Nanotechnology最新文献

Iron oxide nanoparticles (IONPs) are widely used for biomedical applications, and their nanoscale physicochemical properties and surface chemistry strongly influence biological interactions and overall performance. Their easily modified surfaces enable diverse biomedical applications, making it crucial to understand how different surfactants or coatings affect their properties and biological interactions. In this study, IONPs were synthesized by co-precipitation and subsequently functionalized with oleic acid, dextran, or ascorbic acid to investigate coating-dependent differences in physicochemical behavior and cellular responses. Comprehensive structural, magnetic, and colloidal characterizations were performed to ensure well-defined nanoparticle (NP) features. Biological evaluations included cytotoxicity assessments in both monolayer (2D) and spheroid (3D)in vitromodels incorporating healthy and cancer-derived mammalian cell lines from different tissue origins. Direct cytotoxicity was evaluated using WST-1, resazurin, and Annexin V/propidium iodide assays, and indirect cytotoxic effects were examined using NP-conditioned media. The findings revealed that cytotoxicity varied not only with the surface coating but also with the assay format and culture model, emphasizing the need for multi-parameter assessment when evaluating NP biocompatibility. Among the tested coatings, ascorbic acid-modified IONPs exhibited the greatest reduction in hydrodynamic size (22.9 nm) and demonstrated no detectable cytotoxic effects across multiple assays and cell lines, while maintaining key magnetic characteristics. These results highlight that nanoscale surface design can be strategically leveraged to achieve a favorable balance between magnetic performance and biological safety. The study underscores the importance of coating-driven modulation in guiding the development of next-generation magnetic NPs for biomedical applications.

The dynamic magnetization of magnetic nanoparticles (MNPs) arises from coupled Néel and Brownian relaxations, which are influenced by intrinsic particle properties such as size, saturation magnetization, magnetic anisotropy, and damping. While experimental AC magnetization measurements can reveal the collective dynamic behavior of MNP ensembles, extracting accurate nanoparticle-specific parameters from such data remains a challenge due to experimental limitations and model oversimplifications. To address this, we apply a stochastic Langevin model that explicitly captures the time-dependent magnetization response of MNPs under alternating magnetic fields by incorporating both thermal fluctuations and stochastic relaxation processes. This model provides a physically grounded framework for simulating magnetization hysteresis under experimental conditions, enabling parameter estimation through direct data fitting. In this work, we fit the stochastic Langevin model to experimentally measured hysteresis loops of different MNPs collected under a 20 mT, 5 kHz AC field. By coupling the model with Bayesian optimization and Gaussian process regression, we identify optimal values of key magnetic parameters: saturation magnetization (Ms), effective anisotropy (Ka), and Gilbert damping parameter (α). Furthermore, theMsis experimentally measured and employed as a validation parameter. Accordingly, the determination of theαand theKais based on two complementary criteria: (1) the best agreement between the simulated and experimental AC response magnetization hysteresis loops, quantified by the coefficient of determination (R2), and (2) the closest correspondence between the estimated and experimentally measuredMsvalues, evaluated using the mean absolute percentage error. Our approach is validated on four commercial MNP products (SHS30, IPG30, SHP25, and SHP15, from Ocean Nanotech, LLC), yielding high-fidelity fits to experimental data and robust estimation of their magnetic properties.

We realize strongly confined quantum dots (QDs) in InAs nanowires (NWs) by combining epitaxial crystal-phase control with chemical wet etching. A strong axial confinement is first introduced by growing closely spaced wurtzite (WZ) tunnel barriers in NWs to enclose a zinc blende (ZB) QD. The NW cross-section is then reduced by isotropic etching to obtain very small QDs, with a maximum observed charging energy>30 meV. Using low-temperature electrical characterization and finite-element method simulations, we study how charging energies and the onset of electron filling scale with QD diameter. For extremely small diameters, we identify a regime where stray capacitances become non-negligible, limiting further increase in charging energy by diameter reduction alone. This approach to increasing confinement is particularly relevant for understanding the strong spin-orbit interaction observed in crystal-phase QDs, possibly linked to polarization charges at the WZ/ZB interfaces. Small diameter QDs allow considerably weaker interfering electric fields when studied, but the QDs cannot be realized with epitaxial growth alone due to a loss of crystal phase control.

