Automated mechanical exfoliation technique: a spin pumping study in YIG/TMD heterostructures.

Spintronics devices rely on the generation and manipulation of spin currents. Two-dimensional transition-metal dichalcogenides (TMDs) are among the most promising materials for a spin current generation due to a lack of inversion symmetry at the interface with the magnetic material. Here, we report on the fabrication of Yttrium Iron Garnet(YIG)/TMD heterostructures by means of a crude and fast method. While the magnetic insulator single-crystalline YIG thin films were grown by magnetron sputtering, the TMDs, namely MoS2 and MoSe2, were directly deposited onto YIG films using an automated mechanical abrasion method. Despite the brute force aspect of the method, it produces high-quality interfaces, which are suitable for spintronic device applications. The spin current density and the effective spin mixing conductance were measured by ferromagnetic resonance, whose values found are among the highest reported in the literature. Our method can be scaled to produce ferromagnetic materials/TMD heterostructures on a large scale, further advancing their potential for practical applications.

Development of an electrochemical sensor based on ternary oxide SiO2/Al2O3/SnO2 modified with carbon black for direct determination of clothianidin in environmental and food samples.

This study presents the development of an electrochemical sensor, denoted as GCE/CB/SiAlSn, based on the modification of a glassy carbon electrode surface with the ternary oxide SiO2/Al2O3/SnO2 associated with carbon black, for direct determination of the neonicotinoid pesticide clothianidin in different matrices, such as environmental and food samples. Morphological characterization by the scanning electron microscopy technique, electroanalytical analyses using the cyclic voltammetry technique and differential pulse voltammetry are presented which demonstrated that the developed electrochemical platform presents high sensitivity in the electroanalytical clothianidin determination. The linear range studied was from 2.99 × 10-7 to 6.04 × 10-5 mol L-1, with an LOD of 2.47 nmol L-1. This high sensitivity was explained using the synergistic relationship between carbon black and ternary oxide that maximized the electroactive surface area of the GCE/CB/SiAlSn sensor. Interferent studies were performed that showed high selectivity of the sensor to the pesticide in the presence of Ca2+, K+, Na+, and Mg2+ and carbendazim, glyphosate, imidacloprid and thiamethoxam pesticides. The sensor was applied to real samples of tap water and apple juice obtaining recoveries from 91.0% to 103.0%.

Evaluation of microplastic contamination by metals in a controlled environment: A risk to be considered.

The metal contamination and the degradation of polyethylene terephthalate (PET) due to human activities have contributed to the worsening of environmental problems in aquatic systems. Therefore, the study aimed to evaluate PET microplastic adsorption levels when exposed to high amounts of Ni, Cu and Co. The PET microplastic was characterized by scanning electron microscopy, Brunner-Emmet-Teller, porosimetry system, Barrett-Joyner-Halenda and Fourier transform infrared spectroscopy with attenuated total reflectance for evaluation of surface morphology, surface area, porosity, pore size and functional groups, respectively. The results showed that the surface area, the presence of macro and mesopores, and the functional groups influence the adsorption of metals on the surface of PET microplastic. The adsorption isotherms confirmed the presence of mesoporosity and macroporosity on the PET microplastic surface. The Freundlich and Langmuir models were used to study the adsorption capacity. The kinetics of adsorptions were interpreted using pseudo-first order and pseudo-second order models. The results indicated that the Langmuir isotherm and the pseudo-second order adequately described the adsorption of metals by the PET microplastic. The removal rates by the PET microplastic varied from 8 to 34% for Ni, 5 to 40% for Cu and 7 to 27% for Co after a period of 5 days. Furthermore, the adsorption was predominantly chemical and extremely fast, indicating that the presence of microplastics in the environment can lead to a rapid metal accumulation which elevates the hazards potential of microplastic in living beings.

The Effects of Titanium Dioxide Nanoparticles on Osteoblasts Mineralization: A Comparison between 2D and 3D Cell Culture Models.

