Search Results (27)

To enhance the sensitivity of graphene-DNA sensors for Hg²⁺ detection, a novel graphene nanoribbon-DNA sensor was fabricated using a template-assisted approach. Silicon nanowires served as templates to decorate the graphene device, followed by plasma etching to delineate graphene nanoribbons. After template removal, the resulting sensors based on silicon nanowire templates were successfully constructed. DNA sequences containing four guanine bases were conjugated with graphene sensors prepared using the templates. The carboxyl groups on the edges of the graphene nanoribbons were activated with EDC/NHS chemistry to facilitate covalent bonding with amino-modified DNA. The kinetic response and Hg²⁺ detection capability of the fabricated sensors were characterized using a semiconductor parameter analyzer. Results indicated that the silicon nanowire-templated graphene nanoribbon sensor exhibited high sensitivity, with a detection limit of 3.62 pM. This innovative approach further improved the sensitivity of graphene-DNA sensors for Hg²⁺ detection. Full article

In this work, we described the variations in the defect energy levels of four different ZnO morphologies, namely nanoribbons, nanorods, nanoparticles, and nanoshuttles. All the ZnO morphologies were grown on a seeded 4% Boron-doped p-type silicon (p-Si) wafer by using two different synthesis techniques, which are chemical bath deposition and microwave-assisted methods. The defect energy levels were analyzed by using the Deep-Level Transient Spectroscopy (DLTS) characterization method. The DLTS measurements were performed in the 123 K to 423 K temperature range. From the DLTS spectra, we found the presence of different trap-related defects in the synthesized ZnO nanostructures. We labeled all the traps related to the four different ZnO nanostructures as P₁, P₂, P₃, P₄, and P₅. We discussed the presence of defects by measuring the activation energy (E_a) and capture cross-section ($\alpha$). The lowest number of defect energy levels was exhibited by the ZnO nanorods at 0.27 eV, 0.18 eV, and 0.75 eV. Both the ZnO nanoribbons and nanoparticles show four traps, which have energies of 0.31 eV, 0.23 eV, 0.87 eV, and 0.44 eV and 0.27 eV, 0.22 eV, 0.88 eV, and 0.51 eV, respectively. From the DLTS spectrum of the nanoshuttles, we observe five traps with different activation energies of 0.13 eV, 0.28 eV, 0.25 eV, 0.94 eV, and 0.50 eV. The DLTS analysis revealed that the origin of the nanostructure defect energy levels can be attributed to Zinc vacancies (V_zn), Oxygen vacancies (V_o), Zinc interstitials (Zn_i), Oxygen interstitials (O_i), and Zinc antisites (Zn_o). Based on our analysis, the ZnO nanorods showed the lowest number of defect energy levels compared to the other ZnO morphologies. Full article

The development of highly sensitive diagnostic systems for the early revelation of diseases in humans is one of the most important tasks of modern biomedical research, and the detection of the core antigen of the hepatitis C virus (HCVcoreAg)—a protein marker of the hepatitis C virus—is just the case. Our study is aimed at testing the performance of the nanoribbon biosensor in the case of the use of two different types of molecular probes: the antibodies and the aptamers against HCVcoreAg. The nanoribbon sensor chips employed are based on “silicon-on-insulator structures” (SOI-NR). Two different HCVcoreAg preparations are tested: recombinant β-galactosidase-conjugated HCVcoreAg (“Virogen”, Watertown, MA, USA) and recombinant HCVcoreAg (“Vector-Best”, Novosibirsk, Russia). Upon the detection of either type of antigen preparation, the lowest concentration of the antigen detectable in buffer with pH 5.1 was found to be approximately equal, amounting to ~10⁻¹⁵ M. This value was similar upon the use of either type of molecular probes. Full article

Prostate cancer (PC) is one of the major causes of death among elderly men. PC is often diagnosed later in progression due to asymptomatic early stages. Early detection of PC is thus crucial for effective PC treatment. The aim of this study is the simultaneous highly sensitive detection of a palette of PC-associated microRNAs (miRNAs) in human plasma samples. With this aim, a nanoribbon biosensor system based on “silicon-on-insulator” structures (SOI-NR biosensor) has been employed. In order to provide biospecific detection of the target miRNAs, the surface of individual nanoribbons has been sensitized with DNA oligonucleotide probes (oDNA probes) complementary to the target miRNAs. The lowest concentration of nucleic acids, detectable with our biosensor, has been found to be 1.1 × 10⁻¹⁷ M. The successful detection of target miRNAs, isolated from real plasma samples of PC patients, has also been demonstrated. We believe that the development of highly sensitive nanotechnology-based biosensors for the detection of PC markers is a step towards personalized medicine. Full article

