Synthesis and characterization of fluorinated anatase nanoparticles and subsequent N-doping for efficient visible light activated photocatalysis.

Fluorinated-titanium dioxide (TiO2-F) nanoparticles in a pure anatase polymorph was precipitated from solution by hydrolysis of titanium oxychloride, using urea and ammonia as precipitation agents and potassium fluoride as a source of fluorine anion. A further wet attrition milling in presence of glycine completed by a heat treatment allowed an additional nitrogen doping of TiO2 (TiO2-F&N-HT). The morphology and crystalline structure of the as-synthesized powder was determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD) and showed that TiO2 powder was composed of nanoparticles with narrow size distribution which crystallized in the anatase phase. X-ray photoelectron spectroscopy (XPS) revealed that fluorine and nitrogen are present in TiO2 as surface fluorination and interstitial doping, respectively. UV-vis diffuse reflectance spectroscopy (DRS) showed an increased optical absorption in the visible for TiO2-F&N-HT sample. Under visible light irradiation, TiO2-F nanoparticles showed a high photocatalytic performance, showing the high potential of an improved surface fluorination for Escherichia coli (E. coli) disinfection in suspension. These results show the importance of anatase-TiO2 nanoparticles synthesis and modification by using a wet chemical approach leading to low aggregation and high specific surface area for effective bacterial inactivation. The co-doped TiO2-F&N-HT powder showed slightly improved performance compared to the fluorinated sample. The significant degree of aggregation after the heat treatment is postulated as being a limiting factor in its photocatalytic activity.

Bacterial adhesion and inactivation on Ag decorated TiO2-nanotubes under visible light: Effect of the nanotubes geometry on the photocatalytic activity.

This study investigates the effect of the diameter of TiO2 nanotubes and silver decorated nanotubes on optical properties and photocatalytic inactivation of Escherichia coli under visible light. The TiO2 nanotubes (TiO2-NTs) were prepared using the electrochemical method varying the anodization potential starting from 20 V until 70 V. The Ag nanoparticles were carried out using the photoreduction process under the same experimental conditions. The diameter size was determined using the scanning electronic microscopy (SEM). TiO2-NTs diameter reached ∼100 nm at 70 V. Transmission electronic microscopy (TEM) imaging confirmed the TiO2-NTs surface decoration by silver nanoparticles. The Ag-NPs average size was found to be equal to 8 nm. The X-Ray diffraction (XRD) analysis confirm that all TiO2-NTs crystallize in the anatase phases regardless the used anodization potential. The decrease of the photoluminescence (PL) intensity of Ag NPs decorated TiO2-NTs indicates the decrease of the specific area when the nanotubes diameter increases. The UV-vis absorbance show that the absorption edges was bleu shifted with the increasing of nanotubes diameter, which can be explained by the increase of the crystallites average size. The bacterial adhesion and inactivation tests were carried in the dark and under light. Bacteria were seen to adhere on TiO2-NTs in the dark; however, under light the bacteria were killed before they establish a strong contact with the TiO2-NTs and Ag/TiO2-NTs surfaces. Bacterial inactivation kinetics were faster when the anodizing potential of the NTs-preparation increases. A total bacterial inactivation was obtained on ∼100 nm nanotubes diameter within 90 min. This result was attributed to the enhancement of the TNTs crystallinity leading to reduced surface defects. Redox catalysis was seen to occur under light on the TiO2-NTs and Ag/TiO2-NTs. the photo-induced antibacterial activity on the AgO/Ag2O decorated TiO2-NTs was attributed to the interfacial charge transfer mechanism (IFCT).

Sputtered Gum metal thin films showing bacterial inactivation and biocompatibility.

Super-elastic Titanium based thin films Ti-23Nb-0.7Ta-2Zr-(O) (TNTZ-O) and Ti-24Nb-(N) (TN-N) (at.%) were deposited by direct current magnetron sputtering (DCMS) in different reactive atmospheres. The effects of oxygen doping (TNTZ-O) and/or nitrogen doping (TN-N) on the microstructure, mechanical properties and biocompatibility of the as-deposited coatings were investigated. Nano-indentation measurements show that, in both cases, 1sccm of reactive gas in the mixture is necessary to reach acceptable values of hardness and Young's modulus. Mechanical properties are considered in relation to the films compactness, the compressive stress and the changes in the grain size. Data on Bacterial inactivation and biocompatibility are reported in this study. The biocompatibility tests showed that O-containing samples led to higher cells proliferation. Bacterial inactivation was concomitant with the observed pH and surface potential changes under light and in the dark. The increased cell fluidity leading to bacterial lysis was followed during the bacterial inactivation time. The increasing cell wall fluidity was attributed to the damage of the bacterial outer cell which losing its capacity to regulate the ions exchange in and out of the bacteria.

