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576 KiB

Open AccessArticle

Green Biosynthesis and Characterization of Magnetic Iron Oxide (Fe₃O₄) Nanoparticles Using Seaweed (Sargassum muticum) Aqueous Extract

by Mahnaz Mahdavi, Farideh Namvar, Mansor Bin Ahmad and Rosfarizan Mohamad

Molecules 2013, 18(5), 5954-5964; https://doi.org/10.3390/molecules18055954 - 21 May 2013

Cited by 546 | Viewed by 22969

Abstract

The synthesis of nanoparticles has become a matter of great interest in recent times due to their various advantageous properties and applications in a variety of fields. The exploitation of different plant materials for the biosynthesis of nanoparticles is considered a green technology [...] Read more.

The synthesis of nanoparticles has become a matter of great interest in recent times due to their various advantageous properties and applications in a variety of fields. The exploitation of different plant materials for the biosynthesis of nanoparticles is considered a green technology because it does not involve any harmful chemicals. In this study, iron oxide nanoparticles (Fe₃O₄-NPs) were synthesized using a rapid, single step and completely green biosynthetic method by reduction of ferric chloride solution with brown seaweed (BS, Sargassum muticum) water extract containing sulphated polysaccharides as a main factor which acts as reducing agent and efficient stabilizer. The structural and properties of the Fe₃O₄-NPs were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray fluorescence spectrometry (EDXRF), vibrating sample magnetometry (VSM) and transmission electron microscopy. The average particle diameter as determined by TEM was found to be 18 ± 4 nm. X-ray diffraction showed that the nanoparticles are crystalline in nature, with a cubic shape. The nanoparticles synthesized through this biosynthesis method can potentially useful in various applications. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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1430 KiB

Open AccessArticle

Hydrogen Generation Using a CuO/ZnO-ZrO₂ Nanocatalyst for Autothermal Reforming of Methanol in a Microchannel Reactor

by Kuen-Song Lin, Cheng-Yu Pan, Sujan Chowdhury, Mu-Ting Tu, Wan-Ting Hong and Chuin-Tih Yeh

Molecules 2011, 16(1), 348-366; https://doi.org/10.3390/molecules16010348 - 7 Jan 2011

Cited by 32 | Viewed by 9939

Abstract

In the present work, a microchannel reactor for autothermal reforming of methanol using a synthesized catalyst porous alumina support-CuO/ZnO mixed with ZrO₂ sol washcoat has been developed and its fine structure and inner surface characterized. Experimentally, CuO/ZnO and alumina support with ZrO [...] Read more.

In the present work, a microchannel reactor for autothermal reforming of methanol using a synthesized catalyst porous alumina support-CuO/ZnO mixed with ZrO₂ sol washcoat has been developed and its fine structure and inner surface characterized. Experimentally, CuO/ZnO and alumina support with ZrO₂ sol washcoat catalyst (catalyst slurries) nanoparticles is the catalytically active component of the microreactor. Catalyst slurries have been dried at 298 K for 5 h and then calcined at 623 K for 2 h to increase the surface area and specific pore structures of the washcoat catalyst. The surface area of BET N₂ adsorption isotherms for the as-synthesized catalyst and catalyst/ZrO₂ sol washcoat samples are 62 and 108 ± 2 m²g⁻¹, respectively. The intensities of Cu content from XRD and XPS data indicate that Al₂O₃ with Cu species to form CuAl₂O₄. The EXAFS data reveals that the Cu species in washcoat samples have Cu-O bonding with a bond distance of 1.88 ± 0.02 Å and the coordination number is 3.46 ± 0.05, respectively. Moreover, a hydrogen production rate of 2.16 L h⁻¹ is obtained and the corresponding methanol conversion is 98% at 543 K using the CuO/ZnO with ZrO₂ sol washcoat catalyst. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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2351 KiB

Open AccessArticle

A General Strategy for the Preparation of Carbon Nanotubes and Graphene Oxide Decorated with PdO Nanoparticles in Water

by Hongkun He and Chao Gao

Molecules 2010, 15(7), 4679-4694; https://doi.org/10.3390/molecules15074679 - 2 Jul 2010

Cited by 57 | Viewed by 12156

Abstract

The preparation of carbon nanotube (CNT)/PdO nanoparticles and graphene oxide (GO)/PdO nanoparticle hybrids via a general aqueous solution strategy is reported. The PdO nanoparticles are generated in situ on the CNTs and GO by a one-step “green” synthetic approach in aqueous Pd(NO₃ [...] Read more.

