Hollow Spherical Structure Research Articles

The photocatalytic redox properties of polymeric carbon nitride nanocages (PCNCs) with mesoporous hollow spherical structures prepared by a ZnO-template method

Abstract The polymeric carbon nitride nanocages (PCNCs) with mesoporous hollow spherical structures and a spherical shell thickness of ca 50 nm have been successfully prepared via an ZnO-template method, in which the ZnO@PCN core-shell structures were fabricated by simple calcination of ZnO nanospheres and deposited melamine, followed by sequential treatment with hydrochloric acid and aqueous ammonia for thorough removal of ZnO templates and residual Zn2+ ions. The as-prepared pure PCNCs were characterized by various physico-chemical techniques combined with the photocatalytic oxidation reaction of rhodamine B in aqueous solution and the photocatalytic hydrogen evolution reaction under visible light irradiation. The photocatalytic evaluation results indicate that the PCNCs catalysts show higher activity for both photocatalytic reactions than the bulk PCN catalysts prepared by conventional calcination method. The characterization results have shown that the enhanced photocatalytic properties of PCNCs catalysts are mainly attributed to their larger specific surface area, more mesoporous in the range of 2–50 nm, lower band gap energy, higher visible light absorbance and more efficient electron-hole separation in the shell of hollow spherical nanocages than those of bulk PCN. Moreover, the PCNCs catalysts with hollow spherical structures exhibit an excellent reusability in both photocatalytic reactions.

A functionalized chitosan wrinkled hollow sphere containing calcium ions: Efficient adsorption of sodium dodecylbenzenesulfonate (SDBS) from aqueous solutions

In this study, a novel chitosan material (ECS@Ca@CTA) was prepared to significantly adsorb sodium dodecylbenzene sulfonate (SDBS). First, chitosan is complexed with CaCl2 and crosslinked into hollow spheres by glutaraldehyde (GA). However, a part of the active groups (amino group) is depleted. The amino group is crucial in CS, which can adsorb anions under acidic aqueous solutions and be functionalized by other groups. Therefore, the amino group is reactivated by ethylenediamine (EDA), then the ECS@Ca is quaternized by (3-chloro-2 hydroxypropyl) trimethylammonium chloride (CTA) and prepared to hollow sphere structure with wrinkled surface in order to improve the effect of pH on adsorption of SDBS. It is not only a simple functionalization, but a synergistic effect between the three materials (ECS@Ca@CTA) to efficiently adsorb SDBS. Thus the maximum adsorption capability of ECS@Ca@CTA is 2430, 1967 and 1116 mg g−1 at pH 3.0, 7.0 and 10.0 for SDBS, respectively. The adsorption kinetics, adsorption isotherm and reusability of ECS@Ca@CTA were studied. This paper is to provide a new environmentally friendly adsorbent material to adsorb SDBS.

Preparation and luminescent properties of CaCO3:Eu3+ hollow sphere by co-precipitation method

In order to improve its tracking applications, Eu3+ doped calcium carbonate (CaCO3:Eu3+) hollow spheres with red light emission were prepared using soft template method. XRD and SEM results revealed that the prepared CaCO3:Eu3+ has vaterite and calcite structures, and the vaterite CaCO3:Eu3+ with hollow spherical structure were expected. The freeze-drying method was used to obtain a better hollow spherical structure after the precipitation of CaCO3 sample. When surfactant amount was used exceed 0.2 mol/L, the CaCO3 with hollow spherical structure was destroyed. Under excitation at 393 nm, the as-prepared CaCO3:Eu3+ hollow spheres exhibit a red emission peak at 618 nm, due to the 5D0→7F2 electronic transition of Eu3+, which is expected to be used in medicine as a probe to track the location of drugs in the human body.

Novel activated N-doped hollow microporous carbon nanospheres from pyrrole-based hyper-crosslinking polystyrene for supercapacitors

Here, pyrrole-based hollow microporous organic nanospheres (Py-HMONs) were firstly synthesized through co-hyper-cross-linking of pyrrole and polylactide-b-polystyrene (PLA-b-PS) diblock copolymers based on Scholl reaction. The effect of diblock copolymers and pyrrole amount on the morphology of Py-HMONs was discussed. Py-HMONs can be further transformed into activated N-doped hollow microporous carbon nanospheres (AN-HMCNs) with enhanced high surface area (1347 m2 g−1) by a simply KOH-activated pyrolyzing treatment. Owing to high surface area, unique hollow spherical structure and nitrogen heteratom doping, the obtained AN-HMCNs as supercapacitor electrodes deliver a high specific capacitance of 395 F g−1 at a current density of 1 A g−1. More remarkably, AN-HMCNs electrodes exhibit outstanding cycling stability with almost no decrease over 10000 cycles at a current density of 10 A g−1. This work provide a new avenue to prepare activated hollow porous carbon nanospheres with high surface area and nitrogen-doping for high-performance supercapacitor applications.

