Hybrid materials for optics and photonics

The interest in organic-inorganic hybrids as materials for optics and photonics started more than 25 years ago and since then has known a continuous and strong growth. The high versatility of sol-gel processing offers a wide range of possibilities to design tailor-made materials in terms of structure, texture, functionality, properties and shape modelling. From the first hybrid material with optical functional properties that has been obtained by incorporation of an organic dye in a silica matrix, the research in the field has quickly evolved towards more sophisticated systems, such as multifunctional and/or multicomponent materials, nanoscale and self-assembled hybrids and devices for integrated optics. In the present critical review, we have focused our attention on three main research areas: passive and active optical hybrid sol-gel materials, and integrated optics. This is far from exhaustive but enough to give an overview of the huge potential of these materials in photonics and optics (254 references).     

Photochromic organic-inorganic hybrid materials

Photochromic organic-inorganic hybrid materials have attracted considerable attention owing to their potential application in photoactive devices, such as optical memories, windows, photochromic decorations, optical switches, filters or non-linear optics materials. The growing interest in this field has largely expanded the use of photochromic materials for the purpose of improving existing materials and exploring new photochromic hybrid systems. This tutorial review summarizes the design and preparation of photochromic hybrid materials, and particularly those based on the incorporation of organic molecules in organic-inorganic matrices by the sol-gel method. This is the most commonly used method for the preparation of these materials as it allows vitreous hybrid materials to be obtained at low temperatures, and controls the interaction between the organic molecule and its embedding matrix, and hence allows tailoring of the performance of the resulting devices.     

Organic-inorganic hybrids assembled by bis(undecatungstophosphate) lanthanates and dinuclear copper(II)-oxalate complexes

A series of organic-inorganic hybrid compounds, K2H7[{Ln(PW11O39)2}{Cu2(bpy)2(mu-ox)}].xH2O (Ln = La, x approximately = 18 (1); Ln = Pr, x approximately = 18(2); Ln = Eu, x approximately = 16(3); Ln = Gd, x approximately 22(4); Ln = Yb, x approximately = 19 (5); bpy = 2,2'-bipyridine and ox = oxalate), have been isolated by the conventional solution method. Single-crystal X-ray diffraction studies reveal that compounds 1-5 are isomorphic and consist of one-dimensional chains, which are constructed by alternating bis(undecatungstophosphate) lanthanates [Ln(PW11O39)2](11-) and dinuclear copper(II)-oxalate complexes [Cu2(bpy)2(mu-ox)]2+.pi-pi interactions of the bpy ligands from adjacent chains lead to their three-dimensional structures. An analogue of potassium K2H9[{K(PW11O39)2}{Cu2(bpy)2(mu-ox)}1].approximately 20.5H2O(6) has also been obtained. The syntheses and structures of these compounds are reported here. Magnetic properties of 1, 2 and 3 are discussed as well. Attempts to crystallize similar compounds containing Co(II) and Ni(II) were unsuccessful.     

Spectroscopic study of a UV-photostable organic-inorganic hybrids incorporating an Eu3+ beta-diketonate complex.

New europium and gadolinium tris-beta-diketonate complexes have been prepared and incorporated in sol-gel-derived organic-inorganic hybrids, named di-ureasils. The general formula [Ln(btfa)3(4,4'-bpy)(EtOH)] (Ln=Eu, Gd; 4,4'-bpy=4,4'-bipyridine; btfa=4,4,4-trifluoro-1-phenyl-1,3-butanedione) for the complexes was confirmed by X-ray crystallography and elemental analysis. The ground-state geometry of the Eu3+ complex was calculated from the Sparkle/AM1 model. The calculated quantum yield obtained from the Sparkle model and from the crystal structure (both 46%) are in satisfactory agreement with the experimental value (38+/-4%). In the isolated complex the most efficient luminescence channel is S0-->S1-->T-->(5D1, 5D0)-->7F0-6, where the exchange mechanism dominates in the energy-transfer channel T-->(5D1, 5D0). For the Eu3+-based di-ureasils a 50% quantum yield enhancement compared to the Eu3+ complex is observed, which suggests an effective hybrid host-metal ion interaction and an active energy-transfer channel between the hybrid host and the Eu3+ complex. The Eu3+-based di-ureasils are photostable under UVA (360 nm) excitation, whereas under UVB (320 nm) and UVC (290 nm) photodegradation occurs.     

