David Maria Tobaldi - Academia.edu (original) (raw)

Papers by David Maria Tobaldi

Journal of Physical Chemistry Letters 7 (2016) 4039-4046, Sep 27, 2016

We present for the first time a nonaqueous sol–gel route to produce ultrasmall (<2 nm) magnetic b... more We present for the first time a nonaqueous sol–gel route to produce ultrasmall (<2 nm) magnetic bimetallic CoPt3 nanoparticles (NPs). The one-pot procedure is carried out at low temperature (180 °C) using benzyl alcohol, acting as both reducing agent and solvent. The highly monodisperse CoPt3 NPs were investigated with innovative advanced X-ray methods (whole powder pattern modeling), HR-STEM, XPS, and SQUID magnetometry. XPS showed Co was mostly in metallic form, but with a very small amount of CoO on the NP surface. The spherical NPs had an ultrasmall diameter of 1.6 nm and could self-assemble in aligned linear chains, or nanobelts, of single NPs. They are superparamagnetic, with blocking temperature of ∼20 K and coercivity at 10 K of 27.9 kA m–1 (∼350 Oe). However, there is evidence of a second magnetic phase (probably CoO) in the ZFC magnetization curve, which enhances their magnetization values, without significantly affecting their superparamagnetism.

Solid State Sciences, 2007

Pseudobrookite pigments were synthesised by the conventional ceramic route, calcining at 1300 °C ... more Pseudobrookite pigments were synthesised by the conventional ceramic route, calcining at 1300 °C four mixtures, with a Fe 2 O 3 :TiO 2 ratio ranging from 47:53 to 40:60, and were characterised by XRPD, DRS and coloring performance in several ceramic matrices. Titania in moderate excess of the Fe 2 TiO 5 stoichiometry, necessary to minimise the occurrence of unreacted precursors, induced lattice parameters smaller than ideal pseudobrookite, in agreement with the different radii of Ti 4+ and Fe 3+ ions.

Journal of Solid State Chemistry, 2007

Karrooite, MgTi2O5, is a promising ceramic pigment due to its high refractoriness and refractive ... more Karrooite, MgTi2O5, is a promising ceramic pigment due to its high refractoriness and refractive indices, as well as its ability to host transition metal ions in two crystallographically distinct octahedral sites. The colouring performance was investigated combining X-ray powder diffraction with UV–vis–NIR spectroscopy on karrooite doped with V, Cr, Mn, Fe, Co or Ni (M) according to the formula Mg1−xTi2−xM2xO5,

Journal of Solid State Chemistry, 2015

Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution... more Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO2 has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO2 to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO2 lattice using our green sol-gel nanosynthesis method, used to create 10 nm TiO2 NPs. Two parallel routes were studied to produce nitrogen-modified TiO2 nanoparticles (NPs), using HNO3+NH3 (acid-precipitated base-peptised) and NH4OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800°C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NOx) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NOx abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450°C, and NPs heated to 450°C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO2 NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice

Ceramics International, 2015

Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 -HAp) is a common material for bone replacement in artific... more Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 -HAp) is a common material for bone replacement in artificial implants and prostheses, due to its high biocompatibility. In this work we report about the preparation of HAp-based materials of marine origin with antibacterial properties. Bones from cod fish (Gadhus morua) were treated with a dilute AgNO 3 solution, to obtain HAp-containing samples with silver as a minor component. The samples were characterised by XRD, FT-IR spectroscopy and SEM, indicating the presence of HAp, β-TCP and some metallic silver. The determination of unit cell parameters, however, indicated that the majority of silver is substituted in the β-TCP lattice in ionic form. The antibacterial activity of these materials was tested towards both Gram-positive and Gram-negative bacterias; results showed that the material is very effective with Gram-negative strains such as Escherichia coli (inactivation rates of 99.82% and 99.999% after 2 and 5 h, respectively) and had a smaller but still significant effect on Gram-positive MRSA (91% inactivation rate). These results show the potentials of these samples as infection-resistant bone replacement materials.

