Nanoparticle Chains Research Articles

Effects of heating rate and sintering temperature on the tensile properties of sintered γ-Ti/Al nanoparticle chains

Abstract This paper presents the results of molecular dynamics simulations that were performed to numerically study the laser sintering process and mechanical behavior of γ-Ti/Al bimetallic alloy nanoparticles (NPs). The study systematically investigates the effects of heating rate and sintering temperature on the resultant uniaxial tensile performances of the sintered NPs. A chain model was formed by connecting three pre-equilibrated Ti/Al NPs via necks during solid-state sintering. The solid-state sintered chain samples were heated to 1798 K using four different heating rates (0.04, 0.2, 0.5, and 1.0 K/ps). After high-temperature relaxation of selected sintering temperature cases (e.g., 398 K, 598 K, etc. with a 200 K interval) for 10 ns, the heat sintered chain samples underwent a solidification process with a cooling rate of 0.08 K/ps and maintained at 298 K for an additional 1 ns. The resulting sintered chain products were then subjected to uniaxial tension at a strain rate of 0.0001/ps. The thermodynamic properties and crystallographic deformation were investigated during the sintering and subsequent tension processes. Analysis of the yield strengths obtained from the tension tests revealed a statistically significant correlation between the tensile strength of the sintered NPs and the pre-established sintering temperatures at each temperature. This observation indicates that higher sintering temperatures strengthen the neck connections within the NP-chains, leading to greater tensile strength. The higher sintering temperatures can reinforce the neck during high-temperature relaxation. It is worth noting that the effect of heating rates on mechanical properties was less pronounced when the sintering temperature was constant.

Electric-field assisted spatioselective deposition of MIL-101(Cr)PEDOT to enhance electrical conductivity and humidity sensing performance

Precise deposition of metal–organic framework (MOF) materials is important for fabricating high-performing MOF-based devices. Electric-field assisted drop-casting of poly(3,4-ethylenedioxythiophene)-functionalized (PEDOT) MIL-101(Cr) nanoparticles onto interdigitated electrodes allowed their precise spatioselective deposition as percolating nanoparticle chains in the interelectrode gaps. The resulting aligned materials were investigated for resistive and capacitive humidity sensing and compared with unaligned samples prepared via regular drop-casting. The spatioselective deposition of MOFs resulted in up to over 500 times improved conductivity and approximately 6 times increased responsivity during resistive humidity sensing. The aligned samples also showed good capacitive humidity sensing performance, with up to 310 times capacitance gain at 10 versus 90 % relative humidity. In contrast, the resistive behavior of the unaligned samples rendered them unsuitable for capacitive sensing. This work demonstrates that applying an alternating potential during drop-casting is a simple yet effective method to control MOF deposition for greater efficiency, conductivity, and enhanced humidity sensing performance.

LSPR anisotropy minimization by sequential growth of Ag nanoparticles on nanoripple patterned Si surface for SERS Application

The present work describes the formation of low-aspect-ratio Ag nanoparticles (NPs) arrays by sequential deposition of Ag from different growth directions on a nanoripple-patterned Si substrate, produced by low-energy ion beam irradiation. It is observed that the growth of Ag-NPs on ripple surfaces is direction-dependent due to the asymmetric ridge of the ripple pattern. This asymmetric ridge can be utilized to tune the shape of NP from elongated to spherical and in turn, assists in minimizing the LSPR anisotropy. The Finite-Difference-Time-Domain (FDTD) simulations demonstrate that the interparticle gap, major, and minor axis combinations of a NP are crucial in minimizing anisotropic near-field interaction. NPs grown perpendicular to the ripple from either direction lead to an elongated chain of nanoparticles; however, if a proper combination of sequential growth times is chosen then the aspect ratio of NPs can be tuned from elongation to spherical ones. Interestingly, a LSPR shift of 209 nm was observed when NPs are grown for 60 min on ripple patterns from one direction only. On the other hand, it reduces to 54 nm when NPs are sequentially grown for 30 min from each of directions, perpendicular to the ripples. SERS measurements also evidence a minimized anisotropic nature in sequentially grown NP arrays; hence, the growth direction as well as optimized growth times together can be used to control the LSPR anisotropy of NP arrays which can be used to fabricate such isotropic SERS substrates.

