References of "Martin Lanzoni, Evandro 50031800"
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See detailEffects of Annealing and Light on Co-evaporated Methylammonium Lead Iodide Perovskites using Kelvin Probe Force Microscopy in Ultra-High Vacuum
Gallet, Thibaut UL; Martin Lanzoni, Evandro UL; Redinger, Alex UL

in 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) (2020, February 06)

Careful surface analysis is essential to understand the electronic and ionic behaviors in perovskite absorbers. In this contribution we discuss Kelvin probe force microscopy performed in ultra-high vacuum ... [more ▼]

Careful surface analysis is essential to understand the electronic and ionic behaviors in perovskite absorbers. In this contribution we discuss Kelvin probe force microscopy performed in ultra-high vacuum on as-grown and annealed co-evaporated methylammonium lead iodide perovskite thin films. By comparing the contact potential difference upon annealing and illumination, we find that annealing increases the average workfunction, indicating a change either in doping or in surface composition. Illumination also increases the average workfunction, indicating a p-type absorber, by reducing band bending as the photo-generated carriers screen the surface states. The effect of light shows a two-step process, with a first fast trend, linked to the surface photovoltage and a second slower trend indicating a possible redistribution of mobile charges. [less ▲]

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See detailSurface characterization of epitaxial Cu-rich CuInSe2 absorbers
Martin Lanzoni, Evandro UL; Spindler, Conrad UL; Ramirez Sanchez, Omar UL et al

in IEEE Photovoltaic Specialists Conference. Conference Record (2019, July)

We investigated the electrical properties of epitaxial Cu-rich CuInSe 2 by Kelvin probe force microscopy (KPFM) under ambient and ultra-high vacuum conditions. We first measured the sample under ambient ... [more ▼]

We investigated the electrical properties of epitaxial Cu-rich CuInSe 2 by Kelvin probe force microscopy (KPFM) under ambient and ultra-high vacuum conditions. We first measured the sample under ambient conditions before and after potassium cyanide (KCN) etching. In both cases, we do not see any substantial contrast in the surface potential data; furthermore, after the KCN etching we observed outgrowths with a height around 2nm over the sample surface. On the other hand, the KPFM measurements under ultra-high vacuum conditions show a work function dependence according to the surface orientation of the Cu-rich CuInSe 2 crystal. Our results show the possibility to increase the efficiency of epitaxial Cu-rich CuInSe 2 by growing the materials in the appropriated surface orientation where the variations in work function are reduced. [less ▲]

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See detailBanana starch nanocomposite with cellulose nanofibers isolated from banana peel by enzymatic treatment: In vitro cytotoxicity assessment
Tibolla, H.; Pelissari, F. M.; Martins, J. T. et al

in Carbohydrate Polymers (2019), 207

The potential use of cellulose nanofibers (CNFs) as a reinforcing agent in banana starch-based nanocomposite films was investigated. CNFs were isolated from banana peel (Musa paradisiaca) by enzymatic ... [more ▼]

The potential use of cellulose nanofibers (CNFs) as a reinforcing agent in banana starch-based nanocomposite films was investigated. CNFs were isolated from banana peel (Musa paradisiaca) by enzymatic hydrolysis. Banana starch-based nanocomposite films were prepared with CNFs using the casting method. CNFs effect on cell viability and on nanocomposite films properties’ was investigated. The cytotoxicity of CNFs was assessed on Caco-2 cell line. CNFs were not cytotoxic at 50–2000 μg/mL. However, CNFs above 2000 μg/mL significantly decreased cell viability. Topography analysis showed that the incorporation of CNFs modified the film structure. The nanocomposites exhibited a complex structure due to strong interactions between CNFs and starch matrix, promoting a remarkable improvement on mechanical and water barrier properties, opacity and UV light barrier compared to the control film. CNFs can offer a great potential as reinforcing material for starch-based nanocomposite films, producing a value-added food packaging from a waste material. [less ▲]

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See detailUnraveling the Role of Sn Segregation in the Electronic Transport of Polycrystalline Hematite: Raising the Electronic Conductivity by Lowering the Grain-Boundary Blocking Effect
Soares, Mario R. S.; Costa, Carlos A. R.; Martin Lanzoni, Evandro UL et al

in Advanced Electronic Materials (2019), 0(0), 1900065

This paper describes the role of SnO2 in the electronic transport of polycrystalline hematite (α-Fe2O3). The proper sintering process allows for freezing of a state of electronic defects, in which the ... [more ▼]