PLOS ONE, 2015

[This corrects the article DOI: 10.1371/journal.pone.0122989.].

PLOS ONE, 2015

A template-free precipitation method was used as a simple and low cost method for preparation of ... more A template-free precipitation method was used as a simple and low cost method for preparation of CeO 2 nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO 2 nanoparticles. The FT-IR spectrum of prepared CeO 2 nanoparticles showed absorption bands at 400 cm -1 to 450 cm -1 regime, which correspond to CeO 2 stretching vibration. The dielectric constant (ε r ) and dielectric loss (tan δ) values of sintered CeO 2 compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz.

J. Mater. Chem. C, 2015

Titanium dioxide (TiO 2 ) nanomaterials are attracting increasing interest, mostly because of the... more Titanium dioxide (TiO 2 ) nanomaterials are attracting increasing interest, mostly because of their superior photocatalytic and antibacterial properties. In this work, we report the synthesis, by a ''green'' aqueous sol-gel route, of TiO 2 doped with Eu and Nd (1 and 5 mol%), in order to extend its photocatalytic activity to the visible range, and also take advantage of the luminescent features of the rare earth metals (REs).

Construction and Building Materials, 2015

highlights DoE was used to formulate mortars with nano-TiO 2 and poliacrilonitrile fibers. The us... more highlights DoE was used to formulate mortars with nano-TiO 2 and poliacrilonitrile fibers. The use of rheometry can play a relevant role on the final properties. Mortars with similar initial yield stress and workability diverged over time. Rheology was governed by nano-TiO 2 . Mechanical properties were mainly influenced by poliacrilonitrile fibers.

CrystEngComm, 2015

Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (ti... more Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (titania, TiO 2 ) being widely used for various applications, such as light-to-energy conversion and storage, and photocatalysis. In this work, TiO 2 has been synthesised via an aqueous sol-gel method, using three different mineral acids (HNO 3 , HCl and HBr) to peptise the sol, and hence provide counter-ions. Dried sols were thermally treated at three different temperatures (450, 600 and 800°C), using three different dwell times (2, 4, and 8 h). Advanced X-ray methods were used to monitor the effect that the counter-ions had on the anatase-to-rutile phase transformation (ART). Quantitative phase analysis (QPA) using the Rietveld method was applied to assess the true amount of crystalline phases in the systems, and the amount of amorphous phase. Furthermore, the average crystalline domain diameter was also investigated, using whole powder pattern modelling (WPPM). With the advanced XRPD data (actual crystalline phase weight fraction in the samples and their average domain diameter and size distribution), it was possible to carry out a semiquantitative study of the ART transformation kinetics. At a low temperature of 75°C, the Cl − counter-ion was the most favourable to obtain anatase as the major crystalline phase, delaying the onset of the ART. Conversely, the Br − ions, maintained more anatase at 450°C, with a lower ART rate. In general, halides were more effective in delaying the ART than NO 3 − counterions. Moreover, we observed an inverse linear relationship between the lattice volume expansion of rutile and the increase of its crystalline domain size at 450 and 600°C isotherms. As the domain sizes increased with temperature, this effect reversed and became a direct linear dependence at the 800°C isotherm, suggesting a critical size limit <90 nm for this effect.

