Spin‐Coated Periodic Mesoporous Organosilica Thin Films—Towards a New Generation of Low‐Dielectric‐Constant Materials

Periodic mesoporous organosilica (PMO) thin films have been produced using an evaporation‐induced self‐assembly (EISA) spin‐coating procedure and a cationic surfactant template. The precursors are silsesquioxanes of the type (C₂H₅O)₃Si–R–Si(OC₂H₅)₃ or R′–[Si(OC₂H₅)₃]₃ with R = methene (–CH₂–), ethylene (–C₂H₂–), ethene (–C₂H₄–), 1,4‐phenylene (C₆H₄), and R′ = 1,3,5‐phenylene (C₆H₃). The surfactant is successfully removed by solvent extraction or calcination without any significant Si–C bond cleavage of the organic bridging groups R and R′ within the channel walls. The materials have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X‐ray diffraction (PXRD), and ²⁹Si and ¹³C magic‐angle spinning (MAS) NMR spectroscopy. The d‐spacing of the PMOs is found to be a function of R. Nanoindentation measurements reveal increased mechanical strength and stiffness for the PMOs with R = CH₂ and C₂H₄ compared to silica. Films with different organic‐group content have been prepared using mixtures of silsesquioxane and tetramethylorthosilicate (TMOS) precursors. The dielectric constant (k) is found to decrease with organic content, and values as low as 1.8 have been measured for films thermally treated to cause a “self‐hydrophobizing” bridging‐to‐terminal transformation of the methene to methyl groups with concomitant loss of silanols. Increasing the organic content and thermal treatment also increases the resistance to moisture adsorption in 60 and 80 %‐relative‐humidity (RH) environments. Methene PMO films treated at 500 °C are found to be practically unchanged after five days exposure to 80 % RH. These low dielectric constants, plus the good thermal and mechanical stability and the hydrophobicity suggest the potential utility of these films as low‐k layers in microelectronics.     

Fabrication of Hollow Inorganic Microspheres by Chemically Induced Self‐Transformation

Two contrasting approaches, involving either polymer‐mediated or fluoride‐mediated self‐transformation of amorphous solid particles, are described as general routes to the fabrication of hollow inorganic microspheres. Firstly, calcium carbonate and strontium tungstate hollow microspheres are fabricated in high yield using sodium poly(4‐styrenesulfonate) as a stabilizing agent for the formation and subsequent transformation of amorphous primary particles. Transformation occurs with retention of the bulk morphology by localized Ostwald ripening, in which preferential dissolution of the particle interior is coupled to the deposition of a porous external shell of loosely packed nanocrystals. Secondly, the fabrication process is extended to relatively stable amorphous microspheres, such as TiO₂ and SnO₂, by increasing the surface reactivity of the solid precursor particles. For this, fluoride ions, in the form of NH₄F and SnF₂, are used to produce well‐defined hollow spheroids of nanocrystalline TiO₂ and SnO₂, respectively. Our results suggest that the chemical self‐transformation of precursor objects under morphologically invariant conditions could be of general applicability in the preparation of a wide range of nanoparticle‐based hollow architectures for technological and biomedical applications.     

New Inorganic–Organic Hybrid Materials for HPLC Separation Obtained by Direct Synthesis in the Presence of a Surfactant

Nanostructured, mesoporous inorganic–organic hybrid xerogels were reproducibly synthesized by a sol–gel procedure. For the introduction of long alkyl chains into inorganic polymers, trifunctional n‐alkyltrialkoxysilanes of the type CH₃(CH₂)_nSi(OR)₃ (n = 7, 11, 17; R = CH₃, C₂H₅) were co‐condensed with Si(OEt)₄ (TEOS). The synthetic pathway involves the employment of n‐hexadecylamine as template and catalyst. The xerogels obtained by the present procedure consist of uniform spherical particles with a diameter of about 1 μm. The composition of the new materials was determined by ¹³C and ²⁹Si cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. In addition, the degree of organization was investigated by small angle X‐ray and electron diffraction. In accordance with ¹³C CP/MAS NMR spectroscopic measurements, the alkyl chains form a crystalline arrangement within the silica polymer. Brunauer–Emmett–Teller (BET) adsorption measurements confirm specific surface areas of up to 1400 m²/g. The material properties prove the xerogels to be suitable as stationary phases in high‐performance liquid chromatography (HPLC). These novel mesoporous, nanostructured materials have been successfully employed in HPLC for the first time. Different standard reference materials (SRMs) containing polycyclic aromatic hydrocarbons have been separated with the xerogels described in the present work.     

