Remote-control of the enantiomeric supramolecular recognition mediated by chiral azobenzenes bound to human serum albumin.

Three novel tyrosine-conjugated azobenzene molecules were designed and their ability to target a natural chiral host matrix (human serum albumin, HSA) was investigated. We found that the interplay between the spatial configuration of the chiral substituents and the change in local symmetry resulting from the photoisomerization process strongly affects the optical activity of the bound photochromes. In particular, the different signal amplification obtained upon binding of the photoswitches to the biopolymer enables obtaining a chirooptical system tunable over a wide range of wavelengths.

Photophysical, amplified spontaneous emission and charge transport properties of oligofluorene derivatives in thin films.

We investigate the photophysical and amplified spontaneous emission properties of a series of monodisperse solution-processable oligofluorenes functionalized with hexyl chains at the C9 position of each fluorene unit. Thin films of these oligofluorenes are then used in organic field-effect transistors and their charge transport properties are examined. We have particularly focused our attention on the influence of oligofluorene length on the absorption and steady-state fluorescence spectra, on the HOMO/LUMO energy levels, on the photoluminescence lifetime and quantum yield as well as on the amplified spontaneous emission properties and the charge carrier mobilities. Differential scanning calorimetry and X-ray diffraction measurements demonstrate that, among all oligofluorene derivatives used in this study, only the structure and morphology of the pentafluorene film is significantly modified by a thermal treatment above the glass transition temperature, resulting in a 9 nm blue-shift of the fluorescence spectrum without significant changes in the photoluminescence quantum yield and in the amplified spontaneous emission threshold. In parallel, hole field-effect mobility is significantly increased from 8.6 × 10(-7) to 3.8 × 10(-5) cm(2) V(-1) s(-1) upon thermal treatment, due to an increase of crystallinity. This study provides useful insights into the morphological control of oligofluorene thin films and how it affects their photophysical and charge transport properties. Moreover, we provide evidence that, because of the low threshold, the tunability of the amplified spontaneous emission and the photostability of the films, these oligofluorenes are promising candidates for organic solid-state laser applications.

Effective control of the intrinsic DNA morphology by photosensitive polyamines.

Non-viral vectors for gene therapy such as DNA-cationic probe complexes offer important bio-safety advantages over viral approaches, due to their reduced pathogenicity, immunogenicity and cytotoxicity. In the present study we examine two polycationic water-soluble azobenzene derivatives (bis-Azo-2N and bis-Azo-3N) containing different linear unsubstituted polyamine moieties and we demonstrate the ability of such photochromes to destabilize the intrinsic B-DNA secondary structure in a concentration-dependent manner. Furthermore, through a detailed series of biophysical experiments, varying the photochrome conformation, temperature, salt and DNA concentration, we provide a detailed insight into the azobenzene-DNA binding pathway (Ka: bis-Azo-2N(trans)-DNA = 5.3 ± 0.3 × 104 M-1, Ka: bis-Azo-2N(cis)-DNA = 2.6 ± 0.2 × 104 M-1, Ka: bis-Azo-3N(trans)-DNA = 7.1 ± 0.4 × 104 M-1 and Ka: bis-Azo-3N(cis)-DNA = 5.1 ± 0.4 × 104 M-1) establishing the versatility of such materials as promising candidates for use in non-viral gene delivery systems.

A Fluorescent Polymer Probe with High Selectivity toward Vascular Endothelial Cells for and beyond Noninvasive Two-Photon Intravital Imaging of Brain Vasculature.

A chromophore-engineering strategy that relies on the introduction of a ground-state distortion in a quadrupolar chromophore was used to obtain a quasi-quadrupolar chromophore with red emission and large two-photon absorption (2PA) cross-section in polar solvents. This molecule was functionalized with water-solubilizing polymer chains. It constitutes not only a remarkable contrast agent for intravital two-photon microscopy of the functional cerebral vasculature in a minimally invasive configuration but presents intriguing endothelial staining ability that makes it a valuable probe for premortem histological staining.

Linear and nonlinear optical properties of azobenzene derivatives.

The results of computations of spectroscopic parameters of lowest-lying electronic excited states of azobenezene derivatives are presented. The analysis of experimentally recorded spectra was supported by quantum chemical calculations using density functional theory. The theoretically determined resonant (two-photon absorption probabilities) and non-resonant (first-order hyperpolarisability) nonlinear optical properties are also discussed, with an eye towards the performance of recently proposed long-range corrected (LRC) schemes (LC-BLYP and CAM-B3LYP functionals).