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The synthesis of nanosized organic benzil (C6H5CO)2 crystals within the mesoporous SiO2 host matrix was investigated via X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and ab initio lattice dynamics analysis. Combining these methods, we have proved that the main structural properties of benzil nanocrystals embedded into SiO2 host membranes with pore diameters of 6.0, 7.8, 9.4, and 13.0 nm are preserved compared to a bulk benzil crystal. Space confinement has an insignificant impact on the lattice vibrational properties of benzil crystals implanted into the host matrices. The ab initio lattice dynamics calculation of the phonon spectrum in the Brillouin zone center shows the mechanical and dynamical stability of benzil lattice, revealing very low optical frequency of 11 cm−1 at point Γ.

The designed flexible lead-free Cs3Cu2X5 (X = Cl, Br, I) nanocrystal perovskite photodetectors demonstrate excellent properties, including high photoresponses, strong photoselectivity and bending stability at different irradiation wavelengths.

In this work, we have investigated the features of electron transport in AlGaN/GaN transistor-like heterostructures with nanowires of different width. These nanostructures are studied extensively because of their great electronic and sensing advantages for electronic biosensor applications. We study the depletion effects and impact of ultraviolet excitation on the electron transport in sets of nanowires of different width from 1110 down to 185 nm. We have found significant difference in electrical characteristic’s behavior between wide (1110…480 nm) and narrow (280…185 nm) nanowires and have observed regions related to space-charge-limited transport for the narrowest nanowires. Also, we obtained evident dependence of nanowire’s current-voltage characteristics on the wavelength and energy of UV excitation. External UV excitation allows us to control the depletion widths in nanowires and effectively tune space-charge-limited transport.

Amino acids play essential role for humans. We studied the dielectric properties of the basic aliphatic amino acids and polar positive amino acids in solutions of different concentrations. The high-Q single microwave whispering gallery-mode (WGM) quartz dielectric resonator based technique, enhanced to a number of measurement frequencies, was applied. The technique allows liquid investigation of micro- to nano- liter volumes filled in microfluidic channel on six discrete frequencies in the 30–40 GHz range. The dependencies of the complex permittivity on the molar mass show almost linear behavior for aliphatic amino acids at different concentrations. The study results are in good agreement with the calculated data obtained by Cole-Cole equation.

pH sensors, with high sensitivity, durability, and low cost, are considered to be essential tools in several applications such as laboratory experiments, water quality, agriculture, and healthcare....

The lattice dynamics of preferentially aligned nanocrystals formed upon drying of aqueous Ba(NO

The lattice dynamics of preferentially aligned nanocrystals formed upon drying of aqueous Ba(NO$_3$)$_2$ solutions in a mesoporous silica glass traversed by tubular pores of approximately 12 nm are explored by Raman scattering. To interpret the experiments on the confined nanocrystals polarized Raman spectra of bulk single crystals and X-ray diffraction experiments are also performed. Since a cubic symmetry is inherent to Ba(NO$_3$)$_2$, a special Raman scattering geometry was utilized to separate the phonon modes of A$_g$ and E$_g$ species. Combining group-theory analysis and \textit{ab initio} lattice dynamics calculations a full interpretation of all Raman lines of the bulk single crystal is achieved. Apart from a small confinement-induced line broadening, the peak positions and normalized peak intensities of the Raman spectra of the nanoconfined and macroscopic crystals are identical. Interestingly, the Raman scattering experiment indicates the existence of comparatively large, $\sim$10-20 $\mu$m, single-crystalline regions of Ba(NO$_3$)$_2$ embedded in the porous host, near three orders of magnitude larger than the average size of single nanopores. This is contrast to the initial assumption of non-interconnected pores. It rather indicates an inter-pore propagation of the crystallization front, presumably via microporosity in the pore walls., Comment: 12 pages, 9 figures, as submitted

Studies of biological solutions require high measurement accuracy, the ability to detect low changes in substance concentration, and small amounts of the liquid under test. A microwave complex permittivity measurement technique based on a high-quality-factor whispering-gallery-mode resonator with a microfluidic chip allows small amounts of dielectric liquids to be investigated with high accuracy. An existing technique based on a sapphire resonator does not provide for a low-concentration detection limit for substances with low molecular weight. Here, we present an advanced technique based on a quartz dielectric resonator. The detection limit obtained for glucose in water solution was found to be about one order of magnitude lower for the quartz resonator cell than for the sapphire-resonator-based measurement cell. The limit is about or lower than the concentration of glucose in human blood. This fact means that the technique can be used as the sensor for investigations of biological solutions in the microwave range. A study of glucose, lactalbumin, and bovine serum albumin was successfully performed in the $Ka$ -band using the developed sensor.

