Photoactive nanostructured hybrid materials for optical and biomedical applications

198 p.Along this manuscript different hybrid materials are synthesized and extensively characterized for several used: from optical to therapeutic applications. First, by the incorporation of different dyes, styryl 722 and pyronine into several smectite clay films, macroscopically ordered systems are obtained. The effect of the clay on the dye is deeply analysed and its preferential orientation is studies by anisotropic response of the films to the linear polarized light. Second, large monoliths with embedded laser dyes with strong absorption and fluorescence bands in different region of the visible spectrum are attained by sol gel chemistry to obtain solid-state dye laser (SSDL) with good photo, thermal and chemical stabilities. Third, silica NP (NP) with suitable size (50 nm) and functionalized external surface are also synthesized by sol gel chemistry. Through the encapsulation of fluorescent dye molecules in their core and by the grafting of the photosensitizers on their shell, biocompatible nanoparticles for bio-imaging and photodynamic therapy (PDT) applications are prepared. In order to optimize their properties, a careful investigation of the photophysical properties and mainly the singlet oxygen generation of a large range of new photosensitizer based on chromophores known as BODIPYs, is previously carried out. Based on the results, some efficient BODIPYs are selected for grafting on silica nanoparticles in order to use them for PDT.Université de Pau et des pays de L'Adour CNRS Laboratory for Molecular Spectroscopy IPREM. Institut des sciences analytiques et de physico-chimie pour l'environnement et des matériau

Photoactive nanostructured hybrid materials for optical and biomedical applications

198 p.Along this manuscript different hybrid materials are synthesized and extensively characterized for several used: from optical to therapeutic applications. First, by the incorporation of different dyes, styryl 722 and pyronine into several smectite clay films, macroscopically ordered systems are obtained. The effect of the clay on the dye is deeply analysed and its preferential orientation is studies by anisotropic response of the films to the linear polarized light. Second, large monoliths with embedded laser dyes with strong absorption and fluorescence bands in different region of the visible spectrum are attained by sol gel chemistry to obtain solid-state dye laser (SSDL) with good photo, thermal and chemical stabilities. Third, silica NP (NP) with suitable size (50 nm) and functionalized external surface are also synthesized by sol gel chemistry. Through the encapsulation of fluorescent dye molecules in their core and by the grafting of the photosensitizers on their shell, biocompatible nanoparticles for bio-imaging and photodynamic therapy (PDT) applications are prepared. In order to optimize their properties, a careful investigation of the photophysical properties and mainly the singlet oxygen generation of a large range of new photosensitizer based on chromophores known as BODIPYs, is previously carried out. Based on the results, some efficient BODIPYs are selected for grafting on silica nanoparticles in order to use them for PDT.Université de Pau et des pays de L'Adour CNRS Laboratory for Molecular Spectroscopy IPREM. Institut des sciences analytiques et de physico-chimie pour l'environnement et des matériau

Fully Functionalizable β,β'-BODIPY Dimer: Synthesis, Structure, and Photophysical Signatures

The versatility in the synthesis of BODIPY derivatives in terms of functionalization is further demonstrated. Particularly, in this work β−β’-BODIPY dimers with varied functional groups in the meso-positions were synthetized in a very efficient yields and short reaction times from a single platform. A photophysical study was carried in all the compounds. The resultant dimers show absorption bands at around 600 nm as a consequence of electronically coupled monomers disposed with a dihedral angle of around 30º, which is supported by theoretical simulations. The emission properties of these molecules are distinguished by the appearance of an ICT state as the polarity of the solvent increases.Financial support from Gobierno Vasco (IT912-16), Ministerio de Economía y Competitividad “MINECO” (MAT2017-83856-C3-3-P), and CONACyT (grants 253623, 123732) is acknowledged. I. J. A.-C. thanks CONACyT for graduate scholarship. Donation of 2,6-dimethyl-8-methylthioBODIPY by Cuantico de Mexico (www.cuantico.mx) is appreciated

Molecular Forces Governing Shear and Tensile Failure in Clay-Dye Hybrid Materials

