Electrochemical Entinostat purchase anodization was carried out with a DC voltage stabilizer. All of the samples were fabricated at 15 V (for 1.5 h) in electrolytes of 1 M NaH2PO4 containing 0.5 wt.% HF. The as-anodized samples were annealed at either 450°C or 550°C for 1 h in air to obtain crystallized nanofilms. Nanofilm sensors were fabricated using circular Pt electrodes and conductive wires for PCB assembly. Detailed sensor fabrication process

can be found in our previous work [23]. Characterization of nanostructure films Surfaces of the above as-anodized and as-annealed samples were characterized with a scanning electron microscope (SEM; FEI SIRION 200, Hillsboro, OR, USA) equipped with energy dispersive X-ray analysis (EDXA; OXFORD INCA, Fremont, CA, USA). Surface

compositions of the nanofilms were characterized with X-ray photoelectron spectroscopy (XPS; ESCALAB 250, Thermo VG Scientific, West Sussex, UK). The phase structures of the as-annealed samples were characterized with X-ray diffraction (XRD; D/max 2550 V, Rigaku, Tokyo, Japan). Grazing incident diffraction with an incident angle of 1° was carried out during the XRD testing. Testing PFT�� chemical structure of hydrogen sensors The nanofilm sensors were tested in alternating atmospheres of air and 1,000 ppm H2 at temperatures ranging from 25°C to 300°C. A Keithley 2700 multimeter (Cleveland, OH, USA) was used to test the resistance of the nanofilm sensor during the hydrogen sensing experiments. Results Ti-Al-V-O

oxide nanofilms formed during the anodization process. Figure 1 shows the anodization current transients (I-t curves) recorded at the constant anodization voltage of 15 V. The anodization current decreased rapidly from 7 to 2 mA, which corresponded to the formation of a barrier oxide at the alloy surface. At the stage of current increase to a peak value of Carbohydrate 2.4 mA, the pores of oxide film grew randomly. After the peak point, the current decreased to reach a nearly steady-state value indicating that self-assembled oxide nanofilm could be grown on the alloy substrate [7]. Figure 1 Current density vs. time curve of the anodization process. Original Ti6Al4V alloy consisted of two different phases (α and β). The major phase was α phase. Figure 2a shows the surface morphology and cross-sectional image of the oxide nanofilms grown on the Ti6Al4V substrate. The oxide nanofilms consisted of two kinds of nanostructures, i.e., nanotubes grown at the α-phase Cell Cycle inhibitor region and inhomogeneous nanopores grown at the β-phase region [22]. Average inner diameter of the nanotubes grown at the α-phase region was 65 nm, and average length of the nanotubes was around 800 nm (Figure 2c). Figure 2 SEM images of the oxide nanofilms before and after annealing.