Lamellar Mesostructured Silicas with Chemically Significant Hierarchical Morphologies

We describe the hierarchical structures of mesostructured silicas assembled from electrically neutral and unsymmetrical Gemini surfactants of the type C_nH_2n+1NH(CH₂)_mNH₂ with n = 10, 12, 14 and m = 3, 4. As expected for Gemini surfactants with an all anti‐chain configuration and a packing parameter near 1.0, lamellar framework structures are formed, regardless of the length of the alkyl chain (n) and the number of carbon atoms (m) linking the two amino group centers. However, different layer curvatures and levels of hierarchical structure are observed depending on the delicate balance between the hydrophilic interactions at the surfactant head group–silica interface and the hydrophobic interactions between the surfactant alkyl groups. For Gemini derivatives with n = 12 or 14 and m = 3 or 4, well‐expressed hierarchical vesicles are formed that are analogous to those assembled previously from Gemini surfactants with m = 2. However, for n = 10, a new coiled slab structure (m = 3) and an onion‐like core–shell structure (m = 4) are formed. In addition, a previously unobserved stripe‐like silica structure is obtained from a C⁰₁₂₊₂₊₀ Gemini surfactant in combination with an α,ω‐diamine co‐surfactant. The relative stability of these hierarchical structures depends on the delicate competition between the long‐range elastic forces occurring in the hydrophobic region of the assembled surfactant and the short‐range chemical forces in the hydrophilic moiety. Lamellar silicas with hierarchical vesicular structures, the new coiled slab, and stripe‐like phases promise to be chemically significant morphologies, because they can minimize the framework pore length and provide optimal access to the framework walls under diffusion‐limited conditions.     

Water‐Dispersible,Ligand‐Free,and Extra‐Small (<10 nm) Titania Nanoparticles: Control Over Primary,Secondary, and Tertiary Agglomeration Through a Modified “Non‐Aqueous” Route

Non‐aqueous routes to inorganic nanoparticles are supposedly based on the absence of water; here, this view is partially challenged, showing that the presence of water (or moisture) is probably necessary, and is surely useful to achieve a precise control over the growth/aggregation phenomena leading to titanium dioxide nanoparticles. This study is focused on the preparation of size‐controlled and ligand‐free titania (anatase) nanoparticles in water dispersion. This is achieved through a three‐step process: 1) production of primary (3–4 nm) nanoparticles from titanium alkoxides (Ti(OnPr)₄, Ti(OnBu)₄ or Ti(OⁱPr)₄) in benzyl alcohol through the controlled addition of water; 2) thermal growth phase, where the aggregation of primary nanoparticles at 80 °C leads to secondary nanoparticles with a typical fractal dimension of 2.2–2.4; the primary particles are still identifiable as the individual crystallites composing the secondary nanoparticles; 3) precipitation/re‐dispersion in water, where secondary nanoparticles further agglomerate to yield tertiary nanoparticles. The size of the latter and their photocatalytic efficiency is primarily controlled by the nature of residual alkoxide chains; in particular, isopropoxide groups allow to produce anatase nanoparticles with an average size of 7–8 nm in water dispersion and in the absence of any stabilizing ligand, which is an unprecedented result.     

