Development of Multifunctional Hybrid Coatings (Mechanically Resistant and Hydrophobic) Using Methyltrimethoxysilane-Diethoxydimethylsilane-Tetraethoxysilane Mixed Systems.

For many industrial applications, the simultaneous presence in a material of different functional properties is necessary. The main interest lies in making a single material more versatile and durable, less fragile and more efficient. In this study, two concomitant properties in the same material were mainly studied: resistance to cracking and the increase in its hydrophobic properties. The chosen process was the sol-gel route due to its versatility and the ease of formulating materials from various precursors in order to obtain (multi)functional materials. In this paper, sol-gel coatings were prepared with tetraethoxysilane, methyltrimethoxysilane and diethoxydimethylsilane as precursors. Tetraethoxysilane was mainly used to improve the material's mechanical properties, especially hardness, and silicon oil was added to improve its hydrophobic behavior. The integration of silicon oil was monitored via 29Si NMR. Microstructural characterizations were carried out to correlate the multi-scale properties with the microstructure of the derived films. Young's modulus and hardness were measured to highlight the effect of key formulation parameters on the mechanical strength of the coatings. The synergistic effect of these precursors is underlined as well as the beneficial effect of silicon oil (generated in situ or precondensed).

A review on solution- and vapor-responsive sensors for the detection of phthalates.

Phthalic acid esters, largely referred to as phthalates, are today acknowledged as important pollutants used in the manufacture of polyvinyl chloride (PVC)-based plastics, whose use extends to almost every aspect of modern life. The risk of exposure to phthalates is particularly relevant as high concentrations are regularly found in drinking water, food-contact materials and medical devices, motivating an immense body of research devoted to methods for their detection in liquid samples. Conversely, phthalate vapors have only recently been acknowledged as potentially important atmospheric pollutants and as early fire indicators; additionally, deposition of these vapors can pose significant problems to the proper functioning of spacecraft and diverse on-board devices, leading to major space agencies recognizing the need of developing vapor-responsive phthalate sensors. In this manuscript we present a literature survey on solution- and vapor-responsive sensors and analytical assays for the detection of phthalates, providing a detailed analysis of a vast array of analytical data to offer a clear idea on the analytical performance (limits of detection and quantification, linear range) and advantages provided by each class of sensor covered in this review (electrochemical, optical and vapor-responsive) in the context of their potential real-life applications; the manuscript also gives detailed fundamental information on the various physicochemical responses exploited by these sensors and assays that could potentially be harnessed by new researchers entering the field.

Influence of Hybrid Sol-Gel Crosslinker on Self-Healing Properties for Multifunctional Coatings.

Self-healing polymers are a new class of material that has recently received a lot of attention because of the lifespan improvement it could bring to multiple applications. One of the major challenges is to obtain multifunctional materials which can self-heal and exhibit other interesting properties such as protection against corrosion. In this paper, the effect of the incorporation of an aminosilane on the properties of a self-healing organic polymer containing disulfide bond is studied on films and coatings for aluminium AA2024-T3 using simple one step in situ synthesis. Hybrid coatings with enhanced anticorrosion properties measured by EIS were obtained thanks to the formation of a protective oxide interface layer, while exhibiting wound closure after exposition at 75 °C. The thermal, mechanical and rheological properties of the films with different aminosilane amounts were characterized in order to understand the influence of the slight presence of the inorganic network. Stiffer and reprocessable hybrid films were obtained, capable to recover their mechanical properties after healing. The nanocomposite structure, confirmed by TEM, had a positive effect on the self-healing and stress relaxation properties. These results highlight the potential of sol-gel chemistry to obtain efficient anticorrosion and self-healing coatings.

An innovative GC-MS, NMR and ESR combined, gas-phase investigation during chemical vapor deposition of silicon oxynitrides films from tris(dimethylsilyl)amine.

