Publications by authors named "Alberto Naldoni"

23 Publications

  • Page 1 of 1

Light-Induced Migration of Spin Defects in TiO Nanosystems and their Contribution to the H Evolution Catalysis from Water.

ChemSusChem 2021 Aug 12. Epub 2021 Aug 12.

Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacký University, Slechtitelů 27, 78371, Olomouc, Czech Republic.

The photocatalytic activity for H production from water, without presence of hole scavengers, of thermally reduced TiO nanoparticles (H-500, H-700) and neat anatase were followed by in-situ continuous-wave light-induced electron paramagnetic resonance technique (CW-LEPR), in order to correlate the H evolution rates with the electronic fingerprints of the photoexcited systems. Under UV irradiation, photoexcited electrons moved from the deep lattice towards the superficially exposed Ti sites. These photogenerated redox sites mediated (e +h ) recombination and were the crucial electronic factor affecting catalysis. In the best-performant system (H-500), a synergic combination of mobile electrons was observed, which dynamically created diverse types of Ti sites, including interstitial Ti , and singly ionized electrons trapped in oxygen vacancies (V ). The interplay of these species fed successfully surface exposed Ti sites, which became a catalytically active, fast reacting Ti ⇄Ti state that was key for the H evolution process.
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http://dx.doi.org/10.1002/cssc.202101218DOI Listing
August 2021

Syngas Evolution from CO Electroreduction by Porous Au Nanostructures.

ACS Appl Energy Mater 2020 May 6;3(5):4658-4668. Epub 2020 May 6.

Department of Chemical and Pharmaceutical Sciences, University of Ferrara, Via Luigi Borsari 46, 44121 Ferrara, Italy.

Electrocatalytic reduction of CO recently emerged as a viable solution in view of changing the common belief and considering carbon dioxide as a valuable reactant instead of a waste product. In this view, we herein propose the one-step synthesis of gold nanostructures of different morphologies grown on fluorine-doped tin oxide electrodes by means of pulsed-laser deposition. The resulting cathodes are able to produce syngas mixtures of different compositions at overpotentials as low as 0.31 V in CO-presaturated aqueous media. Insights into the correlation between the structural features/morphology of the cathodes and their catalytic activity are also provided, confirming recent reports on the remarkable sensitivity toward CO production for gold electrodes exposing undercoordinated sites and facets.
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http://dx.doi.org/10.1021/acsaem.0c00301DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8016180PMC
May 2020

Carboxylated Graphene for Radical-Assisted Ultra-Trace-Level Water Treatment and Noble Metal Recovery.

ACS Nano 2021 Feb 19;15(2):3349-3358. Epub 2021 Jan 19.

Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute, Palacký University, Křížkovského 511/8, 779 00 Olomouc, Czech Republic.

Sorption technologies, enabling removal of heavy metals, play a pivotal role in meeting the global demands for unrestricted access to drinking water. Standard sorption technologies suffer from limited efficiency related to the weak sorbent-metal interaction. Further challenges include the development of technologies enabling smart metal recovery and sorbent regeneration. To this end, a densely functionalized graphene, with 33% by mass content of carboxyl groups, linked through direct C-C bonds (graphene acid, GA) represents a previously unexplored solution to this challenge. GA revealed excellent efficiency for removal of highly toxic metals, such as Cd and Pb. Due to its selective chemistry, GA can bind heavy metals with high affinity, even at concentrations of 1 mg L and in the presence of competing ions of natural drinking water, and reduce them down to drinking water allowance levels of a few μg L. This is not only due to carboxyl groups but also due to the stable radical centers of the GA structure, enabling metal ion-radical interactions, as proved by EPR, XPS, and density functional theory calculations. GA offers full structural integrity during the highly acidic and basic treatment, which is exploited for noble metal recovery (Ga, In, Pd) and sorbent regeneration. Owing to these attributes, GA represents a fully reusable metal sorbent, applicable also in electrochemical energy technologies, as illustrated with a GA/Pt catalyst derived from Pt-contaminated water.
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http://dx.doi.org/10.1021/acsnano.0c10093DOI Listing
February 2021

Operando X-ray Absorption Spectroscopy (XAS) Observation of Photoinduced Oxidation in FeNi (Oxy)hydroxide Overlayers on Hematite (α-FeO) Photoanodes for Solar Water Splitting.

