Metal-Dielectric-Graphene Hybrid Heterostructures with Enhanced Surface Plasmon Resonance Sensitivity Based on Amplitude and Phase Measurements

Metal-dielectric-graphene hybrid heterostructures based on oxides Al2O3, HfO2, and ZrO2 as well as on complementary metal–oxide–semiconductor compatible dielectric Si3N4 covering plasmonic metals Cu and Ag have been fabricated and studied. We show that the characteristics of these heterostructures are important for surface plasmon resonance biosensing (such as minimum reflectivity, sharp phase changes, resonance full width at half minimum and resonance sensitivity to refractive index unit (RIU) changes) can be significantly improved by adding dielectric/graphene layers. We demonstrate maximum plasmon resonance spectral sensitivity of more than 30,000 nm/RIU for Cu/Al2O3 (ZrO2, Si3N4), Ag/Si3N4 bilayers and Cu/dielectric/graphene three-layers for near-infrared wavelengths. The sensitivities of the fabricated heterostructures were ~ 5–8 times higher than those of bare Cu or Ag thin films. We also found that the width of the plasmon resonance reflectivity curves can be reduced by adding dielectric/graphene layers. An unexpected blueshift of the plasmon resonance spectral position was observed after covering noble metals with high-index dielectric/graphene heterostructures. We suggest that the observed blueshift and a large enhancement of surface plasmon resonance sensitivity in metal-dielectric-graphene hybrid heterostructures are produced by stationary surface dipoles which generate a strong electric field concentrated at the very thin top dielectric/graphene layer.

The Combination of Low-Temperature Plasma and Tripterygium wilfordii Hook F on Ameliorating Imiquimod-Induced Psoriasiform Dermatitis in Mice

Improving the transdermal delivery efficiency of medicine is a crucial measure to improve the treatment efficiency of psoriasis. This paper developed a low-cost, highly active, and large-action-area low-temperature plasma (LTP) jet array. The two components of plasma—the high concentration of reactive oxygen and nitrogen species and the strong electric field—easily changed the structural integrity of the stratum corneum, which enhanced the transdermal delivery of the medicine. Tripterygium wilfordii Hook F (TwHF) is a medicine used to treat autoimmune and inflammatory conditions. The enhanced transdermal delivery of TwHF significantly alleviated the severed psoriasiform dermatitis induced by the imiquimod. Unlike the TwHF treatment alone, the LTP + TwHF treatment was more efficient at suppressing epidermal thickening and inhibiting systemic inflammation without noticeable side effects. LTP + TwHF treatment provides a potential new solution for psoriasis treatment.

Surface-Integrated Electric Field Sensor for the Detection of High-Voltage Power Lines

When a drone is used for inspection of facilities, there are often cases in which high-voltage power lines interfere, resulting in the drone being caught or falling. To prevent this type of incident, drones must be capable of detecting high-voltage power lines. Typically, a strong electric field is formed around the high-voltage lines. To detect the electric fields around high-voltage lines, this study proposes an electric field sensor that may be integrated within the body of a drone. In a laboratory environment, a voltage of 25 kV was applied to an overhead line, and the induced voltage in the proposed sensor was measured at various electric field intensities. Over an electric field range of 0.5 to 10.1 kV/m, a voltage of 0 to 0.77 V was measured with each proposed sensor. In addition, the electric field and the voltage induced in the sensor were measured in a real-world railway environment with overhead lines. Under these conditions, the proposed sensor has the compensated value of 4.5 when the measured electric field was 4.05 kV/m. Therefore, the proposed sensor may be applied in drones to measure large electric fields and to detect the presence of high-voltage lines in its vicinity.

