Electrostatic Image Research Articles

Linear and non-linear optical and dielectric properties of transition metals complexes films derived from Azo-Schiff base for photovoltaic applications

A novel azo-Schiff base, which incorporates a heterocyclic triazole nucleus known as 1H-1,2,4-triazol-5-yl)imino)methyl)-5-((2-nitrophenyl)diazenyl)phenol (H2ASB, 1), was formulated and synthesized. Furthermore, a series of Cu2+ complexes, derived from this azo-Schiff base, were prepared by a simple method with a molar ratio of 1 M Cu2+ to 1 M H2ASB. The synthesized compounds were thoroughly characterized using alternative analytical and spectral techniques. The obtained results confirmed that H2ASB bonded with the Cu2+ ions in a uni-negative/neutral bidentate manner, via the phenolic hydroxyl oxygen and azomethine nitrogen atom, thereby resulting in tetrahedral or octahedral geometries. Additionally, theoretical studies employing DFT/B3LYP/LanL2DZ were conducted, which included the assessment of global reactivity descriptors, dipole moment, molecular electrostatic potential image (MEP), optimized geometry, and the LUMO-HOMO energy gap to support the geometrical structure of the synthesized compounds. On the other side, the optical constants of H2ASB and its complexes have been studied over 300–1500 nm spectral range. The optical band gap (Eg) values of the present film's changes from 1.92 eV for H2ASB to 1.45 eV for CuHASB(5) film whereas the static index of refraction (n) takes a different behavior. The obtained values of n and Eg are the same as those recorded for many semiconductor materials. This means that, compared to the cost and ease of preparation, these films under study could replace many other semiconductors, such as CdTe with (Eg = 1.5 eV) which is the same value of CuHASB(4) film. With the help of n and extinction coefficient (k) values, the dielectric and non-linear optical parameters have been estimated and well discussed. Finally, the sheet resistance (Rs) and thermal emissivity (εth) changes due to the incident photon energy have been investigated. It was observed that, the change of Rs and εth with E is opposite to the change of other parameters such as the absorbance and optical conductivity.

Modelling of the Electrostatic Image in Films of Photosensitive Amorphous Molecular Semiconductors

Modelling of the Electrostatic Image in Films of Photosensitive Amorphous Molecular Semiconductors

Tutorial: Electrodynamic balance methods for single particle levitation and the physicochemical analysis of aerosol

Single particle levitation methods are a powerful subset of aerosol instrumentation that allow a wide range of particle properties and processes to be explored. One of the most common forms of single particle levitation uses electric fields and is generally referred to as an electrodynamic balance (EDB). There are many different kinds of EDB's that have been designed with different applications in mind, and a corresponding array of analytical tools have been developed to characterize particles held in these traps. In this tutorial, we review the design and development of the EDB and discuss a range of analytical methods, including electrostatic analysis, light scattering, spectroscopy, and imaging, that allow for measurements of hygroscopic growth, volatility, surface tension and viscosity, diffusion, and phase and morphology. We go on to review recent advanced analytical methods using mass spectrometry to probe particle composition. This review is intended to provide readers with the basic knowledge to set up an EDB platform, design measurement protocols based on the available analytical tools, and run experiments to probe the fundamental properties of aerosol particles relevant to their role in the atmosphere, impacts on clouds and climate, effects on air quality, role in health and disease, and applications in industrial processes.

A Field High Resolution Measurement Method for Irregular Surface Electrostatic Potential

Characterized by noninvasiveness and high sensitivity, the noncontact electrostatic testing technology has been widely used in scientific research and engineering practices such as electrostatic charge imaging, high-voltage insulator analysis, biological sensing, and gas—solid two-phase flow parameter measurement. However, in many practical applications, scanning electric potential microscope (SEPM) technologies focusing on high spatial resolution cannot meet the testing requirements of charged objects with irregular 3-D structures and flexible activities. Based on the principle of direct inductive electrostatic potential measurement and a six-axis robot arm, a 3-D scanning method for noncontact electrostatic potential measurement is proposed in this article. A low-noise electrostatic potential sensor with both high sensitivity and high accuracy was designed via positive feedback circuit technology. A calibration system was built, which has an adjustable excitation signal, progressive spatial accuracy, and variable 3-D attitude. The experimental data verify the effectiveness of this method. The correlation between the signal characteristics and the physical size of the calibration device was statistically analyzed. The effects of parameters such as the amplitude and frequency of the excitation signal, speed, and normal distance of the robot arm scanning on the resolution of the test results were investigated. The testing results show that the 3-D spatial resolution of dc and low-frequency ac potential distribution reached 200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> .