Langmuir 2020 Oct 22;36(39):11564-11572. Epub 2020 Sep 22.

Department of Materials Science and Engineering, Technion--Israel Institute of Technology, Haifa 3200003, Israel.

An FeNi (oxy)hydroxide cocatalyst overlayer was photoelectrochemically deposited on a thin-film hematite (α-FeO) photoanode, leading to a cathodic shift of ∼100 mV in the photocurrent onset potential. Operando X-ray absorption spectroscopy (XAS) at the Fe and Ni K-edges was used to study the changes in the overlayer with potential in the dark and under illumination conditions. Potential or illumination only had a minor effect on the Fe oxidation state, suggesting that Fe atoms do not accumulate significant amount of charge over the whole potential range. In contrast, the Ni K-edge spectra showed pronounced dependence on potential in the dark and under illumination. The effect of illumination is to shift the onset for the Ni oxidation because of the generated photovoltage and suggests that holes that are photogenerated in hematite are transferred mainly to the Ni atoms in the overlayer. The increase in the oxidation state of Ni proceeds at potentials corresponding to the redox wave of Ni, which occurs immediately prior to the onset of the oxygen evolution reaction (OER). Linear combination fitting analysis of the obtained spectra suggests that the overlayer does not have to be fully oxidized to promote oxygen evolution. Cathodic discharge measurements show that the photogenerated charge is stored almost exclusively in the Ni atoms within the volume of the overlayer.
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http://dx.doi.org/10.1021/acs.langmuir.0c02065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7586389PMC
October 2020

Solar Thermoplasmonic Nanofurnace for High-Temperature Heterogeneous Catalysis.

Nano Lett 2020 May 27;20(5):3663-3672. Epub 2020 Apr 27.

Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University Olomouc, Šlechtitelů 27, 78371 Olomouc, Czech Republic.

Most of existing solar thermal technologies require highly concentrated solar power to operate in the temperature range 300-600 °C. Here, thin films of refractory plasmonic TiN cylindrical nanocavities manufactured via flexible and scalable process are presented. The fabricated TiN films show polarization-insensitive 95% broadband absorption in the visible and near-infrared spectral ranges and act as plasmonic "nanofurnaces" capable of reaching temperatures above 600 °C under moderately concentrated solar irradiation (∼20 Suns). The demonstrated structures can be used to control nanometer-scale chemistry with zeptoliter (10 L) volumetric precision, catalyzing C-C bond formation and melting inorganic deposits. Also shown is the possibility to perform solar thermal CO oxidation at rates of 16 mol h m and with a solar-to-heat thermoplasmonic efficiency of 63%. Access to scalable, cost-effective refractory plasmonic nanofurnaces opens the way to the development of modular solar thermal devices for sustainable catalytic processes.
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http://dx.doi.org/10.1021/acs.nanolett.0c00594DOI Listing
May 2020

Selective Functionalization Blended with Scaffold Conductivity in Graphene Acid Promotes HO Electrochemical Sensing.

ACS Omega 2019 Nov 15;4(22):19944-19952. Epub 2019 Nov 15.

Department of Chemical and Pharmaceutical Sciences, INSTM and ICCOM-CNR, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy.

The widespread industrial use of HO has provoked great interest in the development of new and more efficient materials for its detection. Enzymatic electrochemical sensors have drawn particular attention, primarily because of their excellent selectivity. However, their high cost, instability, complex immobilization, and inherent tendency toward denaturation of the enzyme significantly limit their practical usefulness. Inspired by the powerful proton-catalyzed HO reduction mechanism of peroxidases, we have developed a well-defined and densely functionalized carboxylic graphene derivative (graphene acid, GA) that serves as a proton source and conductive electrode for binding and detecting HO. An unprecedented HO sensitivity of 525 μA cm mM is achieved by optimizing the balance between the carboxyl group content and scaffold conductivity of GA. Importantly, the GA sensor greatly outperforms all reported carbon-based HO sensors and is superior to enzymatic ones because of its simple immobilization, low cost, and uncompromised sensitivity even after continuous operation for 7 days. In addition, GA-based sensing electrodes remain highly selective in the presence of interferents such as ascorbic acid, paracetamol, and glucose, as well as complex matrices such as milk. GA-based sensors thus have considerable potential for use in practical industrial sensing technologies.
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http://dx.doi.org/10.1021/acsomega.9b02881DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6882107PMC
November 2019

Gap-plasmon enhanced water splitting with ultrathin hematite films: the role of plasmonic-based light trapping and hot electrons.

