3,623 research outputs found
SOSpesa – Neighbourhood solidarity networks for the recovery, distribution, and valorisation of food surplus.
No full textThis paper presents and discusses the redesign of a charity activity, implemented in a neighbourhood of the city of Milan, into an innovative service called 'SOSpesa'. By creating, activating and experimenting a network of local actors to achieve a solidarity aim against food poverty, SOSpesa also implements a strategy to fight food waste and support local shops. Acting on a neighbourhood scale, it leverages the local context as a strength of the service, exploiting the networks already existing in the specific context of NoLo, the ‘North of Loreto’ area of the city. The paper illustrates the initiative's ongoing transformation from charitable action to structured service, working carefully not to distort its spirit and bottom-up commitment, and with the intention to frame it into a replicability strategy
Polyaniline-oxide nanocomposites for environmental remediation : the role of the nature of the photocatalyst
No full textPANI materials have been recently applied to pollutant abatement owing to PANI environmental stability and sorption capabilities [1]. However, the conventional PANI synthesis involves toxic reagents, hazardous by-products and large amounts of inorganic waste. As an alternative, we developed a two-step green procedure starting from benign reactants ((N-(4-aminophenyl)aniline and H2O2) and initiated by UV-irradiated photocatalysts [2][3]. Here, the role of the adopted photocatalysts was investigated in depth by adopting semiconductor oxides of different nature and surface area: two commercial TiO2 powders (Degussa P25, 50 m2/g, and Kronos 1077, 10 m2/g) together with synthesized and commercial WO3 powders (3.5 m2/g and 6.1 m2/g). Moreover, the amount of H2O2 was varied (from a 1/1 aniline-dimer/H2O2 molar ratio to a 1/3) to investigate the reaction mechanism. The as prepared PANI-composites where subjected to an all-round characterization. All the prepared PANI composites presented a large surface area and a crystallinity degree higher than PANI materials reported in the literature. These features can be related to the two-step mechanism of our synthetic procedure as showed by the study of the PANI-TiO2 synthesis. During the first step, ATR-FTIR, XPS and ζ-potential measurements highlighted the formation and slow growth of PANI-oligomeric chains at the photocatalyst surface upon UV-irradiation. The ensuing addition of H2O2 in the second step leads to the polymer formation. On the other hand, PANI composites prepared with different oxides showed important differences in terms of PANI oxidation state and of amount of oligomers generated during the first synthetic step. Furthermore, while the amount of H2O2 plays a major role in PANI-TiO2 synthesis, leading to strong changes in the final composite surface area and polymer content, PANI-WO3 composites did not showed any dependence on the synthetic H2O2 amount, underlying differences in the semiconductor-produced oxidizing species. Samples were tested towards wastewater remediation, showing good dye and heavy metal removal capacity. While a similar total dye removal capacity was observed, notable differences are observed in terms of adsorption kinetics of PANI-composites prepared with different photocatalysts, as shown by the figure on right. The sample prepared with the high surface area oxide (TiO2-P25) resulted in a faster kinetics, whereas the other tested oxides led to composites exhibiting an intraparticle diffusion kinetics, despite the similar surface area of the PANI-composites. These differences can be traced back to the sample morphology and oxidation state of the polymer component.