Phys. Chem. Chem. Phys, 2014

RSC Adv., 2014

A novel, facile method based on a non-aqueous sol-gel solvothermal process has been developed to ... more A novel, facile method based on a non-aqueous sol-gel solvothermal process has been developed to synthesise spherical TiO 2 nanoparticles (NPs) in one pot. The reaction between titanium(IV) tert-butoxide (Ti[OC(CH 3 ) 3 ] 4 ) and benzyl alcohol was a simple process, which resulted in the formation of highly crystalline titania NPs with a small size of only 6 nm, and with a correspondingly high surface area. The chemical formation mechanism of the metal oxide NPs has been proposed, and the degree of surface hydroxyls (-OH groups) has been examined. The products of the synthesis were characterised by X-ray powder diffraction (XRPD) using the advanced whole powder pattern modelling (WPPM) method, highresolution transmission electron microscopy (HR-TEM), thermo-gravimetric analysis (TGA), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) spectroscopy. The photocatalytic activity (PCA) was evaluated in both the liquid-solid phase, by monitoring the degradation of an organic dye (methylene blue (MB)) under UV-light irradiation, and in the gas-solid phase, by following the degradation of 2-propanol under UVand visible-light exposures. The synthesized titania powders not only exhibited excellent photocatalysis in the liquid-solid phase (under UV irradiation), but also possessed a superior PCA in the gas-solid phase under a visible-light exposure. The effects on the PCA of the very small crystalline domain size, surface composition and the presence of organic molecules due to the synthesis process of the TiO 2 NPs were shown to account for this behaviour.

Journal of Materials Chemistry A, 2013

Calcium phosphate based materials of natural origin with photocatalytic properties were produced.... more Calcium phosphate based materials of natural origin with photocatalytic properties were produced. Bones of Atlantic cod fish were treated in appropriate solutions (either Ca-or Ti-containing salts) and successively annealed. Results showed multiphasic materials (hydroxyapatite, b-tricalcium phosphate and anatase titania) with excellent photocatalytic performance under both UV and visible light, with an anatase concentration of only about 2 mol%. Results with such a low amount of anatase have never been reported before for a calcium phosphate-based material; this is attributed to the presence of anatase being mainly on the surface. Single-phase hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 or HAp) also showed some photocatalytic properties and antibacterial activity.

Journal of Materials Chemistry B, 2 (2014) 5999-6009, 2014

The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful... more The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful UVA and UVB rays, is becoming an increasingly important issue. Such products are usually based on TiO 2 or ZnO, although both Fe 2 O 3 and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) doped with metal ions have been reported as being ultraviolet (UV) absorbing materials. HAp is the main component of bone; it is, therefore, highly biocompatible. In the present work, an iron-doped HAp-based material, containing both Fe ions substituted into the HAp structure and iron oxide in hematite (a-Fe 2 O 3 ) form, was successfully developed from waste cod fish bones. This was achieved through a simple process of treating the bones in a Fe(II) containing solution, followed by heating at 700 C. The material showed good absorption in the whole UV range and did not form radicals when irradiated. The sunscreen cream formulated with this material could be used as a broad sunscreen protector (l crit > 370 nm), showing high absorption both in the UVA and UVB ranges. Because of its absorption properties it would be classified as 5 star protection according to the Boots UVA star rating system. The cream is also photostable, and does not cause irritation or erythema formation when in contact with the human skin.

Materials Letters, 2014

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

In this paper, phosphate-based compounds used in biomedicine were extracted from bones and scales... more In this paper, phosphate-based compounds used in biomedicine were extracted from bones and scales of European sardines (Sardina pilchardus); this is the first time that different parts of the same fish are used for the extraction of these kinds of materials. The bones and scales behave very differently with processing, producing different materials when annealed between 600 and 1000 1C.

Catalysis Science and Technology, 2014

Titanium dioxide (TiO 2 ) nanoparticles are attracting increasing interest because of their super... more Titanium dioxide (TiO 2 ) nanoparticles are attracting increasing interest because of their superior photocatalytic and antibacterial properties. Here, aqueous titanium oxy-hydroxide sols were made, using a green synthesis method, from the controlled hydrolysis/peptisation of titanium isopropoxide. Three different mineral acids were used to peptise the sol (HNO 3 , HBr and HCl), and provide counter-ions. The influence of nitrate or halide sol counter-ions on size distributions of the starting sols were measured via photon correlation spectroscopy (PCS). Semi-quantitative phase composition analysis (QPA), on the gels thermally treated at 450 and 600°C, was carried out via Rietveld refinement of the X-ray powder diffraction (XRD) patterns. Photocatalytic activity of the prepared samples was also assessed, in the gas-solid phase, monitoring NO x degradation using both solar and white lamps (artificial indoor lightning). Both halides (chlorine or bromine) encouraged the anatase-to-rutile phase transition (ART), resulting in powders containing up to 77 wt% rutile and only 5 wt% brookite after heating to only 450°C, with particle sizes 50 nm, and these produced 100% rutile at 600°C. Photocatalytic tests in the gas phase, using a white lamp, showed that the halide-stabilised sols, thermally treated at 450°C, gave titania with the highest NO x conversion ratetwice that of Degussa P25.

