Search results for "Actant"
showing 10 items of 473 documents
pH-Responsive Cyclodextrin-Surfactant Inclusion Complexes: Thermodynamics and Structural Aspects
2023
This thesis presents the investigation of the multilevel assembly of the alkyl oligoethylenoxide carboxylic acids and cyclodextrins. The aim of the work is to combine the short-range host-guest and long-range electrostatic interactions to form highly-ordered supramolecular complexes. The interactions between the components affect their individual response and their properties; therefore, the knowledge of the nature and the influence of their chemical structure is essential to understand the system’s behaviour. Polyoxyethylene alkyl carboxylic acids are an attractive class of surfactants to integrate both inclusion complexes and polyelectrolyte systems due to their pH and thermoresponsivenes…
Structure of Urea Clusters Confined in AOT Reversed Micelles
2003
The structure of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and that of urea containing AOT reversed micelles has been investigated by small-angle neutron scattering (SANS) and Fourier transform infrared (FT-IR) spectroscopy at different AOT concentrations and urea/AOT molar ratios. For the AOT/n-heptane system, SANS data analysis indicates that AOT molecules form prolate ellipsoidal aggregates, which grow asymmetrically along the major axis upon increasing the surfactant concentration. For the urea/AOT/n-heptane system, the SANS results are consistent with the hypothesis that urea is encapsulated as small-sized ellipsoidal hydrogen-bonded clusters within the hydrophilic micellar core of …
Spatio-temporal perturbation of the dynamics of the ferroin catalyzed Belousov-Zhabotinsky reaction in a batch reactor caused by sodium dodecyl sulfa…
2008
The effects of the anionic surfactant sodium dodecyl sulfate (SDS) on the spatio-temporal and temporal dynamics of the ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction have been studied over a wide surfactant concentration range. For the first time, investigations were performed also for unstirred systems. The presence of SDS in the reaction mixture influences the oscillatory parameters to an extent that significantly depends on the surfactant concentration. The trend of the wave speed v upon the increasing amount of SDS was found to have a maximum at [SDS] = 0.075 mol dm (-3) ( v = 0.071 mm s (-1)), after which the speed decreased to 0.043 mm s (-1) at [SDS] = 0.5 mol dm (-3), which is…
Insect pests of the Herbarium of the Palermo botanical garden and evaluation of semiochemicals for the control of the key pest Lasioderma serricorne …
2020
Abstract The herbaria are scientific tools of great importance that preserve extinct, rare, endemic, and common plant species and also have importance as Cultural Heritage for their historical and esthetical value. Herbaria can be infested by several insect pests feeding on dried plants, and their management is often complicated and difficult as the use of chemical insecticides can have negative drawbacks. This suggests a strong need for alternative control tools such as the use of semiochemicals to develop Integrated Pest Management (IPM) programs. In order to identify the main insect pests that determine the damages on the exsiccata stored in the Palermo Botanical Garden's Herbarium, one …
NEW INSIGHTS ON SUPRAMOLECULAR AGGREGATES OF SODIUM DOCUSATE (AOTNa) BY ION MOBILITY MASS SPECTROMETRY
2013
Backgorund: The ability of some surfactants to form charged aggregates in gas phase has been proven experimentally by electrospray ionization (ESI) spectrometry [1- 5]. However, in the early investigations, interesting questions concerning the structural organization of these aggregates in gas phase and if they reflect their typical self-assembling in the starting liquid solutions were not addressed. Subsequently, independently of their aggregation motive in liquid phase and of the charge state in the gas phase, some hints suggesting that surfactant molecules are organized in gas phase as reverse micelle-like aggregates have been reported Objective: The supramolecular charged aggregates for…
Collision induced fragmentations of multiply charged sodium bis(2-ethylhexyl)-sulfosuccinate aggregates in gas phase: neutral loss versus charge sepa…
2016
Abstract Stability and fragmentation patterns of multicharged aggregates of sodium bis(2-ethylhexyl)-sulfosuccinate (NaAOT) in gas phase have been investigated by ion mobility mass spectrometry (IM-MS) and tandem mass spectrometry (MS-MS). Positively doubly charged NaAOT aggregates show at low collision energy a preference for the loss of NaAOT molecules, whereas fragmentation through charge separation process is favored at higher collision energy. By increasing the charge state of the aggregates, the fragmentation through charge separation tends to predominate especially at low aggregation number and only charge separation fragmentation is observed for positively quadruply charged species.…
Soft Nanoonions: A Dynamic Overview onto Catanionic Vesicles Temperature-Driven Transition.
2020
Catanionic vesicles are emerging interesting structures for bioapplications. They self-generate by a pairing of oppositely charged ionic surfactants that assemble into hollow structures. Specifically, the anionic-cationic surfactant pair assumes a double-tailed zwitterionic behavior. In this work, the multilamellar-to-unilamellar thermal transition of several mixed aqueous systems, with a slight excess of the anionic one, were investigated. Interestingly, it was found that the anionic counterion underwent a dissociation as a consequence of a temperature increase, leading to the mentioned thermal transition. The present work proposed the spectroscopic techniques, specifically multinuclear NM…
Bioadhesive Matrix Tablets Loaded with Lipophilic Nanoparticles as Vehicles for Drugs for Periodontitis Treatment: Development and Characterization
2019
Periodontitis treatment is usually focused on the reduction or eradication of periodontal pathogens using antibiotics against anaerobic bacteria, such as metronidazole (MTR). Moreover, recently the correlation between periodontal diseases and overexpression of reactive oxygen species (ROS) led to the introduction of antioxidant biomolecules in therapy. In this work, bioadhesive buccal tablets, consisting of a hydrophilic matrix loaded with metronidazole and lipophilic nanoparticles as a vehicle of curcumin, were developed. Curcumin (CUR)-loaded nanostructured lipid carriers (NLC) were prepared using glycyrrhetic acid, hexadecanol, isopropyl palmitate and Tween®
Microemulsions: Phase transitions and their dynamics
2007
By differential scanning microcalorimetry we investigate temperature-induced phase transitions and their dynamics in mixtures of water, oil and a non-ionic surfactant. Special emphasis is on an investigation of the transition from a lamellar to a microemulsion phase and on the emulsification failure. The first-order phase transition from a lamellar to a microemulsion phase leads to heat changes up to 1k BT per surfactant molecule. These large values for the latent heat are quantitatively described by an interfacial model which takes into account the temperature dependence of the spontaneous curvature.
Binding of Short Alkyl Chain Surfactants to the (Ethylene oxide)13−(Propylene oxide)30−(Ethylene oxide)13and (Ethylene oxide)75−(Propylene oxide)30−(…
2002
The enthalpy of transfer (ΔHt) of neutral copolymers, at a fixed and low concentration ca. 10-3 mol kg-1, from water to the aqueous surfactant solutions as a function of the surfactant concentration (fSmS) was determined at 25 °C. The surfactants studied are sodium octanoate, sodium decanoate, N-octylpyridinium chloride (OPC), and N,N-dimethyloctylamine-N-oxide (ODAO). The copolymers are (ethylene oxide)13−(propylene oxide)30−(ethylene oxide)13 (L64) and (ethylene oxide)75−(propylene oxide)30−(ethylene oxide)75 (F68). The two copolymers show different hydrophilic−hydrophobic ratios, the larger being for F68. As a general feature, the shape of the ΔHt vs fSmS curve depends on the nature of t…