Hollow Ones Research Articles

Water Absorption Behavior of Polystyrene Particles Prepared by Emulsion Polymerization with Nonionic Emulsifiers and Innovative Easy Synthesis of Hollow Particles.

Submicrometer-sized raspberry-like polystyrene (PS) particles, which were prepared by emulsion polymerization with polyoxyethylene nonylphenyl ether nonionic emulsifier (Emulgen 910, HLB 12.2) and potassium persulfate initiator, contained 8.5 vol % (relative to the particle) of water and 5.5 wt % (relative to PS) of Emulgen 910 in the inside. The water absorption decreased the glass transition temperature of the PS particles dispersed in an aqueous medium. The wt % (relative to PS) of the incorporated Emulgen 910 increased with increasing initial Emulgen 910 concentration in the emulsion polymerization, but the wt % (relative to the total Emulgen 910 used) of the incorporated Emulgen 910 was constant at approximately 50% independent of the initial concentration. The vol % (relative to particle) of water increased to 46% by heat treatment at 90 °C for 24 h, which was based on further water absorption, and resulted in spherical hollow particles, where the amount of the incorporated Emulgen 910 remarkably decreased in a short treatment and then remained almost constant during the heat treatment. After another 24 h treatment, the percentage of nonhollow particles increased gradually, which was based on the escape of the water domain together with Emulgen 910 from the inside of the particles. On the other hand, spherical PS particles prepared by emulsifier-free emulsion polymerization did not contain water in the inside and were not changed to hollow ones by a similar heat treatment. From these results, an innovative easy method to synthesize hydrophobic hollow PS particles is proposed.

Force Comparison of Commercially Available Transfascial Suture Passers.

Transfascial suture passers (TSPs) are a commonly used surgical tool available in a wide array of tip configurations. We assessed the insertion force of various TSPs in an ex vivo porcine model. Uniform sections of porcine abdominal wall were secured to a 3D-printed platform. Nine TSPs were passed through the abdominal wall both without and with prolene suture under the following scenarios: abdominal wall only and abdominal wall plus underlay ePTFE or composite ePTFE/polypropylene mesh. Insertion forces were recorded in Newton (N). When passed without suture through the abdominal wall, smaller diameter TSPs required less insertional force (1.50 ± 0.17 N vs 9.68 ± 1.50 N [ P = 0.00072]). Through composite mesh, the solid tipped TSPs required less force than hollow tipped ones (3.87 ± 0.25 N vs 7.88 ± 0.20 N [ P = 0.00026]). Overall, smaller diameter TSPs required less force than the larger TSPs when passed through ePTFE empty (Gore 2.95 ± 0.83 N vs Carter-Thomason 16.07 ± 2.10 N [ P = .0005]) or with suture (Gore 8.37 ± 2.59 N vs Carter-Thomason 19.12 ± 1.10 N [ P = .003]). Diameter plays the greatest role in the force required for TSP penetration. However, when passed through underlay mesh or while holding suture, distal tip shape, the mechanism of suture holding, and shaft diameter all contribute to the forces necessary for penetration. These factors should be considered when choosing a TSP for intraoperative use.

Size Dependent Properties of Hollow Gold Nanoparticles: A Theoretical Investigation

A new kind of nanostructures with the negative curvature defined as the hollow ones have recently used in biomedical applications. In this work, an analytic model was developed to compute the size-dependent properties of spherical hollow gold nanoparticles in shell-core-shell configuration. This model has established to calculate the cohesive energies based on the surface energy consideration depending on sizes of inner and outer surfaces of hollow nanoparticles. The size and geometry of the model particles have been obtained by using the stability diagram and the collapsing mechanism was studied by molecular dynamics simulations. The model has been also applied to the hollow particles within unstable and half stable geometry. The predicted results have been compared with each other and those obtained by solid ones. The theoretically predicted size dependent properties are consistent with experimental observations and the hollow quantum dot calculations. Thus, an atomistic insight into the size effect on the cohesive energies of hollow nanoparticles has been presented.

Fabrication of hollow gold nanoparticles by dewetting, dealloying and coarsening

A sequence of diffusion-controlled processes, namely, thin film dewetting, dealloying and thermal coarsening was employed for producing of hollow gold nanoparticles. The porous gold nanoparticles on silica substrate were obtained by solid state dewetting of Au–Ag bi-layers followed by selective dealloying of Ag. We studied in detail the last stage of the proposed method enabling the transformation of porous nanoparticles into hollow ones due to curvature-driven surface diffusion. The porous nanoparticles were annealed at 350 °C in air and in vacuum and characterized by high-resolution scanning electron microscopy. The microstructure evolution of the particles during thermal treatment was studied by in-situ X-ray diffraction. The observed decrease of compressive strain in the particles during coarsening was discussed in terms of Weissmüller–Cahn model. Annealing in ambient air resulted in faster coarsening of gold nanoparticles compared to annealing in vacuum. The isolated pores trapped in the particle bulk as well as the pores located at the particle/substrate interface were observed in the particles annealed in air. A qualitative model illustrating the observed coarsening behavior is proposed.