Journal of Photochemistry and Photobiology, 296 (2015) 40-47, 2015

Fish bones were converted into materials consisting of silver phosphate (Ag 3 PO 4 ), b-calcium p... more Fish bones were converted into materials consisting of silver phosphate (Ag 3 PO 4 ), b-calcium phosphate (b-Ca 3 (PO 4 ) 2 , b-TCP) and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp), as well as of metallic silver (Ag 0 ), with a simple treatment in solution and calcination (650 or 1000 C). The antibacterial activity of the material was measured in the dark and under UV and white light irradiation; this is the first time that an Ag 3 PO 4based material was tested under these conditions. Results showed light-enhanced antibacterial properties toward Gram-positive and Gram-negative strains (Methicillin-resistant Staphylococcus aureus -MRSA, Escherichia coli,Pseudomonas aeruginosa), with inactivation rates of up to 99.999% under UV light, and 99% for E. coli under white light (artificial indoor lighting). The photocatalytic activity was also tested, and the degradation of methylene blue dye was observed under both UV and white light. Even if the MB degradation was to a smaller extent under white light, it was approximately twice that of the commercial photocatalyst P25. This work demonstrates the valorisation of a food industry by-product such as fish bones to form a potentially valuable material, with important applications in self sterilizing surfaces and environmental remediation.

Journal of Materials Chemistry B, 3 (2015) 399-407, 2015

ABSTRACT There is a need to detect low (a few ppm) levels of anesthetics in surgical and hospital... more ABSTRACT There is a need to detect low (a few ppm) levels of anesthetics in surgical and hospital environments, as residual anesthetic vapors can pose a serious health risk to both medical staff and patients. Currently, the most common surgical anesthetic is the volatile halogenataed compound sevoflurane (C4H3F7O), and there is an urgent need for a versatile, low cost, fast and sensitive method to detect this gas. In this paper, we report for the first time the use of metal oxide semiconductors for the detection of halogenated anesthetic vapors, specifically the use of indium oxide (In2O3) nanoparticles (NPs) as sensors for low levels of sevoflurane. A novel non-aqueous sol–gel route for synthesizing pure In2O3 NPs was developed, using indium acetylacetonate as a precursor and n-butylamine as a reactive solvent, under solvothermal conditions. This is a relatively simple synthesis at 140 ºC / 4hr, which requires no surfactant capping agents or subsequent annealing for form good quality crystalline NPs, and the mechanism is explained in detail. These In2O3 NPs were quasi-spherical in shape, being around 7 nm in diameter as prepared and 9.5 nm after thermal treatment at 250 °C. The In2O3 NPs were characterized by an advanced X-ray method (whole powder pattern modeling, WPPM) which gives detailed nanostructural information, and high-resolution transmission electron microscopy (HR-TEM), which showed the exclusive presence of pure In2O3. Diffuse reflectance spectroscopy (DRS) was used to determine the optical band gap (Eg) of the sample. The In2O3 NPs were tested as highly sensitive sensing interfaces to provide resistance changes during exposure to a gas phase. In this case, the NPs were used to successfully detect sevoflurane, and the In2O3 NP sensor demonstrated a good response and fast response/recovery time towards very low concentrations of sevoflurane in air (~1-10 ppm), suggesting a very attractive application as a real-time monitoring anesthetic sensor in hospital, surgical and medical environments.