Faraday Discuss 2019 05 1;214:283-295. Epub 2019 Mar 1.

School of Electrical and Computer Engineering, Purdue University, IN-47907, USA. and Birck Nanotechnology Center, Purdue University, West Lafayette, IN-47907, USA.

Hydrogen is a promising alternative renewable fuel for meeting the growing energy demands of the world. Over the past few decades, photoelectrochemical water splitting has been widely studied as a viable technology for the production of hydrogen utilizing solar energy. A solar-to-hydrogen (STH) efficiency of 10% is considered to be sufficient for practical applications. Amongst the wide class of semiconductors that have been studied for their application in solar water splitting, iron oxide (α-FeO), or hematite, is one of the more promising candidate materials, with a theoretical STH efficiency of 15%. In this work, we show experimentally that by utilizing gold nanostructures that support gap-plasmon resonances together with a hematite layer, we can increase the water oxidation photocurrent by two times over that demonstrated by a bare hematite film at wavelengths above the hematite bandgap. Moreover, we achieve a six-fold increase in the oxidation photocurrent at near-infrared wavelengths, which is attributed to hot electron generation and decay in the gap-plasmon nanostructures. Theoretical simulations confirmed that the metamaterial geometry with gap plasmons that was used allows us to confine electromagnetic fields inside the hematite semiconductor and to enhance the surface photochemistry.
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http://dx.doi.org/10.1039/c8fd00148kDOI Listing
May 2019

Plasmon-Enhanced Photoelectrochemical Water Splitting for Efficient Renewable Energy Storage.

Adv Mater 2019 Aug 18;31(31):e1805513. Epub 2019 Feb 18.

Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University Olomouc, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.

Photoelectrochemical (PEC) water splitting is a promising approach for producing hydrogen without greenhouse gas emissions. Despite decades of unceasing efforts, the efficiency of PEC devices based on earth-abundant semiconductors is still limited by their low light absorption, low charge mobility, high charge-carrier recombination, and reduced diffusion length. Plasmonics has recently emerged as an effective approach for overcoming these limitations, although a full understanding of the involved physical mechanisms remains elusive. Here, the reported plasmonic effects are outlined, such as resonant energy transfer, scattering, hot electron injection, guided modes, and photonic effects, as well as the less investigated catalytic and thermal effects used in PEC water splitting. In each section, the fundamentals are reviewed and the most representative examples are discussed, illustrating possible future developments for achieving improved efficiency of plasmonic photoelectrodes.
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http://dx.doi.org/10.1002/adma.201805513DOI Listing
August 2019

Photocatalysis with Reduced TiO: From Black TiO to Cocatalyst-Free Hydrogen Production.

ACS Catal 2019 Jan 30;9(1):345-364. Epub 2018 Nov 30.

Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University Olomouc, Šlechtitelů 27, 78371 Olomouc, Czech Republic.

Black TiO nanomaterials have recently emerged as promising candidates for solar-driven photocatalytic hydrogen production. Despite the great efforts to synthesize highly reduced TiO, it is apparent that intermediate degree of reduction (namely, gray titania) brings about the formation of peculiar defective catalytic sites enabling cocatalyst-free hydrogen generation. A precise understanding of the structural and electronic nature of these catalytically active sites is still elusive, as well as the fundamental structure-activity relationships that govern formation of crystal defects, increased light absorption, charge separation, and photocatalytic activity. In this Review, we discuss the basic concepts that underlie an effective design of reduced TiO photocatalysts for hydrogen production such as (i) defects formation in reduced TiO, (ii) analysis of structure deformation and presence of unpaired electrons through electron paramagnetic resonance spectroscopy, (iii) insights from surface science on electronic singularities due to defects, and (iv) the key differences between black and gray titania, that is, photocatalysts that require Pt-modification and cocatalyst-free photocatalytic hydrogen generation. Finally, future directions to improve the performance of reduced TiO photocatalysts are outlined.
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http://dx.doi.org/10.1021/acscatal.8b04068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6344061PMC
January 2019

