Fullerene Derivatives Embedded in Hybrid Sol-Gel Glasses: Nonlinear Optical Properties and Optical Limiting Performances

Hybrid organic-inorganic materials are investigated as suitable materials for inclusion of fullerene derivatives and for fabrication of laser protection devices. A specific synthesis has been developed in order to optimize non-linear optical performances of fullerene derivatives. 3-glicydoxypropyltrymethoxysilane has been used as an inorganic and organic network former to obtain the host material. The sol-gel synthesis consists of the hydrolysis and condensation in acidic conditions of the inorganic network. Epoxy polymerization has been achieved by using zirconium or BF₃ alkoxides precursors. Bulk and multilayer materials doped with a fullerene derivative have been fabricated. They show good optical requirements: high fullerenes concentration, high microstructural homogeneity, high laser damage threshold and high optical limiting efficiency. Optical limiting (OL) mechanisms have been investigated. The most effective in the sol-gel materials is the reverse saturable absorption (RSA) one. However, different mechanisms, like non-linear (NL) scattering and NL refraction contribute to a different extent. Open- and closed-aperture OL and z-scan measurements on sol-gel samples show the contribution of NL scattering and NL refraction at 690 nm. Laser damage threshold has been characterized as a function of the structure of the samples and of the optical configurations (f/66 and f/5).     

Mechanical Properties of 3-Glycidoxypropyltrimethoxysilane Based Hybrid Organic-Inorganic Materials

Hybrid organic-inorganic materials were synthesized from acid catalysed sols of tetraethyl orthosilicate, 3-glycidoxypropyltrimethoxysilane and titanium or zirconium alkoxides. The mechanical properties of these materials were measured in different conditions of preparation. The elastic modulus E was determined by a resonance method and by Knoop microindentation. After a thermal treatment at 125°C for 120 h, E was around 3–5 and 1–2 GPa for the samples synthesized with titanium butoxide or zirconium butoxide, respectively. An increase in E in the samples cured for longer times was observed. Knoop microhardness also increased with the heating time and was larger in samples synthesized from titanium alkoxides than zirconium alkoxides. The two methods gave results in good agreement when applied to samples treated for shorter times. In the other samples Knoop microindentation gave a larger value of E compared to the resonance vibration method. Hardness to elastic modulus ratio, H/E, was evaluated by Knoop microindentation. The elastic recovery at the longest heat treatment time was similar to that of soda-lime glasses. Fracture toughness was measured by three points flexural test, a _KIc in the range of 0.4–0.5 MPa m^1/2 was evaluated for samples treated during 168 h.     

Hybrid Organic-Inorganic Sol-Gel Materials Based on Epoxy-Amine Systems

Understanding the synthesis-structure-properties relationship of hybrid organic-inorganic materials is an important and fundamental task to develop a new generation of highly performing systems for the new needs of nanotechnologies. This issue is, also, important to improve the properties of hybrids when used in applications where nanoscale control is not a fundamental request. In this article, a short overview of epoxy amine sol-gel hybrids is reported. The synthesis of these materials has a large flexibility to allow the fabrication of a wide group of hybrids with different structures and properties, whose applications are ranging from non-linear optics to adhesive and protective coatings.     

Induced Absorption of C60 and a Water-Soluble C60-Derivative in SiO2 Sol-Gel Matrices

Porous sol-gel glasses, either impregnated with pure C₆₀ or doped with a methanofullerene derivative, have been studied and induced absorption or reverse saturable absorption (RSA) has been observed in both types of solid materials. The samples impregnated by pure C₆₀ mainly contain well-dispersed fullerene molecules. Unlike crystalline films of C₆₀, their absorption dynamics can be well described by a 5-level model, developed for non-interacting C₆₀-molecules in solutions. Methanofullerene samples, on the other hand, show signs of micellar aggregation and therefore RSA dynamics that are influenced by solid state effects. We observe an important decrease of transmission at high fluences for both kinds of samples, a shortened singlet-state lifetime to that observed in solution, but nonetheless, a triplet yield, that cannot be considered as negligible. In the case of pure C₆₀ in a sol-gel matrix, we can explain the faster de-excitation dynamics, relative to behavior in solution, mainly by the absence of stabilizing aromatic solvents and also by the interaction of the amorphous environment with the molecules. Concerning the methanofullerene samples, the acceleration of the de-excitation dynamics can be principally attributed to solid-state effects due to the micellar aggregation.     

Preparation and Characterization of Fullerenes Containing Sol-Gel Glass

Transparent materials containing C₆₀ are interesting because of their optical limiting properties. Fullerenes can be incorporated in sol-gel matrices, but their poor solubility in the solvents commonly used in the process and their tendency to form clusters constitutes the main experimental problem. For this reason we have synthesized C₆₀ derivatives with high solubility and having reactive groups that could covalently bond to the inorganic network. By this way and by an optimization of the sol-gel preparation procedure, transparent films and bulks were obtained. Good optical limiting performances were demonstrated by experimental measurements.     

