Publications by authors named "Renato Figi"

12 Publications

  • Page 1 of 1

Multiscale Analysis of Metal Oxide Nanoparticles in Tissue: Insights into Biodistribution and Biotransformation.

Adv Sci (Weinh) 2020 Aug 18;7(15):2000912. Epub 2020 Jun 18.

Particles-Biology Interactions, Department of Materials Meet Life Swiss Federal Laboratories for Materials Science and Technology (Empa) Lerchenfeldstrasse 5 St. Gallen 9014 Switzerland.

Metal oxide nanoparticles have emerged as exceptionally potent biomedical sensors and actuators due to their unique physicochemical features. Despite fascinating achievements, the current limited understanding of the molecular interplay between nanoparticles and the surrounding tissue remains a major obstacle in the rationalized development of nanomedicines, which is reflected in their poor clinical approval rate. This work reports on the nanoscopic characterization of inorganic nanoparticles in tissue by the example of complex metal oxide nanoparticle hybrids consisting of crystalline cerium oxide and the biodegradable ceramic bioglass. A validated analytical method based on semiquantitative X-ray fluorescence and inductively coupled plasma spectrometry is used to assess nanoparticle biodistribution following intravenous and topical application. Then, a correlative multiscale analytical cascade based on a combination of microscopy and spectroscopy techniques shows that the topically applied hybrid nanoparticles remain at the initial site and are preferentially taken up into macrophages, form apatite on their surface, and lead to increased accumulation of lipids in their surroundings. Taken together, this work displays how modern analytical techniques can be harnessed to gain unprecedented insights into the biodistribution and biotransformation of complex inorganic nanoparticles. Such nanoscopic characterization is imperative for the rationalized engineering of safe and efficacious nanoparticle-based systems.
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http://dx.doi.org/10.1002/advs.202000912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7404155PMC
August 2020

Dual-porous cellulose nanofibril aerogels via modular drying and cross-linking.

Nanoscale 2020 Apr;12(13):7383-7394

Cellulose & Wood Materials Laboratory, Empa, Überlandstrasse 129, CH-8600, Dübendorf, Switzerland.

Nanofibrillar foams and aerogels are traditionally either macroporous with low surface area and high mechanical strength, or mesoporous with high surface area and low mechanical strength. In this work, an anionic cellulose nanofibril (CNF)-based dual-porous aerogel with BET specific surface area up to 430 m2 g-1 was prepared via a modular process combining directional freeze-thawing (creating macro-pores, ca. 50-200 μm) and supercritical drying (creating meso-pores, ca. 2-50 nm). Furthermore, by optionally utilizing both physical and chemical cross-linking strategies, aerogels with a Young's modulus of up to 711 kPa and good stability in aqueous conditions were demonstrated. By altering cross-linking strategies, the properties of resulting aerogels, such as hydrophilicity, mechanical strength and stability in water, can be precisely controlled for different applications. As a result, cationic methylene blue (MB) and metal ions (Ag+) were chosen as model species to investigate the absorption properties of the physically cross-linked aerogels in water. The aerogels showed a maximum adsorption of MB up to 234 mg g-1 and of Ag+ up to 116 mg g-1 as a result of the high specific surface area of the aerogels and their strong electrostatic interaction with the model species. Importantly, the hierarchical dual porosity of the aerogels enabled fast adsorption kinetics combined with a considerable adsorption capacity overall. Finally, it was shown that the adsorbed Ag+ could be converted to metallic Ag, demonstrating the additional functionality of these dual porous hybrid aerogels for antibacterial or catalytic applications.
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http://dx.doi.org/10.1039/d0nr00860eDOI Listing
April 2020

Multi-element chemical analysis of printed circuit boards - challenges and pitfalls.

Waste Manag 2019 Jun 20;92:124-136. Epub 2019 May 20.

Chair of Circular Economy and Recycling Technology at Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany.