Sb-Doped SnO Nanorods Underlayer Effect to the α-Fe O Nanorods Sheathed with TiO for Enhanced Photoelectrochemical Water Splitting.

Small 2018 May 14;14(19):e1703860. Epub 2018 Apr 14.

Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University, Slechtitelu 11, 783 71, Olomouc, Czech Republic.

Here, a Sb-doped SnO (ATO) nanorod underneath an α-Fe O nanorod sheathed with TiO for photoelectrochemical (PEC) water splitting is reported. The experimental results, corroborated with theoretical analysis, demonstrate that the ATO nanorod underlayer effect on the α-Fe O nanorod sheathed with TiO enhances the PEC water splitting performance. The growth of the well-defined ATO nanorods is reported as a conductive underlayer to improve α-Fe O PEC water oxidation performance. The α-Fe O nanorods grown on the ATO nanorods exhibit improved performance for PEC water oxidation compared to α-Fe O grown on flat fluorine-doped tin oxide glass. Furthermore, a simple and facile TiCl chemical treatment further introduces TiO passivation layer formation on the α-Fe O to reduce surface recombination. As a result, these unique nanostructures show dramatically improved photocurrent density (139% higher than that of the pure hematite nanorods).
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http://dx.doi.org/10.1002/smll.201703860DOI Listing
May 2018

Hematite Photoanode with Complex Nanoarchitecture Providing Tunable Gradient Doping and Low Onset Potential for Photoelectrochemical Water Splitting.

ChemSusChem 2018 Jun 26;11(11):1873-1879. Epub 2018 Apr 26.

Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University, 17. listopadu 1192/12, 771 46, Olomouc, Czech Republic.

Over the past years, α-Fe O (hematite) has re-emerged as a promising photoanode material in photoelectrochemical (PEC) water splitting. In spite of considerable success in obtaining relatively high solar conversion efficiency, the main drawbacks hindering practical application of hematite are its intrinsically hampered charge transport and sluggish oxygen evolution reaction (OER) kinetics on the photoelectrode surface. In the present work, we report a strategy that synergistically addresses both of these critical limitations. Our approach is based on three key features that are applied simultaneously: i) a careful nanostructuring of the hematite photoanode in the form of nanorods, ii) doping of hematite by Sn ions using a controlled gradient, and iii) surface decoration of hematite by a new class of layered double hydroxide (LDH) OER co-catalysts based on Zn-Co LDH. All three interconnected forms of functionalization result in an extraordinary cathodic shift of the photocurrent onset potential by more than 300 mV and a PEC performance that reaches a photocurrent density of 2.00 mA cm at 1.50 V vs. the reversible hydrogen electrode.
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http://dx.doi.org/10.1002/cssc.201800256DOI Listing
June 2018

Applying plasmonics to a sustainable future.

Science 2017 Jun;356(6341):908-909

Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA.

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http://dx.doi.org/10.1126/science.aan5802DOI Listing
June 2017

Observation of charge transfer cascades in α-FeO/IrO photoanodes by operando X-ray absorption spectroscopy.

Phys Chem Chem Phys 2017 Feb;19(8):5715-5720

Istituto Nazionale di Scienza e Tecnologia dei Materiali - INSTM, Via Giusti 9, Firenze, Italy and Dipartimento di Chimica, Università di Pavia, Viale Taramelli 16, 27100, Pavia, Italy.

