Double-shelled Hollow Research Articles

Architecting double-shelled hollow carbon nanocages embedded bimetallic sites as bifunctional oxygen electrocatalyst for zinc-air batteries

Rational design of complex hollow nanostructures offers a great opportunity to construct various functional nanostructures. A novel in situ disassembly-polymerization-pyrolysis approach was developed to synthesize atomically dispersed Fe single atoms (Fe SAs) and tiny Co nanoparticles (Co NPs) binary sites embedded in double-shelled hollow carbon nanocages (Co NPs/Fe SAs DSCNs) without removing excess templates. The Co NPs/Fe SAs DSCNs displayed excellent bifunctional activity, boosting the realistic rechargeable zinc-air batteries with high efficiency, long-term durability, and reversibility, which is comparable to noble metal catalysts (Pt/C and RuO2). The enhanced catalytic activity should be attributed to as well as the strong interactions between Fe SAs and Co NPs with the nitrogen-doped carbon matrix, the exposure of more active sites, and the high-flux mass transportation. In addition, the confinement effect between the double C-N shells prevented the aggregation and corrosion of metal atoms, thus improving the durability of the Co NPs/Fe SAs DSCNs, further highlighting the structural advantages of carbon nanoreactor. This work provides guidance for further rational design and preparation of complex hollow structure materials with advanced bifunctional air cathodes.

Thickness-controlled HsGDY/N-doped double-shell hollow carbon tubes for broadband high-performance microwave absorption

With the increasing deterioration of the electromagnetic environment, it is important to develop new and efficient electromagnetic wave-absorbing materials. In this work, bilayer hollow HsGDY/NC nanotubes with controllable thickness are constructed by introducing high conductivity polydopamine (PDA) and hydrogen-substituted graphdiyne (HsGDY) followed by the etching and carbonization. Subsequently, the effects of the composition, coating order, and structural characteristics of nanotubes on the electromagnetic parameters are thoroughly investigated, thereby analyzing the microwave absorption mechanism. The impedance matching of HsGDY/NC is optimized by changing the thickness of NC layer, while utilizing unique multi-heterogeneous interfaces and hierarchical conductive structures that enhance the interface polarization and conductive loss. As a result, HsGDY@NC-3 displays the optimal absorbing performance with an effective absorption bandwidth (EAB) of 7.8 GHz (10.1–17.9 GHz) and a minimum reflection loss (RLmin) of −47.18 dB at the filler content of only 11 %. This work broadens the application scopes of HsGDY and provides a novel insight into the design of lightweight, high-efficiency, and wide-frequency microwave absorbers, which is expected to be a potentially effective microwave-absorbing material.

“Two birds one stone” strategy to integrate electromagnetic wave absorption and self-anticorrosion in magnetic nanocomposites with double-shell hollow structure

Magnetic metal has broad application prospects in the field of electromagnetic wave (EMW) absorption due to its excellent dielectric and magnetic properties. However, high density and poor chemical stability constrain their development potential. The combination of magnetic metals with other lightweight carbon materials is an effective solution. In this work, magnetic nanoparticle fiber composites were prepared by electrostatic spinning and high-temperature annealing processes. By adjusting the preparation process and annealing temperature, Co/Co7Fe3/CF-800 fiber composites containing double-shell hollow structured nanocubes were cleverly synthesized. The material is mixed with paraffin wax and has a minimum reflection loss (RL) of –52.14 dB and a maximum effective absorption bandwidth (EAB) of 6.16 GHz at a load of 10 wt%. By analyzing the electromagnetic parameters of the material, it was demonstrated that the material absorbs EMW through the synergistic effect of dielectric and magnetic losses. Electrochemical testing in a simulated seawater environment demonstrated that the material also has a degree of self-anticorrosion capability. This work provides new strategies for designing materials with excellent electromagnetic wave absorption and self-anticorrosion properties.

Micro/Meso-Porous Double-Shell Hollow Carbon Spheres through Spatially Confined Pyrolysis for Supercapacitors and Zinc-Ion Capacitor.

