One-dimensional nanostructures of polypyrrole for shielding of electromagnetic interference in the microwave region

Polypyrrole one-dimensional nanostructures (nanotubes, nanobelts and nanofibers) were prepared using three various dyes (Methyl Orange, Methylene Blue and Eriochrome Black T). Their high electrical conductivity (from 17.1 to 60.9 S cm−1), good thermal stability (in the range from 25 to 150◦ C) and resistivity against ageing (half-time of electrical conductivity around 80 days and better) were used in preparation of lightweight and flexible composites with silicone for electromagnetic interference shielding in the C-band region (5.85–8.2 GHz). The nanostructures’ morphology and chemical structure were characterized by scanning electron microscopy, Brunauer–Emmett–Teller specific surface measurement and attenuated total reflection Fourier-transform infrared spectroscopy. DC electrical conductivity was measured using the Van der Pauw method. Complex permittivity and AC electrical conductivity of respective silicone composites were calculated from the measured scattering parameters. The relationships between structure, electrical properties and shielding efficiency were studied. It was found that 2 mm-thick silicone composites of polypyrrole nanotubes and nanobelts shield almost 80% of incident radiation in the C-band at very low loading of conductive filler in the silicone (5% w/w). Resulting lightweight and flexible polypyrrole composites exhibit promising properties for shielding of electromagnetic interference in sensitive biological and electronic systems. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech Republicproject DKRVO [RP/CPS/2020/006]; [A2_FCHI_2020_030

Coating of leather with dye-containing antibacterial and conducting polypyrrole

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic dyes: crystal violet, neutral red, methyl orange, acriflavine, and methylene blue. This technique ensures the uniform coating of collagen fibers with polypyrrole and incorporation of organic dyes. The surface morphology was observed with scanning electron microscopy and the transverse profile, reflecting the penetration of the conducting phase into the leather body with optical microscopy. While the polypyrrole coating endows leather with electrical conductivity, organic dyes are expected to affect the polymer morphology and to provide an antibacterial effect. The lowest sheet resistance and antibacterial activity were obtained with crystal violet. This type of coating was characterized in more detail. Infrared spectroscopy confirmed the coating of collagen fibers with polypyrrole and dye incorporation. Mechanical properties were extended to the cyclic bending of the leather at various angles over 5000 cycles. The relative resistance changes were a few percent, indicating good electrical stability during repeated mechanical stress.Ministry of Education, Youth and Sports of the Czech Republic [FRC RO70200003025/2102]Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: FRC RO70200003025/210

Pressure-sensitive conducting and antibacterial materials obtained by in situ dispersion coating of macroporous melamine sponges with polypyrrole

Melamine sponges were coated with polypyrrole during the in situ polymerization of pyrrole. The precipitation polymerization was compared with the dispersion mode, that is, with the preparation in the presence of poly(N-vinylpyrrolidone) and nanosilica as colloidal stabilizers. The coating of sponges during the dispersion polymerization leads to the elimination of the undesired polypyrrole precipitate, improved conductivity, and increased specific surface area. The sponges were tested with respect to their conductivity and as pressure-sensitive conducting materials with antibacterial performance. © 2021 The Authors. Published by American Chemical Society.Czech Science FoundationGrant Agency of the Czech Republic [19-04859S, 21-09830S]; internal Prague University research project [A2_FCHI_2021_003]; Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [DKRVO RP/CPS/2020/001]RP/CPS/2020/001; A2_FCHI_2021_003; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Grantová Agentura České Republiky, GA ČR: 19-04859S, 21-09830

Polypyrrole nanotubes and their carbonized analogs: Synthesis, characterization, gas sensing properties

Polypyrrole (PPy) in globular form and as nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the absence and presence of methyl orange, respectively. They were subsequently converted to nitrogen-containing carbons at 650 °C in an inert atmosphere. The course of carbonization was followed by thermogravimetric analysis and the accompanying changes in molecular structure by Fourier Transform Infrared and Raman spectroscopies. Both the original and carbonized materials have been tested in sensing of polar and non-polar organic vapors. The resistivity of sensing element using globular PPy was too high and only nanotubular PPy could be used. The sensitivity of the PPy nanotubes to ethanol vapors was nearly on the same level as that of their carbonized analogs (i.e., ~18% and 24%, respectively). Surprisingly, there was a high sensitivity of PPy nanotubes to the n-heptane vapors (~110%), while that of their carbonized analog remained at ~20%. The recovery process was significantly faster for carbonized PPy nanotubes (in order of seconds) compared with 10 s of seconds for original nanotubes, respectively, due to higher specific surface area after carbonization. © 2016 by the authors; licensee MDPI, Basel, Switzerland

