Biologically mediated nanoparticle (NP) synthesis offers a reliable and sustainable alternative route for metal NP production. Compared with conventional chemical and physical production methods that require hazardous materials and considerable energy expenditure, some microorganisms can reduce metal ions into NPs during standard metabolic processes. However, to be considered a feasible commercial option, the properties and inherent activity of bio-NPs still need to be significantly improved. In this work, we present an Escherichia coli-mediated synthesis method for catalytically active Pd-Fe NPs. The produced biogenic Pd-Fe NPs with varying Fe content were characterized using complementary analytical techniques to assess their size, composition, and structural properties. In addition, their catalytic performance was assessed by using standardized chemical reactions. We demonstrate that the combination of Pd with Fe leads to synergistic effects that enhance the catalytic performance of Pd NPs and make biogenic Pd-Fe NPs excellent potential substitutes for currently used catalysts. Briefly, the apparent rates for the model reaction of 4-nitrophenol reduction to 4-aminophenol catalyzed by Pd-based nanoparticles were as high as 0.1312 min-1 using bimetallic Pd-Fe NPs, which is far superior to the rates of monometallic Pd NPs counterparts. This study provides a feasible strategy for the synthesis of multimetallic Pd-based NPs using common microbial processes. It emphasizes the potential of biogenic Pd-Fe NPs as efficient and sustainable catalysts for hydrogenation reactions, offering an environmentally friendly synthesis for various applications, including wastewater treatment and the production of fine chemicals.

Superconductivity is a quantum-mechanical phenomenon with multiple technological applications among which is quantum computing. It is usually associated with metals and low temperatures, but theoretically was extended to room temperature, organic, and biological matter. To achieve room-temperature superconductivity, an unconventional mechanism in a system with reduced dimensionality is likely to be necessary. Experimental attempts in search for it are under the way. Here the experiments with microtubules, nanometerscale quasi one-dimensional structures abundant in the brain and nerve system are presented arguing that they are superconducting at the room temperature. Complementing data on electrical transport and magnetic measurements, the paper focuses on the magnetic flux quantization and Josephson effect revealed by the electromagnetic radiation coming from the connections of microtubules during the propagation of action potential in the axons of the nerve cells. A mechanism for such generation is suggested. It is argued that nanoscale superconductivity is responsible for the quantum processing of information in the living organisms, and the coherent Josephson radiation helps synchronizing their functions. The values of main parameters for the room-temperature superconductor are estimated and given in the paper. The interpretation of the behavior of microtubules in terms of room-temperature superconductivity could strengthen understanding of the quantum nature of biological systems.

Metal nanoparticles have attracted considerable attention due to their astounding potential for a wide range of commercial applications. From targeted drug delivery and antimicrobial agents to electronics, metal nanoparticles seem to have immeasurable prospects in all areas of science. However, modern industrial production frequently involves complex procedures, large amounts of energy, utilizes strong chemical solvents, or produces hazardous waste. Biological synthesis has been proposed as an alternative for simpler, inexpensive, and more eco-friendly metal nanoparticle production. Microorganisms possess multiple mechanisms to transport, regulate and bind metal ions that may result in the biosynthesis of nanoparticles. They can synthesize even complex bimetallic nanoparticles, which are difficult to produce with normal chemical and physical processes. A better understanding of bacteria-metal interactions might thus pave the way for a wide array of industrial applications. This review will summarize the current methods for metal nanoparticle synthesis, with a focus on the microbial (bio) synthesis of nanoparticles. We will describe the general mechanisms of bacteria-metal ion interactions, including cellular uptake and the subsequent reduction into nanoparticles. Protocols for the production of metal-based nanoparticles of relevant elements with different bacterial strains are compiled and the current challenges in bacterial synthesis of metal nanoparticles in the industry are discussed.

Microtubules are essential structural elements in living organisms, which form scaffolding of the cells and participate in transport of proteins and separation of chromosomes.They are highly ordered nanotubes built of two types of tubulin proteins and filled with water.It was suggested that additionally to the transport and mechanical functions, microtubules are crucial for the processing of information.Moreover, this processing is considered to be quantummechanical and even based on superconductivity.Previously, screening of magnetic field, which supports superconductivity, has been observed by magnetic force microscopy in the microtubules assembled from the mammalian tubulin.Here the study is extended to the fungal self-assembled microtubules.In spite of observed structural differences between the mammalian and fungal microtubules, both display full screening of magnetic field.The temporal scans reveal steady screening in the mammalian microtubules and a fluctuating screening in the fungal microtubules.The formation of links between the microtubules and their implication for the processing and transfer of information is discussed.

