Laser nanostructuring is a powerful tool to produce different nanomaterials such as nanoparticles and surface relief structures. It was shown that pulsed laser ablation of thin 250 nm Fe film in acetone allows obtaining core-shell Fe@FeO nanoparticles with a mean size of 90 nm. Fabrication of femtosecond laser-induced periodic surface structures on a Si substrate surface with subsequent deposition of a NiFe/IrMn exchange-biased bilayer causes the appearance of an additional out-of-plane magnetization component with keeping exchange bias. Obtained nanomaterials look promising for designing magnetic biosensors with an improved detection limit.

We report the observation of negative differential resistance (NDR) in single-atom single-electron devices based on arsenic, phosphorus and potassium dopants implanted in a silicon host matrix. All devices exhibit NDR, with the potassium-based one exhibiting NDR at room temperature because of the larger charging and confinement energies. Our experimental results are reproduced with a simple model that assumes sequential electron tunnelling through two series-connected charge centres, each having two discrete energy levels. The model utilises the nonequilibrium Keldysh diagram technique, and its accuracy is improved by introducing an effective local temperature that depends on the dissipated power and by semi-classical averaging of fluctuations of the dopant spectra. Our control experiments on undoped devices revealed the bandgap boundaries of the silicon host matrix which we successfully modelled using a single-barrier approximation. The use of unconventional dopants in silicon with high characteristic energies, such as potassium, is a major step forward toward the implementation of room-temperature single-atom electronics.

Immunosensors based on field-effect transistors with nanowire channels (NWFETs) provide fast and real-time detection of a variety of biomarkers without the need for additional labels. The key feature of the developed immunosensor is the coating of silicon NWs with multilayers of polyelectrolytes (polyethylenimine (PEI) and polystyrene sulfonate (PSS)). By causing a macromolecular crowding effect, it ensures the “soft fixation” of the antibodies into the 3-D matrix of the oppositely charged layers. We investigated the interaction of prostate-specific antigen (PSA), a biomarker of prostate cancer, and antibodies adsorbed in the PEI and PSS matrix. In order to visualize the formation of immune complexes between polyelectrolyte layers using SEM and AFM techniques, we employed a second clone of antibodies labeled with gold nanoparticles. PSA was able to penetrate the matrix and concentrate close to the surface layer, which is crucial for its detection on the nanowires. Additionally, this provides the optimal orientation of the antibodies’ active centers for interacting with the antigen and improves their mobility. NWFETs were fabricated from SOI material using high-resolution e-beam lithography, thin film vacuum deposition, and reactive-ion etching processes. The immunosensor was characterized by a high sensitivity to pH (71 mV/pH) and an ultra-low limit of detection (LOD) of 0.04 fg/mL for PSA. The response of the immunosensor takes less than a minute, and the measurement is carried out in real time. This approach seems promising for further investigation of its applicability for early screening of prostate cancer and POC systems.

In this work, we present the studies of structural phase transitions in FeSe 0.675 Te 0.3 S 0.025 crystals. The data obtained indicate a significant change in the behavior of many characteristics during the transition in this composition compared to the case of the unsubstituted FeSe. The resistivity at low temperatures for the studied FeSe 0.675 Te 0.3 S 0.025 is proportional to the square of the temperature, while for pure FeSe below the structural transition it depends almost linearly on temperature. 77 Se NMR studies also confirm a change in the type of phase transition. The NMR data showed a noticeable line broadening below the structural transition and an anomaly in the temperature dependence of the relaxation rate, which was not observed in FeSe. Our results confirm the quantum criticality of Fe(Se,Te) at a low Te content or existence of the nematicity change point (NCP). This makes the phase diagram of quasi-binary Fe(Se,Te) compounds generally consistent with the phase diagram of FeSe under pressure. In both cases, there is a local minimum in the superconducting critical temperature near NCP and a strong increase in the superconducting critical temperature near the point of complete suppression of nematicity.

The possibility of synthesizing nanoparticles by pulsed laser ablation of thin cobalt films in water is shown. The average size of the formed nanoparticles varies in the range of 70–1020 nm depending on the thickness of the ablated film. At film thicknesses less than 35 nm, the size dispersion of the nanoparticles is minimum. The produced nanoparticles are characterized by magnetic response and structurally most closely correspond to cobalt oxide Co3O4.

