Hollow Carbon Spheres Research Articles

A nitrogen-doped hollow carbon nanospheres-based aptasensor for non-invasive salivary detection of progesterone

Developing an easy-to-use and non-invasive sensor for monitoring progesterone (P4) as a multi-functional hormone is highly demanded for point-of-care testing. In this study, an ultrasensitive electrochemical aptasensor is fabricated for monitoring P4 in human biofluids. The sensing interface was designed based on the porous nitrogen-doped hollow carbon spheres (N-HCSs). The N-HCSs covalently immobilized high-dense aptamer (Apt) sequences as the bioreceptor of P4. The electron transfer of the redox probe was hindered by incubating P4 on the aptasensor surface and forming the P4-Apt complexes. Meanwhile, the signaling was decreased under two wide linear dynamic ranges (LDRs) from 10 fM to 5.6 μM with a limit of detection (LOD) value of 3.33 fM. The aptasensor presented satisfactory selectivity in the presence of different off-target species with successful feasibility for P4 detection in some human urine and saliva samples. The aptasensor with high sensitivity, as an advantage for on-site and sensitive measurement of P4, can be considered a non-invasive tool for routine analysis of real-world clinical samples method.

A new strategy for preparing high oil content PAO40@HMCs microcapsules for improving tribological properties of PA6 composites

Enhancing the tribological characteristics of polyamide 6 (PA6) represents an effective strategy for extending the service life of self-lubricating PA6 composites. In this investigation, hollow mesoporous carbon spheres (HMCs) with an average diameter of 10 μm were synthesized using the template method, and the crucial factors influencing HMCs preparation were thoroughly examined. Successful synthesis of polyalphaolefin oil-containing microcapsules (PAO40@HMCs) was achieved, utilizing HMCs as microcontainers and PAO40 lubricant as the core material. The self-lubricating PAO40@HMCs microcapsules exhibited a notable oil content of 76.0 wt%. The tribological properties of the prepared self-lubricating PA6 composites were significantly better than those of pure PA6. When the content of PAO40@HMCs microcapsules in the composite reached 7 wt%, the coefficient of friction (COF) for the PA6 composite decreased by 87.9% (from 0.420 to 0.051), and the wear loss was reduced by 80% (from 0.115 to 0.023 g/0.5h). Through an analysis of the morphology and transfer film of the wear surface and friction pair, it was evident that microcapsules played a pivotal role in enhancing the self-lubricating properties of PA6 composites.

Designing hollow mesoporous carbon sphere for high-rate supercapacitor in water-in-salt electrolyte

The expansion of the operational voltage in supercapacitors (SCs) through the utilization of water-in-salt electrolytes (WISEs) has garnered considerable attention for achieving elevated energy density. However, the poor rate performance of assembled SCs persists due to the heightened viscosity of WISEs (e.g., 17.0 mol kg−1 NaClO4), so designing the porous structure of electrode materials to improve the rate performance of SC in WISEs has become a research focus. In this study, we present a straightforward approach to fabricate hierarchical porous carbon spheres, designing to expedite ion infilling and transport within WISE-based SCs. The hollow porous carbon is synthesized via one-step pyrolysis process, wherein the decomposition of inner colloid particles yields gases, while the outer resorcinol–formaldehyde resin carbonizes to form a spherical shell. In the WISE of 17.0 mol kg−1 NaClO4, the resulting symmetric SCs exhibit an operational voltage of 2.6 V and significantly improved rate capability with a capacitance retention of 47.7 % at 100 A g−1. Notably, the energy density can reach 31.0 Wh kg−1 at a power density of 2.4 kW kg−1. Even under high power density conditions of 120.0 kW kg−1, the energy density of 14.7 Wh kg−1 can remain. Additionally, the SC device manifests an impressive capacitance retention of 99.1 % after 20,000 cycles, showcasing exceptional cyclic stability. This research introduces a novel synthesis strategy for hierarchical porous carbon materials, enabling the development of high-rate SCs with both elevated energy density and power density.