MOF-derived bimetal oxides NiO/NiCo2O4 with different morphologies as anodes for high-performance lithium-ion battery

Bimetal oxides NiO/NiCo2O4 were successfully fabricated by using metal-organic frameworks (MOFs) as the precursor. The prepared NiO/NiCo2O4 showed hollow sphere and rod-like structures, respectively. When evaluated as an anode material for lithium-ion battery, a sphere-like NiO/NiCo2O4 showed an initial discharge capacity of 1778 mAh/g and reversible capacity of 920 mAh/g at 100 mA/g after 100 cycles. And a rod-like NiO/NiCo2O4 displayed initial discharge capacity of 1800 mAh/g and stabilized at an average capacity of 1198 mAh/g after 100 cycles. The results showed that the materials with the rod-like structure were much more stable and had better rate capability and more superior cyclic stability. The rod-like structure had a shorter transmission distance of Li+, which could maintain its stable rod-like structure in the long-term cycle. This strategy could shed light on designing stable electrode materials for conversion devices and energy storages.

A facile synthesis of nitrogen-doped hierarchical porous carbon with hollow sphere structure for high-performance supercapacitors

In this work, nitrogen-doped carbon with hierarchical porous and hollow sphere structure has been synthesized through a simple and facile route of spray drying using glycine as the nitrogen-containing carbon source. After KOH activation, the prepared material (NHPCA) shows a large specific surface area of 962 m2 g−1 with moderate N-doping of 5.74% and exhibits a high specific capacitance of 271 F g−1 in 6 M KOH electrolyte at 1.0 A g−1, remarkable rate capability and particularly stable cycling performance with no significant specific capacitance drop after 10000 cycles at 1.0 A g−1. The excellent electrochemical properties come from the unique structure and the doping of nitrogen. The hierarchical pore structure improves the efficiency of electrolyte ions transport, and diffusion and the hollow sphere structure further facilitates mass transport. The doping of nitrogen increases the total capacitance by providing redox pseudo-capacitance. The results indicate the as-prepared nitrogen-doped carbon with hierarchical porous and hollow sphere structure can be used as a hopeful candidate for an efficient electrode of commercial supercapacitors devices.

Fabrication and magnetic transformation from paramagnetic to ferrimagnetic of ZnFe2O4 hollow spheres

Abstract ZnFe2O4 hollow spheres (ZFHs) with sizes of 200–302 nm were synthesized by simple impregnating method using the as-prepared phenolic formaldehyde (PF) spheres as templates and subsequent annealing at 500–700 °C. The prepared ZFHs are assembled by a large number of small nanoparticles with sizes of 15–20 nm, and many mesopores exist among these nanoparticles. The samples annealed at 500–550 °C exhibit a single cubic spinel structure, while higher annealing temperature leads to the formation of hexagonal ZnO and rhombohedral α-Fe2O3 secondary phases. The size of the assembled nanoparticles increases with the increase in annealing temperature. Novel magnetic transformation from paramagnetic to ferrimagnetic is induced by the reduction of annealing temperature and the saturation magnetization significantly increases from 2.3 to 13.5 A·m2/kg. The effect of the formation of hollow sphere structure on the redistribution of Fe3+ and Zn2+ in the spinel structure was studied.

Badania struktur komórkowych typu hollow sphere wytwarzanych metodą selektywnego spiekania laserowego

The research of hollow sphere structures as absorbers of mechanical energy is described. The first part of the article is devoted to the description of selective laser sintering additive technique as the optimal method of sample production in the case of laboratory tests. The next part presents the use of computer aided design to create parametric three-dimensional models. Next, the results of experimental tests in the conditions of quasi-static load are presented. Based on the collected data, a qualitative analysis of the structure deformation process was performed and final conclusions are presented.