Graphyne has attractive electronic properties that make it a possible replacement of silicon in FET technology. In FET technology, the goal is to achieve low power dissipation and lower subthreshold swing. In this study, we focused on achieving these goals and studied the electronic properties of α-graphyne nanoribbons. We simulated the transfer and output characteristics of an α-graphyne ballistic nanoribbon FET. We used the tight-binding model with nearest-neighbor approximation to obtain the band structure which gives the same band structure as the one found from the DFT. In order to simulate the I-V characteristics of the transistor we used the non-equilibrium Green’s function (NEGF) formalism. The results show that the modeled FET can provide a high Ion/Ioff ratio and low subthreshold swing. We also studied the effects of defects as defects cannot be avoided in any practical device. The study shows that the Ion/Ioff ratio and subthreshold swing improves as defects are added, but the delay time and dynamic power dissipation worsen. Full article

The dimensions of nanoribbons have a significant impact on their material properties. In the fields of optoelectronics and spintronics, one-dimensional nanoribbons exhibit distinct advantages due to their low-dimensional and quantum restrictions. Novel structures can be formed by combining silicon and carbon at different stoichiometric ratios. Using density functional theory, we thoroughly explored the electronic structure properties of two kinds of silicon–carbon nanoribbons (penta-SiC₂ and g-SiC₃ nanoribbons) with different widths and edge conditions. Our study reveals that the electronic properties of penta-SiC₂ and g-SiC₃ nanoribbons are closely related to their width and orientation. Specifically, one type of penta-SiC₂ nanoribbons exhibits antiferromagnetic semiconductor characteristics, two types of penta-SiC₂ nanoribbons have moderate band gaps, and the band gap of armchair g-SiC₃ nanoribbons oscillates in three dimensions with the width of the nanoribbon. Notably, zigzag g-SiC₃ nanoribbons exhibit excellent conductivity, high theoretical capacity (1421 mA h g⁻¹), moderate open circuit voltage (0.27 V), and low diffusion barriers (0.09 eV), making them a promising candidate for high storage capacity electrode material in lithium-ion batteries. Our analysis provides a theoretical basis for exploring the potential of these nanoribbons in electronic and optoelectronic devices as well as high-performance batteries. Full article

In this study, epitaxial graphene layers of cm² sizes were grown on silicon carbide (SiC) substrates by high-temperature sublimation. The behavior of the two crystallographic SiC-polar faces and its effect on the growth mechanism of graphene layers and their properties were investigated. Crystallographic structural differences observed in AFM studies were shown to cause disparities in the electrical conductivity of the grown layers. On the silicon-polar (Si-polar) face of SiC, the graphene formation occurred in spike-like structures that originated orthogonally from atomic steps of the substrate and grew outwards in the form of 2D nucleation with a fairly good surface coverage over time. On the carbon-polar (C-polar) face, a hexagonal structure already formed at the beginning of the growth process. On both polar faces, the known process of step-bunching promoted the formation of nm-scale structural obstacles. Such a step-bunching effect was found to be more pronounced on the C-polar face. These 2D-obstacles account for a low probability of a complete nano-sheet formation, but favor 2D-structures, comparable to graphene nanoribbons. The resulting direction-dependent anisotropic behavior in electrical conductivity measured by four-point probe method mainly depends on the height and spacing between these structural-obstacles. The anisotropy becomes less prudent as and when more graphene layers are synthesized. Full article

The electronic transport properties and rectifying behaviors of armchair silicene nanoribbons (ASiNRs) were investigated by using first-principles density functional theory, in which the left lead was pristine ASiNR and the right lead was doped ASiNR where two phosphorus (P) atoms replaced a pair of adjacent silicon atoms in the same sublattice A (AA-P₂). Two types of AA-P₂-doped models were considered for P dopant-substitute silicon atoms at the center or edges. The results showed that the rectification behavior of the system with a large rectifying ratio could be found, which could be modulated by changing the width of the silicene nanoribbons or the position of the AA-P₂ dopant. Mechanisms were revealed to explain the rectifying behaviors and provide a theoretical basis for semiconductor rectifier devices. Full article

We numerically investigated the use of graphene nanoribbons placed on top of silicon-on-insulator (SOI) strip waveguides for light polarization control in silicon photonic-integrated waveguides. We found that two factors mainly affected the polarization control: the graphene chemical potential and the geometrical parameters of the waveguide, such as the waveguide and nanoribbon widths and distance. We show that the graphene chemical potential influences both TE and TM polarizations almost in the same way, while the waveguide width tapering enables both TE-pass and TM-pass polarizing functionalities. Overall, by increasing the oxide spacer thickness between the silicon waveguide and the top graphene layer, the device insertion losses can be reduced, while preserving a high polarization extinction ratio. Full article

Quick label-free virus screening and highly sensitive analytical tools/techniques are becoming extremely important in a pandemic. In this study, we developed a biosensing device based on the silicon nanoribbon multichannel and dielectrophoretic controlled sensors functionalized with SARS-CoV-2 spike antibodies for the use as a platform for the detection and studding of properties of viruses and their protein components. Replicatively defective viral particles based on vesicular stomatitis viruses and HIV-1 were used as carrier molecules to deliver the target SARS-CoV-2 spike S-proteins to sensory elements. It was shown that fully CMOS-compatible nanoribbon sensors have the subattomolar sensitivity and dynamic range of 4 orders. Specific interaction between S-proteins and antibodies leads to the accumulation of the negative charge on the sensor surface. Nonspecific interactions of the viral particles lead to the positive charge accumulation. It was shown that dielectrophoretic controlled sensors allow to estimate the effective charge of the single virus at the sensor surface and separate it from the charge associated with the binding of target proteins with the sensor surface. Full article

