Cu-Doped TiO2: Visible Light Assisted Photocatalytic Antimicrobial Activity

Abstract

Surface contamination by microbes is a major public health concern. A damp environment is one of potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO2) can effectively curb this growing threat. Metal-doped titania in anatase phase has been proven as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu)-doped TiO2 (Cu-TiO2) was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO2 was carried out via sol-gel technique. Cu-TiO2 further calcined at various temperatures (in the range of 500–700 °C) to evaluate the thermal stability of TiO2 anatase phase. The physico-chemical properties of the samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV–visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO2 was maintained well, up to 650 °C, by the Cu dopant. UV–vis results suggested that the visible light absorption property of Cu-TiO2 was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasize the introduction of Cu+ and Cu2+ ions by replacing Ti4+ ions in the TiO2 lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9999%) was attained in 30 min of visible light irradiation by Cu-TiO2.

Antibacterial Activity of Visible Light-Activated TiO2 Thin Films with Low Level of Fe Doping

“…erefore, in order to extend the spectral response to visible light region, efforts to combine TiO 2 with other elements such as metal deposition [11,[14][15][16][17], nonmetal doping [18][19][20][21], and metal and nonmetal codoping [22,23] have been carried out. Doping TiO 2 with transition metals such as Fe [11,24], Cr [25], Cu [26,27], and Zn [28] is a simple and effective method. More recently, antibacterial properties of TiO 2 with various morphologies such as graphene nanosheet doped TiO 2 [29], titania nanotubes [6], and Fe-Ag/TiO 2 bimetallic nanowires [30] were reported.…”

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes

“…By itself, this metal exhibits antibacterial and antiviral properties since Cu ions can infiltrate across their cell membrane [65,66]. % to cause a substitution in the crystal lattice [69]. According to theoretical studies based on the DFT theory, the incorporation of Cu ions in the TiO2 should be less than 0.3 at.…”

“…From the inside, Cu ions can alter the charge balance of the microorganism, which provides its deformation until cell lysis [67,68]. In this sense, the Cu 2+ /Cu + ions can replace the Ti 4+ from the TiO2 crystal lattice resulting in the formation of single and double oxygen vacancies [69]. % to cause a substitution in the crystal lattice [69].…”

“…% to cause a substitution in the crystal lattice [69]. Previous studies have reported the use of a Cu-TiO2 system for the removal of several microorganisms such as Escherichia coli [67,69,70,71,72], In consequence, Cu-doped TiO2 increases its charge-transfer resistance and decreases the capacitance, in addition to exhibiting a shift in the optical absorption edge to the visible region which indicates a narrowing of the band gap in the semiconductor [70].…”

Synthesis, Characterization and Photocatalytic Activity of Nanocrystalline First Transition-Metal (Ti, Mn, Co, Ni and Zn) Oxisde Nanofibers by Electrospinning

“…In addition, the recycle ability of ZnO, TiO 2 and NiO nanofibers were also studied (Figure 9b), after the third recycle, the photocatalytic efficiency remains 95.9%, 87.1% and 65.4%, respectively, which indicates that ZnO and TiO 2 nanofibers have an excellent catalytic cycling ability. Many researchers have explained the mechanism of photolysis [55][56][57][58]: when the ZnO, TiO 2 and NiO are excited by UV light with energy higher than or equal to their band gaps, electrons (e − ) in the valence band (VB) can be excited to the conduction band (CB), leaving corresponding holes (h + ) in the VB. Photogenerated electrons (e − ) on the surface of nanoparticles are easily captured by electronic acceptors such as oxygen dissolved in water to form superoxide radicals (·O 2 − Furthermore, it should be pointed out that the photocatalytic degradation is actually a free radical reaction.…”