Monodispersed platinum nanoparticles embedded in Ni3S2-containing hollow carbon spheres with ultralow Pt loading and high alkaline hydrogen evolution activity

The design and fabrication of efficient Pt-based electrocatalysts with ultralow-loading but high-mass-activity for hydrogen evolution reaction (HER) in alkaline media is of significant importance. Herein, we report the monodispersed platinum nanoparticles (PtNPs) with an ultralow Pt loading (3.6 μg per electrode area (cm2)) embed in Ni3S2-containing hollow carbon spheres as HER catalysts. Notably, the as-prepared electrocatalyst exhibits a mass activity of 7.6 A gPt−1 at an overpotential of 70 mV, which is 8.5 times higher than that of commercial Pt/C and is among the highest levels of reported Pt-based HER electrocatalysts in alkaline conditions. This electrocatalyst also exhibits excellent HER performance with an overpotential of 42 mV reaching an area current of 10 mA cm−2 and significantly improved stability. The outstanding HER performance is attributed to the hollow and porous carbon spherical structure, as well as highly dispersed PtNPs that provide more active sites and facilitate proton/electron transport. Meanwhile, the nickel-containing layered precursors convert to some Ni3S2 NPs which guarantees the formation of Pt-Ni3S2 heterostructures on the carbon substrate and thus further enhance the activity of PtNPs. This work provides an effective strategy to simultaneously regulate the nanostructure and active site of Pt-containing carbon-based HER electrocatalysts.

Dynamic responses and energy absorption of hollow sphere structure subjected to blast loading

Closed-cell and open-cell hollow spheres were designed to develop lightweight cellular structures with excellent blast resistance, and the mechanical response of the hollow sphere structure (HSS) under blast loading was investigated numerically using ANSYS®/LS-DYNA®17.0. In this paper, the blast wave pressure decay rate was served as the main index of blast resistance while areal specific energy absorption and frame deformation were used as auxiliary indexes. The results indicated that the weight of HSS was reduced by 37.7%–69.8% compared to solid structures with the same physical size, and the blast resistance of HSS was significantly affected by the hollow sphere diameter and wall thickness, frame length and width, opening size and opening density. Closed-cell HSS with smaller hollow sphere diameters and thicker wall, or smaller frame lengths and widths would achieve the optimal blast resistance. Meanwhile, the blast resistance of HSS could be improved by adopting a smaller opening size, but the effect of opening density did not follow any rule, which was affected by the number and position of openings. Comprehensively, the blast resistance of HSS was enhanced when there was opening only at the face blast surface rather than at both the face blast surface and back blast surface.

Three-dimensional ordered hollow sphere composite Pt/TiO2-ZrO2: enhanced performance of photocatalytic degradation and photocatalytic hydrogen evolution

In this paper, a three-dimensional ordered hollow sphere (3DOH) structure composite Pt/TiO2-ZrO2 was prepared by using polystyrene (PS) colloidal spheres as the template and combining with two-step vacuum impregnation method, of which the composition, crystalline structure, morphology, and surface physicochemical properties were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance (UV-vis/DRS), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and nitrogen adsorption-desorption measurements. The results illustrate the crystal type of 3DOH Pt/TiO2-ZrO2 is mainly anatase TiO2 and tetragonal ZrO2 phase, which exhibits a three-dimensional ordered hollow sphere structure. Hollow spheres are arranged orderly; moreover, the composite shows a strong absorption in the visible region due to the effect of surface plasmon absorption (SPA) after doping Pt nanoparticles. Meanwhile, the photocatalytic activity of 3DOH Pt/TiO2-ZrO2 was investigated by using Congo red as the model molecule. The results show that 3DOH Pt/TiO2-ZrO2 has good photocatalytic activity under multi-modes photocatalytic experiments, and its activity is higher than that of P25, ZrO2, and other Pt/TiO2-ZrO2 not treated by PS colloidal spheres. In addition, the total amount of hydrogen production of 3DOH Pt/TiO2-ZrO2 is 100 times as much as the commercial P25 in the photocatalytic hydrogen evolution experiment (8 h), which shows an excellent photolysis of water hydrogen production activity.

Spatially separated CdS hollow spheres with interfacial charge transfer and cocatalyst for enhancing photocatalytic hydrogen evolution

To improve the efficiency of photocatalytic H2 evolution, comprehensive utilization of constructing heterojunction, designing structure and loading cocatalyst is imperative. In this study, a novel hollow sphere photocatalyst (MnOx/CdS/CuS) driven by constructing CdS/CuS heterojunction induced interfacial charge transfer (IFCT) and loading MnOx as cocatalyst was realized. CuS is deposited on the outside of the CdS shell, and MnOx is anchored on the inside, thus photoinduced electrons and holes were spatially separated due to this hollow spherical structure. As expected, the H2 evolution rate of MnOx/CdS/CuS is 18 times higher than that of pure CdS, besides, MnOx/CdS/CuS exhibited excellent stability in cycle experiments. This work opens a rational direction for design spatially separated photocatalytic systems to enhance photocatalytic H2 evolution.

