•The novel TiO2-SiO2 shell was constructed with TiO2 nanosheets and silica species.•The formation mechanism involves the growth of TiO2 and redeposition of silica.•The strategy could be applied in the synthesis of yolk@shell nanocatalyst.In this work, a novel strategy has been proposed to synthesize a hierarchical Pt@TiO2-mSiO2 yolk@shell nanocatalyst firstly. Inner active sites could be protected by the TiO2-mSiO2 shell. The formation mechanism involves the in-situ growth of TiO2 nanosheets and simultaneous redeposition of etch-released silica species. TEM images were employed to characterize each step of the synthesis process. During the hydrothermal process, original TiO2 layer can be converted into a hierarchical structure and the inner SiO2 sphere was etched out automatically. Furthermore, the reduction of 4-nitrophenol had been used to test the hierarchical Pt@TiO2-mSiO2 yolk@shell nanocatalyst. The mixed oxides shell was constructed with in-situ grown hierarchical TiO2 nanosheets and redeposited SiO2.

In this work, we report a feasible approach to synthesize a ternary nanocomposites, Pt/lanthanum doped mesoporous zirconium oxide (Pt/La2O3-ZrO2), via an effective two-step method. Ordered mesoporous La2O3-ZrO2 composites were firstly fabricated with mesoporous silica KIT-6 as a hard template. Subsequently, uniform Pt nanoparticles encapsulated by 4 hydroxyl-terminated poly (amidoamine) (G4-OH PAMAM) dendrimers were deposited on the La2O3-ZrO2 composites. The as-prepared samples were characterized by transmission electron microscope (TEM), N2 adsorption–desorption isotherm analysis, energy dispersion X-ray analysis (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (H2-TPR). The average size of PtDENs was found to be 1.48 nm in diameter. Furthermore, the introduction of La could improve the structure of the supports which was confirmed by XRD and H2-TPR analysis. The reduction of p-nitrophenol to p-aminophenol by NaBH4 was utilized to evaluate the catalytic performances of catalysts. Results indicated that the Pt/La2O3-ZrO2 catalyst calcined in nitrogen at 550 °C exhibited the highest catalytic performance and still kept the high catalytic activity even after six cycles. This phenomenon suggests that synergistic effect among Pt-Zr-La could enhance the catalytic efficiency. Finally, reaction mechanism was proposed for the reduction of p-nitrophenol.Download high-res image (61KB)Download full-size image

Hybrids of polyacetylene (PA) with multiwalled carbon nanotubes (MWNTs) were fabricated by wrapping PA derivatives containing stigmasterol and pivalic acid moieties onto MWNTs walls. The PA derivatives with moderate molecular weights (Mn ~ 24409) were proved to adopt a single-handed helical structure stabilized by asymmetric hydrogen bonding force and stereo-hindrance effect. Convincing experimental results show that PA had been wrapped evenly on the surface of MWNTs without damaging their internal structures. Moreover, the helical structure of PA became more compact and ordered after wrapping around MWNTs. The incorporation of stigmasterol moieties could contribute to enhancing the microwave absorbing properties and decreasing infrared emissivities. PA@MWNTs showed a minimum reflection loss value of −20.65 dB at 9.7 GHz and the bandwidth of reflection loss less than −10 dB (90% absorption) was 3.2 GHz. Meanwhile, PA@MWNTs composites had a much lower infrared emissivity value (ε = 0.503) than raw MWNTs. The efficient microwave absorption and low infrared emissivity might result from the synergistic effect of the extraordinary helical structure of PA and π-electronic interactions between the organic substituents and inorganic MWNTs walls, which provides a promising method to prepare materials with low infrared emissivities and excellent microwave absorption properties.

•A novel polyacetylene based on stigmasterol has been successfully prepared.•Hydrogen bonding interactions induce the helical conformation.•Helical structures are sensitive to solvent effect and monomer ratio variations.•The optically active poly(N-propargyamide)s exhibit tunable infrared emissivity.Novel chiral N-propargylamide based on stigmasterol (M1, HCCCH2NHCOCH2CH2COO-R, R = stigmasteryl) and achiral N-propargylamide based on pivalic acid (M2) were prepared and (co)polymerized with rhodium zwitterions catalyst in CHCl3 to afford helical polyacetylenes with moderate molecular weights (8997–26777) in good yields. The polymers were characterized by Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC). Ultraviolet–visible spectroscopy (UV–Vis) and circular dichroism (CD) absorption spectra demonstrated that the as-prepared polymers could form helical structures with a preferential helicity. The formation of hydrogen bonds of poly(M1) in CHCl3 was investigated according to the solution sate IR spectroscopic data. The single-handed helical conformation and polymerization degree of the new-typed poly(N-propargylamide)s could be controlled by the changing the feed ratio of chiral and achiral monomers. Furthermore, the infrared emissivity values (0.536–0.798) of copolymers were investigated at 8–14 μm by the Infrared Emissometer.Download high-res image (279KB)Download full-size image

Recently, novel morphological nanocomposites have attracted increasing attention due to their unique features. In this work, a 3D hierarchical magnetic Fe@Pt/Ti(OH)4 nanoarchitecture has been synthesized successfully. TEM images were used to confirm the success of each of the synthesis steps, and the reduction of 4-NP to 4-AP was employed to evaluate their catalytic performance. Their large surface area and nanorod structure guarantee their good catalytic performance. Furthermore, the as-prepared nanocapsule shows excellent anti-sintering properties for the physical barrier effects of Ti(OH)4 nanorods. The sample calcined at 700 °C showed the highest catalytic activity in our work due to the decomposition of Ti(OH)4. Finally, the synthesized Fe@Pt/Ti(OH)4 nanocomposite could be easily recycled.