Preparation of Functional Hybrid Glass Material from Platinum (II) Complexes for Broadband Nonlinear Absorption of Light

The synthesis of trans‐di(arylalkynyl)diphosphine platinum(II) complexes bearing trialkoxysilane groups is described, as well as the preparation of siloxane‐based hybrid materials from organometallic chromophores through a modified sol–gel process. Glass materials prepared from trans‐[P(n–Bu)₃]₂Pt[(C≡C–p–C₆H₄–C≡C–p–C₆H₄–CH₂O(CO)NH(CH₂)₃Si(OC₂H₅)₃]₂ generally show spectral transmittance, absorption and luminescence similar to that of solutions reported in the literature. Measurements of optical power limiting for the hybrid glass are carried out, and show broadband nonlinear absorption throughout the whole visible wavelength range with clamping values in the range 0.2–7 µJ at 120 mM chromophore concentration. The sol–gel process using urethane‐propyltriethoxysilane‐functionalized chromophores as precursors appears to be a valid method for formation of robust silicate materials with grafted diarylethynyl Pt(II) complexes for OPL devices.     

A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (M_n = 4 × 10³ g mol^?1, M_w/M_n < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.     

Designing of a Magnetodielectric System in Hybrid Organic–Inorganic Framework,a Perovskite Layered Phosphonate MnO3PC6H4‐m‐Br⋅H2O

Very few hybrid organic–inorganic framework (HOIF) exhibit direct coupling between spins and dipoles and are also restricted to a particular COOH‐based system. It is shown how one can design a hybrid system to obtain such coupling based on the rational design of the organic ligands. The layered phosphonate, MnO₃PC₆H₅?H₂O, consisting of perovskite layers stacked with organic phenyl layers, is used as a starting potential candidate. To introduce dipole moment, a closely related metal phosphonate, MnO₃PC₆H₄‐m‐Br?H₂O is designed. For this purpose, this phosphonate is prepared from 3‐bromophenylphosphonic acid that features one electronegative bromine atom directly attached on the aromatic ring in the meta position, lowering the symmetry of precursor itself. Thus, bromobenzene moieties in MnO₃PC₆H₄‐m‐Br?H₂O induce a finite dipole moment. This new designed compound exhibits complex magnetism, as observed in layered alkyl chains MnO₃PC_nH_2n+1?H₂O materials, namely, 2D magnetic ordering ≈20 K followed by weak ferromagnetic ordering below 12 K (T₁) with a magnetic field (H)‐induced transition ≈25 kOe below T₁. All these magnetic features are exactly captured in the T and H‐dependent dielectric constant, ε′(T) and ε′(H). This demonstrates direct magnetodielectric coupling in this designed hybrid and yields a new path to tune multiferroic ordering and magnetodielectric coupling.     

Optimization of interdigitated back contact silicon heterojunction solar cells: tailoring hetero‐interface band structures while maintaining surface passivation

Interdigitated back contact silicon heterojunction (IBC‐SHJ) solar cells have the potential for high open circuit voltage (V_OC) due to the surface passivation and heterojunction contacts, and high short circuit current density (J_SC) due to all back contact design. Intrinsic amorphous silicon (a‐Si:H) buffer layer at the rear surface improve the surface passivation hence V_OC and J_SC, but degrade fill factor (FF) from an “S” shape J–V curve. Two‐dimensional (2D) simulation using “Sentaurus device” demonstrates that the low FF is related to the valence band offset (energy barrier) at the hetero‐interface. Three approaches to the buffer layer are suggested to improve the FF: (1) reduced thickness, (2) increased conductivity, and/or (3) reduced band gap. Experimental IBC‐SHJ solar cells with reduced buffer thickness (<5 nm) and increased conductivity with low boron doping significantly improves FF, consistent with simulation. However, this has only marginal effect on efficiency since J_SC and V_OC also decrease due to poor surface passivation. A narrow band gap a‐Si:H buffer layer improves cell efficiency to 13.5% with unoptimized passivation quality. These results demonstrate that tailoring the hetero‐interface band structure is critical for achieving high FF. Simulations predicts that efficiences >23% are possible on planar devices with optimized pitch dimensions and achievable surface passivation, and 26% with light trapping. This work provides criterion to design IBC‐SHJ solar cell structures and optimize cell performance. Copyright © 2010 John Wiley & Sons, Ltd.     

