Beilstein Journal of Nanotechnology最新文献

Nanomechanical maps to test the mechanical response of the outer envelope of Pseudomonas aeruginosa were obtained utilizing atomic force microscopy in force-volume mode in the low range of loading forces when exposed to hypotonic (Milli-Q water), isotonic (PBS), and hypertonic (0.5 M NaCl) solutions. Imaging and mechanical testing showed that bacteria are highly resilient to deformation and can withstand repetitive indentations in the range of 500 pN. Analysis of force spectra revealed that although there are differences in the mechanical response within the first stages of nanoindentation, similar values in the slopes of the curves reflected a stable stiffness of about k _B = 20 mN/m and turgor pressures of P _t = 12.1 kPa. Interestingly, a change in the nonlinear regime of the force curves and a gradual increase in maximal deformation by the AFM tip from hypotonic to hypertonic solutions suggest a softening of the outer envelope, which we associate with intense dehydration and membrane separation between inner and outer envelopes. Application of a contact mechanics model to account for the minute differences in mechanical behavior upon deformation provided Young's moduli in the range of 0.7-1.1 kPa. Implications of the presented results with previously reported data in the literature are discussed.

The Gauss neuron is a nonlinear signal converter, whose transfer function (TF) is described by the derivative of some sigmoidal dependence. A superconducting Gauss neuron can be implemented as a two-junction interferometer shunted symmetrically by an additional inductance. This work analyzes three cases of asymmetry that can occur in the experimental samples of Gauss neurons, that is, unequal critical currents of the interferometer's Josephson junctions, asymmetric inductive shunting, and asymmetry of the input signal supply. We illustrate the modifications in equations and the shape of the TF compared to the symmetric case. The analysis performed provides an explanation for the key features observed in a previously conducted experiment.

High-entropy alloy nanoparticles (HEA NPs) represent a promising material class with significant potential in various applications, such as heterogeneous catalysis or magnetic devices. This is due to their exceptional compositional tunability arising from the synergistic interplay of multiple elements within a single particle. While laser-synthesized, surfactant-free colloidal HEA NPs have already been reported, the underlying formation mechanism remains unknown, particularly the underexplored preference of amorphous over crystalline structures warrants further investigation. Herein, we present a systematic study of laser-generated equimolar CrMnFeCoNi nanoparticles, focusing on structural differences, arising from varying pulse durations during synthesis in organic solvents (acetone, ethanol, acetonitrile). In a systematic experimental series using high-resolution transmission electron microscopy, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy, selected-area electron diffraction, X-ray diffraction, electron energy loss spectroscopy, in situ heating, post-irradiation experiments, and differential scanning calorimetry we demonstrate that a pulse-duration-driven structural difference occurs during laser ablation in liquid is observable to the three utilized solvents. While picosecond-pulsed laser ablation in liquid produces polycrystalline HEA NPs, nanosecond-pulsed laser ablation favors a metastable amorphous structure. Particle cores in all cases exhibit a homogeneous distribution of the metals Cr, Mn, Fe, Co, and Ni, while particle shells were found to vary between manganese-enriched oxide layers and thin graphitic carbon coatings. The discovery of the structure-directing mechanism allows one to select between crystalline or amorphous HEA NP products, simply by choice of the laser pulse duration in the same, well-scalable setup, giving access to colloidal particles that can be further downstream processed to heterogeneous catalysts or magnets. In that context, the outstanding temperature stability up to 375 °C (differential scanning calorimetry) or 500 °C (transmission electron microscopy) may motivate future application-relevant work.

In this study, we employed traditional methods and deep learning models to improve resolution and quality of low-resolution AFM images made under standard ambient scanning. Both traditional methods and deep learning models were benchmarked and quantified regarding fidelity, quality, and a survey taken by AFM experts. The deep learning models outperform the traditional methods and yield better results. Additionally, some common AFM artifacts, such as streaking, are present in the ground truth high-resolution images. These artifacts are partially attenuated by the traditional methods but are completely eliminated by the deep learning models. This work shows deep learning models to be superior for super-resolution tasks and enables significant reduction in AFM measurement time, whereby low-pixel-resolution AFM images are enhanced in both resolution and fidelity through deep learning.

Transmission X-ray microscopes (TXMs) are now increasingly used for quantitative analysis of samples, most notably in the spectral analysis of materials. Validating such measurements requires quantitatively accurate models for these microscopes, but current TXM models have only been tested qualitatively. Here we develop an experimental and theoretical framework for evaluation of TXMs that uses Mie theory to compute the electric field emerging from a nanosphere. We approximate the microscope's condenser illumination by plane waves at the mean illumination angle and the zone plate by a thin lens. We find that this model produces good qualitative agreement with our 3D measurements of 60 nm gold nanospheres, but only if both β and δ for the complex refractive index n = 1 - δ + iβ of gold are included in the model. This shows that both absorption and phase properties of the specimen influence the acquired TXM image. The qualitative agreement improves if we incorporate a small tilt into the condenser illumination relative to the optical axis, implying a small misalignment in the microscope. Finally, in quantitative comparisons, we show that the model predicts the nanosphere's expected absorption as determined by Beer's law, whereas the microscope underestimates this absorption by 10-20%. This surprising observation highlights the need for future work to identify the microscope feature(s) that lead to this quantitative discrepancy.

