Yuanqing Gu

Hierarchical, titania-coated, carbon nanofibrous material derived from a natural cellulosic substance.

Hierarchical, titania-coated, nanofibrous, carbon hybrid materials were fabricated by employing natural cellulosic substances (commercial filter paper) as a scaffold and carbon precursor. Ultrathin titania films were firstly deposited by means of a surface sol-gel process to coat each nanofiber in the filter paper, and successive calcination treatment under nitrogen atmosphere yielded the titania-carbon composite possessing the hierarchical morphologies and structures of the initial paper. The ultrathin titania coating hindered the coalescence effect of the carbon species that formed during the carbonization process of cellulose, and the original cellulose nanofibers were converted into porous carbon nanofibers (diameters from tens to hundreds of nanometers, with 3-6 nm pores) that were coated with uniform anatase titania thin films (thickness approximately 12 nm, composed of anatase nanocrystals with sizes of approximately 4.5 nm). This titania-coated, nanofibrous, carbon material possesses a specific surface area of 404 m(2) g(-1), which is two orders of magnitude higher than the titania-cellulose hybrid prepared by atomic layer deposition of titania on the cellulose fibers of filter paper. The photocatalytic activity of the titania-carbon composite was evaluated by the improved photodegradation efficiency of different dyes in aqueous solutions under high-pressure, fluorescent mercury-lamp irradiation, as well as the effective photoreduction performance of silver cations to silver nanoparticles with ultraviolet irradiation.

Fabrication of natural cellulose substance derived hierarchical polymeric materials

Hierarchical porous metal oxide/polymer hybrid and polymer materials were fabricated by replication of natural cellulosic substances and successive removal of the template cellulose components using a solution dissolving method under mild conditions. Commercial filter paper was employed as the template, metal oxide/polymer (titania/polyvinyl alcohol) composite ultrathin films were deposited by layer-by-layer assembly to replicate its structures with nanometer precisions, and the cellulose components were thereafter removed by treating with sodium hydroxide/urea solution. The resulting hierarchical porous titania/PVA composite sheets possessed the initial structures and morphologies of the template cellulosic substance, and also inherited the corresponding physical properties such as flexibility and swelling property in various solvents. Pure hierarchical PVA material was successively obtained by removing the titania component from the titania/PVA hybrid sheets with acidic treatment. The current research breaks the limitation caused by calcination employed in general template syntheses to burn off the template component, opening a pathway for the design and preparation of bio-inspired polymeric and organic materials.

Luminescent cellulose sheet fabricated by facile self-assembly of cadmium selenide nanoparticles on cellulose nanofibres

A hierarchical luminescent cellulose sheet was fabricated viaself-assembly of cadmium selenide (CdSe) nanoparticles capped with trioctylphosphine oxide (TOPO) and 1-hexadecylamine (HDA) onto ultrathin titania film pre-coated cellulose nanofibres of bulk natural cellulose substance (common commercial filter paper). Each cellulose nanofibre of the filter paper was firstly coated with nanometre-thick titania film by means of the surface sol–gel process, followed by alternative deposition of self-assembled layers of stearic acid (SA) and TOPO/HDA capped CdSe nanoparticles, giving a filter paper/titania/SA/(CdSe/SA) composite luminescent sheet possessing stable and well-defined green fluorescence. SEM and TEM observations showed that the resulting luminescent sheet retained the hierarchical structures and morphologies of the initial cellulose substance; meanwhile, the CdSe nanoparticles were anchored on the nanofibre surfaces within SA thin layers through the hydrophobic interaction between the alkyl chains of the surface ligands of CdSe nanoparticles and SA molecules. UV-vis and photoluminescence spectra indicated that the resulting luminescent sheet showed similar characteristic absorption and emission properties as those of the original CdSe nanoparticles. The current approach provides a facile shortcut to fabricate bulk luminescent materials that inherit the mechanical behaviour of cellulose substances and simultaneously possess designed luminescent properties.