Constructing the unique structure with Co9S8 embedded in mesoporous carbon hollow sphere for high-performance anode materials of lithium-ion batteries

Constructing the unique structure with Co9S8 embedded in mesoporous carbon hollow sphere for high-performance anode materials of lithium-ion batteries

Spatial Confinement of Sn/TiO2 Nanoparticles in Hollow Mesoporous Carbon Spheres Opal for Stable Zn Metal Anodes

AbstractThe sluggish Zn2+ diffusion and high nucleation energy barrier induce uncontrolled growth of Zn dendrites and detrimental parasitic reactions, severely hampering the commercialization of Zn metal anodes (ZMAs). Herein, hollow mesoporous carbon sphere opal with confined Sn/TiO2 clusters (HMCSST) is designed as the host to spatially regulate the Zn deposition. Owing to the capillary effect of the ordered hierarchical porous structure, the mass diffusion can be dramatically accelerated to promote a fast deposition kinetics at the interface between ZMA and electrolyte. Besides, the encapsulated ultrafine Sn/TiO2 clusters serve as zincophilic sites to achieve both the uniform Zn deposition on the hierarchical porous opal host and the high thermodynamic stability of ZMAs. Benefiting from the structural and componential merits, the HMCSST host effectively reduces the activation energy to enable a temporal‐spatial ordering of Zn nucleation and growth. As expected, the stable HMCSST‐Zn electrode guarantees steady Zn platting/stripping with long‐term stability over 1300 h in a symmetrical cell at a depth of discharge of 37.5%. As a proof‐of‐concept demonstration, an HMCSST‐Zn||ammonium vanadate full cell shows a long lifespan over 5000 cycles at 10.0 A g−1 with low polarization.

Cobalt/Nitrogen-Doped carbon hollow spheres for highly efficient degradation of tinidazole with peroxymonosulfate

This study aimed to put forward a strategy to synthesize cobalt/N-Doped carbon hollow spheres (Co/NCHPs) with ample reactive sites. The zeolitic imidazolate framework-67 was loaded on the polystyrene nanosphere (PS@ZIF-67) as precursors, followed by a controlled pyrolysis to obtain Co/NCHPs with a large single hole on each sphere. The 1O2, SO4•−, O2•−, and •OH were identified as the main reactive oxygen species (ROSs) by electron paramagnetic resonance (EPR) experiments. It is also worth noting that electron transfer was also the main non-radical pathway for tinidazole (TNZ) degradation in Co/NCHPs/PMS systems. The effects of reaction conditions on TNZ degradation were investigated. 20 mg/L of TNZ was degraded within 6 min under UV–visible light irradiation. Besides, the degradation efficiency of four organic pollutants was higher than 95 % in different water matrices. Moreover, Co/NCHPs exhibited an exceptional photocatalytic performance for several antibiotics and organic dyes mixed solution in natural water. Furthermore, the recycling test of Co/NCHPs indicated that catalysts can be reused five times without obvious activity loss. This work provided a facile and large-scale preparation method to obtain Co/NCHPs.

Photoelectrothermocatalytic reduction of CO2 to glycol via CdIn2S4-N/C hollow heterostructure mimicking plant cell

A series of novel semiconductor composites of CdIn2S4-N/C, in which CdIn2S4 is grown on hollow nitrogen-doped carbon spheres to mimic plant cells, were designed and applied to photoelectrothermocatalytic reduction of CO2. Our results reveal that the unique hollow structure and photothermal properties of N/C contribute to excellent performance of catalyst in CO2 reduction. Specifically, the optimal catalyst of CdIn2S4-N/C-2–800 demonstrates an outstanding catalytic activity with a formation rate of 168.5 µM h−1 cm−2 for carbon-based products and an electron selectivity for C2 products of 66.9 %. DFT calculations demonstrate that pyridine N and pyrrole N can reduce the energy barrier during CO2 reduction. Two important species of *=C=O and OC-COH* were detected by operando IR spectra and suggested to be key intermediates to C2 products via a carbene (*=C=O) coupling mechanism. CdIn2S4-N/C provides thermoelectrons and active sites like in the membrane of plant to enhance the probability of C-C coupling.

