Gestational obesity and subclinical inflammation: The pathway from simple assessment to complex outcome (STROBE-compliant article)

Maternal obesity and excessive gestational weight gain (GWG) are associated with pregnancy-related complications, poor birth outcomes, and increased birth weight (BW).The aims of this study were to assess the relationship between excessive GWG and gestational inflammatory status in terms of blood parameters, as well as its influence on newborn''s outcomes.We performed a prospective study on 176 pregnant women divided into 2 groups depending on the GWG: group 1—normal GWG, 80 cases; and group 2—high GWG, 96 cases. The statistical analysis was performed using the GraphPad Prism program, trial variant. We performed a thorough anamnesis and clinical examination in all mothers and their newborns, as well as an assessment of multiple laboratory parameters.The levels of both platelets and triglycerides were significantly higher in pregnant women from high GWG group (P = .0165/P = .0247). The newborns whose mothers presented an excessive GWG were found with a significantly higher BW as compared to those with normal GWG mothers (P = .0023). We obtained a positive correlation between the mothers’ and newborns’ values for hemoglobin, high-density lipoprotein, leucocytes, and platelets/lymphocytes ratio (P = .0002/P = .0313/P = .0137). Moreover, a significant positive correlation was found between GWG and BW (r = 0.2049, 95% CI: 0.0588–0.3425, P = .0064).Our findings sustain the hypothesis that maternal obesity is a risk factor for macrosomia and childhood obesity since we found a positive correlation between GWG and BW. Women with high GWG expressed significantly higher levels of platelets and triglycerides suggesting a subclinical inflammation associated to excessive fat accumulation. The inflammation transfer from mother to fetus in our study was suggested by the positive correlations between maternal and neonatal leukocytes and platelets/lymphocytes ratio.     

Nanoparticle Tracing during Laser Powder Bed Fusion of Oxide Dispersion Strengthened Steels

The control of nanoparticle agglomeration during the fabrication of oxide dispersion strengthened steels is a key factor in maximizing their mechanical and high temperature reinforcement properties. However, the characterization of the nanoparticle evolution during processing represents a challenge due to the lack of experimental methodologies that allow in situ evaluation during laser powder bed fusion (LPBF) of nanoparticle-additivated steel powders. To address this problem, a simulation scheme is proposed to trace the drift and the interactions of the nanoparticles in the melt pool by joint heat-melt-microstructure–coupled phase-field simulation with nanoparticle kinematics. Van der Waals attraction and electrostatic repulsion with screened-Coulomb potential are explicitly employed to model the interactions with assumptions made based on reported experimental evidence. Numerical simulations have been conducted for LPBF of oxide nanoparticle-additivated PM2000 powder considering various factors, including the nanoparticle composition and size distribution. The obtained results provide a statistical and graphical demonstration of the temporal and spatial variations of the traced nanoparticles, showing ∼55% of the nanoparticles within the generated grains, and a smaller fraction of ∼30% in the pores, ∼13% on the surface, and ∼2% on the grain boundaries. To prove the methodology and compare it with experimental observations, the simulations are performed for LPBF of a 0.005 wt % yttrium oxide nanoparticle-additivated PM2000 powder and the final degree of nanoparticle agglomeration and distribution are analyzed with respect to a series of geometric and material parameters.     

Effect of Receptor Structure and Length on the Wrapping of a Nanoparticle by a Lipid Membrane

Nanoparticles have been considered as a type of powerful tool to deliver drugs and genes into cells for disease diagnosis and therapies. It has been generally accepted that the internalization of nanoparticles into cells is mostly realized by receptor-mediated endocytosis. However, for the influence of structural factors of receptors on endocytosis, this is still largely unknown. In this paper, computer simulations are applied to investigate the effects of structure (i.e., the number of constituent chains of the receptor) and the length of the receptor on the wrapping behavior of nanoparticles by the lipid membrane, which is a key step of receptor-medicated endocytosis. It is found that these structural factors of receptors have strong effects on the nanoparticle’s final interaction configuration with the membrane in the simulations, such as adhering on the membrane surface or being partly or fully wrapped by the membrane. Furthermore, in some cases, the rupture of the lipid membrane occurs. These results are helpful for the understanding of endocytosis and the preparation of advanced nanoscale drug-delivery vectors.     