Hybrid materials based on photoactive molecules confined into nanostructured substrates are very promising for technological applications. However, little is known about the impact of organic dyes on the mechanical properties of the substrate, a key aspect for their practical implementation. In this work, we use atomistic simulation methods to investigate the mechanical properties of two hybrid systems consisting on a clay matrix (laponite) loaded with two different cationic dyes (LDS-722 and pyronin Y). We applied tensile and shear deformations to the layered hybrid materials and characterize the key mechanism triggering their failure. It has been observed that the water and dye molecules located in the interlaminar spaces are those involved in the deformation processes, while the structure of the laponite layers does not change. Furthermore, it has been also found that the incorporation of dye molecules modifies the hydrogen-bonding network of water in the interlaminar space, worsening the mechanical properties of the hybrids with respect to the clay. The information obtained by molecular simulation help us to assess the mechanical behavior of these materials, and to design materials with tailored strength

Rational Design of Advanced Photosensitizers Based on Orthogonal BODIPY Dimers to Finely Modulate Singlet Oxygen Generation

The synthesis, photophysical characterization, and modeling of a new library of halogen-free photosensitizers (PS) based on orthogonal boron dipyrromethene (BODIPY) dimers are reported. Herein we establish key structural factors in order to enhance singlet oxygen generation by judiciously choosing the substitution patterns according to key electronic effects and synthetic accessibility factors. The photosensitization mechanism of orthogonal BODIPY dimers is demonstrated to be strongly related to their intrinsic intramolecular charge transfer (ICT) character through the spin-orbit charge-transfer intersystem crossing (SOCT-ISC) mechanism. Thus, singlet oxygen generation can be effectively modulated through the solvent polarity and the presence of electron-donating or withdrawing groups in one of the BODIPY units. The photodynamic therapy (PDT) activity is demonstrated by in vitro experiments, showing that selected photosensitizers are efficiently internalized into HeLa cells, exhibiting low dark toxicity and high phototoxicity, even at low PS concentration (0.05–5×10−6 m)

Adapting BODIPYs to singlet oxygen production on silica nanoparticles

International audienceA modified Stober method is used to synthesize spherical core-shell silica nanoparticles (NPs) with an external surface functionalized by amino groups and with an average size around 50 nm. Fluorescent dyes and photosensitizers of singlet oxygen were fixed, either separately or conjointly, respectively in the core or in the shell. Rhodamines were encapsulated in the core with relatively high fluorescence quantum yields (Φfl ≥ 0.3), allowing fluorescence tracking of the particles. Various photosensitizers of singlet oxygen (PS) were covalenty coupled to the shell, allowing singlet oxygen production. The stability of NP suspensions strongly deteriorated upon grafting the PS, affecting their apparent singlet oxygen quantum yields. Agglomeration of NPs depends both on the type and on the amount of grafted photosensitizer. New, lab-made, halogenated 4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPY) grafted to the NPs achieved higher singlet oxygen quantum yields (ΦΔ ∼ 0.35-0.40) than Rose Bengal (RB) grafted NPs (ΦΔ ∼ 0.10-0.27). Finally, we combined both fluorescence and PS functions in the same NP, namely a rhodamine in the silica core and a BODIPY or RB grafted in the shell, achieving the performance Φfl ∼ 0.10-0.20, ΦΔ ∼ 0.16-0.25 with a single excitation wavelength. Thus, proper choice of the dyes, of their concentrations inside and on the NPs and the grafting method enables fine-tuning of singlet oxygen production and fluorescence emission.[on SciFinder (R)

Singlet Fission Mediated Photophysics of BODIPY Dimers

The photodynamics of an orthogonal BODIPY dimer, particularly the formation of triplet states, has been explored by femtosecond and nanosecond transient absorption measurements. The short time scale data show the appearance of transient features of triplet character that, according to quantitative analysis of their intensities, account for more than 100% of the initially excited molecules, which reveals the occurrence of a singlet fission process in the isolated dimers. The formation rate of the triplet correlated state 1(TT) is found to depend on the solvent polarity, pointing to the mediation of a charge transfer character state. The dissociation of the 1(TT) state into pairs of individual triplets determines the triplet yield measured in the long time scales. The kinetic model derived from the results provides a comprehensive view of the photodynamics of BODIPY dimers and permits rationalization of the photophysical parameters of these systems