Fine-scale dynamics of fragmented aurora-like emissions

Fragmented aurora-like emissions (FAEs) are small (few kilometres) optical structures which have been observed close to the poleward boundary of the aurora from the high-latitude location of Svalbard (magnetic latitude 75.3 ∘N). The FAEs are only visible in certain emissions, and their shape has no magnetic-field-aligned component, suggesting that they are not caused by energetic particle precipitation and are, therefore, not aurora in the normal sense of the word. The FAEs sometimes form wave-like structures parallel to an auroral arc, with regular spacing between each FAE. They drift at a constant speed and exhibit internal dynamics moving at a faster speed than the envelope structure. The formation mechanism of FAEs is currently unknown. We present an analysis of high-resolution optical observations of FAEs made during two separate events. Based on their appearance and dynamics, we make the assumption that the FAEs are a signature of a dispersive wave in the lower E-region ionosphere, co-located with enhanced electron and ion temperatures detected by incoherent scatter radar. Their drift speed (group speed) is found to be 580–700 m s−1, and the speed of their internal dynamics (phase speed) is found to be 2200–2500 m s−1, both for an assumed altitude of 100 km. The speeds are similar for both events which are observed during different auroral conditions. We consider two possible waves which could produce the FAEs, i.e. electrostatic ion cyclotron waves (EIC) and Farley–Buneman waves, and find that the observations could be consistent with either wave under certain assumptions. In the case of EIC waves, the FAEs must be located at an altitude above about 140 km, and our measured speeds scaled accordingly. In the case of Farley–Buneman waves a very strong electric field of about 365 mV m−1 is required to produce the observed speeds of the FAEs; such a strong electric field may be a requirement for FAEs to occur.

Study of conditions of gas- discharge synthesis of Zinc oxide nanostructures under automatic UV-irradiation of the substrate by plasma

The spectroscopic characteristics of a bipolar, overstressed discharge of nanosecond duration between zinc electrodes in oxygen at a pressure p(O2) = 13.3 kPa are presented. In the process of microexplosions of inhomogeneities on the working surfaces of the electrodes in a strong electric field, zinc vapor is introduced into the discharge gap. This creates the prerequisites for the formation of zinc oxide molecules and clusters in the plasma and the synthesis of thin island zinc oxide films, which can be deposited on a dielectric substrate installed near the center of the discharge gap. The spectral characteristics of the discharge were investigated from the central part of the discharge gap 2 mm in size. The main excited components of the plasma of a vapor-gas mixture based on zinc and oxygen were established at high values ​​of the parameter E / N (where E is the electric field strength; N is the total concentration of particles in the plasma), which, when deposited outside the discharge plasma, can lead to the formation of fine nanostructured films based on zinc oxide.

High-detectivity tin disulfide nanowire photodetectors with manipulation of localized ferroelectric polarization field

Tin sulfide semiconductor nanowires (NWs) have been widely investigated for photodetection applications because of their good optical and electrical properties. Herein, we synthesized n-type SnS2 NWs and then fabricated SnS2 NW photodetectors with a ferroelectric polymer side-gate. The strong electric field induced by ferroelectric polymer can effectively suppress the dark current and improve the detectivity in SnS2 NW photodetectors. The photodetectors after polarization depletion exhibit a high photoconductive gain of 4.0 × 105 and a high responsivity of 2.1 × 105 A W−1. Compared with devices without polarization depletion, the detectivity of polarization-depleted photodetectors is improved by at least two orders of magnitude, and the highest detectivity is 1.3 × 1016 Jones. Further, the rise and fall time are 56 and 91 ms respectively, which are about tens of times faster than those without polarization depletion. The device also shows a good spectral response from ultraviolet to near-infrared. This study demonstrates that ferroelectric materials can enhance optoelectronic properties of low-dimensional semiconductors for high-performance photodetectors.

Genetic Algorithm-Driven Surface-Enhanced Raman Spectroscopy Substrate Optimization

Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive and molecule-specific detection technique that uses surface plasmon resonances to enhance Raman scattering from analytes. In SERS system design, the substrates must have minimal or no background at the incident laser wavelength and large Raman signal enhancement via plasmonic confinement and grating modes over large areas (i.e., squared millimeters). These requirements impose many competing design constraints that make exhaustive parametric computational optimization of SERS substrates prohibitively time consuming. Here, we demonstrate a genetic-algorithm (GA)-based optimization method for SERS substrates to achieve strong electric field localization over wide areas for reconfigurable and programmable photonic SERS sensors. We analyzed the GA parameters and tuned them for SERS substrate optimization in detail. We experimentally validated the model results by fabricating the predicted nanostructures using electron beam lithography. The experimental Raman spectrum signal enhancements of the optimized SERS substrates validated the model predictions and enabled the generation of a detailed Raman profile of methylene blue fluorescence dye. The GA and its optimization shown here could pave the way for photonic chips and components with arbitrary design constraints, wavelength bands, and performance targets.

