Giacomo Ghini

Self-sorting chiral organogels from a long chain carbamate of 1-benzyl-pyrrolidine-3,4-diol

(3S,4S)-1-benzylpyrrolidine-3,4-diyl bis(dodecylcarbamate), a pyrrolidine ring bearing two long carbon chains connected by carbamate functionalities, is the origin of stable gels in both polar and apolar solvents. Several experimental and theoretical techniques (cryo-TEM, AFM, DSC, circular dichroism (CD), molecular mechanics calculations and CD simulations) were used to describe the formation and the characteristics of the chiral supramolecular structures and fibers constituting the gel. The chirality at both supramolecular and microscopic level depends on the configuration of the stereogenic centers of the pyrrolidine unit. The gels formed by the two enantiomers of the gelator and their mixtures display enantiomeric discrimination resulting in a self-sorting process. In fact, separate fibers of opposite helicity are obtained, which suggests this class of compounds has strong potential for realizing functionalized chiral architectures.

Pyrene-Excimers-Based Antenna Systems

A series of dendrimeric compounds bearing pyrene units were synthesized to afford light-harvesting antennae based on the formation of intramolecular excimers. The synthetic plan profited from the efficiency of the Huisgen reaction, the 1,3-dipolar cycloaddition of azides and terminal alkynes, which allowed ready assembly of the different building blocks. The three molecular antennae obtained, of increasing generation, revealed efficient energy transfer both in solution and in the solid state.

Chirality driven self-assembly in a fluorescent organogel†

In this work, we present the characterization of an enantiomeric pair of fluorescent dye organogelators and the properties of their stable gel at low concentration in organic solvents. The gels of both enantiomers and of their mixtures were analyzed by differential scanning calorimetry, circular dichroism (CD), atomic force microscopy, UV-vis absorption, and fluorescence. The acquired data were supported by molecular modeling of the helical assembly of the gelators and by the simulation of their CD spectra by means of DeVoe method, and suggested the occurrence of an enantiomeric discrimination process during the formation of the gels.

Soft matter nanocomposites by grafting a versatile organogelator to carbon nanostructures

The organic functionalization of either [60]fullerene or MWCNTs with a highly efficient organogelator has allowed the production of novel and homogeneously dispersed soft-nanocomposites. While the nanostructured carbon materials produced by simple mixing do not homogeneously disperse into a preformed gel, C60- and MWCNT-containing gels have been conveniently obtained by covalent functionalization of the carbon lattice with reactive organogelator derivatives. The present study, while emphasizing the gelling properties of a selected class of organogelators, allows the conjugation of the properties of gels and nanostructured carbon materials yielding novel soft-nanocomposites.

A new organogelator based on an enantiopure C2 symmetric pyrrolidine

The synthesis and the properties of a new chiral organogelator based on a C(2) symmetric pyrrolidine, are described together with its use for the synthesis of other functionalised organogelators.

Surface-enhanced fluorescence and surface-enhanced Raman scattering of push-pull molecules: sulfur-functionalized 4-amino-7-nitrobenzofurazan adsorbed on Ag and Au nanostructured substrates.

AbstractWe investigated the chemisorption of self-assembled monolayers of sulfur-functionalized 4-amino-7-nitrobenzofurazan on gold and silver nanoisland films (NIFs) by means of surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS). The ligand is a push–pull molecule, where an intramolecular charge transfer occurs between an electron-donor and an electron-acceptor group, thus exhibiting nonlinear optical properties that are related to both SERS and SEF effects. The presence of different heteroatoms in the molecule ensures the possibility of chemical interaction with both silver and gold substrates. The SERS spectra suggest that furazan is bound to silver via lone pairs of the nitrogen atoms, whereas the ligand is linked to gold via a sulfur atom. Silver NIFs provide more efficient enhancement of both fluorescence and Raman scattering in comparison with gold NIFs. The present SEF and SERS investigation could provide useful information for foreseeing changes in the nonlinear responses of this push–pull molecule. FigureSurface-enhanced fluorescence on Ag and Au substrates