Nitrogen-oxygen co-doped carbon@silica hollow spheres as encapsulated Pd nanoreactors for acetylene dialkoxycarbonylation

The introduction of heteroatoms into hollow carbon spheres is imperative for enhancing catalytic activity. Consequently, we investigated the utilization of nitrogen–oxygen(N/O) co-doped hollow carbon (C)/silica (SiO2) nanospheres (NxC@mSiO2), which have a large internal volume and a nano-constrained environment that limits metal aggregation and loss, making them a potential candidate. In this study, we demonstrate the synthesis of nitrogen–oxygen (N/O) co-doped hollow carbon spheres using resorcinol and formaldehyde as carbon precursors, covered with silica, and encapsulated with palladium nanoparticles (NPs) in situ. The N/O co-doping process introduced defects on the surface of the internal C structure, which acted as active sites and facilitated substrate adsorption. Subsequent treatment with hydrogen peroxide (H2O2) introduced numerous carboxyl groups onto the C structure, increasing the catalytic environment as acid auxiliaries. The carboxyl group is present in the carbon structure, as determined calculations based on by density functional theory, reduces the adsorption energy of acetylene, thereby promoting its adsorption and enrichment. Furthermore, H2O2-treatment enhanced the oxygen defects in the carbon structure, improving the dispersion of Pd NPs and defect structure. The Pd/NxC@mSiO2-H2O2 catalysts demonstrated outstanding performance in the acetylene dialkoxycarbonylation reaction, showcasing high selectivity towards 1,4-dicarboxylate (>93 %) and remarkable acetylene conversion (>92 %). Notably, the catalyst exhibited exceptional selectivity and durability throughout the reaction.

Efficient PMS activation toward degradation of bisphenol A by metal-free nitrogen-doped hollow carbon spheres

Peroxymonosulfate (PMS) activation methods conventionally face challenges such as high energy consumption and the risk of metal leaching, limiting their practical application. Metal-free catalysts often face the problem of low catalytic activity. This study designed an in-situ nitrogen-doped hollow carbon catalyst (DNC-9), which offers balances efficient catalytic performance and metal-free catalysis. The results indicate that the DNC-9/PMS system effectively degrades bisphenol A, achieving complete degradation over a broad pH range (3.0–9.0). Through structure modification, the degradation efficiency of bisphenol A compared with SiO2@DNC-9/PMS system was improved by around 6 times and the degradation kinetic rate can reach 0.346 min−1. DNC-9 can activate PMS, resulting in a higher concentration of singlet oxygen without the generation of free radicals. Graphitic nitrogen in DNC-9 plays a crucial role in this activation, offering adsorption sites that facilitate decomposition of PMS and generating 1O2. In addition, graphitic nitrogen forms a transient active intermediate, DNC-9-PMS*, enhancing bisphenol A degradation. The catalyst recovers its high activity to complete bisphenol A removal with 15 min after thermal regeneration in cyclic experiments, demonstrating its potential as a practical solution for the efficient degradation of emerging contaminants.

Nitrogen-doped hollow carbon spheres decorated with NiCo alloy nanoparticles for high-performance supercapacitor electrode

Nitrogen-doped hollow carbon spheres (NHCSs) decorated with NiCo alloy nanoparticles (NPs) were prepared and examined for their prospective role as high-performance electrode materials. The NHCSs were synthesized through a silica-assisted synthesis method, followed by the decoration of NiCo alloy NPs onto the NHCSs using a simple wet impregnation method, employing a 1:1 M ratio of Co to Ni elements. The NiCo/NHCS-23, composed of NHCSs with 23 wt% of NiCo alloy NPs, exhibited a specific capacitance (Csp) of 536 F g−1 when tested in a 6 M KOH solution at a current density of 1 A g−1. This high Csp is attributed to the synergistic effect of the faradaic charge storage provided by NiCo alloy NPs and the N-doped hollow carbon structure. The N content of the NHCSs and NiCo/NHCS-23 was found to be 1.9 % and 2.2 %, respectively. Symmetric supercapacitor (SSC) devices were assembled using two NiCo/NHCS-23 electrodes and a 0.5 M tetraethylammonium tetrafluoroborate/propylene carbonate electrolyte. The resulting SSC device operated within a potential window of 3.5 V and exhibited an energy density of 16.1 Wh kg−1 at the power density of 250 W kg−1. The SSC device demonstrated impressive cycling stability, maintaining 90.0 % capacitance and 83.1 % Coulombic efficiency after 5000 cycles. These results suggest that NiCo/NHCS nanocomposites have significant potential for utilization in high-energy storage applications.