Characteristics and Parameters of Overstressed Nanosecond Discharge Plasma in Air between an Electrode from Aluminum and Electrode from Chalcopyrite (CuInSe2)

The characteristics and parameters of an overstressed high-current discharge with a duration of 100–150 ns in air, which was ignited between an aluminum electrode and a chalcopyrite electrode (CuInSe2), are presented. The air pressure was 13.3 and 101.3 kPa. In the process of microexplosions of inhomogeneities on the working surfaces of electrodes in a strong electric field, aluminum vapors and chalcopyrite vapors were introduced into the interelectrode gap, which creates the prerequisites for the synthesis of thin films based on quaternary chalcopyrite – CuAlInSe2. The films synthesized from the products of electrode destruction were deposited on a quartz plate at a distance of 2–3 cm from the center of the discharge gap. The current and voltage pulses across the discharge gap of d = 1 mm, as well as the pulse energy input into the discharge, were investigated. The plasma emission spectra were studied, which made it possible to establish the main decay products of the chalcopyrite molecule and the energy states of atoms and singly charged ions of aluminum, copper and indium, which are formed in the discharge. The reference spectral lines of atoms and ions of aluminum, copper, and indium were established, which can be used to control the process of deposition of thin films of quaternary chalcopyrite. Thin films were synthesized from the degradation products of chalcopyrite molecules and aluminum vapors, which may have the composition of the quaternary chalcopyrite CuAlInSe2; the transmission spectra of the synthesized films in the spectral range of 200–800 nm were studied. By the method of numerical simulation of the plasma parameters of an overstressed nanosecond discharge based on aluminum and chalcopyrite vapors in air by solving the Boltzmann kinetic equation for the electron energy distribution function, the temperature and density of electrons, the specific power losses of the discharge for the main electronic processes and their rate constants depending on the value parameter E/N for plasma of vapor-gas mixtures based on air, aluminum vapor and ternary chalcopyrite were modulated.

Long-Range Static and Dynamic Previtreous Effects in Supercooled Squalene—Impact of Strong Electric Field

This article presents evidence for the long-range previtreous changes of two static properties: the dielectric constant (ε) and its strong electric field related counterpart, the nonlinear dielectric effect (NDE). Important evidence is provided for the functional characterizations of ε(T) temperature changes by the ‘Mossotti Catastrophe’ formula, as well as for the NDE vs. T evolution by the relations resembling those developed for critical liquids. The analysis of the dynamic properties, based on the activation energy index, excluded the Vogel–Fulcher–Tammann (VFT) relation as a validated tool for portraying the evolution of the primary relaxation time. This result questions the commonly applied ‘Stickel operator’ routine as the most reliable tool for determining the dynamic crossover temperature. In particular, the strong electric field radically affects the distribution of the relaxation times, the form of the evolution of the primary relaxation time, and the fragility. The results obtained in this paper support the concept of a possible semi-continuous phase transition hidden below Tg. The studies were carried out in supercooled squalene, a material with an extremely low electric conductivity, a strongly elongated molecule, and which is vitally important for biology and medicine related issues.

Terahertz absorption characteristics of guar gum determined via microfluidic technology

The vibrational energy levels of many biomolecules correspond to the terahertz band; thus, terahertz technology can be used to identify these substances. Moreover, as the biological activity of most biomolecules can be observed only in aqueous solution, the characteristics of such biomolecules must be studied in aqueous solution. In this study, a simple microfluidic chip, a temperature control device and a strong electric field device were designed to study the terahertz absorption characteristics of guar gum for different temperatures, concentrations and electric field exposure durations, thus enabling the use of terahertz technology to analyse the characteristics of guar gum.