Organo-Nanocups Assist the Formation of Ultra-Small Palladium Nanoparticle Catalysts for Hydrogen Evolution Reaction

Ultra-small palladium nanoparticles were synthesized and applied as catalysts for a hydrogen evolution reaction. The palladium metal precursor was produced via beta-cyclodextrin as organo-nanocup (ONC) capping agent to produce ultra-small nanoparticles used in this study. The produced ~3 nm nanoparticle catalyst was then characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR) to confirm the successful synthesis of ~3 nm palladium nanoparticles. The nanoparticles’ catalytic ability was explored via the hydrolysis reaction of sodium borohydride. The palladium nanoparticle catalyst performed best at 303 K at a pH of 7 with 925 μmol of sodium borohydride having an H₂ generation rate of 1.431 mL min⁻¹ mL_cat⁻¹. The activation energy of the palladium catalyst was calculated to be 58.9 kJ/mol.     

Forced Convection Nanofluid Heat Transfer as a Function of Distance in Microchannels

As electronic devices become smaller and more powerful, the demand for micro-scale thermal management becomes necessary in achieving a more compact design. One way to do that is enhancing the forced convection heat transfer by adding nanoparticles into the base liquid. In this study, the nanofluid forced convection heat transfer coefficient was measured inside stainless-steel microchannels (ID = 210 μm) and heat transfer coefficient as a function of distance was measured to explore the effects of base liquid, crystal phase, nanoparticle material, and size on heat transfer coefficient. It was found that crystal phase, characteristics of nanoparticles, the thermal conductivity and viscosity of nanofluid can play a significant role on heat transfer coefficient. In addition, the effects of man-made and commercial TiO₂ on heat transfer coefficient were investigated and it was found that man-made anatase TiO₂ nanoparticles were more effective to enhance the heat transfer coefficient, for given conditions. This study also conducted a brief literature review on nanofluid forced convection heat transfer to investigate how nanofluid heat transfer coefficient as a function of distance would be affected by effective parameters such as base liquid, flow regime, concentration, and the characteristics of nanoparticles (material and size).     

Elicitation of Neutralizing Antibody Responses to HIV-1 Immunization with Nanoparticle Vaccine Platforms

A leading strategy for developing a prophylactic HIV-1 vaccine is the elicitation of antibodies that can neutralize a large fraction of circulating HIV-1 variants. However, a major challenge that has limited the effectiveness of current vaccine candidates is the extensive global diversity of the HIV-1 envelope protein (Env), the sole target for HIV-neutralizing antibodies. To address this challenge, various strategies incorporating Env diversity into the vaccine formulation have been proposed. Here, we assessed the potential of two such strategies that utilize a nanoparticle-based vaccine platform to elicit broadly neutralizing antibody responses. The nanoparticle immunogens developed here consisted of different formulations of Envs from strains BG505 (clade A) and CZA97 (clade C), attached to the N-termini of bacterial ferritin. Single—antigen nanoparticle cocktails, as well as mosaic nanoparticles bearing both Env trimers, elicited high antibody titers in mice and guinea pigs. Furthermore, serum from guinea pigs immunized with nanoparticle immunogens achieved autologous, and in some cases heterologous, tier 2 neutralization, although significant differences between mosaic and single—antigen nanoparticles were not observed. These results provide insights into the ability of different vaccine strategies for incorporating Env sequence diversity to elicit neutralizing antibodies, with implications for the development of broadly protective HIV-1 vaccines.     

Influence of three-dimensional nanoparticle branching on the Young’s modulus of nanocomposites: Effect of interface orientation