Electrochemical devices for energy conversion and storage are central for a sustainable economy. The performance of electrodes is driven by charge transfer across different layer materials and an understanding of the mechanistics is pivotal to gain improved efficiency. Here, we directly observe the transfer of photogenerated charge carriers in a photoanode made of hematite (α-FeO) and a hydrous iridium oxide (IrO) overlayer, which plays a key role in photoelectrochemical water oxidation. Through the use of operando X-ray absorption spectroscopy (XAS), we probe the change in occupancy of the Ir 5d levels during optical band gap excitation of α-FeO. At potentials where no photocurrent is observed, electrons flow from the α-FeO photoanode to the IrO overlayer. In contrast, when the composite electrode produces a sustained photocurrent (i.e., 1.4 V vs. RHE), a significant transfer of holes from the illuminated α-FeO to the IrO layer is clearly demonstrated. The analysis of the operando XAS spectra further suggests that oxygen evolution actually occurs both at the α-FeO/electrolyte and α-FeO/IrO interfaces. These findings represent an important outcome for a better understanding of composite photoelectrodes and their use in photoelectrochemical systems, such as hydrogen generation or CO reduction from sunlight.
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http://dx.doi.org/10.1039/c6cp08053gDOI Listing
February 2017

Copper NPs decorated titania: A novel synthesis by high energy US with a study of the photocatalytic activity under visible light.

Ultrason Sonochem 2016 Jul 15;31:295-301. Epub 2016 Jan 15.

GranitiFiandre SpA, Castellarano (MO), Italy.

The most important drawback of the use of TiO2 as photocatalyst is its lack of activity under visible light. To overcome this problem, the surface modification of commercial micro-sized TiO2 by means of high-energy ultrasound (US), employing CuCl2 as precursor molecule to obtain both metallic copper as well as copper oxides species at the TiO2 surface, is here. We have prepared samples with different copper content, in order to evaluate its impact on the photocatalytic performances of the semiconductor, and studied in particular the photodegradation in the gas phase of some volatile organic molecules (VOCs), namely acetone and acetaldehyde. We used a LED lamp in order to have only the contribution of the visible wavelengths to the TiO2 activation (typical LED lights have no emission in the UV region). We employed several techniques (i.e., HR-TEM, XRD, FT-IR and UV-Vis) in order to characterize the prepared samples, thus evidencing different sample morphologies as a function of the various copper content, with a coherent correlation between them and the photocatalytic results. Firstly, we demonstrated the possibility to use US to modify the TiO2, even when it is commercial and micro-sized as well; secondly, by avoiding completely the UV irradiation, we confirmed that pure TiO2 is not activated by visible light. On the other hand, we showed that copper metal and metal oxides nanoparticles strongly and positively affect its photocatalytic activity.
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http://dx.doi.org/10.1016/j.ultsonch.2016.01.015DOI Listing
July 2016

3D-printed photo-spectroelectrochemical devices for in situ and in operando X-ray absorption spectroscopy investigation.

J Synchrotron Radiat 2016 Mar 2;23(2):622-8. Epub 2016 Feb 2.

Dipartimento di Chimica, Università di Pavia, Via Taramelli 16, Pavia 27100, Italy.

Three-dimensional printed multi-purpose electrochemical devices for X-ray absorption spectroscopy are presented in this paper. The aim of this work is to show how three-dimensional printing can be a strategy for the creation of electrochemical cells for in situ and in operando experiments by means of synchrotron radiation. As a case study, the description of two cells which have been employed in experiments on photoanodes for photoelectrochemical water splitting are presented. The main advantages of these electrochemical devices are associated with their compactness and with the precision of the three-dimensional printing systems which allows details to be obtained that would otherwise be difficult. Thanks to these systems it was possible to combine synchrotron-based methods with complementary techniques in order to study the mechanism of the photoelectrocatalytic process.
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http://dx.doi.org/10.1107/S1600577515024480DOI Listing
March 2016

Probing long-lived plasmonic-generated charges in TiO2 /Au by high-resolution X-ray absorption spectroscopy.

Angew Chem Int Ed Engl 2015 Apr 6;54(18):5413-6. Epub 2015 Mar 6.

Department of Physics and Astronomy, University of Bologna, Viale Berti-Pichat 6/2, 40127 Bologna (Italy); ESRF-The European Synchrotron, 71 Avenue des Martyres, Grenoble 38000 (France).

