Spectroscopic ellipsometry study of gold nanostructures for LSPR bio-sensing applications

This main aim of this work is the development of optical biosensors based on the LSPR phenomenon in nano-structured gold films suitable for detection of low molecular weight analytes such as mycotoxins. A simple technology of annealing thin gold films was utilized for the formation of gold nano-islands exhibiting the LSPR effect. The morphology of gold nano-structures produced was studied with SEM and AFM, and their optical properties were analysed with UV-visible absorption spectroscopy and spectroscopic ellipsometry (SE). The position of LSPR band appeared to depend on the dimensions of gold nano-islands. The dependence of the LSPR band spectral shift on the refractive index of a medium was studied with both UV-vis absorption and SE, and the refractive index sensitivity (RIS) was evaluated. The method of SE gave from two to three times higher values of RIS as compared to those obtained by absorption spectroscopy. LSPR bio-sensing tests were attempted using total internal reflection ellipsometry (TIRE); a noticeable spectral shift was recorded on course of immune binding of Aflatoxin B1 to specific antibodies immobilized on the surface of gol

ЛІРИКО-ДРАМАТИЧНИЙ ТИП ГЕРОЯ УКРАЇНСЬКИХ НАРОДНИХ ДУМ

The paper highlights the basic features of the lyric-dramatic type of epic hero as seen through the prism of his subjective, ideological, and aesthetic self-articulation. Such a character is distinguished by his deep lyricism and passionate struggle against unsatisfactory reality, and determined chiefl y by his strong relation to nature which allows a deeper comprehension of the hero’s feelings and emotional experience as well as of the meaning of the dumas in general.Через суб’єктивну, емоційну, ідейно-естетичну оцінку дійсності у статті простежено особливості лірико-драматичного типу епічного героя, якому властива глибока ліричність, внутрішньо-емоційна боротьба з негативними явищами дійсності. Зумовленість характеру природним началом дає змогу глибше розкрити зміст, зрозуміти почуття й переживання лірико-драматичного героя українських народних дум

Electrochemical Aptasensor for Detection of Dopamine

This work presents a proof of concept of a novel, simple, and sensitive method of detection of dopamine, a neurotransmitter within the human brain. We propose a simple electrochemical method for the detection of dopamine using a dopamine-specific aptamer labeled with an electrochemically active ferrocene tag. Aptamers immobilized on the surface of gold screen-printed gold electrodes via thiol groups can change their secondary structure by wrapping around the target molecule. As a result, the ferrocene labels move closer to the electrode surface and subsequently increase the electron transfer. The cyclic voltammograms and impedance spectra recorded on electrodes in buffer solutions containing different concentration of dopamine showed, respectively, the increase in both the anodic and cathodic currents and decrease in the double layer resistance upon increasing the concentration of dopamine from 0.1 to 10 nM L-1. The high affinity of aptamer-dopamine binding (KD ≈ 5 nM) was found by the analysis of the binding kinetics. The occurrence of aptamer-dopamine binding was directly confirmed with spectroscopic ellipsometry measurements

Formation and UV-vis studies of lead sulfide nanoparticles

An elegant technique of synthesizing semiconductor lead sulfide nanoparticles (PbS-NPS) embedded in Langmuir-Blodgett (LB) films is presented here. Stearic acids have been used as a matrix to form and grow the quantum-sized PbS. Pure Y-type Pb-salts of stearic acid (SA) LB films were prepared at a dipping speed of 15 mm/min and surface pressure of 28 mN/m. PbS-NPs were formed inside LB films of SA by exposure the LB films to hydrogen sulfide (H2S) gas. The preparation of PbS-NPs is discussed in terms of particle formation and growth. The presence of PbS-NPs was investigated by UV-visible absorption. It was found that the PbS-NPs within SA LB films indicated a large blue shift of the optical absorption edge. The estimation of the size distribution performed by optical measurements allows one to attribute the particle range a few nanometers. This figure seems to depend upon the reaction conditions as well as the quality of the initial LB films

Resistivity network and structural model of the oxide cathode for CRT application