Although several studies assess the biological effects of micro and titanium dioxide nanoparticles (TiO2 NPs), the literature shows controversial results regarding their effect on bone cell behavior. Studies on the effects of nanoparticles on mammalian cells on two-dimensional (2D) cell cultures display several disadvantages, such as changes in cell morphology, function, and metabolism and fewer cell-cell contacts. This highlights the need to explore the effects of TiO2 NPs in more complex 3D environments, to better mimic the bone microenvironment. This study aims to compare the differentiation and mineralized matrix production of human osteoblasts SAOS-2 in a monolayer or 3D models after exposure to different concentrations of TiO2 NPs. Nanoparticles were characterized, and their internalization and effects on the SAOS-2 monolayer and 3D spheroid cells were evaluated with morphological analysis. The mineralization of human osteoblasts upon exposure to TiO2 NPs was evaluated by alizarin red staining, demonstrating a dose-dependent increase in mineralized matrix in human primary osteoblasts and SAOS-2 both in the monolayer and 3D models. Furthermore, our results reveal that, after high exposure to TiO2 NPs, the dose-dependent increase in the bone mineralized matrix in the 3D cells model is higher than in the 2D culture, showing a promising model to test the effect on bone osteointegration.

Migration of silver nanoparticles from plastic materials, with antimicrobial action, destined for food contact.

Five materials with antimicrobial function, by adding silver, were investigated to evaluate total silver concentration in the polymers and migration of silver nanoparticles from the materials in contact with food. The migration test was carried out by contacting plastic material with food simulant. Migration concentrations and average silver particle sizes were determined by mass spectrometry with inductively coupled plasma, performed in single particle mode (spICP-MS). Additionally, silver particles size and shape were characterized by scanning electron microscopy (SEM) with chemical identification by energy-dispersive X-ray spectroscopy (EDS). Most of samples showed detectable total silver concentrations and all samples showed migration of silver nanoparticles, with concentrations found between 0.00433 and 1.35 ng kg-1. Indeed, the migration study indicated the presence of silver nanoparticles in all food simulants, with sizes bellow 95 nm. The average particle size determined for acetic acid was greater than that observed in the other simulants. In the images obtained by SEM/EDS also confirmed the presence of spherical silver nanoparticles, between 17 and 80 nm. The findings reported herein will aid the health area concerning of human health risk assessments, aiming at regulating this type of material from a food safety point of view.

Wurtzite Gallium Phosphide via Chemical Beam Epitaxy: Impurity-Related Luminescence vs Growth Conditions.

The metastable wurtzite crystal phase in gallium phosphide (WZ GaP) is a relatively new structure with little available information about its emission properties compared to the most stable zinc-blend phase. Here, the effect of growth conditions of WZ GaP nano- and microstructures obtained via chemical beam epitaxy on the optical properties was studied using power- and temperature-dependent photoluminescence (PL). We showed that the PL spectra are dominated by two strong broad emission bands at 1.68 and 1.88 eV and two relatively narrow peaks at 2.04 and 2.09 eV. The broad emissions are associated with the presence of carbon and a small number of extended crystal defects, respectively. For the sharp emissions, two main radiative recombination channels were observed with ionization energies estimated in the range of 50-80 meV and lower than 10 meV. No variation of the low-temperature PL spectra was observed for samples grown at different P precursor flows, while increasing Ga content enhanced the dominant broad emission at around 1.68 eV, suggesting that the group III organometallic precursor is the main source of impurities. Finally, Be-doped samples were grown, and their characteristic optical emission at 2.03 eV was identified. These results contribute to the understanding of impurity-related luminescence in hexagonal GaP, being useful for further crystal growth optimization required for the fabrication of optoelectronic devices.

An electrochemical sensor-based carbon black associated with a modified mixed oxide (SiO2/TiO2/Sb2O5) for direct determination of thiamethoxam in raw honey and water samples.

The study aimed to develop an electrochemical sensor based on glassy carbon, mixed oxide (SiO2/TiO2/Sb2O5), and carbon black. The material was synthesized, characterized, and used to determine thiamethoxam in raw honey and water. The morphologic structure and electrochemical performance of the sensor was characterized by scanning electron microscopy and cyclic voltammetry. Differential pulse voltammetry with a concentration of 0.1 mol L-1 of Britton-Robinson buffer at pH 7.0 allowed the generation of a method to determine thiamethoxam in a linear range of 0.25 to 100.5 µmol L-1 and with a limit of detection of 0.012 µmol L-1. The system efficiently quantified traces of thiamethoxam in raw honey and tap water samples. The modified sensor did not present interferences of K+, Na+, Ca2+, Mg2+, glyphosate, imidacloprid, and carbendazim. In addition, the device showed good recovery values for thiamethoxam when applied directly to honey and water samples without any treatment, presenting an electrochemical sensor to monitor real-time hazardous substances in environmental and food matrices.