Energy storage in supercapacitors and hybrid zinc ion capacitors (ZIC) using porous carbon materials offers a promising alternative method for clean energy solutions. The unique combination of hierarchical porous structure and nitrogen doping in these materials has demonstrated significant capacity for energy storage. Nevertheless, the full potential of these materials, particularly the relationship between pore structure configuration and performance, remains underexplored. Herein, a confined pyrolysis strategy based on the polymerization characteristics of polydopamine (PDA) was developed to construction of hollow carbon spheres with microporous/mesoporous dual shell structure. The depth of micropores and cavity can be controlled by adjusting the duration of heat treatment and hydrothermal treatment, in accordance with the decomposition and polymerization characteristics of PDA. Due to the elasticity of this structure, the relationship between the micro/mesoporous depth of the prepared carbon spheres and the energy storage performance in supercapacitors and ZIC is established. Through optimizing the ion transport capacity of carbon spheres and considering the influence of its internal cavity structure on energy storage, the resulting carbon spheres exhibit high specific capacitance of 389 F g-1 in supercapacitor and specific capacitance of 260 F g-1 and excellent stability with 99.3 % retention after 30000 chare/discharge cycles in ZIC.

Highly responsive double-shell ZnO hollow microspheres based gas sensor for acetic acid detection in vinegar

Acetic acid sensing materials for environmental and related food quality control requiring high sensitivity and selectivity, and ppb-level detection limit, remain challenging. Double-shell ZnO hollow microspheres were prepared by a surfactant assisted template method, and the resultant gas sensor showed excellent acetic acid sensing performance. The sensor response reached 116 to 100 ppm acetic acid at 270°C with a short response time of 3.2 s. The relationship between acetic acid concentration and the response was established, and the detection limit reached 100 ppb. DFT theory computational results demonstrated the highest adsorption energy of the ZnO gas sensor to acetic acid among all tested gases, proving its high selectivity to acetic acid. Besides, the unique double-shell hollow structure with abundant oxygen vacancy and large surface area might be the other factors that gave rise to its excellent acetic acid gas sensing performance. Based on the gas sensor, a method for fast quantitative detection of acetic acid content in vinegar was developed. The linear relationship between sensor response and acetic acid gas concentration of vaporized white vinegar was established, and the acetic acid content in the vinegar can be quickly determined. The result proved our acetic acid sensor to be a promising candidate for practical applications.

An origami microfluidic paper device based on core-shell Cu@Cu2S@N-doped carbon hollow nanocubes

BackgroudThe global prevalence of diabetes mellitus, a serious chronic disease with fatal consequences for millions annually, is of utmost concern. The development of efficient and simple devices for monitoring glucose levels is of utmost significance in managing diabetes. The advancement of nanotechnology has resulted in the indispensable utilization of advanced nanomaterials in high-performance glucose sensors. Modulating the morphology and intricate composition of transition metals represents a viable approach to exploit their structure/function correlation, thereby achieving optimal electrocatalytic performance of the synthesized catalysts. ResultsHerein, a sensitive and rapid Cu-encapsulated Cu2S@nitrogen-doped carbon (Cu@Cu2S@N–C) hollow nanocubes-functionalized microfluidic paper-based analytical device (μ-PAD) was fabricated. Through a delicate sacrificial template/interface technique and thermal decomposition, inter-connected hollow networks were formed to boost the active sites, and the carbon shell was coated to protect Cu from being oxidation. For application, the constructed μ-PAD is used for glucose sensing utilizing an origami automated sample pretreatment system enabled by a simple application of strong alkaline solution on wax paper. Under optimal circumstances, the Cu@Cu2S@N–C electrochemical biosensor exhibits broad detection range of 2–7500 μM (R2 = 0.996) with low detection limit of 0.16 μM (S/N = 3) and high sensitivity of 1996 μA mM−1 cm−2. Additionally, the constructed μ-PAD also exhibited excellent selectivity, stability, and reproducibility. SignificanceBy rationally designing the double-shell hollow nanostructure and introducing Cu-encapsulated inner layer, the synthesized Cu@Cu2S@N–C hollow nanocubes show large specific surface area, short diffusion channels, and high stability. The proposed origami μ-PAD has been successfully applied to serum samples without any additional sample preparation steps for glucose determination, offering a new perspective for early nonenzymatic glucose diagnosis.

