Hollow Morphology Research Articles

Self-propelled nanoemulsion assembly of organosilane to the synthesis of high-surface-area hollow carbon spheres for enhanced energy storage

Hollow carbon spheres (HCSs) with large interior cavity and porous shell have emerged as an important class of carbon materials, while exploring novel synthesis methods in terms of convenience, controllability and universality remains a challenge. Herein, we develop a self-propelled nanoemulsion assembly of organosilane approach to fabricate monodispersed HCSs. In this approach, volatile oils are severed as self-elimination soft template and organosilane both as carbon precursor and in-situ pore-template. The key to the synthesis is the self-propelled formation of oil-in-water nanoemulsion stabilized by amphipathic hydrolyzed organosilane, which could hydrolyze at the oil-water interface and condense to form the polysilsesquioxane shell. The present approach has good controllability and universality that can be demonstrated by modulating alternative volatile oils, organosilane precursors and dry condition. After carbonization and NaOH treatment, the as-prepared HCSs have uniform particle size of ∼900 nm, large cavity, controllable carbon shell of 80–110 nm, and high surface area up to 2300 m2/g. The unique integration of high-surface-area and well-defined hollow spherical morphology make them a great potential as electrode materials for supercapacitive energy storage and carbon host for lithium sulfur batteries. These findings could inspire more novel methodologies for constructing of high-surface-area yet well-defined nanostructured materials for tackling energy issues.

One-step synthesis of hollow spherical polyethylene by dispersion polymerization

In this paper, ɑ-diimine nickel catalyst without immobilization was successfully used for one-step synthesis of spherical hollow polyethylene particles at mild condition (1.0 MPa, 25 °C) by conducting coordination dispersion polymerization. It was found 2-methyl-2-pentanol (MP) played a key role in the formation of the unusual hollow particular morphology. By varying the addition amount of MP, changing the bulky groups of alkyl aluminum, and adjusting the concentration of nickel catalyst, the particle size was finely tuned. A plausible mechanism was proposed to interpret the formation of these polyethylene hollow particles.

Effect of Crystal Structure and Morphology on Na3V2(PO4)2F3 Performances for Na‐Ion Batteries

AbstractNa‐ion batteries (SIB) are considered promising systems for energy storage devices, however diversity of available cathode materials is lower compared to lithium ion batteries. Recently, Na3V2(PO4)2F3 (NVPF) has been demonstrated as promising cathode material for SIB owing to high specific capacity and electrochemical reversibility. However, most of reports demonstrates capacities lower than theoretical value and optimization of electrochemical performances by controlled morphology and crystal structure was not demonstrated yet. Here, we demonstrate a scalable synthesis strategy to tailor the crystal structure and morphology of NVPF and showed that our approach enables to optimize the Na+ ion accommodation, diffusion and stability. A flower morphology (NVPF‐F) crystalizes in tetragonal structure, demonstrates discharge capacity of 109.5 mA.h.g−1 and 98.1 % columbic efficiency whereas a hollow spherical morphology (NVPF‐S) with orthorhombic structure exhibits discharge capacity of 124.8 mA.h.g−1 (very close to theoretical value) and 99.5 % columbic efficiency. The observed discharge capacity for NVPF‐S is highest reported value which is ascribed due to stable crystal structure and monodispersed morphology. Long term stability with negligible capacity loss is demonstrated over 550 cycles. Our findings shed light on importance of crystal structure and morphology of NVPF on electrochemical response, and realization as cathode material for SIB.

Polycation-Carbon Nanohybrids with Superior Rough Hollow Morphology for the NIR-II Responsive Multimodal Therapy.