In this paper, the electrical properties of oxide cathode and oxide cathode plus, supplied by LG Philips Displays, have been investigated in relation to different cathode activation regimes and methods. Oxide cathode activation treatment for different durations has been investigated. The formations of the compounds associated to the diffusion of reducing elements (Mg, Al, and W) to the Ni cap surface of oxide cathode were studied by a new suggestion method. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) was used as analytical techniques. Al, W, and Mg doping elements take place during heating to 1080 K (Ni-Brightness) under a rich controlled Ba–SrO atmosphere through an acceleration life test. The chemical transport of these elements was occurred mainly by the Ni cap grain boundary mechanism with significant pile-up of Mg compounds. Al and W show a superficial concentrations and distribution. A new structural and resistivity network model of oxide cathode plus are suggested. The new structural model shows a number of metallic and metallic oxide pathways are exist at the interface or extended through the oxide coating. The effective values of the resistances and the type of the equivalent circuit in the resistivity network model are temperature and activation time dependent.</p

Electrochemical inhibition bacterial sensor array for detection of water pollutants: artificial neural network (ANN) approach

This work reports on further development of an inhibition electrochemical sensor array based on immobilized bacteria for the preliminary detection of a wide range of organic and inorganic pollutants, such as heavy metal salts (HgCl2, PbCl2, CdCl2), pesticides (atrazine, simazine, DDVP), and petrochemicals (hexane, octane, pentane, toluene, pyrene, and ethanol) in water. A series of DC and AC electrochemical measurements, e.g., cyclic voltammograms and impedance spectroscopy, were carried out on screen-printed gold electrodes with three types of bacteria, namely Escherichia coli, Shewanella oneidensis, and Methylococcus capsulatus, immobilized via poly L-lysine. The results obtained showed a possibility of pattern recognition of the above pollutants by their inhibition effect on the three bacteria used. The analysis of a large amount of experimental data was carried out using an artificial neural network (ANN) programme for more accurate identification of pollutants as well as the estimation of their concentration. The results are encouraging for the development of a simple and cost-effective biosensing technology for preliminary in-field analysis (screening) of water samples for the presence of environmental pollutants

Electronic Structure of (Organic-)Inorganic Metal Halide Perovskites: The Dilemma of Choosing the Right Functional

Organic–inorganic metal halide perovskites (HaPs) are intensively studied for their light-harvesting properties. Owing to the interplay between strong electron–electron interaction and spin-orbit coupling (SOC), their quantitative theoretical description is still a challenge as evidenced by the wide variety of results available in literature. Here, various methodologies for computing their electronic structure are evaluated, also accounting for SOC. More specific, the approach as well as variants of the hybrid functionals PBE0 and HSE are at the center of the investigations. For both functionals, methods to determine the mixing parameter α are explored, and for HSE, the impact of the screening-parameter ω is investigated. An extensive investigation of PbI2, a precursor of many HaPs, leads to the conclusion that hybrid functionals with α tuned by the density-based mixing method are most suitable for obtaining band gaps comparable toPeer Reviewe

Highly sensitive label-free in vitro detection of aflatoxin B1 in an aptamer assay using optical planar waveguide operating as a polarization interferometer

This work reports on further development of an optical biosensor for the in vitro detection of mycotoxins (in particular, aflatoxin B1) using a highly sensitive planar waveguide transducer in combination with a highly specific aptamer bioreceptor. This sensor is built on a SiO2–Si3N4–SiO2 optical planar waveguide (OPW) operating as a polarization interferometer (PI), which detects a phase shift between p- and s-components of polarized light propagating through the waveguide caused by the molecular adsorption. The refractive index sensitivity (RIS) of the recently upgraded PI experimental setup has been improved and reached values of around 9600 rad per refractive index unity (RIU), the highest RIS values reported, which enables the detection of low molecular weight analytes such as mycotoxins in very low concentrations. The biosensing tests yielded remarkable results for the detection of aflatoxin B1 in a wide range of concentrations from 1 pg/mL to 1 μg/mL in direct assay with specific DNA-based aptamers