Magnetic imaging of individual magnetosome chains in magnetotactic bacteria

While significant advances have been made in exploring and uncovering the promising potential of biomagnetic materials, persistent challenges remain on various fronts, notably in the characterization of individual elements. This study makes use of advanced modes of Magnetic Force Microscopy (MFM) and tailored MFM probes to characterize individual magnetotactic bacteria in different environments. The characterization of these elements posed a significant challenge, as the magnetosomes, besides presenting low magnetic signal, are embedded in bacteria of much larger size. To overcome this, customed Atomic Force Microscopy probes are developed through various strategies, enhancing sensitivity in different environments, including liquids. Furthermore, employing MFM imaging under an in-situ magnetic field provides an opportunity to gather quantitative data regarding the critical fields of these individual chains of nanoparticles. This approach marks a substantial advancement in the field of MFM for biological applications, enabling the detection of magnetosomes under different conditions.

In-situ WAXS and SAXS microstructural investigation of Poly(vinylidene fluoride)- Fe3O4 coaxial-electrospun nanocomposites under thermal and mechanical loading: Nanoparticles size effects on fibers molecular orientation, mechanical properties and crystalline polymorphs

In this study, 15 % w/w polyvinylidene fluoride (PVDF)–Fe3O4 nanoparticle (NP) nanocomposite scaffolds were prepared using coaxial electrospinning with a high-speed conductive rotating collector to obtain aligned fibers. The effects of varying the Fe3O4 NP size (6, 9, and 14 nm in diameter) on the fiber morphology, mechanical response, and piezoelectric phase content were investigated. In situ X-ray diffraction measurements during heating-cooling and tensile tests were carried out using synchrotron radiation to study the charge in the β-phase content and polymer chain orientation under different conditions. At zero strain, the presence of smaller NPs seems to impede the β-phase crystallization in PVDF. However, heating-cooling cycles revealed that the NPs acted as nucleation agents, promoting a higher β-phase content after cooling compared to pure PVDF. The mechanical response showed that nanocomposites with smaller NPs exhibited higher stiffness. While the initial degree of polymer chain orientation was higher in the nanocomposites, the presence of NPs hindered the α-to-β phase transformation and chain alignment under tensile deformation compared to pure PVDF. This study highlights the complex interplay among NP size, β-phase formation, mechanical properties, and chain orientation in PVDF-Fe3O4 nanocomposites, providing insights into tailoring their piezoelectric performance for various applications.

Spontaneous self‐assembly of magnetic nanoparticle chains, at the first stage of a gas aggregation source

AbstractThere is an increasing interest in magnetic nanoparticles (MNPs) and self‐assembled MNP chains for applications in biomedicine, catalysis, and other technologically relevant applications. In this work, we report the spontaneous self‐assembly of MNPs at the top surface of the shield of a magnetron sputter head. The resulting nanostructures consisted of clustered nanoscale chains arranged in highly oriented microfibers, with lengths of micrometer order and diameters ranging from 20 to 600 nm. The intense magnetic field gradient around the sputter magnetron's head is the driving force of the self‐assembly process, also trapping species that would otherwise be lost in the carrier gas flow.

Comparison of aggregation effect of axial and polar Magnetotactic bacteria for tumor therapy