With the availability of nanoparticles with controlled size and shape, there has been renewed interest in the mechanical properties of polymer/nanoparticle blends. Despite the large number of theoretical studies, the effect of branching for nanofillers tens of nanometers in size on the elastic stiffness of these composite materials has received limited attention. Here, we examine the Young''s modulus of nanocomposites based on a common block copolymer (BCP) blended with linear nanorods and nanoscale tetrapod Quantum Dots (tQDs), in electrospun fibers and thin films. We use a phenomenological lattice spring model (LSM) as a guide in understanding the changes in the Young''s modulus of such composites as a function of filler shape. Reasonable agreement is achieved between the LSM and the experimental results for both nanoparticle shapes—with only a few key physical assumptions in both films and fibers—providing insight into the design of new nanocomposites and assisting in the development of a qualitative mechanistic understanding of their properties. The tQDs impart the greatest improvements, enhancing the Young''s modulus by a factor of 2.5 at 20 wt.%. This is 1.5 times higher than identical composites containing nanorods. An unexpected finding from the simulations is that both the orientation of the nanoscale filler and the orientation of X-type covalent bonds at the nanoparticle-ligand interface are important for optimizing the mechanical properties of the nanocomposites. The tQD provides an orientational optimization of the interfacial and filler bonds arising from its three-dimensional branched shape unseen before in nanocomposites with inorganic nanofillers.Polymer−nanoparticle composites have become a highly active topic of research with rapidly expanding applications (1), in part because of their high polymer−particle interfacial area and the unique shape- and size-dependent, tunable properties of nanoparticle reinforcements. For example, new polymer nanocomposites have been developed that can optically sense stress concentration (2), are responsive to magnetic, electrical, and thermal actuation (3, 4), and exhibit large changes in elastic modulus and glass transition temperature at low nanoparticle concentrations (5).While theoretical studies show that the Young’s modulus of such polymer nanocomposites depends on nanoparticle shape (6), experimental studies are limited. Experimental studies on polymers (7) include the synergistic reinforcement effects of multiple nanocarbons (8) and the shape-dependent reinforcement effects of micrometer-sized tetrapods (9), microscale ceramic needles (10), carbon nanotubes (11), clay-based nanocomposites (12, 13), and others (14). Computational studies include the effects of nanoparticle packing and size on the nanocomposite Young’s modulus (15–17). However, the effects of increasing nanoparticle branching on the mechanical behavior of nanocomposites have not been demonstrated (18). It is possible to make nanocrystals with controlled shapes and degree of branching (19); as such, they pose an ideal system to study the effect of reinforcement branching.Here, using nanorods (NRs) and tetrapod quantum dots (tQDs) in both electrospun fibers and solvent-cast films, we study the effect of increasing nanoparticle branching on the Young’s modulus of a common structural elastomer, poly(styrene block−ethylene−butylene block−styrene) (SEBS) (20). We chose SEBS since it is a widely used structural copolymer, has a 40% phase (ethylene−butylene) of similar chemical makeup as our nanoparticle surface ligands (although it is incompatible with 60% of the polymer, the polystyrene (PS) phase), and is amorphous, allowing for improved intercalation with the nanoparticles. In choosing polymer−filler nanocomposites, there is a critical choice to be made between the case where the polymer−filler interaction is very strong, in which case the intrinsic polymer structure is disrupted to a high degree, and the case where it is weak, leaving the native polymer structure largely unperturbed. Both limits are of significant interest, but in this first study, we focus on the latter weak interface case, as it is by far the most common case in practical composites and it is the case that is most amenable to modeling through summation of mechanically independent components. In such a case, the nanoparticles form nanoscopic aggregates distributed throughout the SEBS matrix, due to the van der Waals interactions between the native alkyl ligands on the nanoparticles and the SEBS polymer. No macrophase separation was observed, and no surface modification was performed to achieve single nanofiller dispersion. Future studies will be directed at the single-filler dispersed case, where the filler−polymer interaction is much stronger. In the stronger interface case, the nanoparticles may be selectively incorporated within one block copolymer (BCP) microdomain, and, due to their size, the intrinsic local polymer chain conformation may be more affected by the presence of the filler.In both electrospun fibers and films, we observed nanoscopic aggregates of nanofillers (∼150 nm in diameter), and we found that the multiple-branched tQDs improved the Young’s modulus the most compared with linear shapes, i.e., nanoscale branching may optimize the Young’s modulus. Our simulated results using a 2D lattice spring model (LSM) suggest that this shape effect on the Young’s modulus is primarily due to the orientation of the strong X-type bonds (21) at the nanoparticle−ligand interface. This illustrates the importance of the orientation of both types (filler and interfacial) of bonds in increasing the stiffness of structural composites. To the best of our knowledge, our study is the first to examine this effect on the mechanical properties of composites for nanofillers in this size range, thereby providing some unique mechanistic insights. We expect that these insights can be exploited to design polymer nanocomposites with optimized mechanical properties for a variety of applications.     

