Composite Spheres Research Articles

Hollow Carbon Sphere and Polyhedral Carbon Composites Supported Iron Nanoparticles as Excellent Bifunctional Electrocatalysts of Zn–Air Battery

Herein, we synthesize Fe‐based nanocatalysts supported on the composites composed of hollow carbon spheres (HCSs) and metal–organic frameworks (MOFs) by a facile pyrolysis method. The composites with different ratios of HCSs and MOFs present an interesting phenomenon: the oxygen reduction reaction (ORR) limiting current increases along with the HCSs content, while the onset potential and half‐wave potential show the highest values when the ratio between HCSs and MOFs is optimized. The composite catalysts exhibit superior ORR electrocatalytic performance than Pt/C in alkaline and neutral media. Even in the acidic media, these composite catalysts still present a close catalytic activity to Pt/C. For the oxygen evolution reaction (OER) test, the prepared Fe‐NC@NHCS‐600 shows a reduced overpotential to that of the benchmark IrO2. The rechargeable Zn‐air battery using Fe‐NC@NHCS‐600 as the catalyst of air electrode exhibits superior discharge capability with an open‐circuit voltage of 1.620 V and a maximum power density of 278.97 mW cm−2 in alkaline electrolyte, as well as an open‐circuit voltage of 1.457 V and a maximum power density of 114.96 mW cm−2 in neutral electrolyte. The battery also exhibits steady cycling stability for more than 90 and 70 h at 5 and 10 mA cm−2, respectively.

A novel bio-inspired metal hollow sphere filled TC4/Al sandwich composite: Fabrication and compressive properties

A novel bio-inspired metal hollow sphere filled TC4/Al sandwich composite was proposed based on the cognition of biological materials with TC4/Al metal laminated composites (MLCs) as outer layers and metal hollow sphere composite (MHSC) made from 316 L stainless steel (316 L SS) metal hollow spheres (MHSs) and Al powder matrix as inner core. The sandwich composite was sintered by the hot pressing method in a one-step process. Scanning electron microscopy (SEM) observation, energy dispersive spectrometer analysis (EDS), and X-ray diffraction (XRD) analysis were carried for characterization on multiple interfaces. Al3Ti intermetallic compound layers were formed between laminations and 316 L/Al interfaces with Fe-Al intermetallic compounds were formed between 316 L SS MHSs and Al matrix in MHSC inner core. Compressive stress-strain curves of the sandwich composite exhibited the combination characteristic of the comparison MHSC and MLC curves. The deformation behavior of the sandwich composite was first dominated by MHSC inner core and then by MLCs outer layers. Failure modes and interface effects were also studied.

The Effect of the Modification of Carbon Spheres with ZnCl2 on the Adsorption Properties towards CO2.

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.

Remediation of Cd (II) ions in aqueous and soil phases using novel porous cellulose/chitosan composite spheres loaded with zero-valent iron nanoparticles

Novel porous cellulose/chitosan composite spheres loaded with nanoscale zero-valent iron (nZVI/PCSs) were fabricated for the removal of Cd (II) from aqueous solution and the remediation of Cd species in contaminated soil. The green-based nZVI/PCSs exhibited the improved dispersion and antioxidability of nZVI compared to the pristine one. The results from SEM/EDS suggested that the Fe (0) took part in the adsorption of the Cd (II) ions; whereas XPS analysis revealed that Fe (0) and amino groups in nZVI/PCSs played crucial roles in Cd (II) removal via the effects of precipitation or chelation. The results of the experiments in aqueous solution and model fitting showed that the adsorption of Cd (II) induced by nZVI/PCSs was better described by Langmuir isotherm and the maximum adsorption capacity reached up to 110.3 mg/g. The soil remediation tests demonstrated that nZVI/PCSs could significantly enhance cadmium immobilization, enabling the conversion of most exchangeable Cd species to FeMn oxides and organic matters in contaminated soil after the remediation. Overall, nZVI/PCSs have great potential as an excellent adsorbent with cost-effectiveness in Cd (II) removal from the aqueous solution and the remediation of Cd species in contaminated soil phases.