Polymer-inorganic hybrid nanomaterials have attracted much attention for the multimodal cancer therapy, while it is still desirable to explore hybrids with superior morphologies for two or more therapeutic modalities. In this work, four types of carbon nanoparticles with distinct morphologies were prepared by an elaborate template-carbonization corrosion process and then functionalized with a similar amount of the superior polycationic gene vector, CD-PGEA [consisting of one β-cyclodextrin core (CD) and two cationic ethanolamine-functionalized poly(glycidyl methacrylate) (PGEA) arms] to evaluate the morphology-influenced gene and photothermal (PT) therapy. Benefiting from the starting rough hollow nanosphere (RHNS) core, the resultant nanohybrids RHNS-PGEA exhibited the highest gene transfection (including luciferase, fluorescent protein plasmid, and antioncogene p53) and NIR PT conversion efficiency among the four types of nanohybrids. Moreover, the efficient PT effect endowed RHNS-PGEA with PA imaging enhancement and an effective imaging guide for the tumor therapy. In addition, anticancer drug 10-hydroxy camptothecin was successfully encapsulated in RHNS with polycation coating, which also displayed the second near-infrared (NIR-II)-responsive drug release. Taking advantages of the superior gene delivery/PT effect and NIR-II-enhanced drug delivery, RHNS-PGEA realized a remarkable therapeutic effect of trimodal gene/PT/chemotherapy of malignant breast cancer treatment in vitro and in vivo. The present work offers a promising approach for the rational design of polymer-inorganic nanohybrids with superior morphology for the multimodal cancer therapy.

Surface-induced reversal of a phase transformation for the synthesis of ε-Fe2O3 nanoparticles with high coercivity

A metastable ε-polymorph of iron(III) oxide (ε-Fe2O3) is a very attractive material from the technological, engineering, and scientific points of view. In comparison with other iron oxides, it is characterized by unusual magnetic properties and a giant coercivity of ~20 kOe, which is the largest value among metal oxides. The routine method of ε-Fe2O3 formation is based on the thermal annealing of maghemite (γ-Fe2O3) nanoparticles confined in a silica matrix where the ε-Fe2O3 appears as an intermediate phase between the maghemite and an α-polymorph (α-Fe2O3) hematite (γ→ε→α pathway). In this study, it is demonstrated that the ε→α transformation can be reversed when hematite nanoparticles with an anisotropic hollow morphology are annealed above 600 °C. The observed reversal of the phase stability is explained in terms of an increased nanoparticle surface area and surface energy related to the hollow structure. This study demonstrates the applicability of surface-induced phase transformation to stabilize and control ε-Fe2O3 nanostructures with anisotropic shape and high coercivity ~1600 kA/m that is one of the key properties of functional magnetic materials for information processing and storage. The understanding of ε-Fe2O3 formation mechanism can provide a new viewpoint and guidance for designing metastable polymorphs and applicative properties.

ALMA reveals a large structured disk and nested rotating outflows in DG Tauri B

We present Atacama Large Millimeter Array (ALMA) Band 6 observations at 14−20 au spatial resolution of the disk and CO(2-1) outflow around the Class I protostar DG Tau B in Taurus. The disk is very large, both in dust continuum (Reff, 95% = 174 au) and CO (RCO = 700 au). It shows Keplerian rotation around a 1.1 ± 0.2 M⊙ central star and two dust emission bumps at r = 62 and 135 au. These results confirm that large structured disks can form at an early stage where residual infall is still ongoing. The redshifted CO outflow at high velocity shows a striking hollow cone morphology out to 3000 au with a shear-like velocity structure within the cone walls. These walls coincide with the scattered light cavity, and they appear to be rooted within < 60 au in the disk. We confirm their global average rotation in the same sense as the disk, with a specific angular momentum ≃65 au km s−1. The mass-flux rate of 1.7−2.9 × 10−7 M⊙ yr−1 is 35 ± 10 times that in the atomic jet. We also detect a wider and slower outflow component surrounding this inner conical flow, which also rotates in the same direction as the disk. Our ALMA observations therefore demonstrate that the inner cone walls, and the associated scattered light cavity, do not trace the interface with infalling material, which is shown to be confined to much wider angles (> 70°). The properties of the conical walls are suggestive of the interaction between an episodic inner jet or wind with an outer disk wind, or of a massive disk wind originating from 2 to 5 au. However, further modeling is required to establish their origin. In either case, such massive outflow may significantly affect the disk structure and evolution.

