Biao Gao

Freestanding Mesoporous VN/CNT Hybrid Electrodes for Flexible All-Solid-State Supercapacitors

High-performance all-solid-state supercapacitors (SCs) are fabricated based on thin, lightweight, and flexible freestanding MVNN/CNT hybrid electrodes. The device shows a high volume capacitance of 7.9 F/cm(3) , volume energy and power density of 0.54 mWh/cm(3) and 0.4 W/cm(3) at a current density of 0.025 A/cm(3) . By being highly flexible, environmentally friendly, and easily connectable in series and parallel, the all-solid-state SCs promise potential applications in portable/wearable electronics.

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.

Long-lasting in vivo and in vitro antibacterial ability of nanostructured titania coating incorporated with silver nanoparticles.

Although titanium (Ti) implants are widely used clinically, implant-associated bacterial infection is still one of the most serious complications in orthopedic surgery. Long-term antibacterial properties and the ability to inhibit biofilm formation are highly desirable to prevent implant associated infection. In this study, a controllable amount of silver (Ag) nanoparticles was incorporated into titanium oxide; or titanium, nanotubes (TiO₂ -NTs). The reliable release and long-term antibacterial function of Ag, in vivo and in vitro, and influence normal bone-implant integration from the Ag released from Ag-incorporated NTs in vivo have been studied to make them useable in clinical practice. In the current study, TiO₂ -NTs loaded with Ag (NT-Ag) exhibited strong antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA, ATCC43300) in vitro for 30 days, and the ability to penetrate the protein layer well. In addition, X-ray examination and 2-[(18)F]-fiuoro-2-deoxy-D-glucose positron emission tomography indicates that NT-Ag show extremely long antibacterial activity in vivo in a rat model. Furthermore, histomorphometric analysis demonstrated that satisfactory bio-integration can be expected. Our results indicate that NT-Ag has both simultaneous antimicrobial and excellent bio-integration properties, make it a promising therapeutic material for orthopedic application.

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.

Mesoporous TiO2 Nanocrystals/Graphene as an Efficient Sulfur Host Material for High-Performance Lithium–Sulfur Batteries

Rechargeable lithium-sulfur (Li-S) batteries are promising in high-energy storage due to the large specific energy density of about 2600 W h kg(-1). However, the low conductivity of sulfur and discharge products as well as polysulfide-shuttle effect between the cathode and anode hamper applications of Li-S batteries. Herein, we describe a novel and efficient S host material consisting of mesoporous TiO2 nanocrystals (NCs) fabricated in situ on reduced graphene oxide (rGO) for Li-S batteries. The TiO2@rGO hybrid can be loaded with 72 wt % sulfur. The strong chemisorption ability of the TiO2 NCs toward polysulfide combined with high electrical conductivity of rGO effectively localize the soluble polysulfide species within the cathode and facilitate electron and Li ions transport to/from the cathode materials. The sulfur-incorporated TiO2@rGO hybrid (S/TiO2@rGO) shows large capacities of 1116 and 917 mA h g(-1) at the current densities of 0.2 and 1 C (1 C = 1675 mA g(-1)) after 100 cycles, respectively. When the current density is increased 20 times from 0.2 to 4 C, 60% capacity is retained, thereby demonstrating good cycling stability and rate capability. The synergistic effects of TiO2 NCs toward effective chemisorption of polysulfides and conductive rGO with high electron mobility make a promising application of S/TiO2@rGO hybrid in high-performance Li-S batteries.

Multilayered paper-like electrodes composed of alternating stacked mesoporous Mo2N nanobelts and reduced graphene oxide for flexible all-solid-state supercapacitors

Flexible all-solid-state supercapacitors (SCs) have great potential in flexible and wearable electronics due to their safety, flexibility, high power density, and portability. The energy storage properties of SCs are determined mainly by their composition and conductivity as well as the configuration of the integrated electrode material. Herein, a freestanding multilayered film electrode consisting of alternating stacked mesoporous Mo2N nanobelts and rGO nanosheets (MMNNBs/rGO) is described. The electrode has a high mass loading of 95.6 wt% of the Mo2N active material and boasts high areal capacitances of 142 and 98 mF cm−2 at current densities of 1 and 150 mA cm−2, respectively. All-solid-state SCs fabricated by sandwiching two thin and flexible freestanding MMNNBs/rGO hybrid electrodes with a poly (vinyl alcohol) (PVA)/H3PO4/silicotungstic acid (SiWA) gel electrolyte show a high volumetric capacitance of 15.4 F cm−3 as well as energy and power densities of 1.05 mW h cm−3 and 0.035 W cm−3 at a current density of 0.1 A cm−3 based on the volume of the entire cell. After 4000 charging–discharging cycles, the flexible SC retains 85.7% initial capacitance, thus exhibiting good cycling stability. This study provides a versatile method for the fabrication of flexible and high-performance ceramic-based nanohybrid films for SCs, and has immense potential in flexible and wearable electronics.

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.

High-energy lithium-ion hybrid supercapacitors composed of hierarchical urchin-like WO3/C anodes and MOF-derived polyhedral hollow carbon cathodes

A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO3 (WO3/C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO3/C microspheres assembled by radially oriented WO3/C nanorods along the (001) plane enable effective Li+ insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li+ conductivity, electronic conductivity and structural robustness. The WO3/C structure shows a reversible specific capacity of 508 mA h g-1 at a 0.1 C rate (1 C = 696 mA h g-1) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g-1 at a current density of 0.2 A g-1. At a high current density of 6 A g-1, 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO3/C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg-1 at a power density of 173.6 W kg-1 and 88.3% of the capacity is retained at a current density of 5 A g-1 after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO3/C//MOF-NC render large potential in energy storage.