Growth of 1‐eV GaNAsSb‐based photovoltaic cell on silicon substrate at different As/Ga beam equivalent pressure ratios

We report the performance of 1‐eV GaNAsSb‐based photovoltaic samples grown on a Si substrate using molecular beam epitaxy at different As/Ga beam equivalent pressure (BEP) ratios. The light current–voltage curve and spectral response of the samples were measured. The sample grown at an As/Ga BEP ratio of 10 showed the highest energy conversion efficiency with an open circuit voltage (V_OC) of 0.529 V and a short circuit current density of 17.0 mA/cm². This measured V_OC is the highest ever reported value in GaNAsSb 1‐eV photovoltaic cell, resulting in the lowest ever reported E_g/q‐V_OC of 0.50 eV. The increase in the As/Ga BEP ratio also resulted in an increase in the bandgap‐voltage offset value (E_g/q‐V_OC) and a decrease in quantum efficiency up to As/Ga BEP ratio of 18. Copyright © 2015 John Wiley & Sons, Ltd.     

Simple Synthesis of Hollow Tin Dioxide Microspheres and Their Application to Lithium‐Ion Battery Anodes

Hollow tin dioxide (SnO₂) microspheres were synthesized by the simple heat treatment of a mixture composed of tin(IV ) tetrachloride pentahydrate (SnCl₄·5H₂O) and resorcinol–formaldehyde gel (RF gel). Because hollow structures were formed during the heat treatment, the pre‐formation of template and the adsorption of target precursor on template are unnecessary in the current method, leading to simplified synthetic procedures and facilitating mass production. Field‐emission scanning electron microscopy (FE‐SEM) images showed 1.7–2.5 μm sized hollow spherical particles. Transmission electron microscopy (TEM) images showed that the produced spherical particles are composed of a hollow inner cavity and thin outer shell. When the hollow SnO₂ microspheres were used as a lithium‐battery anode, they exhibited extraordinarily high discharge capacities and coulombic efficiency. The reported synthetic procedure is straightforward and inexpensive, and consequently can be readily adopted to produce large quantities of hollow SnO₂ microspheres. This straightforward approach can be extended for the synthesis of other hollow microspheres including those obtained from ZrO₂ and ZrO₂/CeO₂ solid solutions.     

Highly Stable Two‐Dimensional Tin(II) Iodide Hybrid Organic–Inorganic Perovskite Based on Stilbene Derivative

Hybrid organic–inorganic perovskites have recently emerged as potential disruptive photovoltaic technology. However, the toxicity of lead used in state‐of‐the‐art hybrid perovskites solar cell prevents large‐scale commercialization, which calls for lead‐free alternatives. Sn‐based perovskites have been considered as alternatives but they are limited by rapid oxidation and decomposition in ambient air. Here, an Sn‐based two‐dimensional hybrid organic–inorganic perovskites [A₂B_(n‐1)Sn_nI_(3n+1)] (n = 1 and 2) are reported with improved air stability, using bulky stilbene derivatives as the organic cations (2‐(4‐(3‐fluoro)stilbenyl)ethanammonium iodide (FSAI)). The moisture stability of the [(FSA)₂SnI₄] perovskites is attributed to the hydrophobic properties of fluorine‐functionalized organic chains (FSA), as well as the strong cohesive bonding in the organic chains provided by H bonds, CH···X type H bonds, weak interlayer F···F interaction, and weak face‐to‐face type π‐π interactions. The photodetector device fabricated on exfoliated single crystal flake of [(FSA)₂SnI₄] exhibits fast and stable photoconductor response.     

Gd2O(CO3)2 · H2O Particles and the Corresponding Gd2O3: Synthesis and Applications of Magnetic Resonance Contrast Agents and Template Particles for Hollow Spheres and Hybrid Composites