Mesostructured Hollow Siliceous Spheres for Adsorption of Dyes

AbstractA facile and one‐pot strategy for the preparation of novel diamino‐functionalized hollow siliceous spheres (DAF‐HSS) is suggested. Field‐emission scanning electron microscopy (FE‐SEM) images of DAF‐HSS showed a monodispersed hollow sphere morphology. Also, TEM images revealed that the DAF‐HSS has a porous structure with parallel semi‐long‐range channels. DAF‐HSS material was used as an adsorbent for the removal of hazardous monocationic dyes in aqueous solution. Neutral red (NR) and crystal violet (CV) were selected as model compounds. Isotherm and kinetic studies were carried out and their different linear forms were applied and compared. The equilibrium data fitted better with the Langmuir model.

Preparation of hollow SiC ceramic fibre from polycarbosilane fibre by diffusion-controlled cross-linking method

ABSTRACTCross-linking is favourable for increasing ceramic yield and avoiding melting or deformation of SiC ceramic precursor polycarbosilane (PCS) during pyrolysis. In order to achieve hollow SiC fibre, PCS fibre with a limited cross-linking depth was prepared by chlorinating the Si–H group in the outer layer of PCS fibre followed by hydrolysis and condensation of the formed Si–Cl group. The chlorination was implemented through a gas–solid reaction between Cl2 and PCS fibre. Based on the results of energy-dispersive spectrometer and attenuated total reflectance–Fourier transform infrared spectroscopy, the diffusion-controlled chlorination reaction was confirmed. During hydrolysis, the catalysis of ammonia gas was necessary. According to the results of dissolution and degradation experiments, cross-linked PCS outer layer formed after chlorination, hydrolysis and condensation, and the outer layer had higher ceramic yield than the core part. After pyrolysis, SiC fibre with hollow morphology was formed. By adjusting the chlorination degree, the morphology of resulting hollow SiC fibre could be modified.

Remarkable facets for selective monitoring of biomolecules by morphologically tailored CuO nanostructures

Remarkable selective analysis of biomolecules i.e., glucose and ascorbic acid on copper oxide facets was reported for the first time. The copper oxide nanostructures were synthesized using different Cu-ions sources i.e., CuCl2 and CuSO4 by utilizing the hydrothermal method, which congregates in flower and hollow sphere morphologies, respectively. Interestingly, the results showed a comparable sensitivity and selectivity of CuO nanostructures toward glucose and ascorbic acid. To provide a deep understanding of the key factors that predominate the efficiency and selectivity of nanostructured CuO toward these biomolecules, density functional theory (DFT) calculations were accomplished. Five different crystal facets including (002), (200), (202), (111), and (110) were considered and their binding energies with the biomolecules were investigated. It was found that the facets with rich Cu or O atoms might control the selectivity toward glucose and ascorbic acid. This approach will be helpful for designing sensitive and selective targeted nanomaterial-based sensors.

Electrochemical Performance of LiNixMnyCozO2 (NMC) Materials with Hollow Spheres Morphology

Electrochemical performance of the materials NMC333, NMC622 and NMC532 with hollow spheres morphology is evaluated both on a thin electrode and in a 3D arrangement in the battery module. Cyclic voltammetry of Li insertion provides charge capacities of 124, 154 and 142 mAh/g for thin electrodes containing NMC622, 532 and 333, respectively. NMC333 in the 3D battery arrangement provides 82.5% of the theoretical capacity after 5 formatting and 5 testing cycles at the C/20 and C/10 rates, respectively. NMC622 and NMC532 exhibit, under the same conditions, capacities of 64.0% and 64.6% of the theoretical battery capacity, respectively. The worse performance of the Ni-rich NMCs is ascribed to their higher reactivity with electrolyte during formatting.

Hollow Li2SiO3 architectures with tunable secondary nanostructures and their potential application for the removal of heavy metal ions

