Self‐Assembly of Amphiphilic Nanocrystals

Amphiphilic hybrid materials are formed from polymer‐coated semiconductor nanoparticles that simulate a surfactant‐like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.

     

Spontaneous Stepwise Self‐Assembly of a Polyoxometalate–Organic Hybrid into Catalytically Active One‐Dimensional Anisotropic Structures

An inorganic–organic hybrid surfactant with a hexavanadate cluster as the polar head group was designed and observed to assemble into micelle structures, which further spontaneously coagulate into a 1D anisotropic structure in aqueous solutions. Such a hierarchical self‐assembly process is driven by the cooperation of varied noncovalent interactions, including hydrophobic, electrostatic, and hydrogen‐bonding interactions. The hydrophobic interaction drives the quick formation of the micelle structure; electrostatic interactions involving counterions leads to the further coagulation of the micelles into larger assemblies. This process is similar to the crystallization process, but the specific counterions and the directional hydrogen bonding lead to the 1D growth of the final assemblies. Since most of the hexavanadates are exposed to the surface, the 1D assembly with nanoscale thickness is a highly efficient heterogeneous catalyst for the oxidation of organic sulfides with appreciable recyclability.     

Morphology‐Controlled Self‐Assembly of an Organic/Inorganic Hybrid Porphyrin Derivative Containing Polyhedral Oligomeric Silsesquioxane (POSS)

An organic/inorganic hybrid porphyrin derivative, namely, metal‐free tetrakisphenyl porphyrin–polyhedral oligomeric silsesquioxanes (H₂TPP‐POSS) was synthesized by azide–alkyne click chemistry. The self‐assembly behavior of H₂TPP‐POSS was systematically studied in CHCl₃ at different concentrations and in solvents with different polarities. Novel nanovesicles could be obtained through the self‐assembly of H₂TPP‐POSS in CHCl₃ at a concentration lower than 10^?4 m. Diffuse microrods formed at a concentration higher than 10^?4 M . Additionally, the polarity of the solvent also greatly influenced the assembled morphologies, and a series of assembled morphologies, including crescent‐shaped micelles, spherical micelles, doughnut‐shaped vesicles, and ordered square sheets, could form in solvents with different polarities.     

Reverse‐Vesicle Formation of Organic–Inorganic Polyoxometalate‐Containing Hybrid Surfactants with Tunable Sizes

The formation of reverse‐vesicular structures of the polyoxometalate‐containing hybrid surfactants [nBu₄N]₃[MnMo₆O₁₈{(OCH₂)₃? CNHCO(CH₂)_n?2CH₃}₂] (Mn‐Anderson‐C_n, n=6, 16) in nonpolar medium was achieved by titrating toluene into Mn‐Anderson‐C_n/acetonitrile (MeCN) solution. Stepwise change of the solvent polarity induces self‐association of the hydrophilic Mn‐Anderson cluster on the hybrid amphiphiles. The reverse‐vesicle formation was characterized by laser light scattering and further confirmed by transmission electron microscopy techniques, and the vesicle sizes increase with increasing toluene contents. The assembly process was accelerated at an elevated temperature. The length of the alkyl tails on the hybrid surfactants has a minor effect on the vesicle sizes, because the strong attraction between the polyoxometalate clusters is more dominant in the reverse‐vesicle formation.     

Two Organic–Inorganic Hybrid 3D {P5W30}‐Based Heteropolyoxotungstates with Transition‐Metal/Ln–Carboxylate–Ln Connectors

