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In this paper, Cu and Ce were added to melt-spun Al-Ag precursor alloys to refine the microstructures of nanoporous Ag and Ag/CeO2 composite catalysts for NaBH4 oxidation. After the precursor alloys were dealloyed in 20% NaOH, calcined in air and corroded again in 50% NaOH, Ag2Al in the precursor alloys was completely removed, and refined nanoporous Ag could be obtained; from this process, the finest microstructures were exhibited by Al84Ag8Cu8. When more than 0.3% Ce was added to the Al84Ag8Cu8 ribbons, a refined nanoporous Ag material that consisted of CeO2 nanorods interspersed between Ag ligaments was obtained. Electrochemical measurements indicated that the catalytic properties were clearly increased due to the Cu addition to the Al-Ag alloy. After Ce was added to the Al84Ag8Cu8 ribbons, the catalytic properties of the resulting material were further improved. In regard to melt-spun Al84Ag8Cu8Ce0.5, the obtained nanoporous Ag/CeO2 presented the best properties, and its current density was 2.5 times that of Al84Ag8Cu8, 3.1 times that of Al90Ag8Cu2 and 2.3 times that of Ag/Ce from the Al79Ag15Ce6 precursor alloy without Cu. It was believed that the core-shell structure composed of Ag and Cu-rich phases formed during dealloying could limit the diffusion of Ag and prevent the coarsening of Ag ligaments. Thus, the refined microstructures could provide a large specific surface or additional active sites for the catalytic reaction. Strong interactions resulted from the many interfaces between the Ag ligaments and interspersed CeO2 nanorods, and the more effective utilization of Ag was due to the decomposition of Ag2Al; this result was the key reason for the clear improvement in catalytic performance.
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In this paper, Cu and Ce were added to melt-spun Al-Ag precursor alloys to refine the microstructures of nanoporous Ag and Ag/CeO2 composite catalysts for NaBH4 oxidation. After the precursor alloys were dealloyed in 20% NaOH, calcined in air and corroded again in 50% NaOH, Ag2Al in the precursor alloys was completely removed, and refined nanoporous Ag could be obtained; from this process, the finest microstructures were exhibited by Al84Ag8Cu8. When more than 0.3% Ce was added to the Al84Ag8Cu8 ribbons, a refined nanoporous Ag material that consisted of CeO2 nanorods interspersed between Ag ligaments was obtained. Electrochemical measurements indicated that the catalytic properties were clearly increased due to the Cu addition to the Al-Ag alloy. After Ce was added to the Al84Ag8Cu8 ribbons, the catalytic properties of the resulting material were further improved. In regard to melt-spun Al84Ag8Cu8Ce0.5, the obtained nanoporous Ag/CeO2 presented the best properties, and its current density was 2.5 times that of Al84Ag8Cu8, 3.1 times that of Al90Ag8Cu2 and 2.3 times that of Ag/Ce from the Al79Ag15Ce6 precursor alloy without Cu. It was believed that the core-shell structure composed of Ag and Cu-rich phases formed during dealloying could limit the diffusion of Ag and prevent the coarsening of Ag ligaments. Thus, the refined microstructures could provide a large specific surface or additional active sites for the catalytic reaction. Strong interactions resulted from the many interfaces between the Ag ligaments and interspersed CeO2 nanorods, and the more effective utilization of Ag was due to the decomposition of Ag2Al; this result was the key reason for the clear improvement in catalytic performance.
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In this work, NiCo2S4 nanoparticles for supercapacitors are successfully synthesized with a top-down strategy, using a novel dealloying method with an ion exchange reaction. The surface morphology and x-ray diffraction investigations demonstrated that NiCo2S4 nanoparticles are interconnected by ligaments of the synthesized sample. The dealloyed NiCo2S4 shows an enhanced electrochemical performance of about 1132.5 F g-1 at 0.5 A g-1; kinetic analysis implies a surface-controlled contribution from NiCo2S4 (53.86% capacitive contributions). Notably, the NiCo2S4//AC (active carbon) device displays a comparatively high energy density (22.83 Wh kg-1), maximum power density (1327.1 W kg-1) and superior cycling performance (capacitance retention of 108% after 30 000 cycles).
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Inspired by kinetics, the design of hollow hierarchical electrocatalysts through large-scale integration of building blocks is recognized as an effective approach to the achievement of superior electrocatalytic performance. In this work, a hollow, hierarchical Co3O4 architecture (Co3O4 HHA) was constructed using a coordinated etching and precipitation (CEP) method followed by calcination. The resulting Co3O4 HHA electrode exhibited excellent electrocatalytic activity in terms of high sensitivity (839.3 µA mM-1 cm-2) and reliable stability in glucose detection. The high sensitivity could be attributed to the large specific surface area (SSA), ample unimpeded penetration diffusion paths and high electron transfer rate originating from the unique two-dimensional (2D) sheet-like character and hollow porous architecture. The hollow hierarchical structure also affords sufficient interspace for accommodation of volume change and structural strain, resulting in enhanced stability. The results indicate that Co3O4 HHA could have potential for application in the design of non-enzymatic glucose sensors, and that the construction of hollow hierarchical architecture provides an efficient way to design highly active, stable electrocatalysts.