Organic-inorganic hybrid mesoporous silicas: functionalization, pore size, and morphology control

Topological design of mesoporous silica materials, pore architecture, pore size, and morphology are currently major issues in areas such as catalytic conversion of bulky molecules, adsorption, host-guest chemistry, etc. In this sense, we discuss the pore size-controlled mesostructure, framework functionalization, and morphology control of organic-inorganic hybrid mesoporous silicas by which we can improve the applicability of mesoporous materials. First, we explain that the sizes of hexagonal- and cubic-type pores in organic-inorganic hybrid mesoporous silicas are well controlled from 24.3 to 98.0 A by the direct micelle-control method using an organosilica precursor and surfactants with different alkyl chain lengths or triblock copolymers as templates and swelling agents incorporated in the formed micelles. Second, we describe that organic-inorganic hybrid mesoporous materials with various functional groups form various external morphologies such as rod, cauliflower, film, rope, spheroid, monolith, and fiber shapes. Third, we discuss that transition metals (Ti and Ru) and rare-earth ions (Eu(3+) and Tb(3+)) are used to modify organic-inorganic hybrid mesoporous silica materials. Such hybrid mesoporous silica materials are expected to be applied as excellent catalysts for organic reactions, photocatalysis, optical devices, etc.     

含Fe(Ⅲ)离子有机-无机层状类钙钛矿杂合物修饰电极对对苯二酚的电催化作用及测定

以酚藏花红为有机层、含三价铁的K3Fe(CN)6为无机层在空气中合成了有机-无机层状类钙钛矿杂合物修饰碳糊电极。利用扫描电镜(SEM)和X-射线衍射(XRD)对其表面形貌和微观结构进行表征,并用循环伏安法研究了杂合物修饰电极的电化学性质,发现该电极对对苯二酚具有良好的电催化作用。结果表明,在pH5.0的PBS缓冲溶液中,对苯二酚在空白碳糊电极上为二步还原过程而在修饰电极上只有一步还原过程,修饰电极更有利于检测对苯二酚。采用微分脉冲伏安法在-0.4～0V电位范围内进行扫描,在-240.2mV处的还原峰电流与对苯二酚浓度在1.0×10-6～1.0×10-3mol/L范围呈良好的线性关系,相关系数为0.9951,检出限为4.73×10-7mol/L。对1.0×10-5mol/L的对苯二酚连续测定5次,相对标准偏差为1.8%。模拟样品中对苯二酚的平均加标回收率为102%。     

一种基于碘化铅的有机/无机杂化钙钛矿材料传输性能的研究

合成了一种新型的有机/无机杂化钙钛矿(NH3C6H4OC6H4NH3)PbI4, 采用元素分析、紫外-可见光吸收光谱、X射线衍射和透射电镜对其结构进行了表征, 结果表明这种材料具有规则的层状结构, 有序性高. 对这种材料的薄膜进行了伏安测试, 结果表明该材料属于n型半导体, 其电子迁移率达到0.065 cm2•V－1•s－1, 在光电器件领域有着潜在的应用前景.     