Journal of Physical Chemistry Letters 7 (2016) 4039-4046, Sep 27, 2016

We present for the first time a nonaqueous sol–gel route to produce ultrasmall (<2 nm) magnetic b... more We present for the first time a nonaqueous sol–gel route to produce ultrasmall (<2 nm) magnetic bimetallic CoPt3 nanoparticles (NPs). The one-pot procedure is carried out at low temperature (180 °C) using benzyl alcohol, acting as both reducing agent and solvent. The highly monodisperse CoPt3 NPs were investigated with innovative advanced X-ray methods (whole powder pattern modeling), HR-STEM, XPS, and SQUID magnetometry. XPS showed Co was mostly in metallic form, but with a very small amount of CoO on the NP surface. The spherical NPs had an ultrasmall diameter of 1.6 nm and could self-assemble in aligned linear chains, or nanobelts, of single NPs. They are superparamagnetic, with blocking temperature of ∼20 K and coercivity at 10 K of 27.9 kA m–1 (∼350 Oe). However, there is evidence of a second magnetic phase (probably CoO) in the ZFC magnetization curve, which enhances their magnetization values, without significantly affecting their superparamagnetism.

Solid State Sciences, 2007

Pseudobrookite pigments were synthesised by the conventional ceramic route, calcining at 1300 °C ... more Pseudobrookite pigments were synthesised by the conventional ceramic route, calcining at 1300 °C four mixtures, with a Fe 2 O 3 :TiO 2 ratio ranging from 47:53 to 40:60, and were characterised by XRPD, DRS and coloring performance in several ceramic matrices. Titania in moderate excess of the Fe 2 TiO 5 stoichiometry, necessary to minimise the occurrence of unreacted precursors, induced lattice parameters smaller than ideal pseudobrookite, in agreement with the different radii of Ti 4+ and Fe 3+ ions.

Journal of Solid State Chemistry, 2007

Karrooite, MgTi2O5, is a promising ceramic pigment due to its high refractoriness and refractive ... more Karrooite, MgTi2O5, is a promising ceramic pigment due to its high refractoriness and refractive indices, as well as its ability to host transition metal ions in two crystallographically distinct octahedral sites. The colouring performance was investigated combining X-ray powder diffraction with UV–vis–NIR spectroscopy on karrooite doped with V, Cr, Mn, Fe, Co or Ni (M) according to the formula Mg1−xTi2−xM2xO5,

Journal of Solid State Chemistry, 2015

Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution... more Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO2 has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO2 to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO2 lattice using our green sol-gel nanosynthesis method, used to create 10 nm TiO2 NPs. Two parallel routes were studied to produce nitrogen-modified TiO2 nanoparticles (NPs), using HNO3+NH3 (acid-precipitated base-peptised) and NH4OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800°C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NOx) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NOx abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450°C, and NPs heated to 450°C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO2 NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice

Ceramics International, 2015

Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 -HAp) is a common material for bone replacement in artific... more Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 -HAp) is a common material for bone replacement in artificial implants and prostheses, due to its high biocompatibility. In this work we report about the preparation of HAp-based materials of marine origin with antibacterial properties. Bones from cod fish (Gadhus morua) were treated with a dilute AgNO 3 solution, to obtain HAp-containing samples with silver as a minor component. The samples were characterised by XRD, FT-IR spectroscopy and SEM, indicating the presence of HAp, β-TCP and some metallic silver. The determination of unit cell parameters, however, indicated that the majority of silver is substituted in the β-TCP lattice in ionic form. The antibacterial activity of these materials was tested towards both Gram-positive and Gram-negative bacterias; results showed that the material is very effective with Gram-negative strains such as Escherichia coli (inactivation rates of 99.82% and 99.999% after 2 and 5 h, respectively) and had a smaller but still significant effect on Gram-positive MRSA (91% inactivation rate). These results show the potentials of these samples as infection-resistant bone replacement materials.