In this study, we present a detailed examination of the influence of the defects induced by the nitrogen plasma on the electrodynamic properties of few-layer graphene using terahertz (THz) time-domain spectroscopy (TDS). Initially, few-layer graphene is obtained using the chemical vapor deposition technique. Then, it is repeatedly treated with sub-3 kV nitrogen plasma that results in the creation of multiple lattice defects and the insertion of nitrogen observed by means of Raman and x-ray photoelectron spectroscopy. According to obtained spectra, the graphene lattice transferred onto a quartz substrate withstands up to 600 s of plasma treatment. However, the number of defects increases with treatment time: even 10 s treatment of initial graphene considerably reflects in Raman spectra. At the same time, 600 s of plasma treatment leads to the insertion of up to ∼9 at. % nitrogen, predominantly in pyridinic and pyrrolic/pyrazolic forms. Notably, the ratio between pyridinic, pyrrolic/pyrazolic and graphitic forms of nitrogen insertion in graphene remains constant independently on the treatment time. The described structural changes lead to the increase in THz transmittance with treatment time, as observed using THz- TDS. According to the proposed theoretical explanation based on the Kubo formalism, such dependence of THz spectra on an extension of treatment time indicates the decrease in total conductivity of graphene corresponding to the sufficient increase in electron collision broadening and the decrease in chemical potential caused by plasma treatment. Therefore, nitrogen plasma treatment is proven as an effective, robust and scalable method for adjusting the conductivity and transport properties of graphene widening its potential applications in THz electronics and photonics.

We investigate the atomic-layer-deposition (ALD) mechanism of In₂O₃using the InCp precursor with H₂O and O₂coreactants through density functional theory (DFT) calculations under experimentally relevant conditions. InCp adsorption on hydroxylated SiO₂is strongly favorable, forming In-O bonds and releasing C₅H₆(g) with free-energy gains of -0.48 eV, enabling nearly complete saturation of surface -OH sites. During ALD cycling, the surface-bound In species appear as either Cp-containing or Cp-free motifs, and these two states exhibit distinct oxidation pathways. O₂oxidizes Cp-free In sites to form In-O networks, with a decrease in the free energy by -0.96 eV. However, it cannot remove the remaining Cp ligand. Conversely, H₂O readily converts the Cp ligand into -OH groups, reducing the free energy by -0.56 eV, while it cannot oxidize Cp-free In, which is strongly unfavorable. When supplied together, O₂and H₂O provide complementary reactivity that enables complete oxidation of both surface motifs, consistent with the experimentally observed high growth-per-cycle (GPC) in simultaneous exposure. These mechanistic insights clarify the origins of oxidant-dependent GPC trends and offer guidance for optimizing In₂O₃ALD processes for energy and electronic applications.

Magnetic resonance imaging (MRI) is a non-invasive and non-ionizing imaging modality that provides high-resolution images of internal organs such as the breast, brain, and cardiovascular system, enabling three-dimensional visualization of soft tissues. While MRI offers excellent soft tissue contrast, its sensitivity can be further enhanced using contrast agents, and many clinical applications rely on exogenous agents to improve detection and diagnostic accuracy. Two primary classes are used clinically: paramagnetic substances, exemplified by gadolinium (Gd), which predominantly shorten longitudinal (T₁) relaxation, and superparamagnetic iron oxide nanoparticles (SPIONs), which exert strong effects on transverse (T₂) relaxation. The performance and safety of these agents are strongly influenced by their pharmacokinetics and biodistribution, including rapid recognition and clearance by the reticuloendothelial system, which can both enable liver-spleen imaging and limit target-specific contrast in other organs. In this review, we first summarize the fundamental principles of MRI contrast generation, with an emphasis on relaxation mechanisms relevant to magnetic nanoparticles (MNPs). We then discuss the use of MNPs as contrast agents in representative biomedical applications, focusing on cardiac, breast, and brain MRI and illustrating how organ-specific physiology constrains nanoparticle design and performance. Finally, we examine biocompatibility and safety considerations for both Gd-based agents and SPIONs, highlighting current regulatory concerns, open questions regarding long-term toxicity, and key challenges that must be addressed to translate next-generation nanoparticle-based MRI contrast agents into routine clinical practice.