Adhesion forces of radioactive particles measured by the Aerodynamic Method–Validation with Atomic Force Microscopy and comparison with adhesion models

Median adhesion forces of tritiated tungsten micro-particles deposited on a glass substrate were successfully determined using an aerodynamic method (AM) which is presented in this paper. The original aerodynamic device built for these experiments has been carefully characterized in terms of friction velocities allowing to quantify aerodynamic torque exerted on the particles and to deduce median adhesion forces thanks to a force balance approach. Using the same particle/surface systems (non-radioactive tungsten particles in contact with a glass substrate), distribution of adhesion forces were obtained using AFM for comparison with the AM. The results show a good agreement between the two techniques which allowed to validate the AM. Furthermore, a precise description of the root-mean square roughness (rms) distribution of the glass substrate made it possible to compare the experimental results with different analytical adhesion force models. Integrating the rms roughness distribution of the substrate into the model of Rabinovich et al. showed the best agreement with the present experiments capturing most of the adhesion forces of 10µm to 18µm diameter tungsten particles. Moreover, the method developed in this work made it possible to show that the electrostatic image force arising from the self-charging of tritiated tungsten particles has a negligible contribution in the adhesion of the particles for the studied configuration.

Profiling and imaging of forensic evidence – A pan-European forensic round robin study part 1: Document forgery

The forensic scenario, on which the round robin study was based, simulated a suspected intentional manipulation of a real estate rental agreement consisting of a total of three pages. The aims of this study were to (i) establish the amount and reliability of information extractable from a single type of evidence and to (ii) provide suggestions on the most suitable combination of compatible techniques for a multi-modal imaging approach to forgery detection. To address these aims, seventeen laboratories from sixteen countries were invited to answer the following tasks questions: (i) which printing technique was used? (ii) were the three pages printed with the same printer? (iii) were the three pages made from the same paper? (iv) were the three pages originally stapled? (v) were the headings and signatures written with the same ink? and (vi) were headings and signatures of the same age on all pages? The methods used were classified into the following categories: Optical spectroscopy, including multispectral imaging, smartphone mapping, UV-luminescence and LIBS; Infrared spectroscopy, including Raman and FTIR (micro-)spectroscopy; X-ray spectroscopy, including SEM-EDX, PIXE and XPS; Mass spectrometry, including ICPMS, SIMS, MALDI and LDIMS; Electrostatic imaging, as well as non-imaging methods, such as non-multimodal visual inspection, (micro-)spectroscopy, physical testing and thin layer chromatography. The performance of the techniques was evaluated as the proportion of discriminated sample pairs to all possible sample pairs. For the undiscriminated sample pairs, a distinction was made between undecidability and false positive claims. It was found that none of the methods used were able to solve all tasks completely and/or correctly and that certain methods were a priori judged unsuitable by the laboratories for some tasks. Correct results were generally achieved for the discrimination of printer toners, whereas incorrect results in the discrimination of inks. For the discrimination of paper, solid state analytical methods proved to be superior to mass spectrometric methods. None of the participating laboratories deemed addressing ink age feasible. It was concluded that correct forensic statements can only be achieved by the complementary application of different methods and that the classical approach of round robin studies to send standardised subsamples to the participants is not feasible for a true multimodal approach if the techniques are not available at one location.

Charged Colloids at the Metal–Electrolyte Interface

We discuss the peculiarities of the structure of the interface between a metal and a stable colloidal dispersion of charged nanoparticles in an electrolyte. It is demonstrated that a quasi-2D ionic structure of elevated density arises in its vicinity due to the effect of electrostatic image forces. The stabilized colloidal particles, being electroneutral and spatially distributed objects in the bulk of the electrolyte and approaching the interface, are attracted to it. In their turn, the counterions forming their coat partially retract into the 2D-layer, which results in an acquisition by the colloidal particle of the effective charge eZ*≫e and which, together with its mirror image, creates the electric dipole. The formed dipoles, possessing the moments directed perpendicularly to the interface, form the gas with repulsion between particles. The intensity of this repulsion, evidently, depends on the value of the effective charge eZ* acquired by the nanoparticle having lost a number of counterions. It can be related to the value of the excess osmotic pressure Posm measured in the experiment. On the other hand, this effective charge can be connected by means of the simple geometric consideration with the structural charge eZ of the nanoparticle core being in the bulk of the electrolyte.

