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51.
Polystyrene latex (PSL) nanoparticle (NP) sample is one of the most widely used standard materials. It is used for calibration of particle counters and particle size measurement tools. It has been reported that the measured NP sizes by various methods, such as Differential Mobility Analysis, dynamic light scattering (DLS), optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), differ from each other. Deformation of PSL NPs on mica substrate has been reported in AFM measurements: the lateral width of PSL NPs is smaller than their vertical height. To provide a reliable calibration standard, the deformation must be measured by a method that can reliably visualize the entire three dimensional (3D) shape of the PSL NPs. Here we present a method for detailed measurement of PSL NP 3D shape by means of electron tomography in a transmission electron microscope. The observed shape of the PSL NPs with 100 nm and 50 nm diameter were not spherical, but squished in direction perpendicular to the support substrate by about 7.4% and 12.1%, respectively. The high difference in surface energy of the PSL NPs and that of substrate together with their low Young modulus appear to explain the squishing of the NPs without presence of water film. 相似文献
52.
A Non‐Enzymatic Hydrogen Peroxide Sensor Based on Gold Nanoparticles/Carbon Nanotube/Self‐Doped Polyaniline Hollow Spheres 下载免费PDF全文
In this study, a novel non‐enzymatic hydrogen peroxide (H2O2) sensor was fabricated based on gold nanoparticles/carbon nanotube/self‐doped polyaniline (AuNPs/CNTs/SPAN) hollow spheres modified glassy carbon electrode (GCE). SPAN was in‐site polymerized on the surface of SiO2 template, then AuNPs and CNTs were decorated by electrostatic absorption via poly(diallyldimethylammonium chloride). After the SiO2 cores were removed, hollow AuNPs/CNTs/SPAN spheres were obtained and characterized by transmission electron microscopy (TEM), field‐emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical catalytic performance of the hollow AuNPs/CNTs/SPAN/GCE for H2O2 detection was evaluated by cyclic voltammetry (CV) and chronoamperometry. Using chronoamperometric method at a constant potential of ?0.1 V (vs. SCE), the H2O2 sensor displays two linear ranges: one from 5 µM to 0.225 mM with a sensitivity of 499.82 µA mM?1 cm?2; another from 0.225 mM to 8.825 mM with a sensitivity of 152.29 µA mM?1 cm?2. The detection limit was estimated as 0.4 µM (signal‐to‐noise ratio of 3). The hollow AuNPs/CNTs/SPAN/GCE also demonstrated excellent stability and selectivity against interferences from other electroactive species. The sensor was further applied to determine H2O2 in disinfectant real samples. 相似文献
53.
We first review the Coset Space Dimensional Reduction (CSDR) programme and present the best model constructed so far based on the , 10‐dimensional E8 gauge theory reduced over the nearly‐Kähler manifold with the additional use of the Wilson flux mechanism. Then we present the corresponding programme in the case that the extra dimensions are considered to be fuzzy coset spaces and the best model that has been constructed in this framework too. In both cases the best model appears to be the trinification GUT . 相似文献
54.
《Particuology》2022
An innovative application of the solvent evaporation technique was suggested. Solvent evaporation technique is a technique for drug encapsulation and nanosphere preparation. The widely used technique is also facing the problem of low actual drug entrapment percent, which is not economic from the industrial view. The goal of this work is trying to use the advantage of this technique concerning the product sphericity and the ability to control particle size, to prepare a drug as pure crystals spheres. Ibuprofen is selected as a model drug. The spheres are formed by using Polyvinyl pyrrolidone (PVP) or Polyethylene glycol (PEG) as an anti-aggregating agent but not formed on using tween or span. Particle size and actual drug content depend on the concentrations the anti-aggregating agent used. Surfaces of the drug crystal spheres are porous with empty sphere internal structure on using PVP but spongy and rough on using PEG. The drug has its identity chemical form in the drug crystal spheres. IR scan of spheres prepared on using PEG showed a characteristic ether peak. DSC showed melting endothermic peak of PEG, but X-ray showed minor change in the drug crystal patterns. Drug release profiles from crystal spheres prepared with the same anti-aggregating agent are close to each other. The drug release profiles from drug crystal spheres prepared by using PEG are more controlled than that prepared by using PVP. The drug release mechanism is diffusion. It was concluded that, the same technique could be suggested for preparation of other biomedical material in pure crystals spheres with controlled particle size. These properties may encourage to prepare very small particles with spherical shape for inhalation or injection as an innovative particle technology application for the widely used technique. 相似文献
55.
