Hybrid organic–inorganic nanocomposite materials for application in solid state electrochemical supercapacitors

Integration into a conducting polymer matrix to form a hybrid material is an effective way to harness the electrochemical activity of nanosized oxide clusters. By anchoring them into polyaniline, the reversible redox chemistry of the otherwise soluble polyoxometalate clusters can be combined with that of the conducting polymer and be put to work in energy storage applications. We present here preliminary results that show how the resulting hybrid polymer displays the combined activity of its organic and inorganic components to store and release charge in a solid state electrochemical capacitor device.     

Flexible inorganic–organic hybrids with dual inorganic components

Combining multiple inorganic components is an effective approach to improve the mechanical properties of inorganic–organic hybrid materials. The inorganic components can form interactions with the organic polymer matrix, and there is thus a need to understand the reinforcement mechanism under the optimal combination of organic polymer and inorganic particles. In this work, we prepared a series of dual inorganic particle–based titania/silica–poly(tetrahydrofuran)–poly(ε-caprolactone) (TiO₂/SiO₂–PTHF–PCL) hybrids by means of simultaneous cationic ring-opening polymerization and sol–gel reaction. In addition to constructing hybrid networks, the SiO₂ and TiO₂ components play important roles in multiple toughening mechanisms. The prepared dual inorganic hybrids feature enhanced thermal stability and mechanical properties when compared with the ones with a single inorganic component. The optimized mixing of such two inorganic components is identified through mechanical tests, revealing that the hybrid polymer₇₀/(Si_0.6Ti_0.4)₃₀ (70/18/12 mass ratio) has the highest compressive failure strain (80%) and compressive ultimate strength (1.3 MPa) as well as storage modulus (120 kPa), enabling elongation of up to 37% when compared with its original length. We thus find that the dual inorganic component approach is an effective strategy to enhance the mechanical properties of hybrid materials, suggesting potential applications as scaffolds for tissue engineering and soft robotics.     

Hybrid organic–inorganic sol–gel coatings with interpenetrating network for corrosion protection of tinplate

Novel hybrid organic–inorganic coatings with interpenetrating network were synthesized by the acid-catalyzed hydrolytic co-polycondensation of tetraethoxysilane and 3-metacryloxypropyltrimethoxysilane, followed by radical polymerization with methyl methacrylate and triallyl isocyanurate (TAIC). The hybrid coatings were characterized by Fourier transformed infrared spectroscopy, thermogravimetric analysis and scanning electron microscope, and their anti-corrosion behaviors were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy and salt spray test. The results indicated that the hybrid coatings exhibited excellent anti-corrosion ability by forming a physical barrier between metal and its external environment. Thermal stability of the hybrid coatings was increased after the addition of TAIC. Furthermore, hydrophobic properties of the hybrid coatings were examined by measuring the contact angles, and the change in wetting characteristics of the hybrid coatings was not obvious.     

Hybrid organic–inorganic materials: from child’s play to energy applications

The field of hybrids has boomed since its initial conception with silicones as structural materials to the wealth of different types of hybrid materials studied nowadays as functional materials. Hybrids based on conducting polymers and a great variety of inorganic species constitute a growing area of this field. We present a brief review of the intersection between conducting polymer hybrids and electrochemical applications to energy storage and conversion. But beyond examples of hybrids active in batteries, supercapacitors, solar or fuel cells, we have tried to convey the standing challenges concerning the design of chemically (and electrochemically) complex hybrid systems with components and building blocks ranging from extended oxides or nanoparticles to carbon or oxide nanotubes, to clusters and to molecules and the opportunities arising from their integration with conducting polymers.     

Bacterial cellulose–silica organic–inorganic hybrids

Bacterial cellulose (BC) hydrated membranes present nanometric reticulated structure that can be used as a template in the preparation of new organic–inorganic hybrids. BC–silica hybrids were prepared from BC membranes and tetraethoxysilane, (TEOS) at neutral pH conditions at room temperature. Macroscopically homogeneous membranes were obtained containing up to 66 wt.% of silica spheres, 20–30 nm diameter. Scanning electron micrographs clearly show the silica spheres attached to cellulose microfibrils. By removing the cellulose, the silica spheres can be easily recovered. The new hybrids are stable up to 300 °C and display a broad emission band under UV excitation assigned to oxygen-related defects at the silica particles surface. Emission color can be tuned by changing the excitation wavelength.     

Functionalization of mesostructured inorganic–organic and porous inorganic materials

The capability to functionalize the interior channels and/or high internal surface areas of mesostructured inorganic–organic or porous inorganic solids with specific organic or inorganic moieties has dramatically expanded the potential applications for these versatile materials in catalysis, separations, optical and opto-electronic devices, drug delivery, sensors, and energy conversion. Key to the widespread application of these materials are the various synthetic schemes that have been developed to provide control over the types of species incorporated and, more importantly, their distributions within the mesostructured hosts. Furthermore, multiple active species can often be independently incorporated and collectively optimized to yield multifunctional properties that widen application prospects. Several recent developments and examples in this rapidly growing field of materials chemistry and engineering are highlighted and discussed.     