The combination of graphene and silicon in hybrid electronic devices has attracted increasing attention over the last decade. Here, a unique technology of graphene-on-silicon heterostructures as solution-gated transistors for bioelectronics applications is presented. The proposed graphene-onsilicon field-effect transistors (GoSFETs) are fabricated by exploiting various conformations of channel doping and dimensions. The fabricated devices demonstrate hybrid behavior with features specific to both graphene and silicon, which are rationalized via a comprehensive physics-based compact model which is purposely implemented and validated against measured data. The developed theory corroborates that the device hybrid behavior can be explained in terms of two independent silicon and graphene carrier transport channels, which are, however, strongly electrostatically coupled. Although GoSFET transconductance and carrier mobility are found to be lower than in conventional silicon or graphene field-effect transistors, it is observed that the combination of both materials within the hybrid channel contributes uniquely to the electrical response. Specifically, it is found that the graphene sheet acts as a shield for the silicon channel, giving rise to a nonuniform potential distribution along it, which impacts the transport, especially at the subthreshold region, due to non-negligible diffusion current., MCIN/AEI PID2020-116518GB-I00, FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades A-TIC-646-UGR20 B-RNM-375-UGR18 PY20_00633, European Commission 825213, PAIDI 2020, European Social Fund Operational Programme 2014-2020 20804, MCIN/AEI/PTA grant PTA2020-018250-I, Projekt DEAL

This paper presents the results of the investigation of stress relaxation at the Si-SiO2 interface using electron paramagnetic resonance (EPR) spectra, scanning electron microscopy (SEM) image technique, deflection analysis, X-ray photoelectron spectroscopy (XPS) and C-V characterisation of metal oxide semiconductor (MOS) structures. It has been shown, on the basis of EPR, XPS, C-V, and deflection data, that the mechanism of stress relaxation depends on the oxidation conditions: temperature, cooling rate and oxide thickness. In the Si-SiO2-Si3N4 system the stress relaxation occurs due to the difference in the thermal expansion coefficient of SiO2 and Si3N4 material. With an appropriate choice of oxidation conditions compressive stresses in SiO2 and tensile stresses in Si are almost equal and stress can be reduced considerably at the interface.

C-reactive protein (CRP) and cardiac troponin I (cTnI) biomolecules represent the earliest enzymes that appear in the blood when a cardiac injury occurs. Real-time and selective detection of these biomarkers is essential for the prediction and detection of cardiovascular diseases at an early stage. Here we report on the label-free specific detection of both proteins at picomolar concentrations using fabricated nanowire-based biosensors. We demonstrate a novel functionalization technique based on the attachment of dibenzocyclooctyne (DBCO)- linked troponin-specific aptamers to azide-functionalized silicon (Si) nanowire (NW) surface. Due to the fast and reliable immobilization of cTnI-specific aptamers and CRP-specific antibodies on the Si NWs, the fabricated devices can rapidly detect target biomolecules demonstrating high sensitivity. We confirm the attachment of proteins to the surface of Si NWs by atomic force microscopy (AFM). Moreover, we demonstrate that nanowire structures of different sizes enable the detection of biomarkers in a wide concentration range (from 1 pg/ml to 1 mg/ml), corresponding to CRP and cTnI elevation levels during the early stage of disease formation.

The characteristics of photocurrent are investigated in new nanocomposites of cadmium octanoate with semiconductor nanoparticles (NPs) as well as in pure matrix of the cadmium octanoate. CdS NPs are synthesized inside the cadmium octanoate matrix during one-step chemical reaction. The photoconductivity in these nanocomposites has been detected in wide temperature range. The photocurrent exhibits nonlinear behavior over all different mesophases of the nanocomposites. Two types of near-electrode processes that occur depending on the value of applied voltage are considered to explain the nonlinear dependence of the current-voltage characteristics.