An integrated system for automated measurement of airborne pollen based on electrostatic enrichment and image analysis with machine vision

Here we describe an automated and compact pollen detection system that integrates enrichment, in-situ detection and self-cleaning modules. The system can achieve continuous capture and enrichment of pollen grains in air samples by electrostatic adsorption. The captured pollen grains are imaged with a digital camera, and an automated image analysis based on machine vision is performed, which enables a quantification of the number of pollen particles as well as a preliminary classification into two types of pollen grains. In order to optimize and evaluate the system performance, we developed a testing approach that utilizes an airflow containing a precisely metered amount of pollen particles surrounded by a sheath flow to achieve the generation and lossless transmission of standard gas samples. We studied various factors affecting the pollen capture efficiency, including the applied voltage, air flow rate and humidity. Under optimized conditions, the system was successfully used in the measurement of airborne pollen particles within a wide range of concentrations, spanning 3 orders of magnitude.

Real-time imaging of atomic electrostatic potentials in 2D materials with 30 keV electrons

Scanning transmission electron microscopy (STEM) is the most widespread adopted tool for atomic scale characterization of two-dimensional (2D) materials. Many 2D materials remain susceptible to electron beam damage, despite the standardized practice to reduce the beam energy from 200 keV to 80 or 60 keV. Although, all elements present can be detected by atomic electrostatic potential imaging using integrated differential phase contrast (iDPC) STEM or electron ptychography, capturing dynamics with atomic resolution and enhanced sensitivity has remained a challenge. Here, by using iDPC-STEM, we capture defect dynamics in 2D WS$_2$ by atomic electrostatic potential imaging with a beam energy of only 30 keV. The direct imaging of atomic electrostatic potentials with high framerate reveals the presence and motion of single atoms near defects and edges in WS$_2$ that are otherwise invisible with conventional annular dark-field STEM or cannot be captured sufficiently fast by electron ptychography.

Structure investigation, density functional theory, and biostudy of synthesized dihydrazone incorporating isatin moiety and its homo‐bimetallic complexes

AbstractSeven homo‐bimetallic complexes derived from 3‐(‐(1,5‐dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)methylene)hydrazono)indolin‐2‐one with Fe3+, Co2+, Cu2+, and UO22+have been prepared and structurally investigated using elemental and thermo‐gravimetric analyses and spectral, magnetic, and molar conductivity measurements. This structural investigation leads us to conclude that the bis‐hydrazone has behaved as neutral tetradentate chelator chelated to the Fe3+, Co2+, Cu2+, and UO22+ions via the carbonyl and azomethine groups adopting distorted octahedral structure for Fe3+, Co2+, and Cu2+complexes (2–5), whereas the Cu2+complexes (6–7) have square planar structures. The structural characterization of bis‐hydrazone and its chelated compounds has been supported by density functional theory calculations. The optimized geometry, global reactivity descriptors, and lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the molecules have been calculated in accordance with the density functional theory (DFT)‐Beckee3eLeeeYangeParr (B3LYP) technique and 6e311G(d,p) basis set. The molecular electrostatic potential image was also drawn by the DFT‐B3LYP technique and 6e311G(d,p) basis set to envision the charge distribution and chemical reactivity on the molecules. The bioeffect of bis‐hydrazone and its chelated compounds was assessed against bacterial strainsBacillus subtilis,Escherichia coli, as well as fungal strainsCanadian albicansandAspergillus niger. The observed data imply encouraging bioeffect of some of these complexes in comparing with the free bis‐hydrazone or amphotericin B (AmB) against all fungalC. albicansandA. niger.

Electrostatic image force energy for charges in three-layer structures: exact formulas and their approximations

The problem of image force energy W(Z) in three-layer plane structures, where Z is the coordinate perpendicular to the layers, has been reconsidered. In the classical electrostatic limit, where the dielectric permittivities ɛ i of all structure components (i = 1, 2, 3) are constants, the exact general dependences W(Z) were obtained for each layer and any ɛ i -combination in terms of the Lerch transcendent function. For certain combinations of ɛ i , an ion adsorption minimum was found to arise in one of the covers far from the interlayer. Some other combinations of ɛ i can lead to the appearance of a potential barrier, which does not permit a free charge existing in the cover to approach the interlayer, although it will be attracted to the interlayer in the close vicinity of the latter. For symmetric structures (ɛ 1 = ɛ 3), the asymptotic behavior of was shown to be rather than , as it takes place in the two-layer case. Simple approximate analytical formulas that describe W(Z) and possess high accuracy for arbitrary relationships among the ɛ i -constants were proposed.