The solution approach was employed to yield multifunctional amorphous Gd₂O(CO₃)₂ · H₂O colloidal spheres by reflux of an aqueous solution containing GdCl₃ · 6H₂O and urea. By elongating the reaction time, crystalline rhombus‐ shaped Gd₂O(CO₃)₂ · H₂O with at least 87% yield could be formed and were also accompanied by some rectangular particles. High‐resolution synchrotron powder X‐ray diffraction provides crystal structure information, such as cell dimensions, and indexes the exact crystal packing with hexagonal symmetry, which is absent from the Joint Committee on Powder Diffraction Standards file, for the crystalline rhombus sample. Particle formation was studied based on the reaction time and the concentration ratio of [urea]/[GdCl₃ · 6H₂O]. After a calcination process, the amorphous spheres and crystalline rhombus Gd₂O(CO₃)₂ · H₂O particles convert into crystalline Gd₂O₃ at temperatures above 600 °C. For in vitro magnetic resonance imaging (MRI), both Gd₂O(CO₃)₂ · H₂O and Gd₂O₃ species show the promising T₁‐ and T₂‐weighted effects and could potentially serve as bimodal T₁‐positive and T₂‐negative contrast agents. The amorphous Gd₂O(CO₃)₂ · H₂O contrast agent further demonstrates enhanced contrast of the liver and kidney using a dynamic contrast‐enhanced MR imaging (DCE‐MRI) technique for in vivo investigation. The multifunctional capability of the amorphous Gd₂O(CO₃)₂ · H₂O spheres was also evidenced by the formation of nanoshells using these amorphous spheres as the template. Surface engineering of the amorphous Gd₂O(CO₃)₂ · H₂O spheres could be performed by covalent bonding to form hollow silica nanoshells and hollow silica@Fe₃O₄ hybrid particles.     

STM Lithography in an Organic Self‐Assembled Monolayer

We describe the suitability of ultra‐high vacuum scanning tunneling microscopy (UHV‐STM) based nanolithography by using highly ordered monomolecular organic films, called self‐assembled monolayers (SAMs), as ultrathin resists. Organothiol‐type SAMs such as hexadecanethiol (SH–(CH₂)₁₅–CH₃) and N‐biphenylthiol (SH–(C₆H₆)₂–NO₂) monolayers have been prepared by immersion on gold films and Au(111) single crystals. Organosilane‐type SAMs such as octadecyltrichlorosilane (SiCl₃–(CH₂)₁₇–CH₃) monolayers have been prepared on hydroxylated Si(100) surfaces as well as hydroxylated chromium film surfaces. Dense line patterns have been written by UHV‐STM in constant current mode for various tunneling parameters (gap voltage, tunneling current, scan speed, and orientation) and transferred into the underlying substrate by wet etch techniques. The etched structures have been analyzed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Best resolution has been achieved without etch transfer for a 20 nm × 20 nm square written in hexadecanethiol/Au(111) with an edge definition of about 5 nm. Etch transfer of the STM nanopatterns in Au films resulted in 55 nm dense line patterns (15 nm deep) mainly broadened by the isotropic etch characteristic, while 35 nm wide and 30 nm deep dense line patterns written in octadecyltrichlorosilane/Si(100) and anisotropically etched into Si(100) could be achieved.     

Diphenylmethanofullerenes: New and Efficient Acceptors in Bulk‐Heterojunction Solar Cells

A novel fullerene derivative, 1,1‐bis(4,4′‐dodecyloxyphenyl)‐(5,6) C₆₁, diphenylmethanofullerene (DPM‐12), has been investigated as a possible electron acceptor in photovoltaic devices, in combination with two different conjugated polymers poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐para‐phenylene vinylene] (OC₁C₁₀‐PPV) and poly[3‐hexyl thiophene‐2,5‐diyl] (P3HT). High open‐circuit voltages, V_OC = 0.92 and 0.65 V, have been measured for OC₁C₁₀‐PPV:DPM‐12‐ and P3HT:DPM‐12‐based devices, respectively. In both cases, V_OC is 100 mV above the values measured on devices using another routinely used fullerene acceptor, [6,6]‐phenyl‐C₆₁ butyric acid methyl ester (PCBM). This is somewhat unexpected when taking into account the identical redox potentials of both acceptor materials at room temperature. The temperature‐dependent V_OC reveals, however, the same effective bandgap (HOMO_Polymer–LUMO_Fullerene; HOMO = highest occupied molecular orbital, LUMO = lowest unoccupied molecular orbital) of 1.15 and 0.9 eV for OC₁C₁₀‐PPV and P3HT, respectively, independent of the acceptor used. The higher V_OC at room temperature is explained by different ideality factors in the dark‐diode characteristics. Under white‐light illumination (80 mW cm^–2), photocurrent densities of 1.3 and 4.7 mA cm^–2 have been obtained in the OC₁C₁₀‐PPV:DPM‐12‐ and P3HT:DPM‐12‐based devices, respectively. Temperature‐dependent current density versus voltage characteristics reveal a thermally activated (shallow trap recombination limited) photocurrent in the case of OC₁C₁₀‐PPV:DPM‐12, and a nearly temperature‐independent current density in P3HT:DPM‐12. The latter clearly indicates that charge carriers traverse the active layer without significant recombination, which is due to the higher hole‐mobility–lifetime product in P3HT. At the same time, the field‐effect electron mobility in pure DPM‐12 has been found to be μ_e = 2 × 10^–4 cm² V^–1 s^–1, that is, forty‐times lower than the one measured in PCBM (μ_e = 8 × 10^–3 cm² V^–1 s^–1).     

