Browsing by Author "Piccirillo, C."
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- Aerosol assisted chemical vapour deposition of hydroxyapatite-embedded titanium dioxide composite thin filmsPublication . Piccirillo, C.; Denis, C. J.; Pullar, R. C.; Binions, R.; Parkin, I. P.; Darr, J. A.; Castro, P. M. L.This work describes the first Aerosol Assisted Chemical Vapour Deposition (AACVD) synthesis of photocatalytic titanium dioxide thin films embedded with synthetic hydroxyapatite, [Ca-10(PO4)(OH)(2)], nanoparticles. The hydroxyapatite nanoparticles were prepared using a low temperature continuous hydrothermal flow synthesis method; analysis of the hydroxyapatite powder showed that it was phase pure and that the as-prepared material was made up of nano-needles. The nanoparticles were then embedded into TiO2 coatings using the AACVD technique by suspending them in a solution of the titania precursor (titanium tetra-isopropoxide). Results showed that the hydroxyapatite, although present in very low concentrations in the coatings (not detectable by XRD or Raman spectroscopy), heavily affected their morphology, depending on their concentration in the precursor solution. Tests of the photocatalytic activity of the composite films showed that the inclusion of the hydroxyapatite led to an increase in methylene blue photodegradation (up to 50% higher) and that the materials were photostable. This study shows that TiO2 coatings embedded with hydroxyapatite nanoparticles have potential as highly efficient photocatalysts.
- Bacteria immobilisation on hydroxyapatite surface for heavy metals removalPublication . Piccirillo, C.; Pereira, S. I. A.; Marques, A. P. G. C.; Pullar, R. C.; Tobaldi, D. M.; Pintado, M. E.; Castro, P. M. L.Selected bacterial strains were immobilised on the surface of hydroxyapatite (Ca-10(PO4)(6)(OH)(2) - HAp) of natural origin (fish bones). The capacity of the material, alone and in combination with the bacterial strains to act as heavy metal removers from aqueous streams was assessed. Pseudomonas fluorescens (S3X), Micro bacterium oxydans (EC29) and Cupriavidus sp. (1C2) were chosen based on their resistance to heavy metals and capacity of adsorbing the metals. These systems were tested using solutions of Zn(II), Cd(II) and in solutions containing both metals. A synergistic effect between the strains and HAp, which is effective in removing the target heavy metals on its own, was observed, as the combination of HAp with the bacterial strains led to higher adsorption capacity for both elements. For the solutions containing only one metal the synergistic effect was greater for higher metal concentrations; 1C2 and EC29 were the most effective strains for Zn(II) and Cd(II) respectively, while S3X was less effective. Overall, an almost four-fold increase was observed for the maximum adsorption capacity for Zn(II) when 10 was employed - 0.433 mmol/g in comparison of 0.121 mmol/g for the unmodified HAP. For Cd(II), on the other hand, an almost three-fold increase was registered with EC29 bacterial strain - 0.090 vs 0.036 mmol/g for the unmodified HAp. When the solutions containing both metals were tested, the effect was more marked for lower concentrations.
- Bioconversion of oleuropein to hydroxytyrosol by lactic acid bacteriaPublication . Santos, M. M.; Piccirillo, C.; Castro, Paula M. L.; Kalogerakis, N.; Pintado, M. E.The aim of this work is to study the conversion of oleuropein—a polyphenol present in olives and olive oil by-products—into hydroxytyrosol, a polyphenol with antioxidant and antibacterial properties. The hydrolysis reaction is performed by lactic acid bacteria. Six bacterial strains (Lactobacillus plantarum 6907, Lactobacillus paracasei 9192, Lactobacillus casei, Bifidobacterium lactis BO, Enterococcus faecium 32, Lactobacillus LAFTI 10) were tested under aerobic and anaerobic conditions. The oleuropein degradation and hydroxytyrosol formation were monitored by HPLC. Results showed that oleuropein could be successfully converted into hydroxytyrosol. The most effective strain was Lactobacillus plantarum 6907, with a reaction yield of hydroxytyrosol of about 30 %. Different reaction mechanisms were observed for different microorganisms; a different yield was observed for Lactobacillus paracasei 9192 under aerobic or anaerobic conditions and an intermediate metabolite (oleuropein aglycone) was detected for Lactobacillus paracasei 9192 and Lactobacillus plantarum 6907 only. This study could have significant applications, as this reaction can be used to increase the value of olive oil by-products and/or to improve the taste of unripe olives.