Inspired by the ability of synaptic transistors to mimic the signal transmission and plasticity regulation of synapses between human neurons, and the property of NiTi shape memory alloy (SMA) to recover its original shape after deformation upon heating, we propose a biomimetic system capable of sensing pain and recovering its original shape upon heating after deformation by external force. This system combines a polyvinylidene fluoride (PVDF) and NiTi SMA piezoelectric sensor and IGZO/Cu₂O bipolar synaptic transistor (BST). The sensor, composed of PVDF and NiTi SMA, converts external stress into electrical pulses. Applying these pulses to the gate of the BST simulates the complex behavior of synapses. The thermal response of the NiTi SMA enables autonomous repair at controlled temperatures, while BST responds to piezoelectric signals to simulate pain sensitization and obtains different current responses by adjusting the baseline of the gate voltage, thereby simulating pain sensation in different parts of the robotic skin. This work demonstrates the integration of pain perception, pain sensitization, and self-healing functions, providing a new avenue for the development of next-generation intelligent robotic skin.

The presence of defects in transition metal dichalcogenides (TMDs) can lead to dramatic local changes in their properties which are of interest for a range of technologies including quantum security devices, hydrogen production, and energy storage. It is therefore essential to be able to study these materials in their native environments, including ambient conditions. Here we report single atom resolution imaging of atomic defects in MoS2, WSe2 and WS2 monolayers carried out in ambient conditions using conductive atomic force microscopy (C-AFM). By comparing measurements from a range of TMDs we use C-AFM to chemically identify the most likely atomic species for the defects observed and quantify their prevalence on each material, identifying oxygen chalcogen substitutions and transition metal substitutions as the most likely, and most common, defect types. Moreover, we demonstrate that C-AFM operated in ambient environments can resolve subtle changes in electronic structure with atomic resolution, which we apply to nitrogen-plasma doped WSe2 monolayers, demonstrating the capability of C-AFM to resolve electronic, and chemical-specific, details at the atomic scale.

Nanoimprint lithography is a technique that promises a low-cost, high-throughput, and high-resolution method for fabricating nanostructures, which may be used in communications, sensing, and emerging technologies such as augmented reality glasses. We present a comprehensive analysis of an ultraviolet nanoimprint lithography protocol using a resin-stamp platform, introduced by OpTool AB, for the production of 1D and 2D guided mode resonance grating structures. We assess their performance optically, a method rarely reported, to investigate the device functionality and make practical comparisons to electron-beam lithography. We achieve a representative resolution of 30 nm, which leads to good optical resonances, but we also note issues with inconsistent patterning over large areas (>1 mm²) and short shelf-lives of the chemicals involved. We conclude that, while Nanoimprint lithography can fabricate structures on a par with electron beam lithography, it also presents some challenges in producing functional devices at lower throughputs, a key consideration for small research laboratories.

Magnetic droplet solitons-self-localised, strongly nonlinear spin-wave states-offer compact microwave sources in nanocontact (NC) spin-torque oscillators, yet their frequency agility and coherence remain sensitive to device geometry. Here we introduce a wedge-shaped (thickness-graded) free layer to engineer the internal demagnetising field and thereby control droplet nucleation, frequency and linewidth within a single device. Using micromagnetic simulations (Mumax3) of spin-valve with strong perpendicular anisotropy Co/Ni free layer, we place NC at systematically varied positions along the gradient and extract the formation of droplet as well as nucleation time and current and steady-state spectra. We find that thicker regions require higher current and exhibit wider hysteresis-like loops, while the nucleation frequency increases monotonically towards the thin side, accompanied by improved phase coherence. In dual-contact geometries, we map a thickness-gradient-dependent critical merging distance and its current scaling. These results establish thickness gradients as a practical, fabrication-compatible knob for tuning droplet dynamics and suggest gradient-engineered free layers for fast, coherent droplet-based microwave oscillators.