Two-zero Majorana textures in the light of the Planck results

The recent results of the Planck experiment put a stringent constraint on the sum of the light neutrino masses, m1+m2+m3 < 0.23 eV (95 % CL). On the other hand, two-zero Majorana mass matrix textures predict strong correlations among the atmospheric angle and the sum of the masses. We use the Planck result to show that, for the normal hierarchy case, the texture with vanishing (2,2) and (3,3) elements is ruled out at a high confidence level; in addition, we emphasize that a future measurement of the octant of the atmospheric mixing angle (or the one sigma determination of it based on recent fit to neutrino data) will put severe constraint on the possible structure of the Majorana mass matrix. The implication of the above mentioned correlations for neutrinoless double beta-decay are also discussed, for both normal and inverted orderings.Comment: 9 pages, 8 figure

‘SOSpesa’–Service Design Leveraging Neighborhood Solidarity Networks to Tackle Food Poverty, Food Surplus, and Sustainability of Local Commerce

This paper illustrates a project to redesign a charitable initiative against food poverty into an innovative solution called "SOSpesa", implemented in a neighborhood of the city of Milan named NoLo - North of Loreto. The paper outlines approach, methodology and strategy to move from an activist initiative to a service with more than charitable purposes and outlines the new service configuration in its opportunities and limitations as emerged from the pilot project. It focuses on strategies to harness a network of neighborhood actors to achieve a goal of solidarity, combating food waste and supporting local shops. Based on the assumption that the local context is a strength of the service, the project activated a wide range of actors, from volunteers to third sector organizations and businesses, under the coordination of a team of researchers, to experiment with different service configurations in search of overall sustainability. Finally, the paper discusses design strategies for scaling up grassroots social innovation through replicability, not to distort its spirit and bottom-up engagement

Wetting Modification by Photocatalysis: A Hands-on Activity To Demonstrate Photoactivated Reactions at Semiconductor Surfaces

We present a hands-on activity designed for advanced physical chemistry courses for Master\u2019s students on the application of photocatalysis to the modification of the surface properties of a semiconductor (titanium dioxide). The wetting properties of TiO2 films, deposited from commercial powders, are studied before and after UV irradiation. Irradiation-induced superhydrophilicity is exploited to provide antifogging properties. The TiO2 films are then functionalized with a perfluorinated alkylsilane to impart superhydrophobicity and subsequently lithographed by irradiation through a photomask: the photocatalytic degradation of the organic chains in the irradiated areas leads to a wetting contrast that can be revealed using dye solutions. This experience can be easily adapted to be suited for undergraduates or high-school students as well as to demonstrations for science festivals

