Bimetallic CuZn (brass) nanoparticles are key materials in catalytic applications, yet access to the full compositional range remains challenging using conventional wet chemical synthesis. In this study, we demonstrate the physical synthesis of CuZn nanoparticles across a broad compositional range using spark ablation of alloyed feedstocks (Cu25Zn75, Cu50Zn50, Cu75Zn25). In spark ablation, the nanoparticles are formed directly in the gas phase without the need for post-synthesis treatments and exhibit complete internal mixing, as confirmed by (scanning) transmission electron microscopy ((S)TEM) and energy-dispersive X-ray spectroscopy (EDS). A pronounced evolution over time in nanoparticle composition was observed during continuous generation. To elucidate the underlying mechanisms, a comprehensive set of advanced, time-resolved characterization techniques was employed, including X-ray fluorescence (XRF) of deposited nanoparticles, optical emission spectroscopy (OES) of the spark plasma, in-flight inductively coupled plasma mass spectrometry (ICP-MS), and in-flight X-ray photoelectron spectroscopy (XPS). These complementary characterization methods reveal a gradual compositional evolution linked to changes at the feedstock surface rather than post-formation processes. The results indicate that preferential Zn evaporation governs the temporal evolution of the nanoparticle composition, followed by the establishment of a dynamic steady state during prolonged sparking. Based on the experimental observations, a qualitative mechanism supported by a simple ablation model is proposed to explain the compositional evolution in CuZn spark ablation. Despite the large differences in thermophysical properties between Cu and Zn, a broad Cu-Zn compositional range can be accessed, with stable nanoparticle compositions achieved upon extended operation. This work provides insight into bimetallic nanoparticle formation via spark ablation and how tunable alloy compositions can be achieved via gas-phase synthesis, with direct relevance for catalytic and other composition-sensitive applications.

Air pollutants, such as particulate matter, are known to contribute to disease in humans, but their impact on wildlife remains understudied. A contributing factor to this health impact is the fraction of inhaled particles depositing in the respiratory system. Compared to humans, birds are equipped with a very different respiratory system, which may render them more or less susceptible to air pollution. Although evidence for adverse pollution effects in birds has emerged, little is known about particle dynamics inside the avian lungs. To elucidate this, we exposed zebra finches (Taeniopygia guttata) to ambient-like ultrafine model particles under controlled conditions and quantified deposition in the lungs and, in a smaller subset, also the heart, liver and red blood cells. Birds were exposed to 50 or 100 nm particles at air temperatures of 5 or 25 °C, all of which fall within environmentally relevant exposure conditions. Lung deposition was highest for the smallest particles, in line with the size dependence of particle diffusion rate. While deposited fraction in the lung remained unaffected, deposited dose rate (DR) increased at the lower temperature, indicating that the effect was driven solely by elevated minute ventilation (oxygen consumption). Particle clearance measurements 2 weeks after exposure revealed that 44% of the initially deposited 100 nm particles remained in the avian lungs. We found no evidence that particles translocated to the heart, liver or red blood cells in the analyzed subsets. These findings provide an ecologically relevant foundation for understanding particle exposure dynamics in an avian model and support future work assessing health effects of particulate pollution in birds.

Pd-Ga alloy nanoparticles with tunable compositions were produced by combining spark ablation with a downstream injection of a metal-organic precursor. This dual-process approach enables control over nanoparticle composition and morphology by adjusting precursor flow rate and sintering temperature. At lower precursor flows, uniform Pd-Ga nanoparticles form, exhibiting stable Pd5Ga2 and Pd2Ga phases. HRTEM and STEM-EDX analyses reveal that as precursor supply increases, Ga incorporation intensifies, leading to structural transitions, phase segregation, and the formation of PdGa dominated phases with amorphous Ga-rich domains, influencing nanoparticle shape and crystallinity. This process unlocks pathways for tailoring alloy compositions inflight with low-melting point materials.