SARS-CoV-2: Ultrastructural Characterization of Morphogenesis in an In Vitro System.

The pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has impacted public health and the world economy and fueled a worldwide race to approve therapeutic and prophylactic agents, but so far there are no specific antiviral drugs. Understanding the biology of the virus is the first step in structuring strategies to combat it, and in this context several studies have been conducted with the aim of understanding the replication mechanism of SARS-CoV-2 in vitro systems. In this work, studies using transmission and scanning electron microscopy and 3D electron microscopy modeling were performed with the goal of characterizing the morphogenesis of SARS-CoV-2 in Vero-E6 cells. Several ultrastructural changes were observed-such as syncytia formation, cytoplasmic membrane projections, lipid droplets accumulation, proliferation of double-membrane vesicles derived from the rough endoplasmic reticulum, and alteration of mitochondria. The entry of the virus into cells occurred through endocytosis. Viral particles were observed attached to the cell membrane and in various cellular compartments, and extrusion of viral progeny took place by exocytosis. These findings allow us to infer that Vero-E6 cells are highly susceptible to SARS-CoV-2 infection as described in the literature and their replication cycle is similar to that described with SARS-CoV and MERS-CoV in vitro models.

Defect activated optical Raman modes in single layer MoSe2.

In the last decade, transition metal dichalcogenides (TMDs) have been intensively synthesized/studied thus linking their morphological aspect to their physical properties, and consequently leading to the understanding of the possible benefits of defects in such materials. Nevertheless, for future applications, quantifying and identifying defects in TMDs is still a milestone to reach in order to better employ these materials in optoelectronic devices. Raman Spectroscopy has been successfully employed in graphene to quantify punctual or line defects. In this paper, we bombarded monolayer MoSe2with He ions and found out the existence of three defect activated Raman bands around 250-300 cm-1. Density functional theory calculations were employed to obtain the electronic and phonon dispersion bands, making it possible to infer that these bands arise from inter-valley Raman double resonance processes. Interestingly, the same punctual defect model, that allows one to predict the defect concentration at which graphene starts to become amorphous, also works for TMDs. Hence, this work opens the door to the macroscopic quantification of defects in TMDs, which is essential for technological applications.

Morphology and morphogenesis of SARS-CoV-2 in Vero-E6 cells.

BACKGROUND: The coronaviruses (CoVs) called the attention of the world for causing outbreaks of severe acute respiratory syndrome (SARS-CoV), in Asia in 2002-03, and respiratory disease in the Middle East (MERS-CoV), in 2012. In December 2019, yet again a new coronavirus (SARS-CoV-2) first identified in Wuhan, China, was associated with a severe respiratory infection, known today as COVID-19. This new virus quickly spread throughout China and 30 additional countries. As result, the World Health Organization (WHO) elevated the status of the COVID-19 outbreak from emergency of international concern to pandemic on March 11, 2020. The impact of COVID-19 on public health and economy fueled a worldwide race to approve therapeutic and prophylactic agents, but so far, there are no specific antiviral drugs or vaccines available. In current scenario, the development of in vitro systems for viral mass production and for testing antiviral and vaccine candidates proves to be an urgent matter. OBJECTIVE: The objective of this paper is study the biology of SARS-CoV-2 in Vero-E6 cells at the ultrastructural level. METHODS: In this study, we documented, by transmission electron microscopy and real-time reverse transcription polymerase chain reaction (RT-PCR), the infection of Vero-E6 cells with SARS-CoV-2 samples isolated from Brazilian patients. FINDINGS: The infected cells presented cytopathic effects and SARS-CoV-2 particles were observed attached to the cell surface and inside cytoplasmic vesicles. The entry of the virus into cells occurred through the endocytic pathway or by fusion of the viral envelope with the cell membrane. Assembled nucleocapsids were verified inside rough endoplasmic reticulum cisterns (RER). Viral maturation seemed to occur by budding of viral particles from the RER into smooth membrane vesicles. MAIN CONCLUSIONS: Therefore, the susceptibility of Vero-E6 cells to SARS-CoV-2 infection and the viral pathway inside the cells were demonstrated by ultrastructural analysis.

