Hybrid layer-by-layer films based on lanthanide-bridged silicotungstates and poly(ethylenimine)

Product-oriented decomposition of lignocellulose catalyzed by novel polyoxometalates-ionic liquid mixture

Lignocellulose was oxidatively decomposed in a newly developed polyoxometalates-imidazolium ionic liquid mixture. Aromatic compounds covering acids, esters, ketones, aldehydes, and phenols were selectively produced under various conditions. 4-Hydroxylbenzoic acid was dominatingly yielded under low temperature and high oxidant concentration. Phenolic compounds were mainly generated at high temperature with a selectivity of 45.1% and a yield of 4.3%, higher than those generated in similar polyoxometalates-ionic liquids system. The products distributions and residues of lignocellulose decomposition under various conditions were characterized; the influences of the ionic liquids anions on the polyoxometalates-ionic liquids complex formation, the acidic and redox properties of the catalyst, and the final products were profoundly investigated; and a tentative reacting process was proposed. The ionic liquid could be recycled for five times. This work not only provided a new lignocellulose decomposition strategy to produce aromatic products, but also offered a guidance for product-oriented lignocellulose decomposition.

Multielectrocatalysis by layer-by-layer films based on pararosaniline and vanadium-substituted phosphomolybdate

Hybrid multilayer films based on the two molecular species pararosaniline (PR) and Keggin-type polyoxometalate K5[PMo11VO40)] (PMo11V) were prepared on different substrates using the electrostatic layer-by-layer (LbL) self-assembly method. The film buildup, monitored by electronic spectroscopy, showed a regular stepwise growth, and X-ray photoelectron spectroscopy data confirmed the presence of both molecular components within the LbL films. Scanning electron microscopy images revealed a completely covered surface with a nonuniform distribution of film components, and atomic force microscopy images confirmed a rough surface. The film electrochemical responses and permeability were studied by cyclic voltammetry. Films revealed three Mo-based redox processes (Mo(VI) → Mo(V)) and one V-based redox process (V(V) → V(IV)) in the potential range between 0.8 and -0.4 V vs Ag/AgCl. Studies with the redox probes [Fe(CN)6](3-/4-) and [Ru(NH3)6](3+/2+) showed that the films maintain the permeability even after six bilayers. Furthermore, the {PR/PMo11V}n multilayer films exhibit excellent Mo-based electrocatalytic activity toward reduction of iodate and V-based electrocatalytic activity toward ascorbic acid oxidation, thus acting as a versatile multielectrocatalyst.

Characterization of Strong and Crystalline Polyvinyl Alcohol/Montmorillonite Films Prepared by Layer-by-Layer Deposition Method

The preparation of a high-strength and highly crystalline nanocomposite with a layered structure by the use of layer-by-layer deposition (LbL) method from polyvinyl alcohol (PVOH) and montmorillonite (MMT) platelets is reported. The crystallinity and interactions between the components were studied by the use of Fourier transform infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The nanocomposite film structure was investigated by the use of scanning electron microscope (SEM) and atomic force microscopy (AFM). The stiffness of the LbL PVOH/MMT film was significantly higher compared to pure PVOH and conventional PVOH/MMT nanocomposite. The structural and thermal studies on thin PVOH/MMT films indicated the enhanced crystallinity of the polymer.

Lanthano phosphomolybdate-decorated silica nanoparticles: novel hybrid materials with photochromic properties

Novel hybrid nanomaterials prepared through the immobilization of phosphomolybdates onto functional silica nanoparticles revealed promising photochromic properties under UV irradiation.