Antonino Gulino

Pathway-dependent self-assembly of perylene diimide/peptide conjugates in aqueous medium.

Most molecular self-assembly strategies involve equilibrium systems, leading to a single thermodynamic product as a result of weak, reversible non-covalent interactions. Yet, strong non-covalent interactions may result in non-equilibrium self-assembly, in which structural diversity is achieved by forming several kinetic products based on a single covalent building block. We demonstrate that well-defined amphiphilic molecular systems based on perylene diimide/peptide conjugates exhibit kinetically controlled self-assembly in aqueous medium, enabling pathway-dependent assembly sequences, in which different organic nanostructures are evolved in a stepwise manner. The self-assembly process was characterized using UV/Vis circular dichroism (CD) spectroscopy, and cryogenic transmission electron microscopy (cryo-TEM). Our findings show that pathway-controlled self-assembly may significantly broaden the methodology of non-covalent synthesis.

Self-Propagating Assembly of a Molecular-Based Multilayer

Accelerated growth of a molecular-based material that is an active participant in its continuing self-propagated assembly has been demonstrated. This nonlinear growth process involves diffusion of palladium into a network consisting of metal-based chromophores linked via palladium.

Deposition of thin films of cobalt oxides by MOCVD

The Co(hfa)2·2H2O (hfa = CF3C(O)CHC(O)CF3) precursor was used in MOCVD experiments to deposit cobalt oxides, on optically transparent SiO2 substrates. CoO and Co3O4 films have been obtained depending on the adopted deposition conditions. XRD measurements provided evidence that CoO consists of cubic, (100) oriented crystals, whilst Co3O4 films are only partially oriented along the (311) direction. Mean crystallite sizes were evaluated from the XRD line broadening and the band-gap for Co3O4 was determined from the optically induced transitions. Both optical spectra and resistivity measurements of Co3O4 thin films showed that they are semi-conducting. The surface structure of the films was investigated by XPS.

Structural and electronic characterization of self-assembled molecular nanoarchitectures by X-ray photoelectron spectroscopy.

AbstractMolecular monolayers and similar nanoarchitectures are indicative of the promising future of nanotechnology. Therefore, many scientists recently devoted their efforts to the synthesis, characterization, and properties of mono- and multilayer-based systems. In this context, X-ray photoelectron spectroscopy is an important technique for the in-depth chemical and structural characterization of nanoscopic systems. In fact, it is a surface technique suitable for probing thicknesses of the same order of the photoelectron inelastic mean free paths (a few tens of ångströms) and allows one to immediately obtain qualitative and quantitative data, film thickness, surface coverage, molecule footprint, oxidation states, and presence of functional groups. Nevertheless, other techniques are important in obtaining a complete spectroscopic characterization of the investigated systems. Therefore, in the present review we report on X-ray photoelectron spectroscopy of self-assembled molecular mono- and multilayer materials including some examples on which other characterization techniques produced important results. FigureX-ray photoelectron spectroscopy revealed to be an important technique for an in-depth chemical and structural characterization of self-assembled molecular mono- and multi-layer materials

Stepwise Assembly of Coordination-Based Metal−Organic Networks

Metal-organic networks (MONs) were created by a stepwise solution deposition approach from vinylpyridine-based building blocks and PdCl(2). The combined experimental and computational study demonstrates the formation of saturated, structurally organized systems on solid supports. The rigid nature and geometry of the components are well-suited to form honeycomb and parallelogram structures, as predicted by a computational study. Detailed structural information of the new MONs was obtained by optical (UV/vis) spectroscopy, ellipsometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and synchrotron X-ray reflectivity (XRR). Notably, the XPS elemental composition indicates the formation of a palladium coordination-based network.

Linear vs Exponential Formation of Molecular-Based Assemblies

Here we present the critical role of the molecular structure and reaction parameters on the nature of thin-film growth, using a versatile two-step assembly method with organic and metal-organic chromophores cross-linked with palladium. It was found that the polypyridyl complexes exhibit exponential growth, whereas, under identical conditions, the organic systems exhibit linear behavior. The internal film morphology plays a pivotal role in the storage and usage of the palladium, where a more porous structure results in exponential growth. Interestingly, through proper tuning of the reaction conditions, the growth of the molecular assemblies can be controlled, resulting in a changeover from exponential to linear growth. These findings unequivocally demonstrate the importance of both the internal film structure and deposition conditions on the assembly of molecular-based films.

Very fast CO2 response and hydrophobic properties of novel poly(ionic liquid)s

A series of polymerizable tetraalkylammonium ionic liquids based on [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium cation and bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anions, as well as their corresponding homo- and copolymers, have been synthesized and characterized by means of 1H NMR, TG-DTA, DSC, MALDI-TOF, viscosimetry and XPS investigations. Hydrophobic and CO2 sensing properties of the poly(ionic liquid)s have been explored by dynamic contact angle and quartz crystal microbalance measurements. The CO2 sensing behavior of present polymers is very remarkable as they are featured by extremely rapid and completely reversible response without any memory-effect. Best results, in terms of sensitivity, have been obtained for [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium nonafluoro-1-butanesulfonate-based homopolymer. Tensiometric data show good hydrophobic properties with θadv > 90° for all the polymers under study except the one involving 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anion (θadv = 78.3°); receding contact angles, representative of the most hydrophilic portions of the polymers surface, lie in the range 22–54° and can be further improved by choosing the proper long-chained N-alkyl groups.

Tunable luminescent properties of a europium complex monolayer

Silica substrates were functionalized with a covalent 4-ClCH2C6H4SiCl3 monolayer. Additional covalent bonding of the tris(dibenzoylmethane) mono(5-amino-1,10-phenanthroline)europium (III) to the silylated substrates was further achieved. The optical properties of this robust monolayer system were studied at room temperature by both UV-vis and photoluminescence measurements. The UV-vis spectrum, in tune with solution measurements, reveals the presence of the title compound on the film surface. The surface chemical characterization of the monolayer was carried out by X-ray photoelectron measurements and the Eu spectrum shows spin–orbit components of the Eu 3d states. Photoluminescence measurements indicate the presence of two bands at 591 and 614 nm whose intensities can be switched by different light inputs. The adopted synthetic procedure has proven to be effective in transferring molecular properties to a solid state device.

Surface segregation of Sb in doped TiO2 rutile

Abstract The surface concentration of Sb in doped TiO2 rutile ceramics ( Ti 1 − 5 4x Sb x O 2 0 ), has been measured by means of angle-resolved core level X-ray photoelectron spectroscopy (AR-XPS). Depth profiles have been obtained by alternating Ar+-ion bombardment with core level measurements. At low doping levels Sb segregates by substitutional replacement of Ti in a large number of ionic planes whilst at higher Sb doping levels there is evidence of a new SbTiO amorphous surface phase whose thickness involves about five ionic planes. A rationalization of the monotonic decrease of the work function throughout the doping range studied has been proposed.

An x-ray photoelectron spectra and atomic force microscopy characterization of silica substrates engineered with a covalently assembled siloxane monolayer

Silica substrates were functionalized with a covalent 4-ClCH(2)C(6)H(4)SiCl(3) monolayer. Additional covalent bonding of appropriate functional molecules to the silylated substrates was further achieved. The surface chemical characterization was carried out by angle resolved x-ray photoelectron measurements. Moreover, surface morphological characterizations were performed by atomic force microscopy measurements. Present results provide step by step information on the covalently linked monolayer during the synthetic procedure.