Design and Characterisation of a Non-Contact Flexible Sensor Array for Electric Potential Imaging Applications

Capacitive non-contact imaging of electric fields and potentials with micro-metre resolution can provide relevant insights into material characterisation, structural analysis, electrostatic charge imaging and bio-sensing applications. However, scanning electric potential microscopes have been confined to rigid and single-probe devices, making them slow, prone to mechanical damage and complex to fabricate. In this work, we present the design and characterisation of a novel 5-element flexible array of electric potential probes with spatial resolution down to 20μm to speed up the scanning time. This was achieved by combining flexible thin-film probes for active guarding and shielding with state-of-the art discrete conditioning circuits. The potential of this approach is showcased by using the fabricated array to image latent fingerprints deposited on an insulating surface by contact electrification, obtain the surface topography of conductive samples and to visualise local dielectric variations.

Propagator for a driven Brownian particle in step potentials

Although driven Brownian particles are ubiquitous in stochastic dynamics and often serve as paradigmatic model systems for many aspects of stochastic thermodynamics, fully analytically solvable models are few and far between. In this paper, we introduce an iterative calculation scheme, similar to the method of images in electrostatics, that enables one to obtain the propagator if the potential consists of a finite number of steps. For the special case of a single potential step, this method converges after one iteration, thus providing an expression for the propagator in closed form. In all other cases, the iteration results in an approximation that holds for times smaller than some characteristic timescale that depends on the number of iterations performed. This method can also be applied to a related class of systems like Brownian ratchets, which do not formally contain step potentials in their definition, but impose the same kind of boundary conditions that are caused by potential steps.

Imaging atomic motion of light elements in 2D materials with 30 kV electron microscopy.

Scanning transmission electron microscopy (STEM) is the most widespread adopted tool for atomic scale characterization of two-dimensional (2D) materials. However, damage free imaging of 2D materials with electrons has remained problematic even with powerful low-voltage 60 kV-microscopes. An additional challenge is the observation of light elements in combination with heavy elements, particularly when recording fast dynamical phenomena. Here, we demonstrate that 2D WS2 suffers from electron radiation damage during 30 kV-STEM imaging, and we capture beam-induced defect dynamics in real-time by atomic electrostatic potential imaging using integrated differential phase contrast (iDPC)-STEM. The fast imaging of atomic electrostatic potentials with iDPC-STEM reveals the presence and motion of single sulfur atoms near defects and edges in WS2 that are otherwise invisible at the same imaging dose at 30 kV with conventional annular dark-field STEM, and has a vast speed and data processing advantage over electron detector camera based STEM techniques like electron ptychography.

Experimental Investigations Into Bubble Characteristics in a Fluidized Bed Through Electrostatic Imaging

Fluidized beds are widely applied in many industrial processes. In order to control and optimize the operation of a fluidized bed, it is necessary to develop reliable methods for the measurement of bubble characteristics to monitor the status of the bed. Electrostatic sensing methods based on the detection of charges on particles have been applied to characterize the particle motion in a fluidized bed. However, there is limited research on the measurement of bubble characteristics using the electrostatic methods due to complex electrostatic phenomena around the bubbles. In this article, an imaging method using a two-dimensional electrostatic sensor array is employed for the experimental investigations into the bubble behaviors in a two-dimensional fluidized bed. The bubble size, shape, rising velocity, and generation frequency are measured. Moreover, an optical imaging system is employed to obtain reference information to evaluate the performance of the electrostatic imaging method. Experimental results show that the bubble characteristics measured from the electrostatic sensor array have a good agreement with the results from the optical imaging system. The relative root mean square error between the bubble shapes measured from the electrostatic sensor array and from the optical system is 0.239 with a standard deviation within 4.7%.

Orientation of adsorbed polar molecules (dipoles) in external electrostatic field

A model is proposed in the framework of classical electrostatics to describe the behavior of an adsorbed polar molecule near the plane interface between two insulators under the action of an external electrostatic field. The molecule is considered as a permanent point dipole that polarizes the interface and interacts with it through electrostatic image forces. The latter and the applied field try to reorient the dipole in a competitive manner. The system behavior turns out to be rather complicated: it may show a bistable character with a hysteresis (a switch). Such a switch can serve as an element in a memory network made of adsorbed molecules.

