Effects of Substitution and Substrate Strain on the Structure and Properties of Orthorhombic Eu1-xYxMnO3 (0 ≤ x ≤ 0.5) Thin Films.

The effects on the structure and magnetic properties of Eu1-xYxMnO3 (0.0 ≤ x ≤ 0.5) thin films due to lattice strain were investigated and compared with those obtained in equivalent composition ceramics. The films were deposited by spin-coating chemical solution onto Pt\TiO2\SiO2\Si (100) standard substrates. X-ray diffraction and Raman spectroscopy measurements revealed that all films crystallize in orthorhombic structure with space group Pnma, observing an added contraction of the unit cell with increasing Y-substitution ou Eu, corresponding to a broadening of the Mn-O1-Mn angle and a gradual decrease in magnetic order response.

An Electrochemical Immunosensor Based on Carboxylated Graphene/SPCE for IgG-SARS-CoV-2 Nucleocapsid Determination.

The COVID-19 pandemic has emphasized the importance and urgent need for rapid and accurate diagnostic tests for detecting and screening this infection. Our proposal was to develop a biosensor based on an ELISA immunoassay for monitoring antibodies against SARS-CoV-2 in human serum samples. The nucleocapsid protein (N protein) from SARS-CoV-2 was employed as a specific receptor for the detection of SARS-CoV-2 nucleocapsid immunoglobulin G. N protein was immobilized on the surface of a screen-printed carbon electrode (SPCE) modified with carboxylated graphene (CG). The percentage of IgG-SARS-CoV-2 nucleocapsid present was quantified using a secondary antibody labeled with horseradish peroxidase (HRP) (anti-IgG-HRP) catalyzed using 3,3',5,5'-tetramethylbenzidine (TMB) mediator by chronoamperometry. A linear response was obtained in the range of 1:1000-1:200 v/v in phosphate buffer solution (PBS), and the detection limit calculated was 1:4947 v/v. The chronoamperometric method showed electrical signals directly proportional to antibody concentrations due to antigen-antibody (Ag-Ab) specific and stable binding reaction.

Molecularly Imprinted Membrane Produced by Electrospinning for ß-Caryophyllene Extraction.

Molecularly imprinted membrane of ß-caryophyllene (MIM-ßCP) was fabricated incorporating ß-caryophyllene molecularly imprinted polymer nanoparticles (ßCP-NP) into polycaprolactone (PCL) fibers via electrospinning. The ßCP-NP were synthesized by precipitation polymerization using the ßCP as a template molecule and acrylic acid as a functional monomer in the proportion of 1:4 mol, respectively. Atomic force microscopy images and X-ray diffraction confirmed the nanoparticles' incorporation into MIM-ßCP. MIM-ßCP functionalization was evaluated by gas chromatography. The binding capacity was 1.80 ± 0.05 µmol/cm2, and the selectivity test was performed with a mixing solution of ßCP and caryophyllene oxide, as an analog compound, that extracted 77% of the ßCP in 5 min. The electrospun MIM-ßCP can be used to detect and extract the ßCP, applications in the molecular sieve, and biosensor production and may also contribute as an initial methodology to enhance versatile applications in the future, such as in the treatment of skin diseases, filters for extraction, and detection of ßCP to prevent counterfeiting of commercial products, and smart clothing with insect-repellent properties.

Effect of the Deposition Time on the Structural, 3D Vertical Growth, and Electrical Conductivity Properties of Electrodeposited Anatase-Rutile Nanostructured Thin Films.

TiO2 time-dependent electrodeposited thin films were synthesized using an electrophoretic apparatus. The XRD analysis revealed that the films could exhibit a crystalline structure composed of ~81% anatase and ~6% rutile after 10 s of deposition, with crystallite size of 15 nm. AFM 3D maps showed that the surfaces obtained between 2 and 10 s of deposition exhibit strong topographical irregularities with long-range and short-range correlations being observed in different surface regions, a trend also observed by the Minkowski functionals. The height-based ISO, as well as specific surface microtexture parameters, showed an overall decrease from 2 to 10 s of deposition, showing a subtle decrease in the vertical growth of the films. The surfaces were also mapped to have low spatial dominant frequencies, which is associated with the similar roughness profile of the films, despite the overall difference in vertical growth observed. The electrical conductivity measurements showed that despite the decrease in topographical roughness, the films acquired a thickness capable of making them increasingly insulating from 2 to 10 s of deposition. Thus, our results prove that the deposition time used during the electrophoretic experiment consistently affects the films' structure, morphology, and electrical conductivity.