Printed circuit boards (PCB) are an essential component of electrical and electronic equipment (EEE) and account for roughly 5% of the mass of EEE. Knowledge about the chemical composition of PCB is crucial to enable an enhanced recycling, especially for elements considered critical regarding their economic importance and supply risk (e.g. precious metals or specialty metals such as tantalum, germanium, gallium). No standard reference methods exist for determining the chemical composition of PCB. Previously published element mass fractions cover a wide range and were produced with numerous methods for sample preparation, digestion, and measurement. This impedes comparability of PCB composition from different studies. To investigate sample- and element-specific effects of applied methods a PCB sample from desktop PC was analysed in two separate labs. One lab applied sample- and element-specific validated methods (aqua regia, HF, HSO blend; ICP-OES, QQQ-ICP-MS), providing reference values, the other applied routine in-house methods (aqua regia; ICP-OES, ICP-MS) to assess the validity of in-house methods for chemical analysis of PCB. A t-test was used to identify elements depicting significant differences between validated and in-house methods. For base metals, in-house methods led to comparable results. For precious, specialty, and hazardous metals as well as REE investigated in this study, significant differences were detected. With respect to all results for in-house methods in this study, the combination of aqua regia and ICP-OES led to less significant differences than aqua regia and ICP-MS. The results show that sample- and element-specific quality assurance is crucial to prevent analytical bias.
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http://dx.doi.org/10.1016/j.wasman.2019.04.061DOI Listing
June 2019

High-performance carbon/MnO micromotors and their applications for pollutant removal.

Chemosphere 2019 Mar 7;219:427-435. Epub 2018 Dec 7.

Institute of Environmental Engineering, ETH Zurich, Schafmattstrasse 6, 8093, Zurich, Switzerland; Advanced Analytical Technologies Laboratory, EMPA, Überlandstrasse 129, 8600, Dübendorf, Switzerland. Electronic address:

The wide applications of particulate micromotors in practice, especially in the removal of environmental pollutants, have been limited by the low production yields and demand on high concentration of fuel such as HO. Carbon/MnO micromotors were made hydrothermally using different carbon allotropes including graphite, carbon nanotube (CNT), and graphene for treatment of methylene blue and toxic Ag ions. The obtained micromotors showed high speed of self-propulsion. The highest speed of MnO-based micromotors to date was observed for CNT/MnO (>2 mm/s, 5 wt% HO, 0.5 wt% surfactant). Moreover, different from previous studies, even with low HO concentration (0.5 wt%) and without surfactant addition, the micromotors could also be well dispersed in water by the O stream released from their reaction with HO. The carbon/MnO micromotors removed both methylene blue (>80%) and Ag ions (100%) effectively within 15 min by catalytic decomposition and adsorption. Especially high adsorption capacity of Ag (600 mg/g) was measured on graphite/MnO and graphene/MnO micromotors.
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http://dx.doi.org/10.1016/j.chemosphere.2018.12.051DOI Listing
March 2019

Refractive indices of layers and optical simulations of Cu(In,Ga)Se solar cells.

Sci Technol Adv Mater 2018 15;19(1):396-410. Epub 2018 May 15.

Laboratory for Thin films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.

Cu(In,Ga)Se based solar cells have reached efficiencies close to 23%. Further knowledge-driven improvements require accurate determination of the material properties. Here, we present refractive indices for all layers in Cu(In,Ga)Se solar cells with high efficiency. The optical bandgap of Cu(In,Ga)Se does not depend on the Cu content in the explored composition range, while the absorption coefficient value is primarily determined by the Cu content. An expression for the absorption spectrum is proposed, with Ga and Cu compositions as parameters. This set of parameters allows accurate device simulations to understand remaining absorption and carrier collection losses and develop strategies to improve performances.
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http://dx.doi.org/10.1080/14686996.2018.1458579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5954485PMC
May 2018

Functional lignocellulosic material for the remediation of copper(II) ions from water: Towards the design of a wood filter.

J Hazard Mater 2018 08 9;355:119-127. Epub 2018 May 9.

Wood Materials Science, ETH Zürich, Stefano-Franscini-Platz 3, CH-8093 Zürich, Switzerland; Applied Wood Materials, EMPA - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland. Electronic address:

In this study, the chemical modification of bulk beech wood is described along with its utilization as biosorbent for the remediation of copper from water. The material was prepared by esterification using anhydrides, and reaction conditions were optimized to propose a greener process, in particular by reducing the amount of solvent. This modification yields a lignocellulosic material whose native structure is preserved, with an increased amount of carboxylic groups (up to 3 mmol/g). We demonstrate that the material can remove up to 95% of copper from low concentration solutions (100- 500 ppm). The adsorption efficiency decreases with concentrated copper solutions, and we show that a limited number of -COOH groups participate in copper binding (ca. 0.1 Cu/-COOH). This result suggests a limited accessibility of -COOH groups in the wood scaffold. This was demonstrated by the characterization of -COOH and copper distributions inside wood. Raman and EDX imaging confirmed that most -COOH groups are located inside the wood cell walls, thereby limiting interactions with copper. According to this study, critical limitations of bulk wood as a biosorbent were identified, and the results will be used to improve the material and design an efficient wood filter for heavy metal remediation.
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http://dx.doi.org/10.1016/j.jhazmat.2018.05.015DOI Listing
August 2018

Differentiation of dental restorative materials combining energy-dispersive X-ray fluorescence spectroscopy and post-mortem CT.