Cobalt hydroxide decorating N-doped hollow carbon sphere as a new sulfur host to improve long cycle stability in lithium–sulfur batteries

Cobalt hydroxide decorating N-doped hollow carbon sphere as a new sulfur host to improve long cycle stability in lithium–sulfur batteries

Hyphae‐mediated bioassembly of carbon fibers derivatives for advanced battery energy storage

AbstractIngenious design and fabrication of advanced carbon‐based sulfur cathodes are extremely important to the development of high‐energy lithium‐sulfur batteries, which hold promise as the next‐generation power source. Herein, for the first time, we report a novel versatile hyphae‐mediated biological assembly technology to achieve scale production of hyphae carbon fibers (HCFs) derivatives, in which different components including carbon, metal compounds, and semiconductors can be homogeneously assembled with HCFs to form composite networks. The mechanism of biological adsorption assembly is also proposed. As a representative, reduced graphene oxides (rGOs) decorated with hollow carbon spheres (HCSs) successfully co‐assemble with HCFs to form HCSs@rGOs/HCFs hosts for sulfur cathodes. In this unique architecture, not only large accommodation space for sulfur but also restrained volume expansion and fast charge transport paths are realized. Meanwhile, multiscale physical barriers plus chemisorption sites are simultaneously established to anchor soluble lithium polysulfides. Accordingly, the designed HCSs@rGOs/HCFs‐S cathodes deliver a high capacity (1189 mA h g−1 at 0.1 C) and good high‐rate capability (686 mA h g−1 at 5 C). Our work provides a new approach for the preparation of high‐performance carbon‐based electrodes for energy storage devices.

Mesoporous carbon spheres with programmable interiors as efficient nanoreactors for H2O2 electrosynthesis

The nanoreactor holds great promise as it emulates the natural processes of living organisms to facilitate chemical reactions, offering immense potential in catalytic energy conversion owing to its unique structural functionality. Here, we propose the utilization of precisely engineered carbon spheres as building blocks, integrating micromechanics and controllable synthesis to explore their catalytic functionalities in two-electron oxygen reduction reactions. After conducting rigorous experiments and simulations, we present compelling evidence for the enhanced mass transfer and microenvironment modulation effects offered by these mesoporous hollow carbon spheres, particularly when possessing a suitably sized hollow architecture. Impressively, the pivotal achievement lies in the successful screening of a potent, selective, and durable two-electron oxygen reduction reaction catalyst for the direct synthesis of medical-grade hydrogen peroxide disinfectant. Serving as an exemplary demonstration of nanoreactor engineering in catalyst screening, this work highlights the immense potential of various well-designed carbon-based nanoreactors in extensive applications.

Support engineering modulated Pt/hierarchical MoSe2@mesoporous hollow carbon spheres for efficient methanol-assisted water splitting

Hydrogen generation from methanol via methanol-assisted water splitting is a promising electrochemical energy conversion technology but still meets challenges in addressing the low intrinsic activity and easy poisoning problems of the conventional Pt catalysts. Herein, the support engineering modulated Pt by hierarchical MoSe2@mesoporous hollow carbon support was proposed to integrate some structural and catalytic advantages for hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). Supporting engineering by layered MoSe2 nanosheets confined in mesoporous hollow carbon spheres (MHCSs) is adopted to uniformly anchor Pt nanoparticles (Pt/MoSe2@MHCS), which effectively enhances the conductivity and prevents the layer-by-layer stacking of MoSe2; Strong interaction and coupling ability between Pt and MoSe2 and the resultant electronic structure regulation of the active centers could weaken the binding strength of CO* and H* intermediates during catalysis and strengthen the oxophilicity leading to improved MOR and HER kinetics. Specifically, Pt/MoSe2@MHCS shows a significantly improved MOR current density of 81.1 mA cm−2, about 3.0 times that of the benchmark Pt/C catalyst. Meanwhile, it also exhibits the HER performance of 28 mV to achieve a kinetic current density of 10 mA cm−2 in methanol-contained electrolytes. When employed for overall methanol electrolysis, a lowered input voltage of 1.11 V can be obtained to drive the current density (10 mA cm−2) compared to that for water electrolysis (0.62 V vs. 1.73 V). The electrochemical properties of high activity, rapid catalytic kinetics, and good stability were also demonstrated due to the enhanced oxophilicity and high poisoning tolerance ability resulting from the MoSe2/carbon substrate-induced electron redistribution of Pt sites. This work reports a novel platform to address the catalysis challenges in hydrogen production via the methanol electrolysis technique.

