Mixed Metal Oxide W-TiO2 Nanopowder for Environmental Process: Synergy of Adsorption and Photocatalysis

A mixed metal oxide W-TiO2 nanopowder photocatalyst was prepared by using the sol-gel method with a broad range of elemental compositions x = CW/(CW + CTi), including TiO2 and WO3. The material was structurally characterized and evaluated in adsorption and photocatalytic processes by testing its removal capacity of a representative pollutant methylene blue (MB) in aqueous solutions and under UV-A and sunlight illuminations. The nanopowders appeared to be more effective adsorbents than pure TiO2 and WO3 materials, showing a maximum at 15 mol% W, which was set as the tungsten solubility limit in anatase titania. At the same time, the photocatalytic decomposition of MB peaked at 2 mol% W. The examination of different compositions showed that the most effective MB removal took place at 15 mol% W, which was attributed to the combined action of adsorption and heterogeneous photocatalysis. Moreover, MB decomposition under sunlight was stronger than under UV-A, suggesting photocatalyst activation by visible light. The pollutant removal efficiency of the material with 15 mol% W was enhanced by a factor of ~10 compared to pure TiO2 at the beginning of the process, which shows its high potential for use in depollution processes in emergency cases of a great pollutant leak. As a result, a Wx=0.15-TiO2 catalyst could be of high interest for wastewater purification in industrial plants.

Effects of Surface Chemical Modification by Ethoxysilanes on the Evolution of 3D Structure and Composition of Porous Monoliths Consisting of Alumina Hydroxide Nanofibrils in the Temperature Range 25-1700 °C

Bulk nanomaterials with an open porosity offer exciting prospects for creating new functional materials for various applications in photonics, IR-THz optics, metamaterials, heterogeneous photocatalysis, monitoring and cleaning toxic impurities in the environment. However, their availability is limited by the complexity of controlling the process of synthesis of bulk 3D nanostructures with desired physicochemical and functional properties. In this paper, we performed a detailed analysis of influence of a silica monolayer chemically deposited on the surface of a monolithic ultraporous nanostructure, consisting of a 3D nanofibril network of aluminum oxyhydroxide, on the evolution of structure and morphology, chemical composition and phase transformations after heat treatment in the temperature range of 20-1700 °C. The experimental results are interpreted in the framework of a physical model taking into account surface and volume mass transport and sintering kinetics of nanofibrils, which made it possible to estimate activation energies of the surface diffusion and sintering processes. It is shown that the presence of a surface silica monolayer on the surface affects the kinetics of aluminum oxyhydroxide dehydration and inhibits diffusion mass transfer and structural phase transformations. As a result, the overall evolution of the 3D nanostructure significantly differs from that of nanomaterials without surface chemical modification.

Antibacterial Activity Evaluation of ZnO, CuO, and TiO2 Nanoparticles in Solution and Thin Films

This chapter introduces unique methodology of antibacterial activity evaluation of nanoparticles in both solution and thin films. Nanoparticles of ZnO, TiO₂, 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.

Polymerization initiation of pure 2-hydroxyethylmethacrylate under shock wave compression

The ability to initiate chemical reactions without the need for potentially hazardous solvents, catalysts and radical initiators is of key importance for modern biotechnologies and medicine.

Photocatalytic activity of TiO2-P25@n-TiO2@HAP composite films for air depollution

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.

[A COMPARISON OF RESULTS BETWEEN HOOK PLATE AND TIGHTROPE FOR ACUTE ACROMIOCLAVICULAR JOINT DISLOCATION]

Purpose the study - despite of this fact that there are different surgical techniques to treat acromioclavicular dislocation and also the surgery remains controversial, the purpose of our study is to compare the results of surgery treatment to acromioclavicular joint dislocation on the condition of surgical method: Hook Plate versus TightRope. Between 2015 and 2019, 30 patients were with acute Rockwood type III-VI acromioclavicular dislocation at the age of 23-54. Patients were divided into 2 groups according to the surgical methods (Hook plate: n=15; TightRope: n=15)to compare the functional outcome after using either Hook plate and TightRope stabilization. Patients were evaluated using Constant Score and radiography. Comparing the functional results, were observed some differences between the two groups. According to Constant Score the results were: Hook plate - 78.5, TightRope - 81.4. 14 patients in the hook plate group were reoperated to remove the device, except 1 patient who refused to be reoperated. There was insignificant difference between both groups regarding severity pain. The majority of tightrope group (70%) regained their normal functional activities, whereas only 40% of the hook plate patients did (р<0.001)/ About half (50%) of the tightrope group in comparison with 30% of hook plate group had active forward flexion more than 150° (р<0.01). Both groups showed no significant differences regarding degree of muscle strength, patients' satisfaction, and total outcome. Both operative methods are effective techniques and could be recommended to treat an acute acromioclavicular joint dislocation. Between the two groups are no significant differences. However, TightRope fixation provides a low rate of failure and complications and avoids the need for second surgery to remove the implant.