Exploring the Preparation of Albendazole-Loaded Chitosan-Tripolyphosphate Nanoparticles

The objective of this study was to improve the solubility of albendazole and optimize the preparation of an oral nanoparticle formulation, using β-cyclodextrin (βCD) and chitosan-tripolyphosphate (TPP) nanoparticles. The solubility of albendazole in buffers, surfactants, and various concentrations of acetic acid solution was investigated. To determine drug loading, the cytotoxic effects of the albendazole concentration in human hepatocellular carcinoma cells (HepG2) were investigated. The formulations were prepared by mixing the drug solution in Tween 20 with the chitosan solution. TPP solution was added dropwise with sonication to produce a nanoparticle through ionic crosslinking. Then the particle size, polydispersity index, and zeta potential of the nanoparticles were investigated to obtain an optimal composition. The solubility of albendazole was greater in pH 2 buffer, Tween 20, and βCD depending on the concentration of acetic acid. Drug loading was determined as 100 µg/mL based on the results of cell viability. The optimized ratio of Tween 20, chitosan/hydroxypropyl βCD, and TPP was 2:5:1, which resulted in smaller particle size and proper zeta positive values of the zeta potential. The chitosan-TPP nanoparticles increased the drug solubility and had a small particle size with homogeneity in formulating albendazole as a potential anticancer agent.     

Temperature-Responsive Polysaccharide Microparticles Containing Nanoparticles: Release of Multiple Cationic/Anionic Compounds

Most drug carriers used in pulmonary administration are microparticles with diameters over 1 µm. Only a few examples involving nanoparticles have been reported because such small particles are readily exhaled. Consequently, the development of microparticles capable of encapsulating nanoparticles and a wide range of compounds for pulmonary drug-delivery applications is an important objective. In this study, we investigated the development of polysaccharide microparticles containing nanoparticles for the temperature-responsive and two-step release of inclusions. The prepared microparticles containing nanoparticles can release two differently charged compounds in a stepwise manner. The particles have two different drug release pathways: one is the release of nanoparticle inclusions from the nanoparticles and the other is the release of microparticle inclusions during microparticle collapse. The nanoparticles can be efficiently delivered deep into the lungs and a wide range of compounds are released in a charge-independent manner, owing to the suitable roughness of the microparticle surface. These polysaccharide microparticles containing nanoparticles are expected to be used as temperature-responsive drug carriers, not only for pulmonary administration but also for various administration routes, including transpulmonary, intramuscular, and transdermal routes, that can release multiple drugs in a controlled manner.     

Effect of External Charging on Nanoparticle Formation in a Flame

This paper attempts to demonstrate the importance of the nanoparticle charge in the synthesis flame, for the mechanism of their evolution during formation processes. An investigation was made of MgO nanoparticles formed during combustion of magnesium particles. The cubic shape of nanoparticles in an unaffected flame allows for direct interpretation of results on the external flame charging, using a continuous unipolar emission of ions. It was found that the emission of negative ions applied to the flame strongly affects the nanoparticle shape, while the positive ions do not lead to any noticeable change. The demonstrated effect emphasizes the need to take into account all of the phenomena responsible for the particle charge when modeling the nanoparticle formation in flames.     

State of the Art in Gold Nanoparticle Synthesisation via Pulsed Laser Ablation in Liquid and Its Characterisation for Molecular Imaging: A Review

With recent advances in nanotechnology, various nanomaterials have been used as drug carriers in molecular imaging for the treatment of cancer. The unique physiochemical properties and biocompatibility of gold nanoparticles have developed a breakthrough in molecular imaging, which allows exploration of gold nanoparticles in drug delivery for diagnostic purpose. The conventional gold nanoparticles synthetisation methods have limitations with chemical contaminations during the synthesisation process and the use of higher energy. Thus, various innovative approaches in gold nanoparticles synthetisation are under development. Recently, studies have been focused on the development of eco-friendly, non-toxic, cost-effective and simple gold nanoparticle synthesisation. The pulsed laser ablation in liquid (PLAL) technique is a versatile synthetic and convincing technique due to its high efficiency, eco-friendly and facile method to produce gold nanoparticle. Therefore, this study aimed to review the eco-friendly gold nanoparticle synthesisation method via the PLAL method and to characterise the gold nanoparticles properties for molecular imaging. This review paper provides new insight to understand the PLAL technique in producing gold nanoparticles and the PLAL parameters that affect gold nanoparticle properties to meet the desired needs in molecular imaging.     

