Yingying Zheng

The structural and biological properties of hydroxyapatite-modified titanate nanowire scaffolds.

Hydroxyapatite-modified titanate nanowire scaffolds as alternative materials for tissue engineering have been developed via a titanate nanowire matrix assisted electrochemical deposition method. The macroporous titanate nanowire matrix on Ti metal was fabricated by a hydrothermal method, and then followed by an electrochemical synthesis of hydroxyapatite nanoparticles on titanate nanowire. The incorporation of titanate nanowire matrix with high oriented hydroxyapatite nanoparticles generates hierarchical scaffolds with highly osteogenic, structural integrity and excellent mechanical performance. As-prepared porous three dimensional interconnected hydroxyapatite-modified titanate nanowire scaffolds, mimicking the natures extracellular matrix, could provide a suitable microenvironment for tissue cell ingrowth and differentiation. The ceramic titanate nanowire core with HA nanoparticle sheath structure displays superhydrophilicity, which facilitates the cell attachment and proliferation, and induces the in vitro tissue-engineered bone. Human osteoblast-like MG63 cells were cultured on the hydroxyapatite-modified titanate nanowire scaffolds, and the results showed that the scaffolds highly promote the bioactivity, osteoconductivity and osteoblast differentiation.

Polysaccharide-based nanocomposites and their applications

Polysaccharide nanocomposites have become increasingly important materials over the past decade. Polysaccharides offer a green alternative to synthetic polymers in the preparation of soft nanomaterials. They have also been used in composites with hard nanomaterials, such as metal nanoparticles and carbon-based nanomaterials. This mini review describes methods for polysaccharide nanocomposite preparation and reviews the various types and diverse applications for these novel materials.

Controlled synthesis and self-assembly of dendrite patterns of Fe3O4 nanoparticles.

A method for the growth and self-assembly of Fe(3)O(4) nanoparticles that is template assisted, as well as gas diffusion and surface tension controlled, has been developed at room temperature. Well-defined dendrite patterns of Fe(3)O(4) nanoparticles were obtained upon ion (Fe(3+)/Fe(2+)) entrapment in a polyethylene glycol solution followed by NH(3) gas exposure on the surface of an aqueous solution on the glass substrate. During the formation of Fe(3)O(4) nanoparticles, the diffusion of volatile NH(3) limits the hydrolysis rate of the molecular precursor and catalyzes slow formation. The template and surface tension also provided significant driving forces to promote the formation of dendrite patterns and influence the nature of the pattern. The Fe(3+)/Fe(2+) concentration was varied in order to see the affects on the template molecular weight. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and SQUID measurements were used to characterize the final product. The derived patterned structure can be tailored by a simple combination of the physical and chemical procedure, which provides a new opportunity for obtaining a controllable pattern of nanoparticles.

Uniform nanoparticle coating of cellulose fibers during wet electrospinning

This work outlines a newly developed method that allows electrospun cellulose fibers to be coated with nanoparticles during dry-jet wet electrospinning. Cellulose fibers were wet electrospun from a room temperature ionic liquid solvent into a coagulation bath containing an aqueous suspension of magnesium hydroxide nanoparticles to prepare composites of nanofibers coated with functional nanoparticles. Flame retardant cellulose–magnesium hydroxide coated composite fibers were prepared to demonstrate this novel electrospinning method. The placement of the nanoparticles exclusively on the surface of the cellulose fibers dramatically impacted the functionality of the fibers. Electrospun cellulose fibers exhibited an onset of combustion in air at 239 °C and a maximum mass loss at 302 °C. Cellulose fibers with Mg(OH)2 nanoparticles ( 100 nm avg. diameter) were used, the onset of combustion was 185 °C and the maximum mass loss was at 216 °C when nanoparticles were inside the fibers, and the onset of combustion was 263 °C and the maximum mass loss was at 317 °C for Mg(OH)2 nanoparticle coated cellulose fibers. Simple flame tests showed a similar trend, with nanoparticle-coated fibers being fire resistant and fibers with nanoparticles inside burned rapidly upon exposure to an open flame.