Morphology and morphogenesis of SARS-CoV-2 in Vero-E6 cells

BACKGROUND The coronaviruses (CoVs) called the attention of the world for causing outbreaks of severe acute respiratory syndrome (SARS-CoV), in Asia in 2002-03, and respiratory disease in the Middle East (MERS-CoV), in 2012. In December 2019, yet again a new coronavirus (SARS-CoV-2) first identified in Wuhan, China, was associated with a severe respiratory infection, known today as COVID-19. This new virus quickly spread throughout China and 30 additional countries. As result, the World Health Organization (WHO) elevated the status of the COVID-19 outbreak from emergency of international concern to pandemic on March 11, 2020. The impact of COVID-19 on public health and economy fueled a worldwide race to approve therapeutic and prophylactic agents, but so far, there are no specific antiviral drugs or vaccines available. In current scenario, the development of in vitro systems for viral mass production and for testing antiviral and vaccine candidates proves to be an urgent matter. OBJECTIVE The objective of this paper is study the biology of SARS-CoV-2 in Vero-E6 cells at the ultrastructural level. METHODS In this study, we documented, by transmission electron microscopy and real-time reverse transcription polymerase chain reaction (RT-PCR), the infection of Vero-E6 cells with SARS-CoV-2 samples isolated from Brazilian patients. FINDINGS The infected cells presented cytopathic effects and SARS-CoV-2 particles were observed attached to the cell surface and inside cytoplasmic vesicles. The entry of the virus into cells occurred through the endocytic pathway or by fusion of the viral envelope with the cell membrane. Assembled nucleocapsids were verified inside rough endoplasmic reticulum cisterns (RER). Viral maturation seemed to occur by budding of viral particles from the RER into smooth membrane vesicles. MAIN CONCLUSIONS Therefore, the susceptibility of Vero-E6 cells to SARS-CoV-2 infection and the viral pathway inside the cells were demonstrated by ultrastructural analysis.

Unraveling structural and compositional information in 3D FinFET electronic devices.

Non-planar Fin Field Effect Transistors (FinFET) are already present in modern devices. The evolution from the well-established 2D planar technology to the design of 3D nanostructures rose new fabrication processes, but a technique capable of full characterization, particularly their dopant distribution, in a representative (high statistics) way is still lacking. Here we propose a methodology based on Medium Energy Ion Scattering (MEIS) to address this query, allowing structural and compositional quantification of advanced 3D FinFET devices with nanometer spatial resolution. When ions are backscattered, their energy losses unfold the chemistry of the different 3D compounds present in the structure. The FinFET periodicity generates oscillatory features as a function of backscattered ion energy and, in fact, these features allow a complete description of the device dimensions. Additionally, each measurement is performed over more than thousand structures, being highly representative in a statistical meaning. Finally, independent measurements using electron microscopy corroborate the proposed methodology.

Surface-enhanced Raman scattering study of the redox adsorption of p-phenylenediamine on gold or copper surfaces.

The adsorption of the p-phenylenediamine (PPD(+)) radical cation on gold or copper nanoparticle (NP) surfaces was studied through surface-enhanced Raman scattering (SERS) spectroscopy, excited at 1064 nm. The SERS spectra were obtained from gold or copper NPs after exposure to non-oxidized p-phenylenediamine (PPD) aqueous solution, in millimolar concentration. The gold NPs were synthesized as nanoshells involving silica cores (SiO(2)@Au) and the copper NPs were obtained in aqueous medium, undergoing surface oxidation with the formation of Cu(II) oxide nanoshell (Cu@CuO). In the latter, the oxidative adsorption of PPD(+) led to the reduction of the copper oxide, present on NP surface, allowing obtaining the PPD(+) SERS spectrum. The vibrational assignments of the SERS spectra of the adsorbate were performed using the results of Density Functional Theory calculations of the Raman frequencies, which together with the SERS surface selection rules, allowed to infer the adsorption geometry of PPD(+) radical cation on both metallic surfaces. This work stress the investigation of redox processes involved in the molecular adsorption is imperative for the interpretation of the SERS results, which is even more important when copper surfaces are studied.