The Effect of the Modification of Carbon Spheres with ZnCl2 on the Adsorption Properties towards CO2
Iwona Peech Piotr Staciwa Daniel Sibera Ewelina Kusiak-Nejman Antoni W. Morawski Joanna Kapica-Kozar Urszula Narkiewicz 《Molecules (Basel, Switzerland)》2022,27(4)
Zinc chloride and potassium oxalate are often applied as activating agents for carbon materials. In this work, we present the preparation of ZnO/carbon spheres composites using resorcinol-formaldehyde resin as a carbon source in a solvothermal reactor heated with microwaves. Zinc chloride as a zinc oxide source and potassium oxalate as an activating agent were applied. The effect of their addition and preparation conditions on the adsorption properties towards carbon dioxide at 0 °C and 25 °C were investigated. Additionally, for all tested sorbents, the CO2 sorption tests at 40 °C, carried out utilizing a thermobalance, confirmed the trend of sorption capacity measured at 0 and 25 °C. Furthermore, the sample activated using potassium oxalate and modified using zinc chloride (a carbon-to-zinc ratio equal to 10:1) displayed not only a high CO2 adsorption capacity (2.69 mmol CO2/g at 40 °C) but also exhibited a stable performance during the consecutive multicycle adsorption–desorption process. 相似文献
56.
Micrometer-sized MoO2 hollow spheres were synthesized hydrothermally with ammonium heptamolybdate tetrahydrate as molybdenum source, Cetyltrimethylammonium bromide as structure-directing agent and C2H5OH as reducing agent, respectively. The products were investigated by X-ray diffraction, thermo- gravimetry and differential thermal analysis, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A morphology transition of "blocks-solid spheres-hollow spheres" during the growth process was observed and the possible mechanism for the formation of MoO2 samples was proposed to be through a microscale Kirkendall effect. 相似文献
57.
The working performance of agricultural machinery is largely determined by the walking performance of the wheel when driving in complex unstructured soil. However, the driving performance of existing wheels is not satisfactory for paddy field with muddy soil. The purpose of the current study is therefore to propose a novel rigid wheel for agricultural machinery which is applicable to paddy field with muddy soil. Firstly, a novel arc edge shaped wheel was designed based on the principles of mechanics on the ground. Then the driving performance of this arc edge shaped wheel was evaluated using FE modeling of interaction between rigid wheel and soil. Finally, the structure originally designed arc edge shaped wheel was improved according to FE modeling results, and this improved design was further evaluated by both FE simulation and prototype experiments. Both FE modeling and experimental results indicate that the improved arc edge shaped wheel proposed in this study has a good driving performance with regarding to wheel sinkage and soil reaction force. The proposed arc edge shaped wheel could be used as an effective component of rice harvester for paddy field with muddy soil. 相似文献
58.
《Physics letters. A》2020,384(22):126539
Ultrathin MnO2 nanosheets grown on the surface of hollow carbon spheres (MnO2/HCSs) were fabricated by the redox reaction between carbon spheres with KMnO4 in aqueous solution. Due to the porous structure and large amounts of active sites, MnO2/HCSs exhibit excellent capacitive performance with 227.5 F g−1 at 1 A g−1. After 5000 cycles, the capacity retention of MnO2/HCSs remains 96%, indicating its good cycling stability. These results demonstrate that MnO2/HCSs are promising supercapacitor electrode material and this work provide a facile method for growth of ultrathin MnO2 nanosheets on carbon substrate. 相似文献
59.
60.
Hong-Ping Lin Yah-Ru Cheng Chung-Rong Lin Feng-Yin Li Chang-Lin Chen She-Tin Wong Soofin Cheng Shang-Bin Liu Ben-Zu Wan Chung-Yuan Mou Chin-Yuan Tang Ching-Yen Lin 《中国化学会会志》1999,46(3):495-507
We report a “delayed neutralization” process for the preparation of highly-ordered aluminosilicate MCM-41 molecular sieves with high thermal and hydrothermal stability, and sharp pore size distribution. However, the structural order and pore size are dependent on the carbon chain length. In the mixture surfactant systems, the pore size of the MCM-41 materials could be fine-tuned. The pore size can be extended from 2.5 to 4.5 nm by adding a suitable amount of hydrocarbons. The tubular morphology of the MCM-41 material of 0.3 to 10 micrometers diameter, where the wall consists of coaxial cylindrical pores of nanometers MCM-41, can be obtained by careful control of the surfactant-water content and the rate of condensation of silica. An optimum condition for automatic synthesis of the hierarchical TWT structure has been accomplished. The addition of 1-alkanols as cosurfactant would not only improve the order of the MCM-41 hexagonal structure but also promote the formation of micrometer-sized hierarchical materials, for example: tubules-within-tubule and uniform-sized hollow spheres of diameter 5.0 ± 1.0 μm. However, the inside of the micron spheres has intricate structures possessing various topological genus ranks. The MCM-41 is a good supporter for Molybdenum oxide catalysts. The rate of deactivation in the catalytic reaction of ethyl-benzene dehydrogenation to styrene increases in the order: MT < MP < SiO2. The physically mixed samples have higher catalytic activity than impregnated ones. 相似文献