Magnetotactic bacteria (MTB), possessing chains of iron oxide nanoparticles, are potential tools for controlled therapy due to their responsiveness to weak magnetic fields. This study aims to evaluate the targeting and aggregation capabilities of axial AMB-1 and polar MO-1 MTB for therapeutic applications. A three-dimensional focusing magnetic field (fMF)-producing device was designed and established with a gradient magnetic field of 0.08 mT/mm at the central region for the guidance of MTB in vitro and in vivo. Under a unidirectional magnetic field, polar Magneto-ovoid MO-1 formed a single line in the culture dish, whereas axial Magnetospirillum magneticum AMB-1 displayed a small portion aggregated on the centerline. With simultaneous X and Y magnetic field application, MO-1 cells aggregated at a point, while AMB-1 bacteria gathered incompletely. Further, magnetic resonance imaging of breast cancer-bearing nude mice injected subcutaneously with MTB peritumorally and navigated by a fMF revealed more substantial aggregation of MO-1 cells within the tumor than AMB-1 bacteria. Prussian blue staining corroborated the penetration of MO-1 cells into the tumor tissue. These findings suggest that polar MO-1 bacteria exhibit superior targeting and aggregation properties compared to axial AMB-1, indicating their potential suitability for targeted therapeutic applications.

The Concept of Using 2D Self-Assembly of Magnetic Nanoparticles for Bioassays

It can be observed that magnetic iron-oxide nanoparticles are increasingly used in bioassay methods. This is due to their stability in aqueous solutions, ease of functionalization, biocompatibility and very low toxicity. Here, we show that the recent discovery of the ability of magnetic nanoparticles to self-assemble into 2D structures of ordered chains may be exploited for bioassays. This would open up the possibility of controlled immobilization of proteins, enzymes, DNA or RNA and other molecular systems on spatially ordered nanostructures. In this work, fluorescein was used as an example. Also shown is the possibility of using Raman spectroscopy to analyze material accumulated on such structures. The observed formation of regularly spaced chains of magnetic nanoparticles takes place during the drying process of a thin layer of magnetic liquid placed on an appropriately prepared low-density polyethylene (LDPE) film.

Assessment of Anti-inflammatory, Antimicrobial and Cytotoxicity of Chitosan-Moringa Composite and Calcium Hydroxide Nanoparticles as an intra-canal medicament in vitro

In this study Chitosan nanoparticles was characterized usingUV spectrophotometry, FT-IR, Transmission electron microscopy, and X-Ray diffraction. The composition of Moringa oleifera of ethanolic extract was analyzed using GC-Mass.The antimicrobial, anti-inflammatory, and cytotoxicity of Chitosan-Moringa composite, H2CaO2 nanoparticles, Ca(OH)2, and Moringa oleifera of ethanol extract as an intra-canal medicament in vitro were also investigated. Results of our research summarized that; The UV of chitosan nanoparticles range from 280 to 300 nm. The FT-IR results confirm the presence of a broad and powerful band at 3442 cm1, 1636 cm1, and 1052 cm1 all band confirm the presence of the native chitosan. The X-Ray diffraction proved three strong characteristic peaks indicating crystallinity of chitosan nanoparticles chains. The TEM of Chitosan nanoparticles size was between 76.61 – 126.91nm and the shape was less spherical with slightly wrinkled surface. The major chemical compounds in Moringa ethanol extract by GC-Mass were detected. Also, the antimicrobial activity of Moringa extracts proved that ethanol extract had the highest zone of inhibition. The antimicrobial activity of Moringa-chitosan composite had the highest antimicrobial activity followed by H2CaO2 nanoparticles against dental pathogens. The anti-inflammatory effects on HRBC hemolysis at concentration 100μg/mL Ca (OH)2 gave the best lower production than the positive control Stander Indo meth followed by H2CaO2 nanoparticles, Moringa ethanol extract, and finally Chitosan-Moringa composite. The MTT assay against OEC have been showed that, Ca (OH)2 is the most cytotoxic with the lowest IC50 followed by Moringa ethanol extract, Chitosan-Moringa composite, and finally H2CaO2 nanoparticles.

Dynamic response of a ferromagnetic nanofilament under rotating fields: effects of flexibility, thermal fluctuations and hydrodynamics.

Using nonequilibrium computer simulations, we study the response of ferromagnetic nanofilaments, consisting of stabilized one dimensional chains of ferromagnetic nanoparticles, under external rotating magnetic fields. In difference with their analogous microscale and stiff counterparts, which have been actively studied in recent years, nonequilibrium properties of rather flexible nanoparticle filaments remain mostly unexplored. By progressively increasing the modeling details, we are able to evidence the qualitative impact of main interactions that can not be neglected at the nanoscale, showing that filament flexibility, thermal fluctuations and hydrodynamic interactions contribute independently to broaden the range of synchronous frequency response in this system. Furthermore, we also show the existence of a limited set of characteristic dynamic filament configurations and discuss in detail the asynchronous response, which at finite temperature becomes probabilistic.