Surface ligand modified cesium lead bromide/silica sphere composites for low-threshold upconversion lasing

In recent years, all-inorganic halide perovskite quantum dots (QDs) have drawn attention as promising candidates for photodetectors, light-emitting diodes, and lasing applications. However, the sensitivity and instability of perovskite to moisture and heat seriously restrict their practical application to optoelectronic devices. Recently, a facile ligand-engineering strategy to suppress aggregation by replacing traditional long ligands oleylamine (OAm) during the hot injection process has been reported. Here, we further explore its thermal stability and the evolution of photoluminescence quantum yield (PLQY) under ambient environment. The modified CsPbBr 3 QDs film can maintain 33% of initial PL intensity, but only 17% is retained in the case of unmodified QDs after 10 h continuous heating. Further, the obtained QDs with higher initial PLQY (91.8%) can maintain PLQY to 39.9% after being continuously exposed in air for 100 days, while the PLQY of original QDs is reduced to 5.5%. Furthermore, after adhering CsPbBr 3 QDs on the surface of a micro SiO 2 sphere, we successfully achieve the highly-efficient upconversion random laser. In comparison with the unmodified CsPbBr 3 QDs, the laser from the modified CsPbBr 3 QDs presents a decreased threshold of 79.81 μJ / cm 2 and higher quality factor ( Q ) of 1312. This work may not only provide a facile strategy to synthesize CsPbBr 3 QDs with excellent photochemical properties but also a bright prospect for high-performance random lasers.

The Neutral Protease Immobilization: Physical Characterization of Sodium Alginate-Chitosan Gel Beads.

Sodium alginate and chitosan were cross-linked to form composite gel spheres, which were entrapped to immobilize the free neutral protease. The matrix of the immobilized neutral protease was detected and characterized by using Fourier transform infrared spectroscopy and energy-dispersive X-ray. The optimum immobilization conditions were determined by orthogonal test, in which the concentration of sodium alginate was 3.5%, CaCl2 2.5%, chitosan 2.5%, and immobilizing time 1.5h. Meanwhile, the activities of immobilized neutral protease and free enzyme were compared. The results showed that the pH value of immobilized enzyme was 5-8, the relative activity was above 90%, the free enzyme was above 80%, the relative activity of immobilized enzyme was above 80% in 30-80°C, and the free enzyme was above 64% in 40-80°C. The immobilized enzyme is better than the free enzyme in the constant of pH and temperature. The relative activity of immobilized enzyme was 50% after six hydrolysis cycles, and 80% after 11days of storage.

Study on the homogeneous design of ultra-thin protonated g-C3N4 composite TiO2 hollow spheres and its photocatalytic performance for RHB

Study on the homogeneous design of ultra-thin protonated g-C3N4 composite TiO2 hollow spheres and its photocatalytic performance for RHB

Carbon-encapsulated core-shell structure ZnFe2O4 sphere composites coupled with excellent microwave absorption and corrosion resistance.

Microwave absorbing materials (MAMs) have been identified as an efficient means to solve major electromagnetic pollution problems. Current core-shell composite MAMs are fabricated as single magnetic cores with dielectric shells, yielding decreased magnetic couplings and impedance mismatches. Herein, carbon shell encapsulated core-shell structured zinc ferrate (ZnFe2O4) sphere composites (CSZF@C) were fabricated using a hydrothermal method and subsequent carbonisation process. The complex permittivity and complex permeability of CSZF@C can be effectively adjusted by varying the parameters of the outer carbon shell. The synergistic effect of carbon shell and inner core-shell structured ZnFe2O4 (CSZF) not only meets impedance matching but also improves electromagnetic energy loss, a result of the unique microstructure. CSZF@C-1 exhibited a considerable reflection loss (RL) of -53.5 dB and an effective absorption bandwidth (EAB) of up to 6.56 GHz, the thickness is only 2.94 mm. Meanwhile, the epoxy resin coating of CSZF@C-1 substantially increases the corrosion resistance of the metal substrate owing to carbon encapsulation. This study presents new ideas for designing efficient multifunctional nanocomposites with high microwave absorption and corrosion resistance.

