Light-driven directed motion of azobenzene-coated polymer nanoparticles in an aqueous medium

Azobenzene-coated polymer nanoparticles in the 16-nm-diameter range act as phototriggered nanomotors combining photo to kinetic energy conversion with optical control through light intensity gradients. The grafted dyes act as molecular propellers: their photoisomerization supplies sufficient mechanical work to propel the particles in an aqueous medium toward the intensity minima with velocities of up to 15 μm/s. It is shown that nanoparticles can be driven over tens of micrometers by translating the intensity gradients in the plane. The analysis of the particles motion demonstrates the decisive role of photoisomerization in the transport with a measured driving force that is 3 to 4 orders of magnitude higher than optical forces.     

Synthesis of azide‐functionalized nanoparticles by microemulsion polymerization and surface modification by click chemistry in aqueous medium

Stable translucent aqueous suspensions of azide‐functionalized cross‐linked nanoparticles (NPs), with diameters in the 15–20 nm range, were prepared using two synthetic approaches. Copolymerization of azidomethylstyrene (VBN₃), styrene, and divinylbenzene in various oil‐in‐water microemulsions led to NPs with modulable azide contents (0.53–0.78 mmol/g) and surface over volume distributions. Surface modifications of reactive NPs bearing chlorobenzyl groups, produced by microemulsion copolymerization of vinylbenzylchloride, with sodium azide led to azido‐coated NPs with high densities of peripheral groups (0.13–0.45 mmol/g). It is shown that the nature of the surfactant used for the preparation of the microemulsion has an impact on the incorporation of VBN₃ in the polymer particles as well as on the surface reaction yield. The azide‐functionalized NPs were used as clickable polymeric scaffolds for the grafting of sparingly water‐soluble dansyl and fluorescein derivatives through copper(I)‐catalyzed azide‐alkyne cycloaddition in water in the presence of surfactants as solubilizing agents to produce fluorescent NPs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A “Multi-Heavy-Atom” Approach toward Biphotonic Photosensitizers with Improved Singlet-Oxygen Generation Properties

Two trispicolinate 1,4,7-triazacyclonane (TACN)-based ligands bearing three picolinate biphotonic antennae were synthetized and their Yb³⁺ and Gd³⁺ complexes isolated. One series differs from the other by the absence ( L¹ )/presence ( L² ) of bromine atoms on the antenna backbone, offering respectively improved optical and singlet-oxygen generation properties. Photophysical properties of the ligands, complexes and micellar Pluronic suspensions were investigated. Complexes exhibit high two-photon absorption cross-section combined either with NIR emission (Yb) or excellent ¹O₂ generation (Gd). The very large intersystem crossing efficiency induced by the combination of bromine atom and heavy rare-earth element was corroborated with theoretical calculations. The ¹O₂ generation properties of L² Gd micellar suspension under two-photon activation leads to tumour cell death, suggesting the potential of such structures for theranostic applications.     

4-Hydroxy-6-methoxyaurones with high-affinity binding to cytosolic domain of P-glycoprotein

A series of 4-hydroxy-6-methoxyaurones and 4,6-dimethoxyaurones has been synthesised and tested for their binding affinity toward the nucleotide-binding domain of P-glycoprotein, an ABC (ATP-Binding Cassette) transporter which mediates the resistance of cancer cells to chemotherapy. These compounds differ from each other by the nature of the substituent on the aurone B-ring. The binding affinity seems to be linked to the nature of the substituent, as well as to the presence or the absence of a hydroxy group at position 4. The most active compounds were 4'-bromo-4-hydroxy-6-methoxyaurone and 4-hydroxy-4'-iodo-6-methoxyaurone.     

Iron(II) carboxylate complexes based on a tetraimidazole ligand as models of the photosynthetic non-heme ferrous sites: synthesis, crystal structure, and Mössbauer and magnetic studies

The preparations, X-ray structures, and detailed physical characterization are presented for new complexes involving an iron(II) center, a tetraimidazole ligand (TIM), and different carboxylates. [Fe(TIM)(C(6)H(5)CH(2)CO(2))](ClO(4)) (1) crystallizes in the Pbca space group with a = 10.8947(13), b = 20.343(2), and c = 22.833(3) A, Z = 8, and V = 5060.6(11) A(3). [Fe(TIM)(CH(3)CO(2))](ClO(4)) (2) crystallizes in the Ia space group with a = 17.117(2), b = 10.3358(12), and c = 25.658(3) A, beta = 90.301(13) degrees, Z = 8, and V = 4539.5(9) A(3). In both structures, the iron(II) is hexacoordinated to the four N(imidazole) donors of the TIM ligand and the two O donors of a bidentate carboxylate. The flexibility of the carboxylate bidentate coordination, symmetrical or more or less asymmetrical, associated with the steric demand of the TIM ligand results in a remarkable versatility of the Fe(II)N(4)O(2) coordination geometry. The diversity in carboxylate bidentate coordination modes has allowed us to clearly show the importance of the structural and electronic effects, through IR and M?ssbauer spectroscopy, of this apparently tenuous carboxylate shift. Comparison of the structural and M?ssbauer properties of these complexes with the non-heme ferrous site of photosynthetic systems (i) shows that the metric parameters of site 2b, including the symmetrically chelated bidentate carboxylate, are closer to those of the non-heme ferrous site in the bacterial reaction centers of Rhodopseudomonas viridis and R. sphaeroides and (ii) suggests that the ligand environment of the non-heme ferrous center of PS 2 is close to the axially distorted octahedral symmetry resulting from an asymmetrical bidentate coordination of the -CO(2) motif, as in complex 1.     

Electrogeneration of a biotinylated poly(pyrrole-ruthenium(II)) film for the construction of photoelectrochemical immunosensor

A biotinylated photosensitive polymer was electrogenerated from on a ruthenium complex bearing biotin and pyrrole groups; the resulting polypyrrolic film allowed the bioaffine immobilisation of avidin and biotinylated cholera toxin and the photoelectrochemical detection of the corresponding antibody.     

Fluctuation-dissipation relations and energy landscape in an out-of-equilibrium strong-glass-forming liquid

We study the out-of-equilibrium dynamics following a temperature jump in a model for silica, a strong liquid, and compare it with the well known case of fragile liquids. We calculate the fluctuation-dissipation relation, from which it is possible to estimate an effective temperature T(eff) associated with the slow out-of-equilibrium structural degrees of freedom. We find the striking and unexplained result that, different from the fragile liquid cases, T(eff) is smaller than the bath temperature.