In small-area transistors, the trapping/detrapping of charge carriers to/from a single trap located in the gate oxide near the Si/SiO2 interface leads to the discrete switching of the transistor drain current, known as single-trap phenomena (STP), resulting in random telegraph signals. Utilizing the STP-approach, liquid-gated (LG) nanowire (NW) field-effect transistor biosensors have recently been proposed for ultimate biosensing with enhanced sensitivity. In this study, the impact of channel doping concen-tration on the capture process of charge carriers by a single trap in LG silicon NW structures is investigated. A significant effect of the channel doping concentration on the single-trap dynamic is revealed. To under-stand the mechanism behind unusual capture time behavior compared to that predicted by the classical Shockley–Read–Hall theory, an analytical model based on the rigorous description of the additional energy barrier that charge carriers have to overcome to be captured by the trap at dif-ferent gate voltages is developed. The enhancement of the sensitivity for single-trap phenomena biosensing with an increase of the channel doping concentration is explained within the framework of the proposed analytical model. The results open prospects for the development of advanced single trap-based devices.

We study the liquid crystalline phase behaviour of the two-component aqueous colloidal suspensions of multiwalled carbon nanotubes (MWCNTs) and rod-like vanadium pentoxide (V2O5) nanoparticles. The phase diagram features a stable nematic phase in a wide range of concentration of solid components. The oriented nematic phase of the two-component suspension was exposed to the action of alternating current electric field. A variation in MWCNTs concentration within 0.01���0.51 wt.% demonstrates a significant increase in the optical response of the system to the applied electric field.

The detection of cardiac biomolecules is of paramount importance for the prospects of fast medical diagnostics of cardiovascular diseases. Silicon nanowire field-effect transistors (NW FETs) are perfect candidates for (bio)sensing studies due to their tremendous sensitivity to changes in surface charge. We present the results of an investigation of transport, fluctuation and modulation phenomena with certain characteristic times in n+-p-n+ liquid-gated field-effect transistors (FETs) and compare them with those of p+-p-p+ structures. We reveal the gate coupling effect to be a tool for influencing the channel noise mechanism. n+-p-n+ liquid-gated FETs demonstrate higher signal-to-noise ratios (SNRs) compared to p+-p-p+ structures. We show the results of the influence of light waves on the electrical properties of NW FET structures and of studying modulation phenomena in these structures. Excitation of NW samples by light waves allows the effective control of conductance in nanowire channels. Noise spectra and time-dependent modulations of the drain current show promising prospects for enhancing the sensitivity and SNR of nanowire biosensors. The direct translation of periodical signals at a frequency around 1 kHz from the biological object into surface potential changes, caused by interaction with cardiac cells, enables the highly sensitive monitoring of cell dynamic activity before and after pharmacological treatments. Electrical properties of the fabricated Si NW FETs demonstrate high sensitivity for the detection of human C-reactive protein (CRP) – a biomolecule which has recently emerged as a reliable biomarker used in clinical practice for predicting and tracking the state of cardiovascular diseases. The response of the sensor to different concentrations of target CRP molecules, which represent predictable cardio-biomarkers, is studied. Moreover, we reveal that the periodical modulation of drain current due to the single-trap effect may be used to achieve enhanced sensitivity of biosensors. The results are promising for cost-efficient lab-on-chip monitoring, which is especially necessary in the case of acute cardiovascular diseases, where every minute is critical for saving life.

Transistor biosensors are mass-fabrication-compatible devices of interest for point of care diagnosis as well as molecular interaction studies. While the actual transistor gates in processors reach the sub-10 nm range for optimum integration and power consumption, studies on design rules for the signal-to-noise ratio (S/N) optimization in transistor-based biosensors have been so far restricted to 1 µm2 device gate area, a range where the discrete nature of the defects can be neglected. In this study, which combines experiments and theoretical analysis at both numerical and analytical levels, we extend such investigation to the nanometer range and highlight the effect of doping type as well as the noise suppression opportunities offered at this scale. In particular, we show that, when a single trap is active near the conductive channel, the noise can be suppressed even beyond the thermal limit by monitoring the trap occupancy probability in an approach analog to the stochastic resonance effect used in biological systems.