Effect of Light Intensity on the Free-Radical Photopolymerization Kinetics of 2-Hydroxyethyl Methacrylate: Experiments and Simulations

The effect of UV light intensity on the kinetics of free-radical polymerization of 2-hydroxyethyl methacrylate (HEMA) triggered with the phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) photoinitiator was investigated experimentally and theoretically. The temporal evolution of the conversion yield and polymerization rate was followed by Raman spectroscopy. The experimental data were treated with a kinetic model, which takes into account significant diffusion-controlled processes and termination pathways including bimolecular reaction and primary radical termination. This model showed very good agreement with the experiment in a large range of UV light intensities and shed light on the termination process. In particular, it was shown that the primary radical termination is dominant for relatively low light intensities below 1 mW/cm², when the photoinitiator is weakly consumed during the polymerization process.

Antibacterial activity of ZnO and CuO nanoparticles against gram positive and gram negative strains

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.

Synthesis of organic-inorganic hybrids via a high-pressure-ramp process: the effect of inorganic nanoparticle loading on structural and photochromic properties

Organic polymerization remains a limiting step in the preparation of organic-inorganic hybrid materials with a strong concentration of the inorganic component. In this work, a high-pressure-ramp process was applied to achieve pHEMA-TiO₂ nanoparticulate solids with an unprecedentedly high concentration (12 mol l^-1) of the inorganic component, which is four times higher than that obtained after radical polymerization induced thermally or by photons. The inorganic nanoparticles underwent morphological and structural changes with an increase of Ti concentration above 1.5 mol l^-1: they slightly coarsen and crystallize into an anatase polymorph. The material possesses a strong photochromic response related to the electron-hole separation at the organic-inorganic interface and can store 1e^- per 5 Ti atoms. The electron storage capacity of the titania nanoparticles decreases upon crystallization.

Transport-based model for turbulence-corrupted imagery

A new model for turbulence-corrupted imagery is proposed based on the theory of optimal mass transport. By describing the relationship between photon density and the phase of the traveling wave, and combining it with a least action principle, the model suggests a new class of methods for approximately recovering the solution of the photon density flow created by a turbulent atmosphere. Both coherent and incoherent imagery are used to validate and compare the model to other methods typically used to describe this type of data. Given its superior performance in describing experimental data, the new model suggests new algorithms for a variety of atmospheric imaging and wave propagation applications.

From nanoparticles to bulk crystalline solid: nucleation, growth kinetics and crystallisation of mixed oxide ZrxTi1−xO2 nanoparticles

We describe the preparation of mixed metal oxide nanoparticles of a desirable composition and their transformation to the crystalline solids Zr_xTi_1−xO₂ (0.0 ≤ x ≤ 1.0) after heat treatment.

A New Route for High-Purity Organic Materials: High-Pressure-Ramp-Induced Ultrafast Polymerization of 2-(Hydroxyethyl)Methacrylate

The synthesis of highly biocompatible polymers is important for modern biotechnologies and medicine. Here, we report a unique process based on a two-step high-pressure ramp (HPR) for the ultrafast and efficient bulk polymerization of 2-(hydroxyethyl)methacrylate (HEMA) at room temperature without photo- and thermal activation or addition of initiator. The HEMA monomers are first activated during the compression step but their reactivity is hindered by the dense glass-like environment. The rapid polymerization occurs in only the second step upon decompression to the liquid state. The conversion yield was found to exceed 90% in the recovered samples. The gel permeation chromatography evidences the overriding role of HEMA2(••) biradicals in the polymerization mechanism. The HPR process extends the application field of HP-induced polymerization, beyond the family of crystallized monomers considered up today. It is also an appealing alternative to typical photo- or thermal activation, allowing the efficient synthesis of highly pure organic materials.