Li2SiO3 is a potential new material for mitigating environmental issues such as greenhouse effect and wastewater treatment, but the high-quality failure and evolvable morphology limit have restricted its large-scale application. Herein, a high-quality hierarchically hollow-structured Li2SiO3 assembled by tunable secondary structures was precisely fabricated by an efficient green and facile hydrothermal method. The secondary structures, from nanosheets to belts, thorns, spinule and eventually to nanoparticles, accompanying the corresponding morphologies evolving from peony-like to chrysanthemum-like, urchin-like, waxberry-like and eventually to spherical structures, could be tuned by adjusting precursors’ Li/Si molar ratios. All of the obtained hollow Li2SiO3 structures were attributed to a common growth mechanism called inside-out Ostwald ripening. The as-prepared hollow Li2SiO3 structures were experimented as heavy metal adsorbents for the first time and exhibited excellent adsorption performance for all employed heavy metal ions (Cu2+, Mn2+ and Ni2+). Furthermore, as a case study, the obtained heavy metal-bearing Li2SiO3 architectures (Cu(OH)2@Li2SiO3, MnO(OH)2@Li2SiO3 and Ni(OH)2@Li2SiO3) inherited the primary hollow morphology, which endowed them with reusability as high-efficient adsorbents for methylene blue by color removal efficiency higher than 98%. This work lays the foundation for the development of an environmentally friendly “two birds with one stone” route of “remover of heavy metal ions to dye adsorbent,” which will be of great significance for the wastewater treatment.

Platinum like cocatalysts tungsten carbide loaded hollow tubular g-C3N4 achieving effective space separation of carriers to degrade antibiotics

A novel P-doped hollow tubular g-C3N4/tungsten carbide (P-TCN/WC) photocatalyst was newly synthesized by a simple one-pot calcination process and used to degrade two typical antibiotics, tetracycline (TC) and ciprofloxacin (CIP) under visible light irradiation. The P-TCN/WC showed excellent photocatalytic activities toward degradation of antibiotics. The 8% P-TCN/WC showed the best photocatalytic activity, which could degrade 93.76% TC and 76.21% CIP within 120 min. The enhanced photocatalytic activity of P-TCN/WC was due to the expansion of light absorption and the reduction of carrier recombination. P doping and WC loading expanded light absorption of P-TCN/WC over the whole visible light spectrum. Meanwhile, the hollow tubular morphology boosted the utilization of light. Furthermore, the platinum like noble metal cocatalytic properties of WC loading and P doping made the recombination of carriers of P-TCN/WC decreased significantly no matter bulk or space. The intermediates of CIP were measured and the possible degradation pathway was tentatively proposed. The photocatalysts have high stability, superb light absorption, and prominent photocatalytic activity, which could be used as an effective method for antibiotics degradation.

Preparation of hollow SiC spheres with biological template and research on its wave absorption properties

In this work, SiO2 was evenly coated on dry yeast as biological template by sol-gel method, and the internal substances of yeast were removed at 700 °C to obtain hollow silicon template. Then, RF aerogel (carbon source) was used to wrap the silicon template. After carbonization treatment, carbon thermal reduction reaction was carried out at 1400 °C to obtain hollow SiC spheres (HSS). Under the coating of RF aerogel, the hollow SiO2 maintained its complete physical shape in the process of high-temperature synthesis, and the final product was hollow ellipsoidal silicon carbide with the maximum diameter of about 4.3 μm and the minimum diameter of about 3.5 μm, basically keeping the shape of yeast. The basic properties of the products were characterized by XRD, FT-IR, SEM, TEM and Tg, the absorption properties of the products were analyzed by VNA. The research found that the absorption performance of the hollow SiC with yeast morphology increased significantly in the frequency band of 2–18 GHz. When the thickness is 3.1 mm, the hollow SiC has the maximum reflection loss of −51.74 dB at 12.08 GHz. When the thickness is 4.0 mm, it has an effective absorption frequency width of 6.05 GHz, which has obvious advantages over SiC without special hollow morphology. The effect of hollow structure on the electromagnetic properties of SiC is discussed in detail.

ZIF-derived bifunctional Cu@Cu–N–C composite electrocatalysts towards efficient electroreduction of oxygen and carbon dioxide

