1,721,455 research outputs found
The role of the synthetic procedure of nano-crystalline TiO2 on the photodegradation of toluene
No full textBecause of its stability and nontoxicity TiO2 has been extensively investigated as an efficient photocatalyst for purifying water and air. The use of TiO2 in photocatalytic concrete and paints is very promising and intensively investigated.
In recent years a great deal of activity was dedicated, by the authors’ group, to the study of synthetic routes leading to nanocrystalline materials with tailored features, mainly in the case of titania. Sol-gel paths, combined with hydrothermal stages performed either in the presence or in the absence of surfactants, have led to nanocrystalline TiO2 with controlled enrichment in either anatase, brookite or rutile [1-4]. There is ample debate in the literature concerning the actual role played by either of the titania polymorphs with respect to the photocatalytic activity of the material [5].
In this work the authors report on the activity of nanocrystalline titania, prepared by a multi-step sol-gel procedure, with respect to the photodegradation of toluene used as a model compound. Samples with varying surface area and anatase/brookite/rutile content are fully characterized and then tested and their photoactivity is compared with that of the most commonly commercial TiO2 photocatalysts.
The photodegradation of toluene is investigated both in aqueous and in gas phase. In the former case the composition of the reacting mixture, in terms of side products, is followed by HPLC and MS-GC and the total mineralization by TOC. In the latter case the reactor is equipped with an online micro-GC.
[1] T. Boiadjieva, G. Cappelletti, S. Ardizzone, S. Rondinini, A. Vertova, Phys. Chem. Chem. Phys., 5 (2003) 1689.
[2] G. Cappelletti, C. Ricci, S. Ardizzone, C. Parola, A. Anedda, J. Phys. Chem. B., 109 (2005) 4448.
[3] C.L. Bianchi, S. Ardizzone, G. Cappelletti, Dekker Encyclopedia of Nanoscience and Nanotechnology Marcel Dekker (New York), 2006, pp. 1-10, DOI: 10.1081/E-ENN-120042107
[4] G.Cappelletti, C.L.Bianchi, S. Ardizzone, Appl. Surf. Sci., 253 (2006) 519-524
[5] J. Krysa, M. Keppert, J. Jirkovsky, V. Stengl, J. Subrt, Mater. Chem. Phys., 86 (2004) 333
On the Different Strategies to Reduce the Decay of Stone-Built Cultural Heritage
No full textDeterioration phenomena of ancient and modern stone cultural heritage are natural and unrestrainable decay processes mainly arising from water percolation into stone building materials [1-11]. Thus, the application of hydrophobic/superhydrophobic coatings to stone surfaces is mandatory to protect them from the deleterious effects of water exposition.
Here, in order to avoid both natural and artificial stone decay, mainly due to the interaction with atmospheric pollutants (both gases such as NOx and SO2 and particulate matter) i) commercially available Si-based resins have been applied as protective agents [3,8,10,11], ii) new polymeric coatings have been synthesized with satisfactory water repellency and improved durability, thanks to the combined use of fluorinated and long alkyl chain monomers and without the use of any photo-stabilizers agents [2,4,5,6,7] and finally iii) hybrid coatings containing home-made TiO2 and SiO2 nanoparticles mixed with the commercial silane polymers have been tested to obtain complete buoyancy and self-cleaning properties [1,9]. Both natural stone materials (Carrara, Botticino, Candoglia marbles and Angera, Vicenza stones) and mortars (an Air hardening calcic lime mortar, ALM, and a natural hydraulic lime mortar, HLM) have been used as substrate to be treated.
The results concerning the physico-chemical characteristics of the bare stones compared with those of the treated samples will be presented and discussed. In order to evaluate the stability of the applied coatings towards degradation induced by solar radiation and interaction with the atmospheric pollution, accelerated ageing tests under UV irradiation (also exposing the samples in a Q-UV tester cabinet) and exposure tests in a typical polluted urban environment have been carried out. For the samples characterization the following analyses have been performed: contact angle measurements, SEM-EDS (Scanning Electron Microscopy with X-ray microanalysis), IC (Ion Chromatography), colorimetric tests by DRS (Diffuse Reflectance Spectroscopy) followed by CIELab elaboration, porosity measurements, water absorption by capillarity and water vapor permeability.