Tunable Electromagnetic Coupling in Plasmonic Nanostructures Mediated by Thermoresponsive Polymer Brushes

A smart and highly SERS-active plasmonic platform was designed by coupling regular arrays of nanotriangles to colloidal gold nanorods via a thermoresponsive polymer spacer (poly(N-isopropylacrylamide), PNIPAM). The substrates were prepared by combining a top-down and a bottom-up approach based on nanosphere lithography, surface-initiated controlled radical polymerization, and colloidal assembly. This multistep strategy provided regular hexagonal arrays of nanotriangles functionalized by polymer brushes and colloidal gold nanorods, confined exclusively on the nanotriangle surface. Interestingly, one could finely tune the gold nanorod impregnation on the polymer-coated nanostructures by adjusting the polymer layer thickness, leading to highly coupled plasmonic systems for intense SERS signal. Moreover, the thermoresponsive properties of the PNIPAM brushes could be wisely handled in order to monitor the SERS activity of the nanostructures coupled via this polymer spacer. The coupled hybrid plasmonic nanostructures designed in this work are therefore very promising smart platforms for the sensitive detection of analytes by SERS.

Laser-assisted high-pressure-induced polymerization of 2-(hydroxyethyl)methacrylate

We report on a successful room-temperature polymerization of 2-(hydroxyethyl)methacrylate (HEMA) under high pressure. The polymerization is observed in a limited range of pressures 0.1 to 1.6 GPa without the use of any initiator. When the compressed sample is irradiated at 488 or 355 nm by a laser, the polymerization reaction rate is increased by a factor of 10 or 30, respectively. Moreover, the shift of the laser wavelength to the UV improves the polymerization yield of the recovered sample to 84%. The catalysis of the polymerization process by light results from a one-photon-assisted electron transfer to π* antibonding states of the monomer molecule. The observed polymerization is irreversible and almost complete, which makes this synthesis process suitable for applications.

Nucleation and growth kinetics of zirconium-oxo-alkoxy nanoparticles

Nucleation and growth of zirconium-oxo-alkoxy nanoparticles were studied in a sol–gel process in n-propanol solution in quasi-perfect micromixing conditions.

Characteristics of nanostructured ZnO layers deposited in spray plasma device

ZnO and Al doped ZnO thin film have been deposited on glass substrate by "spray plasma" process using an aqueous solution of Zn(NO3)2. XRD patterns revealed polycrystalline character with the typical hexagonal würtzite structure. The preferential c-axis orientation of crystallites depends highly on the operating conditions. Willamson-Hall method and AFM photographs showed a size of crystallites ranging between 20 and 80 nm and a roughness between 6 and 50 nm. Films exhibit a transmittance between 65 and 90% in the visible region. XPS revealed that the stoichiometry of deposited ZnO is Zn/O = 0.93. Fluorescence spectroscopy showed the presence of two bands at 360 nm (UV) and at 410 nm (Blue). The UV band can be attributed to exiton emission. Another important result concerns the non-existence of a "green" band at 500 nm.

Novel nanostructured pHEMA-TiO2 hybrid materials with efficient light-induced charge separation

We report on a new approach to the fabrication of an electronic material: organic-inorganic pHEMA-oxo-TiO(2) hybrid with efficient light-induced separation of charges. Particular attention is paid to the material nanoscale morphology. The size-selected 5.0 nm titanium oxo-alkoxy nanoparticles are prepared in a sol-gel reactor with rapid (turbulent) fluid micromixing and the ligand exchange results in a stable nanoparticulate precursor in HEMA solution, in which polymerization can be induced thermally or by photons. The obtained hybrid materials demonstrate the highest quantum yield of photoinduced charge separation of 50% and can store photoinduced electrons at a number density above 10% Ti atoms.

Raman study of oriented ZnO thin films deposited by sol-gel method

ZnO films with preferred orientation along the (0 0 2) plane were successfully deposited by the sol-gel method using Zn(CH3COO)2.2H2O as starting material and inorganic precursor. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and monoethanolamine. Thin films are obtained by spin-coating on glass substrates. ZnO films were obtained by preheating the spin-coated films at 300 degrees C for 10 min after each coating and postheating upto 550 degrees C for 2h. The as-deposited films are transformed into mono-oriented ZnO upon thermal treatment. The films consist of spongy particles aggregates with an uniform size and homogenous surface. The films aim to be used in optoelectronic devices. Raman spectroscopy from ZnO films and deposit solutions has been investigated. New Raman results of the deposit solution suggest that Zn-O bond forms first in solution and that these entities play the role of germs initiating the crystallization mechanisms during films annealing. Raman spectra of the annealed films show the presence of a compressive stress within the film structure.