Fullerenes in Sol-Gel Materials

The family of fullerene molecules is composed of a large variety of compounds that have been synthesized following the discovery of C₆₀ in 1985. The chemistry of fullerenes, developed in these last years, has allowed designing the properties of this family of molecules for specific applications in materials science. One of the main tasks to build up solid state devices based on fullerenes is the synthesis of materials doped with a highly dispersed and homogeneous distribution of fullerenes. Many of the peculiar photophysical properties, such as the reverse saturable absorption used to obtain a solid state optical limiter, are in fact lost in the aggregates of fullerenes. Sol-gel processing allows preparing inorganic oxides and hybrid organic-inorganic materials at low temperatures and presents an interesting alternative to organic polymers to entrap molecules of the fullerene family in a solid matrix. Porous inorganic solids and aerogels are also important classes of materials that can be synthesized via sol-gel and can act as hosts of fullerenes. In the present article we have reviewed the main achievements of sol-gel processing of fullerene based nanocomposite materials.     

溶胶-凝胶法制备有机/无机杂化材料工艺及其应用

介绍了溶胶–凝胶法制备有机/无机杂化材料的原理和基本过程,杂化材料的制备方法及对材料性能的影响,概述了杂化材料在结构材料、光学材料及其它材料中的应用研究。     

Reverse Saturable Optical Absorption of C60, Soluble Methanofullerenes, and Fullerodendrimers in Sol-Gel Mesoporous Silica Host Matrices

Porous sol-gel glasses with various pore size distributions are prepared and either impregnated with pure C₆₀ or soaked with methanofullerenes or fullerodendrimers derivative solution. Induced absorption or reverse saturable absorption (RSA) has been studied in both types of solid materials. The samples impregnated by pure C₆₀ mainly contain well-dispersed fullerene molecules. Unlike crystalline films of C₆₀, their absorption dynamics can be well described by a 5-level model, developed for non-interacting C₆₀-molecules in solutions. Methanofullerene samples, on the other hand, show signs of micellar aggregation and therefore RSA dynamics, which are influenced by solid state effects. Fullerodendrimers derivatives lead to the highest quantum yield.     

有机-无机杂化骨修复材料

寻找理想的骨修复材料一直是骨科领域的研究热点之一。骨修复材料已由最初单纯取代天然骨组织的惰性材料向具有诱导骨组织再生功能的生物活性材料发展,其中有机-无机杂化材料由于有机和无机组分在分子/纳米水平的复合使其能够最大程度地实现二者的优势互补和协同优化,近年来受到广泛关注。本文着重介绍了有机-无机杂化骨修复材料近些年来的研究进展,并对其发展趋势进行了展望。     

Linear and Nonlinear Optical Properties of C60 Derivative Sol-Gels

Optical limiting properties of a sol-gel, functionalized with C₆₀ derivative molecule were studied by the nonlinear transmission technique in 480–650 nm wavelength range with nanosecond pulsed laser. The solid plates, with functionalized derivative C₆₀ concentration equal to 0.004 ML^–1, show interesting limiting behavior with threshold around 0.01 J/cm². The damage threshold ranges between 0.1 and 10 J/cm² depending upon the sample optical quality. The nonlinear optical properties of sol-gels were determined also by the optical third harmonic generation. At 1907 nm the cubic ⁽³⁾ (–3 ; , , ) susceptibility is of 1.3(± 0.1) × 10^–14 esu.     

Influence of the Matrix in the Optical Response of Organic-Inorganic Hybrid Materials Doped with Europium(III)

Eu³⁺-doped siloxane-oxide hybrid nanocomposites have been prepared by hydrolysis and condensation of diethoxydimethylsilane (DEDMS) and different metallic alkoxides, M(OR) _n with M = Ti, Zr, Al and Ta. The luminescent properties of Eu³⁺ have been used to study the environment of the rare earth ion within the matrices. Emission spectra shows that the surrounding of the Eu³⁺ varies with the matrix composition and depends on the nature of the metal introduced as cross-linking agent. In addition, decay curves have been performed and they show different lifetime values for each system. Among the systems under investigation, the one with tantalum presents the most anisotropic surrounding and the lowest coordination number for the rare earth ion, and the one with aluminium, which shows the most symmetrical surrounding, presents a small lifetime value, probably due to the tendency of Al³⁺cation to attract and retain hydroxyl groups, responsible for luminescence quenching.     

