During
the last two decades, the synthesis of silica with an ordered mesoporous
structure has been thoroughly explored. The basis of the synthesis is to let
silica monomers polymerize in the presence of an amphiphilic template
component. In the first studies, cationic surfactants were used as structure
inducer. Later it was shown that pluronic copolymers also could have the role.
One advantage with the pluronics copolymers is that they allow for a wider
variation in the radius of pores in the resulting silica material. Another
advantage lies in the higher stability resulting from the thicker walls between
the pores. Mesoporous silica has a very high area to volume ratio, and the
ordered structure ensures surface homogeneity. There are a number of
applications of this type of material. It can be used as support for catalysts,
as templates to produces other mesoporous inorganic materials, or in controlled
release applications.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
Many
chemical reactions—etching, growth, and catalytic—produce highly faceted
surfaces. Examples range from the atomically flat silicon surfaces produced by
anisotropic etchants to the wide variety of faceted nanoparticles, including
cubes, wires, plates, tetrapods, and more. This faceting is a macroscopic
manifestation of highly site-specific surface reactions. In this Account, we
show that these site-specific reactions literally write a record of their
chemical reactivity in the morphology of the surface—a record that can be
quantified with scanning tunneling microscopy.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
Importantly,
the onset of catalysis by the [(PY5Me2)Co(H2O)]2+ series is anodically shifted
by introducing electron-withdrawing functional groups on the ligand. With the
[(bpy2PYMe)Co(CF3SO3)]1+ system, we showed that introducing a redox-active
moiety can facilitate the electro- and photochemical reduction of protons from
weak acids such as acetic acid or water. Using a high-throughput photochemical
reactor, we examined the structure–reactivity relationship of a series of
cobalt(ii) complexes. Taken together, these findings set the stage for the
broader application of polypyridyl systems to catalysis under environmentally
benign aqueous conditions.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
Light
is a fascinating phenomenon that ties together physics, chemistry, and biology.
It is unmatched in its ability to confer information with temporal and spatial
precision and has been used to map objects on the scale of tens of nanometers
(10–8 m) to light years (1016 m). This information, gathered through
super-resolution microscopes or space-based telescopes, is ultimately funneled
through the human visual system, which is a miracle in itself. It allows us to
see the Andromeda galaxy at night, an object that is 2.5 million light years
away and very dim, and ski the next day in bright sunlight at an intensity that
is 12 orders of magnitude higher.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
Supramolecular
bioinorganic chemistry is a natural evolution in biomimetic metallic systems
since it constitutes a further degree of complexity in modeling. The
traditional approach consisting of mimicking the first coordination sphere of
metal sites proved to be very efficient, because valuable data are extracted
from these examples to gain insight in natural systems mechanisms. But it does
not reproduce several specific aspects of enzymes that can be mimicked by the
implementation of a cavity embedding the labile active site and thus
controlling the properties of the metal ion by noncovalent interactions. This
Account reports on a strategy aimed at reproducing some supramolecular aspects
encountered in the natural systems.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
Magnetic
iron oxide nanoparticles have been extensively investigated for their various
biomedical applications including diagnostic imaging, biological sensing, drug,
cell, and gene delivery, and cell tracking. Recent advances in the designed
synthesis and assembly of uniformly sized iron oxide nanoparticles have brought
innovation in the field of nanomedicine. This Account provides a review on the
recent progresses in the controlled synthesis and assembly of uniformly sized
iron oxide nanoparticles for medical applications. In particular, it focuses on
three topics: stringent control of particle size during synthesis via the
“heat-up” process, surface modification for the high stability and
biocompatibility of the nanoparticles for diagnostic purposes, and assembly of
the nanoparticles within polymers or mesoporous silica matrices for theranostic
applications.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
Flame
retardants are widely used industrial chemicals that are added to polymers,
such as polyurethane foam, to prevent them from rapidly burning if exposed to a
small flame or a smoldering cigarette. Flame retardants, especially brominated
flame retardants, are added to many polymeric products at percent levels and
are present in most upholstered furniture and mattresses. Most of these
chemicals are so-called “additive” flame retardants and are not chemically
bound to the polymer; thus, they migrate from the polymeric materials into the
environment and into people. As a result, some of these chemicals have become
widespread pollutants, which is a concern given their possible adverse health
effects. Perhaps because of their environmental ubiquity, the most heavily used
group of brominated flame retardants, the polybrominated diphenyl ethers
(PBDEs), was withdrawn from production and use during the 2004–2013 period.
This led to an increasing demand for other flame retardants, including other
brominated aromatics and organophosphate esters. Although little is known about
the use or production volumes of these newer flame retardants, it is evident
that some of these chemicals are also becoming pervasive in the environment and
in humans.
Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-chemistry/