- Biphasic apatite-carbon materials derived from pyrolysed fish bones for effective adsorption of persistent pollutants and heavy metalsPublication . Piccirillo, C.; Moreira, I. S.; Novais, R. M.; Fernandes, A. J. S.; Pullar, R. C.; Castro, P. M. L.Biphasic apatite-carbon biochar-type materials were prepared from pyrolysed cod fish bones and were assessed for the adsorption of persistent organic pollutants (pharmaceuticals diclofenac and fluoxetine), and heavy metals (Pb(II)). The materials, prepared with a simple pyrolysis process at different temperatures (200–1000 °C), were characterised with XRD, FTIR, Raman and SEM. Results showed that the pyrolysis temperature had a significant effect on the features/composition of the materials: up to 800 °C, carbonate apatite Ca10(PO4)6(CO3) was the main component, while for higher temperatures oxyapatite Ca10(PO4)6O was the dominant phase. Graphitic carbon was also detected. The mixed apatite-carbon products (bone char) exhibited high adsorption efficiency. Graphite carbon was the main adsorber for the pharmaceuticals, the best performing material being that pyrolysed at 1000 °C. Xm values of 43.29 and 55.87 mg/g were observed (Langmuir fitting), while KF values of 5.40 and 12.53 (mg/g)(L/mg)nF were obtained with the Freundhlich model (diclofenac and fluoxetine respectively). This is the first time that a biochar-like material has been used for fluoxetine adsorption. For Pb (II), the powder pyrolysed at 600 °C was the most effective, with the apatite playing a key role (Xm = 714.24 mg/g). This work shows that a by-product of the fish industry could be converted into efficient materials for environmental remediation; according to the pyrolysis conditions, powders effective in the removal of either organics or heavy metals can be obtained. Moreover, with pyrolysis at intermediate temperatures, materials capable of adsorbing both kinds of pollutants can be produced, even if less efficient.
- Calcium hydroxyapatite-based photocatalysts for environment remediation: characteristics, performances and future perspectivesPublication . Piccirillo, C.; Castro, P. M. L.Calcium hydroxyapatite Ca10(PO4)6(OH)2 (HAp) is a material widely used in biomedicine, for bone implants manufacture, due to its biocompatibility. HAp has also application for environmental remediation, as it can be employed as metal removal; moreover, it has the capability of effectively adsorbing organic molecules its surface. In recent years, the photocatalytic properties of HAp have been investigated; indeed several studies report of HAp used as photocatalyst, either on its own or combined with other photocatalytic materials. Although in the majority of cases the activity was induced by UV light, some reports of visible light-activated materials were reported. Here we present a critical review of the latest developments for HAp-based photocatalysts; the materials discussed are undoped single phase HAp, doped HAp and HAp-containing composites. For undoped single phase HAp, the possible surface treatment and lattice defects which can lead to a photoactive material are discussed. Considering doped HAp, the use of Ti4+ (the most common dopant) is described, with particular attention to the effects that this metal have on the characteristics of the material (i.e. crystallinity) and on its photocatalytic behaviour. The use of other dopants is also discussed. For the multiphasic materials, the combination of HAp with other photocatalysts is discussed, mainly but not only with titanium dioxide TiO2. Overall, HAp is a compound with high potential as photocatalyst; this property, combined with its capability for heavy metal removal, makes it a multifunctional material for environmental remediation. As future perspectives, further studies, based on the results obtained until present, should be performed, to improve the performance of the materials and/or shift the band gap into the visible. The use of other dopants and/or the combination with other photocatalysts, for instance, are features which is worth exploring.
- Chemical composition and antibacterial properties of stem and leaf extracts from Ginja cherry plantPublication . Piccirillo, C.; Demiray, S.; Silva Ferreira, A. C.; Pintado, M. E.; Castro, Paula M. L.In this work the first systematic study on the composition and the antibacterial properties of the extracts from the stems and the leaves of Ginja cherry are reported. This native Portuguese cherry (Prunus cerasus, L. Rosaceae) is used to make a liquor (Ginjinha); both stems and leaves are a by-product of this process. The extracts from stems and leaves were prepared using different solvents (ethyl acetate, ethanol, acetone and water); their analysis was performed with GC-MS. Thirty-six volatile compounds were identified; terpenes - both hydrocarbons and oxygenated - were the main class of compounds. The extracts made from the stems with ethyl acetate were particularly rich in these species; compounds such as linalool, alpha-pinene, 4-terpineol and cedrene were present in concentration more than 10 times higher than in the other extracts. The antibacterial properties of all the extracts were tested against eight bacterial strains; the values of the minimum inhibitory concentration and minimum bactericidal concentration were determined. The stem extracts in ethyl acetate were the most active, showing bacteriostatic and bactericidal activity towards Gram-positive and Gram-negative microorganisms. This study showed that these by-products can be successfully valorized with solvent extraction of valuable compounds. The antibacterial properties of these extracts, combined with their antioxidant activity, make them suitable to be employed in areas like cosmetics and food packaging.
