Yanfen Ding

Immobilization of TiO2 nanoparticles in polymeric substrates by chemical bonding for multi-cycle photodegradation of organic pollutants.

Nano titanium dioxide (TiO(2)) photocatalyst is generally immobilized onto the matrix through the physical absorption, hydrogen bonding or chemical bonding, which is utilized for the application of wastewater treatment. In this research, TiO(2) nanoparticles were immobilized in polyvinyl alcohol (PVA) matrix via solution-casting combined with heat-treatment method. Structure characterization indicated that Ti-O-C chemical bond formed via dehydration reaction between TiO(2) and PVA during the heat treatment process, and TiO(2) nanoparticles had been chemically immobilized in PVA matrix. Photodegradation results of methyl orange (MO) showed that the film with 10 wt% TiO(2) and treated at 140°C for 2h exhibited a remarkable ultraviolet (UV) photocatalytic activity, approximately close to the TiO(2) slurry system. This was mainly attributed to the fixation effect by Ti-O-C chemical bonds, which was indirectly confirmed by the slight loss of TiO(2) photocatalysts even after 25-cycle use. In addition, the good swelling ability of PVA matrix provided the MO molecules with more opportunities to fully contact with TiO(2), thus benefited the photocatalysis. This route to chemically immobilize TiO(2) nanoparticles is simple and cheap to prepare polymer/TiO(2) hybrid materials with high photocatalytic activity for multi-cycle use, which is of significance to the practical application of TiO(2) catalysts.

Highly Exfoliated Poly(Ethylene Terephthalate)/Clay Nanocomposites via Melt Compounding: Effects of Silane Grafting

The ammonium intercalated montmorillonite (A-MMT), especially acid treated montmorillonite (H-S-A-MMT), which experienced silane grafting treatment, exhibited highly exfoliation state in poly(ethylene terephthalate) (PET) matrix. It can be explained that the shear stress was transferred effectively from molten polymer to clay layers during melting processing due to the enhanced polymer-clay interaction by the grafted silane, leading to the slippage and peeling of clay sheets. Furthermore, the equilibrium melting point reduction of highly exfoliated nanocomposite calculated by the Hoffman-Weeks formula exhibited great miscibility between clay and polymer, which was proved by the Nishi-Wang equation.

The Effect of Encapsulation of Nano Zinc Oxide with Silica on the UV Resistance of Polypropylene

The objective of this study is to improve the performances of the ceramic UV stabilizers in polymer nanocomposites. Silica coated ZnO nanoparticles were prepared and melt blended into polypropylene (PP) matrix in order to introduce an inert silica shell between the ZnO and polymer chains as an isolation layer and protect this polymer against photodegradation. The UV resistance of the nanocomposites was evaluated by accelerated aging test. The results indicated that the photocatalytic activity of the ZnO particles was suppressed via encapsulating with silica. The coated ZnO could effectively improve the UV stability of the PP nanocomposites.

Transparent epoxy–ZnO/CdS nanocomposites with tunable UV and blue light-shielding capabilities

It is known that ultraviolet (UV) radiation is harmful to human health and affects the long-term stability of many organic materials. It has recently been discovered that blue radiation also poses a danger. In this study, epoxy–ZnO/CdS (EP–ZC) nanocomposites capable of shielding both UV and blue radiation were developed. First, ZnO/CdS nanoparticles were synthesized through the growth of CdS on prefabricated ZnO quantum dots (ZnO QDs). In contrast to ZnO QDs, which only absorb a portion of UV light, the ZnO/CdS nanoparticles exhibited strong absorption over the wavelength region extending from UV light to blue light. Further, their absorption-band range could be controlled by adjusting the Zn/Cd molar ratio. In situ polymerization was employed to prepare the EP–ZC nanocomposites, which were highly transparent at wavelength greater than 500 nm. It was found that the EP–ZC nanocomposites exhibited strong UV-shielding capability and could almost completely block UV light between 200–400 nm as well as more than 80% of the blue light between 400–450 nm when they contained 0.3 wt% ZnO/CdS nanoparticles. Finally, their optical transparency to visible light in the region beyond blue light was the same as that of pure epoxy due to the uniform dispersion of nanoparticles.

Isothermal crystallization of polypropylene/surface modified silica nanocomposites

In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica (SiO2-WD70) and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide immobilized silica (SiO2-WD70-DOPO) nanoparticles were prepared. Silica, SiO2-WD70 and SiO2-WD70-DOPO were incorporated into polypropylene (PP) by melt compounding. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized optical microscopy (POM) were employed to investigate the isothermal crystallization behavior of PP and PP/silica composites. The kinetic constant (kn), and half crystallization time (t1/2) were calculated by Avrami equation, while the surface free energy of folding was calculated by Lauritzen-Hoffman theory. The increased kn, decreased t1/2 and the surface free energy (σe) in the order of PP, PP/SiO2, PP/SiO2-WD70 and PP/SiO2-WD70-DOPO nanocomposites were attributed to the surface modification of silica. XRD indicated that SiO2-WD70-DOPO addition had no effect on PP crystal structure but accelerated the crystallization rate. POM determined that SiO2-WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.