Magnetic nanoparticles for magnetic particle imaging (MPI): design and applications.

Recent advancements in medical imaging have brought forth various techniques such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), and ultrasound, each contributing to improved diagnostic capabilities. Most recently, magnetic particle imaging (MPI) has become a rapidly advancing imaging modality with profound implications for medical diagnostics and therapeutics. By directly detecting the magnetization response of magnetic tracers, MPI surpasses conventional imaging modalities in sensitivity and quantifiability, particularly in stem cell tracking applications. Herein, this comprehensive review explores the fundamental principles, instrumentation, magnetic nanoparticle tracer design, and applications of MPI, offering insights into recent advancements and future directions. Novel tracer designs, such as zinc-doped iron oxide nanoparticles (Zn-IONPs), exhibit enhanced performance, broadening MPI's utility. Spatial encoding strategies, scanning trajectories, and instrumentation innovations are elucidated, illuminating the technical underpinnings of MPI's evolution. Moreover, integrating machine learning and deep learning methods enhances MPI's image processing capabilities, paving the way for more efficient segmentation, quantification, and reconstruction. The potential of superferromagnetic iron oxide nanoparticle chains (SFMIOs) as new MPI tracers further advanced the imaging quality and expanded clinical applications, underscoring the promising future of this emerging imaging modality.

Spatio-temporally resolved dynamical transitions in flow of Pickering emulsions through porous media

Pickering emulsions, when formulated using suitable particles, can exhibit both droplet–droplet and droplet–grain attraction while flowing through porous media. Despite their potential impact on the flow behavior of Pickering emulsions, the underlying mechanisms and dynamics of these attractions are not yet fully understood. To address this, we developed a custom-built micro-sandpack apparatus coupled with confocal microscopy to simultaneously measure the pressure gradient and visualize the flow patterns of emulsions. Our results reveal that the flow of attractive Pickering emulsions displays large-amplitude oscillations in the pressure gradient which cannot be explained using traditional models (e.g. geometric straining, filtration, or continuum). We have identified localized flow patterns characterized by particle attachment and deposition to nearby grains, droplet deposition, jamming of droplets within the throat, and droplet release. These patterns occur cyclically, corresponding to the gradual and rapid changes in the overall pressure gradient. Photonic force microscopy confirmed the strength of droplet–droplet attraction and revealed the underlying cause of this flow dynamics: the formation of chains of nanoparticles that tether droplets together. Our work provides new insights into the mechanism for self-regulated morphological evolution of Pickering emulsion during flow through porous media, resulting from the combined effects of droplet jamming/straining (in line with prior observations of emulsion flow through porous media) and particle deposition (typically observed in the flow of particulate suspensions).

Integrating 2D Materials and Plasmonics on Lithium Niobate Platforms for Pulsed Laser Operation at the Nanoscale

AbstractThe current need for coherent light sources for integrated (nano)photonics motivates the search for novel laser designs emitting at technologically relevant wavelengths with high‐frequency stability and low power consumption. Here, a new monolithic architecture that integrates monolayer MoS2 and chains of silver nanoparticles on a rare‐earth (Nd3+) doped LiNbO3 platform is developed to demonstrate Q‐switched lasing operation at the nanoscale. The localized surface plasmons provided by the nanoparticle chains spatially confine the gain generated by Nd3+ ions at subwavelength scales, and large‐area monolayer MoS2 acts as saturable absorber. As a result, an ultra‐compact coherent pulsed light source delivering stable train pulses with repetition rates of hundreds of kHz and pulse duration of 1 µs is demonstrated without the need of any voltage‐driven optical modulation. Moreover, the monolithic integration of the different elements is achieved without sophisticated processing, and it is compatible with LiNbO3‐based photonics. The results highlight the robustness of the approach, which can be extended to other 2D materials and solid‐state gain media. Potential applications in communications, quantum computing, or ultra‐sensitive sensing can benefit from the synergy of the materials involved in this approach, which provides a wealth of opportunities for light control at reduced scales.