Hand and Abrasive Flow Polished Tungsten Carbide Die: Optimization of Surface Roughness,Polishing Time and Comparative Analysis in Wire Drawing

This research work highlights the benefits of abrasive flow polishing (AFP) applied to tungsten carbide dies compared with conventional hand polishing (HP). An indigenous experimental set-up for AFP was developed. The effect of prominent process parameters viz. extrusion pressure, number of cycles, and abrasive particle concentration on the final surface roughness, percentage improvement in surface roughness, and polishing time was investigated by Taguchi-designed experiments. The multi-objective optimization (MOO) was performed using the Taguchi-TOPSIS-Equal weight approach to find the respective optimized AFP parametric settings. A set of skilled operators performed the conventional HP of dies, and the best hand-polished (HPed) die was selected using the TOPSIS technique. The operational performance of the HPed dies and the abrasive flow polished (AFPed) dies were compared on the three-stage wire drawing operation. The results revealed that AFP’s surface resulted in a better-quality surface than hand polishing with a 27.06% improvement in surface roughness. Furthermore, AFP can reduce the dependency on costly and tricky-to-locate skilled operators, with a reasonable amount of time saving (about 87.05%). Overall, the study’s findings show that abrasive flow polishing of dies is fast and cost-effective.     

G protein-coupled receptors function as logic gates for nanoparticle binding and cell uptake

More selective interactions of nanoparticles with cells would substantially increase their potential for diagnostic and therapeutic applications. Thus, it would not only be highly desirable that nanoparticles can be addressed to any cell with high target specificity and affinity, but that we could unequivocally define whether they rest immobilized on the cell surface as a diagnostic tag, or if they are internalized to serve as a delivery vehicle for drugs. To date no class of targets is known that would allow direction of nanoparticle interactions with cells alternatively into one of these mutually exclusive events. Using MCF-7 breast cancer cells expressing the human Y₁-receptor, we demonstrate that G protein-coupled receptors provide us with this option. We show that quantum dots carrying a surface-immobilized antagonist remain with nanomolar affinity on the cell surface, and particles carrying an agonist are internalized upon receptor binding. The receptor functions like a logic “and-gate” that grants cell access only to those particles that carry a receptor ligand “and” where the ligand is an agonist. We found that agonist- and antagonist-modified nanoparticles bind to several receptor molecules at a time. This multiligand binding leads to five orders of magnitude increased-receptor affinities, compared with free ligand, in displacement studies. More than 800 G protein-coupled receptors in humans provide us with the paramount advantage that targeting of a plethora of cells is possible, and that switching from cell recognition to cell uptake is simply a matter of nanoparticle surface modification with the appropriate choice of ligand type.     

Defect tolerance and the effect of structural inhomogeneity in plasmonic DNA-nanoparticle superlattices

Bottom-up assemblies of plasmonic nanoparticles exhibit unique optical effects such as tunable reflection, optical cavity modes, and tunable photonic resonances. Here, we compare detailed simulations with experiment to explore the effect of structural inhomogeneity on the optical response in DNA-gold nanoparticle superlattices. In particular, we explore the effect of background environment, nanoparticle polydispersity (>10%), and variation in nanoparticle placement (∼5%). At volume fractions less than 20% Au, the optical response is insensitive to particle size, defects, and inhomogeneity in the superlattice. At elevated volume fractions (20% and 25%), structures incorporating different sized nanoparticles (10-, 20-, and 40-nm diameter) each exhibit distinct far-field extinction and near-field properties. These optical properties are most pronounced in lattices with larger particles, which at fixed volume fraction have greater plasmonic coupling than those with smaller particles. Moreover, the incorporation of experimentally informed inhomogeneity leads to variation in far-field extinction and inconsistent electric-field intensities throughout the lattice, demonstrating that volume fraction is not sufficient to describe the optical properties of such structures. These data have important implications for understanding the role of particle and lattice inhomogeneity in determining the properties of plasmonic nanoparticle lattices with deliberately designed optical properties.The rational arrangement of nanoparticles in multiple dimensions is a promising means for creating materials with novel properties not found in nature. Noble metal nanoparticles are interesting material building blocks due to their ability to amplify local fields by orders of magnitude and scatter light well below the diffraction limit. These efficient interactions with visible light are due to localized surface plasmon resonances (LSPRs), the collective oscillation of conduction electrons (1). Hierarchical arrangements of plasmonic nanoparticles have become the basis for colorimetric sensors (2, 3), subdiffraction limited waveguides (4), visible light metamaterials (5), and nanoscale lasing devices (6, 7), and the ability to adjust architecture in such materials has led to a wide variety of structures with tunable and unusual optical properties (8–12). Many of these technologies leverage the scalability and modularity of bottom-up assembly techniques, which use chemically synthesized colloidal nanoparticles as building blocks (13, 14). Unfortunately, all nanoparticle assembly techniques result in materials with structural defects across multiple length scales, including imprecise particle placement, grain boundaries, and variation in crystallite size. In addition, the nanoparticles used in these systems are inherently inhomogeneous: varying in size, shape, and radius of curvature. Although the effects of inhomogeneity have been investigated at the individual nanoparticle level (15, 16), the effects of inhomogeneity on plasmonic assemblies are not as well understood. Determining the defect resilience of emergent properties is crucial for the continued development of scalable nanomaterial devices with reproducible properties. At this point, a comprehensive understanding of how structural defects contribute to the optical response does not exist.Herein, we combine structural and optical characterization with a variety of theoretical techniques to investigate structural inhomogeneities that affect the optical properties of hierarchical plasmonic assemblies. These factors include the chemical environment of the structure, the inhomogeneity of the nanoparticle building blocks, and the displacement of nanoparticles within the lattice. We use the programmability of DNA (3, 17–22) to construct body-centered cubic (bcc) thin-film plasmonic superlattices comprising nanospheres with diameters of 10, 20, and 40 nm. We compare the optical response of these superlattices with two types of simulations: (i) Fresnel thin-film simulations based solely on volume fraction that closely mimic the experimental geometry, and (ii) rigorous electrodynamics simulations that explicitly describe structural inhomogeneities of the crystalline superlattice. In doing so, we determine that volume fraction accurately describes the plasmonic superlattices comprising plasmonic building blocks spaced at least a diameter apart, i.e., when their interactions are primarily dipolar. At volume fractions of 20% Au and above (when the particles are within a diameter), the plasmonic properties vary depending on the nanoparticle building block size. In the far field, changes in plasmonic coupling primarily result in red-shifted collective resonances. In the near field, however, simulations suggest that both nanoparticle inhomogeneity and disorder in the superlattice arrangement alter the electric-field intensity throughout the lattice. These data suggest that the plasmonic properties of elevated volume fraction superlattices are dependent on both nanoparticle size and crystal symmetry, providing a powerful means for fine-tuning the optical response.     