Prepared nanoporous structures of anodized aluminum oxide Al2O3 (AOA) with a pore diameter of 40 and 75 nm. The crystal material KH2PO4 (KDP) in the form of nanowires and nanotubes at different growth variants from aqueous solution on nanoporous Al2O3 matrices was obtained and studied.

New highly sensitive direct methods for the early detection of peptides involved in Alzheimer's disease (AD) are required in order to prolong effective and healthy memory and thinking capabilities and also to stop the factors resulting in AD. In this contribution, we report the successful demonstration of a label-free approach for the detection of amyloid-beta (Aβ) peptides by highly selective aptamers immobilized onto the SiO2 surface of the fabricated sensors. A modified single-stranded deoxyribonucleic acid (ssDNA) aptamer was specially designed and synthesized to detect the target amyloid beta-40 sequence (Aβ-40). Electrolyte–insulator–semiconductor (EIS) structures as well as silicon (Si) nanowire (NW) field-effect transistors (FETs) covered with a thin SiO2 dielectric layer have been successfully functionalized with Aβ-40-specific aptamers and used to detect ultra-low concentrations of the target peptide. The binding of amyloid-beta peptides of different concentrations to the surface of the sensors varied in the range from 0.1 pg/ml to 10 μg/ml resulting in a change of the surface potential was registered by the fabricated devices. Moreover, we show that the single-trap phenomena observed in the novel Si two-layer (TL) NW FET structures with advanced characteristic parameters can be effectively used to increase the sensitivity of nanoscale sensors. The obtained experimental data demonstrate a highly sensitive and reliable detection of ultra-low concentrations of the Aβ-40 peptides. This opens up prospects for the development of real-time electrical biosensors for studying and understanding different stages of AD by utilizing Si TL NW FET structures fabricated on the basis of cost-efficient CMOS-compatible technology.

Numerous sensitive nanobiosensors are reported for various bioassay applications as a result of the development of materials science and nanotechnology. Among these sensors, nanowire (NW) field‐effect transistors (FETs) represent one of the most promising practical biosensors for ultrasensitive clinical diagnostic tools. Most studies mainly focus on how to achieve a lower detection limit but pay less attention to the long settling time effect for the detection of very small concentrations of molecules in a solution. In this study, single silicon NW FETs with long‐term stability is fabricated to investigate the settling time process at small concentrations of cardiac biomarkers relevant to myocardial diseases. It is found that the settling time strongly depends on the type of molecule, its charge state and analyte concentrations. For low concentrations, the time for measurement signals to settle down is relatively long. Therefore, it is essential to understand the settling time effect in Si NW FET‐based biosensing processes to ensure the accuracy and reliability of the detection signal. An alternative approach is demonstrated to circumvent the long measurement time by utilizing reaction kinetics parameters for the fast determination of low‐concentration detection, which also benefits the optimal balance between suitable detection time and reliable detection results.

The paper reports the results on first-principles investigation of energy band spectrum and optical properties of bulk and nanoporous silicon. We present the evolution of energy band-gap, refractive indices and extinction coefficients going from the bulk Si of cubic symmetry to porous Si with periodically ordered square-shaped pores of 7.34, 11.26 and 15.40 &Aring, width. We consider two natural processes observed in practice, the hydroxylation of Si pores (introduction of OH groups into pores) and the penetration of water molecules into Si pores, as well as their impact on the electronic spectrum and optical properties of Si superstructures. The penetration of OH groups into the pores of the smallest 7.34 &Aring, width causes a disintegration of hydroxyl groups and forms non-bonded protons which might be a reason for proton conductivity of porous Si. The porosity of silicon increases the extinction coefficient, k, in the visible range of the spectrum. The water structuring in pores of various diameters is analysed in detail. By using the bond valence sum approach we demonstrate that the types and geometry of most of hydrogen bonds created within the pores manifest a structural evolution from distorted hydrogen bonds inherent to small pores (&sim, 7 &Aring, ) to typical hydrogen bonds observed by us in larger pores (&sim, 15 &Aring, ) which are consistent with those observed in a wide database of inorganic crystals.

