Visualizing Solubilization by a Realistic Particle Model in Chemistry Education

An application for the visualization of the mixing process of two different types of structureless interacting particles is presented. The application allows to demonstrate on a qualitative basis, as well as by quantitatively monitoring the time evolution of the fractions of aggregates of different sizes, that the formation of a homogeneous mixture is the result of favorable solute-solvent interactions as well as by temperature. It is suggested that, along with the use of suitable macroscopic examples, visualizations by the present application are useful in elucidating concepts related to miscibility/solubility. The application is based on a two-dimensional realistic dynamic model where ato…

Cyclodextrin‐Calixarene Nanosponges as Potential Platforms for pH‐Dependent Delivery of Tetracycline

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 ty…

Sintesi e attivita’ fotocatalitica di materiali compositi ciclodestrina/ossido di grafene/nanoparticelle di argento

Engineering of polylactic acids for biomedical applications

Evaluation of adsorption ability of Cyclodextrin-Calixarene Nanosponges towards Pb2+ ion in aqueous solution

Abstract Different cyclodextrin-calixarene nanosponges (CyCaNSs) have been characterized by means of FFC-NMR relaxometry, and used as sorbents to remove Pb2+ ions from aqueous solutions. Considering that the removal treatments may involve polluted waters with different characteristics, the adsorption experiments were performed on solutions without and with the addition of background salts, under different operational conditions. The adsorption abilities and affinities of the nanosponges towards Pb2+ ions were investigated by measuring the metal ion concentration by means of Inductively Coupled Plasma Emission Spectroscopy (ICP-OES) and Differential Pulse Anodic Stripping Voltammetry (DP-ASV…

Attivita’ sinergica di nanoparticelle di argento fotosintetizzate con antibatterici classici

Synergistic activity of photo-synthesized silver nanoparticles with classic antibacterials

Realistic Implementation of the Particle Model for the Visualization of Nanoparticle Precipitation and Growth

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 numeric…

Un modello realistico per visualizzazioni dinamiche in didattica della chimica

In questo lavoro sono presentate due applicazioni per la visualizzazione dei processi di aggregazione e di solubilizzazione di particelle interagenti e prive di struttura. Le applicazioni consentono di dimostrare qualitativamente e quantitativamente, per mezzo dell'osservazione dell'evoluzione temporale del rapporto superficie/volume e della frazione di particelle aggregate, che, da un lato, il processo di crescita di nanoaggregati è accompagnato da una diminuzione del rapporto superficie/volume, dall'altro, che interazioni soluto-solvente favorevoli e temperature elevate producono soluzioni omogenee. Si propone che, insieme ad opportuni esempi macroscopici, visualizzazioni mediante le pres…

Effect of pH Variations on the Properties of Cyclodextrin‐Calixarene Nanosponges

The pH-responsive properties of cyclodextrin-calixarene nanosponge co-polymeric materials have been investigated. In particular, ISE-H+ potentiometric titrations were carried out in order to evaluate the acid-base properties and the actual amount of ionizable sites present in the materials. Moreover, the relevant pH-dependent adsorption abilities were evaluated towards a set of selected model organic pollutant molecules by means of adsorption tests and by studying the corresponding adsorption isotherms. The latter ones could be suitably described by means of the Freundlich model. The whole of the experimental results enabled us to clarify some general aspects of the microscopic behavior of …

Synergistic Activity of Silver Nanoparticles and Polyaminocyclodextrins in Nanosponge Architectures

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 …

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

Two mixtures of polyaminoazides were synthesized by a nucleophilic displacement strategy providing no separation of the components. The mixtures were adequately characterized by means of combined HR-ESIMS, FTIR and NMR techniques and, despite their complexity, they were successfully used to accomplish the subsequent preparation of pH-sensitive calixarene hyper-reticulated nanosponge materials. The desired responsivity to pH variations of the nanosponges obtained was verified by means of absorption tests on a set of organic pollutant model molecules.

Acid-base properties and sequestering abilities towards toxic metal ions of cyclodextrin-calixarene co-polymers

Smart materials with stimuli-responsive properties represent an interesting research area considering both their potential applications and the conceptual issues implied. They might be successfully employed in various fields, such as drug carrier/delivery devices to sensors, environment remediation, active packaging [1-2]. In this contest, we have recently synthesized various pH-responsive pre- and post-modified cyclodextrin-calixarene nanosponges (CyCaNSs) with 1,2,3-triazole linker units (ACNSs) able to vary their sequestering abilities towards organic and inorganic compounds. In particular, their adsorption properties were varied changing the molar ratio between the co-monomers, and the …