Differently Shaped Au Nanoparticles: A Case Study on the Enhancement of the Photocatalytic Activity of Commercial TiO2

In the present work, the influence of a gold nanoparticle’s shape was investigated on the commercially available Evonik Aeroxide P25. By the variation of specific synthesis parameters, three differently shaped Au nanoparticles were synthetized and deposited on the surface of the chosen commercial titania. The nanoparticles and their composites’ morphological and structural details were evaluated, applying different techniques such as Diffuse Reflectance Spectroscopy (DRS), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The influence of the Au nanoparticles’ shape was discussed by evaluating their photocatalytic efficiency on phenol and oxalic acid degradation and by investigating the H₂ production efficacy of the selected composites. Major differences in their photocatalytic performance depending on the shape of the deposited noble metal were evidenced.     

Friction mechanism of individual multilayered nanoparticles

Inorganic nanoparticles of layered [two-dimensional (2D)] compounds with hollow polyhedral structure, known as fullerene-like nanoparticles (IF), were found to have excellent lubricating properties. This behavior can be explained by superposition of three main mechanisms: rolling, sliding, and exfoliation-material transfer (third body). In order to elucidate the tribological mechanism of individual nanoparticles in different regimes, in situ axial nanocompression and shearing forces were applied to individual nanoparticles using a high resolution scanning electron microscope. Gold nanoparticles deposited onto the IF nanoparticles surface served as markers, delineating the motion of individual IF nanoparticle. It can be concluded from these experiments that rolling is an important lubrication mechanism for IF-WS(2) in the relatively low range of normal stress (0.96 ± 0.38 GPa). Sliding is shown to be relevant under slightly higher normal stress, where the spacing between the two mating surfaces does not permit free rolling of the nanoparticles. Exfoliation of the IF nanoparticles becomes the dominant mechanism at the high end of normal stress; above 1.2 GPa and (slow) shear; i.e., boundary lubrication conditions. It is argued that the modus operandi of the nanoparticles depends on their degree of crystallinity (defects); sizes; shape, and their mechanical characteristics. This study suggests that the rolling mechanism, which leads to low friction and wear, could be attained by improving the sphericity of the IF nanoparticle, the dispersion (deagglomeration) of the nanoparticles, and the smoothness of the mating surfaces.     