References
1. A. Samadi, M. Xie, J. Li, H. Shon, C. Zheng, S. Zhao, Chem. Eng. J. 2021, 418, 129425
2. C. Cionti, C. Della Pina, D. Meroni, E. Falletta, S. Ardizzone, Chem. Commun. 2018, 54, 10702
3. C. Cionti, C. Della Pina, D. Meroni, E. Falletta, S. Ardizzone, Nanomaterials, 2020, 10, 441
Self-cleaning properties of a silica/silver nanoparticles/titania sandwich sensor
No full textOne of the main challenges faced during electroanalysis of complex matrices is represented by fouling and passivation of the electrode surface, especially in the fields of biomedical and environmental trace analysis [1], where sophisticated and highly engineered sensors have to be used in order to increase sensitivity and lower detection limits. These sensors can not be cleaned by conventional mechanical or electrochemical procedures, since these methods could affect the integrity of the active layer. In order to overcome these problems, the production of highly engineered reliable and reusable devices, designed ad hoc for specific applications, which could be simply cleaned by irradiation with UV light, would be an interesting step beyond the current state of the art.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer [2, 3] was designed, prepared and characterized. The device structure is meant to confer multifunctional properties for a complex biomedical challenge: the detection and quantification of catecholamine neurotransmitters. The key role of each component of the device was thoroughly investigated to demonstrate the robustness and efficiency of the final sensor. In particular, the size distribution of silver nanoparticles, the device architecture and surface homogeneity were inspected by electron microscopy. The cleaning overlayer was made of the active polymorph of titanium dioxide (anatase), as confirmed by X-ray diffraction and by model contaminants photodegradation measurements. Electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that an highly ordered distribution of silver nanoparticles is the active core of the device, allowing easier electron transfer and better quantification of the analytes even in the presence of conventional interferents, e.g. ascorbic acid and uric acid in human fluids.
The high photoactivity of titania top layer allowed total recovery of the device performance in terms of sensitivity after a fast (less than 20 min) UV cleaning step, affordable with different UV-A sources. This self-cleaning property, combined with a remarkable resistance against ageing, allows to employ the sensor also in on-field and remote applications.
References
[1] C. M. Welch and R. G. Compton, Anal. Bioanal. Chem. 2006, 384, 601–619.
[2] G. Maino, D. Meroni, V. Pifferi, L. Falciola, G. Soliveri, G. Cappelletti, S. Ardizzone, J. Nanoparticle Res. 2013, 15, 2087.
[3] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 2015, 140, 1486
Innovative engineered sensors based on silica, silver nanoparticles and titania with self-cleaning features
No full textPassivation of the electrode surface and fouling are important challenges in electroanalysis during the use of modified electrodes in complex matrices, especially in the biomedical and environmental fields (Soliveri et al., 2015). The production of highly engineered devices, ad hoc designed for specific applications, could overcome such problems, accessing really effective sensors. A performing, reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, would perfectly match this goal.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer (Maino et al., 2013 and Welch and Compton, 2006), was developed. Such structure confers to the device multifunctional properties for a complex biomedical challenge: the detection and quantification of catecholamine neurotransmitters. The sensor was thoroughly investigated in order to understand the role of each component with the aim of making the device a robust and efficient electroanalytical system.
The overlayer was made of anatase (the active polymorph of titanium dioxide) as confirmed by X-ray diffraction and by measuring the photodegradation of model contaminants. The size distribution of silver nanoparticles, the device architecture and surface homogeneity were inspected by electron microscopy. Electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that a highly ordered distribution of silver nanoparticles constitutes the active core of the device, allowing easier electron transfer and better quantification of the analytes even in the presence of conventional interferents, e.g. ascorbic and uric acid. Titania photoactive top layer allowed total recovery of the device performance in terms of sensitivity after a fast and simple UV-A cleaning step, affordable with different UV sources. This self-cleaning property, combined with a remarkable resistance against aging and ease of use, allows to employ the sensor also in on-field and remote applications.
Maino G., Meroni D., Pifferi V., Falciola L., Soliveri G., Cappelletti G., Ardizzone S. (2013). Electrochemically assisted deposition of transparent, mechanically robust TiO2 films for advanced applications. J. Nanoparticle Res., 15, 2087.
Soliveri G., Pifferi V., Panzarasa G., Ardizzone S., Cappelletti G., Meroni D., Sparnacci K., Falciola L. (2015). Self-cleaning properties in engineered sensors fordopamine electroanalytical detection. Analyst, 140, 1486-1494.
Welch C. M., Compton R. G. (2006). The use of nanoparticles in electroanalysis: a review. Anal. Bioanal. Chem., 384, 601–619
Anti-inflammatory and immunomodulating properties of statins. An additional tool for the therapeutic approach of systemic autoimmune diseases?
