Nanovalve-controlled cargo release activated by plasmonic heating

International audienc

Photo-driven expulsion of molecules from mesostructured silica nanoparticles

Azobenzene derivatives act as both impellers and gatekeepers when they are tethered in and on mesoporous silica nanoparticles. Continuous excitation at 457 nm, a wavelength where both the cis and trans conformers absorb, produces constant isomerization reactions and results in continual dynamic wagging of the untethered terminus. The 2 nm diameter pores are loaded with luminescent probe molecules, azobenzene motion is stimulated by light, and the photoinduced expulsion of the probe from the particles that is caused by the motion is monitored by luminescence spectroscopy. The light-responsive nature of these materials enables them to be externally controlled such that the expulsion of dye molecules from the mesopores can be started and stopped at will. These results open the possibilities of trapping useful molecules such as drugs and releasing them on demand

Isolation of Dysprosium and Yttrium Complexes of a Three-Electron Reduction Product in the Activation of Dinitrogen, the N23- Radical

International audienceDyI2 reacts with 2 equiv of KOAr (OAr ) OC6H3(CMe3)2-2,6) under nitrogen to form not only the (N2)2- complex, [(ArO)2(THF)2Dy]2(μ-η2:η2-N2), 1, but also complexes of similar formula with an added potassium ion, [(ArO)2(THF)Dy]2(μ-η2:η2-N2)[K(THF)6], 2, and [(ArO)2(THF)Dy]2(μ3-η2:η2:η2-N2)K(THF), 3. The 1.396(7) and 1.402(7) Å N-N bond distances in 2 and 3, respectively, are consistent with an (N2)3- ligand, but the high magnetic moment of 4f9 Dy3+ precluded definitive identification. The Y[N(SiMe3)2]3/K reduction system was used to synthesize yttrium analogues of 2 and 3, {[(Me3Si)2N]2(THF)Y}2(μ-η2:η2- N2)[K(THF)6] and {[(Me3Si)2N]2(THF)Y}2(μ3-η2:η2:η2-N2)K, that had similar N-N distances and allowed full characterization. EPR, Raman, and DFT studies are all consistent with the presence of (N2)3- in these complexes. 15N analogues were also prepared to confirm the spectroscopic assignments. The DFT studies suggest that the unpaired electron is localized primarily in a dinitrogen π orbital isolated spatially, energetically, and by symmetry from the metal orbitals

Shortwave infrared imaging with J-aggregates stabilized in hollow mesoporous silica nanoparticles.

Tissue is translucent to shortwave infrared (SWIR) light, rendering optical imaging superior in this region. However, the widespread use of optical SWIR imaging has been limited, in part, by the lack of bright, biocompatible contrast agents that absorb and emit light above 1000 nm. J-Aggregation offers a means to transform stable, near-infrared (NJR) fluorophores into red-shifted SWIR contrast agents. Here we demonstrate that J-aggregates of NIR fluorophore IR-140 can be prepared inside hollow mesoporous silica nanoparticles (HMSNs) to result in nanomaterials that absorb and emit SWIR light. The J-aggregates inside PEGylated HMSNs are stable for multiple weeks in buffer and enable high resolution imaging in vivo with 980 nm excitation

Photoisomerization of Azobenzene Derivatives in Nanostructured Silica

A series of derivatized azobenzene molecules are synthesized such that one of the phenyl groups can be chemically bonded to mesostructured silica and the other, derivatized with dendrons, is free to undergo large-amplitude light-driven motion. The silica frameworks on which the motion takes place are either 150 nm thick films containing ordered hexagonal arrays of tubes (inner diameter about 2 nm) containing the bonded azobenzenes, or particles (about 500 nm in diameter) containing the same ordered arrays of functionalized tubes. The photoisomerization yields and the rate constants for the thermal cis to trans back-reaction of the azobenzenes in the tubes are measured and compared to those of the molecules in solution. The rate constants decrease with increasing size of the dendrons. Fluorescence spectra of the cis and trans isomers in the pores show that the photoisomerization in the nanostructured materials is selectively driven by specific wavelengths of light and is reversible

Controlled multiple functionalization of mesoporous silica nanoparticles: homogeneous implementation of pairs of functionalities communicating through energy or proton transfers

International audienc

Dispersion and stability optimization of TiO2 nanoparticles in cell culture media

Accurate evaluation of engineered nanomaterial toxicity requires not only comprehensive physical−chemical characterization of nanomaterials as produced, but also thorough understanding of nanomaterial properties and behavior under conditions similar to those used for in vitro and in vivo toxicity studies. In this investigation, TiO2 nanoparticles were selected as a model nanoparticle and bovine serum albumin (BSA) was selected as a model protein for studying the effect of protein−nanoparticle interaction on TiO2 nanoparticle dispersion in six different mammalian, bacteria, and yeast cell culture media. Great improvement in TiO2 dispersion was observed upon the addition of BSA, even though the degree of dispersion varied from medium to medium and phosphate concentration in the cell culture media was one of the key factors governing nanoparticle dispersion. Fetal bovine serum (FBS) was an effective dispersing agent for TiO2 nanoparticles in all six media due to synergistic effects of its multiple protein components, successfully reproduced using a simple “FBS mimic” protein cocktail containing similar concentrations of BSA, γ-globulin, and apo-transferrin