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This chapter introduces unique methodology of antibacterial activity evaluation of nanoparticles in both solution and thin films. Nanoparticles of ZnO, TiO 2 , and CuO are synthesized via the sol-gel method. Antibacterial tests are carried out against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria using disk diffusion and bioluminescence. To perform antibacterial tests on thin films and to overcome bacterial strains recuperation on the supports, a new method of bacterial detaching from the slides is developed based on French standard NF EN 14561., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

We report on an elaboration of new composite photocatalysts (TiO 2 -P 25 @ n-TiO 2 @HAP) based on grafted size-selected 5-nm titanium-oxo-alkoxo nanoparticles on P25-TiO 2 nanoparticles and HAP obtained by co-precipitation of salts. The 5-nm oxo-TiO 2 particles were prepared in a sol-gel reactor with rapid reagents micromixing. The photocatalytic test of ethylene degradation, in a continuous-flow fixed-bed reactor, showed an increase of the photocatalytic yield for the composite photocatalysts with an addition of HAP. This result was interpreted by a synergy between adsorption and photo-oxidation.

TiO2 nanoparticles were prepared via sol-gel method using a chemical reactor with ultra-rapid micromixing. The as-formed nanoparticles atomic structure was characterized using the pair distribution function method and compared to the structure of several titanium oxide based compounds (anatase, rutile, brookite, Tilepidocrocite-type). The best agreement was obtained with the Ti-lepidocrocite-type structure. Connection between photocatalytic properties and atomic structure of the nanoparticles was discussed. [ABSTRACT FROM AUTHOR]

Due to surface effects and quantum size effects, nanomaterials have properties that are vastly different from those of bulk materials due to surface effects. The particle size distribution plays an important role in chemical and physical properties. The measurement and control of this parameter are crucial for nanomaterial synthesis. Dynamic light scattering (DLS) is a fast and non-invasive tool used to measure particle size, size distribution and stability in solutions or suspensions during nanomaterial preparation. In this review, we focus on the in situ sizing of nanomaterial preparation in the form of colloids, especially for metal oxide nanoparticles (MONs). The measuring principle, including an overview of sizing techniques, advantages and limitations and theories of DLS were first discussed. The instrument design was then investigated. Ex-situ and in situ configuration of DLS, sample preparations, measurement conditions and reaction cell design for in situ configuration were studied. The MONs preparation monitored by DLS was presented, taking into consideration both ex situ and in situ configuration. [ABSTRACT FROM AUTHOR]

Stable TiO2-P25@n-TiO2 nanocoating was prepared based of grafted size selected 5 nm Titanium-oxo-alkoxo (n-TiO2) nanoparticles on P25-TiO2 nanoparticles surface and their immobilization on Aluminium substrate. The 5-nm oxo-TiO2 particles were prepared in a sol-gel reactor with rapid reagents micromixing. The photocatalytic test of ethylene degradation, in a continuous-flow fixed bed reactor, showed an increase of the photocatalytic yield with number of the deposited layers until a sursaturation regime. By modeling the photocatalytic activity of the composite, a death layer of electron-hole pairs excitation of 20 nm, corresponding of the film thickness, was found. Furthermore, the estimation of the TiO2 absorption coefficient (k≤2 .104 cm-1) indicates a strong porosity of the deposited films. [ABSTRACT FROM AUTHOR]

We report on an elaboration of new composite photocatalysts (TiO2–P25@ n-TiO2@HAP) based on grafted size-selected 5-nm titanium-oxo-alkoxo nanoparticles on P25-TiO2 nanoparticles and HAP obtained by co-precipitation of salts. The 5-nm oxo-TiO2 particles were prepared in a sol–gel reactor with rapid reagents micromixing. The photocatalytic test of ethylene degradation, in a continuous-flow fixed-bed reactor, showed an increase of the photocatalytic yield for the composite photocatalysts with an addition of HAP. This result was interpreted by a synergy between adsorption and photo-oxidation. [ABSTRACT FROM AUTHOR]

In a previous work in our team (Oualha et al., Chem Eng Trans, vol 73, 67-72 (2019)) it was shown that at large Reynold numbers (Re > 8000) a vapor phase appears by cavitation in T-mixer reactors used for chemical precipitation of nanoparticles. This phenomenon can affect dramatically the properties of the obtained nanoparticles. In the work of Oualha et al (2019), the apparent size (more precisely the hydrodynamic diameters) of vapor bubbles due to the cavitation, was in situ monitored in the reactor by using SLS (Static Light Scattering) and DLS (Dynamic Light Scattering) methods. A modeling was also given using Fluent software: calculated size population of bubble was provided. Unfortunately this population could not be directly compared to experimental data since the relationship between apparent and real size was unknown. In the present work, new DLS measurements using particles of calibrated sizes are presented to help us to interpret and comment our previous results on bubbles size distribution. They were obtained using a new apparatus designed and realized for the purpose of defining a method of true diameters measurement. [ABSTRACT FROM AUTHOR]

Titanium-vanadium oxo-alkoxy (VTOA) nanoparticles with vanadium addition (V:Ti) between 0 and 20 mol% were prepared via sol-gel method in a chemical reactor with ultra-rapid micromixing. A control of the nucleation and growth process in the reactor permitted synthesis of size-selective V-TiO2 nanoparticles, which were used for the nanocoatings deposition on glass beads. The activity of the prepared photocatalysts (after calcination at 450 °C) was studied by the degradation of methylene blue in aqueous solutions under UVA illumination. A steady decrease of the reaction rate was observed with an increase of the vanadium content. This effect was explained by the residual presence of non-crystallized oxide, which elimination requires further studies. [ABSTRACT FROM AUTHOR]

