Can Plasmon Change Reaction Path? : Decomposition of Unsymmetrical Iodonium Salts as an Organic Probe

Plasmon-assisted transformations of organic compounds represent a novel opportunity for conversion of light to chemical energy at room temperature. However, the mechanistic insights of interaction between plasmon energy and organic molecules is still under debate. Herein, we proposed a comprehensive study of the plasmon-assisted reaction mechanism using unsymmetric iodonium salts (ISs) as an organic probe. The experimental and theoretical analysis allow us to exclude the possible thermal effect or hot electron transfer. We found that plasmon interaction with unsymmetrical ISs led to the intramolecular excitation of electron followed by the regioselective cleavage of C–I bond with the formation of electron-rich radical species, which cannot be explained by the hot electron excitation or thermal effects. The high regioselectivity is explained by the direct excitation of electron to LUMO with the formation of a dissociative excited state according to quantum-chemical modeling, which provides novel opportunities for the fine control of reactivity using plasmon energy.Peer reviewe

Final report of the project - Secure erasing memory chips using electromagnetic pulse

The subject of this contractual research was the theoretical analysis and the mathematical model of the problem of electromagnetic pulse penetration and involvement of storage function of the memory chips. The report includes description of the experimental preparation memory chip, methodology of memory media testing, experiment shielding, software scanning of the memory chip, EMP generation, EMP intensity measurement. \nSummary of results of experiments of EMP influence on the memory media.\nA comprehensive research report was handed over to NUKIB representatives on 31 May 2018. NUKIB representatives confirmed receipt of the report. \nDefense of the project results took place on 27.6.2018 in the NUKIB building. Project goals were fulfilled. The agreed amount was invoiced for this report.\n\

Secure erasing memory chips using electromagnetic pulse - phase 1

The subject of this contractual research was to perform study of technologies and principles of flash memories currently available on the market. The research report focuses on technological advancements in their development, the readability of stored / deleted data by available laboratory techniques, and the interaction of these memories with the electromagnetic pulse.\nThe outcome was handed over to NUKIB representatives on 29 March 2018. \nThe project was fulfilled, the agreed amount was invoiced for this report.\n\n\

Interaction of selected gases with zinc phthalocyanine thin films: theoretical and experimental studies

In this work we studied both theoretically and experimentally interactions between zinc phthalocyanine (ZnPc) and selected gases (Ar, He, N2, O2, H2, NO2). Specifically, we focused on electrical conductivity as important macroscopical physical parameter reflecting ZnPc/gas complexes interaction states. To interpret the measured data and determine the main parameters that influence the resistivity/charge transport ability of ZnPc in a specific gas atmosphere, the density functional theory (DFT) has been used. Combining experimental results and DFT modeling we were able to characterize states/parameters influencing charge transport conditions from new and comprehensive perspectives

Molecular Recognition of Phenylalanine Enantiomers onto a Solid Surface Modified with Electropolymerized Pyrrole‐β‐Cyclodextrin Conjugate

We report the electrochemical deposition of a beta-cyclodextrin pyrrole conjugate (Py-beta-CD) on an electrode surface including i) characterization based on surface-enhanced Raman scattering and field-emission scanning electron microscopy; ii) studies of the molecular recognition of enantiomers of phenylalanine methyl ester hydrochlorides (Phe) based on linear sweep voltammetry and a quartz crystal microbalance. The PPy-beta-CD polymeric layer on a metallic substrate is distinguished by its inhomogeneity, in which both highly ordered beta-CD units and highly disordered polymer chains are observed. The voltammetric recognition results showed that PPy-beta-CD exhibited a higher sensitivity for d-Phe (138 +/- 15)x10(3) than for l-Phe (6 +/- 1)x10(3) within the concentration range 0.1-0.75 mM (n=3) despite the differences in the polymer arrangement on the surface. A possible mechanism of molecular recognition of phenylalanine enantiomers is discussed

Study of Photoregeneration of Zinc Phthalocyanine Chemiresistor after Exposure to Nitrogen Dioxide