A Versatile Nanozyme-Based NADH Circulating Oxidation Reactor for Tumor Therapy through Triple Cellular Metabolism Disruption.

Nanozyme-based metabolic regulation triggered by tumor-specific endogenous stimuli has emerged as a promising therapeutic strategy for tumors. The current efficacy, however, is constrained by the limited concentration of endogenous substrates and the metabolic plasticity of tumors. Consequently, the implementation of efficient metabolic regulation in tumor therapy is urgently needed. Herein, a versatile nanozyme-based nicotinamide adenine dinucleotide (NADH) circulating oxidation nanoreactor is reported. First, the synthesized cobalt-doped hollow carbon spheres (Co-HCS) possess NADH oxidase (NOX)-mimicking activity for the NADH oxidation to disrupt oxidative phosphorylation (OXPHOS) pathway of tumor cells. Second, the substrate-cycle manner of Co-HCS can be used for NADH circulating oxidation to overcome the limitation of substrate deficiency. Finally, 2-Deoxy-D-glucose (2-DG) and 6-aminonicotinamide (6-AN) are introduced to block glycolysis and pentose phosphate pathway (PPP), thus creating a versatile nanozyme-based NADH circulating oxidation nanoreactor (Co-HCS/D/A) for tumor therapy through triple cellular metabolism disruption. In vitro and in vivo results demonstrate that the designed nanoreactor not only enhances the catalytic efficiency but also disrupts the tumor metabolic homeostasis, leading to efficient therapy outcome. This study develops a novel NADH circulating oxidation nanoreactor for tumor therapy through triple cellular metabolism disruption, which addresses the limitations of current nanozyme-based metabolism regulation for tumor therapy.

P-bridged Fe-X-Co coupled sites in hollow carbon spheres for efficient hydrogen generation

Non-precious metals have shown attractive catalytic prospects in hydrogen production from ammonia borane hydrolysis. However, the sluggish reaction kinetics in the hydrolysis process remains a challenge. Herein, P-bridged Fe-X-Co coupled sites in hollow carbon spheres (Fe-CoP@C) has been synthesized through in situ template solvothermal and subsequent surface-phosphorization. Benefiting from the optimized electronic structure induced by Fe doping to enhance the specific activity of Co sites, bimetallic synergy and hollow structure, the as-prepared Fe-CoP@C exhibits superior performances with a turnover frequency (TOF) of 183.5 min−1, and stability of over 5 cycles for ammonia borane hydrolysis, comparable to noble metal catalysts. Theoretical calculations reveal that the P-bridged Fe-X-Co coupled sites on the Fe-CoP@C catalyst surfaces is beneficial to adsorb reactant molecules and reduce their reaction barrier. This strategy of constructing hollow P-bridged bimetallic coupled sites may open new avenues for non-precious metal catalysis.

Multi-level hollow sphere rich in heterojunctions with dual function: Efficient microwave absorption and antiseptic

Effective electromagnetic wave absorption is now possible thanks to the design of the dielectric-magnetic double loss mechanism and the rich heterogeneous structure. In this study, hollow carbon spheres with rich heterostructures were synthesized using an easy and effective in situ growing approach. In addition to improving impedance matching, the hollow structure also reduces material density and weight. By modifying the load, this system can alter the dielectric characteristics of MXene, which in turn affects the sample's ability to absorb electromagnetic waves. MXene and the carbon material create a thick conductive network during the whole electromagnetic wave absorption process, creating the ideal environment for conduction loss. The sample's ability to attenuate electromagnetic waves is further improved by the interfacial polarization that the rich heterogeneous structure can produce. Co-magnetic nanoparticle nanoparticles are the main source of magnetic loss. The MXene@Co/C-100–800 (MCC-100–800) exhibits excellent electromagnetic wave absorption performance under the synergy of multiple loss mechanisms, with the maximum effective absorption bandwidth (EABmax) reaching 7.20 GHz and the minimum reflection loss (RLmin) being –53.99 dB at 2.10 mm. Finally, this work is guided by the coating engineering of MXene and provides new ideas for the rational design of heterostructures of nanomaterials.