Assuntos
Técnicas Biossensoriais/métodos , Cobalto/química , Glucose/análise , Óxidos/química , Glicemia/análise , Catálise , Técnicas Eletroquímicas , Eletrodos , Oxirredução , Espectroscopia Fotoeletrônica , Difração de Raios XRESUMO
OBJECTIVE: To comprehensively analyze the cost-utility of robotic surgery in clinical practice and to investigate the reporting and methodological quality of the related evidence. METHODS: Data on cost-utility analyses (CUAs) of robotic surgery were collected in seven electronic databases from the inception to July 2021. The quality of the included studies was assessed using the CHEERs and QHES checklists. A systematic review was performed with the incremental cost-effectiveness ratio as the outcome of interest. RESULTS: Thirty-one CUAs of robotic surgery were eligible. Overall, the identified CUAs were fair to high quality, and 63% of the CUAs ranked the cost-utility of robotic surgery as "favored," 32% categorized as "reject," and the remaining 5% ranked as "unclear." Although a high heterogeneity was present in terms of the study design among the included CUAs, most studies (81.25%) consistently found that robotic surgery was more cost-utility than open surgery for prostatectomy (ICER: $6905.31/QALY to $26240.75/QALY; time horizon: 10 years or lifetime), colectomy (dominated by robotic surgery; time horizon: 1 year), knee arthroplasty (ICER: $1134.22/QALY to $1232.27/QALY; time horizon: lifetime), gastrectomy (dominated by robotic surgery; time horizon: 1 year), spine surgery (ICER: $17707.27/QALY; time horizon: 1 year), and cystectomy (ICER: $3154.46/QALY; time horizon: 3 months). However, inconsistent evidence was found for the cost-utility of robotic surgery versus laparoscopic surgery and (chemo)radiotherapy. CONCLUSIONS: Fair or high-quality evidence indicated that robotic surgery is more cost-utility than open surgery, while it remains inconclusive whether robotic surgery is more cost-utility than laparoscopic surgery and (chemo)radiotherapy. Thus, an additional evaluation is required.
Assuntos
Laparoscopia , Procedimentos Cirúrgicos Robóticos , Análise Custo-Benefício , Humanos , MasculinoRESUMO
Although sheet-like materials have good electrochemical properties, they still suffer from agglomeration problems during the electrocatalytic process. Integrating two-dimensional building blocks into a hollow cage-like structure is considered as an effective way to prevent agglomeration. In this work, the hierarchical NiCo2O4 nanocages were successfully synthesized via coordinated etching and precipitation method combined with a post-annealing process. The nanocages are constructed through the interaction of two-dimensional NiCo2O4 nanosheets, forming a three-dimensional hollow hierarchical architecture. The three-dimensional supporting cavity effectively prevents the aggregation of NiCo2O4 nanosheets and the hollow porous feature provides amounts of channels for mass transport and electron transfer. As an electrocatalytic electrode for methanol, the NiCo2O4 nanocages-modified glassy carbon electrode exhibits a lower overpotential of 0.29 V than those of NiO nanocages (0.38 V) and Co3O4 nanocages (0.34 V) modified glassy carbon electrodes. The low overpotential is attributed to the prominent electrocatalytic dynamic issued from the three-dimensional hollow porous architecture and two-dimensional hierarchical feature of NiCo2O4 building blocks. Furthermore, the hollow porous structure provides sufficient interspace for accommodation of structural strain and volume change, leading to improved cycling stability. The NiCo2O4 nanocages-modified glassy carbon electrode still maintains 80% of its original value after 1000 consecutive cycles. The results demonstrate that the NiCo2O4 nanocages could have potential applications in the field of direct methanol fuel cells due to the synergy between two-dimensional hierarchical feature and three-dimensional hollow structure.
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The lithium/sulfuryl chloride battery has been used as a primary power source because of its high energy/power density and level of safety. However, disadvantages regarding the sluggish kinetics of the electrode materials have limited its further energy related applications. Herein, we report an efficient approach to prepare nitrogen-doped graphene nanocages with high surface roughness to overcome this issue. The combination of a porous wrinkled surface and hollow structure can properly accommodate the volume-change, promote charge transfer, and enhance structural stability. The designed composite electrode can deliver an initial voltage as high as 3.58 V, an advanced discharge time of 840 s, and an outstanding relative capacity (63.20 mA h) and rate capability (29.36%). This unique structure engineering strategy also provides a potentially cost-effective way for synthesizing other carbon materials and their application in various electrochemical energy storage devices.