In this work, we present a complex study of photoregeneration of a zinc phthalocyanine (ZnPc) sensor by illumination from light-emitting diodes (LEDs). It includes an investigation of photoregeneration effectivity for various wavelengths (412–723 nm) of incident light carried out at sensor operating temperatures of 55 °C. It is demonstrated that the efficiency of photoregeneration is increasing with a decrease in the light wavelength. In the region of longer wavelengths (723–630 nm), the regeneration degree (RD) was low and ranged from 12% to 15%. In the region of shorter wavelengths (518–412 nm), the RD rose from 35% for 518 nm to 94% for 412 nm. The efficiency of photoregeneration is also shown to be higher in comparison with the temperature regeneration efficiency. In order to understand the chemism of photoregeneration processes, the electrical measurements are supplemented with Raman and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) studies. The spectroscopic results showed that nitrogen dioxide bonds to the Zn atom in ZnPc in the form of NO2− and NO−, i.e., partial decomposition of NO2 molecules occurs during the interaction with the surface. NAP-XPS spectra proved that light illumination of the ZnPc surface is essential for almost complete desorption of NOx species. At the same time, it is demonstrated that in case of long-time exposure or exposure of a ZnPc chemiresistor with a high concentration of NO2, the oxygen, released due to the NO2 decomposition, slowly but irreversibly oxidizes the layer. This oxidation process is most probably responsible for the sensor deactivation observed in sensor experiments with high NO2 concentrations. Based on these studies, the mechanism of nitrogen dioxide interaction with zinc phthalocyanine both under LED illumination and in dark conditions is proposed, and a special method for the sensor operation called “constant exposure dose” is established

New Insights towards High-Temperature Ethanol-Sensing Mechanism of ZnO-Based Chemiresistors

In this work, we investigate ethanol (EtOH)-sensing mechanisms of a ZnO nanorod (NRs)-based chemiresistor using a near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). First, the ZnO NRs-based sensor was constructed, showing good performance on interaction with 100 ppm of EtOH in the ambient air at 327 °C. Then, the same ZnO NRs film was investigated by NAP-XPS in the presence of 1 mbar oxygen, simulating the ambient air atmosphere and O2/EtOH mixture at the same temperature. The partial pressure of EtOH was 0.1 mbar, which corresponded to the partial pressure of 100 ppm of analytes in the ambient air. To better understand the EtOH-sensing mechanism, the NAP-XPS spectra were also studied on exposure to O2/EtOH/H2O and O2/MeCHO (MeCHO = acetaldehyde) mixtures. Our results revealed that the reaction of EtOH with chemisorbed oxygen on the surface of ZnO NRs follows the acetaldehyde pathway. It was also demonstrated that, during the sensing process, the surface becomes contaminated by different products of MeCHO decomposition, which decreases dc-sensor performance. However, the ac performance does not seem to be affected by this phenomenon

Surface Enhancement Using Black Coatings for Sensor Applications

International audienceThe resolution of a quartz crystal microbalance (QCM) is particularly crucial for gas sensor applications where low concentrations are detected. This resolution can be improved by increasing the effective surface of QCM electrodes and, thereby, enhancing their sensitivity. For this purpose, various researchers have investigated the use of micro-structured materials with promising results. Herein, we propose the use of easy-to-manufacture metal blacks that are highly structured even on a nanoscale level and thus provide more bonding sites for gas analytes. Two different black metals with thicknesses of 280 nm, black aluminum (B-Al) and black gold (B-Au), were deposited onto the sensor surface to improve the sensitivity following the Sauerbrey equation. Both layers present a high surface roughness due to their cauliflower morphology structure. A high response (i.e., resonant frequency shift) of these QCM sensors coated with a black metal layer was obtained. Two gaseous analytes, H2O vapor and EtOH vapor, at different concentrations, are tested, and a distinct improvement of sensitivity is observed for the QCM sensors coated with a black metal layer compared to the blank ones, without strong side effects on resonance frequency stability or mechanical quality factor. An approximately 10 times higher sensitivity to EtOH gas is reported for the QCM coated with a black gold layer compared to the blank QCM sensor