Niobium Nitrate (NbN) superconducting films are extensively used in superconducting electronics, for example as a basic element of single-photon microwave resonators. Here we report on direct visualisation of magnetic flux penetration into a NbN thin film deposited by High-Temperature Chemical Vacuum Deposition (HTCVD). The film is of the thickness of 90.8 nm. It is deposited at a temperature of 1200 °C on a single-crystal $\alpha\text{-Al}_{2}\mathrm{O}_{3}$ (0001) c-axis substrate (sapphire). The visualisation is done by Magneto-Optical imaging allowing to see directly distribution of magnetic flux in the superconductor. It is found that at low temperatures magnetic flux penetrates into the film in the form of dendritic flux avalanches. Moreover, the shape of dendritic avalanches appeared to be very unusual, previously not reported in the literature. The branches of avalanches persistently follow one specific direction in the plane of the film. To clarify the origin of this effect, high-resolution Scanning Electron Microscopy and Atomic Force Microscopy have been used in combination with the Fast Fourier Transform of the obtained images. It was found that the origin of the selected direction in the dendritic flux penetration is deep on the nanometre scale, namely in nano-channels formed by the merging NbN crystallites during their growth. In this way, nanostructure of the film directly controls dendritic flux avalanches in the superconductor. Varying conditions of deposition would allow actively changing superconducting properties of the films.

High-Entropy Alloys (HEAs) are recently introduced materials consisting of numerous-at least five-elements in nearly equal-atomic concentrations. Studying them, previously unexplored phase fields in multidimensional phase diagrams are now being explored. The HEA concept is based on a thermodynamic balance between mixing entropy and enthalpy, which defines values of several critical parameters that determine the formation of simple or complicated phases. Physical properties, like magnetism, are of great interest for these materials, even though they have not been extensively analyzed so far. Particularly, the exploration of the magnetic domain structure and its correlation with the micro- and nano-structural features of the materials is of high scientific value. In this work, we study the influence of the magnetic history on the alteration of the magnetic domain patterns in polycrystalline FeCoNiAl 0.9 Mn 0.9 High Entropy Alloy (HEA). For the study, we introduce a combinatorial method of Electron Backscatter Diffraction and Magnetic Force Microscopy imaging, which reveals specific magnetic domain structures in the grains of different crystallographic orientations. It is found that in the HEA polycrystal, an increase of the applied magnetic field affects the formation of magnetic domains and leads to a transition from a labyrinth-like pattern to a dotted domain configuration, which is expressed differently in the differently oriented grains.

With mounting evidences of superconductivity in brain microtubules, a key experiment to support its existence would be a nanometer-scale mapping of microtubule magnetic properties. Magnetic force microscopy is a convenient instrument to perform such mapping. Previously, it has been used qualitatively resulting in the detection of strong diamagnetic response coming from the in-plane bundles of microtubules. This was preliminary associated with the feature of ideal diamagnetism and therefore superconductivity in the microtubules. Numerical arguments, however, were absent and it was unclear in what substance superconductivity resides. In order to clarify this, magnetic force microscopy was extended to force spectroscopy, which records magnetic signal as function of distance from the surface. Moreover, the spectroscopy was performed on cross-sections of microtubules investigating them individually. In order to do this, a special technique of sample preparation has been developed allowing orienting microtubules perpendicular to the substrate. The magnetic mapping revealed strong diamagnetism coming from the inside of microtubules. The analysis of recorded force curves has been performed analytically separating magnetic and van der Waals contributions to the signal. Following this, estimation of the signal expected for ideal diamagnetism has been obtained and compared with the signal coming from the microtubules. It is concluded that microtubules display property of ideal diamagnetism. The substance, in which superconductivity develops, is likely to be structured water.

