Li+ Pre‐Insertion Leads to Formation of Solid Electrolyte Interface on TiO2 Nanotubes That Enables High‐Performance Anodes for Sodium Ion Batteries

Recently, sodium ion batteries (SIBs) have been widely investigated as one of the most promising candidates for replacing lithium ion batteries (LIBs). For SIBs or LIBs, designing a stable and uniform solid electrolyte interphase (SEI) at the electrode–electrolyte interface is the key factor to provide high capacity, long‐term cycling, and high‐rate performance. In this paper, it is described how a remarkably enhanced SEI layer can be obtained on TiO₂ nanotube (TiO₂ NTs) arrays that allows for a strongly improved performance of sodium battery systems. Key is that a Li⁺ pre‐insertion in TiO₂ NTs can condition the SEI for Na⁺ replacement. SIBs constructed with Li‐pre‐inserted NTs deliver an exceptional Na⁺ cycling stability (e.g., 99.9 ± 0.1% capacity retention during 250 cycles at a current rate of 50 mA g^?1) and an excellent rate capability (e.g., 132 mA h g^?1 at a current rate of 1 A g^?1). The key factor in this outstanding performance is that Li‐pre‐insertion into TiO₂ NTs leads not only to an enhanced electronic conductivity in the tubes, but also expands the anatase lattice for facilitated subsequent Na⁺ cycling.     

Effect of biofouling on anodized and sol-gel treated titanium surfaces: a comparative study

Anodization and sol-gel treatments of titanium (Ti) were evaluated as biofilm control measures on surfaces exposed to seawater exposed to ultraviolet light. Anodized and sol-gel treated specimens were characterized using Raman spectroscopy to confirm the presence of TiO₂. The single anatase phase was observed at the anodized surfaces whereas the anatase/rutile mixed phase was detected on the sol-gel coated surfaces. After exposure of the specimens to seawater, biofilms were characterized by total viable counts, and epifluorescence and Raman microscopy. These techniques confirmed the reduction in biofilm formation on both the anodized and sol-gel coated Ti specimens compared to the untreated specimens. Biofilm control by anodization was found to be more effective than by sol-gel treatment of the specimens. The higher particle size and the inhomogeneity at the sol-gel coated surfaces produced less effective biofilm control.     

Enhanced osteoblast adhesion to drug-coated anodized nanotubular titanium surfaces

Current orthopedic implants have functional lifetimes of only 10-15 years due to a variety of reasons including infection, extensive inflammation, and overall poor osseointegration (or a lack of prolonged bonding of the implant to juxtaposed bone). To improve properties of titanium for orthopedic applications, this study anodized and subsequently coated titanium with drugs known to reduce infection (penicillin/streptomycin) and inflammation (dexamethasone) using simple physical adsorption and the deposition of such drugs from simulated body fluid (SBF). Results showed improved drug elution from anodized nanotubular titanium when drugs were coated in the presence of SBF for up to 3 days. For the first time, results also showed that the simple physical adsorption of both penicillin/streptomycin and dexamethasone on anodized nanotubular titanium improved osteoblast numbers after 2 days of culture compared to uncoated unanodized titanium. In addition, results showed that depositing such drugs in SBF on anodized titanium was a more efficient method to promote osteoblast numbers compared to physical adsorption for up to 2 days of culture. In addition, osteoblast numbers increased on anodized titanium coated with drugs in SBF for up to 2 days of culture compared to unanodized titanium. In summary, compared to unanodized titanium, this preliminary study provided unexpected evidence of greater osteoblast numbers on anodized titanium coated with either penicillin/streptomycin or dexamethasone using simple physical adsorption or when coated with SBF; results which suggest the need for further research on anodized titanium orthopedic implants possessing drug-eluting nanotubes.     

The effect of high-temperature annealing on optical properties of porous anodic alumina formed in oxalic acid.

Photoluminescence (PL) of anodic alumina membranes (AAMs) with ordered nanopore arrays fabricated in oxalic acid has been investigated under different annealing temperatures. X-ray diffraction reveals the structural transition from the amorphous state to crystallization. PL measurements show that a blue PL band occurs in the wavelength range 300-600 nm. The differential thermal analysis (DTA) and thermogravimetric analysis (TG) results revealed plentiful oxalic ions incorporated into the prepared AAMs. The PL band of AAMs could be attributed to the co-actions of the oxygen vacancies (F(+) and F centres) and the luminescent centres transformed from oxalic impurities. With the increase of the annealing temperature, the intensities of PL increase first, and at 500 degrees C reach a maximum value, then decrease. The PL phenomenon is intimately related to the temperature-induced structural transitions. There are three optical centres in the annealed AAMs; the first is originates from the F centres, the second is correlated with F(+) centres and the third is associated with the oxalic impurities incorporated in the AAMs.     

Greater osteoblast proliferation on anodized nanotubular titanium upon electrical stimulation

Currently used orthopedic implants composed of titanium have a limited functional lifetime of only 10–15 years. One of the reasons for this persistent problem is the poor prolonged ability of titanium to remain bonded to juxtaposed bone. It has been proposed to modify titanium through anodization to create a novel nanotubular topography in order to improve cytocompatibility properties necessary for the prolonged attachment of orthopedic implants to surrounding bone. Additionally, electrical stimulation has been used in orthopedics to heal bone non-unions and fractures in anatomically difficult to operate sites (such as the spine). In this study, these two approaches were combined as the efficacy of electrical stimulation to promote osteoblast (bone forming cell) density on anodized titanium was investigated. To do this, osteoblast proliferation experiments lasting up to 5 days were conducted as cells were stimulated with constant bipolar pulses at a frequency of 20 Hz and a pulse duration of 0.4 ms each day for 1 hour. The stimulation voltages were 1 V, 5 V, 10 V, and 15 V. Results showed for the first time that under electrical stimulation, osteoblast proliferation on anodized titanium was enhanced at lower voltages compared to what was observed on conventional (nonanodized) titanium. In addition, compared to nonstimulated conventional titanium, osteoblast proliferation was enhanced 72% after 5 days of culture on anodized nanotubular titanium at 15 V of electrical stimulation. Thus, results of this study suggest that coupling the positive influences of electrical stimulation and nanotubular features on anodized titanium may improve osteoblast responses necessary for enhanced orthopedic implant efficacy.