The preparation of carbon nanotube (CNT)/PdO nanoparticles and graphene oxide (GO)/PdO nanoparticle hybrids via a general aqueous solution strategy is reported. The PdO nanoparticles are generated in situ on the CNTs and GO by a one-step “green” synthetic approach in aqueous Pd(NO₃)₂ solution under ambient conditions without adding any additional chemicals. The production of PdO is confirmed by energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermal gravimetric analysis. The morphologies of the resulting CNT/PdO and GO/PdO nanohybrids are characterized by transmission and/or scanning transmission electron microscopy. PdO nanoparticles with an average size of 2–3 nm in diameter are decorated evenly along the surfaces of CNTs and GO. This synthesis strategy is demonstrated to be compatible for 1) CNTs with different modifications, including pristine, oxidized, and polymer-functionalized CNTs; 2) different types of CNTs, including single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multiwalled carbon nanotubes (MWCNTs); and 3) different shapes of carbon materials, including tubular CNTs and planar GO. The as-prepared CNT/PdO and GO/PdO nanohybrids can be transformed into CNT/Pd and GO/Pd nanohybrids by reduction with NaBH₄, and can then be used as a heterogeneous catalyst in the catalytic reduction of 4-nitrophenol. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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808 KiB

Open AccessArticle

Palladium/Zirconium Oxide Nanocomposite as a Highly Recyclable Catalyst for C-C Coupling Reactions in Water

by Antonio Monopoli, Angelo Nacci, Vincenzo Calò, Francesco Ciminale, Pietro Cotugno, Annarosa Mangone, Lorena Carla Giannossa, Pietro Azzone and Nicola Cioffi

Molecules 2010, 15(7), 4511-4525; https://doi.org/10.3390/molecules15074511 - 24 Jun 2010

Cited by 60 | Viewed by 9850

Abstract

Palladium nanoparticles have been electrochemically supported on zirconium oxide nanostructured powders and all the nanomaterials have been characterized by several analytical techniques. The Pd/ZrO₂ nanocatalyst is demonstrated to be a very efficient catalyst in Heck, Ullmann, and Suzuki reactions of aryl halides [...] Read more.

Palladium nanoparticles have been electrochemically supported on zirconium oxide nanostructured powders and all the nanomaterials have been characterized by several analytical techniques. The Pd/ZrO₂ nanocatalyst is demonstrated to be a very efficient catalyst in Heck, Ullmann, and Suzuki reactions of aryl halides in water. The catalyst efficiency is attributed to the stabilization of Pd nanophases provided by tetra(alkyl)- ammonium hydroxide, which behaves both as base and PTC (phase transfer catalyst) agent. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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426 KiB

Open AccessArticle

Acid-Catalysed Conversion of Saccharides into Furanic Aldehydes in the Presence of Three-Dimensional Mesoporous Al-TUD-1

by Sérgio Lima, Margarida M. Antunes, Auguste Fernandes, Martyn Pillinger, Maria Filipa Ribeiro and Anabela A. Valente

Molecules 2010, 15(6), 3863-3877; https://doi.org/10.3390/molecules15063863 - 28 May 2010

Cited by 80 | Viewed by 11719

Abstract

The one-pot acid-catalysed conversion of mono/di/polysaccharides (inulin, xylan, cellobiose, sucrose, glucose, fructose, xylose) into 2-furfuraldehyde (FUR) or 5-hydroxymethylfurfural (HMF) in the presence of aluminium-containing mesoporous TUD-1 (denoted as Al-TUD-1, Si/Al = 21), at 170 ºC was investigated. Xylose gave 60% FUR yield after [...] Read more.

The one-pot acid-catalysed conversion of mono/di/polysaccharides (inulin, xylan, cellobiose, sucrose, glucose, fructose, xylose) into 2-furfuraldehyde (FUR) or 5-hydroxymethylfurfural (HMF) in the presence of aluminium-containing mesoporous TUD-1 (denoted as Al-TUD-1, Si/Al = 21), at 170 ºC was investigated. Xylose gave 60% FUR yield after 6 h reaction; hexose-based mono/disaccharides gave less than 20% HMF yield; polysaccharides gave less than 20 wt % FUR or HMF yields after 6 h. For four consecutive 6 h batches of the xylose reaction in the presence of Al-TUD-1, the FUR yields achieved were similar, without significant changes in Si/Al ratio. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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1270 KiB

