Double-shelled Hollow Microspheres Research Articles

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.

Synergistic Resonances and Charge Transfer in Double-Shelled ZnO Hollow Microspheres for High-Performance Semiconductor-Based SERS Substrates

Synergistic Resonances and Charge Transfer in Double-Shelled ZnO Hollow Microspheres for High-Performance Semiconductor-Based SERS Substrates

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.

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.

Double-shell ZnO hollow microspheres prepared by template-free method for ethanol detection

Oxide semiconductors with multi-shell hollow architecture are considered favorable candidates as sensing materials for applications in high-performance gas sensors. Herein, the solid, core-shell, and double-shell zinc oxide (ZnO) microspheres were successfully prepared via a facile template-free method. Compared with solid and core-shell spheres, the gas sensor based on double-shell sphere exhibited the highest response to 100 ppm ethanol at 275 °C (∼ 47.4), which was about 4.8-fold higher than that of the solid sphere (∼ 9.8) under the same conditions. Furthermore, the detection limit of the double-shell ZnO microsphere could reach 1 ppm. The enhancement mechanism of the ethanol gas-sensing performance was systematically discussed.

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.

Double-shelled hollow polymer microspheres as acid and metallic colloid bi-functional catalyst for a deactalization-hydrogenation tandem reaction

The double-shelled hollow polymer microspheres with a carboxylic acid in the inner shell and palladium metallic nanocolloids in the outer shell were prepared as a bi-functional catalyst for a tandem reaction including deacetalization on-hydrogenation from benzaldehyde dimethyl acetate to benzyl alcohol. The double-shelled hollow poly(ethyleneglycol dimethacrylate-co-acrylic acid) (PAA) and poly(ethyleneglycol dimethacrylate-co-N-vinyl pyrrolidone) (PNVP) microspheres were synthesized by a two-stage refluxing precipitation copolymerization in presence of 3-(trimethoxysilyl) propyl methacrylate (MPS)-modified silica as seeds to get SiO2/Pt-BA/SiO2/PNVP tetra-layer microspheres with the subsequent hydrolysis of t-butyl ester to acid group and selective removal of the silica inner core and the sandwiched third layer. The palladium nano-colloids in outer-shell were prepared by the in-situ ethanol reduction of Pd(II) after the coordination of palladium acetate with N-pyrrolidone (NVP) groups in presence of SiO2/Pt-BA/SiO2/PNVP tetra-layer microspheres as stabilizers.

Double-shelled hybrid MgFe2O4/Fe2O3 hollow microspheres as a high-capacity anode for lithium-ion batteries

Ternary metal oxides Fe2O3 and MgFe2O4 have attracted considerable attention as lithium anode materials owing to their high theoretical capacities, environmental friendliness, and low cost; however, their rapid capacity decay and large volume expansion inhibit their lithium storage performance. Herein, we synthesize hybrid MgFe2O4/Fe2O3 hollow microspheres (MFO/FO-HS) hydrothermally, via the polyol reaction of ethylene glycol, followed by calcination at different temperatures. The surface morphology was tuned by adjusting the calcination temperature, assisted by inward and outward Ostwald ripening. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were performed to investigate the physio-chemical properties of the prepared samples. The sample calcined at 450 °C exhibited an excellent electrochemical performance and retained a reversible capacity of 1390 mAh g−1 after 160 cycles, indicating the significant role of calcination temperature in tuning the structural and electrochemical properties of anode materials. The double-shelled hollow microspheres inhibit rapid capacity decay and prevent severe volume expansion during the electrochemical process. This work opens new paths toward constructing an electrode material with a high electrochemical performance.