A comparative evaluation of the antibacterial effect of silver in the form of nanoparticles and Ag+ ions was performed. Silver nanoparticulate coatings of stable and reproducible morphology were prepared on monolayer size-selected titanium-oxo-alkoxy nanoparticles deposited on glass substrates. The coatings exhibit a strong antibacterial activity towards Escherichia coli K12 AB 1157 and suppress biofilms formation. This activity is mainly related to the Ag+ ions release into aqueous solutions in dark. The deposited silver mass ~1 μg.cm -2 is smaller compared to that of Ag+ ions and nanoparticles generally reported for inhibiting Escherichia coli. The synergetic effect of the deposited nanoparticles and Ag+ ions can be suggested. [ABSTRACT FROM AUTHOR]

We report on the effect of mixing on the morphology of ultrafine zinc oxide nanoparticles synthesized via a polyol process using zinc acetate and water in a diethylene glycol medium. Three mixing strategies were considered: stirred batch, T-mixer, and impinging free jets. The particle granulometry was accessed using the transmission electron microscopy and x-ray diffraction methods. The nanoparticle size and polydispersity decreased with an increase in the local dissipated energy. In particular, the polyol process conducted in the same chemical environment at 353 K did not lead to the observation of nanoparticles in the stirred batch reactor but resulted in unconventionally small 6-nm particles in the T-mixer and impinging jet configurations. This result is apparently related to the micromixing eddy geometry described by the Kolmogorov length. The hydrodynamic flow patterns and energy dissipation were obtained from computational fluid dynamics simulations, which are essential in the design, optimization, and scale-up of the polyol process. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1708-1721, 2015 [ABSTRACT FROM AUTHOR]

Abstract: We report on photocatalytic activity of new homogeneously Fe(III)-doped TiO2 nanocoatings. The material is prepared in a two-stage process including (1) oxo-TiO2 nanoparticles nucleation, doping by iron(acetylacetonate)3 and reactive deposition on glass substrates in a sol–gel micromixing reactor and (2) thermal treatment. The photocatalytic test of the nanocoatings is conducted on ethylene degradation in a continuous-flow fixed bead reactor. The catalyst shows the best performance at Fe/Ti molar ratio of 0.005at.%, which is explained by a competition between VB-hole localisation on Fe3+ and its annihilation on Fe2+. The proposed model permits an estimation of the localisation distance of the CB-electron in anatase TiO2 after a photoexcitation and defines the optimal size for the nanoparticulate TiO2 photocatalyst to be ∼8nm. [Copyright &y& Elsevier]

Efficient photocatalysis for gas cleaning purposes requires a large accessible, illuminated active surface in a simple and compact reactor. Conventional concepts use powdered catalysts, which are nontransparent. Hence a uniform distribution of light is difficult to be attained. Our approach is based on a coarse granular, UV-A light transparent, and highly porous adsorbent that can be used in a simple fixed bed reactor. A novel sol-gel process with rapid micro mixing is used to coat a porous silica substrate with TiO2-based nanoparticles. The resulting material posses a high adsorption capacity and a photocatalytic activity under UV-A illumination (PCAA = photocatalytic active adsorbent). Its photocatalytic performance was studied on the oxidation of trichloroethylene (TCE) in a fixed bed reactor setup in continuous and discontinuous operation modes. Continuous operation resulted in a higher conversion rate due to less slip while discontinuous operation is superior for a total oxidation to CO2 due to a user-defined longer residence time. [ABSTRACT FROM AUTHOR]

• Nucleation-growth process of vanadium-titanium oxo-alkoxy species was investigated. • At V ≤ 20 mol%, Ti species nucleate serving attraction centres for V species. • At V > 20 mol%, hydrolysed V species imprison small Ti species prohibiting nucleation. • Nucleus size significantly increases with an increase of precursor concentration. The mixed vanadium-titanium oxo-alkoxy (VTOA) nanoparticles were synthesized via sol-gel method in a chemical reactor with ultra-rapid micromixing. The nucleation and growth kinetics and particles size, followed by the static/dynamic light scattering methods, were quite different from those of pure oxo-alkoxy titanium (TOA) and vanadium (VOA) species. It was shown that the TOA species appear first and serve to be centres of attraction for hydrolysed VOA species at the nucleation stage. However, at the vanadium content above 20 mol% large VOA species imprison sub-nucleus TOA species prohibiting the nucleus appearance. The model analysis of the VTOA induction kinetics validated a significant increase of the nucleus size with an increase of the precursor concentration. The results support a new paradigm of the sol-gel process describing profound restructuring of the oxometallic species during assembling at the nucleation stage. [ABSTRACT FROM AUTHOR]

This is a report on the antibacterial activity of ZnO and CuO nanoparticles synthesized via sol-gel method. The studies were performed on Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Pseudomonas aeruginosa bacteria using disc and well diffusion methods, bioluminescence and optical density analysis. The results show a strong decline of bacterial strains after a short contact with nanoparticles. The modelling allowed clarifying the bacterial sensitivity of toxic agents at different stages of their population evolution kinetics. It was concluded that the bacterial suppression is most effective at the exponential growth phase while it is of a lower effectiveness at the lag and stationary phases. The CuO and ZnO nanoparticles showed comparable effectiveness at the exponential growth phase. In the same time, ZnO was almost inactive at the lag phase and of lower effectiveness at the stationary phase, at which CuO conserved a significant activity. • ZnO and CuO nanoparticles of 3 nm size were synthetized using acetate precursors. • CuO and ZnO nanoparticles showed antibacterial effect. • Bacterial sensitivity to toxic agents changes at different stages of growth. • Antibacterial activity of CuO is generally stronger than that of ZnO. [ABSTRACT FROM AUTHOR]