Application of copper thiocyanate for high open‐circuit voltages of CdTe solar cells

Copper thiocyanate (CuSCN) has proven to be a low‐cost, efficient hole‐transporting material for the emerging organic–inorganic perovskite solar cells. Herein, we report that CuSCN can also be applied to CdTe thin‐film solar cells to achieve high open‐circuit voltages (V_OCs). By optimizing the thickness of the thermally evaporated CuSCN films, CdTe cells fabricated by close space sublimation in the superstrate configuration have achieved V_OCs as high as 872 mV, which is about 20–25 mV higher than the highest V_OC for the reference cells using the standard Cu/Au back contacts. CuSCN is a wide bandgap p‐type conductor with a conduction band higher than that of CdTe, leading to a conduction band offset that reflects electrons in CdTe, partially explaining the improved V_OCs. However, due to the low conductivity of CuSCN, CdTe cells using CuSCN/Au back contacts exhibited slightly lower fill factors than the cells using Cu/Au back contacts. With optimized CdS:O window layers, the power conversion efficiency of the best CdTe cell, using CuSCN/Au back contact, is 14.7%: slightly lower than that of the best cell (15.2%) using Cu/Au back contact. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly Connected Silicon–Copper Alloy Mixture Nanotubes as High‐Rate and Durable Anode Materials for Lithium‐Ion Batteries

Seeking high‐capacity, high‐rate, and durable anode materials for lithium‐ion batteries (LIBs) has been a crucial aspect to promote the use of electric vehicles and other portable electronics. Here, a novel alloy‐forming approach to convert amorphous Si (a‐Si)‐coated copper oxide (CuO) core–shell nanowires (NWs) into hollow and highly interconnected Si–Cu alloy (mixture) nanotubes is reported. Upon a simple H₂ annealing, the CuO cores are reduced and diffused out to alloy with the a‐Si shell, producing highly interconnected hollow Si–Cu alloy nanotubes, which can serve as high‐capacity and self‐conductive anode structures with robust mechanical support. A high specific capacity of 1010 mAh g^?1 (or 780 mAh g^?1) has been achieved after 1000 cycles at 3.4 A g^?1 (or 20 A g^?1), with a capacity retention rate of ≈84% (≈88%), without the use of any binder or conductive agent. Remarkably, they can survive an extremely fast charging rate at 70 A g^?1 for 35 runs (corresponding to one full cycle in 30 s) and recover 88% capacity. This novel alloy‐nanotube structure could represent an ideal candidate to fulfill the true potential of Si‐loaded LIB applications.     