Vhodné trénovací algoritmy pro detekci úchopových bodů pomocí ASP U-Net

Robotic manipulation with nontrivial or irregular objects, which provide various types of grasping points, is of both academic and industrial interest. Recently, a powerful data-driven ASP U-Net deep neural network has been proposed to detect feasible grasping points of manipulated objects using RGB data. The ASP U-Net showed the ability to detect feasible grasping points with exceptional accuracy and more than acceptable inference times. So far, the network has been trained using an Adam optimizer only. However, in order to optimally utilize the potential of ASP U-Net, it was necessary to perform a systematic investigation of suitable training algorithms. Therefore, the aim of this contribution was to extend the impact of ASP U-Net by recommending suitable training algorithms and their parameters based on the result of training experiments.Robotická manipulace s netriviálními nebo nepravidelnými objekty, které poskytují různé typy úchopových bodů, je předmětem zájmu akademické sféry i průmyslu. Nedávno byla navržena výkonná datově řízená hluboká neuronová síť ASP U-Net pro detekci dostupných úchopových bodů manipulovaných objektů pomocí vizuálních dat. ASP U-Net prokázala schopnost detekovat proveditelné úchopové body s výjimečnou přesností a více než přijatelnou dobou inference. Síť byla dosud trénována pouze pomocí Adam algoritmu. Pro optimální využití potenciálu sítě ASP U-Net však bylo nutné provést systematický průzkum vhodných tréninkových algoritmů. Cílem tohoto příspěvku proto bylo rozšířit vliv ASP U-Net doporučením vhodných tréninkových algoritmů a jejich parametrů na základě výsledků trénovacích experimentů

Aplikace hashovací funkce pro generování modulačních dat v systému RadCom

The challenge of current radiocommunication systems is the efficient use of the frequency spectrum. One of the rapidly evolving tools is a RadCom system, which combines the functionality of a radar sensor with a communication interface. RadCom systems are used in several fields, and the presented work is focused on their applications in the automotive industry. The goal was to design a modulation technique and generate modulation data, which will be suitable for radar determination of the distance and velocity of targets, but also enable their mutual communication. A model of the RadCom system, which simultaneously allows a simulation of detection and communication of several moving targets, has been developed. Herein, a method of generating pseudo-random data based on the MD5 hashing algorithm is described. The proposed method of radar signal processing enables unambiguous detection of moving targets and determination of the position and velocity of these targets. Principles of synchronization and coding of a radar and communication mode of the RadCom system are explained. A numerical verification of the proposed algorithms using simulation tools is discussed in the final part of the work. The proposed system solution achieves more than 70% probability that the decoded message will not contain erroneous bits.Výzvou současných radiokomunikačních systémů je efektivní využití frekvenčního spektra. Jedním z rychle se vyvíjejících nástrojů je systém RadCom, který kombinuje funkčnost radarového senzoru s komunikačním rozhraním. Systémy RadCom se používají v několika oblastech a prezentovaná práce je zaměřena na jejich aplikace v automobilovém průmyslu. Cílem bylo navrhnout modulační techniku a vygenerovat modulační data, která budou vhodná pro radarové určování vzdálenosti a rychlosti cílů, ale také umožní jejich vzájemnou komunikaci. Byl vyvinut model systému RadCom, který současně umožňuje simulaci detekce a komunikace několika pohybujících se cílů. Je popsán způsob generování pseudonáhodných dat na základě hashovacího algoritmu MD5. Navržený způsob zpracování radarového signálu umožňuje jednoznačnou detekci pohybujících se cílů a určení polohy a rychlosti těchto cílů. Jsou vysvětleny principy synchronizace a kódování radaru a komunikační režim systému RadCom. V závěrečné části práce je diskutováno numerické ověření navržených algoritmů pomocí simulačních nástrojů. Navržené systémové řešení dosahuje více než 70% pravděpodobnosti, že dekódovaná zpráva nebude obsahovat chybné bity

Klasifikace polymerů na základě stupně jejich průhlednosti ve SWIR spektru

Detection, classification and sorting of polymeric particles is a common task required in recycling industry. In the proposed work, an innovative method for detection of polymeric particles and their classification is introduced. The method is based on evaluation of images of polymeric particles, obtained from short-wavelength infrared (SWIR) camera, by convolutional neural network (CNN). Compared to conventionally used spectroscopes or hyper-spectral imaging, this method utilizes single wavelength (1 050 nm) and a degree of polymer transparency serves as the main descriptor. Five different polymers (ABS, ABS-T, Nylon, PETG, PLA) in form of regular blocks (size 15 × 15 × 0.3 mm) were used in the experiment. In total 203 images (size 288 × 288 px) were prepared for CNN training and 67 for testing. Scalable ASP U-Net was tested in 6 combinations and their outputs were compared. According to used intersection over union metrics over all outputs, the topology with 64 filters and depth of 3 exhibited the best results.Detekce, klasifikace a třídění polymerních částic je v recyklačním průmyslu běžným úkolem. V navrhované práci je představena inovativní metoda detekce polymerních částic a jejich klasifikace. Metoda je založena na vyhodnocování snímků polymerních částic získaných z krátkovlnné infračervené kamery (SWIR) pomocí konvoluční neuronové sítě (CNN). Ve srovnání s konvenčně používanými spektroskopy nebo hyperspektrálním zobrazováním využívá tato metoda jedinou vlnovou délku (1 050 nm) a jako hlavní deskriptor slouží stupeň průhlednosti polymeru. V experimentu bylo použito pět různých polymerů (ABS, ABS-T, Nylon, PETG, PLA) ve formě pravidelných bloků (velikost 15 × 15 × 0,3 mm). Celkem bylo připraveno 203 obrázků (velikost 288 × 288 px) pro trénování CNN a 67 pro testování. Škálovatelná ASP U-Net byla testována v 6 kombinacích a jejich výstupy byly porovnány. Podle použitých metrik průniku nad sjednocením nad všemi výstupy vykazovala nejlepší výsledky topologie se 64 filtry a hloubkou 3