The response of sapphire WGM resonator to a single-layer graphene introduced onto the dielectric substrate is studied in Ka-band. The experimental investigations were performed for two types of resonator modes: HE and EH. The modes differ by the prevailing component: electric or magnetic of electromagnetic field along the resonator longitudinal axis. The possibility of using these modes for finding graphene conductivity is demonstrated. Based on the experimental and the resonator model data obtained using COMSOL Multiphysics software the graphene conductivity values were obtained. The conductivity values calculated based on results of measurements performed on two mode types with different substrate position relative to the resonator are compared. The results demonstrate reproducibility. The possible source of some difference between the results obtained on different modes is discussed. The recommendations regarding the design of the most suitable configuration for graphene conductivity measurements are proposed.

In this work, we report on fabrication of the thin-films of silicon oxide dielectric layers on silicon with back-side contact and utilization of the structure to study the detection of human Troponin antigen (cTnI) molecules: the cardiac biomarkers for the early diagnosis of acute myocardial infraction. Aptamers are selectively bound to the target molecules and can block the binding epitope for further reaction like immobilization or interaction to any other molecules. In contrast to antibodies, the aptamers are smaller in size, which allows target molecules to be brought closer to the surface of the biosensor and, therefore, to enhance the molecular signal. The target molecule in this work is cTnI, which is located in the cardiac muscle tissue. As a reliable indicator of heart failure and injury, it is specifically considered for the diagnosis of myocardial infarctions. The solutions of Troponin molecules were studied in different concentrations range from 10 pg/mL to 1 ng/mL. For the electrical detection of cTnI, we used the field-effect capacitive electrolyte-insulator-semiconductor (EIS) technique, which is a robust method for the quantitative characterization of molecular layers. The measured values of capacitances and flat band voltages were used to acquire information about the properties of the molecular layers obtained using solutions with different troponin concentrations. It was shown that this method demonstrates high sensitivity to target cardiac biomolecules and opens up new perspectives for highly selective and sensitive cardiac biosensors developed on the basis of silicon nanowire structures.

We analyze the experimental data on the evolution of the microwave (MW) response of the whispering gallery mode (WGM) resonator. The focus is on the thickness $d_{f}$ variation of the conducting endplates (CEPs) from $d_{f}$ exceeding skin layer thickness $\delta _{s}$ to $d_{f}\ll \delta _{s}$ down to $d_{f} = 0$ , i.e., with no CEPs. The analysis was performed by comparing the numerical simulation results obtained using COMSOL software with the authors’ experimental data on the response of the Ka -band sapphire WGM resonator. The nonmonotonic change in the WGM resonator response with decreasing thickness $d_{f}$ is explained using the metal–insulator percolation model proposed by Krupka et al. We use a different resonator (quasi-optical) technique and different mode polarization, namely, the HE $_{14~1~\delta }$ mode. The artificially introduced discontinuity of the ultrathin film, resulting in a sharp growth of the ${Q}$ -factor is analogous with the percolation material structure. The revealed effect may be useful for the development of MW devices with dynamically controlled properties of metamaterials.

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC8) and of the cobalt octanoate (CoC8). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.

We present several recently synthesized nanocomposites consisting of liquid crystals as well as an organic molecular crystal embedded into the nanochannels of mesoporous alumina and silica. As liquid-crystalline mesogens achiral, nematogen and chiral cholesteric guest molecules infiltrated into nanochannels by spontaneous imbibition were chosen. The molecular ordering inside the nanochannels, which can be tailored by modifying the surface anchoring, was characterized by optical polarimetry (linear and/or circular birefringence) in combination with X-ray diffraction. For the synthesis of the solid crystalline nanocomposites ferroelectric triglycine sulfate (TGS) nanocrystals were deposited into the nanochannels by slow evaporation of saturated water solutions imbibed into the porous hosts. Their textural and physicochemical properties were explored by x-ray diffraction, scanning electron microscopy and dielectric techniques., 4 pages, 2 figures, 21st International Conference on Transparent Optical Networks (ICTON), 9-13 July 2019 Angers, France