Palladium (Pd) is a key component of many catalysts. Nanoparticles (NPs) offer a larger surface area than bulk materials, and with Pd cost increasing 5-fold in the last 10 years, Pd NPs are in increasing demand. Due to novel or enhanced physicochemical properties that Pd NPs exhibit at the nanoscale, Pd NPs have a wide range of applications not only in chemical catalysis, but also for example in hydrogen sensing and storage, and in medicine in photothermal, antibacterial, and anticancer therapies. Pd NPs, on the industrial scale, are currently synthesized using various chemical and physical methods. The physical methods require energy-intensive processes that include maintaining high temperatures and/or pressure. The chemical methods usually involve harmful solvents, hazardous reducing or stabilizing agents, or produce toxic pollutants and by-products. Lately, more environmentally friendly approaches for the synthesis of Pd NPs have emerged. These new approaches are based on the use of the reducing ability of phytochemicals and other biomolecules to chemically reduce Pd ions and form NPs. In this review, we describe the common physical and chemical methods used for the synthesis of Pd NPs and compare them to the plant- and bacteria-mediated biogenic synthesis methods. As size and shape determine many of the unique properties of Pd NPs on the nanoscale, special emphasis is given to the control of these parameters, clarifying how they impact current and future applications of this exciting nanomaterial.

We report the first nanoscale investigation of FeCoNi(AlMn)(x) high-entropy alloys (HEAs) processed by laser metal deposition. The structural evolution of the alloy upon chemical composition variation (0.2 <= x <= 1.5) was investigated by combining imaging and spectroscopies in (scanning) transmission electron microscopy (S)TEM with density functional theory (DFT). A gradual change from a face-centered cubic (FCC) towards an ordered full-Heusler (L2(1)) phase by increasing the Al and Mn contents was observed. Direct imaging and atomic-scale calculations revealed a nanoscale interplay between B2 and L2(1) ordered structures for x = 1.5, wherein the latter, Al and Mn occupy two different Wyckoff sites. By decreasing x, the FCC phase dominates exhibiting intense phase separation tendency, ordering phenomena, and nano-precipitation. Although not chemically discriminated, plasmon-peak splitting in low-loss electron energy loss spectra revealed the presence of two valence electron densities within the FCC phase. Lorentz TEM showed that the ordered nano-precipitates and nano-sized grains with a structure based on a tripled FCC unit cell are pinning-sites for magnetic domain walls and dislocations. All alloy compositions exhibited soft-magnetic behavior with coercivity (H-c) values < 1000 A/m. The FeCoNi(AlMn)(1.5) alloy with L2(1)/B2 nanostructure showed the highest magnetization (M-s) with relatively low H-c, attributed to the large magnetic moment of Mn and the synergistic effect of Mn-Al according to DFT, whilst ordering does not impose a negative effect. Phase separation trends within the FCC phase seem to decrease the M-s however, the overall impact on the magnetic behavior is not intense, opening up for new avenues for tuning FeCoNiAlMn properties through chemically designed phase decomposition regimes. (C) 2022 The Author(s). Published by Elsevier B.V.

Hydrogen as an energy carrier is a promising alternative to fossil fuels, and it becomes more and more popular in developed countries as a carbon-free fuel. The low boiling temperature of hydrogen (20 K or −253.15 °C) provides a unique opportunity to implement superconductors with a critical temperature above 20 K such as MgB2 or high-temperature superconductors. Superconductors increase efficiency and reduce the loss of energy, which could compensate for the high price of LH2 to some extent. Norway is one of the pioneer countries with adequate infrastructure for using liquid hydrogen in the industry, especially in marine technology where a superconducting propulsion system can make a remarkable impact on its economy. Using superconductors in the motor of a propulsion system can increase its efficiency from 95% to 98% when the motor operates at full power. The difference in efficiency is even greater when the motor does not work at full power. Here, we survey the applications of liquid hydrogen and superconductors and propose a realistic roadmap for their synergy, specifically for the Norwegian economy in the marine industry.

Being biological object, microtubules attract significant attention in physics, since it is believed that they are responsible for quantum processing of information in the brain. There were, however, no direct experiments checking such a statement. Recently, strong advancement in quantum computing took place utilizing properties of superconductors at low temperatures. Following this progress, it was proposed that brain microtubules are superconducting at room temperature allowing quantum processing of information. Moreover, the evidence of room-temperature superconductivity in brain slices containing microtubules was obtained by electrical transport measurements, and even specific scenario of quantum processing in the microtubules has been suggested. These results, however, are not yet accepted by the scientific community as there are no known attempts to reproduce them. Another step in proving superconductivity would be confirming ideal diamagnetism of microtubules, since ideal diamagnetism is more fundamental property of superconductivity than perfect conductivity, some features of which were seen indirectly, or the existence of energy gap, which was already confirmed by the transport measurements. Here brain microtubules are examined by the magnetic force microscopy. The evidence of strong diamagnetism and its sensitivity to the water content in the microtubules is obtained. This gives another strong argument in favor of the concept suggesting superconductivity-based quantum processing of information in living organisms.