Removal of Pb(Ii), Cd(Ii), Cu(Ii), Cr (Vi), Acid Red 1, Phenol and Toluene Using Carbon Sphere and Layered Double Hydroxide Composites

Removal of Pb(Ii), Cd(Ii), Cu(Ii), Cr (Vi), Acid Red 1, Phenol and Toluene Using Carbon Sphere and Layered Double Hydroxide Composites

High-Efficiency Graphene Oxide Membranes Intercalated by Hollow Tio2 Nanospheres and Cns@Ldh Composite Spheres for Enhancing Dye Separation from Wastewater

High-Efficiency Graphene Oxide Membranes Intercalated by Hollow Tio2 Nanospheres and Cns@Ldh Composite Spheres for Enhancing Dye Separation from Wastewater

Effect of Preparation Process on Microstructure and Mechanical Properties of Metal Hollow Sphere Composites (Mhscs)

Effect of Preparation Process on Microstructure and Mechanical Properties of Metal Hollow Sphere Composites (Mhscs)

Carbon Encapsulated Core-Shell Structure Znfe2o4 Sphere Composites Coupled with Excellent Microwave Absorption and Corrosion Resistance

Carbon Encapsulated Core-Shell Structure Znfe2o4 Sphere Composites Coupled with Excellent Microwave Absorption and Corrosion Resistance

DEVELOPMENT OF LOW-MELTING GLASSCERAMIC BONDS FOR HIGH RESOURCE DIAMOND-ABRASIVE TOOLS

Research is aimed at creating high-resource diamond-abrasive tools with a large-pore structure of the working layer, the use of which reduces the occurrence of grinding defects when processing materials sensitive to overheating. The formation of an open structure of the working layer ensures effective chip removal, which excludes a decrease in the сutting ability of the tool due to contamination with grinding sludge and creates favorable conditions for intensifying the processing of materials when using high-speed cutting modes. As part of the research, low-melting glass-ceramic binders for diamond-abrasive tools have been developed, which make it possible to increase the tool service life due to the prevention of diamond grains premature destruction and the creation of a large-pore open structure of the working layer. Using a set of calculated data about the main characteristics of glass compositions by factor planning means, the dependences «composition - properties» were determined and the area of optimal compositions of glass-ceramic bonds was established, which ensure sintering of a diamond-containing composite at a temperature of 550–650 °C. The efficiency of the use of alumino-silicate microspheres of technogenic origin as a structure-forming filler providing the formation of a large-pore structure is shown. The features of the chemical and phase composition of the technogenic spheres recovered from the fly ash of the Krivoy Rog TPP have been determined. It has been established that when the diamond-bearing layer of the tool is sintered in the shell of the ash spheres, crystalline new formations with high hardness (hercynite, mullite, maghemite, spinel) are formed. Using ash spheres and developed low-melting binders, which include up to 30 mass. % of glass waste, the laboratory samples of diamond-containing composites with open porosity of 45-50% were made. Studies of their microstructure and morphological features made it possible to determine the pore size (130-200 μm) and establish that during grinding, partial destruction of ash spheres occurs with the formation of additional cutting elements, which increases the tool cutting ability. The research results indicate the advisability of using the proposed approach for selection of the diamond-ceramic composite components and the modes of heat treatment of the diamond-bearing layer when creating a tool. This approach will significantly expand the possibilities of manufacturing large-pore diamond-abrasive tools with a high service life at minimal material costs and will improve the processing of parts made of difficult-to-machine materials.

Development and Application of Nanoparticle-Nanopolymer Composite Spheres for the Study of Environmental Processes.