Structural tuning of multishelled hollow microspheres for boosted peroxymonosulfate activation and selectivity: Role of surface superoxide radical

Herein, a multi-shelled hollow micro-reactor with tunable shell number, thickness and porosity is constructed by nanosized Co3O4 to catalyze peroxymonosulfate (PMS) for the first time. Triple-shelled hollow microspheres (TS-HM) exhibit superior catalytic activity with the degradation rate of 0.4158 min−1, which is 22, 5.8, 1.9 times of that of solid nanoparticles, quadruple-shelled hollow microspheres (QS-HM), and double-shelled hollow microspheres (DS-HM), respectively. Such an outstanding performance of TS-HM is attributed to more exposed active sites, strong capacity of CoII regeneration and desired structure stability. Furthermore, the selectivity of 2-cholorophenol (2-CP) over humic acid (HA) is optimized by tuning shell thickness and porosity. The thick shell and narrow pore size are recognized as the dominant contributors based on size exclusion effects. Significantly, mechanistic studies reveal that O2·− is generated on the catalyst surface via O2 adsorption and reduction by oxygen vacancies, and plays an important role for CoII regeneration.

Construction of PdO-decorated double-shell ZnSnO3 hollow microspheres for n-propanol detection at low temperature

The sensor based on 4 wt% PdO-loaded double-shell ZnSnO3 hollow microspheres shows rapid response/recovery speed to n-propanol at low working temperature.

SnO2/ZnSnO3 double-shelled hollow microspheres based high-performance acetone gas sensor

In this study, the preparation process and the sensing performance toward acetone of SnO2/ZnSnO3 composite microspheres with the double-shelled hollow structure were reported. It was synthesized by one-step chemical vapor deposition (CVD) method using sucrose as solid precursor pyrolysis carbon template. In addition, the internal structure of the composite microspheres can be effectively controlled by changing the sucrose concentration. The perfect double-shelled hollow structure (average diameter of about 500 nm) of the prepared sensitive materials was observed through SEM and TEM. It is noteworthy that the double-shelled hollow structure had a large specific surface area (188.60 m2/g), which can both increase the internal and external reactive sites of the sensitive material effectively. Compared with other obtained composite microspheres, the SnO2/ZnSnO3 sample with double-shelled hollow structure presented the best sensing performance, and the response to 100 ppm acetone reached 30 at 290 °C. Furthermore, it also presented excellent selectivity and long-term stability to acetone. The excellent performance was attributed to the synergistic effect of the double-shelled hollow structure with large specific surface area and the n-n heterojunction at the interface of the SnO2/ZnSnO3 composite. The sensing mechanisms of the double-shelled hollow SnO2/ZnSnO3 composite material were discussed in detail.

Double-shell hollow glass microspheres@Co2SiO4 for lightweight and efficient electromagnetic wave absorption

Novel double-shell hollow glass microspheres (HGMs) coated with cobalt silicate (Co2SiO4) were synthesized by hydrothermal method with a further calcination process. Through the detailed characterization of phase, morphology and electromagnetic (EM) wave absorption properties of the samples, we found that the combination of magnetic loss component Co2SiO4 and dielectric loss component HGMs plays an important role in the introduction and dissipation of EM wave. In the discussion part, we focused on comparing the composite with the single component and explained the influence of the new composite structure on the stability and EM wave absorbing properties of the materials in detail. The minimum reflection loss (RLmin) of the HGMs@Co2SiO4 reached up to − 46.7 dB with a matching thickness (d) of 2.9 mm, and the corresponding effective absorption bandwidth (fE, RL < − 10 dB) was 5.92 GHz. We are confident that the new type of double-shell HGMs@Co2SiO4 will be an excellent candidate for a new generation of stable, lightweight and efficient EM wave absorbing material.

Construction of Double-Shell Hollow TiO2 toward Solvent-Free Polyurethane Films

Solvent-free polyurethane (SFPU) has a fast curing film-forming speed, making the foam and coating layer very dense. Therefore, this film structure has poor hygienic properties. Here, we propose a strategy for introducing double-shell hollow TiO2 microspheres (S@S-TiO2) having a large specific surface area and a special inner and outer cavity structure in the SFPU film, so that the film would develop excellent hygienic properties. First, novel S@S-TiO2 were successfully prepared by a one-step hydrothermal method, which is very rare. Then, the obtained S@S-TiO2 were introduced into SFPU to prepare an S@S-TiO2/SFPU composite film. Then, the morphology and dispersibility of S@S-TiO2 and the composite film were studied by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results show that S@S-TiO2 have an important effect on the hygienic properties of the composite film. Finally, the synergistic effect of TiO2 on the properties of the polyurethane film was further proved by molecular dynamics simulation.