We present a synthesis route for solid-state nanocatalysts composed of gallium phosphide nanowire supports decorated with catalytic palladium nanoparticles. Through precise control of fabrication conditions, we were able to tune the nanowire morphology, density, and crystal structure. The resulting catalysts were highly active and selective in the partial hydrogenation of phenylacetylene to styrene. Size-selected palladium nanoparticles deposited in the aerosol form primarily settle on the upper sidewalls of tapered nanowires, retaining crystallinity and shape. Adjustable nanocatalyst fabrication conditions allow tuning of surface wettability. Hydrophobic, low-density nanocatalysts show enhanced activity in hydrogenation reactions. Exploring these fabrication parameters enables a tailored design of heterogeneous nanocatalysts and provides insights into the critical factors influencing their functionality.

Abstract Nanogenerators are significant in the era of the emerging biodegradable energy harvesting systems, Internet of Things (IoT) application and wearable gadgets, where battery replacement and external power supply are challenging. The rise in energy demand coupled with concerns regarding environmental contamination caused by fossil fuel-based energy generation has spurred research and development of novel sustainable methods for energy harvesting. Nanogenerators increase the operational life of IoT devices by providing sustainable power source. Various nanogenerators like the piezoelectric nanogenerator, triboelectric nanogenerator, thermoelectric nanogenerator, pyroelectric nanogenerator and hybrid nanogenerator are used for sophisticated detection of systems in various fields that are small, inexpensive and environmentally benign. Generally, the choice of a nanogenerator depends on its intended application and the environment in which it will operate. Due to high output and different applications in different conditions and frequency ranges, triboelectric nanogenerators are extensively investigated. Piezoelectric nanogenerators have properties that are well-suited for wearable electronics and environmental sensing. Various studies have reported nanogenerators with high open-circuit voltages of 18 kV, 10 kV, 753 V and 578 V. and short-circuit currents of 348, 320 and 63.3 μA. Nanogenerator also have high operational lifetimes of 3,960,000, 1,260,000, 860,000 and 90,000 cycles. This review presents a comprehensive analysis of the state-of-the-art in green energy technologies focusing on the cutting-edge advancements in nanogenerator principles, simulations, material selection and applications in the emerging field of nanoscale energy conversion.

Metal nitride and metal oxide nanoparticles (NPs) provide key material components for a number of applications due to their unique properties. Here we demonstrate that spark ablation of metallic electrodes, quenched with a pure N2 flow at atmospheric pressure, can be used as a reactive generator to synthesize metal nitride, metal oxide or pure metallic NPs depending on the material. The composition of the synthesized NPs was determined through their crystal structure using X-ray diffraction and transmission electron microscopy (TEM). Our results show that the composition of the resulting NPs strongly depends on the electrode material: Ti and Al form mixtures of metal nitride and oxide NPs, whereas Mg and Pd produce respectively only oxide and pure metallic NPs. Repeated XRD measurements of the samples after exposing them to ambient air over periods of several months showed that the stability of TiN was higher compared to that of the AIN NPs, with the first being converted to TiNyOx and the latter to gamma-Al2O3 after 9 months.

Metal oxide nanoparticles are widely used in catalysis, photovoltaics, and gas sensing, where surface structure and oxidation state strongly influence performance. This work investigates how carrier gas composition, combined with in-flight heating, can be used to control the surface properties of metal oxide nanoparticles generated via the gas-phase method, spark ablation. Sn, Zn, and Al nanoparticles were characterized using in-flight X-ray photoelectron spectroscopy (XPS) at the MAX IV synchrotron radiation facility, enabling near real-time measurement of suspended particles under oxidizing (N2 + O2), inert (N2 and Ar), and potentially reducing (N2 + H2 and Ar + H2) gas environments, without introducing potential changes associated with particle deposition and storage. To support the interpretation of the XPS results, the particle size distributions, spark energy and frequency, and compaction behaviour were studied, providing insight into how material properties and generation conditions affect surface chemistry. The XPS results show that for Sn nanoparticles, surface oxidation state can be tuned from SnO2 to SnO and metallic Sn by selecting appropriate carrier gas and in-flight heating temperature. For Zn, the carrier gas primarily determines the surface composition, while heating has only a minor influence on the balance between ZnO, oxygen-deficient ZnOx, and metallic Zn on the surface. In contrast, the surface oxide of Al nanoparticles remains largely unaffected by both carrier gas and in-flight heating. These findings demonstrate how careful control of carrier gas and in-flight thermal processing can be used to tailor nanoparticle surface properties, providing a pathway for designing materials optimized for specific applications.