In this paper, comparative studies of selected properties of titanium dioxide (TiO₂) coatings deposited using electron beam evaporation (EBE) and ion beam-assisted deposition (IBAD) are presented. Post-process annealing at 800 °C was also conducted to examine its impact on the properties of the prepared coatings. After annealing at 800 °C, a transition from amorphous to the anatase phase occurred for all coatings. In particular, an increase in ion beam current led to a reduction in crystallite size by approximately 30% compared to coatings prepared by conventional EBE process. The average anatase crystallite size for annealed films was in the range of 30.8 to 43.5 nm. A detailed SEM analysis of surface morphology and cross sections revealed that the TiO₂ films prepared by IBAD had smaller, rounded grains and were denser compared to those deposited by EBE. Optical properties showed high transparency of 77-83% in the visible wavelength range for all as-prepared thin films. However, annealing caused a decrease of the transparency level by 32% for films deposited by EBE, while for films from the IBAD process the decrease was less than 10%. The use of an ion gun increased the hardness of the TiO₂ films from 2.4 to 3.5 GPa (I _ibg = 4 A). Although a similar relationship was observed for coatings after annealing, hardness values were lower than for as-deposited coatings. The most notable differences were observed in the abrasion tests, where the IBAD process significantly enhanced the abrasion resistance of the coatings. This research highlights the potential of IBAD to prepare dense, adhesive, and durable TiO₂ coatings with improved optical and mechanical properties, suitable for applications requiring enhanced wear resistance.

We prepared stable nanoparticle dispersions of metal complex phthalocyanines (MPcs; M = AlCl, Fe, Co, Zn) and Pt complex octaethylporphyrin (PtOEP) by nanosecond laser fragmentation of the corresponding microcrystalline powders in an aqueous solution of the amphiphilic polymer Pluronic^® F-127. All nanoparticles dispersed stably in phosphate-buffered saline and cell culture media without any precipitation for longer than one week. The aqueous F-127 solution at 0.1 wt % concentration, which is about one tenth of the critical micelle concentration, was enough to fabricate nanoparticles with excellent dispersion stability and high production efficiency. We examined the photosensitized generation of reactive oxygen species by AlClPc, ZnPc, and PtOEP nanoparticles and the photocytotoxicity for PC12 and HeLa cells, and demonstrated that the nanoparticles can be used as photosensitizers for photodynamic therapy.

Graphene oxide (GO) is expected to be one of the most promising adsorbents for metal ions, including radioactive nuclides in aqueous solutions. Large-area and single-layer graphene oxide (SLGO) grown on α-Al₂O₃(0001) was used as a model structure of GO since the aggregation and re-stacking of the GO sheets prevent the adequate analysis of the adsorption state. The SLGO film was obtained by oxidizing monolayer graphene grown by metal-free chemical vapor deposition on the α-Al₂O₃(0001) surface, and the adsorption state was determined by surface analytical techniques. It was clarified that Cs adsorbs on oxygen functional groups by substituting with H atoms from carboxyl and hydroxy groups. It is also estimated that the weight adsorption capacity of SLGO in the 1.0 mol/L-Cs aqueous solution is as much as approximately 70 wt %. It has been demonstrated that GO has great potential to be a promising adsorbent for Cs in aqueous solutions.

Bone tissue, also known as bone, is a hard and specialized connective tissue consisting of various bone cells. Internally, it has a honeycomb-like matrix providing rigidity to the bone and a piezoelectric feature contributing to bone remodeling. Bone remodeling is a crucial process involving osteoblastic replacement and resorption by osteoclastic cells to maintain structural integrity and mechanical properties of the bone tissue as it grows. However, in cases of fracture or degeneration, the natural self-regeneration process or inherent piezoelectricity of the body may not be sufficient to repair the damage. To address this, the use of piezoelectric nanomaterials (NMs) in bone tissue engineering was investigated. In this study, the influence of the piezoelectric hexagonal boron nitrides (hBNs) and barium titanate (BaTiO₃) on human osteoblasts (HOb) was comparatively evaluated. The synthesized hBNs and purchased BaTiO₃ were used after their full characterization by imaging and spectroscopic techniques. The piezoelectric behavior of both NMs was evaluated using piezoresponse force microscopy (PRFM). During in vitro studies, the piezoelectricity of the NMs was stimulated with ultrasound (US) exposure. The results showed that the NMs are not cytotoxic at the concentrations tested and the migration ability and calcium deposit formation of the cells treated with the NMs and upon US exposure were significantly increased. These results demonstrate that the hBNs have the potential to accelerate bone tissue regeneration and promote bone healing. These findings offer a promising avenue for developing new therapies for bone-related injuries and conditions requiring significant bone remodeling.

The concept of nanoarchitecture, as a post-nanotechnology methodology, can be defined as the construction of functional materials from nanometer-sized units using a variety of materials processes. It is believed to be particularly well suited to the assembly of soft materials that exhibit flexible and diverse structures and properties. To demonstrate its effectiveness, this review takes typical soft materials, including liquid crystals, polymers, gels, and biological materials, as examples. The aims are to extract the properties that emerge from them and to highlight the challenges that lie ahead. The examples also illustrate the potential applications, including organic semiconductor devices, electrochemical catalysts, thin-film sensors, solar energy generation, plastic crystal electrolytes, microactuators, smart light-responsive materials, self-repairing materials, enzyme cascade sensors, healing materials for diabetic bone defects, and bactericidal materials. As can be seen from these examples, soft materials nanoarchitectonics offers a wide range of material designs, specific functions, and potential applications. In addition, this review examines the current state and future of soft materials nanoarchitectonics. As an overall conclusion, it is highly anticipated that soft materials nanoarchitectonics will continue to develop significantly in the future.