锰钒氧无机-有机杂化材料

氧化锰、钒氧簇构筑块经与有机组分组合可形成新型结构的锰钒氧无机-有机杂化材料。人们预测锰钒氧无机-有机杂化材料将兼有金属锰配合物和钒氧无机-有机杂化材料结构的多样性、独特的物理性质和广阔的应用前景。本文综述了近年来锰钒氧无机-有机杂化材料的合成、组成、结构及有关性质的研究与进展。     

Sol-Gel Synthesis of Hybrid Organic-Inorganic Monoliths Doped with Colloidal CdSe/ZnS Core-Shell Nanocrystals

Colloidal CdSe/ZnS core-shell nanocrystals, with a narrow size distribution, were dispersed in a hybrid sol resulting from the hydrolysis of tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane (GLYMO). In order to reduce the gelation time and the exposure of the nanoparticles to air, several catalysts of the GLYMO epoxy ring opening were employed for the sol preparation, such as imidazole, methyl-imidazole, pyridine, benzylamine, propylamine. The role of the various catalysts was monitored by optical absorption measurements in the near infrared region, by observing the evolution of the epoxy bands. Imidazole was found to provide the fastest gelation and the best results in terms of bubble disappearance from the gel structure. The variation in the optical properties of the semiconductor nanoparticles embedded in the matrix was monitored as a function of the gelation time and was compared to the optical absorption and photoluminescence spectra of the nanoparticles dissolved in a chloroform solution. A decrease in the gelation-time results in a closer resemblance between the optical properties of the CdSe/ZnS doped monoliths and those of the particles dissolved in the solvent, before incorporation in the matrix. The photoluminescence of the CdSe/ZnS nanocrystals is not bleached after they are trapped in the glassy matrix.     

Optical Nonlinearity of Hybrid and Nanocomposite Materials Prepared by the Sol-Gel Method

In this paper the nonlinear refractive index, optical limiting effect, photoinduced and electroinduced second harmonic generation of dye-doped hybrid and nanoparticle-doped composite materials prepared by the sol-gel process have been reported. The origin of these nonlinear optical effects has been discussed.     

Sol-Gel技术制备二阶有机/无机复合非线性光学材料的研究进展

溶胶－凝胶技术是制备材料的一种新兴低温工艺，它为两种完全不相容的成份—聚合物材料和无机玻璃的大比例混合（或键合）创造了可能，使得制备出的材料兼备两种成份的优点。本文综述了近年来溶胶－凝胶技术在制备有机／无机复合非线性光学材料领域中的应用，并简要分析了当前研究工作所面临的问题。     

有机噻吩类衍生物作为电致变色材料*

噻吩类衍生物包括聚噻吩衍生物和齐聚噻吩衍生物。本文从有目的地设计、合成噻吩类衍生物的角度出发,探索了其作为电致变色材料的应用,综述了噻吩类衍生物作为电致变色材料的最新研究进展。     

Advances in Photonic Devices Based on Optical Phase-Change Materials

Phase-change materials (PCMs) are important photonic materials that have the advantages of a rapid and reversible phase change, a great difference in the optical properties between the crystalline and amorphous states, scalability, and nonvolatility. With the constant development in the PCM platform and integration of multiple material platforms, more and more reconfigurable photonic devices and their dynamic regulation have been theoretically proposed and experimentally demonstrated, showing the great potential of PCMs in integrated photonic chips. Here, we review the recent developments in PCMs and discuss their potential for photonic devices. A universal overview of the mechanism of the phase transition and models of PCMs is presented. PCMs have injected new life into on-chip photonic integrated circuits, which generally contain an optical switch, an optical logical gate, and an optical modulator. Photonic neural networks based on PCMs are another interesting application of PCMs. Finally, the future development prospects and problems that need to be solved are discussed. PCMs are likely to have wide applications in future intelligent photonic systems.     

Hybrid Organic-Inorganic Materials by Nonhydrolytic Sol-Gel Processes: Organosilsesquioxane-Metal Oxide Hybrids

Organosilsesquioxane-metal oxide hybrid materials prepared by the Sol-Gel process are mainly heterogeneous. In this paper we report the preparation of methylsilsesquioxane-titanium oxide, and methylsilsesquioxane-aluminium oxide hybrid materials by a nonhydrolytic sol-gel process involving the etherolysis-condensation of a mixture of methyltrichlorosilane and metal chloride. The Si/M ration in the xerogels were very closed to the one of the starting solutions. ²⁹Si MAS NMR study has revealed that the methylsilsesquioxane-titanium oxide xerogel was heterogeneous at the atomic level. The spectrum of the hybrid containing aluminium, has shown beside a peak at –66 ppm corresponding to MeSi(OSi)₃ environment, another peak at –47 ppm which was ascribed to MeSi(OAl)₃ environment. The presence of only these two sites might be due to their stability.     

Metal Complexes of Phthalocyanines in Polymers as Suitable Materials for Optical Limiting

Summary: Germanium and tin phthalocyanines containing peripheral and axial different substituents were synthesized. Thin multi-layer films of PMMA and PVC containing monomolecular phthalocyanines were obtained by spin-coating on glass substrates. The phthalocyanines were characterized by their absorption spectra. Optical limiting properties of the phthalocyanines in solution and in polymer films were investigated.