The Pt magnetic nanocatalysts with a TiO2 or CeO2 layer have been fabricated successfully. The mSiO2/Pt/MOx/Fe hybrids have a CeO2 or TiO2 layer synthesized through hydrothermal methods and a moveable magnetic Fe core constructed by hydrogen reduction. The obtained nanocapsules were characterized by several techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersion X-ray analysis (EDX). The catalytic evaluation was tested on the reduction of 4-NP to 4-AP monitored by UV-Vis spectroscpoy. The mesoporous SiO2 shell served as an effective barrier to prevent the migration and aggregation of Pt NPs during calcination. Besides, the oxide layers have an apparent co-catalysis effect to improve the catalytic activity. The mSiO2/Pt/MOx/α-Fe2O3 samples were calcined at different temperatures and the final samples exhibited entirely different catalytic activity. Additionally, a possible mechanism was proposed to explain the results. Furthermore, the synthesized mSiO2/Pt/MOx/Fe hybrids could be easily recycled using a magnet and the catalytic activity did not decrease obviously after five runs.

•The mSiO2/Pt/NCSs nanocomposites have been synthesized by a facile three-step method.•The nanocomposites show an excellent sinter-resistant stability.•The inner hollow structure plays a key role in the excellent catalytic activity.•Synthesized HSC550 have an excellent reusability.A synthetic strategy has been developed to encapsulate Pt nanoparticles in heterogeneous catalysts to prevent their sintering. This method involves the preparation of Pt/nanocarbon spheres composites, the formation of mesoporous silica layers, and finally the removal of CTAB surfactant and NCSs by refluxing and calcination, respectively. TEM images were used to confirm the success of each step, and the catalytic evaluation was tested on the reduction of p-NPh to p-APh monitored by a UV–vis spectra. Besides, the prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherms, energy dispersion X-ray analysis (EDX), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) as well. It was found that the encapsulated Pt nanoparticles could resist sintering up to 750 °C, whereas the catalysts without silica layer protection were shown to sinter by 350 °C. When the calcination temperature is 550 °C, the obtained materials exhibited the highest catalytic activity. Thus, the hollow sphere structure and the mesoporous silica played a key role in the high catalytic performance. Besides, the sample has an excellent reusability without obvious decrease of the catalytic activities even after five cycles. Finally, a possible mechanism was proposed to explain the well catalytic performance.Download high-res image (134KB)Download full-size image

To study the waterproof of coating materials, a series of waterborne polyurethanes were prepared with different kinds and molecular weight of polyols. IR spectroscopy was used to check the end of polymerization reaction and characterization of polymer. The study was carried out by increasing the waterproof of various coating agents through variations of soft segments. We introduced laser-scattering equipment, Brookfield digital viscometer, JC2000C instrument, scanning electron microscope (SEM), and atomic force microscope (AFM) to investigate the particle size, viscosity, contact angle, and morphology of the coated fabric. In short, results displayed waterproof as follows: 3146~8200 mm H2O (IPDI = 30 %) in various polyols and 5421~8748 mm H2O (R = 1.6) of different molecular weight of poly(butylene adipate) (PBA). The higher water resistance belonged to PTMG-WBPU and WBPU-1000, respectively. Experimental results indicated that water resistance may be controlled by not only the types of soft segments, but also the molecular weight.

The properties of materials are largely determined by the microstructures and components of materials. The design of layered double hydroxide (LDH) based composites has garnered much interest as a way of fabricating novel multiscale architectures with tunable micro/nanostructures and chemical compositions. The present study aims at exploiting the Zn–Al composites for controlled synthesis of multi-scale structures and multi-component materials. Firstly, microscaled Al2O3 fibers are successfully fabricated via a simple, convenient, and cost-effective biotemplate method employing paper fibers as bio-templates. Then, the multi-scale architectures are designed by an in situ growth method, which involves direct growth of nanoscaled LDH platelets on the surfaces of Al2O3 fibers. Finally, the multi-component LDH based materials are prepared based on the controlled crystal growth of LDHs and ZnO. The microstructure, morphology, and textural properties of the as-prepared samples are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption/desorption. The experimental results show that the longer reaction times are favorable for the crystal growth of LDHs, and the higher hydrothermal temperatures are favorable for the formation of ZnO. This study shows that the design of multi-scale structures and multi-components Zn–Al composites can be extended for the preparation of other hierarchical LDH based materials with controlled morphological and tunable chemical compositions for separation, catalysis, adsorption, sensor, and optical applications.