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In this work, Ni(OH)2 nanocages@MnO2 nanosheets core-shell architecture (Ni(OH)2â¯NCs@MnO2 NSs CSA) was successfully prepared through coordinated etching and precipitation (CEP) route followed by hydrothermal reaction, and then tested as sensitive electrode material for detection of dopamine (DA). The three dimensional (3D) hollow Ni(OH)2 core effectively prevented the aggregation of MnO2 NSs, leading to high utilization rate of MnO2 NSs. Meanwhile, the two dimensional (2D) MnO2 shell endowed Ni(OH)2â¯NCs with larger specific area and abundant diffusion channels, facilitating mass transport. Ni(OH)2â¯NCs@MnO2 NSs CSA modified glassy carbon electrode (GCE) exhibited two satisfying sensitivities of 467.1 and 1249.9⯵Aâ¯mM-1 cm-2 within the two linear ranges of 0.02-16.30⯵M and 18.30-118.58⯵M, respectively. Furthermore, Ni(OH)2â¯NCs@MnO2 NSs CSA/GCE presented low detection limit of 1.75â¯nM and short response time of 1.14â¯s. Overall, Ni(OH)2â¯NCs@MnO2 NSs/GCE looks promising for analytical sensing of DA thanks to its prominent electrocatalytic dynamic issued from the 3D hollow structure@2D nanosheets core-shell architecture.
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Técnicas Biossensoriais , Dopamina/isolamento & purificação , Técnicas Eletroquímicas , Nanoestruturas/química , Dopamina/química , Hidróxidos/química , Compostos de Manganês/química , Níquel/químicaRESUMO
A PdO/CeO2 composite with a rod-like nanoporous skeletal structure was prepared by combining the dealloying of Al-Ce-Pd alloy ribbons with calcination. For CO oxidation and CH4 combustion, the nanoporous PdO/CeO2 composite exhibits excellent catalytic activity, and the complete reaction temperatures of CO and CH4 are 80 °C and 380 °C, respectively. In addition, the composite possesses excellent cycle stability, CO2 toxicity, and water resistance, and the catalytic activity hardly decreases after 100 h of long-term stability testing in the presence of water vapour (2 × 105 ppm). The results of a series of characterizations indicate that the enhanced catalytic activity can be attributed to the good dispersion of the PdO nanoparticles, large specific surface area, strong redox capacity, interaction between PdO and CeO2, and more surface active oxygen on PdO. The results of the characterization and experiments also indicate that the PdO nanoparticles, prepared by combining dealloying and calcination, have a stronger catalytic activity than do Pd nanoparticles. Finally, a simple model is used to summarize the catalytic mechanism of the PdO/CeO2 composite. It is hoped that this work will provide insights into the development of high-activity catalysts.
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Ni(OH)2 electrocatalysts have acquired lots of research attentions as ideal substitutes for noble metals. However, their electrocatalytic performance still cannot meet the demands for applications due to the difficulties in electron transfer and mass transport. According to kinetics principle, the construction of hollow structure is regarded as an effective method to achieve outstanding electrocatalytic performance. In this work, Ni(OH)2 hollow porous architecture (Ni(OH)2 HPA) was simply synthesized through a coordinating etching and precipitating (CEP) method for the building of enzymatic-free glucose sensors. Ni(OH)2 HPA presents large specific surface area (SSA), ordered diffusion channels, and structure stability. As a detection electrode for glucose, Ni(OH)2 HPA exhibits eminent electroactivity in terms of high sensitivity (1843 µA mM-1 cm-2), lower detection limit (0.23 µM), and short response time (1.4 s). The results demonstrate that Ni(OH)2 HPA has practical applications for construction of enzymatic-free electrochemical sensors. The design of hollow structure also provides an effective engineering method for high-performance sensors.
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Transition metal oxides (TMOs) have attracted extensive research attentions as promising electrocatalytic materials. Despite low cost and high stability, the electrocatalytic activity of TMOs still cannot satisfy the requirements of applications. Inspired by kinetics, the design of hollow porous structure is considered as a promising strategy to achieve superior electrocatalytic performance. In this work, cubic NiO hollow porous architecture (NiO HPA) was constructed through coordinating etching and precipitating (CEP) principle followed by post calcination. Being employed to detect glucose, NiO HPA electrode exhibits outstanding electrocatalytic activity in terms of high sensitivity (1323 µA mM-1 cm-2) and low detection limit (0.32 µM). The excellent electrocatalytic activity can be ascribed to large specific surface area (SSA), ordered diffusion channels, and accelerated electron transfer rate derived from the unique hollow porous features. The results demonstrate that the NiO HPA could have practical applications in the design of nonenzymatic glucose sensors. The construction of hollow porous architecture provides an effective nanoengineering strategy for high-performance electrocatalysts.