Light-assisted ethanol dry reforming over NiZnOx hollow microspheres with enhanced activity and stability

Light-assisted thermocatalytic dry reforming of ethanol (EDR) utilizing the synergistic effect of photocatalysis and thermocatalysis is regarded as a promising route to convert greenhouse gas CO2 into value-added chemicals. In this work, double-shell NiZnOx hollow microspheres (NiZnOx-M) were synthesized as light-harvesting catalyst to enhance EDR performance under mild conditions. The characterization results of UV–vis–NIR and Photoluminescence Spectroscopy (PL) indicated that the band gap energy of NiZnOx-M catalyst was narrower because of the smaller Ni nanoparticles, thereby broadening its optical response range especially in visible light. The strong absorbance of light could greatly improve the activation of ethanol/CO2 and the gasification of carbon. With light irradiation, light could induce the transfer of photogenerated electron from semiconductor ZnO to active metal Ni, reducing the reaction energy barrier. Hence, NiZnOx-M catalyst showed superior photothermal catalytic activity along with good resistance capacity to coke accumulation and aggregation of active metal. Ethanol conversion was ca.2 times those obtained over NiZnOx-C prepared by conventional precipitation method. No obvious deactivation occurred after 100 h tests. This work provides some guidance for the design of high-performance photothermal catalyst to achieve the photo-thermal-chemical conversion of the greenhouse gases.

Ultra-stable Co3O4/NiCo2O4 double-shelled hollow nanocages as headspace solid-phase microextraction coating for enhanced capture of polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are persistent toxic pollutants that tend to accumulate in food and cause damage to human health. This work reports the ultra-sensitive detection of PCBs in beverage samples (green tea, honey, and bottled drinking water) by headspace solid-phase microextraction (HS-SPME) coupled with a gas chromatography-flame ionization detector (GC-FID). The Ultra-stable Co3O4/NiCo2O4 double-shelled hollow nanocages (DSHNC) as SPME fiber coating were synthesized with pyrolysis of zeolitic imidazolate framework-67/layered double hydroxide precursor. The fiber coating material Co3O4/NiCo2O4 DSHNC demonstrated excellent thermal stability (＞1000 °C) and long usage lifespan (≥160 times). The extract ability to polar PCBs was significantly enhanced by oxygen-containing groups, π-π stacking, and electrostatic interaction. Experiments results illustrated that the adsorption is controlled by chemical adsorption with a monolayer molecular adsorption. The HS-SPME-GC-FID method possessed good linearity (R2 ≥ 0.9961) in the linear range of 0.10–50000 pg·mL−1 and low detection limits (0.03–1.5 pg·mL−1). The enrichment factors were determined between 6884 and 9765. The method was successfully applied to enrich PCBs in real samples and obtained a good recovery rate in the range of 78.26–112.1 %.

Coupling effects of dielectric loss in N-doped carbon double-shelled hollow particles for high-performance microwave absorption

Microwave absorbing materials with lightweight and high-performance are of great significance for electronic technique, ecological environment and defense applications. The hollow structure of carbon microspheres is beneficial to achievement of high-performance microwave absorption due to high interfacial polarization. However, the key characteristic is still unclear to control interfacial polarization. Herein, double-shelled N-doped carbon hollow particles derived from polypyrrole by self-sacrifice template were synthesized. The polymerization process was controlled by the interface between solid and pyrrole acid liquid in Fe3O4 disperse system, subsequently, micro-nano structure of carbon was tuned. The N-doped carbon double-shelled hollow particles (DSHS) show a strong dielectric loss due to coupling effect of resistance loss and interfacial polarization owing to the double-shelled hollow structure. Thus, DSHS shows a high-performance microwave absorption with minimum reflection loss (RLmin) of −75.10 dB at a thickness of 2.48 mm and effective absorption bandwidth (RL ≤ -10 dB) of 6.08 GHz and 4.05 GHz covering the whole Ku band and almost the whole X with a thickness of 2.21 mm and 3.00 mm, respectively. This work provides a simple approach for synthesizing N-doped carbon particles with distinct micro-nano hierarchical structure, double-shelled hollow microspheres assembled by nanoparticles have potential application as a high-performance MAM.