NANOSTRUCTURED SEMICONDUCTOR FILMS: SYNTHESIS, SURFACE FUNCTIONALIZATION AND INNOVATIVE APPLICATIONS

In recent years, photoactive semiconductors have received ever growing interest, as testified by the remarkable number of related publications, thanks to their promising applications in manifold fields such as environmental remediation and photovoltaics. Among the photoactive semiconductors, titanium dioxide has been by far the most investigated owing to its cheapness, non-toxicity and stability to photocorrosion. Titanium dioxide can be successfully applied to the photocatalytic remediation of air and water pollutants, H2 production from water splitting, and in solar light harvesting using second generation solar cells; it is a biocompatible material, and it can be employed to obtain self-cleaning surfaces. Although a few commercial applications employing nanometric TiO2 are already on the market, many issues still remain to be addressed to obtain efficient, reliable and durable materials. The present thesis work focuses onto the synthesis and the study of the physicochemical properties of nanometric TiO2. My research activity has focused on two main subjects, one more applicative and the other more fundamental. The first part was devoted to the photocatalytic applications of TiO2. Photocatalytic oxidation of pollutants is one of the most promising technologies in environmental protection and remediation, especially for the removal of low concentration pollutants in slightly contaminated enclosed atmospheres. Nanometric titania has been successfully applied to the photo-oxidation/reduction of numerous organic and inorganic pollutants, both in gaseous phase and in solution. Several concretes and paintings containing nanometric titania that photo-oxidize pollutants are already on the market, but many disadvantages remain to be overcome in order to obtain commercially successful products. Hence, the first part of my research was directed towards the improvement of the photocatalytic activity of TiO2 to obtain more efficient photocatalysts for the degradation of environmental pollutants. The photocatalytic activity of titania is strongly affected by its particles\u2019 physicochemical features, which, in their turn, are imposed by the synthetic path adopted for the material preparation. Therefore, it is essential to tailor the physicochemical characteristics of titania particles using an appropriate synthetic procedure in order to obtain highly active samples. A considerable part of my PhD project was devoted to the optimization of several synthetic procedures in order to produce TiO2 powders and films with tailored optical, morphological and electronic features. One of the main disadvantages of TiO2 is its large band gap (3.2 eV for anatase, 3.0 eV for rutile), which corresponds to a light absorption in the UV region. Thus, currently TiO2 based materials require UV irradiation in order to activate the photocatalytic process. As only 5% of solar light is in the UV region, a shift towards visible absorption is required to improve the photocatalytic activity of TiO2 under solar irradiation. The introduction of non-metal ions in the TiO2 lattice represents one of the most promising approaches to induce a bathochromic shift, i.e., a shift of the absorption edge of TiO2 to longer wavelengths, and consequently increase the photocatalytic response of doped samples into the visible region. Therefore, during my thesis, I synthesized several doped samples with non-metals such as N, in order to assess if a bathochromic shift effectively leads to a higher photocatalytic activity in the visible region and, more important, under solar irradiation. N-doped TiO2 samples were obtained from different titania precursors (Ti(Oi-Pr)4, TiCl3) and adopting different N-sources (ammonia, triethylamine, tea). All obtained samples were exhaustively characterized, in order to obtain a complete picture of the modifications induced in the titania structure and surface features by the modifications of the synthetic pathway. Samples were characterized from the structural, morphological, electrochemical, optical and compositional point of view. Moreover, other features, such as magnetic properties, were determined and ab initio calculations of the electronic properties of the doped samples were performed. All N-doped samples showed a broad absorption in the visible region which was traced back, on the grounds of first principles calculations, to the formation of localized intragap electronic levels. Sample thin films were tested for their photocatalytic activity, under UV, visible and simulated solar irradiation, towards the degradation of gas phase ethanol and acetaldehyde. The most active N-doped sample, both under UV and solar irradiation, was the oxide showing the largest amount of paramagnetic N_b^\u2022 species. Under visible irradiation instead, the sample with the largest activity was the one showing the narrowest apparent band gap and the concomitant presence of anatase and brookite polymorphs, which might hinder charge recombination processes. The structure of N-doped samples was elucidated not only by ordinary powder diffraction, but also by means of synchrotron