Abstract
Thin films of TiO
2
, TiO
2
-multiwalled carbon nanotubes (TiO
2
–MWCNT), Fe-doped TiO
2
–MWCNT (Fe–TiO
2
–MWCNT), and Ag-doped TiO
2
–MWCNT (Ag–TiO
2
–MWCNT) supported on glass substrates were successfully prepared by sol–gel drop coating method. MWCNTs were treated by H
2
SO
4
and HNO
3
to oxidize graphitic carbon. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV-Vis) absorption spectroscopy to confirm their structure and optical properties. XRD patterns of all prepared films exhibited (101), (004), (200), (105), (211), (204), (116), (220), (215), and (224) planes of anatase-phase TiO
2
. A pronounced broad peak at ~3400 cm
−1
in the FTIR spectrum of the MWCNT confirmed oxidation of some carbon atoms on the surface of MWCNTs by HNO
3
and H
2
SO
4
. The photocatalytic and antibacterial activities of the prepared materials were tested under visible-light irradiation based on degradation of methylene blue (MB) dye in aqueous solution and reduction in the viable count of
Escherichia coli
, respectively. Fe or Ag was doped into the TiO
2
-MWCNT composites, lowering the bandgap and thereby enabling enhanced photocatalytic activity in the visible-light region. Based on the MB photodegradation results, the photocatalytic efficiency of the Fe–TiO
2
–MWCNT and Ag–TiO
2
–MWCNT composites could be due to the following mechanism: (1) adsorption and photoinduced electron absorption by MWCNT, and (2) electron trapping by Fe or Ag within the TiO
2
matrix, in addition to the usual photocatalytic activity of TiO
2
. Moreover, as-synthesized Ag–TiO
2
–MWCNT composite films showed outstanding antimicrobial activity.