Jijiang Fu

Fabrication, modification, and biomedical applications of anodized TiO2 nanotube arrays

Titanium dioxide (TiO2) nanotubes have attracted increasing attention due to their outstanding properties and potential applications in photocatalysis, dye-sensitized solar cells, and biomedical devices. In this paper, recent research progress on TiO2 nanotube arrays (NTAs) produced by anodic oxidation of Ti in fluoride-containing electrolytes is reviewed with emphasis on the modification methods and biomedical applications. The fabrication protocol and growth mechanism are first discussed and common modification methods used to improve the optical, electronic, and biomedical properties of TiO2 NTAs are reviewed. Photo/electro-chemical biosensors based on TiO2 NTAs dedicated to the detection of glucose, hydrogen peroxide, and other biomolecules are described and recent examples of using TiO2 NTAs to improve the cellular response in vitro and accelerate osseointegration in vivo are provided. The incorporation and delivery of inorganic bioactive agents such as Ag, Sr, and Zn to achieve antibacterial and/or osteogenesis inducing ability are described and finally, the outlook and future development of TiO2 nanotubes pertaining to biomedical devices are briefly discussed.

One-step growth and field emission properties of quasialigned TiO2 nanowire/carbon nanocone core-shell nanostructure arrays on Ti substrates

Quasialigned nanoarrays consisting of TiO2 nanowire cores and carbon nanocone shells have been produced directly on titanium foils via a simple one-step thermal reaction under acetone vapor at 850°C. The nanowire cores are single-crystalline rutile TiO2 with diameters of 15–20nm and the conical carbon shells are amorphous with gradually decreasing thicknesses from 200–300nm at the bases to 5–10nm at the tips. Disparity of precipitation and etching of carbon shell give rise to the conical shape. Such TiO2∕C nanocone arrays on a conducting substrate are a new member of the conical nanostructures and promising field electron emitters.

Coaxial PANI/TiN/PANI nanotube arrays for high-performance supercapacitor electrodes

Coaxial PANI/TiN/PANI nanotube arrays prepared by electrochemical polymerization of PANI on nanoporous TiN nanotube arrays exhibit a high specific capacitance of 242 mF cm(-2), excellent rate capability with the capacitance remaining at 69% when the current density is increased 50 times from 0.2 to 10 mA cm(-2), and a long cycling life with less than 0.005% decay per cycle.

Recyclable and high-sensitivity electrochemical biosensing platform composed of carbon-doped TiO2 nanotube arrays.

Electrode fouling and passivation are the main reasons for attenuated signals as well as reduced sensitivity and selectivity over time in electrochemical analysis. We report here a refreshable electrode composed of carbon-doped TiO(2) nanotube arrays (C-doped TiO(2)-NTAs), which not only has excellent electrochemical activity for simultaneous determination of 5-hydroxytryptamine and ascorbic acid but also can be easily photocatalytically refreshed to maintain the high selectivity and sensitivity. The C-doped TiO(2)-NTAs are fabricated by rapid annealing of as-anodized TiO(2)-NTAs in argon. The residual ethylene glycol absorbed on the nanotube wall acts as the carbon source and no foreign carbon precursor is thus needed. The morphology, structure, and composition the C-doped TiO(2)-NTAs are determined, and the corresponding doping mechanism is investigated by thermal analysis and in situ mass spectroscopy. Because of the high photocatalytic activity of the C-doped TiO(2)-NTAs electrode, the electrode surface can be readily regenerated by ultraviolet or visible light irradiation. This photoassisted regenerating technique does not damage the electrode microstructure while rendering high reproducibility and stability.

Strontium (Sr) and silver (Ag) loaded nanotubular structures with combined osteoinductive and antimicrobial activities

UNLABELLED Two frequent problems are associated with the titanium surfaces of bone/dental implants: lack of native tissue integration and associated infection. These problems have prompted a significant body of research regarding the modification of these surfaces. The present study describes a hydrothermal treatment for the fabrication of strontium (Sr) and silver (Ag) loaded nanotubular structures with different tube diameters on titanium surfaces. The Sr loading from a Sr(OH)2 solution was regulated by the size of the inner diameter of the titanium nanotubes (NT) (30nm or 80nm, formed at 10V or 40V, respectively). The quantity of Ag was adjusted by immersing the samples in 1.5 or 2.0M AgNO3 solutions. Sr and Ag were released in a controllable and prolonged matter from the NT-Ag.Sr samples, with negligible cytotoxicity. Prominent antibacterial activity was observed due to the release of Ag. Sr incorporation enhanced the initial cell adhesion, migration, and proliferation of preosteoblast MC3T3-E1 cells. Sr release also up-regulated the expression of osteogenic genes and induced mineralization, as suggested by the presence of more mineralized calcium nodules in cells cultured on NT-Ag.Sr surfaces. In vivo experiments showed that the Sr-loaded samples accelerated the formation of new bone in both osteoporosis and bone defect models, as confirmed by X-ray, Micro-CT evaluation, and histomorphometric analysis of rats implanted with NT-Ag.Sr samples. The antibacterial activity and outstanding osteogenic properties of NT-Ag.Sr samples highlight their excellent potential for use in clinical applications. STATEMENT OF SIGNIFICANCE Two frequent problems associated with Ti surfaces, widely used in orthopedic and dental arenas, are their lack of native tissue integration and risk of infection. We describe a novel approach for the fabrication of strontium (Sr) and silver (Ag) loaded nanotubular structures on titanium surfaces. A relevant aspect of this work is the demonstration of long-lasting and controllable Ag release, leading to excellent antibacterial and anti-adherent properties against methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria such as Escherichia coli. The extended release of Sr accelerates the filling of bone defects by improving the repair of damaged cortical bone and increasing trabecular bone microarchitecture. Our results highlight the potential of Sr and Ag loaded nanotubular structures for use in clinical applications.