The properties of the home-made and commercial hydrophobizing polymers in terms of macromolecular structure, molecular weights, thermal features, and water repellency were determined. Furthermore, the long-term behavior of these polymers was estimated by means of accelerated aging tests exploiting UV radiations. Their behavior over time was checked via Size Exclusion Chromatography (SEC) by evaluating Mn and D data of aged polymeric samples and by Fourier Transform Infrared (FT-IR) spectroscopy: all the synthesized polymers seem to be unaffected by UV aging. Thus, the present stable resins were applied on both natural (marble) and artificial (mortar) stone substrates and their wetting properties together with their absorption by capillarity and water vapour permeability were successfully assessed and compared, showing potential features for cultural heritage protection
Nanocomposite Materials for Low Temperature VOCs Chemoresistors
Full text linkThe sensing of gas molecules is of fundamental importance for environmental monitoring, control of chemical processes, and non-invasive medical diagnostics based on human’s breath analysis [1,2]. In recent years, graphene-based gas sensors have attracted much attention and different materials have been developed [2]. However, they still suffer from several problems, which could be overcome by covering the graphene surface with metal oxides (MOS). Besides, thanks to the high chemical versatility, promising results could be also obtained by coupling porphyrin-based macrocycles to MOS. As such, boosted potentialities, especially in terms of tuned selectivity and low water interference, may be obtained. Therefore, the present work is aimed at evaluating and comparing the sensing at both mild temperatures (also exploiting the UV and solar light) of SnO2 matrix coupled with different porphyrins and graphene oxide materials towards the sensing of acetone molecules [4]. Specifically, zinc tetraphenylporphyrin (ZnTPP) and perfluorinated-modified ones were adopted. Switching the lamp on, the samples ability to sense acetone drastically changed: the LOD reached the 200 ppb for all the materials. A possible explanation of the role of both GO and porphyrins in boosting the SnO2 sensing of oxidizing molecules (as acetone) is reported, according to the recent literature related to hybrid chemoresistors [3,4] and DSSC devices [5]
Photo-renewable engineered sensor based on silica, silver nanoparticles and titania
No full textElectrode surface passivation and fouling are important challenges in electroanalysis when using modified electrodes in complex matrices, especially in the biomedical and environmental fields [1-2].
In order to overcome such problems, the production of highly engineered ad hoc designed devices could provide really effective sensors [2]. In particular, a reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, could be perfect for this purpose.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer is developed [3-4]. Such structure confers to the device multifunctional properties which can be conveniently used in the detection and quantification of some neurotransmitters: dopamine, norepinephrine and serotonin.
The sensor is thoroughly investigated by structural, morphological and electrochemical characterizations in order to understand the role of each component with the aim to improve the robustness and efficiency of the electroanalytical system. In particular, the size distribution of silver nanoparticles, the device architecture and surface homogeneity are inspected by electron microscopy. As confirmed by X-ray diffraction the overlayer is made of anatase (the active polymorph of titanium dioxide), capable of photodegrading model contaminants. Furthermore, electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that a highly ordered distribution of silver nanoparticles constitutes the active analytical core of the device, allowing easier electron transfer and better quantification of the analytes.
The system presents good sensing performances, reaching low detection limits even in the presence of typical interferents such as ascorbic and uric acids. Moreover, the titania photoactive top layer allows the complete recovery of the device performance in terms of sensitivity after a fast and simple UV-A cleaning step, affordable with different UV sources. In particular, three lamps (different in terms of power and wavelength) were tested, reaching the total removal of the contaminants in 10-15 minutes [5]. This “self-cleaning” property, combined with a remarkable resistance against aging and ease of use, allows to employ the sensor also for detection in real matrixes, such as liquor and serum.