Tris(dimethylsilyl)amine (TDMSA) is used in the presence of O2 and NH3 for the atmospheric pressure chemical vapor deposition (CVD) of conformal, corrosion barrier silicon oxynitride (SiOxNy) films at moderate temperature. Plausible decomposition pathways taking place during the process, as well as resulting gas-phase by-products, are investigated by an innovative methodology, coupling solid-state films characteristics with gas phase analysis. Liquid NMR, gas chromatography coupled with mass spectrometry (GC-MS) and electron spin resonance (ESR) allow probing stable compounds and radical intermediate species in the gas phase. At least fifteen by-products are identified, including silanols, siloxanes, disilazanes, silanamines, and mixed siloxane-silanamine molecules, in addition to more usual compounds such as water. The radical dimethylsilane, Me2HSi˙, is noted across all experiments, hinting at the decomposition of the TDMSA precursor. Deposition of SiOxNy films occurs even in the absence of NH3, demonstrating the judicious choice of the silanamine TDMSA as a dual source of nitrogen and silicon. Additionally, the presence of Si-H bonds in the precursor structure allows formation of SiOxNy films at temperatures lower than those required by other conventional silazane/silanamine precursors. Addition of NH3 in the inlet gas supply results in lower carbon impurities in the films. The identified by-products and formulated decomposition and gas-phase reactions provide stimulating insight and understanding of the deposition mechanism of SiOxNy films by CVD, offering possibilities for the investigation of representative chemical models and process simulation.

Near-infrared/visible-emitting nanosilica modified with silylated Ru(II) and Ln(III) complexes.

Three luminescent silica-based nanohybrids were fabricated by grafting of silylated Ru(II) and Nd/Yb(III) complexes onto mesoporous silica nanoparticles obtained by microemulsion method. The prepared nanohybrids were characterized by Fourier transform-Raman spectroscopy, solid state-nuclear magnetic resonance, high resolution-transmission electron microscopy and scanning and transmission electron microscopy techniques. The chemical integrity and the grafting of all complexes inside MSNs nanopores as well as a good distribution of metal complexes onto MSNs surface were achieved for all nanohybrids. Photophysical results revealed that by monitoring the excitation on Ru(II) moieties from SiO 2 -RuNd and SiO 2 -RuYb nanohybrids, the sensitization of NIR-emitting Nd/Yb(III) ions were successfully detected via energy transfer processes. Energy transfer rates (k EnT) of 0.20 × 107 and 0.11 × 107 s-1 and efficiencies of energy transfer (η EnT) of 40% and 27.5% were obtained for SiO 2 -RuNd and SiO 2 -RuYb nanohybrids, respectively. These results confirm the preparation of promising dual (near-infrared/visible)-emitting silica-based nanohybrids as new nanotools for applications as nanosensores and nanomarkers.

Luminescent nanohybrids based on silica and silylated Ru(II)-Yb(III) heterobinuclear complex: new tools for biological media analysis.

Lanthanide (Ln) complexes emitting in the near-infrared (NIR) region have fostered great interest as upcoming optical tags owing to their high spatial and temporal resolution emission as well deeper light penetration in biological tissues for non-invasive monitoring. For use in live-cell imaging, lanthanide complexes with long-wavelength absorption and good brightness are especially critical. Light-harvesting ligands of Ln complexes are typically excited in the ultraviolet region, which in turn trigger simultaneously autofluorescence and long-exposition damage of living systems. The association of d-metalloligands rather than organic chromophores enables the excitation of NIR-emitting Ln complex occurs in the visible region. Taking advantage of the long-lived excited states and intense absorption band in the ultraviolet (UV) to NIR region of Ru(II), we successfully design a dual-emitting (in the visible and NIR region) d-f heterobinuclear complex based on Ru(II) metalloligand and Yb(III) complex. In addition, we developed luminescent nanohybrids by grafting of Ru(II)-Yb(III) heterobinuclear complexes containing silylated ligands on the surface of mesoporous and dense silica matrix. The nanomarkers were successfully applied for imaging of murine melanoma B16-F10 and neonatal human dermal fibroblast HDFn cell cultures by one-photon or two-photon absorption using laser scanning confocal microscopy. Great cellular uptake, low cytotoxicity and the possibility to achieve visible and NIR emission via two-photons excitation show that the nanohybrids are remarkable markers for in vitro and a potential tool for in vivo applications.

Improvement of Adhesion Properties and Corrosion Resistance of Sol-Gel Coating on Zinc.