Side-chain engineering of organic photothermal agents for boosting further red-shifted absorption and higher photothermal therapeutic effect

Although organic photothermal agents (PTAs) have been extensively studied in preclinical cancer photothermal therapy (PTT), the internal mechanism, particularly the impact of side chains on photothermal performance, remains inadequately investigated. Herein, we conducted a systematic comparison of the photothermal properties between two organic molecules, namely O-IDTBR with four n-octyl chains and EH-IDTBR with four 2-ethylhexyl chains. With the same conjugated main structure, both O-IDTBR and EH-IDTBR exhibited nearly identical absorption properties (with a peak at 629 nm) in their molecular states. Interestingly, after the formation of nanoparticles (NPs), O-IDTBR NPs with linear alkyl chains exhibit a further red-shifted absorption onset (peak at 711 nm) compared to EH-IDTBR NPs (peak at 662 nm) with branched alkyl chains. Additionally, the photothermal conversion efficiency of O-IDTBR NPs was calculated of 33.7%, which is higher than that of EH-IDTBR NPs (27.7%). This can be attributed to the fact that linear alkyl chains of O-IDTBR NPs promote more intramolecular motions at the aggregated state by extending intermolecular distance and distorting molecular conformation. Therefore, the nonradiative thermal deactivation-induced photothermal property can be further enhanced. Through both in vitro and in vivo experiments, O-IDTBR NPs exhibit effective PTT effect and excellent biocompatibility. This study not only introduces a novel PTA but also opens new avenues for exploring organic optical nano-agents through side-chain engineering to adjust intramolecular motions at the aggregated state.

Coupling Nd3+:Y2O3 fluorescent submicron particles to linear plasmonic chains

We report on the fabrication and optical characterization of a new hybrid material consisting of Nd3+ doped Y2O3 submicron particles associated with linear chains of plasmonic nanostructures. By drop-casting deposition, single Nd3+ doped Y2O3 polycrystalline particles are dispersed and located in the vicinities of plasmonic chains of silver nanoparticles formed on the surface a LiNbO3 substrate. The interaction between the plasmonic modes of the chain with the fluorescent yttria submicron particles is analyzed by micro-luminescence experiments. Orthogonal polarization configurations of the excitation radiation, namely, perpendicular and parallel to plasmonic chain axis, are employed to study the effect of the longitudinal and transverse chain plasmonic modes on the luminescence of the particles. A remarkable dependence of the emission intensity of the Nd3+:Y2O3 submicron particles on the excitation polarization is observed, showing the capability of plasmonic chains to modulate the emission of fluorescent submicron particles in contact with the chain. Numerical simulations evidence a different distribution of the excitation radiation field within the Nd3+:Y2O3 particle depending on the type of excited plasmonic mode, longitudinal or transversal, of the chain, and hence, the ability of plasmonic chains for controlling the emission of Rare Earth doped submicron particles.

Static and Dynamic Magnetization Responses of Self-Assembled Magnetic Nanoparticle Chains

Static and Dynamic Magnetization Responses of Self-Assembled Magnetic Nanoparticle Chains

Gold and Silver Chains from Tetrahydrothiophenocucurbit[6]uril as Au or Ag-Nanoparticles.

Tetrahydrothiophenocucurbit[5 and 6]uril has been synthesized from tetrathiophenoglycoluril diether, providing thioether functionality at the exterior equatorial position of the cucurbituril cage. This functionality has been investigated for chemical modification through sulfoxide formation and subsequent Pummerer rearrangement to the acetoxy derivative of the tetrahydrothiophenocucurbit[5]uril. Nanoparticles of Au and Ag were prepared in the presence of tetrahydrothiophenocucurbit[6]uril, which curiously led to the formation of nanoparticle chains, growing in length over days to weeks.