A Cu@Cu–N–C composite electrocatalyst with metallic Cu NPs and Cu(II)-Nx species embedded into the carbon matrix was pyrolyzed from ZIF-8 precursor through the formation of Cu(OH)2@ZIF-8. The optimal Cu@Cu–N–C catalyst obtained at 1000 °C features a hollow polyhedral morphology, which is resulted from the carbothermal reaction of in-situ generated Cu2O and ZnO with carbon beyond 800 °C. The best-performance Cu@Cu–N–C exhibits an impressive catalytic bifunction towards oxygen reduction reaction (ORR) and carbon dioxide reduction (CO2RR) which is assumed to be imparted by the unique Cu(0)-Cu(II)-Nx active sites. In alkaline electrolyte, it shows the ORR performance (E1/2 = 0.83 V vs RHE) comparable to Pt/C (E1/2 = 0.85 V vs RHE), and the assembled zinc-air (Zn-air) battery displays an excellent durability with the open circuit voltage (1.23 V) decaying only by ca. 4.2% in 80 h at 20 mA cm−2. For CO2RR, it also delivers an outstanding catalytic performance converting CO2 into CO with a high Faradaic efficiency (90% at −0.5 V vs RHE). Control experiments have indicated that the potential synergistic interactions between Cu (0) (from Cu NPs) and Cu-Nx sites have promoting effects on both ORR and CO2RR.

Experimental investigation on improvement of latent heat and thermal conductivity of shape-stable phase-change materials using modified fly ash

Abstract Fly ash (FA) is the solid waste discharged from thermal power plants and has become one of the largest industrial solid wastes produced annually. Meanwhile, as energy shortages and environmental pollution caused by the excessive use of fossil energy becoming increasingly prominent, an improvement in energy efficiencies and the exploitation of clean renewable energies is urgently required. In this research, we proposed to modify FA by a simple alkali treatment. The modified fly ash (mFA) exhibited an optimized multistage three-dimensional hollow morphology with abundant granules and pores on the microsphere surface. The specific surface area of the FA was 2.68 m2/g, while it increased to 10.32 m2/g for mFA. Meanwhile, the Al2O3 content of mFA increased from 31.26 to 38.7 wt%, whereas the SiO2 content decreased from 57.43 to 44.89 wt%. After lauric acid (LA) impregnated into mFA, the shape-stable phase-change material (SSPCM) exhibited simultaneously enhanced latent heat and thermal conductivity. The latent heat and thermal conductivity of the obtained LA/mFA SSPCM was 65.7 J/g and 0.52 W/mK, which was 51.7% and 67.7% higher than that of LA/FA SSPCM, respectively. The latent heat enhancement was attributed to the larger specific surface area and the richer pore structure provided by the mFA. The significant thermal conductivity improvement was ascribed to the higher relative content of Al2O3 and the smaller thermal resistance of LA/mFA SSPCM. Moreover, the LA/mFA SSPCM exhibited robust thermal, chemical, and morphological stability with respect to 1000 times thermal cycling. Considering the suitable phase-change temperature, high energy storage density, enhanced thermal conductivity, robust thermal reliability, applicable thermoregulatory capacity, low cost and easy processing, and role of environmental governance, the mFA based SSPCM may have widespread application in solar-energy storage, building air-conditioning system and geothermal energy utilization.

MnOx fabrication with rational design of morphology for enhanced activity in NO oxidation and SO2 resistance

This paper synthesized MnOx based catalysts with rational design of morphology to investigate the improvement in NO oxidation and SO2 resistance. SEM and TEM characterizations illustrated the fabrication of hollow morphology and irregular rod-like morphology. Significant enhancement in NO oxidation by O2 was attained comparing with MnO2-C, especially at low temperature. Ce and Fe were selected as the second metal to modify H-MnO2 and MnO2-R catalysts. Notably, H-MnFeOx, equipped with rambutan-like morphology, further improved NO conversion, i.e., 89.8% at 220 °C (84.0% for H-MnO2). These catalysts with rational design of morphology displayed high BET surface area that was larger than 100 m2/g. For SO2 resistance, H-MnO2 exhibited the best 20 ppm SO2 tolerance and maintained its initial NO conversion within 360 min rather than deactivation immediately as MnO2-C. The Ce and Fe addition on MnO2-R moderately improved the SO2 resistance within the whole 480 min test. Overall, the hollow cavity structure of H-MnO2 could provide shuttle space for oxidation and improved mass adsorption and transformation, thereby attaining the better NO conversion and SO2 resistance. Finally, the mechanism for NO oxidation was proposed according to in-situ DRIFTS results.