radiation, using Extended X-ray Absorption Fine Structure (EXAFS) to understand the position of dopant ions inside the TiO2 crystal lattice. These data were obtained during a short research stay at the European Synchrotron Radiation Facility (ESRF) in Grenoble. Average Ti nearest neighbors distances were obtained from EXAFS experiments and compared with Density Functional Theory (DFT) calculations, showing that N substitutes oxygen at low levels of doping, whereas oxygen vacancy creation is observed at higher dopant concentrations. Another strategy to improve the photocatalytic activity of TiO2 involves the enhancement of the adsorption and diffusion of pollutants into TiO2. In this respect, I investigated the effect of the modification of TiO2 morphology to obtain mesoporosity via different template syntheses. Mesoporous materials have been consistently proposed to produce better performing catalysts in many fields of catalysis. Here, the morphologic features of titania particles were tailored by using soft templates, in order to obtain materials with a high degree of porosity in the mesoporosity range. Two classes of soft templates were investigated: alkylpyridinium surfactants and block copolymers of the Pluronic family. As for the first class, both monomeric (dodecylpyridinium chloride, DPC) and dimeric gemini-like surfactants (gemini spacer 3, GS3) were employed. Mesoporous TiO2 samples were synthesized by a classical sol-gel route followed by an hydrothermal growth in the presence of one of the structure directed agents. The surfactant/oxide interactions at the solid/liquid interface were evaluated by adsorption isotherms, showing marked differences between the two surfactants. While DPC exhibited weak adsorbate/adsorbent interactions and weak self-aggregation tendency, resulting in the formation of very small, globular micelles, GS3 instead showed strong interactions with the TiO2 surface and the formation of elongated rods and further hexagonal arrangements could be proposed. Such different behaviors lead to significant diversities in the porous structure of the TiO2 samples. The small pores generated by the DPC micelle tend to collapse because of the heat of combustion generated during the surfactant removal step at 600 \ub0C. On the contrary, GS3 leads to a significant fraction of pores in the mesoporosity range. However, the use of cationic surfactants has an intrinsic limitation: high calcination temperatures are required to remove entirely the template. Such harsh conditions markedly reduce the surface area of the oxide due to particle sintering and crystal growth. Non-ionic structure directing agents, such as amphiphilic block copolymers, can be instead completely removed at much lower temperatures. Three block copolymers of the Pluronic family, characterized by different micelle size in water as determined by light scattering analysis, were employed to induce mesoporosity in nano-TiO2. The surfactants were removed by combining UV and thermal treatments in order to avoid pore collapse while obtaining a good oxide crystallinity. Obtained samples presented a high surface area and significant fraction of pores in the mesoporosity range. A good correlation was observed between the sequence of average pore size in mesoporous TiO2 and the micelle size of the used copolymer. A fine modulation of pore size and total volume was obtained by changing polymer type and concentration, effectively enhancing the photocatalytic properties of the oxide towards the degradation of methylene blue. The mesoporous oxides were also used as scaffolds to obtain Bi-promoted TiO2, resulting in a further increase of the photocatalytic performance (see below). Another limitation of TiO2 as photocatalyst is its low quantum yield. Among the factors that concur to reduce the titania photocatalytic efficiency, the recombination of photogenerated electrons and holes plays a leading role by competing with the transfer of photogenerated charges to species adsorbed at the photocatalyst surface. Quantum yields could thus be improved by slowing down such recombination processes. The use of metal particles or mixed oxides with a suitable band structure has been proposed to slow down the recombination process. In fact, if the metal/second oxide has an available electronic level just below the conduction band of TiO2, electrons photogenerated on TiO2 are prompted to migrate to the metal/second oxide, thus enhancing the charge separation and slowing down the recombination process. Noble metals, such as Pt, have been extensively studied in the literature for this purpose and they have proven to be highly effective in enhancing the TiO2 photocatalytic activity. In my work, Bi2O3 was investigated as a cheaper alternative to noble metals to enhance the photocatalytic performances of TiO2. Bi2O3 is non-toxic and environmentally friendly material which, thanks to its band structure, could trap photo-generated electrons, and thus improve the overall quantum efficiency of the material. Theoretical calculations have shown that the specific band structure of Bi2O3-TiO2 could significantly improve the oxide photocatalytic efficiency. In my study, Bi2O3 was allowed to form into the