- Chitosan-hydroxyapatite composites made from sustainable sources: a morphology and antibacterial studyPublication . Scalera, F.; Pereira, S. I. A.; Bucciarelli, A.; Tobaldi, D. M.; Quarta, A.; Gervaso, F.; Castro, P. M. L.; Polini, A.; Piccirillo, C.Chitosan (Cs) and hydroxyapatite (HA) 3D scaffolds/composites were prepared with a sustainable process, as HA was obtained using CaCO3 derived from cork, a natural material used as a template agent. The HA@Cs composites were prepared with HA in situ formation in a Cs solution, with a dissolution-precipitation mechanism. Different reaction times were considered, with time of 72 h leading to the best materials (sample CsHA_72). X-ray Diffraction (XRD) analysis confirmed HA formation. The analysis of Cs unit cell parameters showed that, for the unmodified Cs, the cell had larger dimensions and a higher degree of distortion than previously reported in literature; HA incorporation in the CsHA_72 composite led to a further increase in the cell dimensions. The morphology of the scaffolds was studied with Scanning Electron Microscopy (SEM) and a high level of porosity was observed; a statistical comparison was performed between the unmodified Cs and CsHA_72 to determine the pore size, structure, and distribution. This analysis, the first of this kind for this type of composites, showed smaller and more circular pores for the CsHA_72 composite (average diameter of 70 μm vs. 88 μm for unmodified Cs). The overall level of porosity, however, did not change (>77%); likewise, the Young modulus was not affected by HA incorporation (about 11 kPa). Antibacterial tests, performed on Escherichia coli and Staphylococcus aureus, showed that HA presence did not significantly reduce the antimicrobial properties; the composites were particularly effective towards S. aureus, as a >90% the bacterial population reduction was observed for an incubation time of 2 h. HA@Cs also showed excellent biocompatibility and good cell proliferation. The properties of these 3D scaffolds make them suitable for application as biomaterials.
- Composition and antibacterial properties of extracts from agricultural by-productsPublication . Piccirillo, C.; Demiray, S.; Silva Ferreira, António César; Pintado, M. E.; Castro, Paula M. L.
- Effect of preparation and processing conditions on UV absorbing properties of hydroxyapatite-Fe2O3 sunscreenPublication . Teixeira, M. A. C.; Piccirillo, C.; Tobaldi, D. M.; Pullar, R. C.; Labrincha, J. A.; Ferreira, M. O.; Castro, Paula M. L.; Pintado, M. M. E.The development of innovative, safe and non-photocatalytic sunscreens is urgently needed, as it is essential to have sunscreen filters offering appropriate UV protection without damaging the environment and/or generating free radicals when in contact with the skin. Hydroxyapatite (Ca-10(PO4)(6)(OH)(2), HAp) when substituted with iron has UV protection properties and is not photocatalytic; HAp was used to make a sunscreen filter by treating cod fish bones in an iron-containing solution, and then calcining them at 700 degrees C. Here we present a systematic and advanced study on this material, to obtain a sunscreen with improved UV absorbing properties, Bones were treated with three different iron salts - Fe(II) chloride, Fe(II) lactate and Fe(III) nitrate - under various pH conditions. Results showed that Fe(II) chloride in basic pH led to the most effective iron inclusion, High energy ball milling or ultrasound were investigated to increase surface area and corresponding UV absorption; high energy ball milling treatment led to the best optical properties. The optimum powders were used to formulate UV protection creams, which showed Sun Protection Factor (SPF) values significantly superior to the control cream (up to 4.1). Moreover the critical wavelength (lambda(crit)) was >370 nm (388-389 nm) and UVA/UVB ratios were very close to 1. With these properties these sunscreens can be classified as broad UV protectors. Results also showed that combining these powders with other sunscreens (i.e. titanium dioxide), a synergic effect between the different components was also observed. This investigation showed that HAp-based sunscreens of marine origin are a valid alternative to commercial products, safe for the health of the customers and, being non-photocatalytic, do not pose a threat to the environment.
- Effects of Cu, Zn and Cu-Zn addition on the microstructure and antibacterial and photocatalytic functional properties of Cu-Zn modified TiO2 nano-heterostructuresPublication . Tobaldi, D. M.; Piccirillo, C.; Rozman, N.; Pullar, R. C.; Seabra, M. P.; Škapin, A. Sever; Castro, Paula M. L.; Labrincha, J. A.Titanium dioxide (TiO2) is well established as one of the most common photocatalysts used for many environmental, anti-pollution and antibacterial applications. However, in this work, novel photocatalytic TiO2 nanopowders were modified with additions of 1 mol% copper, zinc or copper + zinc (with various Cu: Zn ratios). These were prepared via a green sol–gel route and thermally treated at 450 C. For the first time, a direct comparison of the effects of these two modifying agents was performed, both as single and co-substitution. The compounds were thoroughly characterised by means of advanced X-ray diffraction (Whole Powder Pattern Modelling, WPPM) and spectroscopic methods (Raman and UV–vis). For functional properties, the photocatalytic activity in the gas-solid phase (nitrous oxides (NOx) and isopropanol degradation (VOCs)) was tested under UV and visible light, and antibacterial activity against Gram positive and Gram negative bacterial strains was also investigated. Neither copper nor zinc entered into the TiO2 structure, but nucleated as oxides at the surface of titania nanoparticles, thus creating a nano-heterojunction between the semiconductor materials; this also retarded the anatase-to-rutile phase transition. When comparing and contrasting their functional properties, it was found that Zn modification gave greater photocatalytic activity than that with Cu. On the contrary, for antibacterial activity, copper was shown to be a better additive. Co-modification with both metals did not improve the antibacterial behaviour, but did lead to an increase in photocatalytic activity in some cases.
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