Crosslinking ionic oligomers as conformable precursors to calcium carbonate.

Inorganic materials have essential roles in society, including in building construction, optical devices, mechanical engineering and as biomaterials1-4. However, the manufacture of inorganic materials is limited by classical crystallization5, which often produces powders rather than monoliths with continuous structures. Several precursors that enable non-classical crystallization-such as pre-nucleation clusters6-8, dense liquid droplets9,10, polymer-induced liquid precursor phases11-13 and nanoparticles14-have been proposed to improve the construction of inorganic materials, but the large-scale application of these precursors in monolith preparations is limited by availability and by practical considerations. Inspired by the processability of polymeric materials that can be manufactured by crosslinking monomers or oligomers15, here we demonstrate the construction of continuously structured inorganic materials by crosslinking ionic oligomers. Using calcium carbonate as a model, we obtain a large quantity of its oligomers (CaCO3)n with controllable molecular weights, in which triethylamine acts as a capping agent to stabilize the oligomers. The removal of triethylamine initiates crosslinking of the (CaCO3)n oligomers, and thus the rapid construction of pure monolithic calcium carbonate and even single crystals with a continuous internal structure. The fluid-like behaviour of the oligomer precursor enables it to be readily processed or moulded into shapes, even for materials with structural complexity and variable morphologies. The material construction strategy that we introduce here arises from a fusion of classic inorganic and polymer chemistry, and uses the same cross-linking process for the manufacture the materials.

Two modes of transformation of amorphous calcium carbonate films in air.

Large-area amorphous calcium carbonate (ACC) films in air are shown to be transformed into crystalline calcium carbonate (CaCO(3)) films via two modes-dissolution-recrystallization and solid-solid phase transition-depending on the relative humidity of the air and the temperature. Moisture in the air promotes the transformation of ACC into crystalline forms via a dissolution-recrystallization process. Increasing the humidity increases the rate of ACC crystallization and gives rise to films with numerous large pores. As the temperature is increased, the effect of moisture in the air is reduced and solid-solid transition by thermal activation becomes the dominant transformation mechanism. At 100 and 120 degrees C, ACC films are transformed into predominantly (110) oriented crystalline films. Collectively, the results show that calcium carbonate films with different morphologies, crystal phases, and structures can be obtained by controlling the humidity and temperature. This ability to control the transformation of ACC should assist in clarifying the role of ACC in the biomineralization of CaCO(3) and should open new avenues for preparing CaCO(3) films with oriented and fine structure.

Stable superhydrophobic organic-inorganic hybrid films by electrostatic self-assembly.

Organic-inorganic hybrid films were prepared through layer-by-layer (LBL) deposition of poly(allylamine hydrochloride) (PAH) and ZrO(2) nanoparticles coated with poly(acrylic acid) (PAA), allowing facile control of surface roughness and hydrophobicity. Superhydrophobic behavior was observed after deposition of silica nanoparticles and a simple fluorination of the surface. The structure of films was controlled by the number of deposition cycles using PAA-coated 100 nm ZrO(2) nanoparticles, the particle size, and the prelayer with PAH and PAA. The change in the apparent water contact angle of (PAH/PAA-coated ZrO(2)n surfaces without fluorination of the surface agrees with Cassie and Baxter's model for nonwetted surfaces even though the outermost surface itself is hydrophilic. Superhydrophobic surfaces were then successfully developed by the deposition of hydrophilic silica nanoparticles on a 10 bilayer surface of PAH/PAA-coated ZrO(2), and a simple fluorination. Moreover, the chemical stability of the film was greatly increased by heat-induced cross-linking of the film. The incorporation of ZrO(2) nanoparticles in superhydrophobic films promises better mechanical properties than the organic film.

[Studies on photoluminescence spectra of polyfluorene under modulation of electric field].

The photoluminescence of polyfluorene thin film modulated by an electric field are studied. The results show that the photoluminescence from polyfluorene film can obviously quenched by the extra electric field, which is attributed to the electric field-induced dissociation of photogeneration excitons. The dependence of the exciton dissociation rate constant on the intensity of electric filed is fitted. The average hopping distance of element charge is 0.68 nm in PFO. This volume is comparable with the reported results in Alq3 and polymers. The spectral dependence of the factor of EFIQP is given. The dissociation of hot-exciton is deduced, which influences on the spectral dependence of the EFIQP factor slightly.

Biomineralization-based virus shell-engineering: towards neutralization escape and tropism expansion.

Biomineralization-based virus shell-engineering (BVSE) is a potential surface modification strategy to afford a biocompatible and biodegradable calcium phosphate (CaPi) shell onto single virus, allowing development of Trojan virus with enhanced infection, expanded tropism and neutralization escape, which open up the multiple applications of virus in biomedicines and materials.