Caterina Maria Tone

Amine-functionalized SBA-15 in poly(styrene-b-butadiene-b-styrene) (SBS) yields permeable and selective nanostructured membranes for gas separation

New nanostructured hybrid membranes for gas separation have been prepared and characterized for the first time in the literature by using a block copolymer, poly(styrene-b-butadiene-b-styrene) (SBS), and aminated SBA-15. Short mesopore channels, platelet SBA-15 particles with a high surface density of 3-aminopropyl grafts (3.8 nm−2) and modest surface area reduction (45%) were prepared, characterized and used as a filler. The gas transport characterization of the hybrid membranes indicates that with a 10 wt% content of aminated filler, outstanding performances in terms of selectivity and permeability for the CH4/N2 and the CO2/N2 gas pairs can be obtained. In particular, the CH4/N2 ideal selectivity of 7.3 is higher than the values of the existing block co-polymers used for this separation and of mixed matrix membranes described to date in the literature. Membranes with such a high separation factor may enable the exploitation of natural gas with high N2 content and increase the amount of methane that can be economically recovered. The combination of the CO2/N2 ideal selectivity of 53 with a CO2 permeability of 173 Barrer demonstrates that the new hybrid membranes prepared in this study deserve further attention as a practical commercial solution also for the post-combustion capture of carbon dioxide. Finally, the small and flat particles dispersed in the polymer lend themselves to the fabrication of thin industrial membranes with enhanced productivity.

Dynamical homeotropic and planar alignments of chromonic liquid crystals

We report on our latest studies on alignment of chromonic liquid crystals, a special class of molecules which recently attracted the attention of researchers. In particular, we show a detailed study of planar anchoring of disodium cromoglycate (DSCG) and, for the first time in the literature, a stable homeotropic alignment, achieved using a surface property of the alignment layer, i.e. the hydrophobicity. Excellent candidates from this point of view are pure polybutadiene (PB) and polydimethylsiloxane (PDMS). In fact, for the former the homeotropic anchoring stabilizes after one day, while for the latter stabilization occurs soon after cooling from the isotropic phase. After a long time both types of alignments (planar and homeotropic) evolve into thermodynamically stable configurations, i.e. ribbon structures. An explanation of the behaviour is given.

All-optical control of localized plasmonic resonance realized by photoalignment of liquid crystals

Large shifts in the plasmonic resonances of a thin film of gold nanorods (GNRs) are induced through the modulation of the local refractive index of the neighboring dielectric medium. This change is enabled through light-induced surface reorientation of a nematic liquid crystal in contact with a nanometer-thin photoalignment layer coating the GNR film. The presence of isolated and well distributed GNRs, both before and after the photoalignment layer deposition, is shown through atomic force and scanning electron microscopy. Exposure of the photoalignment layer to polarized light is shown to reorient aligned nematic liquid crystal molecules to an orthogonal direction, thereby changing the local refractive index of the medium in close proximity to the GNR film. This large change in the local dielectric strength is shown to cause a broad red shift of the localized plasmonic longitudinal resonance and almost no shift in the local transverse resonance. The ability to remotely and quickly change the plasmonic properties of this GNR system marks a breakthrough towards the realization of all-optical plasmonic and photonic devices such as plasmonic colour filters.

Unconventionally shaped chromonic liquid crystals formed by novel silver(I) complexes

The synthesis of the first chiral Ag(I) bis chelated bipyridine ionic complexes showing chromonic liquid crystalline behaviour in water is reported. Single crystal X-ray analysis revealed a pre-chromonic organization in the crystalline state, with silver(I) cations stacking into columns reinforced by hydrogen bonding with the acetate counterions and water molecules. Due to the presence of molecules with an unconventional shape for the generation of typical chromonic phases, a full characterization based on phase diagram analysis, completely resolved by POM, DSC and X-ray powder diffraction measurements, has been conducted. Moreover, cryo-TEM experiments have been carried out in order to confirm the appearance of nematic columnar phases. A “route” to drive the alignment of the liquid crystalline phases of these compounds has been developed, which is particularly important for future application in biophotonic devices. Finally, the presence of transient twisted periodical stripe structures has been observed, when an initial planar alignment is destroyed in favour of a homeotropic configuration of the molecules dictated by the confining surfaces.

Alignment of Chromonic Liquid Crystals: A Difficult Task

We present our recent effort on chromonic liquid crystal alignment. In particular, we report the alignment behavior of chromonic molecules using different hydrophobic substrates. Different materials have been used to this purpose but in all cases ribbons textures develop, indicating a slow water evaporation and/or a strong aggregation among molecules, that, as reported in a recent paper, give rise to threads connected through salt bridge bonds. Thin films of materials usually employed for thermotropic liquid crystals alignment induce schlieren textures that after 10 days evolve into ribbon textures; thin films of materials with a low surface energy orient molecules in homeotropic configuration, but the alignment is lost after two weeks as in the case of degenerate planar alignment.

AFM Studies on Curcumin Based Zn(II) Complex Molecules for Applications as Anticancer Agents

We present our recent atomic force microscopy studies on a curcumin based Zn(II) complex anticancer agent. We investigated the morphology of the molecule on a nanoscale level to test the effect of different substrates and solvents on the shape and the aggregation properties of the molecule. Self assembled films were produced by Langmuir technique at different surface pressures and by spin coating. Measurements showed small molecular aggregates with a height of 0,5 nm. The wetting properties of the substrate play a role in the aggregation properties and the film formation. The obtained results will help in understanding the interaction of the studied molecule with DNA or chromonic systems.