PLOS ONE, 2015

[This corrects the article DOI: 10.1371/journal.pone.0122989.].

PLOS ONE, 2015

A template-free precipitation method was used as a simple and low cost method for preparation of ... more A template-free precipitation method was used as a simple and low cost method for preparation of CeO 2 nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO 2 nanoparticles. The FT-IR spectrum of prepared CeO 2 nanoparticles showed absorption bands at 400 cm -1 to 450 cm -1 regime, which correspond to CeO 2 stretching vibration. The dielectric constant (ε r ) and dielectric loss (tan δ) values of sintered CeO 2 compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz.

J. Mater. Chem. C, 2015

Titanium dioxide (TiO 2 ) nanomaterials are attracting increasing interest, mostly because of the... more Titanium dioxide (TiO 2 ) nanomaterials are attracting increasing interest, mostly because of their superior photocatalytic and antibacterial properties. In this work, we report the synthesis, by a ''green'' aqueous sol-gel route, of TiO 2 doped with Eu and Nd (1 and 5 mol%), in order to extend its photocatalytic activity to the visible range, and also take advantage of the luminescent features of the rare earth metals (REs).

Construction and Building Materials, 2015

highlights DoE was used to formulate mortars with nano-TiO 2 and poliacrilonitrile fibers. The us... more highlights DoE was used to formulate mortars with nano-TiO 2 and poliacrilonitrile fibers. The use of rheometry can play a relevant role on the final properties. Mortars with similar initial yield stress and workability diverged over time. Rheology was governed by nano-TiO 2 . Mechanical properties were mainly influenced by poliacrilonitrile fibers.

CrystEngComm, 2015

Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (ti... more Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (titania, TiO 2 ) being widely used for various applications, such as light-to-energy conversion and storage, and photocatalysis. In this work, TiO 2 has been synthesised via an aqueous sol-gel method, using three different mineral acids (HNO 3 , HCl and HBr) to peptise the sol, and hence provide counter-ions. Dried sols were thermally treated at three different temperatures (450, 600 and 800°C), using three different dwell times (2, 4, and 8 h). Advanced X-ray methods were used to monitor the effect that the counter-ions had on the anatase-to-rutile phase transformation (ART). Quantitative phase analysis (QPA) using the Rietveld method was applied to assess the true amount of crystalline phases in the systems, and the amount of amorphous phase. Furthermore, the average crystalline domain diameter was also investigated, using whole powder pattern modelling (WPPM). With the advanced XRPD data (actual crystalline phase weight fraction in the samples and their average domain diameter and size distribution), it was possible to carry out a semiquantitative study of the ART transformation kinetics. At a low temperature of 75°C, the Cl − counter-ion was the most favourable to obtain anatase as the major crystalline phase, delaying the onset of the ART. Conversely, the Br − ions, maintained more anatase at 450°C, with a lower ART rate. In general, halides were more effective in delaying the ART than NO 3 − counterions. Moreover, we observed an inverse linear relationship between the lattice volume expansion of rutile and the increase of its crystalline domain size at 450 and 600°C isotherms. As the domain sizes increased with temperature, this effect reversed and became a direct linear dependence at the 800°C isotherm, suggesting a critical size limit <90 nm for this effect.