mesoporous network of TiO2 samples obtained by surfactant template synthesis. The obtained materials were characterized by X-ray diffraction (XRD), N2 adsorption at subcritical temperatures (BET), high resolution transmission microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, and zeta potential determinations, providing an insight into the composite structure and into the specificity of the Bi2O3-TiO2 composites with respect to traditional sol-gel TiO2 nanomaterials. All samples were tested for the photocatalytic degradation of methylene blue stains and of formic acid under dry and wet conditions, respectively. The presence of Bi promotes the photocatalytic activity of the final samples in both tested reactions. Photocurrent measurements of Bi2O3-TiO2 composites were performed in order to assess any effect of the Bi addition on the fate of the photogenerated electron-hole pair. The obtained results agree with the observed marked enhancement in photocatalytic activity of the Bi2O3-TiO2 samples, showing an increased recombination time of photogenerated charges in Bi2O3-TiO2 composites. This effect may be related to the finely dispersed nature of Bi2O3 within the mesoporous network of the TiO2 scaffold. A crucial aspect that needs to be addressed for the commercial application of TiO2 materials is their reusability, which is strictly connected to their efficiency in removing recalcitrant compounds. Real life effluents often contain a mixture of pollutants, some of which can be highly recalcitrant compounds. It has been observed that such recalcitrant pollutants or their degradation intermediates can strongly adsorb onto the TiO2 surface, irreversibly poisoning the photocatalyst. The deposition of titania particles in a thin layer is essential for the material applications because it simplifies the separation of the photocatalyst from the effluents and optimizes photon absorption. However, by reducing the available surface area, the deposition in films markedly increases the poisoning effects. A possible strategy to tackle this issue is the combination of photocatalysis with other oxidation techniques, in particular advanced oxidation techniques. In this thesis work, a combination of photocatalysis by TiO2 films and ozonation treatments was studied to achieve the complete oxidation of highly recalcitrant pollutants such as bisphenol A and cumylphenol. A specific deposition procedure of the TiO2 film onto a rough Al support was developed in order to obtain photocatalytic films with high surface area and good mechanical stability. Photocatalytic ozonation was compared to the separate photolytic, photocatalytic, and ozonation techniques to investigate the synergistic processes taking place in the combined treatment. The combination of the two treatments leads to synergistic effects that dramatically enhance the final mineralization of the pollutants. Moreover, the degradation pathway taking place during the photocatalytic ozonation of bisphenol A and 4-cumylphenol was studied by combining HPLC\u2013MS determinations and FTIR analyses of the used catalyst. The knowhow gained in the field of oxide synthesis and photocatalysis was then exploited in the development of oxide-based materials with tailored surface properties by means of surface functionalization with siloxanes. In recent years, hydrophobic modification of oxide surfaces has attracted growing attention because of its vast technological relevance. Siloxanes, compounds with the general formula R-(CH2)n-Si-(OR\u2019)3, are among the functionalizing agents employed to modulate the surface energy, wettability and adhesion properties of oxides, thanks to their ability to form durable bonds with inorganic compounds, upon hydrolysis of labile \u2013OR\u2019 groups. Furthermore, siloxanes may serve as robust coupling agents between organic materials and the oxide for the preparation of a new class of hybrid nanocomposites showing interesting photophysical properties and applications. Firstly, the role played by the structure of the siloxane molecule onto the wetting features of a smooth surface was investigated. The surface energy of different hydrophobing molecules, both fluorinated and unfluorinated, deposited in smooth layers over an inert substrate, was determined by analyzing contact angle values with literature models. The obtained values were compared with dipole moments determined by theoretical calculations employing semiempirical Hamiltonians, finding a close correlation between the calculated dipole moments and the polar components of the surface energy. Siloxanes were then employed to functionalize TiO2 nanoparticles, in order to obtain rough composite films. The functionalization of nanometric TiO2 with siloxanes is even more promising as it has lead to a series of applications uniquely related to the peculiar features of this oxide. For instance, the photocatalytic activity of TiO2 can be exploited to create hydrophobic/hydrophilic patterns by irradiating a siloxane-TiO2 film with UV light through a suitable photomask, a procedure known as photocatalytic lithography. The siloxane is photocatalytically degraded in the areas exposed to UV light, while the siloxane monolayer remains