Investigation of Thermal Stability of Microstructure and Mechanical Properties of Bimetallic Fine-Grained Wires from Al–0.25%Zr–(Sc,Hf) Alloys

Thermal stability of composite bimetallic wires from five novel microalloyed aluminum alloys with different contents of alloying elements (Zr, Sc, and Hf) is investigated. The alloy workpieces were obtained by induction-casting in a vacuum, preliminary severe plastic deformation, and annealing providing the formation of a uniform microstructure and the nucleation of stabilizing intermetallide Al₃(Zr,Sc,Hf) nanoparticles. The wires of 0.26 mm in diameter were obtained by simultaneous deformation of the Al alloy with Cu shell. The bimetallic wires demonstrated high strength and improved thermal stability. After annealing at 450–500 °C, a uniform fine-grained microstructure formed in the wire (the mean grain sizes in the annealed Al wires are 3–5 μm). An increased hardness and strength due to nucleation of the Al₃(Sc,Hf) particles was observed. A diffusion of Cu from the shell into the surface layers of the Al wire was observed when heating up to 400–450 °C. The Cu diffusion depth into the annealed Al wire surfaces reached 30–40 μm. The maximum elongation to failure of the wires (20–30%) was achieved after annealing at 350 °C. The maximum values of microhardness (H_v = 500–520 MPa) and of ultimate strength (σ_b = 195–235 MPa) after annealing at 500 °C were observed for the wires made from the Al alloys alloyed with 0.05–0.1% Sc.     

Influence of support morphology on the bonding of molecules to nanoparticles

Supported metal nanoparticles form the basis of heterogeneous catalysts. Above a certain nanoparticle size, it is generally assumed that adsorbates bond in an identical fashion as on a semiinfinite crystal. This assumption has allowed the database on metal single crystals accumulated over the past 40 years to be used to model heterogeneous catalysts. Using a surface science approach to CO adsorption on supported Pd nanoparticles, we show that this assumption may be flawed. Near-edge X-ray absorption fine structure measurements, isolated to one nanoparticle, show that CO bonds upright on the nanoparticle top facets as expected from single-crystal data. However, the CO lateral registry differs from the single crystal. Our calculations indicate that this is caused by the strain on the nanoparticle, induced by carpet growth across the substrate step edges. This strain also weakens the CO–metal bond, which will reduce the energy barrier for catalytic reactions, including CO oxidation.Nanoparticles exhibit properties distinct from their bulk counterparts (1–3). For instance, semiconductor particles smaller than ∼10 nm act as quantum dots (1–4) and oxide-supported gold nanoparticles are active for a variety of reactions including CO oxidation (5), water–gas-shift reaction (6), and epoxidation (7), whereas gold itself is not. Nanoclusters composed of ∼10 atoms have been shown to be exceptionally catalytically active for some reactions on some metals (8, 9). When the particle size is reduced, the relative number of undercoordinated atoms at the edges and corners increases. The proportion of perimeter sites at the interface between the metal and the support also increases. All these sites have been shown to play a crucial role in some reactions (10, 11). Reducing the particle size can also lead to a decrease in the interatomic bond length in small metal clusters (12, 13), which in the case of Pd nanoparticles results in lower adsorption energies for both CO (14, 15) and O₂ (16), although such weakening of CO binding on the nanoparticle can also arise from other factors such as encapsulation of the nanoparticles by the support (17).The role of the support in modifying nanoparticle properties has also been recognized. For instance, the strong metal support interaction has been known for some time (2) and charge transfer either to or from the nanoparticles can lead to enhanced reactivity (18). More recently, it has come to light that the particle size itself may be governed by the interaction with the support (19). However, one effect that has not been discussed and yet should be present in any nanoparticle–support system is the influence of the support morphology such as steps.Here, we investigate the role of the support morphology on the reactivity of metal nanoparticles using scanning tunneling microscopy (STM). As our test system we choose Pd nanoparticles (20, 21) supported on TiO₂(110) (22) simply because much is known about both. The Pd nanoparticles were found to have curved top (111) facets that arise from carpet growth of Pd across the step edges of TiO₂(110) (Fig. 1A). Whereas this carpet growth has been observed for graphene (23) and NaCl films (24), it has not been reported for metal nanoparticles. The effect of the curvature on the reactivity of the Pd nanoparticles was probed via the adsorption of CO molecules, CO on Pd(111) being a particularly well-understood system (25).Open in a separate windowFig. 1.Pd step-island with a curved (111) top facet formed by carpet growth across the TiO₂(110) step edge. (A) STM image (45 × 45 nm²) recorded from a Pd nanoparticle spanning two step edges of the underlying TiO₂ substrate. The nanoparticle has a measured diameter (d) of about 30 nm and a height (h) of 1.9 nm. Red dashed lines roughly mark the locations of the step edges lying beneath the nanoparticle. The nanoparticle and the TiO₂(110) substrate renditions are composed from two versions of the same image. One has background subtraction optimized for the substrate and the other for the Pd nanoparticle. This was necessary to visualize the substrate and the island together with high contrast. The color bar is identical in both components of the image and has a range of 2.23 nm. (Scale bar, 11 nm.) (B) Line profile taken from the black line in A. (C) Schematic showing a cross-section of a Pd nanocrystal spanning two adjacent TiO₂(110) terraces. Pd(111) stacks with an interlayer spacing of 224.5 pm are placed on top of both TiO₂(110) terraces leading to a vertical mismatch of 100.3 pm between Pd(111) layers that originate from different terraces. This vertical mismatch is accommodated by formation of a “carpet” region highlighted in blue.In Rose et al.’s STM study of Pd(111)-CO (25), it was observed that CO first fills threefold fcc-hollow sites, leading to a hollow (H)-(√3×√3)R30°-1CO overlayer at 0.33 monolayers (ML; 1 ML = 1.53 × 10¹⁵ molecules/cm²), where 1CO indicates one CO molecule per primitive unit cell. As the coverage increases to 0.5 ML, CO also starts to fill bridge sites, so that bridge–bridge c(4 × 2)-2CO (BB) as well as hollow–hollow c(4 × 2)-2CO (HH) overlayers form. Above this coverage, CO fills a combination of atop and hollow sites, leading to an atop–hollow (2 × 2)-3CO overlayer at 0.75 ML. With the exception of the BB phase, we have previously observed all these overlayers on Pd nanoparticles supported on TiO₂(110) (26). We also note that hollow site occupation of CO on the (111) top facet of alumina-supported Pd nanoparticles has been evidenced in some vibrational spectroscopy studies (27).On the curved nanoparticle surfaces that we investigate here, we identify two additional CO phases that have not, to our knowledge, previously been observed either on Pd(111) (25) or TiO₂(110)-supported Pd nanoparticles (26). Based on density functional theory (DFT) calculations, we conclude that the previously unobserved overlayers form due to the strain present above the underlying TiO₂(110) steps.     