The optical response of gold-silver (Au-Ag) alloy nanoparticles is strongly influenced by their localized surface plasmon resonance (LSPR), which can be tuned by varying the particle composition. Accurate simulation of LSPR, often performed using Mie theory, critically depends on the choice of dielectric function, yet available datasets for gold, silver, and their alloys vary widely. In this work, we aim to demonstrate how different dielectric functions lead to discrepancies in simulated LSPR wavelengths, even for pure metals. By using numerical simulation tools, such as PyMieLab and the miepython library, we systematically evaluate commonly used dielectric models for Au-Ag alloys by comparing their predicted LSPR wavelengths with experimental measurements obtained from spark-ablation-generated nanoparticles with well-defined compositions and narrow size distributions. The composition-dependent experimental LSPR data - obtained for the whole composition range between pure silver and gold - provides a reliable benchmark for assessing the accuracy of each model. Our results highlight the potential uncertainty introduced by different dielectric functions and help to identify a model which describes experimental data the best. The results underline the importance of dielectric model selection for predictive optical simulations of alloy nanoparticles.

[This corrects the article DOI: 10.1021/acsanm.5c00144.].

Binary nanoparticles (BNPs), composed of two distinct materials, offer tailored properties advantageous for various applications, including enhanced catalytic, magnetic, and optical behavior. Among the synthesis methods for BNPs, spark ablation stands out for its capability to produce multicomponent nanostructures with tunable compositions. This study investigates the mixing dynamics of material vapors in spark ablation, a critical step in the process of BNP formation. Using spatially and temporally resolved optical emission spectroscopy (OES), we track the expansion and interaction of gold and silver vapors within the spark gap of a spark discharge generator. The collected data reveal the evolution of the vapor mixing process, complemented by a quantitative model that maps the variation of the gold-to-silver concentration ratio over time and space. We correlate these observations with the composition distribution of synthesized AuAg BNPs, as analyzed by scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectrometry (EDX). Our findings elucidate key factors influencing the compositional variance of BNPs, facilitating the understanding of the role of vapor mixing in achieving well-controlled particle processes via spark ablation.

Magneto-responsive soft films constitute a fascinating class of smart materials and devices capable of performing various tasks, such as micromanipulation or transport, noninvasive surgery, and sensing. These components are fabricated by incorporating magnetic materials into flexible substrates. In this context, arranging magnetic particles into elongated chains exhibiting shape anisotropy has shown great potential. Here, we introduce a novel technique for fabricating magnetically responsive films using continuous single-step production and self-assembly of magnetic nanoparticles from a carrier gas at atmospheric pressure into anisotropic magnetic structures directly onto flexible polymer layers. We show that the resulting magnetic soft films exhibit significant residual magnetization and a large response to external magnetic fields. Furthermore, we investigate the magnetic properties of the nanoparticle assemblies and show that interparticle interactions play a critical role in determining the final magnetic properties of the nanostructures. Moreover, we provide experimental evidence that fusing the nanoparticles via post-annealing results in a transition from magnetostatic to exchange interactions with an ≈50% increase in the coercivity.

Engineering on the nanoscale often involves optimizing performance by designing and creating new types of nanostructured materials. Multifunctional nanoparticles can be formed by combining elements that carry fundamentally different properties. The elements can be chosen based on the desired functionality, and by combining, e.g., magnetic, and catalytic elements, it is possible to self-assemble nanoparticles into catalytically active magnetic nanochains. However, mixing and assembling nanoparticles in a controlled way is challenging, and it is not obvious how the intermixing of the elements influences the properties of the individual nanoparticles. In this work, we synthesize and assemble intermixed magnetic and catalytic Cobalt-Palladium (Co-Pd) nanoparticles into multifunctional nanochains. The magnetic behavior is explored by studying the magnetic field-directed self-assembly of the nanoparticles into elongated nanochains. The catalytic properties are determined by measuring CO oxidation at elevated temperatures. Our results confirm that the magnetic and catalytic functionalities of the individual elements are retained when intermixed, which implies the potential to create nanochains with dual functionality that can be assembled in a controlled way.