High-<inline-formula> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> Inductors Utilizing Thick Metals and Dense-Tapered Spirals

Ultra-thick metals are known to be counter productive for quality factor (Q) improvement at high frequencies in multiturn inductors. From the experimental results, assisted by electromagnetic simulations, it is first shown that Q improvement with ultra-thick metals can be pushed to higher frequencies using variable width and spaced (tapered) spirals. Furthermore, it is also shown that the extent of tapering is proportional to the metal thickness for the highest performance. Second, dense-tapered layouts are shown to be good candidates for higher Q rather than hollow ones for a given inductance density.

Cochleate characterization by cryogenic electron microscopy methods: Cryo-TEM and Cryo-SEM

Cochleates are lipid microstructures consisting of negatively charged phospholipid bilayers rolled up into cigar-like spirals, which are formed through the interactions with multivalent counter-ions used as bridging agents. This lipid system was shown to have potential as a drug carrier, primarily for oral delivery. In this study, we describe the structure of cochleates made of dioleoylphosphatidylserine (DOPS), a negatively charged lipid, and calcium that induce the bridging of lipid layers and complex formation. By using advanced cryogenic electron microscopy (CryoEM) methods, cryo-TEM and cryo-SEM, we are able to explore local and global structural details of the cochleates at length scales ranging from the nano to the micro-scale, at high resolution, and at conditions relating to the hydrated, native state. We reveal the nano-layers of cochleates and provide evidence to the mechanism of their formation, and show that that full cochleates and hollow ones can be created, as well as cone-shaped structures. Also, cochleates may be formed by the spiraling of more than one bilayer lamella. The structural insights from this study shed light on the complexation process, which ultimately can impact the delivery of drugs by such carriers.

Cortes cárneos e constituintes não-carcaça de ovelhas terminadas em pasto com teores diferentes de suplementação

This study aimed to evaluate the yield of meat cuts and other body components of sheep kept on pasture Panicum maximum, Massai cultivar, fed increasing amounts of concentrate. The animals were divided into four treatments according to the concentrate intake in relation to body weight (zero, 0.7, 1.4 and 2.1%). After slaughter of the sheep, the weights of non-hollow viscera (tongue, lung, liver, diaphragm, kidney and spleen), hollow ones (trachea, esophagus, heart, gallbladder, bladder, rumen, omasum, abomasum, small and larger intestines), other components (blood, skin, feet, head, tail and mammary gland) and fat in the viscera (omental, mesenteric, perirenal and cavity). In carcasses, the commercial cuts were made (shoulder, ribs, loin, leg, and neck). The cuts except the neck, did not alter their weights, however, there were changes in their proportions. Only the percentage of loin did not change. With the intake of 1.42% in concentrate for body weight, there was an increase of ribs over the leg. The total weight of the non-carcass did not change, however, there was variations in its proportion. Amongst the most noticeable changes is the amount of visceral fat, which greatly increased when the sheep ingested 1.35% in concentrate for body weight. Therefore, concentrate intake by culling ewes does not increase mass commercial cuts. The proportions of commercial cuts and other body constituents change diffusely. With the maturity has been reached, the observed weight gain is, in most cases, result of increased visceral fat.

Controllable synthesis of novel ZnSn(OH)6 hollow polyhedral structures with superior ethanol gas-sensing performance

The synthesis of micro-/nanostructures with desired structure and morphology is of great technological and scientific value owing to their superior physical and chemical properties. In this paper, high uniformity ZnSn(OH)6 (ZHS) with novel hollow polyhedral structures were prepared by a facile self-templating method. The structures and morphologies of ZHS samples were investigated by several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). On the basis of those characterizations, it was found that the solid polyhedras of ZHS were formed firstly by the co-precipitation and then the solid polyhedras converted into hollow ones by an inward etching process with the help of OH−. The diameter of the ZHS hollow polyhedra was around 0.8–1μm and the thickness was about 150–200nm. Owing to the well-shaped polyhedral and hollow structure, the sensor based on ZHS hollow polyhedras exhibited high response and good selectivity to ethanol gas, indicating that the ZHS hollow polyhedras are highly promising for applications as ethanol sensors.