Exploiting plasmonic Au nanoparticles to sensitize TiO2 to visible light is a widely employed route to produce efficient photocatalysts. However, a description of the atomic and electronic structure of the semiconductor sites in which charges are injected is still not available. Such a description is of great importance in understanding the underlying physical mechanisms and to improve the design of catalysts with enhanced photoactivity. We investigated changes in the local electronic structure of Ti in pure and N-doped nanostructured TiO2 loaded with Au nanoparticles during continuous selective excitation of the Au localized surface plasmon resonance with X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). Spectral variations strongly support the presence of long-lived charges localized on Ti states at the semiconductor surface, giving rise to new laser-induced low-coordinated Ti sites.
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http://dx.doi.org/10.1002/anie.201412030DOI Listing
April 2015

The critical role of intragap states in the energy transfer from gold nanoparticles to TiO2.

Phys Chem Chem Phys 2015 Feb;17(7):4864-9

CNR-Istituto di Scienze e Tecnologie Molecolari, Milano, Italy.

Cathodoluminescence spectroscopy is profitably exploited to study energy transfer mechanisms in Au and Pt/black TiO2 heterostructures. While Pt nanoparticles absorb light in the UV region, Au nanoparticles absorb light by surface plasmon resonance and interband transitions, both of them occurring in the visible region. The intra-bandgap states (oxygen vacancies) of black TiO2 play a key role in promoting both hot electron transfer and plasmonic resonant energy transfer from Au nanoparticles to the TiO2 semiconductor with a consequent photocatalytic H2 production increase. An innovative criterion is introduced for the design of plasmonic composites with increased efficiency under visible light.
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http://dx.doi.org/10.1039/c4cp05775aDOI Listing
February 2015

Hierarchical hematite nanoplatelets for photoelectrochemical water splitting.

ACS Appl Mater Interfaces 2014 Aug 16;6(15):11997-2004. Epub 2014 Jul 16.

CNR-Istituto di Scienze e Tecnologie Molecolari , Via C. Golgi 19, 20133 Milano, Italy.

A new nanostructured α-Fe2O3 photoelectrode synthesized through plasma-enhanced chemical vapor deposition (PE-CVD) is presented. The α-Fe2O3 films consist of nanoplatelets with (001) crystallographic planes strongly oriented perpendicular to the conductive glass surface. This hematite morphology was never obtained before and is strictly linked to the method being used for its production. Structural, electronic, and photocurrent measurements are employed to disclose the nanoscale features of the photoanodes and their relationships with the generated photocurrent. α-Fe2O3 films have a hierarchical morphology consisting of nanobranches (width ∼10 nm, length ∼50 nm) that self-organize in plume-like nanoplatelets (350-700 nm in length). The amount of precursor used in the PE-CVD process mainly affects the nanoplatelets dimension, the platelets density, the roughness, and the photoelectrochemical (PEC) activity. The highest photocurrent (j = 1.39 mA/cm(2) at 1.55 VRHE) is shown by the photoanodes with the best balance between the platelets density and roughness. The so obtained hematite hierarchical morphology assures good photocurrent performance and appears to be an ideal platform for the construction of customized multilayer architecture for PEC water splitting.
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http://dx.doi.org/10.1021/am5030287DOI Listing
August 2014

Porous TiO2 microspheres with tunable properties for photocatalytic air purification.

Ultrason Sonochem 2013 Jan 20;20(1):445-51. Epub 2012 Jul 20.

CNR-Istituto di Scienze e Tecnologie Molecolari, Via Golgi 19, 20133 Milano, Italy.

The synthesis of highly-crystalline porous TiO(2) microspheres is reported using ultrasonic spray pyrolysis (USP) in the presence of colloidal silica as a template. We have exploited the interactions between hot SiO(2) template particles surface and TiO(2) precursor that occur during reaction inside the droplets, to control the physical and chemical properties of the resulting particles. Varying the SiO(2) to titanium precursor molar ratio and the colloidal silica dimension, we obtained porous titania microspheres with tunable morphology, porosity, BET surface area, crystallite size, band-gap, and phase composition. In this regard, we have also observed the preferential formation of anatase vs. rutile with increasing initial surface area of the silica template. The porous TiO(2) microspheres were tested in the photocatalytic degradation of nitrogen oxides (NO(x)) in the gas phase. USP prepared nanostructured titania samples were found to have significantly superior specific activity per surface area compared to a commercial reference sample (P25 by Evonik-Degussa).
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http://dx.doi.org/10.1016/j.ultsonch.2012.07.003DOI Listing
January 2013

Effect of nature and location of defects on bandgap narrowing in black TiO2 nanoparticles.