Self-assembly of functionalized inorganic–organic hybrids

Recent advances on the synthesis and self-assembly of hybrid inorganic–organic materials have been reviewed in terms of the synthetic strategies and emerging techniques, including in-situ self-assembly, template-induced self-assembly, evaporation-induced self-assembly, and layer-by-layer assembly for assembling functional hybrids. The perspectives and outlook on this research topic are given.     

Responsive microstructures on organic–inorganic hybrid films

Micro-periodic structures exhibiting shape memory have been fabricated on organic–inorganic hybrid films. The microscale structures are obtained by forming wrinkles via buckling of the stiff surface layer. The surface-modified layers are obtained by surface photopolymerization or by oxidation of the hybrid films. The microscale structures are spontaneously formed by the shrinkage of the underlayer via gelation. The surface microstructures on titania- or silica-based films with hydrophilic swellable polymers exhibit a humidity response, i.e., a shape memory effect. This is observed when the surface microstructure disappears and is subsequently recovered with cyclic variation of the surrounding humidity. Micro-rolls are also fabricated by the selective swelling of surface-modified layers.     

Elastic organic–inorganic hybrid aerogels and xerogels

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH₃SiO_1.5) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a “spring-back” behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.     

Multi-component hybrid inorganic–organic–inorganic particles with various metal oxide outer shells

Non-agglomerated hybrid particles of 200 nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)₄), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides.     

Sedimentation analysis of organic–inorganic hybrid colloids

Hybrid organic–inorganic latex particles are synthesized to combine the beneficial properties of the constituents which thus lead to synergistic improvement in the properties. The properties of hybrid particles are dependent on the successful hybridization process, thus controlling or tuning of such processes by effective characterization is immensely important. Analytical ultracentrifugation provides these characterization possibilities owing to its high statistical capability and ability to characterize multiple parameters. The use of different detection methodologies can help in generating valuable information on the overall size and density distributions of the particles. Apart from that, it is also possible to quantify the presence of any free polymer and inorganic particles in the hybrid latex which would affect the properties of hybrid latexes. By following the densities of the pure and hybrid particles, it is also possible to quantify the amounts of the constituent phases in the hybrid particles. The density gradients generated in preparative ultracentrifugation also provide additional possibilities for the characterization of the hybrid particles which have densities higher than the measurable range in the analytical ultracentrifuge. Evolution of hybrid particles can also be studied as a function of time. It also provides advantage of separation of the various fractions for further characterization.     

Sol–gel derived organic–inorganic composites recognizing molecular asymmetry

A new type of optically active organic-inorganic composite was prepared by a sol–gel method in which tetraethoxysilane (TEOS) is hydrolyzed in the presence of an optically active organic compound (d-lactose, d-glucose, d-sorbitol, d-fructose, l-tartaric acid, l-malic acid, or l-mandelic acid). Optical resolution of tris(pentane-2,4-dionato)metal complexes was performed by using the new sol–gel derived composites, composites prepared by conventional techniques (kneading with l-lactose, l-fructose or l-tartaric acid, and impregnation with an l-lactose, l-fructose or l-tartaric acid solution) and the optically active organic compounds themselves. The sol–gel derived composites showed much higher optical resolution abilities than the composites prepared by conventional techniques. In addition, the optically active organic compounds could not resolve the racemate into the enantiomers under similar conditions. X-ray diffraction and NMR results disclosed that an optically active organic compound in the sol–gel derived composite is highly dispersed, most likely, because it bonds to silicon atoms. Thus, it was deduced that optically active molecules dispersed at a molecular level recognize the chirality of the metal chelate compound. The high-resolution ability of the sol–gel derived composites arises from the combined effect of the silica support (adsorbing power) and the highly dispersed molecules (chiral recognition power).     

Hybrid inorganic–organic layered structures of [AuCl4] and protonated bipyridyl derivatives

Complexes of [AuCl₄]⁻ with 4,4′-dipyridylethane, 4,4′-dipyridylethene and 4,4′-bipyridine-N,N′-dioxide have been prepared by a solvent layering method. All three complexes pack in distinct organic and inorganic layers: [H₂-dpa][AuCl₄]Cl (1) and [H₂-dpe][AuCl₄]Cl (2) are isostructural and consist of layers of [AuCl₄]⁻ anions alternating with hydrogen-bonded dipyridyl?Cl?dipyridyl layers. In [H-bpdo][AuCl₄] (3), the organic layers consist instead of hydrogen-bonded bipyridyldioxide cations. This structure is the first report of a structure containing protonated 4,4′-bipyridine-1,1′-dioxide.     