Trapping of heavy metal ions from electroplating wastewater with phosphorylated double-shelled hollow spheres

The mesoporous multi-shelled hollow structures are promising for trapping of non-degradable heavy metal ions in wastewater but difficult to synthesize. We successfully demonstrated a simple strategy for the construction of mesopore windows on double-shelled α-Fe2O3 hollow spheres. A step-by-step proof of concept synthesis mechanism has been revealed by using mainly electron microscopy and thermogravimetric analysis. We proved that mesopore windows are indispensable to realize the complete surface coverage of phosphonate ligands on α-Fe2O3 double-shelled hollow spheres. The phosphonic groups inherently coordinated with Ni(II) and Cu(II) ions and formed complexes of high stability. Importantly, owing to the structural merits, the phosphorylated double-shelled hollow spheres selectively removes Ni(II) and Cu(II) at wider sample pH range with a high capacity of 380 mg g−1 and 410 mg g−1, respectively. In addition, no significant decrease in the removal efficiency was observed under high salt matrix. For electroplating industry wastewater, the novel structure performs simultaneous Ni(II) and Cu(II) removal, thus producing effluent of stable quality that meets local discharge regulations.

Self-oxidized amorphous FeOx@NiOy electrocatalyst with double-shell hollow nanoarchitecture for boosting oxygen evolution reaction

FeNi-based electrocatalysts are promising for oxygen evolution reaction (OER), but it is still challengeable to obtain unique nanoarchitecture with rich active sites and high OER activity. Herein, a novel self-oxidation strategy is proposed to convert FeNi hydrogels with core-shell structures into amorphous FeNi–O aerogels with double-shell (FeOx@NiOy) hollow nanoarchitecture by the Kirkendall effect. Attributed to the unique double-shell hollow nanoarchitecture, the FeNi–O aerogels own large specific surface area and porosity, which provides many more active sites for OER and facilitates ion diffusion and O2 release. Furthermore, the strong electron interactions occurring at the non-homogeneous interface of the double-shelled structure, can effectively accelerate the electron transfer thus boosting OER. In addition, the amorphous FeOx@NiOy double shell structure is benefit to maintain structural stability and prevent its corrosion by electrolyte. As a result, the FeNi–O aerogels deliver excellent OER activity with a low overpotential of only 280 mV at a high current density of 50 mA cm−2, a low Tafel slope of 32.5 mV dec−1, and good long-term catalytic stability. The work provides a facile, and low-cost strategy to develop hollow non-noble metal based electrocatalysts with boosted OER activity.

Construction of Ni/C composites with double-shell hollow porous structure toward high-efficiency microwave absorption

Designing structure at the nanoscale of materials has been proved to be an effective way to control electromagnetic parameters and optimize microwave absorption performance. For constructing lightweight microwave absorption materials, abundant studies focus on the preparation of absorbent with hollow, porous or yolk-shell structure. However, it is still a challenge to integrate multiple structures on one material by simple method. In this work, we found that the addition of citric acid in the preparation process played an extremely important role in regulating the structure of Ni-MOF, and developed one-step approach to synthesis double-shell hollow porous Ni-MOF. After the carbonization process, the Ni/C composite was obtained. The controllable morphology of Ni-MOF endowed Ni/C composite adjustable absorbing properties. Under the assistance of citric acid, the Ni/C composite with yolk-shell, porous, as well as double-shell hollow porous structure was also synthesized. The optimal reflection loss was −56.18 dB, the broadest bandwidth was 6.1 GHz at 2.2 mm for double-shell hollow porous Ni/C composite. Particularly, strong reflection loss at C band, X band, and Ku band was realized by regulating the structure of Ni/C composite. This work revealed the mechanism of microstructures regulating the absorbing properties, which could be beneficial to the further development of MOFs derived absorbent.