Phys. Chem. Chem. Phys, 2014

RSC Adv., 2014

A novel, facile method based on a non-aqueous sol-gel solvothermal process has been developed to ... more A novel, facile method based on a non-aqueous sol-gel solvothermal process has been developed to synthesise spherical TiO 2 nanoparticles (NPs) in one pot. The reaction between titanium(IV) tert-butoxide (Ti[OC(CH 3 ) 3 ] 4 ) and benzyl alcohol was a simple process, which resulted in the formation of highly crystalline titania NPs with a small size of only 6 nm, and with a correspondingly high surface area. The chemical formation mechanism of the metal oxide NPs has been proposed, and the degree of surface hydroxyls (-OH groups) has been examined. The products of the synthesis were characterised by X-ray powder diffraction (XRPD) using the advanced whole powder pattern modelling (WPPM) method, highresolution transmission electron microscopy (HR-TEM), thermo-gravimetric analysis (TGA), UV-visible diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) spectroscopy. The photocatalytic activity (PCA) was evaluated in both the liquid-solid phase, by monitoring the degradation of an organic dye (methylene blue (MB)) under UV-light irradiation, and in the gas-solid phase, by following the degradation of 2-propanol under UVand visible-light exposures. The synthesized titania powders not only exhibited excellent photocatalysis in the liquid-solid phase (under UV irradiation), but also possessed a superior PCA in the gas-solid phase under a visible-light exposure. The effects on the PCA of the very small crystalline domain size, surface composition and the presence of organic molecules due to the synthesis process of the TiO 2 NPs were shown to account for this behaviour.

Journal of Materials Chemistry A, 2013

Calcium phosphate based materials of natural origin with photocatalytic properties were produced.... more Calcium phosphate based materials of natural origin with photocatalytic properties were produced. Bones of Atlantic cod fish were treated in appropriate solutions (either Ca-or Ti-containing salts) and successively annealed. Results showed multiphasic materials (hydroxyapatite, b-tricalcium phosphate and anatase titania) with excellent photocatalytic performance under both UV and visible light, with an anatase concentration of only about 2 mol%. Results with such a low amount of anatase have never been reported before for a calcium phosphate-based material; this is attributed to the presence of anatase being mainly on the surface. Single-phase hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 or HAp) also showed some photocatalytic properties and antibacterial activity.

Journal of Materials Chemistry B, 2 (2014) 5999-6009, 2014

The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful... more The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful UVA and UVB rays, is becoming an increasingly important issue. Such products are usually based on TiO 2 or ZnO, although both Fe 2 O 3 and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) doped with metal ions have been reported as being ultraviolet (UV) absorbing materials. HAp is the main component of bone; it is, therefore, highly biocompatible. In the present work, an iron-doped HAp-based material, containing both Fe ions substituted into the HAp structure and iron oxide in hematite (a-Fe 2 O 3 ) form, was successfully developed from waste cod fish bones. This was achieved through a simple process of treating the bones in a Fe(II) containing solution, followed by heating at 700 C. The material showed good absorption in the whole UV range and did not form radicals when irradiated. The sunscreen cream formulated with this material could be used as a broad sunscreen protector (l crit > 370 nm), showing high absorption both in the UVA and UVB ranges. Because of its absorption properties it would be classified as 5 star protection according to the Boots UVA star rating system. The cream is also photostable, and does not cause irritation or erythema formation when in contact with the human skin.

Materials Letters, 2014

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

In this paper, phosphate-based compounds used in biomedicine were extracted from bones and scales... more In this paper, phosphate-based compounds used in biomedicine were extracted from bones and scales of European sardines (Sardina pilchardus); this is the first time that different parts of the same fish are used for the extraction of these kinds of materials. The bones and scales behave very differently with processing, producing different materials when annealed between 600 and 1000 1C.

Catalysis Science and Technology, 2014

Titanium dioxide (TiO 2 ) nanoparticles are attracting increasing interest because of their super... more Titanium dioxide (TiO 2 ) nanoparticles are attracting increasing interest because of their superior photocatalytic and antibacterial properties. Here, aqueous titanium oxy-hydroxide sols were made, using a green synthesis method, from the controlled hydrolysis/peptisation of titanium isopropoxide. Three different mineral acids were used to peptise the sol (HNO 3 , HBr and HCl), and provide counter-ions. The influence of nitrate or halide sol counter-ions on size distributions of the starting sols were measured via photon correlation spectroscopy (PCS). Semi-quantitative phase composition analysis (QPA), on the gels thermally treated at 450 and 600°C, was carried out via Rietveld refinement of the X-ray powder diffraction (XRD) patterns. Photocatalytic activity of the prepared samples was also assessed, in the gas-solid phase, monitoring NO x degradation using both solar and white lamps (artificial indoor lightning). Both halides (chlorine or bromine) encouraged the anatase-to-rutile phase transition (ART), resulting in powders containing up to 77 wt% rutile and only 5 wt% brookite after heating to only 450°C, with particle sizes 50 nm, and these produced 100% rutile at 600°C. Photocatalytic tests in the gas phase, using a white lamp, showed that the halide-stabilised sols, thermally treated at 450°C, gave titania with the highest NO x conversion ratetwice that of Degussa P25.