Open AccessArticle

Carbon-Carbon Cross Coupling Reactions in Ionic Liquids Catalysed by Palladium Metal Nanoparticles

by Martin H. G. Prechtl, Jackson D. Scholten and Jairton Dupont

Molecules 2010, 15(5), 3441-3461; https://doi.org/10.3390/molecules15053441 - 12 May 2010

Cited by 148 | Viewed by 15660

Abstract

A brief summary of selected pioneering and mechanistic contributions in the field of carbon-carbon cross-coupling reactions with palladium nanoparticles (Pd-NPs) in ionic liquids (ILs) is presented. Five exemplary model systems using the Pd-NPs/ILs approach are presented: Heck, Suzuki, Stille, Sonogashira and Ullmann reactions [...] Read more.

A brief summary of selected pioneering and mechanistic contributions in the field of carbon-carbon cross-coupling reactions with palladium nanoparticles (Pd-NPs) in ionic liquids (ILs) is presented. Five exemplary model systems using the Pd-NPs/ILs approach are presented: Heck, Suzuki, Stille, Sonogashira and Ullmann reactions which all have in common the use of ionic liquids as reaction media and the use of palladium nanoparticles as reservoir for the catalytically active palladium species. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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121 KiB

Open AccessArticle

A Recyclable Nanoparticle-Supported Rhodium Catalyst for Hydrogenation Reactions

by Maria Michela Dell’Anna, Vito Gallo, Piero Mastrorilli and Giuseppe Romanazzi

Molecules 2010, 15(5), 3311-3318; https://doi.org/10.3390/molecules15053311 - 5 May 2010

Cited by 34 | Viewed by 10605

Abstract

Catalytic hydrogenation under mild conditions of olefins, unsaturated aldeydes and ketones, nitriles and nitroarenes was investigated, using a supported rhodium complex obtained by copolymerization of Rh(cod)(aaema) [cod: 1,5-cyclooctadiene, aaema–: deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with acrylamides. In particular, the hydrogenation reaction of halonitroarenes [...] Read more.

Catalytic hydrogenation under mild conditions of olefins, unsaturated aldeydes and ketones, nitriles and nitroarenes was investigated, using a supported rhodium complex obtained by copolymerization of Rh(cod)(aaema) [cod: 1,5-cyclooctadiene, aaema–: deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with acrylamides. In particular, the hydrogenation reaction of halonitroarenes was carried out under 20 bar hydrogen pressure with ethanol as solvent at room temperature, in order to minimize hydro-dehalogenation. The yields in haloanilines ranged from 85% (bromoaniline) to 98% (chloroaniline). Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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737 KiB

Open AccessArticle

Catalytic Performance of Ceria Nanorods in Liquid-Phase Oxidations of Hydrocarbons with tert-Butyl Hydroperoxide

by Andreia G. Macedo, Sílvia E. M. Fernandes, Anabela A. Valente, Rute. A. S. Ferreira, Luís D. Carlos and João Rocha

Molecules 2010, 15(2), 747-765; https://doi.org/10.3390/molecules15020747 - 2 Feb 2010

Cited by 33 | Viewed by 10808

Abstract

The CeO₂ nanorods (CeNR) promote the oxidation of ethylbenzene (PhEt) and cyclohexene with t-BuOOH, at temperatures as low as 55 ºC. For both substrates the saturated C-H bonds are preferentially activated over the unsaturated ones. The catalyst seems fairly stable towards leaching [...] Read more.

The CeO₂ nanorods (CeNR) promote the oxidation of ethylbenzene (PhEt) and cyclohexene with t-BuOOH, at temperatures as low as 55 ºC. For both substrates the saturated C-H bonds are preferentially activated over the unsaturated ones. The catalyst seems fairly stable towards leaching phenomena. The liquid-phase oxidation catalysis may be associated with the Ce³⁺/Ce⁴⁺ inter-conversion in the one-electron redox processes mediating the formation of tert-butyl-(per)oxy radicals. CeNR is very effective in H₂O₂ disproportionation. Pre-treatment of CeNR with H₂O₂ or t-BuOOH prior to the catalytic reaction enhances the reaction rate of PhEt with t-BuOOH in comparison to CeNR. Textural characterization and spectroscopic studies suggest that catalytic activation is associated to defect sites. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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Review

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632 KiB

Open AccessReview

Extremely Efficient Catalysis of Carbon-Carbon Bond Formation Using "Click" Dendrimer-Stabilized Palladium Nanoparticles

by Didier Astruc, Cátia Ornelas, Abdou K. Diallo and Jaime Ruiz

Molecules 2010, 15(7), 4947-4960; https://doi.org/10.3390/molecules15074947 - 20 Jul 2010

Cited by 32 | Viewed by 10765

Abstract

This article is an account of the work carried out in the authors’ laboratory illustrating the usefulness of dendrimer design for nanoparticle palladium catalysis. The “click” synthesis of dendrimers constructed generation by generation by 1à3 C connectivity, introduces 1,2,3-triazolyl ligands insides the dendrimers [...] Read more.