Supercapacitor performance of MOF-derived double-shell hollow Ni-Fe-Mn-Se nanocubes

In this study, Ni-Fe-Mn-Se nano boxes with a double-layer hollow structure were synthesized by a static self-assembly and hydrothermal method. To generate a stable structure, NiFe Prussian blue analogue (NiFe-PBA) was used as the substrate material. Moreover, a layer of polydopamine (PDA) was applied onto the surface of the PBA as a “connecting link” to protect the PBA core from collapsing internally and anchor metal ions, enabling the external in-situ growth of NiMn-LDH. A comparison was made between the morphology and properties of nano boxes that were etched using varying concentrations of selenium acid. It was observed that the combination of multi-metallic elements with Se effectively modified the electronic structure of the material, improving its electrical conductivity. The synthesized electrode material, Ni-Fe-Mn-Se, exhibited a high specific capacitance of 1433 F g−1 at 1 A g−1. Moreover, an asymmetric supercapacitor made of a Ni-Fe-Mn-Se cathode, Ni-Fe-Mn-Se//AC, demonstrated outstanding cycling stability (85 % capacitance retention after 8000 cycles) and a maximum energy density of 66.8 Wh kg−1 at a power density of 791 W kg−1. Thus, the electrode material synthesized in this study, Ni-Fe-Mn-Se, exhibits great promise for use in energy storage applications.

Hierarchical Cube-in-Cube Cobalt-Molybdenum Phosphide Hollow Nanoboxes Derived from the MOF Template Strategy for High-Performance Supercapacitors.

The design of hierarchical hollow nanostructures with complex shell architectures is an attractive and effective way to obtain a desirable electrode material for energy storage application. Herein, we report an effective metal-organic framework (MOF) template-engaged method to synthesize novel double-shelled hollow nanoboxes, in terms of chemical composition and structure complexity, for supercapacitor application. Starting from cobalt-based zeolitic imidazolate framework (ZIF-67(Co)) nanoboxes as the removal template, we developed a rational preparation approach to synthesize cobalt-molybdenum-phosphide (CoMoP) double-shelled hollow nanoboxes (donated as CoMoP-DSHNBs) through (i) ion-exchange reaction, (ii) template etching, and (iii) phosphorization treatment, respectively. Notably, despite the previously reported works, the phosphorization was simply done using the facile solvothermal method, without employing annealing and high-temperature conditions, which can be considered as one of the merits of the current work. CoMoP-DSHNBs showed excellent electrochemical properties owing to their unique morphology, high surface area, and optimal elemental composition. In a three-electrode system, the target material showed a superior specific capacity of 1204 F g-1 at 1 A g-1 with a remarkable cycle stability of 87% after 20000 cycles. The hybrid device formed of activated carbon (AC) as the negative electrode and CoMoP-DSHNBs as the positive electrode exhibited a high specific energy density of 49.99 W h kg-1 and a maximum power density of 7539.41 W kg-1 with a great cycling stability of 84.5% after 20,000 cycles.

Design of double-shelled NiS-FeS@NC hollow nanocubes for high-performance sodium-ion batteries

Mixed metal sulfides (MMSs) are highly noticeable as prospective materials for sodium storage due to their prominent electrochemical reversibility and excellent redox activity. Nevertheless, the fast capacity decay and poor rate capability hinder their application in sodium-ion batteries (SIBs). In this work, a facile template method, using Prussian blue analogue as the precursor, was employed to fabricate the double-shelled hollow structure with nitrogen (N)-doped carbon layer coated on the outer shell of NiS-FeS hollow nanocubes (NiS-FeS@NC). Specifically, the NiS-FeS@NC composite provides a glorious reversible capacity (395.8 mAh g−1 after 200 cycles at 1.0 A g−1) and superior rate capability (322.2 mAh g−1 at 5.0 A g−1) when employed as electrode material for SIBs. In addition, the designed NiS-FeS@NC= |Na3V2(PO4)2 @C full battery can maintain an excellent reversible capacity (68.7 mAh g−1 after 200 cycles at 1.0 A g−1) as well as robust cycling stability. The improvement of the sodium storage performance can be mainly attributed to the synergistic coupling of the N-doped carbon coating layer and the hollow nanostructure, which can effectively maintain the integrity of the nanocube structure and accelerate the transportation of electrons/ions, thus contributing to improving the electrochemical sodium storage performance. Importantly, the unique modification strategy reported in this paper, combining with the mechanism and kinetics revealing, is expected to provide insights for facilitating high-performance electrodes for SIBs.