Homogeneous nucleation of corundum nanocrystallites by rapid heating of aluminum formate hydroxide-based precursor powder

The high density nucleation of α-Al2O3 nanocrystallites was observed by rapid heating of the aluminum formate hydroxide-based precursor powder at 1200 °C for 50 s. The nucleation of α-Al2O3 nanocrystallites with less 10 nm in size from high purity aluminum oxide matrix has not been observed to our knowledge. Based on the results of XRD and TEM, α-Al2O3 nanocrystallites nucleated from the amorphous phase which formed after thermal decomposition of the precursor powder. Subsequently, α-Al2O3 with hollow rod-like morphology formed through coalescence and growth of nanocrystallites after heating at 1200 °C for 1 min. The results obtained in this paper indicates a possible beneficial effect of the rapid heating and cooling of the aluminum formate hydroxide-based precursor powder on the precipitation of α-Al2O3 nanocrystallites.

A low temperature solid state reaction to produce hollow MnxFe3-xO4 nanoparticles as anode for lithium-ion batteries

Hollow MnxFe3-xO4 nanoparticles (NPs) with an average size of 15 nm are produced from the solid state reaction of Fe3O4–Mn3O4 heterostructures. These heterostructures are synthesized through the seeded-growth of Mn3O4 crystal domains on the surface of hollow Fe3O4 NPs obtained by the nanoscale Kirkendall effect. Fe3O4–Mn3O4 heterostructures are subsequently annealed at 500 °C, enough temperature to promote the interfusion of Fe and Mn ions, but without compromising the hollow geometry. MnxFe3-xO4 nanostructures are tested as anode in lithium-ion batteries (LIBs), delivering large lithium storage capacities and high-rate capabilities of 1054 mAh g−1 at 0.1 A g−1 and 369 mAh g−1 at 5 A g−1. Additionally, hollow MnxFe3-xO4 NPs display long cycling stability, with a capacity up to 887 mAh g−1 at 0.3 A g−1 after 450 cycles. The excellent performance of hollow MnxFe3-xO4 NPs as anode for LIBs is associated with their crystal structure, composition, and the presence of carbonized ligands, which further promote electrical conductivity and buffer the volume changes during cycling. Additionally, the small particle size and hollow morphology improves the lithium kinetics, structural stability and cycling performance.

Preparation of Manganese Phthalocyanine Modified Nano-BiVO4 Photocatalyst with Perforated Hollow Morphology and Its Catalytic Performances

Nano-BiVO4 was successfully modified by manganese phthalocyanine (MnPc) with high photocatalytic activity through a simple hydrothermal path. The perforated hollow morphology of BiVO4 was maintained after the modification, which was profitable for the photocatalytic activity. The MnPc was physically combined with BiVO4 through weak links such as the Coulomb force or hydrogen bond, other than chemical bound. The band gap of the modified BiVO4 was successfully narrowed by MnPc to cause the redshift of the modified BiVO4, which provided larger visible light absorption. Therefore the MnPc-modified BiVO4 obtained improved photocatalystic activity. On the conditions of the hydrothermal temperature of 180 °C, pH of 7.5, hydrothermal time of 4 h, 3.30 mmol of EDTA, and the MnPc amount of 0.20 wt%, the band gap of the BiVO4 catalyst was narrowed to 2.40 eV. Under the catalysis of the MnPc-modified BiVO4, the discoloration rate of methylene blue reached 98.44% in the simulated sunlight. A synergistic effect between MnPc and BiVO4 appeared through our hydrothermal synthesis process. Such a successful modification design could be extended to other photocatalyst systems with phthalocyanine compounds and transition metal oxides.

Morphology-Controllable Hydrothermal Synthesis of Zirconia with the Assistance of a Rosin-Based Surfactant

With the assistance of a rosin-based surfactant, dehydroabietyltrimethyl ammonium bromine (DTAB), well-dispersed hollow cube-like zirconia particles were firstly synthesized by the hydrothermal treatment of ZrOCl2 aqueous solutions. The introduction of DTAB is crucial for improving the dispersion and regularity of the as-synthesized sample. After calcination, the crystal size of the calcined samples increased, and the edge angle of the cube-like particles became round accordingly. Finally, a hollow spherical morphology was formed for the sample calcined at 923 K. The as-synthesized sample showed big surface area of 146.78 m2/g and large pore volume of 0.23 cm3/g. With the increase of calcination temperature, the surface area and pore volume of the samples decreased significantly, and the pore size increased accordingly.