ACKNOWLEDGEMENTS
The Authors would like to thank MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca) for the fundings in the framework of the PRIN 2012 Project (20128ZZS2H)
REFERENCES
[1] C.M.A. Brett, Pure Appl. Chem. 73, 2001, pp 1969–1977.
[2] C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384, 2006, pp 601–619.
[3] G. Maino, D. Meroni, V. Pifferi, L. Falciola, G. Soliveri, G. Cappelletti, S. Ardizzone, J. Nanoparticle Res. 15, 2013, pp 2087.
[4] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 140, 2015, 1486-1494.
[5] V. Pifferi, G. Soliveri, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, L. Falciola, RSC Advances, 5, 2015, 71210-71214
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
Self-cleaning features of an innovative engineered sensor based on silica, silver nanoparticles and titania
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 [1-2].
In order to overcome such problems, the production of highly engineered ad hoc designed devices could access really effective sensors [2]. In particular, a performing, reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, would be perfect for this purpose.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer was developed [3-4]. 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 by structural, morphological and electrochemical characterizations in order to understand the role of each component with the aim to improve the robustness and efficiency of the 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.
References
1. C.M.A. Brett, Pure Appl. Chem. 73, 2001, pp 1969–1977.
2. C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384, 2006, pp 601–619.
3. G. Maino, D. Meroni, V. Pifferi, L. Falciola, G. Soliveri, G. Cappelletti, S. Ardizzone, J. Nanoparticle Res. 15, 2013, pp 2087.
4. G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 140, 2015, 1486-1494
Insight into microtubule dynamics: from purified protein to cell
No full textMicrotubule-targeting agents have received considerable interest as potential tumour-selective anti-angiogenic and vascular-disrupting agents. To improve targeting of these agents, a detailed characterization of their interaction with tubulin/microtubule system is required and includes the analysis of stabilisation and depolymerisation of microtubules as well as imbalance in microtubule dynamics. We performed in vitro assays using purified tubulin to investigate the effects of microtubule-targeting agents on microtubule assembly in terms of polymer mass, polymerization kinetics, microtubule structure.and dynamics1. Moving from purified protein to cultured cells, we investigated the effects of microtubule-targeting agents on microtubule network by immunofluorescence and confocal analyses. Finally, microtubule dynamics in live cell was investigated by time lapse imaging of cells expressing the microtubule-associated protein EB3-GFP, a protein that binds specifically to the plus end of growing microtubules
Experimental study of a rarefied plume impinging on a cylinder-plate configuration
No full textAn experimental analysis of the interaction of a rarefied jet plume with a cylinder-plate system is presented. The main goal is to show that the gas rarefaction can change the distribution of pressure between the two bodies quite unpredictably. The geometrical configuration has been proposed as test case to investigate the development of plume that are typically present in complex structures on spatial satellite. The results are qualitatively in a good agreement with analogous experiments and numerical simulations. (C) 2013 Elsevier Ltd. All rights reserved
Conservazione e valorizzazione degli insetti entomofagi negli ecosistemi naturali e urbani.
No full textMicrotubule destabilization paves the way to Parkinson’s disease
No full textMicrotubules are dynamic structures normally associated to the cell division, during which they form the mitotic spindle, as well as to the initial phases of specification and polarization of various cell type, including neurons. Although microtubules could have a role in the death of many cells and tissues, the microtubule-based degenerative mechanisms have been poorly investigated; nevertheless, during the last two decades, many clues have been accumulated suggesting the importance of microtubule system during neurodegeneration. Thus, the aim of this review is to analyse how the changes of the microtubule cytoskeleton, in terms of organization and dynamics, as well as the failure of the microtubule-dependent neuronal processes, as axonal transport, may play a pivotal role in the chain of events leading to Parkinson’s disease. Last but not least, since disease-modifying or neuroprotective strategies are a clinical priority in Parkinson’s disease, we will also present the hints about the concrete possibility of a microtubule-targeted therapy, which would have the potentiality to block the running degenerative events and to prompt the regeneration of the lost tissues
- …
