3 research outputs found
Efficient Phosphodiester Cleaving Nanozymes Resulting from Multivalency and Local Medium Polarity Control
The
self-organization of ZnÂ(II) complexes on the surface of 1.6-nm
diameter gold nanoparticles (nanozymes) allows the spontaneous formation
of multiple bimetallic catalytic sites capable to promote the cleavage
of a RNA model substrate. We show that by tuning the structure of
the nanoparticle-coating monolayer, it is possible to decrease the
polarity of the reaction site, and this in turn generates remarkable
increments of the cleavage efficiency
A General One-Step Synthesis of Alkanethiyl-Stabilized Gold Nanoparticles with Control over Core Size and Monolayer Functionality
In spite of widespread interest in the unique size-dependent
properties
and consequent applications of gold nanoparticles (AuNPs), synthetic
protocols that reliably allow for independent tuning of surface chemistry
and core size, the two critical determinants of AuNP properties, remain
limited. Often, core size is inherently affected by the ligand structure
in an unpredictable fashion. Functionalized ligands are commonly introduced
using postsynthesis exchange procedures, which can be inefficient
and operationally delicate. Here, we report a one-step protocol for
preparing monolayer-stabilized AuNPs that is compatible with a wide
range of ligand functional groups and also allows for the systematic
control of core size. In a single-phase reaction using the mild reducing
agent tert-butylamine borane, AuNPs that are compatible
with solvents spanning a wide range of polarities from toluene to
water can be produced without damaging reactive chemical functionalities
within the small-molecule surface-stabilizing ligands. We demonstrate
that the rate of reduction, which is easily controlled by adjusting
the period over which the reducing agent is added, is a simple parameter
that can be used irrespective of the ligand structure to adjust the
core size of AuNPs without broadening the size distribution. Core
sizes in the range of 2–10 nm can thus be generated. The upper
size limit appears to be determined by the nature of each specific
ligand/solvent pairing. This protocol produces high quality, functionally
sophisticated nanoparticles in a single step. By combining the ability
to vary size-related nanoparticle properties with the option to incorporate
reactive functional groups at the nanoparticle–solvent interface,
it is possible to generate chemically reactive colloidal building
blocks from which more complex nanoparticle-based devices and materials
may subsequently be constructed
Nanoparticle-Assisted NMR Detection of Organic Anions: From Chemosensing to Chromatography
Monolayer-protected nanoparticles
provide a straightforward access
to self-organized receptors that selectively bind different substrates
in water. Molecules featuring different kinds of noncovalent interactions
(namely, hydrophobic, ion pairing, and metal–ligand coordination)
can be grafted on the nanoparticle surface to provide tailored binding
sites for virtually any class of substrate. Not only the selectivity
but also the strength of these interactions can be modulated. Such
recognition ability can be exploited with new sensing protocols, based
on NMR magnetization transfer and diffusion-ordered spectroscopy (DOSY),
to detect and identify organic molecules in complex mixtures