Controlled synthesis of N-doped carbon microspheres from melamine-based carbon by chemical vapor deposition

N-doped carbon hollow microspheres (NCMs) have been prepared by a facile water-assisted chemical vapor deposition (CVD) process using melamine as both the carbon precursor and N-dopant and ferrocene as both the catalyst and carbon precursor. It is shown that the size of the NCMs can be tuned just by changing the annealing temperature of the CVD furnace. The atomic percentage of nitrogen doping in NCMs could be achieved to 7.85% without sacrificing the hollow spherical structure. Probable growth mechanism of NCMs was proposed in this paper. The work reported here may pave a way for designing novel various atom-doped carbon microspheres.

Optical and photoluminensce properties of Eu2+-activated strontium magnesium silicate phosphors using different rare earth co-activators

Nanostructured powders of Sr1.96MgSi2O7:Eu 0.01 2+ , R 0.01 3+ (R3+ = Er3+, Tm3+ and Tb3+) have been fabricated via urea combustion technique. XRD results implied that tetragonal Sr2MgSi2O7 was the major phase whereas monoclinic Sr2SiO4 and SrSiO3 were the minor phases. Meanwhile, field emission SEM textures showed the hollow spherical network-like shape structures filled with fused interconnections for the Sr1.96MgSi2O7:Eu 0.01 2+ sample. It has been recognized that the replacement of Sr2+ with co-dopant R3+ ions e.g. Er3+, Tm3+ and Tb3+ considerably help obtaining homogeneous structure as well. The values of band gap energy and calculated refractive index were ultimately dependant on the ionic radius of R3+ co-doping ion. It has been suggested that the divalent activator ion (Eu2+) was responsible for the number of PL emission spectra, while the trivalent co-activator ions (R3+) were the key reasons for variations in the broadening and intensity of PL emission spectra.

The effect of monovalent anion species on the aggregation and charging of allophane clay nanoparticles

Allophane is a kind of clay mineral which has amorphous hollow spherical structure. To clarify the dispersion, aggregation and charging behaviour of allophane in the presence of various monovalent anions, F−, Cl−, Br−, I−, BrO3−, IO3−, and SCN−, the stability ratio and electrophoretic mobility of allophane were investigated. The stability ratio was obtained from the temporal change in the average hydrodynamic diameter of allophane measured by dynamic light scattering. The charging behaviour was evaluated from the measurement of electrophoretic mobility (EPM) of allophane. These experiments were performed as a function of electrolyte concentration at pH 5, where the net charge of allophane is positive. The experimental results demonstrated that the stability ratio decreased with increasing the salt concentration and finally it became unity independent of the salt concentration. Consequently, we observed slow aggregation regime, fast aggregation regime, and critical coagulation concentration (CCC). Therefore, the stability ratio follow the classical theory of Derjaguin, Landau, Verwey, Overbeek (DLVO) at least qualitatively. However, the CCC of allophane showed difference for each anion species; the CCC followed the order F− < IO3− < Cl− < SCN− < BrO3− < Br− < I−. We also confirmed the difference in EPM among anion species; the reduction of EPM magnitude was significant for well-hydrated ions. We presume that the CCC and EPM of allophane depend on the affinity of anions to the allophane surface characterized by the degree of hydration of each ion. That is, well-hydrated anions can adsorb to the hydrophilic surface of allophane and effectively decrease the positive charge of allophane. Besides this, the fluoride ion induced much lower CCC and charge reversal. These results are due to the strong affinity of fluoride ion for the allophane surface. Meanwhile the dependence of CCC on the zeta potential followed the DLVO prediction. Although the zeta potential of allophane is affected by anion species, the CCC behaviors can be understood by the DLVO theory through the evaluation of zeta potential of allophane. This means that the measurement of stability ratio and electrophoretic mobility accompanied with the DLVO theory are valuable tools for the understanding of the aggregation-dispersion of charge-stabilized natural clays.

Fabrication of NixCo3-xS4 hollow nanosphere as wideband electromagnetic absorber at thin matched thickness

Abstract Nowadays, transition metal sulfide (TMS), especially for spinel crystal structure (AxB3-xS4), have been proved to be a promising electromagnetic (EM) absorber if been used to deal with the severe electromagnetic pollution. However, EM performance degradation and absorption layer thickness-decreasing at present remains a big challenge, owning to the poor EM attenuation ability. To overcome this barrier, herein we reported a NixCo3-xS4 (x = 0, 0.3, 0.6, 1.0) absorber with hollow sphere structure to realize a good EM performance with a thinner matched thickness (

Interconnected hollow carbon spheres with tunable wall-thickness for improving the high-rate performance of energy storage devices