Hollow and hollow core/shell CeO2/SiO2@CeO2 spheres: Synthesis, structure evolution and catalytic properties

The synthesis of hollow and hollow core/shell CeO2/SiO2@CeO2 spheres by using carbon spheres as a sacrificial template through a two step method is demonstrated in the present study. The preparation involves the key strategies of loading of precursor nucleates into templates and the further loading of silica layer upon them driven by solvothermal. The creation of hollow core/shell structure is achieved after the removal of templates owing to the oxide shell forming is not match with the combustion of templates. Additionally, the products have also experienced a structure evolution from hollow core/shell to hollow with the increasing of starting annealing temperature, which may reveal the transition of precursor driven by heating. The results show that the resultant hollow core/shell CeO2/SiO2@CeO2 spheres exhibit enhanced catalytic activities compared to the hollow ones because of their excellent textural properties.

The stability and diffusion properties of foreign impurity atoms on the surface and in the bulk of vanadium: A first-principles study

Vanadium-based alloy is an attractive candidate for the first-wall or blanket structural materials in future fusion reactors. Foreign impurity atoms (FIAs), such as C, O and N, will seriously affect the mechanical and chemical properties of vanadium-based alloy. With first-principles DFT calculations and CI-NEB method, the stability and diffusion properties of FIAs on the surface and subsurface and in the bulk of metallic vanadium have been studied in details. It is found that the most preferred sites are the hollow ones for the FIAs on V(100) surface. C and N atoms prefer the TIS2–OIS2 site but O atom favors the TIS1-bridge site in the subsurface. O atom is easier to diffuse on the (100) surface. C atom has the highest barrier from the surface to the subsurface, but can diffuse easily from TIS1 to TIS2 in the subsurface. C, O and N atoms all prefer the OIS in the bulk. The diffusion barrier of N atom in vanadium bulk is the highest, while the diffusion coefficient of C atom is the largest. Electronic properties of FIAs on the surface and in the bulk have also been discussed and it is found that the FIAs at the preferred sites gain more electrons than those at the other sites.

Hollow Nanostructures: Highly Ordered Hollow Oxide Nanostructures: The Kirkendall Effect at the Nanoscale (Small 17/2013)

Highly-ordered ultralong copper oxide nanotubes are fabricated by a simple two-step strategy involving the growth of copper nanowires on nanopatterned template substrates by magnetron sputtering followed by thermal annealing in air. As reported by A. A. El Mel and co-workers on page 2838, upon annealing, the nanoscale Kirkendall leads to the transformation of the solid nanostructures into hollow ones. This route is not only limited to 1D nanostructures, but can also be applied to different shapes including 0D nanodots.

Enhancing Colloidal Metallic Nanocatalysis: Sharp Edges and Corners for Solid Nanoparticles and Cage Effect for Hollow Ones

There are two main classes of metallic nanoparticles: solid and hollow. Each type can be synthesized in different shapes and structures. Practical use of these nanoparticles depends on the properties they acquire on the nanoscale. Plasmonic nanoparticles of silver and gold are the most studied, with applications in the fields of sensing, medicine, photonics, and catalysis. In this Account, we review our group's work to understand the catalytic properties of metallic nanoparticles of different shapes. Our group was the first to synthesize colloidal metallic nanoparticles of different shapes and compare their catalytic activity in solution. We found that the most active among these were metallic nanoparticles having sharp edges, sharp corners, or rough surfaces. Thus, tetrahedral platinum nanoparticles are more active than spheres. We proposed this happens because sharper, rougher particles have more valency-unsatisfied surface atoms (i.e., atoms that do not have the complete number of bonds that they can chemically accommodate) to act as active sites than smoother nanoparticles. We have not yet resolved whether these catalytically active atoms act as catalytic centers on the surface of the nanoparticle (i.e., heterogeneous catalysis) or are dissolved by the solvent and perform the catalysis in solution (i.e., homogenous catalysis). The answer is probably that it depends on the system studied. In the past few years, the galvanic replacement technique has allowed synthesis of hollow metallic nanoparticles, often called nanocages, including some with nested shells. Nanocage catalysts show strong catalytic activity. We describe several catalytic experiments that suggest the reactions occurred within the cage of the hollow nanocatalysts: (1) We synthesized two types of hollow nanocages with double shells, one with platinum around palladium and the other with palladium around platinum, and two single-shelled nanocages, one made of pure platinum and the other made of pure palladium. The kinetic parameters of each double-shelled catalyst were comparable to those of the single-shelled nanocage of the same metal as the inside shell, which suggests the reactions are taking place inside the cavity. (2) In the second set of experiments, we used double-shelled, hollow nanoparticles with a plasmonic outer gold surface and a non-plasmonic inner catalytic layer of platinum as catalysts. As the reaction proceeded and the dielectric function of the interior gold cavity changed, the plasmonic band of the interior gold shell shifted. This strongly suggested that the reaction had taken place in the nanocage. (3) Finally, we placed a catalyst on the inside walls of hollow nanocages and monitored the corresponding reaction over time. The reaction rate depended on the size and number of holes in the walls of the nanoparticles, strongly suggesting the confinement effect of a nanoreactor.

