Fig 1.
Transmission electron microscopy characterization of Cu-TiO2NTs.
(A) and (B) high resolution transmission electron microscopy (HRTEM); (C) high-angle annular dark-field imaging scanning transmission electron microscopy (HAADF-STEM); (D) annular bright-field scanning transmission electron microscopy (ABF-STEM) and (E) HAADF-STEM of the same region; (F) ABF-STEM and; (G) HAADF-STEM of the same region of the CU doped TiO2 nanotubes with 1.2% of copper with the accompanying line intensity profile, acquired in direction indication by arrow.
Fig 2.
Photocatalytic activity of TiO2 nanotubes and TiO2 nanotube coated surface.
A) Hydroxyl radical production at a TiO2 nanotube surface versus illumination wavelength measured at high concentration of the spin trap ethanol (17 M), data points are average values of multiple measurements, error bars represent standard errors; B) Hydroxyl radical production of a TiO2 nanotube coated surface measured at low concentration of spin trap DEPMPO (50mM) illuminated with a light emitting diode with peak wavelength of 320 nm. Height of the bars represent average values of 17 measurements (N = 17); error bars represent standard deviations. Each data point is also shown on the graph as closed squares for “TiO2NTs” series and as closed grey circles for “Cu-TiO2NTs” series.
Fig 3.
Deposition heterogeneity and stability of copper doped TiO2 nanotubes on a polymer surface.
A) scanning electron microscopy image of TiO2 nanotubes deposited on a surface. B) relative activity of Cu2+-doped TiO2 nanotubes measured after several washing cycles at different pH and normalized to the activity measured before first washing. C) similar relative activity of the Degussa P25 deposition (water—bars with texture with diagonal lines, acid–bars with no texture, base–bars with dotted texture), without abrasion. Height of the bars represent average values of 6 measurements for each bar (N = 6); error bars represent standard deviations.
Fig 4.
Antibacterial activity of Cu-TiO2NTs treated petri dishes against different microorganisms.
(A) L. innocua; (B) S. aureus; (C) MRSA; (D) E. coli ESBL; and (E) E. coli. Number of colonies on control surfaces without the antibacterial coating kept in dark for 24 hours at 4°C in a refrigerator are shown as closed grey circles; Number of colonies on Cu-TiO2NTs coated petri dishes illuminated with 300 mW/m2 UVA light for 24 hours at 4°C in a refrigerator are shown as closed red circles; Number of colonies on control surfaces counted directly after inoculation are shown as closed black circles. Vertical arrows in each subframe of the figure represent the uncountable number of colonies (in our case set to 350) Straight lines through the data points represent best fit with only one parameter shown in frame F; (F) reduction of the number of microorganisms with regards to the number of inoculated microorganisms. Height of the bars represents value of regression coefficient a obtained by linear regression f = a*x through all the data points in each frame from A to E: 5 points (N = 5) for “L. inncoua” series, 9 points (N = 9) for “S. aureus” series, 6 points (N = 6) for “MRSA” series, 14 points (N = 14) for “E. coli ESBL” series, and 9 points (N = 9) for “E. coli” series. Error bars represent standard error of the regression coefficient.
Fig 5.
Characterization of Cu-TiO2NTs coated surfaces inoculated with L. innocua using bleaching-corrected fluorescence microspectroscopy.
All samples were labeled with rhodamine B isothiocyanate (RITC). Column 1: wavelength of the fluorescence emission peak; and Column 2: bleaching rate images are shown for A) control—uncoated polymer surface, B) Cu-TiO2NTs coated surface, C) uncoated surface inoculated with L. innocua, and D) Cu-TiO2NTs coated surface inoculated with L. innocua. The spectrally contrasted images are color coded based on the local values of the associated fluorescence parameter (values for RITC spectral peak position (λMAX) and bleaching rate (b), respectively). Lengths of the scale bars correspond to 10 μm on the sample. The white arrows mark individual bacteria that were identified by the spectral analysis.
Fig 6.
Scanning electron micrographs of Cu-TiO2NTs coated surfaces inoculated with L. innocua.
A) uncoated surface; B) uncoated surface at higher magnification; C) Cu-TiO2NTs coated surface; D) Cu-TiO2NTs coated surface at higher magnification; bacteria are indicated by white arrows.