•Hierarchically structured Mg–Al composites were successfully prepared.•Multiscale architectures were fabricated by improved biotemplate method.•Crystal growth of LDHs was strongly dependent on urea content.•The biomorphic composites are quite effective in BSA adsorption.In this paper, hierarchically porous LDHs/Al2O3 composites are successfully fabricated in a large scale by combining the biological template method (for morph-Al2O3) and hydrothermal method (for LDHs). The morph-Al2O3 with fiber structure is prepared by template-directed synthesis employing cotton fibers as bio-templates. Then, the 2D LDHs nanoplatelets are fabricated into complex 3D architectures by in situ growth on surface Al2O3 fibers in a closed hydrothermal system, forming the hierarchical macro-mesoporous LDHs/Al2O3 composites. The N2 sorption analyses confirmed that the calcined composites have uniform mesochannels (7.58 nm), high surface area (292.51 m2/g), and large pore volume (0.55 cm3/g). Meanwhile, the macroporous structures fabricated by LDH nanoplatelets can be directly observed in morphology analysis. In LDHs crystal growth process, the controlling mechanism was discussed in detail according to the crystal growth kinetics and thermodynamics. As compared to calcined LDHs particles, the calcined composites have excellent adsorption properties. The efficient adsorption (90.27%) of BSA from solution suggests that the composites are potentially useful in BSA bioseparation.Graphical abstract

•Fabrication of hierarchical BSA/ZnO hybrids by a self-assembly route.•The hybrids have a nearly monodisperse flowerlike texture.•The hybrids exhibited enhanced UV absorbance.Here we present a novel and simple method to fabricate hierarchical nanostructured bovine serum albumin (BSA)/ZnO hybrids based on the assembly of biological proteins and metal ions. The as-fabricated hybrids that are comprised of individual microrods possess self-organized flowerlike architectures with sizes ranging from 400 to 600 mm. The UV–vis spectra depicted that the absorption peak of BSA/ZnO hybrids was blue-shifted as compared to the bare ZnO nanorods due to the enhanced surface effects. This new protein–inorganic hybrid and the design strategy are expected to be applicable to the synthesis of other 3D biohybrid materials for potential applications in biocatalysis, biosensors and nonlinear-optical devices.

Effects of ultrasonic irradiation on the catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation were studied. XRD, TEM and TPDA were used to characterize the catalysts. From the results of XRD, the structure of ZSM-5 was not destroyed by the ultrasound. Ultrasound promoted the dispersion of Pt on the surface of the carrier during impregnation and decreased the size of Pt particles. Compared with the catalyst prepared by conventional impregnation, the supported catalyst prepared by ultrasonic irradiation showed better catalytic activity in propane dehydrogenation.

•The mechanism involves the growth of TiO2 and simultaneous redeposition of silica.•The redeposited mSiO2 provides a physical barrier to prevent Pt NPs from sintering.•The hierarchical TiO2 nanostructure shows an obvious co-catalysis effect.A novel hierarchical TiO2@Pt@mSiO2 hollow nanocatalyst with enhanced thermal stability has been synthesized successfully. The formation procedure involves a facile synthesis of SiO2@TiO2@Pt nanospheres and a subsequent solvothermal process. During the hydrothermal process, original TiO2 layer was transformed into a hierarchical nanostructure and, meanwhile, etch-released silica species redeposited on the surface of the in-situ grown TiO2 nanoplatelets. In the catalytic system, the in-situ grown TiO2 nanoplatelets were buried in the redeposited mSiO2 layers and the Pt NPs dispersed uniformly between TiO2 nanoplatelets and mSiO2 layers. Importantly, the redeposited mSiO2 layer provides a physical barrier to prevent Pt NPs from sintering up to 550 °C and the hierarchical TiO2 nanostructure shows an obvious co-catalysis effect in the reduction of 4-NP. Besides, the mSiO2 layer could also control the rapid crystallization process of TiO2 nanoplatelets effectively. In the high temperature reaction of propane dehydrogenation, HHN exhibits a lower deactivation parameter, indicating the excellent thermal stability.

A novel binary-metal-oxide-coated hollow microspheres-titanium dioxide-zirconium dioxide-coated Au nanocatalyst was prepared via a facile hydrothermal synthesis method. SEM, TEM, EDX, FTIR, XRD, UV–vis and XPS analyses were employed to characterize the composition, structure, and morphology of ZrO2–TiO2 hollow spheres. The size of Au nanoparticles was found to be 3–5 nm in diameter before being immobilized on the aforementioned mesoporous ZrO2–TiO2 layer and used as catalysts in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. Compared with TiO2/Au and ZrO2/Au, ZrO2–TiO2/Au NPs showed a higher catalytic activity because of due to mixed oxide synergistic effect. Besides, the sample gets the highest thermal stability and reactivity at 550 °C, after calcining the hollow ZT/Au NPs at 550 °C, 300 °C and room temperature, respectively. Finally, a possible reaction mechanism was also proposed to explain the reduction of 4-nitrophenol to 4-aminophenol over ZrO2–TiO2/Au catalyst.Schematic illustration for the preparation of a novel ZT/Au hollow catalyst.