Soft hollow particle damping identification in honeycomb structures

The aim of this study is to provide a structural damping solution for space applications to enhance mission performance of honeycomb structures. Classical particle dampers are enclosures partially filled with small metallic or glass spheres, attached to a vibrating structure. The induced damping mechanism is mainly due to frictional losses and collision effects. This paper deals with replacing classical hard particles with soft hollow ones. This study is oriented toward experimental investigations and theoretical validation in order to distinguish dissipation phenomena. The experimental approach first relies on identifying the damping in small honeycomb samples filled with particles. Instead of dissipation by friction and impact, the elliptical shape of the measured hysteresis loops highlights that visco-elastic behavior is dominant with these specific soft particle dampers. Then, experimental and numerical validations are performed on aluminum honeycomb cantilever beams filled with particles. To take into account the effect of the particles, equivalent oscillators, based on the previous experimental damping identification, are added to a finite element model. These kinds of particle dampers are highly nonlinear as a function of excitation frequency and amplitude. It is shown that good damping efficiency is achieved across a large frequency range with low impact on structure stiffness. This paper suggests a convenient method to model the structural damping induced by soft hollow particles.

Large vesicles of ethylenediaminediacetic in ethanol due to hydrogen bonding

Bola surfactant ethylenediaminediacetic (EDDA) was successfully synthesized with using a novel approach. For composites obtained through the supramolecular organization in the ethanol solution, transition behavior of vesicle morphology such as worm-like, petal-like, clustered worm-like, saccules and spherical, was captured by transmission electron microscopy (TEM). In vesicles mentioned above well-defined large spherical aggregations, some of which were solid vesicles, some hollow ones and some multilamellar ones about 1.0–1.5μm, were evidenced by fluorescence microscope. Furthermore, the morphologies and properties of the vesicles were elucidated by means of Fourier transform infrared spectroscopy (FTIR), laser particle size analyzer, geometry simulation of supramolecular architectures and fluorescence spectrophotometer. On the basis of these analyses, the main driving force of large vesicles was considered to be the strong hydrogen bonding interaction among the exposed hydrophilic part of the EDDA surfactant. During the whole process, the ethanol solution played a very important synergistic role in forming self-assembly aggregate in this system.

Controlled synthesis of magnetic Pd/Fe3O4 spheres via an ethylenediamine-assisted route

A simple route based on time-dependent growth was employed to synthesize solid and hollow spheres of Pd/Fe(3)O(4) nanocomposite. Transmission electron microscopic (TEM) imaging shows that the spheres are composed of nanocrystals with the solid spheres having a diameter of 533 nm whereas the hollow ones having a diameter of 520 nm and a shell thickness of 100 nm. An assembly-then-growth mechanism for the formation of the magnetic Pd/Fe(3)O(4) nanocomposite has also been elucidated on the basis of the experimental observations. It is demonstrated that the Pd/Fe(3)O(4) nanocomposite functions as a heterogeneous catalyst for the hydrogenation reaction of p-nitrophenol at room temperature under atmospheric pressure. Both the solid and hollow spheres possess unique magnetic properties so that they may be conveniently separated and recovered by a magnet after the catalytic reaction.

Hollow core–shell nanostructure supercapacitor electrodes: gap matters

Hollow core–shell nanorods with a nanogap are designed and constructed with the assistance of atomic layer deposition (ALD) for energy storage applications. As a demonstration, CoO nanorods and NiO nanowalls are enclosed by a TiO2 nanotube shell, forming the “wire in tube” and “wall in box” structures, respectively. A thin sacrificial layer of Al2O3 is deposited by ALD and removed eventually, forming a nanogap between the CoO core (or the NiO nanowall) and the TiO2 shell. When they are tested as supercapacitor electrodes, an evident difference between the solid core–shell nanostructure and hollow ones can be found; for example, the hollow structure shows ∼2 to 4 times the capacitance compared to the solid wires. The electrochemical properties are also superior compared to the bare nanorods without the nanotube shell. The enhancement is ascribed to the conformal hollow design which provides enlarged specific surface areas and a shorter ion transport path. It is prospected that such a positive nanogap effect may also exist in other electrochemical cell electrodes such as lithium ion batteries and fuel cells.