Corrosion is a major problem for durability of many metals and alloys. Among the efficient classical surface treatments, chromate-based treatments must be banished from industrial use due to their toxicity. At the same time, sol-gel routes have demonstrated high potential to develop an efficient barrier effect against aggressive environments. By this process, the anti-corrosion property can be also associated to others in the case of the development of multi-functional hybrid coatings. In this paper, the main goal is precisely to improve both the corrosion resistance and the adhesion properties of phosphated zinc substrates by the deposition of a hybrid (organic-inorganic) sol-gel layer. To reach this double objective, a choice between two formulations 3-glycidoxypropyltrimethoxysilane (GPTMS)/aluminum-tri-sec-butoxide (ASB) and 3-(trimethoxysilyl)propylmethacrylate (MAP)/tetraethylorthosilicate (TEOS) was firstly made based on the results obtained by microstructural characterizations using SEM, optical analysis, and mechanical characterization such as shock and/or scratch tests (coupled to climatic chamber and salt spray exposure). Several investigations were performed in this study, and the best formulation and performances of the system were obtained by adding a new precursor (1-[3-(trimethoxysilyl)propyl]ureido-UPS) under controlled conditions, as detailed in this paper.

Innovative Formulation Combining Al, Zr and Si Precursors to Obtain Anticorrosion Hybrid Sol-Gel Coating.

The aim of our study is to improve the aluminium alloy corrosion resistance with Organic-Inorganic Hybrid (OIH) sol-gel coating. Coatings are obtained from unusual formulation with precursors mixing: glycidoxypropyltrimethoxysilane (GPTMS), zirconium (IV) propoxide (TPOZ) and aluminium tri-sec-butoxide (ASB). This formulation was characterized and compared with sol formulations GPTMS/TPOZ and GPTMS/ASB. In each formulation, a corrosion inhibitor, cerium (III) nitrate hexahydrate, is employed to improve the corrosion performance. Coatings obtained from sol based on GPTMS/TPOZ/ASB have good anti-corrosion performances with Natural Salt Spray (NSS) resistance of 500 h for a thickness lower than 4 µm. Contact angle measurement showed a coating hydrophobic behaviour. To understand these performances, nuclear magnetic resonance (NMR) analyses were performed, results make sol-gel coating condensation evident and are in very good agreement with previous results.

Organosilylated complex [Eu(TTA)3(Bpy-Si)]: a bifunctional moiety for the engeneering of luminescent silica-based nanoparticles for bioimaging.

A new highly luminescent europium complex with the formula [Eu(TTA)3(Bpy-Si)], where TTA stands for the thenoyltrifluoroacetone, (C4H3S)COCH2COCF3, chelating ligand and Bpy-Si, Bpy-CH2NH(CH2)3Si(OEt)3, is an organosilyldipyridine ligand displaying a triethoxysilyl group as a grafting function has been synthesized and fully characterized. This bifunctional complex has been grafted onto the surface of dense silica nanoparticles (NPs) and on mesoporous silica microparticles as well. The covalent bonding of [Eu(TTA)3(Bpy-Si)] inside uniform Stöber silica nanoparticles was also achieved. The general methodology proposed could be applied to any silica matrix, allowed high grafting ratios that overcome chelate release and the tendency to agglomerate. Luminescent silica-based nanoparticles SiO2-[Eu(TTA)3(Bpy-Si)], with a diameter of 28 ± 2 nm, were successfully tested as a luminescent labels for the imaging of Pseudomonas aeruginosa biofilms. They were also functionalized by a specific monoclonal antibody and subsequently employed for the selective imaging of Escherichia coli bacteria.

An efficient route to aqueous phase synthesis of nanocrystalline γ-Al2O3 with high porosity: from stable boehmite colloids to large pore mesoporous alumina.