SMART NANOSPONGE-BASED SYSTEMS FOR ADVANCED APPLICATIONS

FFC-NMR techniques for assessing the texture features of nanosponges

Nanosponges (NSs), i.e. hyper cross linked polymeric materials obtained by reticulating cyclodextrin units with suitable linker units, constitute an emerging class of functional materials, due to their easy synthesis and chemical modification, and to their tunable absorption and controlled release abilities as well. NSs are supposed to possess a thick network of nanochannels in their highly disordered structure. However, their textural features (average pore size, specific surface and specific pore volume) are quite difficult to estimate, and classical evaluation methodologies (N2 absorption isotherms analyzed by BET or BJH methods, or dye absorption isotherms1) have afforded questionable r…

Elucidating the Influence of the Activation Energy on Reaction Rates by Simulations Based on a Simple Particle Model

An application for visualizing the dynamic properties of an equimolar binary mixture of isotropic reactive particles is presented. By introducing a user selectable choice for the activation energy, the application is useful to demonstrate qualitatively that the reaction rate depends on the above choice and on temperature. The application is based on a 2D realistic dynamic model where atoms move because of their thermal energies and the trajectories are determined by solving numerically Newton’s laws according to a Molecular Dynamics (MD) scheme. Collisions are monitored as time progresses, and every time the collision energy is larger than the selected activation energy, a reactive event oc…

Heuristic Algorithm for the Analysis of Fast Field Cycling (FFC) NMR Dispersion Curves

Evaluation of nuclear magnetic relaxation dispersion (NMRD) curves obtained by the fast field cycling nuclear magnetic resonance (FFC-NMR) relaxometry technique is a valuable tool for analyzing the microscopic dynamics of condensed matter systems. However, quantitative data analysis involves several conceptual and practical issues. Moving forward from previous literature approaches, we propose a new analysis method, relying on the elaboration of the inverse integral transform of the NMRD curve. Our approach results in a true heuristic method, able to unambiguously individuate the dynamic domains in the system, thereby avoiding the possible introduction of any element of discretion. The anal…

A new heuristic algorithm for the analysis of NMRD dispersion curves

Regression analysis of the NMRD dispersion curves obtained by the FFC-NMR relaxometric technique involves several conceptual and practical issues, which must be carefully addressed in order to gain reliable information on the system studied. Indeed, particular caution is needed when the FFC technique is applied to the investigation of complex systems such as polymeric matrixes, porous materials, food samples, and so on. In these cases, and in general whenever a rigorous approach based on a suitable physical modelization of the system is not available, data analysis must be performed by means of a “model–free” approach. Moving forward from previous literature, in the present communication we…

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

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 pro…

Nanosponge-C3N4 composites as photocatalysts for selective partial alcohol oxidation in aqueous suspension

A set of four composite materials was prepared, consisting of a nanosponge matrix based on beta-cyclodextrin in which carbon nitride was dispersed. The materials were characterized by the presence of diverse cross-linker units joining the cyclodextrin moieties, in order to vary the absorption/release abilities of the matrix. The composites were characterized and used as photocatalysts in aqueous medium under UV, visible and natural solar irradiation for the photodegradation of 4-nitrophenol, and for the selective partial oxidation of 5-hydroxymethylfurfural and veratryl alcohol to the corresponding aldehydes. The nanosponge-C3N4 composites showed higher activity than the pristine semiconduc…

Reduced graphene oxide/silver nanoparticles/β-cyclodextrin nanosponges composites with improved photocatalytic activity

Significant activity improvement was achieved by associating graphene oxide-silver composite photocatalysts with cyclodextrin-based nanosponge materials, due to the synergistic effect provided by the supramolecular host abilities of the nanosponge. Three photocatalysts were prepared, fully characterized (FT-IR, ss-NMR, Raman, XRD, SEM, EDX, AFM, ICP, TGA, potentiometric titration), and tested for the oxidative photodegradation of some dyes and phenols, chosen as model organic pollutants. Compared to the unsupported photocatalyst, the nanosponge-based materials showed enhanced performances (being able to carry out the degradation even of dyes which do not react in the presence of the unsuppo…

Un modello realistico per visualizzazioni in didattica

In this work, two applications for the visualization of the aggregation and the solubilization of structureless interacting particles are presented. The applications allow to demonstrate on a qualitative basis as well as by quantitatively monitoring the time evolution of the surface/volume ratio and of the fractions of aggregated particles, that, on the one hand, the growth of nanoaggregates implies a decrease of their surface/volume ratio and, on the other, that the formation of homogeneous mixtures is the result of favorable solute-solvent interactions as well as of temperature. It is suggested that, along with the use of suitable macroscopic examples, visualizations by the present applic…