Electromagnetic interference shielding of polypyrrole nanostructures

Polypyrrole (PPy) is an electrically conductive organic material perspective for application in the field of electromagnetic interference shielding (EMI). The presented fundamental study focuses on the shielding efficiency of three various morphologies of PPy (globules, nanotubes and microbarrels). Powdered samples in both protonated and deprotonated form were embedded at various concentrations (1, 3 and 5 % w/w) in a composite system with a transparent silicone matrix cured at temperatures 25 and 150 °C. The ability of PPy to reflect or absorb electromagnetic radiation in the C-band region covering the range from 5.85 to 8.2 GHz was evaluated. The relationship between the morphology of PPy, its DC and AC electrical conductivity, permittivity and shielding efficiency was studied. The PPy nanotubes with the DC conductivity of 60.8 S cm–1 exhibited shielding efficiency S21 = –13.27 dB at 5% w/w concentration in the composite, which corresponds to transparency of 21.7 % only. It was found that the magnitude of electrical conductivity together with the aspect ratio of PPy morphology determines the shielding efficiency whereas the type of morphology is responsible for absorption or reflection mechanism of EMI shielding. Hence, the appropriate adjustment of both the electrical conductivity and the morphology should be used in the future lightweight and flexible EMI shields with tunable shielding efficiency and mechanism of shielding. © 2020 Elsevier B.V.Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [RP/CPS/2020/006]; [A2_FCHI_2020_030

Room Temperature Detection of Hydrogen Peroxide Vapor by Fe2O3:ZnO Nanograins

In this report, a Fe2O3:ZnO sputtering target and a nanograins-based sensor were developed for the room temperature (RT) detection of hydrogen peroxide vapor (HPV) using the solid-state reaction method and the radio frequency (RF) magnetron sputtering technique, respectively. The characterization of the synthesized sputtering target and the obtained nanostructured film was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analyses. The SEM and TEM images of the film revealed its homogeneous granular structure, with a grain size of 10–30 nm and an interplanar spacing of Fe2O3 and ZnO, respectively. EDX spectroscopy presented the real concentrations of Zn in the target material and in the film (21.2 wt.% and 19.4 wt.%, respectively), with a uniform distribution of O, Al, Zn, and Fe elements in the e-mapped images of the Fe2O3:ZnO film. The gas sensing behavior was investigated in the temperature range of 25–250 °C with regards to the 1.5–56 ppm HPV concentrations, with and without ultraviolet (UV) irradiation. The presence of UV light on the Fe2O3:ZnO surface at RT reduced a low detection limit from 3 ppm to 1.5 ppm, which corresponded to a response value of 12, with the sensor’s response and recovery times of 91 s and 482 s, respectively. The obtained promising results are attributed to the improved characteristics of the Fe2O3:ZnO composite material, which will enable its use in multifunctional sensor systems and medical diagnostic devices

Conducting polypyrrole-coated leathers

Conducting polymers are promising materials applicable as interfaces in various functional materials given they intrinsically possess electronic and ionic conductivity. Herein, a conducting polymer, polypyrrole (PPy) was explored for surface modification of three different leathers via in-situ oxidation of pyrrole in the absence and the presence of two stabilizing polymers, hydroxypropylcellulose and poly(N-vinylpyrrolidone). Colloidal dispersed PPy assemblies were formed with colloidal stabilizers along with PPy-coated leathers and hampered the formation of PPy precipitates that would otherwise contaminate the leather surface. The surface-modified bio-based composites were characterized by FTIR and Raman spectroscopy, and optical and scanning electron microscopy. PPy was deposited on collagen fibers on both sides of the leather. The thickness of the PPy layer varied between 24 and 200 mu m. Mechanical properties of the leathers manifested themselves by the decrease in tensile strength and elongation at break after the modification process. Sheet resistances were in the range of 100-103 k omega/sq with the highest values observed for materials modified in the presence of the polymeric stabilizers. Different sheet resistances were obtained for the top and bottom sides of the leathers depending on the surface finishing. Furthermore, the modified leathers were subjected to cyclic bending tests and the variation in their resistivity was studied. The conductivity and electroactivity of the modified materials may serve as guidance for the rational design of intelligent leathers in the footwear, as heating elements, and in energy storage.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: FRC RO70200003025/2102, FSR-ST.2020/005Ministry of Education, Youth and Sports of the Czech Republic [FSR-ST.2020/005, FRC RO70200003025/2102