J Am Chem Soc 2012 May 24;134(18):7600-3. Epub 2012 Apr 24.

CNR-Istituto di Scienze e Tecnologie Molecolari, Via C. Golgi 19, Milano 20133, Italy.

The increasing need for new materials capable of solar fuel generation is central in the development of a green energy economy. In this contribution, we demonstrate that black TiO(2) nanoparticles obtained through a one-step reduction/crystallization process exhibit a bandgap of only 1.85 eV, which matches well with visible light absorption. The electronic structure of black TiO(2) nanoparticles is determined by the unique crystalline and defective core/disordered shell morphology. We introduce new insights that will be useful for the design of nanostructured photocatalysts for energy applications.
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http://dx.doi.org/10.1021/ja3012676DOI Listing
May 2012

Alkaline phosphatase grafting on bioactive glasses and glass ceramics.

Acta Biomater 2010 Jan 18;6(1):229-40. Epub 2009 Jun 18.

Department of Materials Science and Chemical Engineering, Politecnico di Torino, C. so Duca degli Abruzzi 24, Torino 10129, Italy.

Bone integration of orthopaedic or dental implants and regeneration of damaged bone at the surgical site are still unresolved problems in prosthetic surgery. For this reason, biomimetic surfaces (i.e. both inorganic and biological bioactive surfaces) represent a challenge for bone implantation. In this research work a hydrolase enzyme (alkaline phosphatase) was covalently grafted to inorganic bioactive glass and glass ceramic surfaces, in order to impart biological bioactivity. The functionalized samples were analysed by means of X-ray photoelectron spectroscopy in order to verify enzyme presence on the surface. Enzyme activity was measured by means of UV-visual spectroscopy after reaction with the natural substrate. Scanning electron microscopy-energy-dispersive spectroscopy observations allowed monitoring of the morphological and chemical modification of the materials during the different steps of functionalization. In vitro inorganic bioactivity was investigated by soaking samples in simulated body fluid. Enzymatic activity of the samples was tested and compared before and after soaking. Enzymatic activity of the solution was monitored at different experimental times. This study demonstrates that alkaline phosphatase could be successfully grafted onto different bioactive surfaces while maintaining its activity. Presence of the enzyme in vitro enhances the inorganic bioactivity of the materials tested.
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http://dx.doi.org/10.1016/j.actbio.2009.06.025DOI Listing
January 2010

Photodegradation of Pollutants in Air: Enhanced Properties of Nano-TiO(2) Prepared by Ultrasound.

Nanoscale Res Lett 2008 Nov 25;4(2):97-105. Epub 2008 Nov 25.

Nanocrystalline TiO(2) samples were prepared by promoting the growth of a sol-gel precursor, in the presence of water, under continuous (CW), or pulsed (PW) ultrasound. All the samples turned out to be made of both anatase and brookite polymorphs. Pulsed US treatments determine an increase in the sample surface area and a decrease of the crystallite size, that is also accompanied by a more ordered crystalline structure and the samples appear to be more regular and can be considered to contain a relatively low concentration of lattice defects. These features result in a lower recombination rate between electrons and holes and, therefore, in a good photocatalytic performance toward the degradation of NO(x) in air. The continuous mode induces, instead, the formation of surface defects (two components are present in XPS Ti 2p(3/2) region) and consequently yields the best photocatalyst. The analysis of all the characterization data seems to suggest that the relevant parameter imposing the final features of the oxides is the ultrasound total energy per volume (E(tot)/V) and not the acoustic intensity or the pulsed/continuous mode.
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http://dx.doi.org/10.1007/s11671-008-9208-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2894369PMC
November 2008
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