In this work we present an automatic thermoregulation system for biosensors based on field-effect transistors with a nanowire channel, which provides full control on the required temperature regime in bioanalytical analises. The system elements, including field-effect transistors with a nanowire channel, temperature sensors and heaters, were fabricated on a single silicon cristal using electron beam lithography, reactive ion etching and high-vacuum deposition techniques. Unicue electronics have been developed to control and maintain temperature. The dependence of thermometer readout on heating power was measured, which is in good agreement with the results of numerical simulation. A demonstration of a thermoregulation system with PID-feedback was carried out, ensuring the establishment of a desiered temperature in the range of 30-70◦ C in 18 s in liquid. A demonstration of a thermoregulation system for detecting nucleic acids was carried out using synthetic single-stranded DNA, which is a gene fragment from the bacterium Escherichia coli. The minimal detectable response was observed for a sample with a concentration of 3 fM.

We present a CMOS compatible technique for fabrication a sensor system based on field-effect transistors with a nanowire channel with an integrated thermoregulation elements. The proposed system provides the necessary temperature regimes for many bioanalytical studies. Field-effect transistors with a nanowire channel were fabricated using of reactive-ion etching of the upper layer of a silicon on insulator through a mask formed by electron beam lithography. Titanium thermoresistive strips for temperature control were located on the surface of the chip nearby to the nanowire transistors. Their fabrication is carried out simultaneously with the formation of contact pads to the transistor electrodes, which made it possible to avoid additional technological steps. A demonstration of a system with a built-in temperature controller for the determination of nucleic acids was carried out on model oligonucleotides. Increasing the operating temperature of the device to the ranges at which DNA hybridization occurs most efficiently allows increasing specificity and avoiding false positive results, as well as reducing analysis time. The possibility of heating up to 85–90∘C allows you to reuse such devices.

In this work, we present the studies of structural phase transitions in Fe(Se,Te) crystals in the range of about 30 tellurium. We found a significant change in the properties of the ordered state of these compositions compared to the case of pure FeSe. The resistivity at low temperatures for the studied Fe(Se,Te) is proportional to the square of the temperature while for pure FeSe below the structural transition it depends almost linearly on temperature. The NMR data show a noticeable line broadening below the structural transition and an anomaly in the temperature dependence of the relaxation rate in the tellurium-substituted compounds, which was not observed in the pure FeSe. This reveals in quasi-binary compounds of iron-based superconductors a region of quantum criticality similar to that which exists when the nematicity of FeSe is suppressed under pressure and which precedes the emergence of high-temperature superconductivity in FeSe under hydrostatic pressure.

One-dimensional femtosecond laser-induced periodic surface structures (LIPSS) were formed on amorphous silicon (a-Si) films doped with phosphorus (n-a-Si) and boron (p-a-Si). The formed LIPSS ridges are directed orthogonally to the laser polarization and their period decreases from 1.1 ± 0.1 µm to 0.84 ± 0.07 µm for p-a-Si and from 1.06 ± 0.03 to 0.98 ± 0.01 for n-a-Si when the number of laser pulses per unit area increases from 30 to 120. Raman spectra analysis indicated nonuniform nanocrystallization of the irradiated films, which have a composite structure of amorphous matrix containing nanocrystalline Si phase with volume fraction decreasing with depth from ~80 to ~40% for p-a-Si and from ~20 to ~10% for n-a-Si. Observed in plane conductivity anisotropy of up to 1 order for irradiated films may be explained by the LIPSS depolarizing effect, excessive ablation of the film between LIPSS ridges, as well as anisotropic crystalline phase distribution within the film.

Cold atmospheric plasma (CAP) jets with helium (He) and argon (Ar) plasma-forming gases were used to modify the structure, photoluminescence (PL), and electrical properties of arrays of silicon nanowires (SiNWs) with initial cross-section sizes of the order of 100 nm and length of about 7‒8 microns. The CAP source consisted of a 30 kHz voltage generator with a full power up to 5 W and the CAP treatment for 1‒5 min resulted in spattering of SiNWs’ tips followed by redeposition of silicon atoms. An increase of the silicon oxide phase and a decrease of the PL intensity were observed in the plasma processed SiNW arrays. A decrease of the free hole concentration and an increase in the free electron density were revealed in heavily boron and phosphorous doped SiNWs, respectively, as it was monitored by means of the Raman spectroscopy, considering a coupling of the light scattering by phonon and free charge carriers (Fano effect) in SiNWs. The obtained results demonstrate that the CAP treatment can be used to change the length, sharpness, luminescence intensity, and electrical properties of silicon nanowires for possible applications in optoelectronics and sensorics.