This paper describes the role of SnO2 in the electronic transport of polycrystalline hematite (α-Fe2O3). The proper sintering process allows for freezing of a state of electronic defects, in which the electrical properties of hematite are controlled by the grain boundary and Sn segregation. Impedance spectroscopy and dc conductivity measurements show that current flows through preferential pathways associated with Sn segregation that occurs at the grain boundary, leading to a decrease in grain-boundary resistance. Atomic force microscopy and electric force microscopy measurements confirm the results of the impedance analysis. The identification of preferential grain boundaries for electrical conductivity may have a direct influence on the light-induced water-splitting performance of the hematite photoanode. [less ▲]

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See detailWearable binary cooperative polypyrrole nanofilms for chemical mapping on skin
Morais, Vitória Brito De; Corrêa, Cátia Crispilho; Martin Lanzoni, Evandro UL et al

in Journal of Materials Chemistry A (2019)

Wearable polypyrrole nanofilm arrays have been developed to extend the natural capabilities of the skin. Chemical mapping of acids in different states of matter were accurately detected on skin using ... [more ▼]

Wearable polypyrrole nanofilm arrays have been developed to extend the natural capabilities of the skin. Chemical mapping of acids in different states of matter were accurately detected on skin using binary cooperative polypyrrole structures on cellulose-based substrates. [less ▲]

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See detailCovalent functionalization of graphene oxide with D-mannose: evaluating the hemolytic effect and protein corona formation
Sousa, Marcelo De; Martins, Carlos H. Z.; Franqui, Lidiane S. et al

in Journal of Materials Chemistry B (2018), 6(18), 2803--2812

In this work, graphene oxide (GO) was covalently functionalized with D-mannose (man-GO) using mannosylated ethylenediamine. XPS (C1s and N1s) confirmed the functionalization of GO through the binding ... [more ▼]

In this work, graphene oxide (GO) was covalently functionalized with D-mannose (man-GO) using mannosylated ethylenediamine. XPS (C1s and N1s) confirmed the functionalization of GO through the binding energies at 288.2 eV and 399.8 eV, respectively, which are attributed to the amide bond. ATR-FTIR spectroscopy showed an increase in the amine bond intensity, at 1625 cm−1 (stretching CO), after the functionalization step. Furthermore, the man-GO toxicity to human red blood cells (hemolysis) and its nanobiointeractions with human plasma proteins (hard corona formation) were evaluated. The mannosylation of GO drastically reduced its toxicity to red blood cells. SDS-PAGE analysis showed that the mannosylation process of GO also drastically reduced the amount of the proteins in the hard corona. Additionally, proteomics analysis by LC–MS/MS revealed 109 proteins in the composition of the man-GO hard corona. Finally, this work contributes to future biomedical applications of graphene-based materials functionalized with active biomolecules. [less ▲]

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See detailPredicting Ligand-Free Cell Attachment on Next-Generation Cellulose–Chitosan Hydrogels
Johns, Marcus A.; Bae, Yongho; Guimarães, Francisco E. G. et al

in ACS Omega (2018), 3(1), 937--945

There is a growing appreciation that engineered biointerfaces can regulate cell behaviors, or functions. Most systems aim to mimic the cell-friendly extracellular matrix environment and incorporate ... [more ▼]

There is a growing appreciation that engineered biointerfaces can regulate cell behaviors, or functions. Most systems aim to mimic the cell-friendly extracellular matrix environment and incorporate protein ligands; however, the understanding of how a ligand-free system can achieve this is limited. Cell scaffold materials comprised of interfused chitosan–cellulose hydrogels promote cell attachment in ligand-free systems, and we demonstrate the role of cellulose molecular weight, MW, and chitosan content and MW in controlling material properties and thus regulating cell attachment. Semi-interpenetrating network (SIPN) gels, generated from cellulose/ionic liquid/cosolvent solutions, using chitosan solutions as phase inversion solvents, were stable and obviated the need for chemical coupling. Interface properties, including surface zeta-potential, dielectric constant, surface roughness, and shear modulus, were modified by varying the chitosan degree of polymerization and solution concentration, as well as the source of cellulose, creating a family of cellulose–chitosan SIPN materials. These features, in turn, affect cell attachment onto the hydrogels and the utility of this ligand-free approach is extended by forecasting cell attachment using regression modeling to isolate the effects of individual parameters in an initially complex system. We demonstrate that increasing the charge density, and/or shear modulus, of the hydrogel results in increased cell attachment. [less ▲]

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See detailSeparating the influence of electric charges in magnetic force microscopy images of inhomogeneous metal samples
Arenas, Mónica P.; Martin Lanzoni, Evandro UL; Pacheco, Clara J. et al

in Journal of Magnetism and Magnetic Materials (2018), 446

In this study, we investigate artifacts arising from electric charges present in magnetic force microscopy images. Therefore, we use two austenitic steel samples with different microstructural conditions ... [more ▼]