intact in the areas covered by the photomask. The resulting hydrophobic/hydrophilic pattern can be exploited in numerous applicative fields, for example to promote the site selective condensation of water from the gas phase or the site specific adsorption of hydrophilic/hydrophobic molecules. In this study, the TiO2 surfaces functionalized by different siloxanes were tested in self-cleaning experiments. Further, patterned structures with tunable hydrophobic and oleophobic patches were obtained by exploiting the photocatalytic activity of TiO2 films. The resulting wetting contrast was exploited to obtain a site selective adsorption of a dye molecule, with a procedure that can be adapted to the site selective deposition or growth of a large variety materials, such as semiconductor quantum dots, polymers or biological molecules. Notwithstanding the great interest and the manifold applications of these composite materials, the attachment of hydrophobizing molecules at TiO2 surfaces still remains poorly understood at the molecular level and hardly discussed in the literature. My research activity was aimed at filling the gap by investigating the fundamental features of bonding and structure of the siloxane layers onto TiO2 nanoparticle films. The influence of the siloxane amounts on the wettability and self-cleaning properties of TiO2 was studied, together with the role played by the hydrophobing molecule structure (aliphatic vs. aromatic side-chain, linear vs. branched, length of the side-chain, fluorinated vs. un-fluorinated molecules). The studied siloxanes were both commercial and laboratory-made, the latter synthesized by the research group of Prof. Benaglia (Dipartimento di Chimica, Universit\ue0 di Milano). The modes of attachment of siloxane molecules at the TiO2 surface were investigated by combining data of CP/MAS NMR with ATR-FTIR and XPS analyses, giving a detailed picture of the siloxane layer structure and interaction with the oxide. It appears that the attachment modes of silicon, besides changing with the siloxane content of the surface, are markedly affected by the siloxane structure. For instance, alkyl trifunctional siloxanes give rise, starting for low oxide coverage (9% w/w), to continuous functionalized layers in which silicon atoms are progressively bound by one, two, or three groups, these being either \u2013 O\u2013Ti or \u2013O\u2013Si. These films are uniform and highly hydrophobic showing excellent self-cleaning properties at low contents; they present a Cassie-Baxter wetting behavior in which water drops float over a composite solid-gas carpet. The substitution of the alkyl chain with aromatic end groups favors localization versus spreading for the siloxanes, due to \u3c0-\u3c0 stacking interactions. In these cases, the films, which are locally ordered, are less uniform on the whole. The bifunctional biaryl compound gives rise to layers which are initially, i.e., at low coverage, hydrophilic and end up to be hydrophobic at higher coverage. These are characterized by patch-wise localizations producing a wettability in which the water drops spread following the surface rough profile. Therefore, the structure of the siloxane appears to be a key parameter tuning the features of wettability of the surface by water. Siloxanes are employed not only to modulate the wettability of oxides, but they can be exploited as linkers to attach new functionalities, such as dyes, biological molecules, and nanoparticles, to the oxide surface. By patterning the siloxane monolayer, a site-selective functionalization of the oxide surface can be obtained. Among the available patterning techniques, probe-based electro-oxidative lithography offers one of the best lateral resolution available (line width as narrow as 30 nm). So far, this technique has been applied almost exclusively to Si substrates. In order to fully exploit this technique, its application to other technologically relevant substrates is required. In the present thesis, probe-based electrooxidative lithography of octadecyltrichlorosilane (OTS) monolayers adsorbed on TiO2 and indium tin oxide (ITO) are reported for the first time. The conductivity of the layer and the environmental humidity are critical parameters, affecting the stability of the water meniscus between the probe and the substrate and thus the electro-oxidation process. The resulting surface functionalization was exploited to obtain the site selective growth of metal nanoparticles. The electro-oxidation mechanism was studied by advanced characterization techniques such as Scanning Kelvin Probe Microscopy (SKPM), and the oxidation processes taking place on Si, ITO and TiO2 were compared. For instance, in the case of OTS-ITO, a local overoxidation of the ITO substrate occurs simultaneously to the monolayer oxidation, whereas in OTS-TiO2, no overoxidation of the oxide substrate takes place. This latter part of the work was carried out as collaboration between the group I belong to (Prof. Ardizzone\u2019s group of the Universit\ue0 degli Studi di Milano) and the group of Prof. Schubert of the Friedrich-Schiller Universit\ue4t, Jena (Germany), where I spent a 5-month research period followed by several short stays