Effects of sodium dodecyl benzenesulfonic acid (SDBS) on the morphology and the crystal phase of CaCO3

The effects of anionic surfactant on the morphology and crystallization of calcium carbonate precipitated from CaCl2 and Na2CO3 were investigated. Although reaction temperature did not have an effect on the morphology of calcium carbonate, it did have an effect on the cluster size. The cluster size became bigger with high reaction temperature. With the addition of sodium dodecyl benzenesulfonic acid (SDBS), the morphology of precipitated calcium carbonate changed from cubic to porous spheres with over 98% of the crystal phase transformed from calcite to vaterite. The analysis of precipitates formed by the reaction of CaCl2 solution (from limestone (CaO 50% content)) and Na2CO3 found that the morphology of precipitated calcium carbonate changed from cubic to spherical, and the crystal phase changed from calcite to over 94% vaterite with the addition of sodium dodecyl benzenesulfonic acid. These vaterite structures were solid spheres rather than hollow ones.

In vitro degradation rate of apatitic calcium phosphate cement with incorporated PLGA microspheres

Calcium phosphate cements (CPCs) are frequently used as bone substitute material. Despite their superior clinical handling and excellent biocompatibility, they exhibit poor degradability, which limits bone ingrowth into the implant. Microspheres were prepared from poly( d, l-lactic-co-glycolic acid) (PLGA) and included in injectable CPCs as porogens in order to enhance its macroporosity after the polymeric microspheres had degraded. Upon degradation of the PLGA microspheres, acid is produced that enhances the dissolution rate of the CPC. However, the effect of the characteristics of PLGA microspheres on the degradation rate of CPCs has never been studied before. Therefore, the purpose of the current study was to investigate the dependence of CPC degradation on the chemical and morphological characteristics of incorporated PLGA microspheres. With respect to the chemical characteristics of the PLGA microspheres, the effects of both PLGA molecular weight (5, 17 and 44 kDa) and end-group functionalization (acid-terminated or end-capped) were studied. In addition, two types of PLGA microspheres, differing in morphology (hollow vs. dense), were tested. The results revealed that, although both chemical parameters clearly affected the polymer degradation rate when embedded as hollow microspheres in CPC, the PLGA and CPC degradation rates were mainly dependent on the end-group functionalization. Moreover, it was concluded that dense microspheres were more efficient porogens than hollow ones by increasing the CPC macroporosity during in vitro incubation. By combining all test parameters, it was concluded that dense PLGA microspheres consisting of acid-terminated PLGA of 17 kDa exhibited the highest and fastest acid-producing capacity and correspondingly the highest and fastest amount of porosity. In conclusion, the data presented here indicate that the combination of dense, acid-terminated PLGA microspheres with CPC emerges as a successful combination to achieve enhanced apatitic CPC degradation.

Single-crystalline ZnSn(OH)6 hollow cubes via self-templated synthesis at room temperature and their photocatalytic properties

The synthesis of single-crystalline hollow particles with well-defined non-spherical shapes, especially hollow complex compounds, remains a significant challenge. In this paper, single-crystalline ZnSn(OH)6 (ZHS) hollow cubes were first synthesized by a facile self-templating method at room temperature. On the basis of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy, it was found that hollow ZHS cubes were formed by a two-step process, in which solid cubes of ZHS were formed in the first step due to the co-precipitation of Zn(II) and Sn(IV) under basic conditions and then the solid cubes as the self-templates were converted to hollow ones through an alkali-assisted dissolution process. During the process, NaOH solution added in the second step is critical to the formation of ZHS hollow structures. The photocatalytic activity of ZHS hollow cubes for phenol degradation was tested, which showed much higher catalytic activity than that of the solid ZHS cubes. After four trials, the photocatalytic activity of the ZHS hollow cubes exhibits no significant loss.

Influence of Ti on the formation and stability of gas-phase Mg nanoparticles

The effect of titanium on magnesium nanoparticle formation is investigated in relation to the importance of Mg in hydrogen storage. Addition of Ti reduces the Mg-nanoparticle sizes in the range of 5–20 nm and leads to less protective Mg-oxide shells. This in return accelerates the evaporation of Mg that leads to hollow Mg cores. The presence of oxygen plays a dual role in forming MgO protected stable Mg nanoparticles above a critical size (∼15 nm) and hollow ones below this size both due to evaporation and oxidation associated Kirkendall effects.