We report oscillations of current which accompany anodic deposition from Mn(II) solutions in a neutral acetic buffer and also cathodic birnessite deposition from alkaline permanganate solutions. We demonstrate that for both processes, oscillations appear at high enough overpotentials. The current oscillations are affected by solution convection. The results of rotating disc electrode experiments favor mixed control, with higher diffusion contribution in case of cathodic deposition. Electron microscopy combined with electron and X-ray diffraction and coulometric analysis is applied to assign oscillations to certain morphological features of the deposits. A pronounced difference in microstructure is found for anodic and cathodic deposits formed under oscillating growth conditions: “anodic” birnessite consists of parallel layers of small crystals, whereas “cathodic” birnessite is globular. This difference is interpreted with account for specific crystallographic features. Namely, the more ordered birnessite lattice formed by reduction of permanganate favors a preferentially lateral growth of thin lamellas, in contrast to birnessite having a pronounced interplane distortion, formed in the course of anodic deposition. We assign the periodic current decrease to diffusion limitations in growing porous layers and assume that the subsequent current increase in each period corresponds to dendrite-like growth of a low number of crystals located in the outer diffusion layer.

The self-assembling of nanosized materials is a promising field for research and development. Multiple approaches are applied to obtain inorganic, organic and composite nanomaterials with different functionality. In the present work, self-assembling nanocomplexes (NCs) were prepared on the basis of enzymes and polypeptides followed by the investigation of the influence of low-molecular weight biologically active compounds on the properties of the NCs. For that, the initially possible formation of catalytically active self-assembling NCs of four hydrolytic enzymes with nine effectors was screened via molecular modeling. It allowed the selection of two enzymes (hexahistidine-tagged organophosphorus hydrolase and penicillin acylase) and two compounds (emodin and naringenin) having biological activity. Further, such NCs based on surface-modified enzymes were characterized by a batch of physical and biochemical methods. At least three NCs containing emodin and enzyme (His6-OPH and/or penicillin acylase) have been shown to significantly improve the antibacterial activity of colistin and, to a lesser extent, polymyxin B towards both Gram-positive bacteria (Bacillus subtilis) and Gram-negative bacteria (Escherichia coli).

The density functional theory is used to obtain single-particle spectra of fragments of the one-dimensional metal–organic chain of a coordinated polymer. The effective resistance of the organic part of the polymer is calculated, along with the characteristic Coulomb energy and the effective capacitance of the charge center. The number of conduction channels in an experimentally studied reservoir network based on the observed polymer chains is estimated.

Gold nanoparticles (AuNPs) are popular labels for colorimetric detection of various analytes, involving proteins, nucleic acids, viruses, and whole cells because of their outstanding optical properties, inertness, and modification variability. In this work, we present an improved approach for enhancement of color intensity for DNA membrane microarrays based on seed-mediated growth of AuNP labels. Biotin-labeled DNA is hybridized with capture oligonucleotide probes immobilized on the microarrays. Then biotin is revealed by a streptavidin–AuNP conjugate followed by the detection of AuNPs. Optimization of seed-mediated enlargement of AuNPs by the reduction of tetrachloroauric acid with hydroxylamine made it possible to change the coloring of specific spots on the microarrays from pink to a more contrasting black with minor background staining. Mean size of the resulting AuNPs was four times larger than before the enhancement. Adjusting the pH of HAuCl4 solution to 3.5 and use of a large excess of hydroxylamine increased the signal/background ratio by several times. The method’s applicability was demonstrated for quantification of a short oligonucleotide of 19 bases and full-length TEM-type β-lactamase genes of 860 bp responsible for the development of bacterial resistance against β-lactam antibiotics. Improved protocol for AuNP enlargement may be further transferred to any other membrane-based assays of nucleic acids with both instrumental and visual colorimetric detection.

Ge2Sb2Te5 based devices attract the attention of researchers due to wide opportunities in designing phase change memory. Herein, we studied a possibility to fabricate periodic micro- and nanorelief at surfaces of Ge2Sb2Te5 thin films on silicon oxide/silicon substrates under multi-pulse femtosecond laser irradiation with the wavelength of 1250 nm. One-dimensional lattices with periods of 1250 ± 90 and 130 ± 30 nm were obtained depending on the number of acted laser pulses. Emergence of these structures can be explained by plasmon-polariton generation and laser-induced hydrodynamic instabilities, respectively. Additionally, formation of the lattices whose spatial period is close to the impacted laser wavelength can be modelled by considering the free carrier contribution under intensive photoexcitation. Raman spectroscopy revealed both crystallization and re-amorphization of the irradiated films. The obtained results show a possibility to fabricate rewritable all-dielectric data-storage devices based on Ge2Sb2Te5 with the periodic relief.