No full textCardiovascular diseases secondary to accelerated atherosclerosis are now accepted as a cause of mortality and morbidity in patients suffering from systemic lupus erythematosus and rheumatoid arthritis. More recently, atherosclerosis is emerging as one of the most serious complications in the anti-phospholipid syndrome, although large epidemiological studies, such as those performed in lupus and rheumatoid arthritis patients, have not been performed up to now. Classical risk factors (dislipidemia, hypertension, diabetes, smoking, etc.) and steroid therapy cannot completely explain the high prevalence of cardiovascular complications in systemic autoimmune diseases. Since the modern view defines atherosclerosis as a chronic inflammatory disorder, it has been suggested that systemic inflammation and soluble immune mediators (circulating autoantibodies, immune-complexes, complement activation products) might play a role in accelerating vessel pathology. The main target appears to be the endothelium because of its ability to switch to a pro-adhesive, pro-inflammatory and pro-coagulant surface in response to these mediators. Recent advances in the knowledge of the pharmacology of statins have indicated that these drugs rather than to be simple cholesterol lowering molecules display a pleiotropic effects on several mechanisms involved in the atherosclerotic plaque formation. Their anti-inflammatory activity and particularly their ability to downregulate endothelial cell activation induced by different stimuli strongly suggest their possible use in conditions in which the systemic inflammation and the endothelial activation/damage are thought to represent key pathogenic mechanisms
On smooth functions with two critical values
No full textWe prove that every smooth closed connected manifold admits a smooth real-valued function with only two critical values such that the set of minima (or maxima) can be arbitrarily prescribed, as soon as this set is a finite subcomplex of the manifold (we call a function of this type a Reeb function). In analogy with Reeb’s Sphere Theorem, we use such functions to study the topology of the underlying manifold. In dimension 3, we give a characterization of manifolds having a Heegaard splitting of genus g in terms of the existence of certain Reeb functions. Similar results are proved in dimension n≥5
Bouncing Droplets: A Hands-On Activity To Demonstrate the Properties and Applications of Superhydrophobic Surface Coatings
No full textHere we report a hands-on activity addressed to master’s students in Physical Chemistry and Materials Science courses on the properties and applications of superhydrophobic surfaces. This simple and intuitive experience can also be used to teach undergraduate and high school students, thanks to its application-oriented approach and tangible results. Superhydrophobicity was achieved by the functionalization of oxide powders with alkylsilanes and their subsequent deposition on a glass substrate. The film’s superhydrophobicity was assessed by different application tests and compared with the behaviors of model hydrophobic, hydrophilic, and superhydrophilic surfaces. Its antistain properties were tested with both model dye solutions and everyday liquids. Films were fouled with graphite and dye powders to compare the self-cleaning capabilities of the different surfaces, and single droplet transport was achieved by adding magnetic particles. This engaging and adaptable experience introduces students to basic concepts of surface science in an intuitive and tangible way
UV-induced synthesis of polyaniline (PANI)-TiO2 composites : mechanistic insight and application as sorbent for wastewater remediation
No full textIn recent years, the application of PANI-based materials to pollutant abatement has been proposed owing to PANI environmental stability and excellent sorption capabilities1. However, conventional synthetic procedures of PANI-materials are based on toxic reagents and generate hazardous by-products and large amounts of inorganic waste. As an alternative to conventional PANI oxidative syntheses, we recently developed a green procedure starting from benign reactants ((N-(4-aminophenyl)aniline and H2O2) and initiated by light-irradiated titanium dioxide2. In order to unlock the full potential of this synthetic approach, we studied the relative roles of the oxide semiconductor and of H2O2 in this two step synthetic approach. Composites were synthesized by varying the TiO2 : H2O2 : aniline dimer molar ratios and were characterized from the compositional, structural, morphological, optical, and thermal point of view. Moreover, the reaction mechanism was investigated via a combination of spectroscopic and spectrometric techniques. We found that the first step is driven by TiO2 and UV irradiation and leads to the formation of oligomers at the oxide surface, promoting a higher polymer crystallinity in the final composite. The polymer chain growth requires the addition of H2O2 and the added amount has a crucial role on the reaction pathway. While stoichiometric H2O2 amounts promote the growth of oligomer chains adsorbed at the oxide surface, giving rise to highly porous, large surface area composites, an excess of H2O2 promotes homogenous phase reactions, leading to composites with higher PANI content and thermal stability, but more amorphous and with compact morphology. The composite properties can thus be tailored depending on the desired application. We tested the prepared composites towards the removal of wastewater pollutants, including both organic dyes and heavy metals. A fast and complete pollutant removal was achieved also in the presence of interferents. Consecutive tests with and without regeneration treatments showed promising results in terms of repeated usability, even in simulated drinking water matrix.
