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ZnO nanocrystals with three different morphologies have been synthesized via a simple sol-gel-based method using Brosimum parinarioides (bitter Amapá) and Parahancornia amapa (sweet Amapá) latex as chelating agents. X-ray diffraction (XRD) and electron diffraction patterns (SAED) patterns showed the ZnO nanocrystals were a pure hexagonal wurtzite phase of ZnO. XRD-based spherical harmonics predictions and HRTEM images depicted that the nanocrystallites constitute pitanga-like (~15.8 nm), teetotum-like (~16.8 nm), and cambuci-like (~22.2 nm) shapes for the samples synthesized using bitter Amapá, sweet Amapá, and bitter/sweet Amapá chelating agent, respectively. The band gap luminescence was observed at ~2.67–2.79 eV along with several structural defect-related, blue emissions at 468–474 nm (VO, VZn, Zni), green emissions positioned at 513.89–515.89 (h-), and orange emission at 600.78 nm (–). The best MB dye removal efficiency (85%) was mainly ascribed to the unique shape and oxygen vacancy defects found in the teetotum-like ZnO nanocrystals. Thus, the bitter Amapá and sweet Amapá latex are effective chelating agents for synthesizing distinctive-shaped ZnO nanocrystals with highly defective and remarkable photocatalytic activity.

This study introduces modified carbon paste electrodes with carbon nitride nanosheets (CNNS) and outlines their application for the determination of hydroxychloroquine sulfate (HCQ) in tablets and synthetic urine samples. CNNS were synthesized by hydrothermal route (200°C, 10 h) using melamine and citric acid as their precursors. The carbon nitride nanosheets-based electrode (CNNS/E) presented a linear dynamic range for HCQ (LDR), ranging from 10.0 nmol l À 1 to 6.92 μmol l À 1 , and detection (LOD) and quantification limits (LOQ) of 0.16 nmol l À 1 and 0.52 nmol l À 1 , respectively. LOD and LOQ were calculated by the equations: LOD = 3(S d /b), and LOQ = 10(S d /b). The modified sensor presented excellent relative standard deviations for parameters such as repeatability (2.39 % and 1.87 %) and reproducibility (3.22 % and 2.32 %) in HCQ oxidation peaks (1 and 2). The CNNS/E has not shown significant variations in its anodic signal intensity in the presence of some organic and inorganic substances. It is worth bearing in mind that CNNS/E can be easily manufactured and the sensor has the lowest HCQ detection limits reported so far. The proposed sensor was successfully applied for HCQ determination in tablets and synthetic urine, showing good recovery values and an error of 0.60 % about comparative method in tablet samples, assuring the quality of the method.

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Electrochemical sensors are analytical tools that offer great portability, ease automation, miniaturization capability, and low cost compared to other analytical techniques and methods. For those reasons, there is a growing search for these electrodes to obtain better analysis conditions. This advance is reflected in new patents and articles, which were intensified mainly with the arising of chemically modified electrodes and self-sufficient equipment. Besides, this study brings together and discusses the main aspects of electrochemical methods, the development of electrodes and their modifiers, as well as the perspectives for these electroanalytical tools. Os sensores eletroquímicos são ferramentas de análise que oferecem maior portabilidade, facilidade de automação, capacidade de miniaturização e baixo custo em relação a outras técnicas e métodos analíticos. Por essas razões, existe uma crescente busca pelo desenvolvimento desses eletrodos a fim de se obter melhores condições de análise. Esse avanço reflete em novas patentes e artigos que se intensificaram, principalmente com o surgimento dos eletrodos quimicamente modificados e equipamentos autossuficientes. Em suma, esse estudo reúne e discute aspectos fundamentais concernentes aos métodos eletroquímicos, o avanço no desenvolvimento dos eletrodos e seus modificantes, além das perspectivas para essas ferramentas eletroanalíticas.

We have obtained kefir biofilms loaded with Maytenus rigida extract. The main goal was to evaluate the influence of the addition of the extract on the biofilms microtexture using stereometric and fractal parameters. Atomic force microscopy, Fourier transform infrared spectroscopy, and contact angle tecniques were used to evaluate the topography, chemical interation and wettability of the biofilms. Chemical evaluation showed that the extract interacts with the polymeric matrix of the biofilms, changing their structure. This behavior affected the surface energy because the wettability decreased when the Maytenus content increased. The surface morphology was also affected and suggested the prevalence of bacteria and yeast at lower and higher extract concentrations, respectively. The surface roughness increased according to the increase in the extract concentration. Texture parameters revealed that the biofilm with lowest concentration had deeper furrows than for higher concentration. Advanced fractal parameters revealed that topographic uniformity, percolation and texture homogeneity were more suitable for the biofilm with 0.25 g.L -1 of extract. These results indicate that this biofilm have promising 3D micromorphology for regenerative medicine application. Furthermore, the physics tools used revealed to be very useful for characterizing of the microtexture of polymeric-based biological materials.

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