Two unique organic–inorganic hybrid polyoxometalates constructed from Preyssler‐type [Na(H₂O)P₅W₃₀O₁₁₀]^14? ({P₅W₃₀}) subunits and TM/Ln–carboxylate–Ln connectors (TM=transition metal, Ln=lanthanide), KNa₇[{Sm₆Mn(μ‐H₂O)₂(OCH₂COO)₇(H₂O)₁₈}{Na(H₂O)P₅W₃₀O₁₁₀}] ? 22 H₂O ( 1 ) and K₄[{Sm₄Cu₂(gly)₂(ox)(H₂O)₂₄}{NaP₅W₃₀O₁₁₀}]Cl₂ ? 25 H₂O ( 2 ; gly=glycine, ox=oxalate) have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, UV/Vis‐NIR spectra, thermogravimetric analyses, power X‐ray diffraction, and single‐crystal X‐ray diffraction. Compound 1 displays one interesting 3D framework built by three types of subunits, {P₅W₃₀}, [Sm₂Mn(μ‐H₂O)₂(OCH₂COO)₂(H₂O)₅]⁴⁺, and [Sm₄(OCH₂COO)₅ (H₂O)₁₃]²⁺, whereas 2 also manifests the other intriguing 3D architecture created by three types of subunits, {P₅W₃₀}, [SmCu(gly)(H₂O)₈]⁴⁺, and [Sm₂(ox)(H₂O)₈]⁴⁺. To our knowledge, 1 and 2 are the first 3D frameworks that contain {P₅W₃₀} units and TM/Ln–carboxylate–Ln connectors. The fluorescent properties of 1 and 2 have been investigated.     

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 CO₂ supercritical drying provide high‐surface‐area organic–inorganic hybrid materials. Examples including chitosan–SiO₂, chitosan–TiO₂, 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.     

Generation of Photocurrent by Visible‐Light Irradiation of Conjugated Dawson Polyoxophosphovanadotungstate–Porphyrin Copolymers

Four hybrid polyoxometalate–porphyrin copolymer films were obtained by the electrooxidation of zinc octaethylporphyrin in the presence of four different Dawson‐type polyoxometalates bearing two pyridyl groups (POM(py)₂) with various spacers. The POM monomers were designed around 1,3,5‐trisubstituted benzene rings. Two of the substituents of the benzene ring are linked to the pyridyl groups, and the third is connected to the POM subunit. The four monomers vary in the relative positions of the nitrogen atoms of the pyridine rings or in the distance from the carbonyl group. The monomers were fully characterized by ¹H, ³¹P, and ¹³C NMR spectroscopy, electrospray mass spectrometry, IR and UV/Vis spectroscopy, and electrochemistry. The copolymers were characterized by UV/Vis spectroscopy, X‐ray photoelectron spectroscopy, electrochemistry, and AFM. Their photovoltaic performance under visible light irradiation was investigated by photocurrent transient measurements under visible illumination.     

Hybrid Organic–Inorganic Antiperovskites

Substitution of A‐site and/or X‐site ions of ABX₃‐type perovskites with organic groups can give rise to hybrid perovskites, many of which display intriguing properties beyond their parent compounds. However, this method cannot be extended effectively to hybrid antiperovskites. Now, the design of hybrid antiperovskites under the guidance of the concept of Goldschmidt's tolerance factor is presented. Spherical anions were chosen for the A and B sites and spherical organic cations for the X site, and seven hybrid antiperovskites were obtained, including (F₃(H₂O)_x)(AlF₆)(H₂dabco)₃, ((Co(CN)₆)(H₂O)₅)(MF₆)(H₂dabco)₃ (M=Al³⁺, Cr³⁺, or In³⁺), (Co(CN)₆)(MF₆)(H₂pip)₃ (M=Al³⁺ or Cr³⁺), and (SbI₆)(AlF₆)(H₂dabco)₃. These new structures reveal that all ions at A, B, and X sites of inorganic antiperovskites can be replaced by molecular ions to form hybrid antiperovskites. This work will lead to the synthesis of a large family of hybrid antiperovskites.     