Lanthanide (Eu3+, Tb3+) Centered Mesoporous Hybrids with 1,3‐Diphenyl‐1,3‐Propanepione Covalently Linking SBA‐15 (SBA‐16) and Poly(methylacrylic acid)

1,3‐Diphenyl‐1,3‐propanepione (DBM)‐functionalized SBA‐15 and SBA‐16 mesoporous hybrid materials (DBM‐SBA‐15 and DBM‐SBA‐16) are synthesized by co‐condensation of modified 1,3‐diphenyl‐1,3‐propanepione (DBM‐Si) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 and Pluronic F127 as a template, respectively. The as‐synthesized mesoporous hybrid material DBM‐SBA‐15 and DBM‐SBA‐16 are used as the first precursor, and the second precursor poly(methylacrylic acid) (PMAA) is synthesized through the addition polymerization reaction of the monomer methacrylic acid. These precursors then coordinate to lanthanide ions simultaneously, and the final mesoporous polymeric hybrid materials Ln(DBM‐SBA‐15)₃PMAA and Ln(DBM‐SBA‐16)₃PMAA (Ln=Eu, Tb) are obtained by a sol‐gel process. For comparison, binary lanthanide SBA‐15 and SBA‐16 mesoporous hybrid materials (denoted as Ln(DBM‐SBA‐15)₃ and Ln(DBM‐SBA‐16)₃) are also synthesized. The luminescence properties of these resulting materials are characterized in detail, and the results reveal that ternary lanthanide mesoporous polymeric hybrid materials present stronger luminescence intensities, longer lifetimes, and higher luminescence quantum efficiencies than the binary lanthanide mesoporous hybrid materials. This indicates that the introduction of the organic polymer chain is a benefit for the luminescence properties of the overall hybrid system. In addition, the SBA‐15 mesoporous hybrids show an overall increase in luminescence lifetime and quantum efficiency compared with SBA‐16 mesoporous hybrids, indicating that SBA‐15 is a better host material for the lanthanide complex than mesoporous silica SBA‐16.     

Uniform hollow Lu2O3:Ln (Ln = Eu3+, Tb3+) spheres: facile synthesis and luminescent properties

Uniform hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) phosphors have been successfully prepared via a urea-assisted homogeneous precipitation method using carbon spheres as templates, followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, kinetic decays, quantum yields (QY), and UV-visible diffuse reflectance spectra were employed to characterize the samples. The results show that hollow Lu(2)O(3):Ln spheres can be indexed to cubic Gd(2)O(3) phase with high purity. The as-prepared hollow Lu(2)O(3):Ln phosphors are confirmed to be uniform in shape and size with diameter of about 300 nm and shell thickness of approximate 20 nm. The possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow Lu(2)O(3):Ln microspheres has been proposed. Upon ultraviolet (UV) and low-voltage electron beams excitation, the hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) spheres exhibit bright red (Eu(3+), (5)D(0)-(7)F(2)) and green (Tb(3+), (5)D(4)-(7)F(5)) luminescence, which may find potential applications in the fields of color display and biomedicine.     

Photoactive organic-inorganic hybrid materials: From silylated compounds to optical applications

This review summarizes several aspects of type II photoactive organic-inorganic hybrid materials prepared from silylated fluorophores, including their photophysical properties and uses. In this sense, several examples are presented and discussed taking the nature of the silyl derivative into account. Applications as latent fingerprints detection, chemosensors for metal cations, anions, pH, heavy metals, and small organic molecules, as well as recent use as drug delivery systems, bioimaging, organic solar cells, aerogels, and highly fluorescent hybrid materials, are reported and compared to the literature. Also, fluorescent type II organic-inorganic hybrid materials from non-silylated fluorophores, prepared with binding agents, such as 3-(triethoxysilyl)propyl isocyanate (TESPIC), 3-mercaptopropyltriethoxysilane (TMMPS), or 3-isocyanato propyltrimethoxysilane (ICPTES) are also covered in this review.     