Electrochemical immunosensor for detection of Plasmodium vivax lactate dehydrogenase.

BACKGROUND: Malaria is a disease that affects many tropical and subtropical countries, including Brazil. The use of tests for malaria detection is one of the fundamental strategies recommended by the World Health Organization for the control and eradication of the disease. The lack of diagnostic tests leads to an increase in transmission and non-reporting cases. OBJECTIVES: This work described an electrochemical immunosensor for detecting Plasmodium vivax lactate dehydrogenase antigen (Ag-PvLDH). METHODS: The device has developed by immobilising egg yolk IgY antibodies (Ab-PvLDH) on a gold electrode surface using cysteamine as linker. The immunosensor fabrication was followed by differential pulse voltammetry, and contact angle measurements were performed to characterise the modified gold electrode surface. FINDINGS: The results for Ag-PvLDH determination exhibit a linear response at 10-50 µg mL-1 concentration range, with a limit of detection of 455 ng mL-1. The excellent selectivity of the device was confirmed. MAIN CONCLUSIONS: The developed immunosensor showed a good performance, therefore, it can be considered an alternative test to detect malaria caused by P. vivax.

Rietveld Refinement, Morphology, and Optical and Photoluminescence Properties of a ß-Ag1.94Cu0.06MoO4 Solid Solution.

Corner-truncated cubic ß-Ag1.94Cu0.06MoO4 microcrystals were synthesized using the hydrothermal method. These were investigated by X-ray diffraction, confirming obtention of the spinel structure Fd3̅m. Through Raman spectroscopy are confirmed all modes for the point group of Oh7. The Egap shows a decrease of the band gap from 3.20 to 3.07 eV, with reduction of the conduction band occurring from -0.20 eV (ß-Ag2MoO4) to -0.13 eV (ß-Ag1.94Cu0.06MoO4), suggesting a p-type behavior for the Cu2+ ion. The field-emission scanning electron microscopy images confirm the morphological changes for ß-Ag2MoO4, where potato-like microcrystals were found. Meanwhile, corner-truncated cubic microcrystals for ß-Ag1.94Cu0.06MoO4. The photoluminescence (PL) spectrum confirms the increase in the PL emission for ß-Ag1.94Cu0.06MoO4, with suppression of the deep defects occurring in the structure caused by oxygen and silver atoms. In contrast, the green region is intensified because of distortions of the Ag-O and Mo-O bonds. Therefore, the ß-Ag1.94Cu0.06MoO4 solid solution has PL emission with CCT (4510 K) and CIE coordinates (x = 0.372 and y = 0.433), which could be interesting properties for applications as light-emitting diodes.

Electrochemical immunosensor for detection of Plasmodium vivax lactate dehydrogenase

BACKGROUND Malaria is a disease that affects many tropical and subtropical countries, including Brazil. The use of tests for malaria detection is one of the fundamental strategies recommended by the World Health Organization for the control and eradication of the disease. The lack of diagnostic tests leads to an increase in transmission and non-reporting cases. OBJECTIVES This work described an electrochemical immunosensor for detecting Plasmodium vivax lactate dehydrogenase antigen (Ag-PvLDH). METHODS The device has developed by immobilising egg yolk IgY antibodies (Ab-PvLDH) on a gold electrode surface using cysteamine as linker. The immunosensor fabrication was followed by differential pulse voltammetry, and contact angle measurements were performed to characterise the modified gold electrode surface. FINDINGS The results for Ag-PvLDH determination exhibit a linear response at 10-50 µg mL-1 concentration range, with a limit of detection of 455 ng mL-1. The excellent selectivity of the device was confirmed. MAIN CONCLUSIONS The developed immunosensor showed a good performance, therefore, it can be considered an alternative test to detect malaria caused by P. vivax.