We report a facile synthetic method to produce the interconnected hollow carbon spheres with various wall-thickness (as low as 9 nm). Instead of synthesizing and dispersing the silica hard templates in advance, we produce the templates in-situ to form the interconnected hollow-sphere structure. This interconnected structure provides a fast and efficient pathway for electron transfer. Meanwhile, decreasing the wall-thickness effectively shortens the distance of ion diffusion, which further promotes the high-rate performances of the interconnected hollow carbon spheres. For supercapacitor applications, at 1 A g−1, the MF-1.1-20 (with 9-nm wall-thickness) electrode demonstrates a high specific capacitance of 208 F g−1 and retains 93% of its initial capacity after 10000 cycles. Under a large current density of 20 A g−1, MF-1.1-20's specific capacity remains 153 F g−1, demonstrating excellent high-rate performances. In another aspect, as the electrode for lithium-sulfur battery, MF-1.1-20/S composite electrode demonstrates high specific capacity of 996 mAh g−1 and 465 mAh g−1 at 0.2C and 10C, respectively. The excellent electrochemical behavior of the interconnected hollow carbon spheres demonstrates their potential for applications in high-rate energy storage devices.

Preparation of Graphene–Polypyrrole Hollow Sphere by Pickering Emulsion Method and Their Electrochemical Performances as Supercapacitor Electrode

Graphene–polypyrrole hollow sphere composite was synthesized for the first time via Pickering emulsion polymerization using graphene oxide as Pickering stabilizer. It was found that polypyrrole and graphene were well hybrid and all graphene–polypyrrole composites had a uniform hollow sphere structure, whose diameters gradually decreased as the pyrrole content decreased. The electrochemical properties of the composites as supercapacitor electrode were investigated. The test results displayed that the specific capacitance of the optimal ratio of composite could reach 238[Formula: see text]F/g at a current density of 1[Formula: see text]A/g, and a 90.7% capacitance retention could be achieved after 1500 cycles, which was a significant improvement compared with the 62.2% retention of pure polypyrrole.

Experimental investigation on cenosphere-based paper battery and electrochemical battery

ABSTRACTFly-ash is a by-product of various thermal power plants. The utilization of fly-ash is a big concern in the current scenario as its production rate is much higher than its consumption rate. Cenosphere is one of the most value-added fractions of coal fly-ash. It has a hollow spherical structure and can be applied in many industrial applications, due to its superior properties, such as low bulk density, good thermal resistance, high strength, etc. The present work deals with the usage of fly-ash cenosphere to develop the paper battery and electrochemical battery. The study demonstrates the process of chemical deposition of Cu-ion on cenosphere by electro-less plating technique using silver-nitrate as an activator. Subsequently, metal-ion-coated cenosphere is used for developing the paper battery and electrochemical battery; testing is done by measuring the open circuit voltage (OCV) and by analyzing the discharge curves of battery. The present work analyzes various factors and characteristics affecting the performance of developed batteries.The objective of present work is to explore the applications of low-cost materials like cenosphere, ordinary paper, cotton-balls and aluminum powder for developing thinner batteries like paper battery. The results confirm that the copper-ion-coated cenosphere can be successfully applied for developing electrochemical battery.

In-situ solvothermal phosphorization from nano-sized tetragonal-Sn to rhombohedral-Sn4P3 embedded in hollow graphene sphere with high capacity and stability

Tin phosphide (Sn4P3) has a high theoretical specific capacity as anode material for lithium-ion batteries, nevertheless the large volumetric expansion during lithium insertion and Li-Sn alloying suppresses its application. Herein, we design sandwiched hollow spherical graphene-wrapping Sn4P3 nanoparticles composite by in-situ solvothermal phosphorization from nano-sized tetragonal-Sn. The product perfectly inherits the sandwich hollow spherical structure from the Sn precursor, a stable and high content COP covalent bond is formed between the Sn4P3 active substrate and graphene skeleton to improve the binding force and electrical conductivity. More importantly, the layer-structure Sn4P3 nanoparticles (20–50 nm) are inserted in the loosely stacking graphene shells, thus the radial volume expansion along c-axis and Sn aggregation can be effectively buffered. The synergy effect provides the transformed product with fewer structural changes comparing with metal Sn anodes, lithiation-generated Li3P and Sn can inter-support for each other to promote the conversion reaction with high reversibility. Thus, the sandwich-Sn4P3/spherical graphene composite exhibits excellent structural integrity and cycling stability, a high reversible capacity of 606.4 mAh g−1 is preserved at a rate of 0.1C over 100 cycles.