New evidence for Cu-decorated binary-oxides mediating bacterial inactivation/mineralization in aerobic media.

Binary oxide semiconductors TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 (TiO2-ZrO2-Cu) uniform films were sputtered on polyester (PES). These films were irradiated under low intensity solar simulated light and led to bacterial inactivation in aerobic and anaerobic media as evaluated by CFU-plate counting. But bacterial mineralization was only induced by TiO2-ZrO2-Cu in aerobic media. The highly oxidative radicals generated on the films surface under light were identified by the use of appropriate scavengers. The hole generated on the TiO2-ZrO2 films is shown to be the main specie leading to bacterial inactivation. TiO2-ZrO2 and Cu-decorated TiO2-ZrO2 films release Zr and Ti <1ppb and Cu 4.6ppb/cm(2) as determined by inductively coupled plasma mass spectrometry (ICP-MS) This level is far below the citotoxicity permitted level allowed for mammalian cells suggesting that bacterial disinfection proceeds through an oligodynamic effect. By Fourier transform attenuated infrared spectroscopy (ATR-FTIR) the systematic shift of the predominating νs(CH2) vibrational-rotational peak making up most of the bacterial cell-wall content in C was monitored. Based on this evidence a mechanism suggested leading to CH bond stretching followed by cell lysis and cell death. Bacterial inactivation cycling was observed on TiO2-ZrO2-Cu showing the stability of these films leading to bacterial inactivation.

Coupling of narrow and wide band-gap semiconductors on uniform films active in bacterial disinfection under low intensity visible light: implications of the interfacial charge transfer (IFCT).

This study reports the design, preparation, testing and surface characterization of uniform films deposited by sputtering Ag and Ta on non-heat resistant polyester to evaluate the Escherichia coli inactivation by TaON, TaN/Ag, Ag and TaON/Ag polyester. Co-sputtering for 120 s Ta and Ag in the presence of N2 and O2 led to the faster E. coli inactivation by a TaON/Ag sample within ∼40 min under visible light irradiation. The deconvolution of TaON/Ag peaks obtained by X-ray photoelectron spectroscopy (XPS) allowed the assignment of the Ta2O5 and Ag-species. The shifts observed for the XPS peaks have been assigned to AgO to Ag2O and Ag(0), and are a function of the applied sputtering times. The mechanism of interfacial charge transfer (IFCT) from the Ag2O conduction band (cb) to the lower laying Ta2O5 (cb) is discussed suggesting a reaction mechanism. The optical absorption of the TaON and TaON/Ag samples found by diffuse reflectance spectroscopy (DRS) correlated well with the kinetics of E. coli inactivation. The TaON/Ag sample microstructure was characterized by contact angle (CA) and by atomic force microscopy (AFM). Self-cleaning of the TaON/Ag polyester after each disinfection cycle enabled repetitive E. coli inactivation.

Innovative TiO2/Cu nanosurfaces inactivating bacteria in the minute range under low-intensity actinic light.

The bacterial inactivation of E. coli by cotton TiO(2)/Cu DC-magnetron sputtered thin films was investigated in the dark and under low-intensity actinic light. The TiO(2)/Cu sputtered layers revealed to be sensitive to actinic light showing the spectral characteristics of Cu/CuO. This indicates that Cu does not substitute Ti(4+) in the crystal lattice. Under diffuse actinic light (4 mW/cm(2)), the hybrid composite TiO(2)/Cu sample lead to fast bacterial inactivation times <5 min. This study presents evidence for a direct relation between the film optical absorption obtained by diffuse reflectance spectroscopy (DRS) and the bacterial inactivation kinetics by the TiO(2)/Cu samples. The Cu-ions inactivating the bacteria were followed in solution by inductively plasma coupled spectroscopy (ICPS). The amounts of Cu-ions detected by ICPS provide the evidence for an oligodynamic antibacterial effect. The changes in the oxidation state of Cu during bacterial inactivation were followed by XPS. The E. coli cell viability was detected by standard coliform counting CFU methods. The TiO(2)/Cu thickness layer was determined by profilometry and the film microstructure by XPS, TEM, AFM, XRD, XRF and contact angle (CA). A mechanism of bacterial inactivation by TiO(2)/Cu samples is suggested in terms of interfacial charge transfer (IFCT) involving charge transfer between TiO(2) and Cu.