Novel Co3O4@TiO2@CdS@Au double-shelled nanocage for high-efficient photocatalysis removal of U(VI): Roles of spatial charges separation and photothermal effect

Effective spatial separation and utilization of photogenerated charges are critical for photocatalysis process. Herein, novel Co3O4 @TiO2 @CdS@Au double-shelled nanocage (CTCA) with spatially separated redox centers was synthesized by loading Co3O4 and Au NP cocatalysts on the inner and outer surfaces of Z-scheme heterojunction (TiO2 @CdS). The reduction rate constant of U(VI) by CTCA reached 0.218 min−1 under simulated sunlight irradiation, which was 6.6, 3.2 and 36.3 times than that of monolayer CTCA (0.033 min−1), CTC (0.068 min−1) and CT (0.006 min−1). The full-spectrum light-assisted photothermal catalytic performance can enable CTCA to remove 98.8% of U(VI) and degrade nearly 90% of five organic pollutants simultaneously. Detailed characterizations and theory calculations revealed that the photogenerated holes and electrons in CTCA flow inward and outward. More importantly, Co3O4 acts as a “nano heater” to generate the photothermal effect for further enhancing the charge transfer and accelerating the surface reaction kinetics. Meanwhile, the photogenerated electrons and superoxide radicals play a dominant role in reducing the adsorbed U(VI) to insoluble (UO2)O2·2H2O(s). This work provides valuable input toward a novel double-shelled hollow nanocage reactor with excellent photothermal catalysis ability for efficient recovery U(VI) from uranium mine wastewater to address environmental contamination issues.

Direct Z-Scheme Polymer/Polymer Double-Shell Hollow Nanostructures for Efficient NADH Regeneration and Biocatalytic Artificial Photosynthesis under Visible Light

The design of a highly efficient polymer photocatalyst is an essential prerequisite for photo-biocatalysis in a polymer–enzyme coupled system, which offers an important platform for the synthesis of pharmaceuticals and fine chemicals. However, current polymers still suffer drawbacks of poor water wettability, low visible light absorption, and high recombination rate of photoinduced electron/hole pairs, which severely limit their application in photo-biocatalysis. Herein, we demonstrate a polymer/polymer double-shell hollow nanostructure (PCN@PDBTS-HN) via a facile two-step polymerization with polymeric carbon nitride (PCN) and poly-dibenzothiophene sulfone (PDBTS) as internal and external shells, respectively. The covalent connection of those two polymer layers ensures the spontaneous electron transfer from PDBTS to PCN, as reflected in X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and fluorescence spectra, which could effectively accelerate the charge separation and migration. Thanks to its improved light-harvesting, increased hydrophilicity, and enhanced redox capacity, the obtained PCN@PDBTS-HN demonstrates an excellent catalytic efficiency in visible-light-promoted NADH regeneration with a conversion of 85.4% being achieved in 40 min (turnover frequency of 0.859 mmol g–1 h–1). This value is 1.4 and 2.6 times higher than that of pristine PCN and PDBTS, respectively, indicating an essential role of Z-scheme heterojunction in improving the catalytic efficiency. In addition, PCN@PDBTS-HN also displays excellent photocatalytic selectivity for 1,4-NADH regeneration, remarkable photostability, and good biocompatibility. A total amount of 2.12 mM methanol and 8.39 mM l-glutamate was accumulated in the polymer/alcohol dehydrogenase (YADH) and polymer/glutamate dehydrogenase (GDH) coupled system, respectively, implying high flexibility of fine chemical production via the photo-biocatalytic approach.

