3</sub>N<sub>4</sub> Nanocapsules with Enhanced Visible-Light Harvesting and Electron Transfer Properties for High-Efficiency Photocatalysis
Inspired
by the orderly stacked nanostructure and highly integrated
function of thylakoids in a natural photosynthesis system, multishell
g-C<sub>3</sub>N<sub>4</sub> (MSCN) nanocapsule photocatalysts have
been prepared by SiO<sub>2</sub> hard template with different shell
layers. The resultant triple-shell g-C<sub>3</sub>N<sub>4</sub> (TSCN)
nanocapsules display superior photocatalysis performance to single-shell
and double-shell counterparts owing to excellent visible-light harvesting
and electron transfer properties. Specially, with the increase of
the shell layer number, light harvesting is greatly enhanced. There
is an increase of the entire visible range absorption arising from
the multiple scattering and reflection of the incident light within
multishell nanoarchitectures as well as the light transmission within
the porous thin shells, and an increase of absorption edge arising
from the decreased quantum size effect. The electron transfer is greatly
accelerated by the mesopores in the thin shells as nanoconduits and
the high specific surface area of TSCN (310.7 m<sup>2</sup> g<sup>–1</sup>). With the tailored hierarchical nanostructure features,
TSCN exhibits a superior visible-light H<sub>2</sub>-generation activity
of 630 μmol h<sup>–1</sup> g<sup>–1</sup> (λ
> 420 nm), which is among one of the most efficient metal-free
g-C<sub>3</sub>N<sub>4</sub> photocatalysts. This study demonstrates
a bioinspired
approach to the rational design of high-performance nanostructured
visible-light photocatalysts