Synthesis of TiO2-x/W18O49 hollow double-shell and core-shell microspheres for CO2 photoreduction under visible light.

TiO2-x/W18O49 with core-shell or double-shelled hollow microspheres were synthesized through a facile multi-step solvothermal method. The formation of the hollow microspheres with a double-shell was a result of the Kirkendall effect during the solvothermal treatment with concentrated NaOH. The advanced architecture significantly enhanced the electronic properties of TiO2-x/W18O49, improving by more than 30 times the CO2 photoreduction efficiency compared to the pristine W18O49. Operando DRIFTS measurements revealed that the yellow TiO2-x was a preferable CO2 adsorption and conversion site.

A novel nonenzymatic electrochemical sensor based on double-shelled CuCo2O4 hollow microspheres for glucose and H2O2

CuxCo3-xO4 (x = 0.5, 1, 1.5, 2) are successfully synthesized through hydrothermal and calcination processes. A series of electrochemical tests reveal that all of them exhibit electrocatalytic activity towards glucose and H2O2. Among them, CuCo2O4 (x = 1) has a unique double-shelled hollow structure and shows higher catalytic performance. The electrochemical sensor based on CuCo2O4 displays a linear range from 2.5 μM to 7.9 mM, with a sensitivity of 400.0 μA mM−1cm−2 for the detection of glucose. As for H2O2, it shows a linear range from 10.0 μM to 8.9 mM, with a sensitivity of 94.1 μA mM−1cm−2. The sensor also exhibits short response time (<3 s), good selectivity, reproducibility, and stability over 18 days. Thus, this novel non-enzyme sensor has potential application in glucose and H2O2 detection.

The Mn-promoted double-shelled CaCO3 hollow microspheres as high efficient CO2 adsorbents

Novel Mn-promoted double-shelled hollow CaCO3 microspheres were successfully synthesized by a versatile template method using carbon microspheres as sacrificial templates, achieving the controllable adjustment of Ca-Mn molar ratio, microsphere size and shell thickness. The Mn-promoted hollow CaCO3 microspheres with self-supported double shells effectively handled the collapsing problem led by the continuous volume variations, of which the adsorption performance notably outperformed that of the pure CaCO3 counterpart. The uniformly distributed Mn considerably enhanced structural stability of the double-shelled hollow microspheres and reduced the crystalline size of CaCO3. Furthermore, the existence of Mn promoted the ability of donating electrons of CaO to CO2 and was presumably to bring about oxygen vacancies. The sorbent Ca12Mn1-500 exhibited an initial CO2 adsorption capacity of 0.62 g-CO2/g-ads and a final one of 0.53 g-CO2/g-ads after 25 adsorption-desorption cycles.

Design of Mn-doped CdxZn1-xSe@ZnO triple-shelled hollow microspheres for quantum dots sensitized solar cells with improved photovoltaic performance

Mn-CdxZn1-xSe@ZnO multi-shelled (including single-shelled, double-shelled, and triple-shelled) hollow microspheres (HMS) were successfully synthesized for application in quantum dots sensitized solar cell (QDSSC). The influence of shell numbers on photovoltaic performance of QDSSC were investigated. The results showed that larger surface area, repeated light reflection and reinforced light scattering can be achieved with triple-shelled HMS, which can improve light harvesting efficiency. Furthermore, midgap state created by Mn-doping in CdxZn1-xSe will facilitate electrons injection and collection from excited CdxZn1-xSe quantum dots (QDs) to ZnO. The multi-shelled effects and Mn-doping finally improve the short-circuit current (Jsc) of Mn-CdxZn1-xSe@ZnO tripled-shelled HMS solar cell to 20.21 mA cm−2, leading to the power conversion efficiency significantly enhanced to 3.39%.