Some new organic–inorganic hybrid semiconductors based on metal halide units: structural,optical and related properties†

The structural, optical and related properties of organic–inorganic hybrid semiconductors based on the organic molecules (cations) CH₃NH₃, H₃N(CH₂)₆NH₃, C₆H₅CH₂NH₃, CH₃C₆H₄CH₂NH₃, CH₃OC₆H₄CH₂CH₂NH₃, (H₂N)₂CS(CH₂)₄SC(NH₂)₂, H₃NCH₂CH₂OCH₂CH₂NH₃, C₆H₅CH₂CH₂SC(NH₂)₂, C₁₀H₂₁SC(NH₂)₂, O₂NC₆H₄CH₂SC(NH₂)₂, 1-naphthylmethylammonium C₁₀H₇CH₂NH₃, 9-anthrylmethylammonium C₁₄H₉CH₂NH₃ and 1-pyrenylmethylammonium C₁₆H₉CH₂NH₃ and the inorganic units MX_n (anions) (M≡Bi, Sb, Sn, Pb, Cu, Ag; X≡I, Br, Cl) are described. There is evidence that the position, intensity and shape of the excitonic bands depend on the order/disorder of the inorganic component and on the electronic interaction between organic and inorganic components. Copyright © 2000 John Wiley & Sons, Ltd.     

Tetrakis(phthalocyaninato) terbium–cadmium quadruple-decker liquid crystals with good semiconducting properties

Neutral and mono-oxidized states of novel sandwich-type tetrakis[2,3,9,10,16,17,23,24-octa(dodecanoyloxy)phthalocyaninato] terbium–cadmium quadruple-decker complex {[Pc(OC₁₂H₂₅)₈]Tb[Pc(OC₁₂H₂₅)₈]Cd[Pc(OC₁₂H₂₅)₈]Tb[Pc(OC₁₂H₂₅)₈]} (1) and {[Pc(OC₁₂H₂₅)₈]Tb[Pc(OC₁₂H₂₅)₈]Cd[Pc(OC₁₂H₂₅)₈]Tb[Pc(OC₁₂H₂₅)₈]}·SbCl₆ (2) were synthesized and spectroscopically characterized. Polarized optical microscope (POM) together with differential scanning calorimeter (DSC) measurement revealed their similar two rectangular columnar mesophases over a relatively lower temperature range and higher temperature range, respectively, within their wide liquid crystal temperature range of 19–266 °C for 1 and 4–249 °C for 2. Temperature-dependent X-ray diffraction (XRD) analysis result disclosed the slight difference in terms of the neighboring quadruple-decker π–π stacking between these two mesophases, which in turn accounts for their electric conducting behavior along with the change in temperature. In addition, due to the ionic conductive nature, the mono-oxidized liquid crystals of 2 display more than 2 order of magnitude higher electric conductivity than that for 1, with the highest value 4.1 × 10⁻⁴ S cm⁻¹ achieved at 140 °C.     

Synthesis of Ruthenium Nanoparticles Stabilized by Heavily Fluorinated Compounds

Ruthenium nanoparticles have been prepared by hydrogenation of the complex Ru(COD)(COT) (COD = 1,5‐cyclooctadiene, COT = 1,3,5‐cyclooctatriene) in the presence of i) heavily fluorinated solid compounds as stabilizers (para‐bis(perfluorooctyl)benzene, 2,4,6‐tris(perfluorooctyl)aniline, and the non‐functionalized 11H,11H,12H,12H,13H,13H,14H,14H,15H,15H,16H, 16H‐perfluorohexacosane (C₁₀F₂₁‐(CH₂)₆‐C₁₀F₂₁)); and ii) the liquid 1H,1H,2H,2H‐perfluorodecylamine. The particles have been characterized by IR spectroscopy, elemental analysis, transmission electron microscopy (TEM), high‐resolution TEM, wide‐ and small‐angle X‐ray scattering (WAXS and SAXS), and scanning electron microscopy with a field‐emission gun (SEM‐FEG). TEM images indicate the presence of aggregated small nanoparticles with a regular mean size of ca. 3 nm. These nanoparticles display the hexagonal close‐packed structure of bulk ruthenium, as shown by WAXS analysis. HRTEM and SEM‐FEG analyses reveal the tendency of the particles to self‐assemble into superstructures (spheres) that can be more or less well defined depending on the fluorinated compound and/or the reaction conditions. This behavior has been confirmed in one case by SAXS measurements attesting the presence of small nanoparticles that are closely packed into clusters.