Highly sensitive electrochemical immunosensor using a protein-polyvinylidene fluoride nanocomposite for human thyroglobulin.

The highly sensitive detection of serum thyroglobulin (Tg) is essential in the post-treatment follow-up of patients with differentiated thyroid cancer undergoing total or partial thyroidectomy and radioactive iodine ablation and requires sensitive, accurate and stable methods. This work proposes an electrochemical immunosensor for the detection of serum Tg antigen, making use of innovative nanocomposites including polyvinylidene fluoride (PVDF) microparticles coated with streptavidin (MP) and gold nanoparticles (AuNPs). The functionalized polymer matrices were characterized by UV-Vis, FTIR, XPS, SEM, dynamic light scattering, and free surface energy. Immobilization of biotin-labeled anti-thyroglobulin monoclonal antibodies was achieved by binding these to the polymer nanocomposite via streptavidin proteins. The analytical response was measured in quintuplicate and had a linear profile from 2.0 to 10.0 ng/mL Tg, with r2 of 0.985. The limits of detection and quantification were excellent, equal to 0.015 and 0.047 ng/mL, respectively. In addition, the recovery factor was equal to 95.4% (1.0 ng/mL Tg). Overall, the innovative polymer-based nanocomposite used herein enabled the production of an electrochemical-based immunosensor with excellent sensitivity, selectivity, and reproducibility. It evidenced the remarkable potential of determining low levels of Tg in in vitro assays, thereby suggesting that it may be considered for the analyzes of serum patients.

Nanoscale morphology and fractal analysis of TiO2 coatings on ITO substrate by electrodeposition.

In this paper, we introduced an advanced discussion of the 3D morphology of TiO2 coatings deposited on ITO substrate by electrodeposition under different deposition times. Atomic force microscopy was applied for obtaining topographic images of the samples. The images were processed using the MountainsMap 8.0 commercial software according to ISO 25178-2:2012. Moreover, fractal theory was applied to study the surface microtexture of coatings. The morphology was affected by the deposition time, where the grain size decreased with the increase of the time, making film's surfaces smoother. In addition, the surface roughness exhibited a random behaviour, but does not presented significant difference between samples. The fractal dimension showed similar values for all coatings. In contrast, surface texture isotropy also exhibited random behaviour. However, advanced fractal parameters revealed that when the deposition time increased, the coatings microtexture has become uniform and less porous. Furthermore, all coatings presented high topographic uniformity, regardless of deposition time. These results revealed that the morphology and microtexture of TiO2 -based coatings can be controlled by the deposition time. LAY DESCRIPTION: An advanced characterization on the micromorphology of 3D morphology, using AFM images, of Titanium dioxide (TiO2 ) coatings deposited on ITO substrate by electrodeposition under different deposition times. TiO2 is one of the most studied semiconductors to make photovoltaic devices. The versatility of this semiconductor is associated with low toxicity, high photochemical stability, abundance, and the facility to obtain by conventional synthesis routes. The obtention of a homogeneous and stable layer in the semiconductor TiO2 film deposition is a crucial stage in the assembly of sensitized photovoltaic devices. Atomic Force Microscopy (AFM) is a technique which can magnify up to a billion times and it uses a tip or probe which touches the sample surface point by point. The tip deflection is interpreted as the surface topography by the software, producing 2D or 3D images that generate several tribological parameters such as roughness in respect to a scanned area, has been a technique widely reported in the morphological characterization, determination of thickness, roughness, and particle size in thin films. Therefore, in this paper, the morphology was studied by atomic force microscopy using MountainsMap commercial software. The main goal was to study the influence of the deposition time on the morphology and microtexture of the material. New parameters such as surface entropy, fractal succolarity and fractal lacunarity were obtained for studying coatings microtexture's complexity.