In this study, we investigate artifacts arising from electric charges present in magnetic force microscopy images. Therefore, we use two austenitic steel samples with different microstructural conditions. Furthermore, we examine the influence of the surface preparation, like etching, in magnetic force images. Using Kelvin probe force microscopy we can quantify the charges present on the surface. Our results show that electrical charges give rise to a signature in the magnetic force microscopy, which is indistinguishable from a magnetic signal. Our results on two differently aged steel samples demonstrate that the magnetic force microscopy images need to be interpreted with care and must be corrected due to the influence of electrical charges present. We discuss three approaches, how to identify these artifacts – parallel acquisition of magnetic force and electric force images on the same position, sample surface preparation to decrease the presence of charges and inversion of the magnetic polarization in two succeeding measurement. [less ▲]

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See detailModulating cell response on cellulose surfaces; tunable attachment and scaffold mechanics
Courtenay, James C.; Deneke, Christoph; Martin Lanzoni, Evandro UL et al

in Cellulose (2017)

Combining surface chemical modification of cellulose to introduce positively charged trimethylammonium groups by reaction with glycidyltrimethylammonium chloride (GTMAC) allowed for direct attachment of ... [more ▼]

Combining surface chemical modification of cellulose to introduce positively charged trimethylammonium groups by reaction with glycidyltrimethylammonium chloride (GTMAC) allowed for direct attachment of mammalian MG-63 cells, without addition of protein modifiers, or ligands. Very small increases in the surface charge resulted in significant increases in cell attachment: at a degree of substitution (DS) of only 1.4\%, MG-63 cell attachment was \textgreater 90 compared to tissue culture plastic, whereas minimal attachment occurred on unmodified cellulose. Cell attachment plateaued above DS of ca. 1.85 reflecting a similar trend in surface charge, as determined from ζ-potential measurements and capacitance coupling (electric force microscopy). Cellulose film stiffness was modulated by cross linking with glyoxal (0.3–2.6 degree of crosslinking) to produce a range of materials with surface shear moduli from 76 to 448 kPa (measured using atomic force microscopy). Cell morphology on these materials could be regulated by tuning the stiffness of the scaffolds. Thus, we report tailored functionalised biomaterials based on cationic cellulose that can be tuned through surface reaction and glyoxal crosslinkin+g, to influence the attachment and morphology of cells. These scaffolds are the first steps towards materials designed to support cells and to regulate cell morphology on implanted biomaterials using only scaffold and cells, i.e. without added adhesion promoters. [less ▲]

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See detailSurface modified cellulose scaffolds for tissue engineering
Courtenay, James C.; Johns, Marcus A.; Galembeck, Fernando et al

in Cellulose (2016)

We report the ability of cellulose to support cells without the use of matrix ligands on the surface of the material, thus creating a two-component system for tissue engineering of cells and materials ... [more ▼]

We report the ability of cellulose to support cells without the use of matrix ligands on the surface of the material, thus creating a two-component system for tissue engineering of cells and materials. Sheets of bacterial cellulose, grown from a culture medium containing Acetobacter organism were chemically modified with glycidyltrimethylammonium chloride or by oxidation with sodium hypochlorite in the presence of sodium bromide and 2,2,6,6-tetramethylpipiridine 1-oxyl radical to introduce a positive, or negative, charge, respectively. This modification process did not degrade the mechanical properties of the bulk material, but grafting of a positively charged moiety to the cellulose surface (cationic cellulose) increased cell attachment by 70 compared to unmodified cellulose, while negatively charged, oxidised cellulose films (anionic cellulose), showed low levels of cell attachment comparable to those seen for unmodified cellulose. Only a minimal level of cationic surface derivitisation (ca 3 degree of substitution) was required for increased cell attachment and no mediating proteins were required. Cell adhesion studies exhibited the same trends as the attachment studies, while the mean cell area and aspect ratio was highest on the cationic surfaces. Overall, we demonstrated the utility of positively charged bacterial cellulose in tissue engineering in the absence of proteins for cell attachment. [less ▲]

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See detailOvergrowth of wrinkled InGaAs membranes using molecular beam epitaxy
da Silva, S. Filipe Covre; Martin Lanzoni, Evandro UL; Malachias, A. et al

in Journal of Crystal Growth (2015), 425

Partly released InGaAs layers forming a wrinkled network are used as templates for InAs growth. A systematic growth study was carried out, where InAs amounts from 0 ML to 3 ML were deposited on the ... [more ▼]