Sol–Gel Derived Organic and Inorganic Hybrid Materials for Photonic Applications: Contribution to the Correlation Between the Material Structure and the Transmission in the Near Infrared Region

A promising way of fabricating integrated optics components is based on the sol–gel synthesis and photocuring of organic-inorganic hybrid materials. However, the main factor limiting the development of passive devices is the propagation losses. Moreover, the possibility to compensate these attenuations by optical amplification is competed with the multiphonon relaxation associated to the presence of OH groups. To our knowledge, OH groups were always shown as the main responsible for attenuation at the telecommunication wavelengths, namely at 1310 and 1550 nm, although the matrix is composed of organic species which can contribute to absorptions in this spectral range. This paper deals with spectroscopic and optical characterizations of a well established organic and inorganic hybrid material in order to determine the contribution of each molecular groups to the attenuation at the aforementioned wavelengths.     

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.     

Design and properties of functional hybrid organic-inorganic membranes for fuel cells

This critical review presents a discussion on the major advances in the field of organic-inorganic hybrid membranes for fuel cells application. The hybrid organic-inorganic approach, when the organic part is not conductive, reproduces to some extent the behavior of Nafion where discrete hydrophilic and hydrophilic domains are homogeneously distributed. A large variety of proton conducting or non conducting polymers can be combined with various functionalized, inorganic mesostructured particles or an inorganic network in order to achieve high proton conductivity, and good mechanical and chemical properties. The tuning of the interface between these two components and the control over chemical and processing conditions are the key parameters in fabricating these hybrid organic-inorganic membranes with a high degree of reproducibility. This dynamic coupling between chemistry and processing requires the extensive use and development of complementary ex situ measurements with in situ characterization techniques, following in real time the molecular precursor solutions to the formation of the final hybrid organic-inorganic membranes. These membranes combine the intrinsic physical and chemical properties of both the inorganic and organic components. The development of the sol-gel chemistry allows a fine tuning of the inorganic network, which exhibits acid-based functionalized pores (-SO(3)H, -PO(3)H(2), -COOH), tunable pore size and connectivity, high surface area and accessibility. As such, these hybrid membranes containing inorganic materials are a promising family for controlling conductivity, mechanical and chemical properties (349 references).     

Lanthanide-centered organic-inorganic hybrids through a functionalized aza-crown ether bridge: coordination bonding assembly, microstructure and multicolor luminescence

This work focuses on the synthesis of a series of chemically bonded lanthanide/inorganic/organic hybrid materials (CE-15-Si-Ln, CE-16-Si-Ln, CE-18-Si-Ln) containing a novel aza-crown ether organic component. The materials show red emission (Ln = Eu), green emission (Ln = Tb) and near-infrared (NIR) luminescence (Ln = Nd). Three functional molecular precursors (denoted as CE-15-Si, CE-16-Si, CE-18-Si) have been synthesized with two or three N-substituted pendant arms containing chelating groups which can not only fulfill the high coordination numbers of Ln(3+) ions but also form an inorganic Si-O-Si network with tetraethoxysilane (TEOS). The resulting amorphous materials exhibit regular uniform microstructures for the organic and the inorganic components which are covalently linked through Si-O bonds via a self-assembly process. These hybrids present strong luminescent intensities in red, green and NIR ranges by embedding selected Ln(3+) ions into the hybrid system, which may lead to potential applications in organic electroluminescence displays, light emitting devices, functional membranes or chemical/biomedical sensors.     

有机-无机杂化膜的研究进展

有机-无机杂化膜结合了传统有机膜与无机膜的优良性能,已成为膜领域的研究热点之一。本文综述了有机-无机杂化膜的研究现状,归纳了有机-无机杂化膜的分类、制备技术、应用及其优越性,并针对现存的问题及今后的研究发展提出了一些建议。     

Partial Hydrolysis of Diphosphonate Ester During the Formation of Hybrid TiO2 Nanoparticles: Role of Acid Concentration