Template-free formation of BiOCl double-shelled hollow microspheres with enhanced carbamazepine removal efficiency

Constructing three-dimensional (3D) hierarchical structure is regarded as an effective strategy to alleviate the inherent drawbacks of the BiOCl bulk structure and realize the optimization of photocatalytic performance. Herein, a unique BiOCl double-shelled hollow microsphere structure with adjustable shell thickness is fabricated through a template-free one-pot solvothermal method for the first time. A plausible formation mechanism is proposed by exploring the morphological changes during the growth process. The as-obtained hollow microspheres photocatalyst exhibits excellent carbamazepine (CBZ) degradation efficiency (97.5%) under simulated solar irradiation, the corresponding apparent rate constant is about 4 times and 3 times than that of conventional BiOCl solid microspheres. The experimental and characterization results show that the existence of nanosheet subunits and porous structures shorten the diffusion length of charge carriers, which is conducive to the separation and transfer of photogenerated. Meanwhile, the construction of double-shelled hollow structure achieves higher light utilization. This work demonstrates the superior performance of catalysts with hierarchical hollow structures for pollutant degradation and provides new ideas to further optimize the photocatalytic performance of BiOCl-based materials.

Highly efficient synthesis of CeO2@g-C3N4 double-shelled hollow spheres for ultrasensitive self-enhanced electrochemiluminescence biosensors

In this work, CeO2@g-C3N4 double-shelled hollow spheres were skillfully synthesized as a novel type self-enhanced electrochemiluminescent (ECL) emitter by a highly efficient outside-in hard template method. Thanks to its great catalytic ability, CeO2 were served as a co-reaction accelerator for improving ECL performance of the hollow g-C3N4 spheres (HCNSs)/S2O82− system. In addition, the self-enhanced ECL emitter is designed as a complex containing a co-reaction accelerator and a luminophore to shorten the electron transfer path, which decreases the energy loss of the luminophore significantly. More importantly, the unique double-shelled hollow structure not only greatly decreases the inner filtering effect, but also maximizes the utilization efficiency of the ECL luminophores by increasing a CeO2 shell inside the HCNSs as co-reaction accelerator, effectively enhancing the ECL intensity. Under the optimal conditions, the designed ECL immunosensor showed excellent performance in the determination of CA19-9 with a linear range of 0.50 mU mL−1 –500.00 U mL−1 and a low detection limit of 0.039 mU mL−1. Importantly, the resulting biosensor has good stability, high sensitivity and reliable reproducibility, suggesting its potential application in clinical research.

Engineering tandem double p-n heterostructured CeO2@CdS-Cu8S5 hollow spheres for remarkable photocatalytic CO2 reduction

Carbon cycling and value-added CO2 utilization through photocatalytic CO2 reduction are effective strategies for solving environmental problems and energy crises. Here, we rationally design and fabricate a double p-n heterostructured CeO2@CdS-Cu8S5 double-shelled hollow sphere (DSHSs) photocatalyst, which efficiently and stably performs photocatalytic CO2 reduction under visible light irradiation. Firstly, CeO2 hollow spheres were prepared by the template-assisted method. Then ultrathin CdS nanolayers were grown in situ by the chemical bath deposition method. Finally, part of the CdS was converted to Cu8S5 by cation exchange, resulting in the CeO2@CdS-Cu8S5 hybrid with uniform interfacial contact and ultrathin double-shelled hollow spherical structure. The constructed tandem double p-n heterostructure contributes to the excellent photo-induced charge separation and migration capability of the CeO2@CdS-Cu8S5 photocatalyst. Thanks to the multiple light scattering inside the double-shelled hollow structure, solar radiation can be absorbed more efficiently. In addition, the abundant exposed active sites also significantly contribute to the chemisorption of CO2 molecules and the progress of surface redox reactions. Based on the above properties, the optimized CeO2@CdS-Cu8S5 DSHSs without any noble metal cocatalyst exhibited excellent activity (18.25 µmol g–1h−1) and high selectivity (89.3%) during the photocatalytic reduction of CO2 deoxygenation to CH4.