Precise Size Control over Ultrafine Rutile Titania Nanocrystallites in Hierarchical Nanotubular Silica/Titania Hybrids with Efficient Photocatalytic Activity

Hierarchical-structured nanotubular silica/titania hybrids incorporated with particle-size-controllable ultrafine rutile titania nanocrystallites were realized by deposition of ultrathin titania sandwiched silica gel films onto each nanofiber of natural cellulose substances (e.g., common commercial filter paper) and subsequent flame burning in air. The rapid flame burning transforms the initially amorphous titania into rutile phase titania, and the silica gel films suppress the crystallite growth of rutile titania, thereby achieving nano-precise size regulation of ultrafine rutile titania nanocrystallites densely embedded in the silica films of the nanotubes. The average diameters of these nanocrystallites are adjustable in a range of approximately 3.3-16.0 nm by a crystallite size increment rate of about 2.4 nm per titania deposition cycle. The silica films transfer the electrons activated by crystalline titania and generate catalytic reactive species at the outer surface. The size-tuned ultrafine rutile titania nanocrystallites distributed in the unique hierarchical networks significantly improve the photocatalytic performance of the rutile phase titania, thereby enabling a highly efficient photocatalytic degradation of the methylene blue dye under ultraviolet light irradiation, which is even superior to the pure anatase-titania-based materials. The facile stepwise size control of the rutile titania crystallites described here opens an effective pathway for the design and preparation of fine-nanostructured rutile phase titania materials to explore potential applications.

Superparamagnetic hierarchical material fabricated by protein molecule assembly on natural cellulose nanofibres

Bio-inspired superparamagnetic hierarchical material which possesses significant thermal stability and superparamagnetic property was fabricated by core reconstruction of silica thin film coated ferritin molecules that were immobilized on the surface of natural cellulose nanofibres of common commercial filter paper.

Functional polymeric hybrid nanotubular materials derived from natural cellulose substances

Template synthesis is regarded as an effective pathway to replicate the unique structures and morphologies of natural substances with guest substrates to introduce designed functions into artificial materials, but it is generally limited to inorganic materials syntheses due to the severe calcination treatment to remove the template during the fabrication process. Here, a series of polymeric hybrid nanotubular materials were fabricated employing natural cellulosic substances as templates via versatile alternative layer-by-layer deposition strategies and successive removal of cellulose component by a solution dissolving process under mild conditions. Thin layers of various polyelectrolytes and polysaccharide such as heparin were deposited onto titania thin film pre-coated cellulose nanofibers of natural cellulose substance (e.g. commercial filter paper) through electrostatic interaction and covalent links, respectively. The cellulose substance template was dissolved away by low-temperature sodium hydroxide/urea solution treatment, resulting in corresponding polymeric hybrid nanotubular materials. In spite of the employed raw polymers and deposition strategies, all the obtained nanotubular products successfully memorized the original structures and morphologies of the natural cellulose template. Importantly, since a mild chemical dissolution process was employed instead of calcination to selectively remove the template cellulose substrate, the final polymeric hybrid products were left undamaged, and furthermore, brought their unique instinct properties such as significant anticoagulative properties originated from heparin. Our present research broadens the availability of raw materials for synthesizing bio-inspired products, and provides such products with advanced bio-organic functions.

Hierarchical fibrous titanium metal derived from cellulose substance

We have developed an approach to duplicate the structure of a natural cellulose substance (commercial laboratory filter paper) with titanium metal. A nanometer precise anatase titania replica of filter paper was converted into alpha phase (hcp) titanium by a calciothermic reduction process using calcium chloride as a molten salt. The resulting fibrous titanium metal consists of hierarchical structured fine titanium fibres as duplicates of the cellulose fibres of the initial filter paper.

Reversible self-assembly of ferritin molecules for fabrication of size controlled microspheres and microrods

The reversible self-assembly of ferritin molecules into stable size-tailored ferritin microspheres was achieved in 1-octanol, and microrods consisting of ferritin microspheres were prepared by the porous polycarbonate membrane templated deposition of these ferritin microspheres.