Spatiotemporal controlled delivery of nanoparticles to injured vasculature

There are a number of challenges associated with designing nanoparticles for medical applications. We define two challenges here: (i) conventional targeting against up-regulated cell surface antigens is limited by heterogeneity in expression, and (ii) previous studies suggest that the optimal size of nanoparticles designed for systemic delivery is approximately 50–150 nm, yet this size range confers a high surface area-to-volume ratio, which results in fast diffusive drug release. Here, we achieve spatial control by biopanning a phage library to discover materials that target abundant vascular antigens exposed in disease. Next, we achieve temporal control by designing 60-nm hybrid nanoparticles with a lipid shell interface surrounding a polymer core, which is loaded with slow-eluting conjugates of paclitaxel for controlled ester hydrolysis and drug release over approximately 12 days. The nanoparticles inhibited human aortic smooth muscle cell proliferation in vitro and showed greater in vivo vascular retention during percutaneous angioplasty over nontargeted controls. This nanoparticle technology may potentially be used toward the treatment of injured vasculature, a clinical problem of primary importance.     

Strain Localization of Orthotropic Elasto–Plastic Cohesive–Frictional Materials: Analytical Results and Numerical Verification

Strain localization analysis for orthotropic-associated plasticity in cohesive–frictional materials is addressed in this work. Specifically, the localization condition is derived from Maxwell’s kinematics, the plastic flow rule and the boundedness of stress rates. The analysis is applicable to strong and regularized discontinuity settings. Expanding on previous works, the quadratic orthotropic Hoffman and Tsai–Wu models are investigated and compared to pressure insensitive and sensitive models such as von Mises, Hill and Drucker–Prager. Analytical localization angles are obtained in uniaxial tension and compression under plane stress and plane strain conditions. These are only dependent on the plastic potential adopted; ensuing, a geometrical interpretation in the stress space is offered. The analytical results are then validated by independent numerical simulations. The B-bar finite element is used to deal with the limiting incompressibility in the purely isochoric plastic flow. For a strip under vertical stretching in plane stress and plane strain as well as Prandtl’s problem of indentation by a flat rigid die in plane strain, numerical results are presented for both isotropic and orthotropic plasticity models with or without tilting angle between the material axes and the applied loading. The influence of frictional behavior is studied. In all the investigated cases, the numerical results provide compelling support to the analytical prognosis.