Supercontinuum assisted trapped electron accumulation in titanium oxide gel by femtosecond laser pulses

Long-lived trapped electrons are generated in titanium oxide gels in a convergent part of a loosely focused beam from a millijoule, femtosecond Ti:Sapphire laser. The appearance of trapped electrons is accompanied by the generation of the white supercontinuum. Considering the relevant physical mechanisms of trapped electron accumulation, we show that two-photon interband transitions with participation of photons at the fundamental frequency and from the blue part of the supercontinuum explain the experimental findings.

Chemical Activity of Photoinduced Ti3+ Centers in Titanium Oxide Gels

We report on the chemical activity of trapped electrons in wet titanium oxide gels. These electrons are generated under the band gap irradiation of gels in the spectral range between 3.25 and 4.4 eV and stored as Ti3+ centers that absorb in the visible. Chemical processes in photoirradiated gels are generally similar to those earlier reported in TiO2 colloids; however, peculiarities exist. In particular, a high internal surface of gels strongly enhances interface reactions. Measurements of UV-visible absorption kinetics allow conclusions to be made about extremely high available traps concentration and the activity of all trapped electrons toward nitrate and nitrite anion reduction according to a heterogeneous photocatalytic mechanism.

Nonlinear dynamics associated with a model of vector four-wave mixing

The nonlinear dynamics of doubly-degenerate vector four-wave mixing (FWM) are studied analytical and numerically, in phase space and in Stokes space. Depending on the initial conditions, vector FWM can evolve aperiodically or periodically, but not chaotically. The dynamics of vector FWM are similar to, but richer than, the dynamics of scalar FWM.

Light-induced charge separation and storage in titanium oxide gels

We report on the interaction of light with a particular class of media--wet gels, which in contrast to sols of nanoparticles possess a macroscopic bulk structure, and which differ from conventional solids by the existence of the internal liquid-solid interface. We show, taking an absorption cross section of trapped electrons from Safrany, Gao, and Rabani [J. Phys. Chem. B 104, 5848 (2000)], that a separation of charges with quantum efficiency as high as 46% appears under the band-gap irradiation of titanium oxide gels: electrons are stored in the gel network as Ti3+ centers, whereas holes are stored in the liquid phase. Under a prolonged UV-laser irradiation, more than 14% of Ti4+ centers can be converted into Ti3+ . Their lifetime can be extremely long and exceeds months at room temperature. The trapped electrons are responsible for a "dark" absorption continuum covering the spectral range from 350 nm to 2.5 mum .

Four-wave mixing in fibers with random birefringence

Parametric amplification is made possible by four-wave mixing. In low-birefringence fibers the birefringence axes and strength vary randomly with distance. Light-wave propagation in such fibers is governed by the Manakov equation. In this paper the Manakov equation is used to study degenerate and nondegenerate four-wave mixing. The effects of linear and nonlinear wavenumber mismatches, and nonlinear polarization rotation, are included in the analysis. Formulas are derived for the initial quadratic growth of the idler power, and the subsequent exponential growth of the signal and idler powers (which continues until pump depletion occurs). These formulas are valid for arbitrary pump and signal polarizations.

Isotopic effect on the cage-induced quenching of OH(A)/OD(A) inside small argon clusters

In this paper we report on the isotopic effect on the cage-induced excited-state quenching inside small Ar(m) clusters (m<10(2)) solvated in large Ne(N) clusters (N approximately 7.5x10(3)). Excited OH(A)/OD(A) fragments are produced by photodissociation of H2O and D2O molecules and the quenching agents are correspondingly H or D atoms. The decrease of the fluorescence yield with the size of the cluster m>m0 is observed in both cases and it is attributed to the formation of the cage of argon atoms around the doped molecule. Interestingly, more atoms are needed to induce the fluorescence quenching of OD*(A) fragments, m0=21+/-3, compared to the electronically excited state quenching of OH*(A) molecules, 11+/-2. A diffusion model containing two free parameters, the quenching cross section sigmaq and the number of argon atoms forming the cage m0, explains the effect in terms of the residence time of the hydrogen atom inside the cage. We suggest that the melting of the doped rare gas clusters is responsible for the different predissociation dynamics. The quenching cross section obtained from the experimental data is in good agreement with former experiments.