References
1. C. Della Pina, M. A. De Gregorio, L. Clerici, P. Dellavedova, E. Falletta, J. Hazard. Mater. 2018, 344, 1
2. C. Cionti, C. Della Pina, D. Meroni, E. Falletta S. Ardizzone Chem. Commun. 2018, 54, 10702
UV-induced synthesis of polyaniline-TiO2 hybrids: a mechanistic study
No full textPolyaniline, an important member of the conductive polymer family, has received increasing attention due to its peculiar pH-dependent properties which open the way to a wide spectrum of applications, ranging from electronics and optics to photovoltaic1,2. PANI is traditionally synthesized via oxidative polymerization3, a process which involves toxic reagents (aniline and persulfates) and leads to carcinogenic byproducts. Aiming to more environmentally friendly procedures, other synthetic strategies have been developed during the years: in particular, some of us4 have reported a green synthesis involving aniline dimer ((4-aminophenyl)aniline) as starting compound, H2O2 as oxidant and Fe3+ as catalyst, thus yielding H2O as only coproduct. Unfortunately, with this eco-friendly process, there is no control on the polymer morphology and the result is a compact PANI with low dye-sorption capabilities. We have recently proposed a new green synthesis in which PANI growth is activated by TiO2 photocatalysis giving rise to PANI-TiO2 hybrid systems5. The reaction is carried out in two steps: the photocatalytically induced oligomerization of aniline dimer at the TiO2 surface, and the polymerization step initiated by H2O2 addition. In this work, the reaction mechanism was investigated via radical scavenger tests and by a combination of LCMS, FTIR, XPS and ζ-potential measurements. UV light is essential to initiate the reaction, as without irradiation only short oligomers with poor chain-conjugation are formed (Fig.1). Overall, this synthetic method leads to composites stable under UV irradiation in usage conditions, with high specific surface areas (crucial for sorption properties) and enhanced crystallinity, which is beneficial for PANI conductivity. The role of synthetic parameters like reagent ratios and temperature was also investigated; while incrementing the H2O2 amount leads to poorer crystallinity and lower surface area, the TiO2 content in the hybrid can be increased without affecting its morphology and performance. All samples were tested towards the removal of model dye pollutants. The reusability of the nanocomposite and the influence of common interferents were investigated, also via tests in simulated drinking water. References [1] C.O. Baker, X. Huang, W. Nelson, R.B. Kaner, Chem. Soc. Rev., 46, 2017, 1510. [2] F. Cui, Y. Huang, L. Xu, Y. Zhao, J. Lian, J Bao, H Li, Chem. Commun., 54, 2018, 4160. [3] H.D. Tran, J.M. D’Arcy, Y. Wang, P.J. Beltramo, V.A. Strong, R.B. Kaner, J. Mater. Chem., 21, 2011, 3534 [4] C. Della Pina, M. A. De Gregorio, L. Clerici, P. Dellavedova, E. Falletta, J. Hazard. Mater., 2018, 344, 308 [5] C. Cionti, C. Della Pina, D. Meroni, E. Falletta, S. Ardizzone, Chem. Commun., 2018, 54, 1070
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