Exploring the self-assembly of dumbbell-shaped polyoxometalate hybrids,from molecular building units to nanostructured soft materials

The formation of hierarchical nanostructures using preformed dumbbell-like species made of covalent organic–inorganic polyoxometalate (POM)-based hybrids is herein described. In this system, the presence of charged subunits (POM, metal linkers, and counter ions) in the complex molecular architecture can drive their aggregation, which results from a competition between the solvation energy of the discrete species and intermolecular electrostatic interactions. We show that the nature of the POM and the charge of the metal linker are key parameters for the hierarchical nanoorganization. The experimental findings were corroborated with a computational investigation combining DFT and molecular dynamics simulation methods, which outlines the importance of solvation of the counter ion and POM/counter ion association in the aggregation process. The dumbbell-like species can also form gels, in the presence of a poorer solvent, displaying similar nanoorganization of the aggregates. We show that starting from the designed molecular building units whose internal charges can be controlled by redox trigger we can achieve their implementation into soft nanostructured materials through the control of their supramolecular organization.

The formation of hierarchical nanostructures using supramolecular dumbbell-like species made of organic–inorganic polyoxometalate-based hybrids is investigated by combination of SAXS and computational methods.     

Investigation of the complexation of essential oil components with cyclodextrins

The formation of inclusion complexes of six essential oil (EO) components (β-caryophyllene, cis-ocimene, trans-ocimene, sabinene hydrate (thujanol), γ-terpinene and α-terpineol) with six cyclodextrins (CDs) (α-CD, β-CD, γ-CD, HP-β-CD, RAMEB and CRYSMEB) was investigated by using static headspace-gas chromatography and UV–visible spectroscopy. Retention studies showed that CDs could efficiently reduce the volatility of EO components except for β-caryophyllene with α-CD. In this case, no inclusion complex was detected while for other compounds the formation of 1:1 inclusion complexes was observed. Results revealed that the inclusion stability mainly depends on geometric complementarity between encapsulated molecule and CD's cavity. Molecular modelling was used to investigate the complementarities between host and guest. Thus, CDs could efficiently be regarded as promising encapsulants for EO components leading to improve their application in cosmetic, pharmaceutical and agriculture fields.     

Improved aqueous Cannizzaro reaction in presence of cyclodextrin

An aqueous hydroxypropyl-??-cyclodextrin solution has been used to increase the conversion of 4-biphenylcarboxaldehyde into the corresponding alcoholic and carboxylic substrates, by means of a Cannizzaro reaction. The observed enhancement has been ascribed to a partial solubilization of 4-biphenylcarboxaldehyde. In addition, as the main part of the organic substrates still remains insoluble, synthesized products are easily recovered by filtration. As a consequence, the basic cyclodextrin solution might also be reused for a new synthetic cycle, without significant loss of conversion. Aqueous solid?Cliquid biphasic reaction in presence of cyclodextrins thus seems to be a promising tool in the green chemistry field.     

Effects of vagal nerve stimulation on laryngeal function

Functional electrical stimulation is a developing methodology that shows significant potential in the management of peripheral neuromuscular deficits. Potential applications in the head and neck area, including control of bilateral vocal fold paralysis and spasmodic dysphonia, have recently been explored. Despite promising early results, very little is known about the mechanisms of action or the long-term effects of electrical stimulation on human laryngeal function. Recent development of implantable vagal nerve stimulators as a method to control intractable seizures in individuals who have not responded to medication provides a unique opportunity to study its effect on the normal human larynx. Laryngeal and vocal function testing was studied on five individuals who had undergone vagal nerve stimulator implants for intractable seizures. Consistent abduction/adduction of the left vocal fold was achieved at 20 and 40 Hz, respectively. Higher levels of electrical stimulation produced hemispasm of the larynx. Results were consistent with studies in the literature of recurrent laryngeal nerve stimulation in animal and human models. The vagus nerve provides relatively easy access for implantation of electrodes to provide electrical stimulation to the muscles of the larynx. Vagal nerve stimulation may prove efficacious in the treatment of movement disorders of the larynx; further study is needed.     

Combination of DES and macrocyclic host molecules: Review and perspectives

Solvation in deep eutectic solvents (DESs) and encapsulation in macrocycles are efficient strategies for molecule's solubilization. Recently, new systems combining DES and macrocycles are being constructed using two approaches: a) solubilizing hosts in preformed DES or b) using hosts as a DES component. This strategy could evolve in new outcomes in DES properties, more precisely provide the solvents with supramolecular capacity, and translate into interesting performances. In the present review, we will give the reader an overview of the studies accomplished in this growing research area, with a focus on the experimental perspectives that we consider to be the most important in order to enlarge knowledge on the properties and behavior of these neoteric systems.     

Monotonicity properties of multi-dimensional reflected diffusions in random environment and applications

We consider an N$N$-dimensional reflected process, modeling an infinite capacity fluid queues network, of which service and input rates depend on the queue levels as well as on the state of an exterior ergodic stationary process. N$N$ is the number of queues in the network. We prove a monotonicity result for such a process, from which we deduce stability results for networks of queues. Particular attention is paid to the case N=2$N=2$. Next, we give some applications of those stability results.     

Branching random walk with trapping zones

We consider a branching random walk with values in a certain set $\mathbb{S}$, where the branching mechanism is different according to whether particles (individuals) are in a certain so called trapping set $A?\mathbb{S}$ or not. We are then interested, under different scenarios, in properties of either the transient random measure describing distribution of individuals on $\mathbb{S}$ over time or its asymptotic behaviour.     

Experimental and Theoretical Study on the Inclusion Capability of a Fluorescent Indolizine β-Cyclodextrin Sensor Towards Volatile and Semi-volatile Organic Guest

Inclusion equilibria of a new fluorescent indolizine modified β-cyclodextrin were studied in aqueous solution to evaluate its use as a fluorescent chemo-sensor for volatile organic compounds (VOCs). The host compound shows a decrease of the fluorescence intensity by adding adamantanol, benzene, toluene, phenol and p-cresol as guest. The sensing parameter (ΔI/I ₀) was used to show the sensing ability of the host. The formation constant values measured using a spectral displacement method and a specific algorithm treatment are reported. Although the guest binding ability of the sensor is not enhanced by the existence of the hydrophobic cap, this new cyclodextrin sensor shows a very strong sensing ability. The experimental values of the constants were in good agreement with the computed complexation energies, ΔE, from molecular mechanics modelling of the inclusion process.     

Scanning tunneling microscopy investigation of an inclusion complex between the β-cyclodextrin and the sodium salt of the trisulfonated triphenylphosphine

Scanning tunneling microscopy has been used to image on a highly orientated pyrolytic graphite substrate an inclusion complex between the sodium salt of the trisulfonated triphenylphosphine (TPPTS) and the β-cyclodextrin (CyD). The images were in very good agreement with the structure that has been reported for this inclusion complex and it is postulated that β-CyD/TPPTS inclusion complex lies on the apolar graphite substrate by its primary face. A correlation of image contrast with the frontier orbitals of the inclusion complex is also clearly established for the first time in the case of CyD-based supramolecular assemblies. The self-assembly of the inclusion complexes on the graphic surface is also discussed.