Structural and Optical Properties of Ca0.9Cu0.01WO4 Solid Solution Synthesized by Sonochemistry Method at Room Temperature.

In this work, we report the room-temperature synthesis of pure calcium tungstate (CaWO4) and copper-doped calcium tungstate solid solution (Ca0.99Cu0.01WO4) by using a sonochemistry method. These materials were structurally characterized by X-ray diffraction (XRD) and Raman spectroscopy. The obtained XRD patterns were submitted to a Rietveld refinement showing, in both materials, a tetragonal phase with space group and point group of I41/a and C4h6, respectively. Microscopy images of both materials, obtained by field emission scanning electron microscopy, showed spherical agglomerated structures composed by spherical nanoparticles, while calcium and tungstate elements were identified by energy-dispersive X-ray spectroscopy for pure calcium tungstate and copper, calcium, and tungstate for Ca0.99Cu0.01WO4 solid solution. The decrease of optical band gap (Egap) from 4.0 eV (CaWO4) to 3.45 eV (Ca0.99Cu0.01WO4) confirmed the substitution of calcium atoms for copper atoms in the clusters [CaO8]. Maximum photoluminescence (PL) emission was shifted from 522 nm in the pure CaWO4 to 475 nm in the Ca0.99Cu0.01WO4 solid solution. Consequently, there was an increase of PL emissions intensity in the blue and green regions of the visible spectrum, due to electronic transitions between the orbitals O 2p, Cu 3d, and W 5d.

Antimicrobial properties of α-Ag2WO4 rod-like microcrystals synthesized by sonochemistry and sonochemistry followed by hydrothermal conventional method.

In this study we report the synthesis of silver tungstate microcrystals (α-Ag2WO4) by sonochemistry method (SC) at 65 °C and sonochemistry followed by conventional hydrothermal (SC + HC) for 1, 6 and 12 h, at 140 °C. The structural characterization by XRD confirms the alpha phase of the orthorhombic structure and the space group Pn2n, for all synthesized microcrystals. All the actives modes identified at the Raman spectroscopy were characteristic of alpha phase. The optical band gap by UV-Vis spectroscopy using the diffuse reflectance were 2.98, 3.0, 2.99 and 2.96 eV, for the microcrystals SC, SC + HC-1 h, SC + HC-6 h and SC + HC-12 h, respectively. FE-SEM images show the rod-like microcrystals, however, exhibiting the plane surface (1 0 1) only for the synthesized microcrystals with the assistance of the hydrothermal method (SC + HC-1 h, SC + HC- 6 h and SC + HC-12 h). The antimicrobial potential was confirmed for all α-Ag2WO4 microcrystals synthesized. However, the SC + HC-12 h microcrystals were more susceptible in the bacterial and fungal inhibition, with MIC values for microorganisms C. albicans, T. rubrum, MRSA e EHEC, 0.2-0.5, 4-9, 250 and 31.25 µg mL-1, respectively.

Novel electrochemical sensor based on molecularly imprinted polymer for selective recognition of sesquiterpene ß-caryophyllene.

Molecularly imprinted polymers provide an excellent platform for the modification of selective electrodes for sensing applications. Herein, we present a novel modified carbon paste electrode (CPE) with a selective molecularly imprinted polymer (MIP) for recognition of sesquiterpene ß-caryophyllene, constituted of important plants oil-resins and extracts. The non-covalent MIP was synthesized using AA, EGDMA, and AIBN as a functional monomer, cross-linker and initiator agent, respectively. Structural and chemical characterization of the synthesized MIP was conducted through scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was possible to verify the functional features of the synthesized MIP related to the extraction process of the template molecule. The CPE modified with MIP for sesquiterpene ß-caryophyllene recognition was characterized by electrochemical techniques as cyclic voltammetry (CV) and square wave voltammetry (SWV). The highest selective recognition electrode enables to detect concentrations in the range between 1.5 × 10-7 and 7.5 × 10-7 M, showing great potential for applications in monitoring content of sesquiterpene ß-caryophyllene in technological processes and for predicting the quality of extracts, oils, and resins of plants.