Plastics have long been an environmental contaminant of concern as both large-scale plastic debris and as micro- and nano-plastics with demonstrated wide-scale ubiquity. Research in the past decade has focused on the potential toxicological risks posed by microplastics, as well as their unique fate and transport brought on by their colloidal nature. These efforts have been slowed by the lack of analytical techniques with sufficient sensitivity and selectivity to adequately detect and characterize these contaminants in environmental and biological matrices. To improve analytical analyses, microplastic tracers are developed with recognizable isotopic, metallic, or fluorescent signatures capable of being identified amidst a complex background. Here we describe the synthesis, characterization, and application of a novel synthetic copolymer nanoplastic based on polystyrene (PS) and poly(2-vinylpyridine) (P2VP) intercalated with gold, platinum or palladium nanoparticles that can be capped with different polymeric shells meant to mimic the intended microplastic. In this work, particles with PS and polymethylmethacrylate (PMMA) shells are used to examine the behavior of microplastic particles in estuarine sediment and coastal waters. The micro- and nanoplastic tracers, with sizes between 300 and 500 nm in diameter, were characterized using multiple physical, chemical, and colloidal analysis techniques. The metallic signatures of the tracers allow for quantification by both bulk and single-particle inductively-coupled plasma mass spectrometry (ICP-MS and spICP-MS, respectively). As a demonstration of environmental applicability, the tracers were equilibrated with sediment collected from Bellingham Bay, WA, United States to determine the degree to which microplastics bind and sink in an estuary based of grain size and organic carbon parameters. In these experiments, between 80 and 95% of particles were found to associate with the sediment, demonstrative of estuaries being a major anticipated sink for these contaminants. These materials show considerable promise in their versatility, potential for multiplexing, and utility in studying micro- and nano-plastic transport in real-world environments.

Sensitive sandwich-type electrochemical SARS-CoV‑2 nucleocapsid protein immunosensor.

A sensitive and fast sandwich-type electrochemical SARS-CoV‑2 (COVID-19) nucleocapsid protein immunosensor was prepared based on bismuth tungstate/bismuth sulfide composite (Bi2WO6/Bi2S3) as electrode platform and graphitic carbon nitride sheet decorated with gold nanoparticles (Au NPs) and tungsten trioxide sphere composite (g-C3N4/Au/WO3) as signal amplification. The electrostatic interactions between capture antibody and Bi2WO6/Bi2S3 led to immobilization of the capture nucleocapsid antibody. The detection antibody was then conjugated to g-C3N4/Au/WO3 via the affinity of amino-gold. After physicochemically characterization via transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) analysis were implemented to evaluate the electrochemical performance of the prepared immunosensor. The detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP) in a small saliva sample (100.0 µL) took just 30 min and yielded a detection limit (LOD) of 3.00 fg mL−1, making it an effective tool for point-of-care COVID-19 testing.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-021-05092-6.

Solar-driven enhanced chemical adsorption and interfacial evaporation using porous graphene-based spherical composites

Solar-energy-driven water purification is a promising technology for obtaining clean water during the current global climate crisis. Solar absorbers with high light absorption capacity and efficient energy conversion are critical components of solar-driven water evaporation and purification systems. Herein, we demonstrate that porous reduced graphene oxide (rGO)-based composite spheres facilitate efficient water evaporation and effective organic pollutant adsorption from water. Most solar light (>99% for 1 mm thick composites) is absorbed by the porous rGO-based composite spheres floating on water and is subsequently converted into heat, which is efficiently transferred to water at the air–water interface. Evaporation efficiency via energy conversion by the floating sphere composites reaches ∼74%. The increase in surface temperature of water also contributes to improving the adsorption capacity of the rGO-based composite spheres for organic pollutants. Furthermore, the composites can effectively block ultraviolet radiation, preventing the chemical reaction of water pollutants into harmful components.

Synthesis of Chitosan-Silver Nanoparticle Composite Spheres and Their Antimicrobial Activities.

Synthesis of silver nanoparticles–chitosan composite particles sphere (AgNPs-chi-spheres) has been completed and its characterization was fulfilled by UV–vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and zetasizer nano. UV–vis spectroscopy characterization showed that AgNPs-chi-spheres gave optimum absorption at a wavelength of 410 nm. The XRD spectra showed that the structure of AgNPs-chi-spheres were crystalline and spherical. Characterization by SEM showed that AgNPs-chi-spheres, with the addition of 20% of NaOH, resulted in the lowest average particle sizes of 46.91 nm. EDX analysis also showed that AgNPs-chi-spheres, with the addition of a 20% NaOH concentration, produced particles with regular spheres, a smooth and relatively nonporous structure. The analysis using zetasizer nano showed that the zeta potential value and the polydispersity index value of the AgNPs-chi-sphere tended to increase with an increased NaOH concentration. The results of the microbial activity screening showed that the AgNP-chi-Spheres with highest concentration of NaOH, produced the highest inhibition zone diameters against S. aureus, E. coli, and C. albicans, with inhibition zone diameters of 19.5, 18.56, and 12.25 nm, respectively.

