Gerardo Abbandonato | Scuola Normale Superiore (original) (raw)

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Papers by Gerardo Abbandonato

Liquid Crystals, 2012

The orientational order parameters, Szz and Biax, of UB-d4 [1,4-bis(undec-10-en-1-yloxy)benzene-d... more The orientational order parameters, Szz and Biax, of UB-d4 [1,4-bis(undec-10-en-1-yloxy)benzene-d4] in the ZLI1167 nematic mixture are studied by means of H NMR at variable temperature. The Szz(T) trend fairly follows the Maier–Saupe theoretical curve; therefore, UB-d4 can be considered an excellent probe to monitor the ordering of the nematic phase itself, provided that Biax is not neglected and the complete analysis of quadrupolar and dipolar splittings is performed. UB-d4 is a typical crosslinker in liquid crystal elastomers (LCEs): the order parameters here collected help us to discuss the peculiarities of the crosslinker as a probe for the study of internal order in LCEs. From the analysis of our data and of data in the literature, we infer that the order parameter Biax of the crosslinker in the LCE matrix is low enough to be neglected without severely perturbing the determination of . The crosslinker UB-d4 is a reliable probe to monitor the nematic order degree inside the LSCE-UB-d4 sample.

The aggregation of perfluoroctanoate salts in H 2 O is studied by 19 F NMR on solutions of LiPFO,... more The aggregation of perfluoroctanoate salts in H 2 O is studied by 19 F NMR on solutions of LiPFO, NaPFO, and CsPFO, without and with the addition of two poly(ethylene glycol) (PEG) oligomers of molecular weight 1500 and 3400 Da, respectively, and with the addition of suitable crown ethers. The 19 F chemical shift (cs) trends are monitored, at 25°C, in a concentration range including the critical micellar concentration (cmc) or, in the presence of PEG, the critical aggregation concentration (cac). The cac values in the samples with PEG are lower than the cmc values of the corresponding samples without PEG; moreover, the 19 F cs trends above the cac and above the polymer saturation concentration reveal and help to explain some peculiarities of the aggregation process of PEG on PFO micelles, which, in the first step, seems to occur while the surfactant concentration in water is still increasing. Also in LiPFO/H 2 O or NaPFO/H 2 O solutions containing 12-crown-4 or 15-crown-5 ethers, suitable to complex Li þ or Na þ ions, respectively, the cmc decreases. On the other hand, the micellization process in the presence of crown ethers does not show other peculiarities. The prevailing conformations of the PFO chain are discussed on the basis of quantum-mechanical calculations. The theoretical chemical shifts were computed at the DFT level of theory, taking into account the effects of the environment by means of the IEF-PCM method. The helical structure is the most stable one, but anti conformations are easily accessible, in both the aqueous and fluorinated environment. The comparison between computed and experimental chemical shifts indicates that anti conformations are more important in the micelles than in water and in CsPFO micelles than in LiPFO or NaPFO ones.

Biophysical Journal, 2014

The journal of physical chemistry. B, Jan 22, 2015

Dual fluorescence is an anomalous photophysical phenomenon observed in very few chromophores in w... more Dual fluorescence is an anomalous photophysical phenomenon observed in very few chromophores in which a two-color radiative process occurs that involves two distinct excited electronic states. To date its observation was linked either to electronic rearrangement of an excited fluorophore leading to two conformers with distinct emissive properties, or to a photochemical modification leading to different fluorescent species. In both cases, emission originates from the lowest excited state of the resulting molecular configurations, in line with the so-called Kasha's rule. We report here a combined theoretical and spectroscopic study showing, for the first time, an anti-Kasha dual-emission mechanism, in which simultaneous two-color emission takes place from the first and second excited state of a coumarin derivative. We argue that the observed environmental sensitivity of this peculiar optical response makes the present compound ideally suited for bio-sensing applications in living ...

European Biophysics Journal, 2011

The photoswitching behaviour of the green fluorescent protein (GFP) chromophore and its analogs o... more The photoswitching behaviour of the green fluorescent protein (GFP) chromophore and its analogs opens up exciting horizons for the engineering and development of molecular devices for high sensitivity in vivo studies. In this work we present the synthesis and photophysical study of four GFP chromophore analogs belonging to butenolide and pyrrolinone classes. These chromophores possess an intriguing photoinduced cistrans isomerization mechanism. Stereochemical structural assignment was unambiguously performed by 1D Nuclear Overhauser Effect NMR measurements. The spectroscopic properties of both cis and trans isomers were studied, and photoconversion quantum yield for cis-trans isomerization was assessed to be in the 0.1-0.4 range. Finally, the 3 J C,H coupling constant in the 13 C-C=C-H motif was in excellent agreement with theoretical DFT calculations, thus providing a further confirmation of cis-trans photoisomerization of the structurally analog GFP chromophore.

Chemical Communications, 2013

A fluorescent probe structurally similar to the GFP chromophore is demonstrated to report the loc... more A fluorescent probe structurally similar to the GFP chromophore is demonstrated to report the local static dielectric constant. This probe can be chemically functionalized for selective targeting at the intracellular level. † Electronic supplementary information (ESI) available: Materials and methods, synthesis of compounds, Tables S1-S3, Schemes S1-S3, -S7, chromatographic analysis and mass spectra. See