Enhanced osseointegration and antibacterial action of zinc-loaded titania-nanotube-coated titanium substrates: in vitro and in vivo studies.

Poor osseointegration and infection resulting from implants are serious medical issues, and it is not straightforward to manufacture implants that can simultaneously address both of these problems. In this study, we produced coatings containing titania nanotubes (TiO2 -NTs) incorporated with zinc (NT-Zn) on Ti substrates by anodization and hydrothermal treatment. The zinc content was controlled by varying the duration of the hydrothermal treatment. The NT-Zn implants not only exhibited improved bone formation (shown by both in vitro and in vivo studies), which enhances osseointegration between bone and implant, but also inhibited growth of bacteria. The cytotoxicity of locally high concentrations of zinc in the NT-Zn3h specimens observed during in vitro studies was mitigated by the effects of dilution in vivo.

Temperature dependent photoluminescence from ZnO nanowires and nanosheets on brass substrate

The temperature-dependent optical properties of ZnO nanosheets and nanowires fabricated on conductive brass substrates with different surface-to-volume ratios and morphologies are investigated. The near band edge and deep-level emission mechanisms are studied. The blueshifted donor bound exciton D 0X peak and enhanced deep-level emission in the low-temperature photoluminescence spectrum of the nanosheets are due to the large surface-to-volume ratios. Although D 0X is the dominant emission from both the nanowires and nanosheets at low temperature, the room-temperature spectra are dominated by D 0X (nanowires) and first order longitudinal optical phonon replica of free exciton (nanosheets). The decay in the D 0X peak intensity stems from the thermal dissociation of D 0X to free exciton.

Controlled fabrication of core-shell TiO2/C and TiC/C nanofibers on Ti foils and their field-emission properties.

Core-shell TiO(2)/C and TiC/C nanofibers are fabricated in situ on Ti and Al ion-implanted Ti substrates by a thermochemical reaction in acetone and the growth mechanism is described. Implantation of Al into Ti leads to in situ growth of TiC/C in lieu of TiO(2)/C nanofibers. This is because Al has a higher affinity to oxygen than Ti and Ti reacts preferentially with C to form TiC. The Ti foil serves as both the Ti source and substrate for the core-shell TiO(2)/C and TiC/C NFs to ensure strong bonding and small contact resistance between the Ti substrate and the core-shell field emitters. The core-shell TiC/C and TiO(2)/C nanofibers have similar morphology and structure, but the TiC/C nanofibers possess better field emission properties with a turn on field (E(to)) of 2.2 V/μm compared to an E(to) of 3.2 V/μm measured from the TiO(2)/C nanofibers. The enhanced field-emission property of the TiC/C nanofibers is attributed to the high electrical and thermal conductivity of the TiC inner core, which provides a more effective electron transfer pathway between the cathode and C shell emitters.

In situ growth of aligned CdS nanowire arrays on Cd foil and their optical and electron field emission properties

Aligned CdS nanowire arrays have been fabricated directly on a Cd foil via a simple solvothermal method. The metal Cd foil serves as both the Cd source and substrate during fabrication of the aligned CdS nanowire arrays. The morphology, structure, and composition of the samples are characterized by x-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy, and selected-area electron diffraction, and the results reveal the formation of aligned single-crystalline CdS nanowires with uniform diameters of 20–40 nm. The photoluminescence and Raman spectra disclose the optical properties of the products and the possible growth mechanism is suggested. The electron field emission properties are also investigated and analyzed. The screening effect is observed to play a vital role in the electron field emission properties due to the coalescent ends of the nanowires. The simple synthesis methodology in conjunction with the good field emissio...

Large and porous carbon sheets derived from water hyacinth for high-performance supercapacitors

To elevate the properties of carbon based electrical double-layer capacitors (EDLCs), sheet-like carbon with high porosity is desirable due to enhanced electron transport efficiency and good electrolyte accessibility. In this paper, large porous carbon sheets are fabricated via an acid treatment, pyrolytic carbonization, and alkali activation of water hyacinth (WH) biomass. The WH-derived carbon sheets with a large uniform area have a large specific surface of 1308 m2 g−1 and desirable pore volume of 0.84 cm3 g−1, resulting from the template of the original thin cell walls and large intercellular space, which deliver a high specific capacitance of 273 F g−1 at a current density of 1 A g−1, excellent capacity retention of 75% when the current density is increased from 1 to 50 A g−1, and superior cyclic stability over 10 000 cycles in 6 M KOH. The specific capacitance of the assembled symmetric capacitor based on the large and porous carbon sheets reaches a remarkable 81.5 F g−1 and an energy density of 7.24 W h kg−1 can be achieved at a current density of 1 A g−1. These outstanding electrochemical properties suggest that the WH-derived porous carbon sheets have commercial potential in high-performance supercapacitors and the simple and economical process utilizing the WH waste biomass is environmentally friendly.