Forensic Sci Med Pathol 2018 06 24;14(2):163-173. Epub 2018 Apr 24.

Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, Virtopsy, University of Zurich, CH-8057, Zurich, Switzerland.

Today, post-mortem computed tomography (CT) is routinely used for forensic identification. Mobile energy-dispersive X-ray fluorescence (EDXRF) spectroscopy of a dentition is a method of identification that has the potential to be easier and cheaper than CT, although it cannot be used with every dentition. In challenging cases, combining both techniques could facilitate the process of identification and prove to be advantageous over chemical analyses. Nine dental restorative material brands were analyzed using EDXRF spectroscopy. Their differentiability was assessed by comparing each material's x-ray fluorescence spectrum and then comparing the spectra to previous research investigating differentiability in CT. To verify EDXRF's precision and accuracy, select dental specimens underwent comparative electron beam excited x-ray spectroscopy (EDS) scans, while the impact of the restorative surface area was studied by scanning a row of dental specimens with varying restorative surface areas (n = 10). EDXRF was able to differentiate all 36 possible pairs of dental filling materials; however, dual-energy CT was only able to differentiate 33 out of 36. The EDS scans showed correlating x-ray fluorescence peaks on the x-ray spectra compared to our EDXRF. In addition, the surface area showed no influence on the differentiability of the dental filling materials. EDXRF has the potential to facilitate corpse identification by differentiating and comparing restorative materials, providing more information compared to post-mortem CT alone. Despite not being able to explicitly identify a brand without a control sample or database, its fast and mobile use could accelerate daily routines or mass victim identification processes. To achieve this goal, further development of EDXRF scanners for this application and further studies evaluating the method within a specific routine need to be performed.
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http://dx.doi.org/10.1007/s12024-018-9979-5DOI Listing
June 2018

Agglomeration potential of TiO in synthetic leachates made from the fly ash of different incinerated wastes.

Environ Pollut 2017 Apr 31;223:616-623. Epub 2017 Jan 31.

Institute of Environmental Engineering, ETH Zurich, Schafmattstrasse 6, 8093, Zurich, Switzerland; Advanced Analytical Technologies Laboratory, EMPA, Überlandstrasse 129, 8600, Dübendorf, Switzerland. Electronic address:

Material flow studies have shown that a large fraction of the engineered nanoparticles used in products end up in municipal waste. In many countries, this municipal waste is incinerated before landfilling. However, the behavior of engineered nanoparticles (ENPs) in the leachates of incinerated wastes has not been investigated so far. In this study, TiO ENPs were spiked into synthetic landfill leachates made from different types of fly ash from three waste incineration plants. The synthetic leachates were prepared by standard protocols and two types of modified procedures with much higher dilution ratios that resulted in reduced ionic strength. The pH of the synthetic leachates was adjusted in a wide range (i.e. pH 3 to 11) to understand the effects of pH on agglomeration. The experimental results indicated that agglomeration of TiO in the synthetic landfill leachate simultaneously depend on ionic strength, ionic composition and pH. However, when the ionic strength was high, the effects of the other two factors were masked. The zeta potential of the particles was directly related to the size of the TiO agglomerates formed. The samples with an absolute zeta potential value < 10 mV were less stable, with the size of TiO agglomerates in excess of 1500 nm. It can be deduced from this study that TiO ENPs deposited in the landfill may be favored to form agglomerates and ultimately settle from the water percolating through the landfill and thus remain in the landfill.
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http://dx.doi.org/10.1016/j.envpol.2017.01.065DOI Listing
April 2017

Determination of non-gaseous and gaseous mercury fractions in unused fluorescent lamps: a study of different lamp types.

Waste Manag Res 2015 Mar 19;33(3):295-9. Epub 2015 Feb 19.

EMPA, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Thin Films and Photovoltaics, Duebendorf, Switzerland.

