Effect of ball-milling and Fe-/Al-doping on the structural aspect and visible light photocatalytic activity of TiO2 towards Escherichia coli bacteria abatement

Topotactic formation of poriferous (Al,C)-Ta2O5 mesocrystals for improved visible-light photocatalysis

Poriferous monocrystal-like nanostructures are contributing to fabricate long-distance charge transfer pathways and rapid diffusions of the degraded products, and attracts wide attentions. In this work, layered and poriferous (Al,C)-Ta₂O₅ mesocrystals were fabricated by topotactic transformation strategy with Ta₄AlC₃ MAX as starting materials for visible-light photocatalytic antibiotic degradation. The prepared sample exhibited enhanced visible-light absorption and visible-light photocatalytic performance, far superior to those of commercial Ta₂O₅ and Ta₄AlC₃ MAX, which was mainly because of the elemental doping in the samples. The experimental results also indicated that continuous attacks of the photo-generated holes and ·O₂^- species efficiently induced efficient visible-light photodegradation of tetracycline. Current work also indicates a new and potential tantalum-based semiconductors for high-performance environmental photocatalysis.

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

The approach of this timely review considers the current literature that is focused on the interface nanostructure/cell-wall microorganism to understand the annihilation mechanism. Morphological studies use optical and electronic microscopes to determine the physical damage on the cell-wall and the possible cell lysis that confirms the viability and microorganism death. The key parameters of the tailoring the surface of the photoactive nanostructures such as the metal functionalization with bacteriostatic properties, hydrophilicity, textural porosity, morphology and the formation of heterojunction systems, can achieve the effective eradication of the microorganisms under natural conditions, ranging from practical to applications in environment, agriculture, and so on. However, to our knowledge, a comprehensive review of the microorganism/nanomaterial interface approach has rarely been conducted. The final remarks point the ideal photocatalytic way for the effective prevention/eradication of microorganisms, considering the resistance that the microorganism could develop without the appropriate regulatory aspects for human and ecosystem safety.

Synthesis and evaluation of highly dispersible and efficient photocatalytic TiO2/poly lactic acid nanocomposite films via sol-gel and casting processes

Using titanium teraisopropoxide (TTIP) as the hydrolysis material, titanium dioxide (TiO₂) (6.3-11.1 nm) nanoparticles were synthesized via the sol-gel method and reinforced into poly lactic acid (PLA)/TiO₂ nanocomposite films by casting. The effect of increasing amounts of TiO₂ on the structure and properties of PLA/TiO₂ nanocomposite films were evaluated. These results indicated that self-aggregation of TiO₂ nanoparticles in PLA films could be avoided via sol-gel and casting processes. The presence of TiO₂ significantly improved the tensile strength and thermal stability of films. The PLA/TiO₂ (0.6 wt%) film exhibited the highest photocatalytic activity efficiency under UV irradiation and displayed high antibacterial activities with optimal inhibition zones of Staphylococcus aureus, followed by Escherichia dispersibility of TiO₂ in films were responsible for those improvements. This study suggests that PLA/TiO₂ nanocomposite films could be a promising antimicrobial alternative material to conventional plastic packages.

Fe-TiO 2 Nanoparticles Synthesized by Green Chemistry for Potential Application in Waste Water Photocatalytic Treatment

Anatase TiO2 nanoparticles doped with iron ions have been synthesized via the green chemistry method using aqueous extract of lemongrass (Cymbopogon citratus) obtained from Soxhlet extraction and doped by wet impregnation. The TiO2 anatase phase has been doped with Fe3+ (0.05, 0.075, and 0.1 Fe3+ : Ti molar ratio) at 550°C and 350°C, respectively. The scanning electron microscopy with energy-dispersive X-ray (SEM-EDS) shows nanoparticle clusters and efficiencies of impregnations between 66.5 and 58.4% depending on the theoretical dopant amount. The electron transmission microscopy (TEM) reveals final particle sizes ranging between 7 and 26 nm depending on the presence or not of the dopant. The cathodoluminescence (CL) and photoluminescence (PL) studies of the doped and undoped nanoparticles show a luminescence signal attributed to surface oxygen vacancies (visible CL emission 380–700 nm and PL emission 350–800 nm); additionally, a decrease in emission intensity is observed due the inhibition of the recombination of the photogenerated electron-holes pairs; moreover, nanopowders were analyzed by UV-Vis spectrophotometry of diffuse reflectance, and the absorption edge of the Fe-TiO2 in comparison to undoped TiO2 is extended greatly toward the visible light. The six bands (A1g + 2B1g + 3Eg) found by Raman spectroscopy and the x-ray diffraction pattern (XRD) confirm that synthesized TiO2 is only anatase phase, which is commonly used as a catalyst in waste water treatment, specifically in heterogeneous photocatalytic processes.

Visible light-assisted efficient degradation of dye pollutants with biomass-supported TiO2 hybrids

The objective of this work was to develop a novel organic-inorganic hybrid nanomaterial from agricultural biomass waste for environmental applications. The sugarcane bagasse (SB) supported TiO₂ hybrids were firstly synthesized via a sol-gel method. A series of characterizations were carried out to reveal the structures and components of obtained hybrids. Due to organic-inorganic hybrid (OIH) effect and element doping, the SB-TiO₂ hybrid can expand its optical absorbance ranging from ultraviolet to visible light. The optimal hybrid catalyst prepared with SB doping amount of 2g in 100mL titanic gel and calcined at 200°C was able to degradate 95.0% methyl orange (MO) in 5h under visible light. This study will pave a new and facile pathway for novel visible light driven photocatalysts based on TiO₂ modified by agricultural biomass waste.

Theoretical calculation and experiment study on the electronic structure, microstructures and photocatalytic activity of N–Al codoped TiO2

To more accurately demonstrate how the electronic structure was changed and to explain the origin of the enhanced photocatalytic activity by N–Al codoped TiO₂, we investigated N, Al monodoped, and codoped TiO₂by theoretical calculation and experiments.

Broad-spectrum antimicrobial photocatalysis mediated by titanium dioxide and UVA is potentiated by addition of bromide ion via formation of hypobromite

Antimicrobial photocatalysis involves the UVA excitation of titanium dioxide (TiO2) nanoparticles (particularly the anatase form) to produce reactive oxygen species (ROS) that kill microbial cells. For the first time we report that the addition of sodium bromide to photoactivated TiO2 (P25) potentiates the killing of Gram-positive, Gram-negative bacteria and fungi by up to three logs. The potentiation increased with increasing bromide concentration in the range of 0-10mM. The mechanism of potentiation is probably due to generation of both short and long-lived oxidized bromine species including hypobromite as shown by the following observations. There is some antimicrobial activity remaining in solution after switching off the light, that lasts for 30min but not 2h, and oxidizes 3,3',5,5'-tetramethylbenzidine. N-acetyl tyrosine ethyl ester was brominated in a light dose-dependent manner, however no bromine or tribromide ion could be detected by spectrophotometry or LC-MS. The mechanism appears to have elements in common with the antimicrobial system (myeloperoxidase+hydrogen peroxide+bromide).