No abstract

Investigations about the nanocavities/bubbles formation by inert gas ion implantation in Si matrix and its properties have constituted an ongoing challenge in material science. Dislocation/extended defects (likely the {113} defects) are produced by post-implant annealing, which affect directly the nanocavities/bubbles structural evolution. In this work, the formation of defects induced by Xenon gas ion implantation in a Si sample (#Si-pristine) was studied by high-resolution reciprocal space mappings (RSM) and non-conventional X-ray Multiple Diffraction (XRMD) using synchrotron radiation. For this, Xe+ ions (80 keV; 5x1015 cm-2) were implanted in Si(001) at room temperature. Subsequently, the as-implanted samples were thermally annealed in air atmosphere at 600, 700 and 800 °C for 30 min in order to nucleate Xe nanobubbles that were detected in annealed samples by TEM images. Differences in the diffracted intensity pattern, along the crystal truncation rod, were detected in the Si (113) asymmetrical RSM for as-implanted and annealed samples, in comparison to pristine Si, indicating defect contribution along in-plane an out-of-plane directions. The ω(incident):Φ(azimuthal) coupled scans of two XRMD cases: 3-beam Bragg-Surface-Diffraction (BSD) (000)(002)(1-11) and the 4-beam (000)(002)(1-1-1)(1-13) have shown expected broader peaks (as-implanted sample) in comparison to the pristine sample, besides the ω-axis intensity asymmetry (c-axis strain induced). Furthermore, the analysis of all BSD mappings has provided: i) the annealing effect of reducing the lattice strain (600 and 700 °C samples), and ii) a huge surface effect through the diffuse scattering (800 °C-sample). As to the 4-beam case, a strong streak (diffraction condition trace) was observed for annealed sample patterns. This remarkable effect can be associated to the {113} defects, which are in the same direction of the secondary/coupling diffracting planes (XRMD phenomenon). It is believed that these defects break the spatial coherence, increasing the streak intensity. On the other hand, the streak is suppressed by the primary extinction effect in the pristine-Si and as-implanted samples. Financial support by Brazilian Synchrotron Light Laboratory (LNLS), CAPES, CNPq and FAPEMA.

The COVID‐19 pandemic is still a continuing worldwide challenge for public health systems. Early and ultrasensitive identification of the infection is essential for preventing the spread of COVID‐19 by pre‐symptomatic or asymptomatic individuals, particularly in the community and in‐home settings. This work presents a versatile photoelectrochemical (PEC) immunosensor for SARS‐CoV‐2 detection based on a composite material formed by bismuth vanadate (BiVO4) and strontium titanate (SrTiO3). The PEC platform was denoted as BiVO4/SrTiO3/FTO, and it can be tuned for the detection of either Spike (S) or Nucleocapsid (N) protein by simply altering the antibody immobilized on the platform's surface. Chemical, morphological, and electrochemical characterizations were performed by X‐Ray Diffraction, Scanning Electron microscopy, Energy‐dispersive X‐ray spectroscopy, Electrochemical Impedance Spectroscopy, and Amperometry. With a simple sensing architecture of the PEC platform, it was possible to achieve a linear response range of 0.1 pg mL−1 to 1000 ng mL−1 for S protein and 0.01 pg mL−1 to 1000 ng mL−1 for N protein. The PEC immunosensors presented recovery values for the two SARS‐CoV‐2 proteins in artificial saliva samples between 97 % and 107.20 % suggesting a good accuracy for the proposed immunosensors.

This work describes the development of a photoelectrochemical sensor for glucose quantification exploiting a light assisted-batch injection analysis (BIA) cell. A light-emitting diode (LED) lamp was employed to control the incidence of light on the p-Cu2O/n-Cu2O/fluorine-doped tin oxide(FTO) photoactive platform in BIA cell. The p-Cu2O/n-Cu2O/FTO platform was constructed by electrodepositing n-Cu2O and p-Cu2O and the characteristics of electrodeposited Cu2O films were investigated by X-ray diffraction (XRD), Raman spectroscopy, and electrochemical impedance spectroscopy. The light assisted-batch injection analysis of glucose based on the illuminated p-Cu2O/n-Cu2O/FTO photoelectrode presented a linear response of 10 μmol L-1 mmol L-1, a limit of detection of 4.0 μmol L-1, and sensitivity of 0.768 ± 0.011 μA L μmol-1 cm-2. The system presented an average recovery value of 96% when applied to the determination of glucose in an artificial saliva sample, which indicates that the incidence of light on photoelectroactive platforms is a promising approach for the determination and quantification of glucose.