Metal oxide nanoparticles are essential in various applications, and the synthesis through gas-phase generation methods offers a rapid and reliable pathway for nanoparticle production. Yet achieving precise control over their formation remains challenging due to the complex nature of oxidation processes. While bulk oxidation states can be assessed via off-line measurements, the dynamic nature of surface oxidation is more difficult to monitor and optimize in real time. Here, we investigate the surface oxidation state of unsupported tin oxide nanoparticles using an aerosol sample-delivery system and in-flight X-ray photoelectron spectroscopy. This powerful method allows the continuous monitoring of the surface oxidation of the gas-phase generated nanoparticles in real time, avoiding uncertainties associated with postcollection alterations. Tin oxide nanoparticles are widely used in gas sensing and catalytic applications, where the surface oxide layer plays a crucial role in determining their performance. Our findings demonstrate how the surface oxidation state of the free-flying particles can be controlled by adjusting the carrier gas composition, in-flight heating temperature, and particle composition. Specifically, the surface oxides of tin are partially reduced when heated in a slightly reducing atmosphere, and the reduction is further enhanced by forming mixed tin-gold nanoparticles. While previous studies on metal oxide nanoparticles have focused predominantly on bulk properties or off-line analysis, this study employs real-time in-flight X-ray photoelectron spectroscopy to investigate details of the surface oxidation state. Understanding the surface oxidation of metal oxide nanoparticles is essential to optimize processes, such as in-flight coating or subsequent deposition into a protective environment. This approach enables the exploration of direct correlations between generation conditions and surface properties, providing valuable insights into optimizing gas-phase nanoparticle synthesis.

Nanochains (NCs) made up of a one-dimensional arrangement of magnetic nanoparticles (NPs) exhibit anisotropic properties with potential for various applications. Herein, using a novel self-assembly method we directly integrate single NCs onto desired substrates including devices. We present a nanoscopic analysis of magnetization reversal in 1D linear NP arrays by combining x-ray microscopy, magnetoresistance (MR), and micromagnetic simulations. Imaging the local magnetization along individual NCs by scanning transmission x-ray microscopy and x-ray magnetic circular dichroism under varyingin situmagnetic fields shows that each structure undergoes distinct non-homogeneous magnetization reversal processes. The experimental observations are complemented by micromagnetic simulations, revealing that morphological inhomogeneities critically influence the reversal process where regions with parallel chains or larger multi-domain particles act as nucleation centers for the magnetization switching and smaller particles provide pinning sites for the domain propagation. Magnetotransport through single NCs reveals distinct MR behavior that is correlated with the unique magnetization reversal processes dictated by the morphology of the structures. This study provides new insights into the complex magnetization reversal mechanism inherent to one-dimensional particle assemblies and the effective parameters that govern the process.

Magnetic one-dimensional structures are attractive nanomaterials due to the variety of potential applications they can provide. The fabrication of bimetallic 1D structures further expands the capabilities of such structures by tailoring the magnetic properties. Here, a single-step template-free method is presented for the fabrication of 1D FeCo alloy nanochains. In this approach, charged single-crystalline FeCo nanoparticles are first generated by the co-ablation of pure Fe and Co electrodes under a carrier gas at ambient pressures and attracted to a substrate using an electric field. When reaching the surface, the particles are self-assembled into parallel nanochains along the direction of an applied magnetic field. The approach allows for monitoring the self-assembly particle by particle as they are arranged into linear 1D chains with an average length controlled by the deposited particle concentration. Magnetometry measurements revealed that arranging nanoparticles into nanochains results in a 100% increase in the remanent magnetization, indicating significant shape anisotropy. Furthermore, by combining x-ray microscopy and micromagnetic simulations, we have studied the local magnetization configuration along the nanochains. Our findings show that variations in magnetocrystalline anisotropy along the structure play a crucial role in the formation of magnetic domains.