Superconductors application can lead to significant economic benefits, especially in combination with use of liquid hydrogen, which is becoming an important part of the renewable energy economy. While many traditional superconductors cannot operate in liquid hydrogen, new materials, like high-temperature superconductors and MgB2 perfectly suit this purpose. YBa2Cu3Ox is one of the most used high-temperature superconductors. It can operate even in liquid nitrogen, at the temperature of 77.3 K, but has a strong advantage of enhanced critical current density at the boiling temperature of liquid hydrogen of 20 K. A disadvantage of this material is the absence of natural c-axis pinning centers defining its critical current density. A usual way to solve this problem is the introduction of artificial pinning centers in the form of nanoparticles. The nanoparticles, however, reduce the volume of the superconductor and can lead to the formation of high-angle grain boundaries detrimental for the critical current. Here we explore an approach of depositing magnetic nanoparticles on the surface of superconducting films, which neither reduce the volume of the superconductor nor create high-angle grain boundaries. The additional pinning by these nanoparticles is studied by recording magneto-optical images of the films.

High-Entropy Alloys are advanced technological materials composed of several (typically five) elements in nearly equal atomic concentration. By forming these alloys, previously unknown phase fields of multidimensional phase diagrams are explored. The large number of possible substitutions of constituent elements on crystal lattice sites justifies the dominant contribution of mixing entropy over enthalpy to the free energy reduction. This leads to the formation of phases, which otherwise could not be formed in alloys with fewer main alloying elements. Here we explore magnetic and compositional properties of a High-Entropy Alloy, namely FeCoNiAl x Mn x (0.05 ≤ x ≤ 3.08), composed of magnetic (Fe, Co, Ni) and non-magnetic elements (Al, Mn). By magnetic force microscopy of a selected area, it is observed that for intermediate to low Al and Mn contents, the alloy splits in two major crystallographic phases with different magnetic properties. Elemental maps of the same area were recorded with energy dispersive spectroscopy and scanning electron microscopy. Counterintuitively, it was found that the phase rich in non-magnetic Al has stronger magnetism than the phase rich in Fe. This work showcases possible applications of the here presented HEAs as soft magnetic materials in functional magnetic elements.

Palladium (Pd) is a scarce metal, which is able to catalyze a variety of important chemical reactions. In the bulk form, Pd is anomalous paramagnetic, but in the form of nanoparticles, it has been reported as ferromagnetic. Detecting the magnetism of Pd nanoparticles is, however, difficult due to their reduced dimension. In addition, the ferromagnetic nature is a size-dependent property and, for Pd, the strength of magnetism decreases with slight increments in size. A "green" methodology for the preparation of small Pd nanoparticles was followed in this study. It is based on the ability of bacteria to take up Pd 2+ ions from its surrounding solution and to enzymatically reduce it to metallic Pd 0 nanoparticles. The efficiency of the production can be determined by transmission electron microscopy and, as a new technique, magnetic force microscopy. Notwithstanding, the study of nanoparticles of the size of just a few nanometers with these techniques is still difficult. Here we present a methodology for the enhancement of the magnetic signal of biologically produced Pd-based nanoparticles through the decoration of Escherichia coli bacteria cross-sections with Fe nanoparticles. This methodology allows the visualization of bacteria that are loaded with magnetic nanoparticles even when conventional transmission electron microscopy has difficulties to resolve them inside the microorganisms.

We report a novel doping strategy for YBa2Cu3O7-x (YBCO) superconducting films by using a positive mismatch, Ba2YNbO6 (BYNO), and a negative mismatch, LaAlO3 (LAO), simultaneously. Double doping can significantly reduce the c-strain in the YBCO film by canceling the strain between the two dopants. By systematically optimizing the doping amount of both BYNO and LAO, it was found that BYNO and LAO do not act equally. The microstructure and distribution of both BYNO and LAO were investigated with magneto-optic microscopy and scanning electron microscopy. The effect of BYNO and LAO on pinning was confirmed. The results of this study will help select appropriate positive mismatch and negative mismatch dopants, which is fundamental to the design and fabrication of pinning centers to fit different application scenarios.