In this paper we emphasise the important role of Pluronic F127 on the porosity of mesoporous alumina prepared from boehmite colloids. By focusing on the F127/boehmite interactions we show how the concepts of interface science may help to predict and improve the textural characteristics of mesoporous alumina. By varying the synthetic parameters, in particular the copolymer content, we show that the porosity of γ-Al(2)O(3) can be enhanced by 400% and the average pore diameter can be expanded from 5 to 14 nm. These results are discussed in terms of interactions between the Pluronic F127 and boehmite colloids, and are correlated to the critical micelle concentration (CMC) of the copolymer. The textural characteristics of the mesoporous alumina can be further improved either by introducing hydrocarbons in the preformed boehmite/copolymer sols or by concentrating the sols. In comparison with as-synthesised alumina, those prepared with F127 showed improved thermal stability. Furthermore, boehmite/copolymer sols were stable for all surfactant concentrations investigated and can give high quality coatings suitable for catalytic applications.

Rheological behaviour and spectroscopic investigations of cerium-modified AlO(OH) colloidal suspensions.

The rheological behaviour of aqueous suspensions of boehmite (AlO(OH)) modified with different Ce-salts (Ce(NO(3))(3), CeCl(3), Ce(CH(3)COO)(3) and Ce(2)(SO(4))(3)) was investigated at a fixed Ce/Al molar ratio (0.05). Freshly prepared boehmite suspensions were near-Newtonian and time-independent. A shear-sensitive thixotropic network developed when Ce-salts with monovalent anions were introduced in the nanoparticle sols. The extent of particle aggregation dramatically increased with ageing for Ce(NO(3))(3) and CeCl(3) whereas an equilibrium value was reached with Ce(CH(3)COO)(3). The addition of Ce(2)(SO(4))(3) with divalent anions involved no thixotropy but rather a sudden phase separation. The combined data set of IRTF and DRIFT spectra indicated that free NO(3)(-) anions of peptized boehmite adsorb on the nanoparticle surface by H-bond. The introduction of Ce-salts in the boehmite sol led to the coordination between Ce(3+) ions and NO(3)(-) anions adsorbed on boehmite i.e. to [Ce(NO(3))(4)(H(2)O)(x)](-) complex. Such coordination led to a thixotropic behaviour which was lower with Ce(NO(3))(3) compared to CeCl(3) and Ce(CH(3)COO)(3). In contrast, Ce(2)(SO(4))(3) formed insoluble complexes with dissolved aluminium species. The formation of H-bonded surface nitrate complexes was found to play a decisive role on the particle-particle interactions and consequently on the rheological behaviour of the sols.

Electrophoretic silica-coating process on a nano-structured copper electrode.

A method for silica-coating at the nanoscale by electrophoretic deposition is presented here, using raw or grafted silica dispersions.

Europium(III) complexes containing organosilyldipyridine ligands grafted on silica nanoparticles.

This work focuses on the grafting of transition metal complexes on silica surface nanoparticles. Nanoscale silica particles in aqueous sols are used as starting silicated materials. We have undertaken the synthesis of europium(III) complexes containing organosilyldipyridine ligands, (EtO)3Si(CH2)3NHCH2-bipy (1) and (EtO)(CH3)2Si(CH2) 3NHCH 2-bipy (2), in view of a direct grafting reaction on silica nanoparticles. Reaction of one molar equivalent of 1 and 2 with Eu(tmhd)3 (tmhd= 2,2,6,6-tetramethyl-3,5-heptanedionato), as precursor, leads to octacoordinated silylated europium(III) complexes [Eu(tmhd)3(1)] (3) and [Eu(tmhd)3(2)] (4) as white solids in 34-54% yields. Europium complexes were characterized by elemental analysis, mass spectrometry, FT-IR, UV, and luminescence spectroscopies. These new complexes are reacting in a 1:10 (v/v) water and ethanol mixture with silica nanoparticles colloidal sol. Elemental analysis and thermogravimetric data indicated grafting ratios of 0.41 and 0.26 mmol of europium(III) complexes per gram of silica. Functionalized silica nanoparticles were characterized by DRIFT spectroscopy and TEM microscopy. The first analysis shows that the chemical integrity of the complexes is retained on the silica surface together with the size and the monodispersity of the nanoscale particles. As expected for europium(III) complexes, luminescence is observed under UV irradiation. Emission and excitation spectra indicate that the metal coordination environment is not modified on the silica surface. Moreover, the sharpness of the luminescence bands and the strong antenna effect are maintained when complexes are covalently bonded to silica. New luminescent europium(III) complexes grafted on silica nanoparticles are therefore obtained from our approach.