13 research outputs found
Self-structuring of lamellar bridged silsesquioxanes with long side spacers
Diurea cross-linked bridged silsesquioxanes (BSs) C(10)C(11)C(10) derived from organosilane precursors, including decylene chains as side spacers and alkylene chains with variable length as central spacers (EtO)(3)Si- (CH(2))(10)-Y(CH(2))(n)-Y-(CH(2))(10)-Si(OEt)(3) (n = 7, 9-12; Y = urea group and Et = ethyl), have been synthesized through the combination of self-directed assembly and an acid-catalyzed sol gel route involving the addition of dimethylsulfoxide (DMSO) and a large excess of water. This new family of hybrids has enabled us to conclude that the length of the side spacers plays a unique role in the structuring of alkylene-based BSs, although their morphology remains unaffected. All the samples adopt a lamellar structure. While the alkylene chains are totally disordered in the case of the C(10)C(7)C(10) sample, a variable proportion of all-trans and gauche conformers exists in the materials with longer central spacers. The highest degree of structuring occurs for n = 9. The inclusion of decylene instead of propylene chains as side spacers leads to the formation of a stronger hydrogen-bonded urea-urea array as evidenced by two dimensional correlation Fourier transform infrared spectroscopic analysis. The emission spectra and emission quantum yields of the C(10)C(n)C(10) Cm materials are similar to those reported for diurea cross-linked alkylene-based BSs incorporating propylene chains as side spacers and prepared under different experimental conditions. The emission of the C(10)C(n)C(10) hybrids is ascribed to the overlap of two distinct components that occur within the urea cross-linkages and within the siliceous nanodomains. Time-resolved photoluminescence spectroscopy has provided evidence that the average distance between the siliceous domains and the urea cross-links is similar in the C(10)C(n)C(10) BSs and in oxyethylene-based hybrid analogues incorporating propylene chains as side spacers (diureasils), an indication that the longer side chains in the former materials adopt gauche conformations. It has also allowed us to demonstrate for the first time that the emission features of the urea-related component of the emission of alkylene-based BSs depend critically on the length of the side spacers
Tailoring the Hydrophilic/Lipophilic Balance of Clickable Mesoporous Organosilicas by the Copper-Catalyzed AzideâAlkyne Cycloaddition Click-Functionalization
International audienceWe have designed and synthesized a clickable bridgedsilsesquioxane material featuring pendant alkyne chains as an aggregate ofgolf-ball-like nanoparticles, as evidenced by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and small- and wide-angle X-ray scattering (SWAXS). Using the copper-catalyzed azideâalkyne cycloaddition reaction with a range of organic azides of variable characteristics, we transformed this parent bridged silsesquioxane into new materials with tunable hydrophilic/lipophilic balance in high conversions while preserving the original morphology. N2, cyclohexane, and water sorption experiments were used to quantify the affinity of these materials toward the sorbates through the determination of their Henryâs constants. This resulted in the following hydrophilic scale: M-OH > M-PEG > M-C6 > M-Ph > M-F > M-C16, which was mostly confirmed by SWAXS measurements
Syntheses and applications of periodic mesoporous organosilica nanoparticles
International audienc
Tailoring the Hydrophilic/Lipophilic Balance of Clickable Mesoporous Organosilicas by the Copper-Catalyzed AzideâAlkyne Cycloaddition Click-Functionalization
We
have designed and synthesized a clickable bridged silsesquioxane
material featuring pendant alkyne chains as an aggregate of golf-ball-like
nanoparticles, as evidenced by scanning electron microscopy (SEM),
transmission electron microscopy (TEM), and small- and wide-angle
X-ray scattering (SWAXS). Using the copper-catalyzed azideâalkyne
cycloaddition reaction with a range of organic azides of variable
characteristics, we transformed this parent bridged silsesquioxane
into new materials with tunable hydrophilic/lipophilic balance in
high conversions while preserving the original morphology. N<sub>2</sub>, cyclohexane, and water sorption experiments were used to quantify
the affinity of these materials toward the sorbates through the determination
of their Henryâs constants. This resulted in the following
hydrophilic scale: M-OH > M-PEG > M-C6 > M-Ph > M-F >
M-C16, which
was mostly confirmed by SWAXS measurements
Enhanced Collective Magnetic Properties in 2D Monolayers of Iron Oxide Nanoparticles Favored by Local Order and Local 1D Shape Anisotropy
Magnetic nanoparticle arrays represent
a very attractive research
field because their collective properties can be efficiently modulated
as a function of the structure of the assembly. Nevertheless, understanding
the way dipolar interactions influence the intrinsic magnetic properties
of nanoparticles still remains a great challenge. In this study, we
report on the preparation of 2D assemblies of iron oxide nanoparticles
as monolayers deposited onto substrates. Assemblies have been prepared
by using the LangmuirâBlodgett technique and the SAM assisted
assembling technique combined to CuAAC âclickâ reaction.
These techniques afford to control the formation of well-defined monolayers
of nanoparticles on large areas. The LB technique controls local ordering
of nanoparticles, while adjusting the kinetics of CuAAC âclickâ
reaction strongly affects the spatial arrangement of nanoparticles
in monolayers. Fast kinetics favor disordered assemblies while slow
kinetics favor the formation of chain-like structures. Such anisotropic
assemblies are induced by dipolar interactions between nanoparticles
as no magnetic field is applied and no solvent evaporation is performed.
The collective magnetic properties of monolayers are studied as a
function of average interparticle distance, local order and local
shape anisotropy. We demonstrate that local control on spatial arrangement
of nanoparticles in monolayers significantly strengthens dipolar interactions
which enhances collective properties and results in possible super
ferromagnetic order
Fast Assembling of Magnetic Iron Oxide Nanoparticles by Microwave-Assisted Copper(I) Catalyzed AlkyneâAzide Cycloaddition (CuAAC)
Two dimensional (2D) nanoparticles
(NP) assemblies have become
very attractive due to their original collective properties, which
can be modulated as a function of the nanostructure. Beyond precise
control on nanostructure and easy way to perform, fast assembling
processes are highly desirable to develop efficient and popular strategies
to prepare systems with tunable collective properties. In this article,
we report on the highly efficient and fast 2D assembling of iron oxide
nanoparticles on a self-assembled monolayer (SAM) of organic molecules
by the microwave (MW)-assisted copperÂ(I) catalyzed alkyneâazide
cycloaddition (CuAAC) click reaction. Microwave irradiation favors
a dramatic enhancement of the assembling reaction, which was completed
with maximum density in NPs within one hour, much faster than the
conventional CuAAC click reactions that require up to 48 h. Moreover,
the MW-assisted click reaction presents the great advantage to preserve
specific reactions between alkyne and azide groups at SAM and NP surfaces,
respectively, and also to avoid undesired reactions. To the best of
our knowledge, this is the first time this approach is performed to
nanoparticles assembled on surfaces
Mixed Periodic Mesoporous Organosilica Nanoparticles and CoreâShell Systems, Application to in Vitro Two-Photon Imaging, Therapy, and Drug Delivery
International audienceIn this work, we describe the synthesis of new Mixed Periodic Mesoporous Organosilica Nanoparticles (MPMO NPs), combining the co-condensation of a tetra-trialkoxysilylated twophoton photosensitizer with bis-(triethoxysilyl)phenylene or ethylene. Novel gold core-MPMO shell systems are also described. The MPMO NPs are analyzed and characterized by multiple techniques, and are very efficient for anti-cancer drug delivery combined with two-photon therapy in MCF-7 breast cancer cells, leading down to 76% cancer cell death. MPMO NPs are thus very promising for nanomedicine applications