Partly released InGaAs layers forming a wrinkled network are used as templates for InAs growth. A systematic growth study was carried out, where InAs amounts from 0 ML to 3 ML were deposited on the patterned samples. The material migration during growth is evaluated by distinct microscopy techniques. We find a systematic accumulation of the deposited material on the released, wrinkled areas of the sample, whereas no material accumulation or formation of three-dimensional nanostructures is observed on the unreleased areas of the sample. [less ▲]

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See detailDetermination of High Frequency Dielectric Constant and Surface Potential of Graphene Oxide and Influence of Humidity by KPFM.
Salomão, Francisco Carneiro; Martin Lanzoni, Evandro UL; Costa, Carlos et al

in Langmuir (2015)

We use Kelvin probe force microscopy (KPFM) and capacitance coupling (dC/dz) to study the electrical properties of graphene oxide (GO). We propose using the dC/dz signal to probe the high frequency ... [more ▼]

We use Kelvin probe force microscopy (KPFM) and capacitance coupling (dC/dz) to study the electrical properties of graphene oxide (GO). We propose using the dC/dz signal to probe the high frequency dielectric constant of mono- and few-layer GO. Our measurements suggest that the dynamic dielectric constant of GO is on the order of εGO ? 3.0 ε0, in the high frequency limit, and independent of the number of GO layers. The measurements are performed at a humidity controlled environment (5 of humidity). The effects of increasing humidity on both the dC/dz and KPFM measurements are analyzed. [less ▲]

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See detailAdhesive and Reinforcing Properties of Soluble Cellulose: A Repulpable Adhesive for Wet and Dry Cellulosic Substrates
Ferreira, Elisa UL; Martin Lanzoni, Evandro UL; Costa, Carlos A. R. et al

in ACS Applied Materials Interfaces (2015), 7(33), 18750--18758

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See detailScratch testing for micro- and nanoscale evaluation of tribocharging in DLC films containing silver nanoparticles using AFM and KPFM techniques
Vieira, L.; Lucas, Francis UL; Fisssmer, S. F. et al

in Surface and Coatings Technology (2014), 260

Scratch testing is a fast and effective method for the measurement of critical loads in order to determine the adhesion properties of coatings and their behavior in tribological applications. Kelvin probe ... [more ▼]

Scratch testing is a fast and effective method for the measurement of critical loads in order to determine the adhesion properties of coatings and their behavior in tribological applications. Kelvin probe force microscopy (KPFM) provides a means of monitoring electrostatic charging on the surfaces of materials. In this paper, we describe the use of a combination of scratch testing and KPFM analysis to evaluate the electrostatic effect induced by silver nanoparticles incorporated as clusters in diamond-like carbon (DLC) films, as well as its correlation with the rubbing process. KPFM was used for mapping of the potentials on the surfaces of DLC–Ag films subjected to nanoscale scratching. The procedure was also conducted at the microscale in order to analyze the way in which silver nanoparticles were spread in the track. After scratching, the track was analyzed using backscattered electrons (BSE) and energy dispersive X-ray diffraction (EDX). The BSE images highlighted bright domains of metallic nanoparticles dispersed in the amorphous coating and EDX confirmed the presence of silver nanoparticles in the scratched track. Micro Raman spectroscopy was used to check the DLC signature. The electric potentials of DLC films with and without silver nanoparticles were also analyzed. The results indicated that the incorporation of silver nanoparticles in amorphous materials could offer new option for electrostatic energy storage on the surfaces of materials. [less ▲]

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See detailInAs migration on released, wrinkled InGaAs membranes used as virtual substrate
Silva, S. Filipe Covre Da; Martin Lanzoni, Evandro UL; Barboza, V. De Araujo et al

in Nanotechnology (2014), 25(45), 455603

Partly released, relaxed and wrinkled InGaAs membranes are used as virtual substrates for overgrowth with InAs. Such samples exhibit different lattice parameters for the unreleased epitaxial parts, the ... [more ▼]

Partly released, relaxed and wrinkled InGaAs membranes are used as virtual substrates for overgrowth with InAs. Such samples exhibit different lattice parameters for the unreleased epitaxial parts, the released flat, back-bond areas and the released wrinkled areas. A large InAs migration towards the released membrane is observed with a material accumulation on top of the freestanding wrinkles during overgrowth. A semi-quantitative analysis of the misfit strain shows that the material migrates to the areas of the sample with the lowest misfit strain, which we consider as the areas of the lowest chemical potential of the surface. Material migration is also observed for the edge-supported, freestanding InGaAs membranes found on these samples. Our results show that the released, wrinkled nanomembranes offer a growth template for InAs deposition that fundamentally changes the migration behavior of the deposited material on the growth surface. [less ▲]

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