Core-Shell SiO2/Ag Composite Spheres Prepared by Electrical Exploding Wire Plasma Technique: Synthesis and Characterization

Core-shell nanoparticles (SiO2/Ag) were manufactured by using a two-step process: Electric detonation of Ag. Wire in colloidal solution particles then by using laser pulses, nanoparticles are released. The structural features of these nanoparticles were checked by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The (XRD) study showed the progressive coverage of SiO2/Ag by nanoparticles according to the energies of the laser pulse. Measurements of morphology and EDX confirmed the Core/shell structure with particle size at the nano level. It confirmed that preliminary analysis consists of a SiO2 core and an Ag shell from FESEM. The surface of the microscopic balls (SiO2) has been covered completely and homogeneously with Ag nanoparticles, Moreover, Ultraviolet-Visible, and by optical absorption spectroscopy, the Nanoparticles with core crust SiO2/Ag showed excellent photocatalytic activities at various concentrations and laser pulse energy.

Preparation and adsorption performance of cellulose nanofibrils/polyvinyl alcohol composite gel spheres with millimeter size

Wastewater treatment is a huge problem facing human beings. The development of recyclable and efficient adsorption materials is of great benefit to solve the problem. Based on the biodegradable cellulose nanofibers (CNFs) derived from biomass resources, the large sized CNFs/PVA composite hydrogel spheres (CV-HSs, 1–3 mm) were successfully prepared by the inverse suspension pellet-forming technology using the polymers as raw materials, and another hydrophobic CNFs/PVA composite aerogel spheres (HCV-ASs) were also obtained by lyophilization and followed silylation of as-prepared CV-HSs. The CV-HSs showed excellent adsorption properties for simulated pollutants, including Cu2+, phenol and aniline in water. The maximum absorption capacity of CV-HSs was 17.22 mmol/g for Cu2+, 176.72 mg/g for phenol and 341.93 mg/g for aniline respectively. The HCV-ASs exhibited good absorption properties for weak polar organic solvents, such as petroleum ether, ethyl acetate and toluene. In summary, two kinds of large-sized CNFs/PVA composite gel spheres were successfully fabricated, and exhibited good adsorption properties for organic pollutants and heavy metal ions, indicating their potential for wastewater treatment.

ZnO/Carbon Spheres with Excellent Regenerability for Post-Combustion CO2 Capture.

This paper examines the synthesis of the ZnO/carbon spheres composites using resorcinol—formaldehyde resin as a carbon source and zinc nitrate as a zinc oxide source in a solvothermal reactor heated with microwaves. The influence of activation with potassium oxalate and modification with zinc nitrate on the physicochemical properties of the obtained materials and CO2 adsorption capacity was investigated. It was found that in the case of nonactivated material as well as activated materials, the presence of zinc oxide in the carbon matrix had no effect or slightly increased the values of CO2 adsorption capacity. Only for the material where the weight ratio of carbon:zinc was 2:1, the decrease of CO2 adsorption capacity was reported. Additionally, CO2 adsorption experiments on nonactivated carbon spheres and those activated with potassium oxalate with different amounts of zinc nitrate were carried out at 40 °C using thermobalance. The highest CO2 adsorption capacity at temperature 40 °C (2.08 mmol/g adsorbent) was achieved for the material after activation with potassium oxalate with the highest zinc nitrate content as ZnO precursor. Moreover, repeated adsorption/desorption cycle experiments revealed that the as-prepared carbon spheres were very good CO2 adsorbents, exhibiting excellent cyclic stability with a performance decay of less than 10% over up to 25 adsorption-desorption cycles.