Can natural fibers be a silver bullet? Antibacterial cellulose fibers through the covalent bonding of silver nanoparticles to electrospun fibers

Natural cotton was dissolved in a room-temperature ionic liquid 1-ethyl-3-methyl acetate and wet-jet electrospun to obtain nanoscale cotton fibers with a substantially reduced diameter-and therefore an increased surface area-relative to natural cotton fibers. The resulting nano-cotton fibers were esterified with trityl-3-mercaptopropionic acid, which after selective de-tritylation afforded nano-cotton fibers containing reactive thiol functionality. Silver nanoparticles that were covalently attached to these sulfhydryl groups were assembled next. The microstructure of the resulting nanocomposite was characterized, and the antibacterial activity of the resulting nano-cotton Ag-nanoparticle composite was also studied. This nanocomposite showed significant activity against both Gram-negative and Gram-positive bacteria.

The visible light hydrogen production of the Z-Scheme Ag 3 PO 4 /Ag/g-C 3 N 4 nanosheets composites

The Z-Scheme Ag3PO4/Ag/g-C3N4 nanosheets composites are synthesised via simple annealing and anion-exchange precipitation method. The obtained samples are characterized by SEM, XRD, TEM, XPS, UV–Vis and PL, which imply that the Z-Scheme Ag3PO4/Ag/g-C3N4 structure has been prepared successfully. The photocatalytic activity of the as-prepared Ag3PO4/Ag/g-C3N4 nanosheets composites displays a remarkable enhancement after the Ag3PO4/Ag nanoparticles being introduced by the hydrogen production under visible light. Further, the Z-Scheme structure of the sample and the lamellar structure of the C3N4 are considered as the main reasons for the enhancement.

The visible light photocatalytic activity enhancement of cotton cellulose nanofibers/In2S3/Ag–CdS nanocomposites

Cotton cellulose nanofibers (CCNFs)/In2S3/Ag–CdS nanocomposites were prepared by a typical technical route which combined electrospinning and a chemical method. The results showed that the CCNFs/In2S3/Ag–CdS nanocomposites had a remarkable visible light photocatalytic property and cycling stability, which displayed a significant enhancement compared with that of pure In2S3. Through analysis, this enhancement could be mainly attributed to the multilevel structure of the composites.

The formation and UV-blocking property of flower-like ZnO nanorod on electrospun natural cotton cellulose nanofibers

We report a simple and effective route to fabricate branched hierarchical flower-like nanostructures of ZnO on natural cotton cellulose fiber by combining electrospinning and the low-temperature hydrothermal growth technique. First, natural cotton cellulose nanofibers were prepared by electrospinning cotton cellulose /LiCl/DMAc solution. The electrospun cotton cellulose nanofibers served as flexible substrate, on which the branched, highly uniform, and dense flower-like ZnO were hydrothermally grown. The as-prepared cotton cellulose/ZnO nanocomposite fibers were characterized by SEM, HRTEM, EDS, TG, and UV-vis spectrophotometry. The modified cotton cellulose nanocomposite fibers were not only exhibiting dispersed uniformly, but also rendered excellent protection against UV radiation because of the incorporation of flower-like ZnO nanostructures. Therefore, the as-prepared nanocomposite fibers demonstrate a significant performance in ultraviolet protection and provide a potential application for ultraviolet detection.

p–n junction induced electron injection type transparent photosensitive film of Cu2O/carbon quantum dots/ZnO

An electron injection type transparent photosensitive Cu2O/carbon quantum dot (C QD)/ZnO p-n junction film was prepared by a simple route in which, successively, the ZnO film was prepared by a sputtering process, the C QDs and Cu2O were prepared by hydrothermal synthetic and chemical methods, then the C QDs and Cu2O were introduced onto the surface of the ZnO film. The results indicated that the C QDs and Cu2O were well combined with the ZnO film. The transparency and photosensitivity of this film were investigated, and exhibited an obvious photosensitive enhancement compared with those of the unmodified film. Through analysis, this enhancement of the photoconductivity could be attributed to the remarkable Cu2O/ZnO p-n junction and C QDs with unique up-converted photoluminescence.

The cotton cellulose nanofibers framework of Z-Scheme ZnO/Ag 3 PO 4 heterojunction for visible-light photocatalysis

The cotton cellulose nanofibers framework of Z-Scheme ZnO/Ag3PO4 heterojunction has been successfully fabricated by a simple route of the electrospun-hydrothermal method. The photocatalytic activity of the as-prepared cotton cellulose nanofibers framework of Z-Scheme ZnO/Ag3PO4 heterojunction exhibits significant enhancement after the Ag3PO4 being introduced by the degradation of methylene blue (MB) under visible light irradiation. Furthermore, the high dispersibility of the CCNFs, high visible light absorption and photon-generated carriers separation of Z-Scheme ZnO/Ag3PO4 heterostructure are considered as the main reasons for the enhancement.