Intracellular Nanosensing and Nanodelivery by PMMA Nanoparticles

The delivery of fluorescent agents or probes to cells and tissues by using nanoparticles is currently receiving a growing interest because such nanodimensional structures can conveniently allow the preparation of small tools to spy at cellular mechanisms without interferences. We describe here the synthesis and characterization of fluorescently labeled cationic core–shell nanoparticles (NPs), made up of a core of polymethylmethacrylate (PMMA), surrounded by a shell bearing cationic groups, modified for nanosensing purposes. In particular, the NPs have been characterized as potential intracellular nanocarriers of molecular beacons (MB) for tumor mRNA sensing. Survivin targeting MBs have been used with Atto647N and Blackberry 650 as fluorophore/quencher pair. The MB was anchored to the surface of the PMMA nanoparticles via a commercial sulfhydryl-reactive heterobifunctional crosslinker and the achieved nanomaterials have been then characterized in vitro.

Modified multi-walled carbon nanotubes potentially suitable for intracellular pH measurements

Carboxylic acid functionalized multi-walled carbon nanotubes (COOH-MWCNTs) have been studied as macromolecular carriers for pH indicators to be used inside cells. The activation of carboxylic groups with thionyl chloride (SOCl2) followed by the reaction with a family of fluorescein ethylen glycol derivatives led to dyes covalently anchored to the MWCNT surface. Such a functionalization was found to preserve wholly the fluorescence properties of the dye ultimately providing higher water solubility to the modified macromolecular systems. Moreover, the use of a polyether spacer between the dye and the MWCNT surface preserved from undesired florescence quenching effects. The pH dependence of the modified nanotubes was investigated interrogating a solution of MWCNTs, the pH of which was adjusted in the range 4-9 pH units by adding drops of hydrochloric acid and sodium hydroxide. Light from LED was suitably filtered at 480 nm with a high pass-band filter and coupled to an optical fiber which illuminates the solution containing the fluorescein-functionalised MWCNTs. An optical fiber, at 90° with respect to the LED illumination, is connected with a Hamamtsu spectrum analyzer for the recording of the fluorescence spectra. The modified MWCNTs exhibited linear pH dependence in the range between 6 and 8 pH units with a sensitivity less than 0.1 pH units.

Nanostructured carbon materials decorated with organophosphorus moieties: synthesis and application

A new synthetic approach for the production of carbon nanomaterials (CNM) decorated with organophosphorus moieties is presented. Three different triphenylphosphine oxide (TPPO) derivatives were used to decorate oxidized multiwalled carbon nanotubes (ox-MWCNTs) and graphene platelets (GPs). The TPPOs chosen bear functional groups able to react with the CNMs by Tour reaction (an amino group), nitrene cycloaddition (an azido group) or CuAAC reaction (one terminal C–C triple bond). All the adducts were characterized by FTIR, Raman spectroscopy, TEM, XPS, elemental analysis and ICP-AES. The cycloaddition of nitrene provided the higher loading on ox-MWCNTs and GPs as well, while the Tour approach gave best results with nanotubes (CNTs). Finally, we investigated the possibility to reduce the TPPO functionalized CNMs to the corresponding phosphine derivatives and applied one of the materials produced as heterogeneous organocatalyst in a Staudinger ligation reaction.

Colorimetric resonant detection of biochemical agents in mesoporous silicon-based photonic crystals

A colorimetric resonant mesoporous silicon photonic crystal is used as a surface binding platform for biochemical detection. The photonic crystal, when illuminated with white light at normal incidence, is designed to reflect a photonic band gap (PBG) centered at a single wavelength. When molecules are attached to the internal surfaces of pores, the PBG is shifted due to the change in refractive index of the porous silicon layers. The planar structure of the platform can be easily integrated into a fluidic cell. We have optically verified the presence of proteins and chemicals as a colorimetric shift in the reflectivity spectrum of mesoporous silicon photonic crystals and microcavities.