1. Introduction 20642. Synthesis of Magnetic Nanoparticles 20662.1. Classical Synthesis by Coprecipitation 20662.2. Reactions in Constrained Environments 20682.3. Hydrothermal and High-TemperatureReactions20692.4. Sol-Gel Reactions 20702.5. Polyol Methods 20712.6. Flow Injection Syntheses 20712.7. Electrochemical Methods 20712.8. Aerosol/Vapor Methods 20712.9. Sonolysis 20723. Stabilization of Magnetic Particles 20723.1. Monomeric Stabilizers 20723.1.1. Carboxylates 20733.1.2. Phosphates 20733.2. Inorganic Materials 20733.2.1. Silica 20733.2.2. Gold 20743.3. Polymer Stabilizers 20743.3.1. Dextran 20743.3.2. Polyethylene Glycol (PEG) 20753.3.3. Polyvinyl Alcohol (PVA) 20753.3.4. Alginate 20753.3.5. Chitosan 20753.3.6. Other Polymers 20753.4. Other Strategies for Stabilization 20764. Methods of Vectorization of the Particles 20765. Structural and Physicochemical Characterization 20785.1. Size, Polydispersity, Shape, and SurfaceCharacterization20795.2. Structure of Ferro- or FerrimagneticNanoparticles20805.2.1. Ferro- and Ferrimagnetic Nanoparticles 20805.3. Use of Nanoparticles as Contrast Agents forMRI20825.3.1. High Anisotropy Model 20845.3.2. Small Crystal and Low Anisotropy EnergyLimit20855.3.3. Practical Interests of Magnetic NuclearRelaxation for the Characterization ofSuperparamagnetic Colloid20855.3.4. Relaxation of Agglomerated Systems 20856. Applications 20866.1. MRI: Cellular Labeling, Molecular Imaging(Inﬂammation, Apoptose, etc.)20866.2.

Magnetic Iron Oxide Nanoparticles: Synthesis, Stabilization, Vectorization, Physicochemical Characterizations, and Biological Applications

Diarylethenes for Memories and Switches

Lanthanide-based luminescent hybrid materials.

Organic–inorganic hybrid materials do not represent only a creative alternative to design new materials and compounds for academic research, but their improved or unusual features allow the development of innovative industrial applications. Nowadays, most of the hybrid materials that have already entered the market are synthesised and processed by using conventional soft chemistry based routes developed in the eighties. These processes are based on: a) the copolymerisation of functional organosilanes, macromonomers, and metal alkoxides, b) the encapsulation of organic components within sol–gel derived silica or metallic oxides, c) the organic functionalisation of nanofillers, nanoclays or other compounds with lamellar structures, etc. The chemical strategies (self-assembly, nanobuilding block approaches, hybrid MOF (Metal Organic Frameworks), integrative synthesis, coupled processes, bio-inspired strategies, etc.) offered nowadays by academic research allow, through an intelligent tuned coding, the development of a new vectorial chemistry, able to direct the assembling of a large variety of structurally well defined nano-objects into complex hybrid architectures hierarchically organised in terms of structure and functions. Looking to the future, there is no doubt that these new generations of hybrid materials, born from the very fruitful activities in this research field, will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.

Applications of hybrid organic–inorganic nanocomposites

Photoinduced motions in azo-containing polymers.

Functional hybrids are nanocomporie umterials lying at the interfoce of organic and inorganic realnts, whose high sersatility offers a wide range of possibilities to eloborate tailor-made materials in terms of chemical and physical properties. Because they present several advantogys for derigning materialy for opticol applications (versatile and relativrly facite chemistry, easy shaping and patierning, materials having good mechanical integrity and cacrdlent optical quality), numerous silica or/and silaxane tussed hytirid orgunic-inorganic materiois imve been developed in the past few years. The men striking examples of fonctional hybrids exhibiting emission properties (solid-state dye lasers rare-carth doped hybridslads, electronuminescent devices), absorption properties (photockiomic), nonlinear optical (NLO) porperties (second-order NLO properties, phoiochemical hole burning (PHB), photorefractivity), and sensing are sunimorized in this review.