The Special Issue of Nanomaterials “Frontiers in Nanotoxicology” highlights the modern problems of nanotoxicology and nanobiomedicine, including the toxicity of metal-based, silicon-based, carbon-based, and other types of nanoparticles, occupational safety of nanoproduction workers, comprehensive assessment on new biomedical nanomaterials, improvement of nanotoxicology methods, as well as the current state and prospects of research in the fields of theoretical, experimental, and toxicological aspects of the prospective biomedical application of functionalized magnetic nanoparticles activated by a low-frequency non-heating alternating magnetic field, biomedical applications and the toxicity of graphene nanoribbons, and fetotoxicity of nanoparticles [...] Full article

Silicon-on-insulator (SOI) nanowire or nanoribbon field-effect transistor (FET) biosensors are versatile platforms of electronic detectors for the real-time, label-free, and highly sensitive detection of a wide range of bioparticles. At a low analyte concentration in samples, the target particle diffusion transport to sensor elements is one of the main limitations in their detection. The dielectrophoretic (DEP) manipulation of bioparticles is one of the most successful techniques to overcome this limitation. In this study, TCAD modeling was used to analyze the distribution of the gradient of the electric fields E for the SOI-FET sensors with embedded DEP electrodes to optimize the conditions of the dielectrophoretic delivery of the analyte. Cases with asymmetrical and symmetrical rectangular electrodes with different heights, widths, and distances to the sensor, and with different sensor operation modes were considered. The results showed that the grad E² factor, which determines the DEP force and affects the bioparticle movement, strongly depended on the position of the DEP electrodes and the sensor operation point. The sensor operation point allows one to change the bioparticle movement direction and, as a result, change the efficiency of the delivery of the target particles to the sensor. Full article

A nanoribbon biosensor (NRBS) was developed to register synthetic DNAs that simulate and are analogous to miRNA-17-3p associated with colorectal cancer. Using this nanoribbon biosensor, the ability to detect miRNA-17-3p in the blood plasma of a patient diagnosed with colorectal cancer has been demonstrated. The sensing element of the NRBS was a nanochip based on a silicon-on-insulator (SOI) nanostructure. The nanochip included an array of 10 nanoribbons and was designed with the implementation of top-down technology. For biospecific recognition of miRNA-17-3p, the nanochip was modified with DNA probes specific for miRNA-17-3p. The performance of the nanochip was preliminarily tested on model DNA oligonucleotides, which are synthetic analogues of miRNA-17-3p, and a detection limit of ~10⁻¹⁷ M was achieved. The results of this work can be used in the development of serological diagnostic systems for early detection of colorectal cancer. Full article

The detection of CA 125 protein in buffer solution with a silicon-on-insulator (SOI)-based nanoribbon (NR) biosensor was experimentally demonstrated. In the biosensor, sensor chips, bearing an array of 12 nanoribbons (NRs) with n-type conductance, were employed. In the course of the analysis with the NR biosensor, the target protein was biospecifically captured onto the surface of the NRs, which was sensitized with covalently immobilized aptamers against CA 125. Atomic force microscopy (AFM) and mass spectrometry (MS) were employed in order to confirm the formation of the probe–target complexes on the NR surface. Via AFM and MS, the formation of aptamer–antigen complexes on the surface of SOI substrates with covalently immobilized aptamers against CA 125 was revealed, thus confirming the efficient immobilization of the aptamers onto the SOI surface. The biosensor signal, resulting from the biospecific interaction between CA 125 and the NR-immobilized aptamer probes, was shown to increase with an increase in the target protein concentration. The minimum detectable CA 125 concentration was as low as 1.5 × 10⁻¹⁷ M. Moreover, with the biosensor proposed herein, the detection of CA 125 in the plasma of ovarian cancer patients was demonstrated. Full article

Nanoribbon chips, based on “silicon-on-insulator” structures (SOI-NR chips), have been fabricated. These SOI-NR chips, whose surface was sensitized with covalently immobilized oligonucleotide molecular probes (oDNA probes), have been employed for the nanoribbon biosensor-based detection of a circular ribonucleic acid (circRNA) molecular marker of glioma in humans. The nucleotide sequence of the oDNA probes was complimentary to the sequence of the target oDNA. The latter represents a synthetic analogue of a glioma marker—NFIX circular RNA. In this way, the detection of target oDNA molecules in a pure buffer has been performed. The lowest concentration of the target biomolecules, detectable in our experiments, was of the order of ~10⁻¹⁷ M. The SOI-NR sensor chips proposed herein have allowed us to reveal an elevated level of the NFIX circular RNA in the blood of a glioma patient. Full article