Silicon nanowires (Si NWs) are the most promising candidates for recording biological signals due to improved interfacing properties with cells and the possibility of high-speed transduction of biochemical signals into detectable electrical responses. The recording of extracellular action potentials (APs) from cardiac cells is important for fundamental studies of AP propagation features reflecting cell activity and the influence of pharmacological substances on the signal. We applied a novel approach of using fabricated Si NW field-effect transistors (FETs) in combination with fluorescent marker techniques to evaluate the functional activity of cardiac cells. Extracellular AP signal recording from HL-1 cardiomyocytes was demonstrated. This method was supplemented by studies of the pharmacological effects of stimulations using noradrenaline (NorA) as a modulator of functional activity on a cellular and subcellular levels, which were also tested using fluorescent marker techniques. The role of calcium alteration and membrane potential were revealed using Fluo-4 AM and tetramethylrhodamine, methyl ester, perchlorate (TMRM) fluorescent dyes. In addition, chemical treatment with sodium dodecyl sulfate (SDS) solutions was tested. The results obtained demonstrate positive prospects for AP monitoring in different treatments for studies related to a wide range of myocardial diseases using lab-on-chip technology.

Semiconductor physics, quantum electronics & optoelectronics : SQO 22(2), 237-251 (2019). doi:10.15407/spqeo22.02.237, Published by Inst. of Semiconductor Physics, Kyiv

InAs nanowires (NWs) are recognized as a key material due to their unique transport properties. Despite remarkable progress in designing InAs NW device structures, there are still open questions on device variability. Here, we demonstrate that noise spectroscopy allows us to study not only the parameters of traps, but also to shed light on quantum transport in NW structures. This provides an important understanding of structural behavior as well as the background and strategy required to design NW structures with advanced properties.

We fabricate two-layer (TL) silicon nanowires (NW) field-effect transistors (FETs) with a liquid gate. The NW devices show advanced characteristics, which reflect reliable single-electron phenomena. A strong modulation effect of channel conductivity with effectively tuned parameters is revealed. The effect opens up prospects for applications in several research fields including bioelectronics and sensing applications. Our results shed light on the nature of single trap dynamics which parameters can be fine-tuned to enhance the sensitivity of liquid-gated TL silicon nanowire FETs.

Using WGM resonators allow achieving high accuracy in determining the substances permittivities due to the high Q-factor. The resonator with a microfluidic channel is promising for the study of small-volume liquids, which is especially important for bioliquids. In a Ka-band a sapphire resonator with microfluidic channel has been proposed as a measurement cell, but in the sub-THz range a quartz resonator has more suitable characteristics due to its high Q-factor. In the paper we propose a measurement cell for the determination of complex permittivity of liquids in sub-THz range on the basis of quasi-optical quartz resonator with a layer of plastic comprising a microfluidic channel. Experimental studies of the resonator structure are carried out and a model for numerical research in the software COMSOL Multiphysics is proposed. By means of c omparing the resonator frequencies and Q-factors values with the corresponding values obtained with the numerical model the correction of the model has been carried out for the water-filled microfluidic channel. It is shown that the model for numerical studies correctly describes the resonator structure. The values of the resonator frequency and Q-factor obtained experimentally and numerically, for the microfluidic channel filled with the substances with well-known complex permittivity (methanol, propanol, ethanol, acetone), are in good agreement, which indicates the possibility of using the resonator as a measurement cell allowing the research on small-liquid permittivity using the special calibration procedure.

Here we report on the effect of gamma radiation treatment on transport properties and single-trap kinetics in Si nanowire (NW) field effect transistor (FET) structures. We used noise spectroscopy as a powerful method for advanced physical characterization of nanoscale devices. Our results demonstrate that transport properties of NW FETs can be changed using small doses of gamma radiation treatment. We reveal an enhancement of the gate coupling effect, which is explained as a result of the reorganization of the native defect structure after treatment. The radiation treatment approach allows the single-trap dynamic to be changed, which opens up prospects for a number of fundamental studies and applications of Si NW FET device structures, including biosensors.

