| 1. |
- Fernandes, Arthur B., et al.
(author)
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Recoverable and Reusable Polymer Microbead-Supported Metal Nanocatalysts for Redox Chemical Transformations
- 2020
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In: ACS APPLIED NANO MATERIALS. - : AMER CHEMICAL SOC. - 2574-0970. ; 3:2, s. 1722-1730
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Journal article (peer-reviewed)abstract
- Metal nanoparticles have been widely exploited in catalysis, but their full impact on the environment and human health is still under debate. Here we describe the one-step fabrication of recoverable and reusable polymer microbead-supported metal and metal oxide nanocatalysts for application in batch reactions and flow systems. Au, Ag, and Fe3O4 nanoparticles were prepared directly at the surface of commercial benzylamine-coated spherical polymer beads in water by using low-energy microwave radiation for 5 min. The functionalization of microbead surface with betalamic acid, an antioxidant from plant origin, before irradiation changes the morphology and catalytic properties of the grafted nanoparticles. No leaching of the active phase was observed during the application of these effective and ready-to-use nanocatalysts on the reduction of 4-nitrophenol and oxidation of dihydrorhodamine 123. The supported nanocatalysts were recovered by filtration and/or magnetic separation and reused up to three times without significant drop in catalytic performance. These results can stimulate the controlled and facile synthesis of recoverable microbead-supported magnetic and nonmagnetic nanocatalysts that can be applied under myriad reaction conditions and reused multiple times.
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| 2. |
- Fernandes, Daniel L. A., et al.
(author)
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Green microfluidic synthesis of monodisperse silver nanoparticles via genetic algorithm optimization
- 2016
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:98, s. 95693-95697
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Journal article (peer-reviewed)abstract
- A scalable and green procedure for the microfluidic flow synthesis of monodisperse silver nanoparticles is reported. Beetroot extract is used both as a reducing and growth-regulating agent. A multi-objective genetic algorithm was used to automate the optimization of the reaction and reduce sample polydispersity observed in previous reports. The proposed methodology ensures high-quality nanoparticles in a rapidly manner and devoid of human skill or intuition, essential for method standardization and implementation.
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| 3. |
- Garlisi, Corrado, et al.
(author)
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N-TiO2/Cu-TiO2 double-layer films : Impact of stacking order on photocatalytic properties
- 2017
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In: Journal of Catalysis. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0021-9517 .- 1090-2694. ; 353, s. 116-122
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Journal article (peer-reviewed)abstract
- In this work, we report for the first time a unique configuration of N-doped and Cu-doped TiO2 bilayer. The activity of TiO2 was improved by combining Cu- and N-doping in a layered thin-film structure. The impact of the stacking order was studied, pointing out how the best arrangement is by far the one with Cu-TiO2 as the top layer. The results reveal a unique and simple way to enhance the photocatalytic response of TiO2 in the visible domain.
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| 4. |
- Paun, Cristina, et al.
(author)
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Continuous-Flow Hydrogenation of D-Xylose with Bimetallic Ruthenium Catalysts on Micrometric Alumina
- 2017
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In: Synthesis and Catalysis: Open Access. - : Insight Medical Publishing. ; 2:1
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Journal article (peer-reviewed)abstract
- Continuous-flow hydrogenation of D-xylose to xylitol was evaluated with pristine and silver modified ruthenium supported on micrometric alumina. The original size of alumina support is required for direct use in flow hydrogenation since it prevents setup clogging. The parent ruthenium catalyst shows high activity and selectivity to the desired product. However, there was an evident competition between adsorption of substrate and product desorption, and ruthenium nanoparticles aggregation. In situ modification of the parent catalyst with silver improved catalysts stability and minimize the competitive adsorption behavior between reactant and product.
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| 5. |
- Paun, Cristina, et al.
(author)
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Flow hydrogenation of p-nitrophenol with nano-Ag/Al2O3
- 2016
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:90, s. 87564-87568
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Journal article (peer-reviewed)abstract
- Herein, we report the first continuous-flow hydrogenation of p-nitrophenol to p-aminophenol with molecular hydrogen, as a reducing agent. This reaction converts a known pollutant into a high value product with only water as a by product, which is also the solvent. We employed Ag nanoparticles (<5 nm) supported on alumina, which were synthesized directly on low surface area alumina, avoiding the need for catalyst post-processing to confer the required nominal size for flow applications.
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| 6. |
- Paun, Cristina, et al.
(author)
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Hydrogenation by Silver Catalysts
- 2016
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In: Hydrogenation With Low-Cost Transition Metals. - : CRC PRESS-TAYLOR & FRANCIS GROUP. ; , s. 155-195
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Book chapter (peer-reviewed)abstract
- This chapter deals with hydrogenation mediated by silver metal present as supported and unsupported nanoparticles. In the chapter, we highlight synthetic procedures for the preparation of metallic silver nanoparticles and their applications in catalysis. The emphasis is on catalytic reactions for production of fine and pharmaceutical chemicals.
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| 7. |
- Paun, Cristina, et al.
(author)
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p-Nitrophenol flow hydrogenation with nano-Cu2O grafted on polymeric resin
- 2017
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In: Catalysis communications. - : ELSEVIER SCIENCE BV. - 1566-7367 .- 1873-3905. ; 92, s. 61-64
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Journal article (peer-reviewed)abstract
- Hydrogenation is the most widely used method to reduce organic compounds. There is a demand for the development of active heterogeneous catalysts based on 3d transition metals for economical and environmental reasons. Herein, we report the first continuous-flow hydrogenation of p-nitrophenol to p-aminophenol with molecular hydrogen and heterogeneous nano-Cu2O as reducing agent and Catalyst, respectively. This reaction converts a known pollutant into a high value product with only water as by-product, which is also the solvent. One-pot synthesis methodology was adapted to prepare the catalyst, which confers sufficient nominal size for direct usage in flow reactions, which are preferred from an engineering, industrial, and environmental perspective. Catalyst reactivity was linked to difference in density-of-states between surface and bulk sites, and nanoscale size of active material.
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| 8. |
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| 9. |
- Pavliuk, Mariia V., et al.
(author)
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Nano-hybrid plasmonic photocatalyst for hydrogen production at 20% efficiency
- 2017
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- The efficient conversion of light energy into chemical energy is key for sustainable human development. Several photocatalytic systems based on photovoltaic electrolysis have been used to produce hydrogen via water reduction. However, in such devices, light harvesting and proton reduction are carried separately, showing quantum efficiency of about 10–12%. Here, we report a nano-hybrid photocatalytic assembly that enables concomitant reductive hydrogen production and pollutant oxidation with solar-to-fuel efficiencies up to 20%. The modular architecture of this plasmonic material allows the fine-tuning of its photocatalytic properties by simple manipulation of a reduced number of basic components.
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| 10. |
- Sá, Jacinto, et al.
(author)
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Evaluation of Pt and Re oxidation state in a pressurized reactor : difference in reduction between gas and liquid phase.
- 2011
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In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 47:23, s. 6590-2
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Journal article (peer-reviewed)abstract
- Determination of metal oxidation state under relevant working conditions is crucial to understand catalytic behaviour. The reduction behaviour of Pt and Re was evaluated simultaneously as a function of support and solvent in a pressurized reactor (autoclave). The bimetallic catalysts are used in selective hydrogenation of carboxylic acids and amides. Gas phase reduction reduced the metals more efficiently, in particular Pt.
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