With the advance of superconducting quantum computing and the attempts of extending its operating range to higher temperatures, a special attention is paid to nanostructured quantum circuits. In particular, quasi one-dimensional quantum wires with phase slip centers are argued to be promising structures for the next generation of quantum computers. In its turn, this stimulates revisiting the question about the possibility of quantum processing of information in quasi one-dimensional structures in the nervous system, specifically the brain, in living organisms, especially in the light of recent findings that suggest robust room-temperature superconductivity in these structures. The early theories of superconductivity were in favor of its quasi one-dimensional nature, and the recent findings suggest that reducing dimensions of a system could be a good approach for increasing the critical temperature of a material. Here, based on experimental data, it is argued that both room-temperature superconductivity and quantum processing of information are possible in the microtubules that are abundant in the nervous system and form the scaffolding of every cell in advanced living organisms. The origin of superconductivity in microtubules, and the way in which quantum processing of information may take place in them, are discussed. The role of Josephson oscillations in processing and exchange of information is emphasized.

Scaling behaviour of dynamically driven vortex avalanches in superconducting YBa 2 Cu 3 O 7− δ films deposited on tilted crystalline substrates has been observed using quantitative magneto-optical imaging. Two films with different tilt angles are characterized by the probability distributions of avalanche size in terms of the number of moving vortices. It is found in both samples that these distributions follow power-laws over up to three decades, and have exponents ranging between 1.0 and 1.4. The distributions also show clear finite-size scaling, when the system size is defined by the depth of the flux penetration front – a signature of self-organized criticality. A scaling relation between the avalanche size exponent and the fractal dimension, previously derived theoretically from conservation of the number of magnetic vortices in the stationary state and shown in numerical simulations, is here shown to be satisfied also experimentally.

Bioinspired metal-based nanoparticles have potential uses in many applications, but before possible commercial exploitation, it is essential to clarify the pathways of their production and deposition inside the organisms, for example, in bacteria. The technique of magnetic force microscopy (MFM) could be used to evaluate the nanoparticles' magnetic properties, in addition to allowing tracing their location inside or outside of bacteria, which could help to understand pathways of their biosynthesis. In this work, using MFM and analyzing the interaction of magnetic tip with nanoparticles and bacteria imbedded in resin at different heights above the surface, and comparing gradients of forces recorded by magnetic and non-magnetic tips, a condition was found, which allows measuring the pure magnetic response of Pd-Fe nanoparticles. For these nanoparticles, the interplay between magnetic and van der Waals forces is described at small distances to the surface. Experimental data are compared with simulations, based on the calculation of the distribution of the magnetic field around a nanoparticle, which defines magnetic force acting on the MFM tip.

Anomalous resistive and magnetic behavior of GdOH thin films, which belong to the novel class of materials known as oxyhydrides, is reported. The oxyhydrides contain hydrogen in its rare negatively-charged anion state in combination with oxygen, which is also in the anion state. A range of GdOH films prepared on glass and single-crystalline substrates demonstrate a resistive transition from an insulating to conducting state with decrease of resistance starting as high as at about 200 K. At room temperature, the resistance per square area for the best GdOH films of the thickness of 200 nm is about 100 Ω, which is close to the resistance of the films of high-temperature superconductors of similar thickness. Apparent zero resistance is observed at about 40 K. Magneto-optical imaging registers effect of trapping magnetic flux typical for the superconducting state. The possible anion superconductivity is discussed in connection with recently published papers on near-room-temperature superconductivity in hydrides at high pressure and hydrogen-based superconductivity in biological systems.

Magnetic properties of High-Entropy Alloys based on the Fe-Co-Ni-Al-Mn system are reported. High-Entropy Alloys are cutting-edge technological materials containing five or more elements in relatively high concentrations (5-35 at.%) within one or several solid-state solutions. These solutions are stabilized at the nanometer scale due to the increased contribution of the mixing entropy to the Gibbs free energy, which can overcome the enthalpic contribution. Two magnetic alloys are found in FeCoNiAl x Mn x (1.6 at.% ≤ x ≤ 7.8 at.%) samples processed by laser metal deposition. The magnetic techniques used to screen the materials were magneto-optical imaging and magnetic force microscopy. The former allows characterizing magnetic properties within the mm-μm scale, while the latter is efficient down to the nanometer scale. Magnetic screening confirms the importance of the nanostructure in defining the alloys' magnetic properties, and the trends in the magnetic behavior as a function of the alloy composition are revealed. The experimental results suggest that it is possible to form unique alloys, which may outperform conventional magnetic materials used in various applications such as transformers, screening shields, and wind power generators.