Molecular structure elucidation, charge transfer interactions, electronic properties, vibrational spectral investigation and molecular docking of the antiviral active molecule (E)-4-[1-(2-carbamothioylhydrazinylidene)ethyl]-phenyl benzoate dimer - aided by density functional theory

The molecular structure of the novel thiosemicarbazide (E)-4-[1-(2-carbamothioylhydrazinylidene) ethyl] - phenyl benzoate has been synthesized and subjected to Raman and Fourier transform infrared spectral studies. Optimized parameters of (E)-4-[1-(2-carbamothioylhydrazinylidene) ethyl] - phenyl benzoate monomer and dimer have been compared with X-ray diffraction data. The existence of hydrogen bonded intramolecular interactions, intermolecular interactions and the hyperconjugative energy leading to the stabilization of the system have been revealed by natural bond orbital analysis. Charge transfer interactions from highest occupied molecular orbital to lowest unoccupied molecular orbital and the observed low energy gap predict the molecule to be more reactive. Molecular electrostatic potential image shows the potential binding site is around the sulfur atom. The spectra have been analyzed and the assignments of the normal modes of vibrations have been carried out with the help of normal coordinate analysis following the scaled quantum chemical force field methodology. The observed spectral shift substantiates the spectral evidence of the intermolecular hydrogen bonding. Molecular docking scores reveal good binding affinity and the inhibition activity of the molecule against dengue viral protein 4c11.

Mobility-Fluctuation-Controlled Linear Positive Magnetoresistance in 2D Semiconductor Bi2O2Se Nanoplates.

Linear magnetoresistance is generally observed in polycrystalline zero-gap semimetals and polycrystalline Dirac semimetals with ultrahigh carrier mobility. We report the observation of positive and linear magnetoresistance in a single-crystalline semiconductor Bi2O2Se grown by chemical vapor deposition. Both Se-poor and Se-rich Bi2O2Se single-crystalline nanoplates display a linear magnetoresistance at high fields. The Se-poor Bi2O2Se exhibits a typical 2D conduction feature with a small effective mass of 0.032m0. The average transport Hall mobility, which is lower than 5500 cm2 V-1 s-1, is significantly reduced, compared with the ultrahigh quantum mobility as high as 16260 cm2 V-1 s-1. More interestingly, the pronounced Shubnikov-de Hass oscillations can be clearly observed from the very large and nearly linear magnetoresistance (>500% at 14 T and 2 K) in Se-poor Bi2O2Se. A close analysis of the results reveals that the large and linear magnetoresistance observed can be ascribed to the spatial mobility fluctuation, which is strongly supported by Fermi energy inhomogeneity in the nanoplate samples detected using an electrostatic force microscopy images and multiple frequencies in a Shubnikov-de Hass oscillation. On the contrary, the Se-rich Bi2O2Se exhibits a transport mobility (<300 cm2 V-1 s-1) much smaller than that observed in Se-poor samples and shows a much smaller linear magnetoresistance ratio (less than 150% at 14 T and 2 K). More strikingly, no Shubnikov-de Hass oscillations can be observed. Therefore, the linear magnetoresistance in Se-rich Bi2O2Se is governed by the average mobility rather than the mobility fluctuation.

Corrosion shape reconstruction of the mixed boundary in electrostatic imaging

We consider the corrosion detection problem in terms of the Laplace equation and study a simply connected bounded domain with Wentzell-type GIBC boundary condition. We derive the systems of integral equations and establish the equivalence to the inverse shape problem in a Sobolev space setting. For the direct problem, we use potential theory to simulate the Neumann data from Dirichlet data on Dirichlet boundary. Then we propose a Newton iterative approach based on the boundary integral equations derived from Green’s representation theorem. After describing the linearization and the iteration scheme for the inverse shape, we compute the Fréchet derivatives with respect to the unknowns. We conclude by presenting several numerical examples for shape reconstructions to show the validity of the proposed method.

Electrostatic potential imaging of phase-separated structures in organic materials via differential phase contrast scanning transmission electron microscopy.

Electron staining is generally performed prior to observing organic materials via transmission electron microscopy (TEM) to enhance image contrast. However, electron staining can deteriorate organic materials. Here, we demonstrate electrostatic potential imaging of organic materials via differential phase contrast (DPC) scanning transmission electron microscopy (STEM) without electron staining. Electrostatic potential imaging drastically increases the contrast between different materials. Phase-separated structures in a poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend that are impossible to observe using conventional STEM are clearly visualized. Furthermore, annealing behavior of the phase-separated structures is directly observed. The morphological transformations in the samples are consistent with their physical parameters, including their glass transition and melting temperatures. Our results indicate that electrostatic potential imaging is highly effective for observing organic materials.