New calixarene-based nanosponges (CaNSs), i.e., hyper-reticulated polymers constituted by calixarene monomer units joined by means of bis(1,2,3-trialzolyl)alkyl linkers, were synthesized, characterized and subjected to preliminary tests to assess their supramolecular absorption abilities towards a set of suitable organic guests, selected as pollutant models. The synthesis was accomplished by means of a CuAAC reaction between a tetrakis(propargyloxy)calix[4]arene and an alkyl diazide. The formation of the polymeric network was assessed by means of FTIR and 13C{1H} CP-MAS solid-state NMR techniques, whereas morphological characterization was provided by SEM microghaphy. The materials were proved to possess pH-dependent sequestration abilities, due to the presence of the weakly basic triazole linkers. Sequestration efficiency indeed depends on the effective occurrence of both electrostatic and hydrophobic interactions between the guest and the polymer lattice. Thus, our CaNS nanosponges can be considered as a new class of purely synthetic smart absorbent materials.
Four mixed cyclodextrin‐calixarene nanosponges were tested as possible Drug Delivery Systems, using Tetracycline antibiotic as a suitable model drug. The selected nanosponges featured a different composition ratio between the two host co‐monomer components, and the possible presence of ionisable amine or carboxyl groups deriving from chemical post‐modification. The pH‐dependent absorption and release abilities of the materials were verified; in particular release kinetics showed the occurrence of a simple first‐order profile. The antibacterial activity of nanosponge‐tetracycline composites suitably prepared under sterile conditions was assayed towards both Gram‐positive and Gram‐negative typical bacterial strains, showing in some cases an interesting improvement of the biocidal activity.
Four new composite materials, formed by silver nanoparticles embedded in polyamino‐cyclodextrin nanosponge architectures, were designed exploiting the affinity of polyamino‐cyclodextrins towards Ag+ ions. These materials were characterized by means of different techniques (thermogravimetry, FT‐IR, solid state NMR, SEM, HR‐TEM), and tested as catalysts for the reduction of nitroarenes and the oxidative coupling of anilines. The results obtained showed synergistic activity between the supramolecular binding abilities of the nanosponge matrix and the catalytic properties of the metal nanoparticle, and open the way towards the design of new composite smart nanomaterials with improved catalytic performances.
An application for visualizing the
aggregation of structureless atoms is presented. The application allows
us to demonstrate on a qualitative basis, as well as by quantitatively
monitoring the aggregate surface/volume ratio, that the enhanced
reactivity of nanoparticles can be connected with their large specific
surface. It is suggested that, along with the use of geometric analogies,
this bottom-up approach can be effective in discussing the enhanced
reactivity proprieties of nanoparticles. The application is based
on a two-dimensional realistic dynamic model where atoms move because
of their thermal and interaction potential energies, and the trajectories
are determined by solving numerically Newton’s laws according
to a Molecular Dynamics (MD) scheme. For this purpose, a web-based
MD engine was adapted as needed. It is suggested that, when possible,
using a realistic simulation rather than simple animations offers
several advantages in the visualization of processes of interest in
chemistry education. First, in a simulation the outcome of the process
under study is not set a priori but it is the result of the dynamic
evolution of the system; furthermore, specific parameters can be systematically
varied, and the effects of these changes can be investigated. The
application can be used at different levels of detail and in different
instruction levels. Qualitative visual observations of the growing
aggregates and of the progressive decrease of the reactive surface
are suitable at all levels of instruction. Systematic investigations
on the effect of changes of the atomic and aggregate sizes and temperature,
suitable for senior high school and college courses, are also reported.
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