A Gas Sensor with Enhanced Sensing Properties towards Butyl Acetate: Vascular Bundle Structure Zn2 SnO4 Derived from Maize Straw.

The development of butyl acetate sensors with high sensitivity and selectivity has been highly desirable for its harmful effects on human health. In this work, we developed a high-performance butyl acetate sensor based on vascular bundle structure Zn2 SnO4 nanomaterial derived from maize straw. The vascular bundle structure Zn2 SnO4 with higher specific surface area obtained by calcination to remove the maize straw template, plays the dual role of accelerating the diffusion of gas molecules and providing more active sites. Our research showed that the sensor had a response of 18 to 100 ppm butyl acetate at a working temperature of 250 °C, with a fast response recovery rate (18 s/25 s), which showed significant improvement compared to the Zn2 SnO4 sensor prepared without templates. The improved performance can be attributed to the cross-linked nanoparticle chains and gas collision mechanism of the sensor. These findings highlight the potential of our sensor for the detection of butyl acetate gas.

Optical Binding of Metal Nanoparticles Self‐Reinforced by Plasmonic Surface Lattice Resonances

AbstractOptical binding of metal nanoparticles (NPs) provides a promising way to create tunable photonic materials and devices, where the ultrastrong interparticle interaction is generally attributed to the localized surface plasmon resonances of NPs. Here, it is revealed that the optical binding of metal NPs can be self‐reinforced by the plasmonic surface lattice resonances (PSLRs) associated with the discrete NP arrays. Through simulations and experiments, it is demonstrated that PSLRs can spontaneously arise in optically bound gold NP chains with just a few NPs when they are relatively large, e.g., 150 nm in diameter. Additionally, the PSLRs are enhanced by increasing the chain length, leading to stronger optical binding stiffness. These results reveal a previously unidentified factor that contributes to the ultrastrong optical binding of metal NPs. More importantly, this study presents a prospect for building freestanding and reconfigurable NP arrays that naturally support PLSRs for sensing and other applications.

Adsorption of Aldehyde-Functional Diblock Copolymer Spheres onto Surface-Grafted Polymer Brushes via Dynamic Covalent Chemistry Enables Friction Modification.

Dynamic covalent chemistry has been exploited to prepare numerous examples of adaptable polymeric materials that exhibit unique properties. Herein, the chemical adsorption of aldehyde-functional diblock copolymer spherical nanoparticles onto amine-functionalized surface-grafted polymer brushes via dynamic Schiff base chemistry is demonstrated. Initially, a series of cis-diol-functional sterically-stabilized spheres of 30-250 nm diameter were prepared via reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization. The pendent cis-diol groups within the steric stabilizer chains of these precursor nanoparticles were then oxidized using sodium periodate to produce the corresponding aldehyde-functional spheres. Similarly, hydrophilic cis-diol-functionalized methacrylic brushes grafted from a planar silicon surface using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) were selectively oxidized to generate the corresponding aldehyde-functional brushes. Ellipsometry and X-ray photoelectron spectroscopy were used to confirm brush oxidation, while scanning electron microscopy studies demonstrated that the nanoparticles did not adsorb onto a cis-diol-functional precursor brush. Subsequently, the aldehyde-functional brushes were treated with excess small-molecule diamine, and the resulting imine linkages were converted into secondary amine bonds via reductive amination. The resulting primary amine-functionalized brushes formed multiple dynamic imine bonds with the aldehyde-functional diblock copolymer spheres, leading to a mean surface coverage of approximately 0.33 on the upper brush layer surface, regardless of the nanoparticle size. Friction force microscopy studies of the resulting nanoparticle-decorated brushes enabled calculation of friction coefficients, which were compared to that measured for the bare aldehyde-functional brush. Friction coefficients were reasonably consistent across all surfaces except when particle size was comparable to the size of the probe tip. In this case, differences were ascribed to an increase in contact area between the tip and the brush-nanoparticle layer. This new model system enhances our understanding of nanoparticle adsorption onto hydrophilic brush layers.