The possibility of manufacturing silicon nanoparticles by picosecond laser fragmentation of silicon microparticles in water is analysed. It is shown that for fragmentation duration of 40 min, the dependence of the average sizes of particles on the initial mass concentration of the micropowder varied in the range of 0.5 – 12 mg mL −1 is nonmonotonic, with the maximum average size of 165 nm being achieved at a concentration of 5 mg mL −1 . To explain the obtained result, the simulation of propagation of a focused laser beam in a scattering suspension of silicon microparticles is performed for their different mass concentrations. It is demonstrated that at concentrations not exceeding 5 mg mL −1 , fragmentation occurs in the paraxial region of the beam when it propagates deep into the cuvette with a suspension, while at higher concentrations it occurs primarily in the superficial layer owing to strong extinction. Calculations results allow the experimental features of the formation of silicon nanoparticles to be explained. Spectrophotometry measurements on suspensions of nanoparticles obtained at the initial concentration of microparticles of 12 mg mL −1 are compared with the theoretical estimates of the absorption and scattering coefficients obtained in the framework of the Mie theory. Measured optical properties indicate the potential of using fragmented nanoparticles as scattering and/or absorbing contrast agents in optical imaging of biological objects.

Femtosecond laser treatment allows to fabricate periodic structures at amorphous hydrogenated silicon surfaces on areas more than a square millimeter. The period of the structures is near the laser wavelength and determines by the nonequilibrium electrons concentration at high power laser excitation. The obtained structures possess a pronounced electrophysical anisotropy.

The superior rate capabilities of metal ion battery materials based on Prussianblue analogues (PBAs) are almost exclusively ascribed to the extremely fast solid-state ionicdiffusion, which is possible due to structural voids and spacious three-dimensional channels inPBA structures. We performed a detailed electroanalytical study of alkali ion diffusivities innanosized cation-rich and cation-poor PBAs obtained as particles or electrodepositedfilms inboth aqueous and non-aqueous media, which resulted in a solid conclusion about theexceptionally slow ionic transport. We show that the impressive rate capability of PBAmaterials is determined solely by the small size of the primary particles of PBAs, while theapparent diffusion coefficients are 3-5 orders of magnitude lower than those reported inearlier studies. Ourfinding calls for a reconsideration of the apparent facility of ionic transportin PBA materials and deeper analysis of the charge carrier-host interactions in PBAs

Femtosecond laser-modified amorphous silicon (a-Si) films with optical and electrical anisotropy have perspective polarization-sensitive applications in optics, photovoltaics, and sensors. We demonstrate the formation of one-dimensional femtosecond laser-induced periodic surface structures (LIPSS) on the surface of phosphorus- (n-a-Si) and boron-doped (p-a-Si) amorphous silicon films. The LIPSS are orthogonal to the laser polarization, and their period decreases from 1.1 ± 0.1 µm to 0.84 ± 0.07 µm for p-a-Si and from 1.06 ± 0.03 to 0.98 ± 0.01 for n-a-Si when the number of laser pulses per unit area increases from 30 to 120. Raman spectra analysis indicates nonuniform nanocrystallization of the irradiated films, with the nanocrystalline Si phase volume fraction decreasing with depth from ~80 to ~40% for p-a-Si and from ~20 to ~10% for n-a-Si. LIPSS’ depolarizing effect, excessive ablation of the film between LIPSS ridges, as well as anisotropic crystalline phase distribution within the film lead to the emergence of conductivity anisotropy of up to 1 order for irradiated films. Current–voltage characteristic nonlinearity observed for modified p-a-Si samples may be associated with the presence of both the crystalline and amorphous phases, resulting in the formation of potential barriers for the in-plane carrier transport and Schottky barriers at the electric contacts.

Ge2Sb2Te5 (GST225) looks to be a promising material for rewritable memory devices due to its relatively easy processing and high optical and electrophysical contrast for the crystalline and amorphous phases. In the present work, we combined the possibilities of crystallization and anisotropic structures fabrication using femtosecond laser treatment at the 1250 nm wavelength of 200 nm thin amorphous GST225 films on silicon oxide/silicon substrates. A raster treatment mode and photoexcited surface plasmon polariton generation allowed us to produce mutually orthogonal periodic structures, such as scanline tracks (the period is 120 ± 10 μm) and laser-induced gratings (the period is 1100 ± 50 nm), respectively. Alternating crystalline and amorphous phases at the irradiated surfaces were revealed according to Raman spectroscopy and optical microscopy studies for both types of structures. Such periodic modulation leads to artificial optical and electrophysical anisotropy. Reflectance spectra in the near infrared range differ for various polarizations of probing light, and this mainly results from the presence of laser-induced periodic surface structures. On the other hand, the scanline tracks cause strong conductivity anisotropy for dc measurements in the temperature range of 200–400 K. The obtained results are promising for designing new GST225-based memory devices in which anisotropy may promote increasing the information recording density.