Study of Composite Structures Based on a Porous Silicon Matrix and Nanoparticles Ag/Zno Used as Non-Invasive Highly Sensitive Biosensor Devices

In this work composite structures based on a porous silicon were obtained and studied. Porous matrices were formed by electrochemical etching in aqueous solutions of hydrofluoric acid. Based on the obtained substrates, por-silicon (Si)/silver (Ag) and por-Si/zinc oxide (ZnO) composite structures were formed. These composites were functionalized by various methods (electro (E)-, thermo (T)-, electrothermal exposure) as a result of which the structures were modified. When studying the samples by scanning electron microscopy (SEM), it was concluded that silver nanoparticles actively diffused into the pores under these technological modes of functionalization. The por-Si/Ag and por-Si/ZnO composite structures were also studied using the following methods: infrared (IR) spectroscopy and Raman ultrasoft X-ray emission spectroscopy. Also, the photoluminescent characteristics of the samples were studied. Based on the obtained results, it was concluded that functionalization methods actively change the phase composition of structures and the optical properties of composites

Origin of order in bionanostructures

Analysis of corneal nanocoatings across insect species provides clues to the origin of order in the bionanoworld.</p

Overexpression of Wg leads to a dramatic loss of nipple arrays, correlating with the glossy eye phenotype.

<p>Three-dimensional AFM representation of nipple arrays of wild-type flies (A) and the <i>GMR-Gal4; UAS-Wg</i> flies overexpressing Wg in postmitotic eye cells (B). A catastrophic loss of nipples is observed upon Wg overexpression, with few remaining nipples randomly spaced with huge gaps between them. This loss of nipples correlates with the overall glossy appearance of the mutant eyes (B, insert), as opposed to the wild-type eyes (A, insert). The eye size in <i>GMR-Gal4; UAS-Wg</i> flies is also reduced due to photoreceptor loss. A light microscope was used to take images of the whole eyes shown in inserts.</p

Fine structure AFM images of <i>Drosophila</i> ommatidial surface reveal irregularities in the lens material deposition in <i>frizzled</i> mutants.

<p>Corneal surface of the wild-type (A, B) and <i>frizzled</i> mutant (C, D) eyes was analyzed at high resolution with AFM. Field of view is 10×10 µm. Arrows indicate intercalations of the lens material between ommatidial lens borders in the <i>frizzled</i> mutant (C, D). (A, C) represent top views, while (B, D) are their three-dimensional representations.</p

High-resolution analysis of the <i>Drosophila</i> nipple arrays.

<p>Corneal surface of the wild-type (A) and <i>frizzled</i> mutant (D) eyes was analyzed at high resolution with AFM. Field of view is 3×3 µm. Fourier transform spectra of the AFM images are shown as inserts in (A, D). (B, E) are cross-sectional profiles of representative scans of wild-type (B) and <i>frizzled</i> mutant (E) cornea of ca. 8 µm length. Blue lines in (B, E) are smoothing curves of the height recording curves depicted with the red lines. (C, F) are representative cross-sectional 4 µm-long profiles of flat areas of wild-type (C) and <i>frizzled</i> mutant (F) cornea such as those on (A, D).</p

Diffraction patterns of <i>Drosophila</i> cornea confirm lack of order in ommatidial arrangement in <i>frizzled</i> mutants.

<p>Corneal preparations from wild-type (A) and <i>frizzled</i> mutant (B) eyes were irradiated with a laser beam of 630 nm to collect diffraction patterns.</p