This article is an account of the work carried out in the authors’ laboratory illustrating the usefulness of dendrimer design for nanoparticle palladium catalysis. The “click” synthesis of dendrimers constructed generation by generation by 1à3 C connectivity, introduces 1,2,3-triazolyl ligands insides the dendrimers at each generation. Complexation of the ligands by Pd^II followed by reduction to Pd⁰ forms dendrimer-stabilized Pd nanoparticles (PdNPs) that are extremely reactive in the catalysis of olefin hydrogenation and C-C bond coupling reactions. The stabilization can be outer-dendritic for the small zeroth-generation dendrimer or intra-dendritic for the larger first- and second-generation dendrimers. The example of the Miyaura-Suzuki reaction that can be catalyzed by down to 1 ppm of PdNPs with a “homeopathic” mechanism (the less, the better) is illustrated here, including catalysis in aqueous solvents. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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882 KiB

Open AccessReview

Recyclable Nanostructured Catalytic Systems in Modern Environmentally Friendly Organic Synthesis

by Irina Beletskaya and Vladimir Tyurin

Molecules 2010, 15(7), 4792-4814; https://doi.org/10.3390/molecules15074792 - 8 Jul 2010

Cited by 56 | Viewed by 11156

Abstract

Modern chemical synthesis makes heavy use of different types of catalytic systems: homogeneous, heterogeneous and nano-sized. The latter – nano-sized catalysts – have given rise in the 21st century to a rapidly developing area of research encompassing several prospects and opportunities for new [...] Read more.

Modern chemical synthesis makes heavy use of different types of catalytic systems: homogeneous, heterogeneous and nano-sized. The latter – nano-sized catalysts – have given rise in the 21st century to a rapidly developing area of research encompassing several prospects and opportunities for new technologies. Catalytic reactions ensure high regio- and stereoselectivity of chemical transformations, as well as better yields and milder reaction conditions. In recent years several novel catalytic systems were developed for selective formation of carbon-heteroatom and carbon-carbon bonds. This review presents the achievements of our team in our studies on various types of catalysts containing metal nanoparticles: palladium-containing diblock copolymer micelles; soluble palladium-containing polymers; metallides on a support; polymeric metal salts and oxides; and, in addition, metal-free organic catalysts based on soluble polymers acting as nanoreactors. Representative examples are given and discussed in light of possible applications to solve important problems in modern organic synthesis. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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1245 KiB

Open AccessReview

Recent Advances in Noble Metal Nanocatalysts for Suzuki and Heck Cross-Coupling Reactions

by Radha Narayanan

Molecules 2010, 15(4), 2124-2138; https://doi.org/10.3390/molecules15042124 - 25 Mar 2010

Cited by 161 | Viewed by 13341

Abstract

Since metal nanoparticles have a high surface-to-volume ratio and very active surface atoms, they are very attractive catalysts for a wide variety of organic and inorganic reactions, compared to bulk catalysts. Metal nanoparticles suspended in colloidal solutions and those adsorbed onto bulk supports [...] Read more.

Since metal nanoparticles have a high surface-to-volume ratio and very active surface atoms, they are very attractive catalysts for a wide variety of organic and inorganic reactions, compared to bulk catalysts. Metal nanoparticles suspended in colloidal solutions and those adsorbed onto bulk supports have been used as catalysts for a wide variety of carbon-carbon bond formation reactions such as the Suzuki and Heck cross-coupling reactions. This review article highlights some of the latest advances in the application of noble metal nanoparticles as catalysts for these two industrially important classes of cross-coupling reactions. We will discuss several important advances in using metal nanocatalysts in Suzuki and Heck cross-coupling reactions such as investigations on the nanoparticle shape dependence on the catalytic activity, novel types of supported metal nanoparticles as nanocatalysts, and the use of bi-metallic, tri-metallic and multi-metallic nanoparticles as catalysts for the Suzuki and Heck cross-coupling reactions. Full article

(This article belongs to the Special Issue Nano-catalysts and Nano-technologies for Green Organic Synthesis)

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