Hybrid Organic–Inorganic Silica Gel Carriers with Controlled Drug‐Delivery Properties

Pure and modified silica materials were synthesised by a sol–gel process and used as carrier for the controlled release of ibuprofen, selected as model drug. A one‐step synthesis was optimised for the preparation of various silica–drug composites by using tetraethoxysilane and 3‐aminopropyltriethoxysilane as precursors at different molar ratios. The presence of aminopropyl groups on the silica surface influences the drug‐delivery rate leading to a high degree the desorption process controlled.     

Redox‐Controlled Helical Self‐Assembly of a Polyoxometalate Complex

Polyoxometalate (POM) complex (DODA)₂[Mo₆O₁₉] with a symmetrical linear structure was prepared conveniently by replacing the tetrabutylammonium (TBA) counterions of Lindquist‐type cluster (TBA)₂[Mo₆O₁₉] with cationic surfactant dioctadecyldimethylammonium (DODA). A helical self‐assembled structure of the complex was formed in dichloromethane/propanol. The dynamically reversible transformation between helical and spherical assemblies on alternate UV irradiation and H₂O₂ oxidation was characterized by SEM, TEM, and UV/Vis studies. The redox‐controlled morphology change is modulated by variation of the electrostatic interactions between the inorganic polyanion and the organic cation DODA through controlling the redox properties of the POM component, as shown by the XRD, X‐ray photoelectron spectroscopic, and ¹H NMR measurements. The strategy applied herein is a unique example of targeted smart and helical assembly of POM complexes.     

Organic–Inorganic Hybrid Zinc Phosphate with 28‐Ring Channels

An organic–inorganic hybrid zinc phosphate with 28‐ring channels was synthesized by use of an organic ligand instead of organic amine template under a hydro(solvo)thermal condition. This crystalline zinc phosphate contains large channels constructed from 28 zinc and phosphate tetrahedral units. The walls of the channels consist of two types of zincophosphate chains, in which the Zn atoms are coordinated by 2,4,5‐tri(4‐pyridyl)‐imidazole ligands as pendent groups. This compound exhibits yellow emission and interesting properties of removing cobalt, cadmium, and mercury cations from aqueous solution. A new two‐dimensional organic–inorganic hybrid zincophosphate was also obtained by changing the solvent mixture ratios in the synthesis.     

Light‐ and Solvent‐Controlled Self‐Assembly Behavior of Spiropyran–Polyoxometalate–Alkyl Hybrid Molecules

A molecular photochromic spiropyran–polyoxometalate–alkyl organic–inorganic hybrid has been synthesized and fully characterized. The reversible switching of the hydrophobic spiropyran fragment to the hydrophilic merocyanine one can be easily achieved under light irradiation at different wavelengths. This switch changes the amphiphilic feature of the hybrid, leading to a light‐controlled self‐assembly behavior in solution. It has been shown that the hybrid can reversibly self‐assemble into vesicles in polar solvents and irreversibly into reverse vesicles in non‐polar solvents. The sizes of the vesicles and the reverse vesicles are both tunable by the polarity of the solvent, with the hydrophobic interactions being the main driving force.     

Self‐Assembly of a Giant Tetrahedral 3 d–4 f Single‐Molecule Magnet within a Polyoxometalate System

A giant tetrahedral heterometallic polyoxometalate (POM) [Dy₃₀Co₈Ge₁₂W₁₀₈O₄₀₈(OH)₄₂(OH₂)₃₀]^56?, which shows single‐molecule magnet (SMM) behavior, is described. This hybrid contains the largest number of 4f ions of any polyoxometalate (POM) reported to date and is the first to incorporate two different 3d–4f and 4f coordination cluster assemblies within same POM framework.     

Orientational Organization of Organic Semiconductors within Periodic Nanoscale Silica Channels: Modification of Fluorophore Photophysics through Hierarchical Self‐Assembly

Smart nanomaterials : The orientational organization of small organic semiconductors (anthracene, in this case) within periodic nanoscale silica channels (see figure) is achieved through a novel hierarchical self‐assembly approach. This elicits interesting optical effects and improved mechanical properties that could be of potential importance for functional materials.