AbstractVapor–solid–solid (VSS) growth of III‐V semiconductor nanowires (NWs) has long been considered an alternative for the vapor–liquid–solid (VLS) growth mode, with the potential to avoid the incorporation of deep‐level impurities into semiconductors and to form compositionally abrupt interfaces. Most research however indicates that VSS growth has a much lower growth rate than observed in the VLS growth regime, explained by the very slow mass transport at the solid seed particle‐NW interface. In this study, the direct observation of the VSS growth of GaP NWs under different mechanisms is reported, by using Ni as a seed material inside an environmental transmission electron microscope. These results reveal that when NWs are grown from seed particles exhibiting the NiGa and Ni2Ga3 phases, classic VSS growth occurs with slow NW growth and interface diffusion as the dominant mass transport pathway. In contrast, when NWs are grown by seed particles containing Ni2P phase, rapid NW growth is observed together with a continuous reshaping of the seed particle. A cation exchange reaction is proposed as the predominant growth mechanism. This research results demonstrate an entirely new variant of the VSS growth mode, opening up new degrees of freedom for tuning NW properties.

Segregated bimetallic nanoparticles like core-shell nanoparticles are of interest in various fields including biomedicine, catalysis, and optoelectronics. Aerosol technology is an optimal platform to control nanoparticle size, structure, and composition, which are some of the most important parameters tuning the material performance for the intended applications. Here, we develop a novel evaporator design to coat core particles on-line with a shell directly in the gas phase. The evaporator employs a local heater that decouples heating the evaporating material from the aerosol particles to limit core-shell alloying. We characterize the system by evaporating Zn onto core particles of Au, Sn, and Bi and demonstrate the core-shell particle formation with controllable shell thickness in each material system. We discuss simple models to explain the observed growth process inside the evaporator and the resulting shell formation.

Multimetallic nanoparticles possess a variety of beneficial properties with potential relevance for various applications. These metallic nanoparticles can consist of randomly ordered alloys, which retain the properties of the constituting elements, or ordered intermetallics, which possess extended properties. Depending on the desired application, specific alloys or intermetallic compounds are required. However, it remains challenging to achieve particular morphologies, crystal structures, chemical compositions, and particle sizes because of the inherent complexity of nanoparticle synthesis. In this work, Au-Sn nanoparticles were synthesized using a continuous one-step gas-phase synthesis method that offers the possibility to anneal the nanoparticles in flight directly after generation to tune their properties. The bimetallic model system Au-Sn, comprising both alloys and intermetallic compounds, was studied in the temperature range of 300 to 1100 °C. The bimetallic Au/Sn ratio in the nanoparticles can be adjusted with in-flight annealing between 70/30 and 40/60 atomic %. While Au-rich alloys are obtained at lower temperatures, the increase in the annealing temperature leads to the formation of more Sn-rich intermetallic phases. Surface and size effects greatly influence particle morphologies and phase fractions. This research opens new opportunities for the synthesis of customized nanoparticles by temperature adjustment and particle size selection.

A flexible way to generate bimetallic nanoparticles with high control of their composition is to use spark ablation of alloyed electrodes. It has been generally accepted and stated that particles produced using spark ablation of alloyed electrodes obtain the same chemical composition as the electrodes. However, we identify a lack of studies fully supporting the connection between electrode and particle composition, presented in a small literature survey. The aim of the study is, hence, to explore the validity of the statement by analysing the relation between alloyed electrodes and their resulting particle composition using three sets of AgAu electrodes containing Au and 25, 50, and 75 atomic % Ag, respectively. The resulting composition is thoroughly investigated using both single particle (scanning- and transmission electron microscopy) and ensemble particle techniques (inductive coupled plasma-mass spectroscopy, x-ray photoelectron spectroscopy, x-ray fluorescence, and optical measurements of surface plasmon resonance. We also investigate how sample size (e.g., the number of particles analysed) affects the reliability of the resulting sample mean. For single-particle measurements of a sample with a compositional standard deviation of a few atomic percentage points, a sample size of 20 particles is a good benchmark for obtaining reliable results of the sample mean. Furthermore, this article aims to challenge the practice in which the composition of nanoparticles is measured, presented, and interpreted, to improve and facilitate future research related to this topic. From the results of this study, it could be concluded that for the investigated Ag–Au material system, the particles obtained a composition very similar to the alloyed AgAu electrodes.