Optical properties of functional hybrid organic-inorganic nanocomposites

We have studied by $^{29}\mathrm{Si}$ NMR the complete condensation kinetics in the conditions of rapid hydrolysis (acidic medium, water in excess) of three silicon alkoxides. The gelation of the tetravalent tetraethoxysilane (TEOS) takes several weeks, whereas the trivalent methyltriethoxysilane (MTEOS) and vinyltriethoxysilane (VTEOS) do not form gels. From a quantitative analysis of the data, we deduce that the first steps of the condensation proceed by progressive assembling of small organized units. This accounts for the very slow kinetics (logarithmic function of time), the occurrence of highly condensed agglomerates, and the absence of gelation in trivalent systems. For the tetravalent TEOS, this is followed by an aggregation phase, which has been studied both by NMR and small-angle x-ray scattering. The fractal dimension D=1.9 and the growing kinetics (cluster size increasing as a linear function of time) are consistent with reaction-limited cluster-cluster aggregation with preferential reactivity at the external cluster sites. Finally, we suggest that the progressive transformation of the sol phase into the gel phase after the gel time can be observed by comparing static and magic-angle-spinning NMR spectra.

Sol-gel condensation of rapidly hydrolyzed silicon alkoxides: A joint 29Si NMR and small-angle x-ray scattering study.

Lead magnesium niobate, Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/ (PMN), was prepared by a sol-gel technique using alkoxide precursors. The hydrolysis-condensation mechanism leads to a translucent gel which is dried under hypercritical conditions to avoid collapse of the porous texture. After drying, the aerogel exhibits a B-deficient pyrochlore structure which progressively inserts magnesium oxide when the temperature increases. Near 700{sup 0}C, this pyrochlore phase completely transforms into the PMN-perovskite phase. Above 1000{sup 0}C, the loss of lead oxide leads to the destabilization of the PMN-perovskite with formation of an A-deficient pyrochlore phase.

Low‐Temperature Route to Lead Magnesium Niobate

We have developed new transparent photochromic hybrid organic−inorganic materials in which the photochromic group belongs to the polymer network. These materials involving chemically bonded dithienylethene derivatives were prepared by the sol−gel process in the form of thin films a few microns thick. The thickness and refractive index of the sol−gel films either at 633 or 785 nm were determined both in the colored and discolored state by using the attenuated total reflection (ATR) method. Functionalized sol−gel films showed a large refractive index change in a nonabsorbing spectral region:  Δn ≈ 4 × 10-2 at 785 nm. This important variation due to the high photochrome content allowed us to design optical components used in the field of wave guiding.

Large and Stable Refractive Index Change in Photochromic Hybrid Materials

We have performed magnetic measurements on a diluted system of $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ nanoparticles $(d\ensuremath{\sim}7 \mathrm{nm})$, and on a ferritin sample. In both cases, the zero-field cooled (ZFC) peak presents a nonmonotonic field dependence, as has already been reported in some experiments, and discussed as possible evidence of resonant tunneling. Within simple assumptions, we derive expressions for the magnetization obtained in the usual ZFC, field cooled (FC) and thermoremanent magnetization (TRM) procedures. We point out that the ZFC-peak position is extremely sensitive to the width of the particle-size distribution, and give some numerical estimates of this effect. We propose to combine the FC magnetization with a modified TRM measurement, a procedure which allows a more direct access to the barrier distribution in a field. The typical barrier values that are obtained in this procedure show a monotonic decrease for increasing fields, as expected from the simple effect of anisotropy barrier lowering, in contrast with the ZFC results. From our measurements on $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ particles, we show that the width of the effective barrier distribution is slightly increasing with the field, an effect that is sufficient for causing the observed initial increase of the ZFC-peak temperatures.

/pdf/nonmonotonic-field-dependence-of-the-zero-field-cooled-4qnpj13jo3.pdf

Frederic Chaput

Papers

Optical properties of functional hybrid organic-inorganic nanocomposites

Sol-gel condensation of rapidly hydrolyzed silicon alkoxides: A joint 29Si NMR and small-angle x-ray scattering study.

Low‐Temperature Route to Lead Magnesium Niobate

Large and Stable Refractive Index Change in Photochromic Hybrid Materials

Nonmonotonic field dependence of the zero-field cooled magnetization peak in some systems of magnetic nanoparticles