Journal of Photochemistry and Photobiology, 296 (2015) 40-47, 2015

Fish bones were converted into materials consisting of silver phosphate (Ag 3 PO 4 ), b-calcium p... more Fish bones were converted into materials consisting of silver phosphate (Ag 3 PO 4 ), b-calcium phosphate (b-Ca 3 (PO 4 ) 2 , b-TCP) and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp), as well as of metallic silver (Ag 0 ), with a simple treatment in solution and calcination (650 or 1000 C). The antibacterial activity of the material was measured in the dark and under UV and white light irradiation; this is the first time that an Ag 3 PO 4based material was tested under these conditions. Results showed light-enhanced antibacterial properties toward Gram-positive and Gram-negative strains (Methicillin-resistant Staphylococcus aureus -MRSA, Escherichia coli,Pseudomonas aeruginosa), with inactivation rates of up to 99.999% under UV light, and 99% for E. coli under white light (artificial indoor lighting). The photocatalytic activity was also tested, and the degradation of methylene blue dye was observed under both UV and white light. Even if the MB degradation was to a smaller extent under white light, it was approximately twice that of the commercial photocatalyst P25. This work demonstrates the valorisation of a food industry by-product such as fish bones to form a potentially valuable material, with important applications in self sterilizing surfaces and environmental remediation.

Journal of Materials Chemistry B, 3 (2015) 399-407, 2015

ABSTRACT There is a need to detect low (a few ppm) levels of anesthetics in surgical and hospital... more ABSTRACT There is a need to detect low (a few ppm) levels of anesthetics in surgical and hospital environments, as residual anesthetic vapors can pose a serious health risk to both medical staff and patients. Currently, the most common surgical anesthetic is the volatile halogenataed compound sevoflurane (C4H3F7O), and there is an urgent need for a versatile, low cost, fast and sensitive method to detect this gas. In this paper, we report for the first time the use of metal oxide semiconductors for the detection of halogenated anesthetic vapors, specifically the use of indium oxide (In2O3) nanoparticles (NPs) as sensors for low levels of sevoflurane. A novel non-aqueous sol–gel route for synthesizing pure In2O3 NPs was developed, using indium acetylacetonate as a precursor and n-butylamine as a reactive solvent, under solvothermal conditions. This is a relatively simple synthesis at 140 ºC / 4hr, which requires no surfactant capping agents or subsequent annealing for form good quality crystalline NPs, and the mechanism is explained in detail. These In2O3 NPs were quasi-spherical in shape, being around 7 nm in diameter as prepared and 9.5 nm after thermal treatment at 250 °C. The In2O3 NPs were characterized by an advanced X-ray method (whole powder pattern modeling, WPPM) which gives detailed nanostructural information, and high-resolution transmission electron microscopy (HR-TEM), which showed the exclusive presence of pure In2O3. Diffuse reflectance spectroscopy (DRS) was used to determine the optical band gap (Eg) of the sample. The In2O3 NPs were tested as highly sensitive sensing interfaces to provide resistance changes during exposure to a gas phase. In this case, the NPs were used to successfully detect sevoflurane, and the In2O3 NP sensor demonstrated a good response and fast response/recovery time towards very low concentrations of sevoflurane in air (~1-10 ppm), suggesting a very attractive application as a real-time monitoring anesthetic sensor in hospital, surgical and medical environments.