Polymer dots grafted TiO2 nanohybrids as high performance visible light photocatalysts

As a new member of carbon dots (CDs), Polymer dots (PDs) prepared by hydrothermal treatment of polymers, usually consist of the carbon core and the connected partially degraded polymer chains. This type of CDs might possess aqueous solubility, non-toxicity, excellent stability against photo-bleaching and high visible light activity. In this research, PDs were prepared by a moderate hydrothermal treatment of polyvinyl alcohol, and PDs grafted TiO2 (PDs-TiO2) nanohybrids with TiOC bonds were prepared by a facile in-situ hydrothermal treatment of PDs and Ti (SO4)2. Under visible light irradiation, the PDs-TiO2 demonstrate excellent photocatalytic activity for methyl orange degradation, and the photocatalytic rate constant of PDs-TiO2 is 3.6 and 9.5 times higher than that of pure TiO2 and commercial P25, respectively. In addition, the PDs-TiO2 exhibit good recycle stability under UV-Vis light irradiation. The interfacial TiOC bonds and the π-conjugated structures in PDs-TiO2 can act as the pathways to quickly transfer the excited electrons between PDs and TiO2, therefore contribute to the excellent photocatalytic activity.

Low temperature synthesis and mechanism of finely dispersed nanorod rutile titanium dioxide

As a kind of one-dimensional (1D) nanostructured material, nanorod rutile titanium dioxide (TiO2) with high surface-to-volume ratio shows potential applications in UV-ray shielding, self-cleaning devices, energy conversion and storage. Well dispersed rod-shaped rutile was prepared by hydrolysis of TiCl4 with hydrochloric acid (HCl) solutions and FeCl3 at low temperature. The crystalline form and morphology were characterized by X-ray diffraction (XRD), Raman spectrum and transmission electron microscopy (TEM). The doping of iron was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. A series of experiments were conducted to figure out the effects of reaction conditions on the crystalline form and shape of the powders. The results showed that either change of acids (H2SO4 or HNO3) or varying of cations (NaCl or AlCl3) leaded to a mixed products or pure anatase. A possible mechanism was proposed to explain why the change of minerals or acids would make such a remarkable difference.

Facile fabrication of hybrid PA6-decorated TiO2 fabrics with excellent photocatalytic, anti-bacterial, UV light-shielding, and super hydrophobic properties

Self-cleaning fabrics decorated with titanium dioxide (TiO2) nanoparticles (NPs) have garnered worldwide attention due to their outstanding ultraviolet (UV) light-shielding, anti-bacterial properties and other characteristics. Numerous techniques to construct super-antiwetting surfaces have been investigated for both fundamental research and practical application. A facile and eco-friendly way by a combination of UV irradiation and ultrasonic bath method has been developed to prepare a novel self-cleaning hybrid polyamine 6/nano TiO2 (PA6/nano TiO2) fabric with superhydrophobic and durable photocatalytic properties. To evaluate the fabrics reusability, hybrid PA6/nano TiO2 fabrics were subjected to five consecutive cycles of the photocatalytic degradation of the methyl orange (MO) dye. The results indicated that TiO2 NPs were firmly fixed on the fiber surface. The UV-blocking and anti-microbial properties of these hybrid fabrics were also tested. For PA6 immobilized by commercial nano TiO2-P25 (P25-PA6) and PA6 immobilized by prepared visible-light photocatalyst PVAD-TiO2(PVAD-PA6) fabrics, the UV protection factors (UPFs) of the samples were 56 and 1123, respectively. The anti-microbial efficacies of the two samples were both 99%. The water contact angles were 151.7° and 154.6°, respectively, indicating surface superhydrophobicity. These results showed that this novel fabric has great potential for indoor environmental purification and outdoor protection applications.

Morphology control of rutile TiO2 with tunable bandgap by preformed β-FeOOH nanoparticles

Rutile TiO2 are widely used for applications of coatings, cosmetics, photoelectric devices and so on. However, effective control of well-defined morphology, size and composition of rutile TiO2 nanoparticles from agglomeration has always been a challenge. A new synthesis strategy was proposed to prepare rutile TiO2 with controllable morphology varied from flower-like structures to single-separated nanorods. The β-FeOOH nanoparticles were generated by the hydrolysis of FeCl3 solution and could prevent the aggregation of TiO2 nanocrystals at early stages of the reaction; thus, could control the morphology of rutile nanoparticles. The morphology of rutile TiO2 nanoparticles could be controllably regulated from flower-like structures to individually separated nanorods. Meanwhile, the preformed β-FeOOH also played a role of dopant. Fe ions were substitutionally doped into the bulk lattice of TiO2 nanocrystals and reduced the bandgap, which extended the solar radiation absorption range of rutile TiO2. The prepared TiO2 may be suitable for novel UV-blue light shielding agents and many other applications in photoelectric devices, photocatalysis, and so on due to its small size, unprecedented discrete rod-like structure and unique UV-vis light permeability.