Since incandescent light bulbs have been phased out in the European Union from 2009, the use of fluorescent lamps has drastically increased as a reliable, more energy-efficient and cost-effective alternative. State-of-the-art fluorescent lamps are dependent on mercury/mercury alloys, posing a risk for the consumer and the environment, and appropriate waste management is challenging. Consequently analytical methods to determine possible mercury species (non-gaseous/gaseous) in these lamps are of need. Here, a straightforward and wet-chemistry-based analytical strategy for the determination of gaseous and non-gaseous mercury in commercially available fluorescent lamps is presented. It can be adapted in any analytical laboratory, without or with only minimum modifications of already installed equipment. The analytical figures of merit, as well as application of the method to a series of commercially available fluorescent lamps, are presented. Out of 14 analysed and commercially available lamp types, results from this study indicate that only one contains a slightly higher amount of mercury than set by the legislative force. In all new lamps the amount of gaseous mercury is negligible compared with the non-gaseous fraction (88%-99% of total mercury).
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http://dx.doi.org/10.1177/0734242X14567502DOI Listing
March 2015

On interlayer stability and high-cycle simulator performance of diamond-like carbon layers for articulating joint replacements.

Int J Mol Sci 2014 Jun 11;15(6):10527-40. Epub 2014 Jun 11.

Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland.

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and -3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic.
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http://dx.doi.org/10.3390/ijms150610527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4100166PMC
June 2014

A straightforward wet-chemistry method for the determination of solid and gaseous mercury fractions in Backlight Cold Cathode Fluorescence Lamps.

Talanta 2012 Oct 27;100:134-8. Epub 2012 Aug 27.

EMPA, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Analytical Chemistry, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland.

Backlight Cold Cathode Fluorescence Lamps (B-CCFLs) are already applied in many electronic consumer products such as LCD screens, flat screen TVs, and laptop monitors. In consequence, an increase of such products entering the waste streams can be expected in the near future. As a result of the mercury (Hg) employed in such lamps, the development of recycling techniques to create a best practical environmental option for appropriate end-of-life strategies are necessary. For this purpose the knowledge about speciation in terms of solid and gaseous state of Hg in such lamps is inevitable. However, analytical techniques to discriminate solid and gaseous Hg require a special setup, not available in most routine laboratories. Thus a straightforward and cost efficient analytical technique is of need. In this work we describe sample preparation procedures and analysis techniques, which only require equipment already available in most routine laboratories. The volatile fraction is extracted with a KMnO(4) solution utilizing a novel approach, taking the advantage that the B-CCFL glass tubes have a negative pressure. Thus the extraction solution is directly sucked into the tube where the volatile Hg-fraction is immediately extracted. Subsequently, the solid fraction is dissolved via microwave assisted pressure acid digestion after cryo-milling. Analysis for both fractions took place employing a cold vapor atomic absorption system. To prove the new method is fit for purpose, spiking experiments and analysis of reference materials (when available) was performed with recoveries being between 90% and 110%. First results obtained for a stack of lamps from an used LCD-TV display reveal that solid Hg fractions in all lamps show a variation of 20% between samples whereas the gaseous Hg content can vary up to 600%.
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http://dx.doi.org/10.1016/j.talanta.2012.08.005DOI Listing
October 2012

Real-world emission factors for antimony and other brake wear related trace elements: size-segregated values for light and heavy duty vehicles.

Environ Sci Technol 2009 Nov;43(21):8072-8

Empa, Swiss Federal Laboratories for Materials Testing and Research, CH-8600 Duebendorf, Switzerland.

Hourly trace element measurements were performed in an urban street canyon and next to an interurban freeway in Switzerland during more than one month each, deploying a rotating drum impactor (RDI) and subsequent sample analysis by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). Antimony and other brake wear associated elements were detected in three particle size ranges (2.5-10, 1-2.5, and 0.1-1 microm). The hourly measurements revealed that the effect of resuspended road dust has to be taken into account for the calculation of vehicle emission factors. Individual values for light and heavy duty vehicles were obtained for stop-and-go traffic in the urban street canyon. Mass based brake wear emissions were predominantly found in the coarse particle fraction. For antimony, determined emission factors were 11 +/- 7 and 86 +/- 42 microg km(-1) vehicle(-1) for light and heavy duty vehicles, respectively. Antimony emissions along the interurban freeway with free-flowing traffic were significantly lower. Relative patterns for brake wear related elements were very similar for both considered locations. Beside vehicle type specific brake wear emissions, road dust resuspension was found to be a dominant contributor of antimony in the street canyon.
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http://dx.doi.org/10.1021/es9006096DOI Listing
November 2009