The systematic tunability of nanoparticle dimensions through the controlled loading of surface-deposited diblock copolymer micelles

The continuous tunability of iron oxide nanoparticle dimensions is demonstrated using the pH controlled loading of ferric nitrate from aqueous solution into polystyrene–block–polyacrylic acid reverse micelles deposited on a silicon substrate. Quasi-hexagonally ordered two-dimensional arrays of iron oxide nanoparticles with a systematic tunability of particle heights in the sub-10 nm regime and a constant periodicity are obtained and characterized with atomic force microscopy and x-ray photoelectron spectroscopy.

Influence of gold particle size on the photocatalytic activity for acetone oxidation of Au/TiO2 catalysts prepared by dc-magnetron sputtering

Francis Lévy

Two series of Au/TiO2 materials with different gold content have been prepared by dc-magnetron sputtering on ceramic shaped pure anatase or Degussa P25 TiO2. The time of deposition was varied between 1 and 20 min in order to obtain different thickness and nanoparticle size of the gold films. For comparison samples with Au loadings in the range 0.3-0.9 wt% were prepared using the deposition-precipitation methodology. The obtained materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). DR-UV-Vis and atomic force and scanning electron microscopy techniques. The photocatalytic activity was checked in the photo-oxidation of acetone under both UV and visible irradiation conditions. Several factors were found to influence the photoactivity. An optimal Au content corresponding to a maximum activity is observed and attributed to the occurrence of adequate titania surface coverage and Au particle size. The support plays an important role and it was found that pristine anatase on which gold (average particle size 7.7 nm) was deposed by dc-reactive sputtering exhibits the maximum of the activity. Samples prepared by dc-sputtering were more active than samples prepared by deposition-precipitation method. Also, the photocatalysts prepared using dc-reactive sputtering showed activity under both UV and visible light irradiation, while those prepared using the deposition-precipitation technique are active only under UV light. The most likely mechanism of gold activation of titania is that upon light absorption, gold nanoparticles inject electrons into the titania conduction band. (C) 2011 Elsevier B.V. All rights reserved.

2011

Recent advances on sputtered films with Cu in ppm concentrations leading to an acceleration of the bacterial inactivation

Juan Kiwi, Sami Rtimi

This review focuses on the acceleration of the bactericidal and fungicidal effects by uniform, adhesive Cu-based nanocomposites on textile and thin polymer surfaces. The acceleration of the bacterial inactivation kinetics mediated by Cu, TiO2/Cu and ZrO2-TiO2-Cu films in aerobic and anaerobic media is discussed for Gram negative, Gram positive bacteria and fungi. The Cu induced bacterial inactivation kinetics in the dark was observed to occur within the minute range for diverse bacteria. The characterization of the innovative Cu-films microstructure by several surface science techniques is described. This allows the correlation of the surface-reactivity features of the Cu-composite films mediating bacterial inactivation. The redox reactions on the Cu-films during the bacterial inactivation are documented by X-ray-photoelectron spectroscopy (XPS). Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was used to monitor the changes in the functional groups leading to bacterial inactivation as a function of the bacterial inactivation time. The dependence of the inactivation kinetics on the Cu-loaded surface roughness is accounted for in qualitative way by atomic force microscopy (AFM). A mechanism for the bacterial inactivation induced by the Cu-nanoparticles by way of reactive oxygen species (ROS) in aerobic and anaerobic processes is discussed. The interfacial charge transfer (IFCT) mechanism under light irradiation between Cu and TiO2 or for the Cu with the binary oxide ZrO2-TiO2 is suggested. The relative potential band-position in the Cu-sputtered semiconductors responsible for the charge transfer is discussed. Evidence was found for the presence in anaerobic media of highly oxidative valence band holes (h+)(vb) at -0.4 eV generated by Cu2O. The variation in the interface surface potential (Eigenvalues) of the Cu-films during the bacterial inactivation was monitored and allowed to suggest the bacterial mineralization mechanism. Details for the reactions of the Cu-surfaces with Escherichia coli (E. coli) and Methicillin Resistant Staphylococcus Aureus (MRSA) inactivation are described. Evidence for the synergism between Cu and the TiO2 accelerating the bacterial inactivation kinetics is presented in this review.

ELSEVIER2020

Recent advances on sputtered films with Cu in ppm concentrations leading to an acceleration of the bacterial inactivation

Juan Kiwi, Sami Rtimi

ELSEVIER2020