Implementation of the Hierarchical Reference Theory for simple one-component fluids

Combining renormalization group theoretical ideas with the integral equation approach to fluid structure and thermodynamics, the Hierarchical Reference Theory is known to be successful even in the vicinity of the critical point and for sub-critical temperatures. We here present a software package independent of earlier programs for the application of this theory to simple fluids composed of particles interacting via spherically symmetrical pair potentials, restricting ourselves to hard sphere reference systems. Using the hard-core Yukawa potential with z=1.8/sigma for illustration, we discuss our implementation and the results it yields, paying special attention to the core condition and emphasizing the decoupling assumption's role.Comment: RevTeX, 16 pages, 2 figures. Minor changes, published versio

Ultrasound-enhanced photodegradation of Diclofenac Na

Diclofenac sodium, a non-steroidal anti-inflammatory drug, is an emerging water pollutant that cannot be removed by conventional wastewater treatment plants. Combined processes based on hydrodynamic cavitation (sonolysis) and heterogeneous photocatalysis are highly promising for the degradation and mineralization of refractory drugs [1,2]. Nevertheless, the use of nanoparticles as photocatalyst is not suitable in real applications for environmental and health hazard [3] as well as for the complex photocatalyst retrieval at the end of the process. For this reasons, we studied the photocatalyzed degradation of Diclofenac Na using micrometric titanium dioxide photocatalyst (Kronos 1077, 0.1 g/L), both bare and decorated with silver. Moreover, the synergic effect of pulsed ultrasound was tested. Initial concentrations of diclofenac sodium in the 25-50 ppm range were tested. Tests were performed in a batch jacketed reactor. A UVA lamp set sideway irradiated the solution with a power of 30 W/m2 and an ultrasonic horn (20 kHz) sonicated the solution. HPLC-UV and HPLC-MS determined Diclofenac degradation and the main byproducts. A total organic carbon analyzer (TOC, Shimadzu) calculated the fraction of Diclofenac mineralized. An example of photodegradation run is reported in figure. A positive synergy coupling ultrasounds with photocatalysis is confirmed, mainly with the use of Ag nanoparticles-TiO2. We observed both a faster molecule degradation and its complete mineralization

Triply green polyaniline: UV irradiation-induced synthesis of highly porous PANI/TiO2 composite and its application in dye removal

An environmentally benign procedure for the preparation of polyaniline/TiO2 composites is presented. The UV irradiation-induced synthesis leads to materials with good crystallinity and tailored morphology, showing promising sorption and recycle properties in dye removal tests. A reaction mechanism is proposed on the basis of LC-MS and FT-IR investigations

Polyaniline/TiO2 composites: green photocatalysic synthesis and application in wastewater remediation

In recent years, polyaniline (PANI) composites and nanocomposites with metal and metal-oxide materials have received growing attention for electrochemical and photoelectrochemical applications (Gu 2013). Among them, PANI/TiO2 composites are probably the most interesting systems due to synergistic effects between the conductive polymer and the oxide photocatalyst in terms of photogenerated charge separation and photocatalytic efficiency (Bae 2011). Moreover, polyaniline has been reported to possess favourable sorption properties, which can be exploited for pollutant remediation (Alcaraz-Espinoza 2015, Janaki 2012). PANI/TiO2 composites are thus promising candidates for wastewater treatment combining different pollutant remediation approaches. Polyaniline is classically synthesised via oxidative polymerization (Tran 2011), which involves noxious reagents (aniline and peroxydisulfates) and leads to toxic and carcinogenic byproducts (such as benzidine and trans-azobenzidine). In recent years, greener alternatives have been reported, such as a synthetic process starting from aniline dimer ((4-aminophenil)aniline) and using Fe3+ as catalyst and H2O2 as oxidant (Della Pina 2018). Unfortunately, this alternative procedure does not offer any control over the polymer morphology, leading to compact materials with low surface area and, as a consequence, poor dye-sorption capability. Very recently, we proposed a new photocatalytically induced green synthesis leading to stable polyaniline/TiO2 composites with porous morphology, wide surface area, high crystallinity and, most important, excellent dye removal performance and reusability (Cionti 2018). The reaction is carried out in two steps: at first, the aniline dimer is dissolved in a HCl aqueous solution and TiO2 is added while starting UV irradiation. In the second step, H2O2 is added in the dark, leading to the final product. In this work, we shed light on the photocatalytic nature of the synthetic mechanism, highlighting the different roles of TiO2 and of H2O2 on the composite structural and morphological features as well as on the composite performance for pollutant abatement. The reaction mechanism was investigated by a combination of spectrometric techniques, radical scavenger tests, and surface characterizations (Fig.1). By sampling the reaction mixture at different irradiation times, we demonstrated that under UV irradiation the growth of the oligomers occurs at the TiO2 particle surfaces. The same experiment carried out without UV irradiation showed the intrinsic photocatalytic nature of the process: in the dark, only short oligomers without appropriate chain conjugation were produced. However, even after prolonged UV irradiation, the final green product could be obtained only upon addition of H2O2, showing that, while oligomer formation is initiated by radicals produced by TiO2 photocatalysis, small amounts of an oxidant (H2O2) are still needed for the polymer chain growth. The role of the H2O2 amount proved to be especially crucial with respect to the composite properties. Increasing the H2O2 amount together with that of TiO2 led to composites with low surface area and reduced dye removal capability (Fig.2 a) due to a faster polymerization step. On the other hand, when only the photocatalyst amount was increased, neither the product morphology, nor its dye-removal ability were affected. This enables to increase the TiO2 content within the composite with the aim of enhancing its photocatalytic performance. In this respect, the composite stability was tested in water under prolonged UV irradiation, showing that the material optical, structural and morphological properties remained unchanged. The composite was tested towards the removal of anionic azo dyes in aqueous solution, evaluating the effect of the matrix composition and the composite reusability (Fig.2 b), showing promising results