The hydrolysis of the phosphonate ester linker during the synthesis of hybrid (organic-inorganic) TiO₂ nanoparticles is important when forming porous hybrid organic-inorganic metal phosphonates. In the present work, a method was utilized to control the in-situ partial hydrolysis of diphosphonate ester in the presence of a titania precursor as a function of acid content, and its impact on the hybrid nanoparticles was assessed. Organodiphosphonate esters, and more specific, their hydrolysis degree during the formation of hybrid organic-inorganic metal oxide nanoparticles, are relatively under explored as linkers. Here, a detailed analysis on the hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) as diphosphonate linker to produce hybrid TiO₂ nanoparticles is discussed as a function of acid content. Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO₂ nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4 % to 18.8 % under the applied conditions. As a result of the difference in partial hydrolysis, the linker-TiO₂ bonding was altered. Upon subsequent drying of the colloidal TiO₂ solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker-TiO₂ nanoparticle surface dynamics is crucial for making hybrid organic-inorganic materials (i. e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysis.     

Research progress on hybrid organic-inorganic perovskites for photo-applications

Hybrid organic-inorganic perovskite materials have attracted significant attention of most researchers in recently years, which is ascribed to the superior photoelectric properties, such as the suitable band gaps for harvesting sunlight, and exhibit high optical adsorption, high charge-carrier lifetimes and long diffusion lengths. The photodetectors, light-emitting diodes, solar cells and photocatalysts represent the remarkable applications for the hybrid organic-inorganic perovskite materials. Herein, we review the recent progress of hybrid organic-inorganic perovskite-based photodetectors, light-emitting diodes, solar cells and photocatalysts. The challenges and outlook for the hybrid organic-inorganic perovskite-based photodetectors, light-emitting diodes, solar cells and photocatalysts are considered.     

Near-infrared luminescent hybrid materials doped with lanthanide (Ln) complexes (Ln = Nd, Yb) and their possible laser application

The crystal structures of ternary Ln(DBM)(3)phen complexes (DBM = dibenzoylmethane, phen = 1,10-phenanthroline, and Ln = Nd, Yb) and their in situ syntheses via the sol-gel process are reported. The properties of the Ln(DBM)(3)phen complexes and their corresponding Ln(3+)/DBM/phen-co-doped luminescent hybrid gels obtained via an in situ method (Ln-D-P gel) have been studied. The results reveal that the lanthanide complexes are successfully in situ synthesized in the corresponding Ln-D-P gels. Both Ln(DBM)(3)phen complexes and Ln-D-P gels display sensitized near-infrared (NIR) luminescence upon excitation at the maximum absorption of the ligands, which contributes to the efficient energy transfer from the ligands to the Ln(3+) ions (Ln = Nd, Yb), an antenna effect. The radiative properties of the Nd(3+) ion in a Nd-D-P gel are discussed using Judd-Ofelt analysis, which indicates that the (4)F(3/2) --> (4)I(11/2) transition of the Nd(3+) ion in the Nd-D-P gel can be considered as a possible laser transition.     

Chitosan bio-based organic-inorganic hybrid aerogel microspheres

Recently, organic-inorganic hybrid materials have attracted tremendous attention thanks to their outstanding properties, their efficiency, versatility and their promising applications in a broad range of areas at the interface of chemistry and biology. This article deals with a new family of surface-reactive organic-inorganic hybrid materials built from chitosan microspheres. The gelation of chitosan (a renewable amino carbohydrate obtained by deacetylation of chitin) by pH inversion affords highly dispersed fibrillar networks shaped as self-standing microspheres. Nanocasting of sol-gel processable monomeric alkoxides inside these natural hydrocolloids and their subsequent CO(2) supercritical drying provide high-surface-area organic-inorganic hybrid materials. Examples including chitosan-SiO(2), chitosan-TiO(2), chitosan-redox-clusters and chitosan-clay-aerogel microspheres are described and discussed on the basis of their textural and structural properties, thermal and chemical stability and their performance in catalysis and adsorption.