Two extended organic–inorganic hybrids based on sandwich tungstogermanates

Two inorganic–organic composite polyoxotungstates, [Cu(en)₂(H₂O)]₂[Cu(en)₂(H₂O)₂]-{[Cu(en)₂]₃[Cu₄(GeW₉O₃₄)₂]} · 10H₂O (1, en = ethylenediamine) and (H₂en){[Zn(en)₂]₄-[Zn₄(Hen)₂(GeW₉O₃₄)₂]} · 10H₂O (2), were hydrothermally synthesized and their structures determined by single-crystal X-ray diffraction. Compounds 1 and 2 consist of sandwich polyanions [Cu₄(B-α-GeW₉O₃₄)₂]^12? or [Zn₄(Hen)₂(GeW₉O₃₄)₂]^10? linked by [M(en)₂]²⁺ bridges to form 2-D networks, which are further packed into a 3-D supramolecular porous framework via extensive hydrogen bonding interactions. Their IR and UV spectra, thermal stabilities, and cyclic voltammograms were also investigated.     

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.     

New route to 3-methacryloxypropyltrimethoxysilane-base organic–inorganic hybrid film

A series of poly(3-methacryloxypropyltrimethoxysilane)/waterborne polyurethane (PMPS/WPU) composite latexes and organic–inorganic hybrid films with PMPS contents of 0, 10, 20, 30, 40 and 50 wt.% were prepared via seeded emulsion polymerization initiated by AIBN and hydrolysis–condensation process of PMPS during the evaporation of water, respectively. WPU, that is anionic polyurethane emulsion, was synthesized using isophorone diisocyanate, polytetramethylene ether glycol, dimethylol propionic acid, 1,4-butanediol, and triethylamine. An investigation of transmission electron microscopy confirmed the core–shell morphology of the composite latex particle which was composed of a PMPS core and a polyurethane shell. A dynamic light scattering analysis showed that the average particle size distributed in the range of 42–134 nm. The proposed novel preparation method included the use of polyurethane as macromolecular emulsifier and steric stabilizer, control of (3-methacryloxypropyltrimethoxysilane) (MPS) content less than 50 wt.%, slow addition of MPS and application of AIBN ensured the preparation of a stable PMPS/WPU composite latex. Formed PMPS/WPU organic–inorganic hybrid film with high PMPS content via sol-gel process had uniform transparency at visible band because of less crystalline and phase separation between organic and inorganic phases.     

Three organic–inorganic hybrid complexes based on the Wells–Dawson polyoxoanion

Three new organic–inorganic hybrid complexes based on the Wells–Dawson polyoxoanion, namely (H₂bpp)[Ni₂(bpp)₂(H₂O)₄(P₂W₁₈O₆₂)]·H₂O 1, [Cu₆(Hbpy)₆(bpy)₃(P₂W₁₈O₆₂)₂]·2H₂O 2 and (Him)₅[Cu(im)₂(P₂W₁₈O₆₂)]·4H₂O 3 [bpp = 1,3-bis (4-pyridyl) propane, bpy = 4,4′-bipyridine, im = imidazole] have been synthesized and characterized. Complex 1 exhibits a three-dimensional (6, 3)-connected framework with anatase topology constructed from [α-P₂W₁₈O₆₂]⁶⁻ clusters and [Ni(bpp)]²⁺ fragments. Each [α-P₂W₁₈O₆₂]⁶⁻ anion links to six nickel atoms through six terminal oxygen atoms from four polar and two equatorial WO₆ octahedra, which shows a novel coordination mode of a Wells–Dawson cluster with a transition-metal atom. Complex 2 displays an interesting one-dimensional double-chain structure built from [α-P₂W₁₈O₆₂]⁶⁻ clusters and [Cu₂(bpy)(Hbpy)₂]²⁺ fragments. To our knowledge, complex 2 represents the first double-chain organic–inorganic hybrid complex based on a Wells–Dawson-type cluster. Complex 3 possesses a one-dimensional zigzag chain structure constructed from [α-P₂W₁₈O₆₂]⁶⁻ anions and [Cu(im)₂]⁺ units through weak Cu···O interactions.     

A new organic–inorganic hybrid based on Mn–salen and decavanadate

An organic–inorganic hybrid based on Mn-salen and decavanadate, [NH₄]₂[Mn(salen)(H₂O)₂]₄[V₁₀O₂₈]?·?6H₂O (1) (salen?=?N,N′-ethylene-bis(salicylideneiminate)), has been synthesized by the strategy of secondary building units in mixed methanol–water solution and was structurally characterized by single-crystal X-ray diffraction, elemental analyses, IR, and UV-Vis. The [Mn(salen)(H₂O)₂]⁺ cations and water molecules are located in the interspaces among the polyoxoanions [V₁₀O₂₈]^6? forming a POM-based supramolecule. Compound 1 is the first example of metal-Schiff-base polyoxovanadates. The photocatalytic analysis, cyclic voltammetry, and electrocatalytic analysis of 1 have been investigated.