In this paper, we report on the results of features in the discovered effect of a strong change in the microwave losses (quenching) in HTS-based coplanar waveguide (CPW) at certain values of the input power Pin and direct current (dc) I dc . Two waveguides were studied: CPW-150 and CPW-75, fabricated of epitaxial 150and 75-nm YBCO films. The insertion loss of CPW IL = 10 lg (P out /P in ) was measured versus both the operating temperature and the bias dc current I dc when a fixed level of the input X-band pulsed MW signal P in was applied. Here P out is the power measured at the CPW output. A pulse duration Ti was 5 μs with pulse repetition period T = 40 μs. Experiments showed a noticeable difference in specific values of I* = I dc corresponding to the P in -dependent quenching phenomenon in CPW-150 and CPW-75. With a weak input signal, the difference in behavior of CPWs is anticipated, i.e., quenching occurs at a lower current for thinner film. For P in > 1 W the situation is opposite, i.e., quenching for CPW-150 takes place at a lower I*. This is explained by stronger microwave heating of CPW-150.

We present the accurate microwave characterization technique for investigation of liquids of nanoliters volumes. This technique is an improved modification of the previously developed approach based on a sapphire whispering gallery mode (WGM) resonator. It is based on a high-quality quartz WGM resonator with microfluidic chip. Experimental data are obtained in Ka-band for the aqueous solution of glucose studied down to the concentration equal to concentration of glucose in human blood. The detection limit of the technique for low molecular weight substances was found to be less than their concentration in real biological samples.

We reveal the comparative relationship between small changes in quantum conductivity behavior for molecular junctions. We clarify the mechanisms of acquiring and losing additional thermal activation energy during average current flow in a gold-1,4 benzenediamine (BDA)-gold molecular junction and explain the quantum conductance modulation process. Small changes in working temperature lead to a change in quantum conductivity, which is reflected in random telegraph signal behavior. We demonstrate the high sensitivity of the BDA molecules to small changes in temperature. For BDA molecules, conductance thermo-sensitivity values are relatively high near to 0.8 ÷ 1.6 × 10 − 7 Ω − 1 K − 1 . This advantage can be used to measure weak variations in the ambient temperature. We show that the additional thermal energy arising from the change in temperature can impact on the strength of the electrode-molecule coupling, on the modulation of quantum conductivity. Local changes in quantum conductance of the order of quanta or smaller are conditioned by small random changes in the working regime arising from some of the activation processes. On the basis of the modulation of conductance, we calculate the magnitude of the spring constant of the 1,4 benzenediamine molecule as k s ≈ 7.1 × 10 − 3 N m − 1 at the stretching length of 0.03 nm for the Au−NH2 molecular junction.

This work presents the results of an accurate real-time microwave characterization of low-molecular-weight antioxidant biomarkers in low-volume solutions using a high-Q whispering gallery-mode dielectric resonator with a microfluidic channel. Sodium ascorbate and glutathione were characterized as the most significant non-enzymatic biomarkers of oxidative stress with respect to the reactive oxygen species scavenging system of cells. Microwave characterization was performed using a high-Q whispering-gallery-mode dielectric resonator with a microfluidic channel. The experiments demonstrated a fast response with high sensitivity in detecting sodium ascorbate and glutathione of different concentrations in biological solutions of small nanoliter volumes at a resonance frequency of about 35.5 GHz. These results indicate great potential for applying real-time microwave whispering-gallery-mode biosensing techniques in the characterization of low-molecular-weight antioxidant-specific biomarkers, which could be used in the laboratory and clinical biomedical research.

Antioxidants play a crucial role in the life sciences, as the regulators of biochemical reactions. We studied the dielectric properties of the low-molecular weight antioxidant specific biomarkers sodium ascorbate and glutathione in solutions of different concentrations. The biomarkers are multifunctional metabolites relevant to the reactive oxygen species (ROS) scavenging system of cells. The newly developed high-Q microwave whispering-gallery-mode (WGM) dielectric resonator based technique was applied. The technique allows investigation of liquids of nanoliter volumes filled in microfluidic channel within several milliseconds. The revealed peculiarities in the dependence of permittivity on concentrations of the sodium ascorbate and glutathione solutions are explained by differences in relaxation times and loses introduced by molecules of different shapes. We suggest that this novel approach offers the potential for the detection and characterization of ROS-relevant biomarkers with millisecond-time resolution.