Photocatalytic and oxidative synthetic pathways for highly efficient PANI-TIO2 nanocomposites as organic and inorganic pollutant sorbents

Polyaniline (PANI)-materials have recently been proposed for environmental remediation applications thanks to PANI stability and sorption properties. As an alternative to conventional PANI oxidative syntheses, which involve toxic carcinogenic compounds, an eco-friendly procedure was here adopted starting from benign reactants (aniline-dimer and H2O2) and initiated by ultraviolet (UV)-irradiated TiO2. To unlock the full potential of this procedure, we investigated the roles of TiO2 and H2O2 in the nanocomposites synthesis, with the aim of tailoring the properties of the final material to the desired application. The nanocomposites prepared by varying the TiO2:H2O2:aniline-dimer molar ratios were characterized for their thermal, optical, morphological, structural and surface properties. The reaction mechanism was investigated via mass analyses and X-ray photoelectron spectroscopy. The nanocomposites were tested on both methyl orange and hexavalent chromium removal. A fast dye-sorption was achieved also in the presence of interferents and the recovery of the dye was obtained upon eco-friendly conditions. An efficient Cr(VI) abatement was obtained also after consecutive tests and without any regeneration treatment. The fine understanding of the reaction mechanism allowed us to interpret the pollutant-removal performances of the different materials, leading to tailored nanocomposites in terms of maximum sorption and reduction capability upon consecutive tests even in simulated drinking water

Ultrasound-assisted synthesis of WOx-decorated ZnO photocatalysts for NOx abatement

Heterojunctions based on ZnO have numerous applications, such as water splitting, sensing and energy storage [1]. Recently, ZnO/WO3 composites have shown promising results in the sonocatalytic and photocatalytic degradation of aqueous and gas pollutants [2]. Several synthetic approaches have been reported, including chemical vapor deposition, magnetron sputtering, hydrothermal methods and high temperature annealing. Ultrasound-assisted synthesis can provide a scalable and cost-effective strategy to tailor the catalyst structural and morphological properties [3]. In the present work, pristine ZnO and ZnO/WOx composites were synthesized via a sonochemical method, studying the role of the ultrasound amplitude and mode (continuous/pulsed), metal precursor, WOx content and post-synthetic annealing. The resulting materials were extensively characterized, investigating their structural, morphological, optical, and surface properties. Samples were tested towards the photocatalytic removal of NOx under both UV and visible light irradiation in a batch reactor. A good degree of crystallinity is appreciable even before calcination and better morphological features are observed with respect to reference samples prepared without ultrasounds. The morphological properties can be further tuned by changing the metal precursor and adding a post-synthetic annealing step. Photocatalytic activity is promoted with respect to both benchmark samples (Figure 1)