Luigi Monsù Scolaro

Scaling the Chirality in Porphyrin J-Nanoaggregates

Chiral porphyrin J-aggregates are confined into microemulsions, achieving a fine control of their size and optical properties. The quality of the circular dichroism signal exhibits a remarkable scaling on the dimension from the nano- up to mesoscopic regime.

Solvent vapour annealing of organic thin films: controlling the self-assembly of functional systems across multiple length scales

Solvent vapour annealing allows macroscopic healing of molecular assemblies at surfaces to form suprastructures featuring a higher degree of order, and significant improvement of the performance of organic electronic devices.

Kinetic control of chirality in porphyrin J-aggregates.

Detailed kinetic investigations demonstrate the fundamental role of kinetic parameters in the expression and transmission of chirality in supramolecular systems. The rate of the aggregation process leading to the formation of J-aggregates strongly affects the size of these nanoassemblies and the chiral induction.

Phase separation and affinity between a fluorinated perylene diimide dye and an alkyl-substituted hexa-peri-hexabenzocoronene

Fluorination of alkyl groups is a known strategy for hindering miscibility, thus promoting phase separation, when blends are prepared with a hydrocarbon compound. A new perylene bis(dicarboximide) derivative functionalized with branched N-perfluoroalkyl moieties (BPF-PDI) has been synthesized as electron acceptor to be potentially used in conjunction with the electron donor hexakis(dodecyl)hexabenzocoronene (HBC-C12) in bulk heterojunction solar cells. Aiming at controlling self-assembly between the two components at the supramolecular level, stoichiometric blends in CHCl3 have been prepared either by spin- or drop-casting onto silicon surfaces, and further subjected to solvent vapour annealing (SVA) treatment in a CHCl3-saturated atmosphere. Spectroscopic investigation in solution shows the formation of supramolecular BPF-PDI–HBC-C12 dimers, with an association constant Kass = (2.1 ± 0.3) × 104 M−1, pointing to a strong and unexpected affinity between the two species within the mixture. Characterization through optical and atomic force microscopies of the deposited samples revealed that the self-assembly behaviour of the blends on SiOx is remarkably different from mono-component films, thus confirming the absence of a macroscopic phase-separation between the two components featuring isolated domains of the neat acceptor or donor compound. In addition, X-ray studies provided evidence for the existence of a local-scale phase separation. These findings are of importance for organic photovoltaics, since they offer a new strategy to control the phase separation at different scales in electron acceptor–donor blends.

Probing specific protein recognition by size-controlled glycosylated cyclodextrin nanoassemblies

The balance between hydrophobic and hydrophilic components in amphiphilic β-cyclodextrins, targeted by receptor specific groups (SC6CDGlc, SC6CDGal, SC16CDGlc, SC16CDGal), sensitively influences the structural properties of these systems. The different amphiphilic features of single cyclodextrins generate micellar aggregates and vesicles with an internal aqueous compartment able to encapsulate guests, such as rhodamine 6G. Small-angle light scattering (SAXS), cryo-TEM and AFM investigations describe the size and shape of these self-organized glycoligands. Recognition of the nanoassemblies by a specific receptor has effectively been demonstrated by means of time resolved fluorescence and is addressed in water by the morphological properties of cyclodextrin aggregates. Exclusively galactosylated thiohexyl-cyclodextrin binds specifically lectin from Pseudomonas aeruginosa. β-D-Galactose competes with galactosylated cyclodextrin aggregates by inhibiting lectin binding but does not affect the mesoscopic environment of the protein. The better selectivity of the less hydrophobic cyclodextrins towards lectin should probably be ascribed to the morphology (size and shape) of these cyclodextrin aggregates. The recognition properties of this particular cyclodextrin (SC6CDGal) are probably due to the presence of small micelles which interact more efficiently with the lectin binding site. The modulation of the hydrophobic–hydrophilic balance of the macrocycle labelled with targeting groups allows the design of “active” nanosized carriers for drug delivery.

Kinetic effects of tartaric acid on the growth of chiral J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin

The kinetics of growth for chiral J-aggregates of H(4)TPPS(4) porphyrin have been investigated under different experimental conditions in the presence of tartaric acid. The observed rate constants and the anisotropy factor g show a defined dependence on the enantiomer used as a chiral templating agent.

Supramolecular mimetic peroxidase based on hemin and PAMAM dendrimers

An acid-base interaction between hemin and PAMAM dendrimers affords supramolecular non-covalent peroxidase systems whose catalytic activity is enhanced after spontaneous electrostatic self-assembling onto a solid surface.

Micellar aggregates of platinum(II) complexes containing porphyrins

Abstract The complex [Pt(Cy2dim)Me]4(TpyP)(CF3SO3)4 (1) (Cy2dim=dicyclohexyldiimine; TpyP=5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphine) has been synthesized and characterized with a number of spectroscopic techniques. The solubilization of 1 in anionic (sodium dodecyl sulfate, SDS) and neutral (Triton X-100, TX-100) aqueous surfactant solutions has revealed two different modes of interaction: (i) aggregation in the hydrophobic region of SDS micelles; and (ii) aggregation in the hydrophobic region with partial intercalation in the solvent accessible area of TX-100 micelles. In the case of SDS, the formation of premicellar aggregates has been evidenced by a surfactant concentration range two orders of magnitude lower than the critical micellar concentration (cmc). The metalated Mn(III)TpyP derivative of complex 1 exhibits a moderate peroxidase activity in agreement with the aggregation models proposed for the micellar solutions.

Photoresponsive multilayer films by assembling cationic amphiphilic cyclodextrins and anionic porphyrins at the air/water interface

Densely packed hybrid monolayers of amphiphilic cyclodextrins incorporating hydrophilic porphyrins are formed at the air/water interface through electrostatic interaction and can be transferred onto quartz substrates by Langmuir–Schafer deposition. The resulting multilayers exhibit a good response to light excitation as proven by fluorescence emission, triplet–triplet absorption and singlet oxygen photogeneration.

Nucleation effects in the aggregation of water-soluble porphyrin aqueous solutions

Water soluble porphyrins bearing charged groups can be fostered to aggregate by simply screening the repulsive interactions between side-groups with the same charge. We have extensively studied the aggregation of synthetic porphyrins, which on changing the ionic strength give mesoscopic aggregates having a fractal behavior. The resulting structures can be modulated on changing the medium properties. Here we report on a kinetic study of such aggregation behavior on varying the salt concentration, the temperature and the history of the samples, showing the importance of the nucleation step in determining the growth of the aggregates.