Sustainable Synthesis of Hierarchically Porous Hollow Carbon Spheres for Enhanced Zinc-Ion Hybrid Supercapacitors

Sustainable Synthesis of Hierarchically Porous Hollow Carbon Spheres for Enhanced Zinc-Ion Hybrid Supercapacitors

Development of Dual N, S‐Heteroatom Doped Hollow Carbon Spheres as an Alternative Electrocatalyst for Oxygen Reduction Reaction in Alkaline Medium

AbstractHollow heteroatom‐doped mesoporous carbons were found to be an efficient non‐noble metal catalyst to enhance the oxygen reduction reaction (ORR) in fuel cells. Here, we use dopamine hydrochloride (DHC) and dibenzyl disulfide (DBS) as the nitrogen and sulfur precursors to infiltrate N and S into the HCS in a single‐step process. Dibenzyl disulfide is less explored in literature as a sulfur dopant. Due to its high sulfur content and high boiling point, dibenzyl disulfide acts as an excellent sulfur dopant and can withstand the carbonization process. Among them, NSMHCS‐0.2 obtained by adding 0.2 g of dibenzyl disulfide at 31 h intervals to the polydopamine (PDA) loaded silica leads to the ideal N, S dual hetero‐atom doping in NSMHCS. Notably, it has a high shell thickness (45 nm), high BET surface area (637 m2 g−1), high pyridinic nitrogen (13.54 %), and thiophene sulfur (89.8 %) concentration. Such property tuning paved the way to reach a high positive onset potential (0.86 V vs RHE) and a limiting current density of 3.64 mA cm−2 at 0.4 V vs RHE. Additionally, NSMHCS‐0.2 has shown superior methanol tolerance and strong electrochemical stability when compared to Pt/C 20 %.

Flexible construction of three-dimensional continuous conductive structure by hollow carbon sphere and CNT for promoted ions transport in flow-electrode capacitive deionization

Flow-electrode capacitive deionization (FCDI) emerges as a promising desalination technique, characterized by its unlimited desalination capacity, seamless operation, and easy scalability. However, challenges such as discontinuous electronic network, inadequate dispersion of suspended carbon particles, and hindered electron/ion transport pathways have impeded the full potential of FCDI. This study addresses the above issues by synergistically leveraging the advantage of hollow carbon sphere (HCS) and CNT to construct a flexible, continuous three-dimensional conductive network (HCS@CNT) as the flow-electrode for FCDI. The incorporation of HCS substantially improves the fluidity and effective collision of the flow-electrode slurry. Simultaneously, the bridging effect of CNT facilitates smooth ion transport routes and rapid electron/ion transfer. Moreover, the spherical structure of HCS as a node can effectively alleviate the agglomeration of CNT due to its inherent good fluidity. As a result, the meticulously designed HCS@CNT flow-electrode demonstrates outstanding rheological behavior with excellent hydrophilicity, a large specific capacitance, and low ion diffusion resistance. During desalination tests, the HCS@CNT flow-electrode exhibited a high average salt removal rate (0.56 µmol min−1 cm−2), appropriate energy-normalized removal salt (15 µmol J−1), and notable charge efficiency (89 %) in a 1 g L-1 NaCl solution. Impressively, it maintained good stability and continuity over a continuous 10-hour desalination process, showcasing substantial potential for treating highly concentrated saline water. In addition, density functional theory (DFT) calculations provided additional insights, confirming that the construction of HCS@CNT facilitated interfacial charge transfer and electron transport from HCS to CNT. This innovative approach sheds light on enhancing electron/ion transfer by harnessing the unique structural characteristics of the flow-electrode.