Double-shell Li-rich layered oxide hollow microspheres with sandwich-like carbon@spinel@layered@spinel@carbon shells as high-rate lithium ion battery cathode

Li-rich layered oxides (LRLO) with high specific capacity over 250 mA h g−1 are attractive cathode material candidates for the next-generation high performance lithium-ion batteries. However, LRLO always suffers from low initial Coulombic efficiency, poor cycling and rate properties. Herein, unique double-shell LRLO hollow microspheres with sandwich-like carbon@spinel@layered@spinel@carbon shells (LRLO-500@S@C) were successfully synthesized via a facile template-free method, followed by carbothermal reduction treatment. The fabricated LRLO-500@S@C cathode delivers a high initial charge capacity of 312.5 mA h g−1 with a large initial Coulombic efficiency of 89.7%. After cycling 200 times, large and stable discharge capacities of 228.3 mA h g−1 and 196.1 mA h g−1 can be obtained at 1.0 C and 5.0 C, respectively. Moreover, coin-type full cell with LRLO-500@S@C as cathode and Li4Ti5O12 as anode delivers outstanding lithium storage properties. The impressive electrochemical performances of LRLO-500@S@C cathode material can be attributed to its multiscale coordinated design based on hierarchical double-shell hollow construction, the special layered@spinel@carbon heterostructured shells and the introduced oxygen vacancies, which benefit to shorten Li-ion diffusion paths, strengthen structural stability and reduce side reactions.

CTAB-functionalized C@SiO2 double-shelled hollow microspheres with enhanced and selective adsorption performance for Cr(VI)

A novel cetyltrimethylammonium bromide (CTAB)-functionalized C@SiO2 with structure of double-shelled hollow microspheres (F-C@SiO2) was successfully synthesized by hydrolysis of tetraethyl orthosilicate (TEOS) on the carbonaceous hollow sphere (C). The as-prepared F-C@SiO2, C@SiO2 resulting from extracting CTAB from F-C@SiO2, and C were characterized comparatively by XRD, TGA-DSC, SEM, TEM, N2 adsorption-desorption and zeta potential. Batch adsorption experiments show that the F-C@SiO2 with CTAB functionalization presents the fastest adsorption kinetics and the highest adsorption capacity of 202.02 mg g−1 towards Cr(VI) among the samples (161.81 mg g−1 for C@SiO2 and 33.16 mg g−1 for C, respectively). The adsorption mechanisms involving the electrostatic attraction and reduction reaction were also discussed. In addition, coexistence of the ion interference experiments show that the F-C@SiO2 has a highly selective adsorption capacity of 91.11 mg g−1 towards Cr(VI) under a multiple system of Cr(VI), Cu2+, Cd2+, Zn2+, and Ni2+ with the concentration of 100 mg L−1, respectively. The successful decoration of the CTAB and the SiO2 onto the external surface of the hollow C spheres provides an effective method to develop promising composite for Cr(VI) removal from wastewater.

Al-Stabilized Double-Shelled Hollow CaO-Based Microspheres with Superior CO2 Adsorption Performance

Novel, double-shelled hollow Al-stabilized CaO-based microspheres were successfully prepared through a facile, green method using carbonaceous microspheres as sacrificial templates. Both the morphological and adsorption performance differences, between employing organic and inorganic calcium salt as calcium precursors, to fabricate the double-shelled hollow microspheres were exhibited. Derived from calcium acetate, the Al-stabilized double-shelled hollow microspheres with denser shells showed excellent stability. This was ascribed to the shells that were composed of small CaCO3 nanocrystallite (grain size of <50 nm) and homogeneously distributed stabilizer, Al2O3. Well-spherical, porous hollow structures facilitated CO2 diffusion and buffered mechanical stresses generated by volume change during the calcium looping. The sorbent, CaA40Al1, exhibited a favorable high-temperature CO2 adsorption performance with the capacity of 0.40 g of CO2/g of ads over 60 carbonation/calcination cycles.