De Novo Synthesis of Gold‐Nanoparticle‐Embedded, Nitrogen‐Doped Nanoporous Carbon Nanoparticles (Au@NC) with Enhanced Reduction Ability

Abstract

A de novo synthesis of gold nanoparticles embedded, nitrogen doped nanoporous carbon nanoparticles (Au@NC) was synthesized in this work. The chloroauroic acid was encapsulated inside zeolitic imidazolate framework-8 (ZIF-8) nanoparticles during the synthesis and later reduced into gold nanoparticles. The as-synthesized gold nanoparticles embedded ZIF-8 (Au@ZIF-8) was then carbonized into Au@NC to enhance the stability of the nanoporous support. The results showed that Au@NC exhibited a porous structure containing 3wt% of gold. 2-Methylimidazole provided abundant nitrogen (19wt%) on the carbon matrix, resulting in hydrophilic and positive charge surface that is useful for the reduction of 4-nitrophenol. The results of the catalytic reaction indicated that the synthesized Au@NC could act as an effective catalyst with turnover frequency (TOF) of 1185 g -1 s -1 , which is higher than that of conventional naked Au nanoparticles (TOF of 339 g -1 s -1 ) and Au nanoparticles on activated carbon (TOF of 89 g -1 s -1 ). We propose that the enhanced performance of the Au@NC resulted from the homogeneous distribution of Au nanoparticles along with the hydrophilic and positive charge surface of nitrogen-doped carbon surface.Catalysis has been involved at the core of nearly all chemical protocols from scientific research to industrial applications. In general, catalysis could be divided into homogeneous and heterogeneous catalysis. Both of homogenous and heterogeneous catalysts have their own advantages and drawbacks. [1] Some homogeneous catalysts have been tried to converted into hetrogeneous catalysts for easy recycling and other advantages. [2] In recent years, not only organic functional groups but also organometallic compounds and metallic nanoparticles have been decorated on different supports to change homogeneous catalyst into heterogeneous catalyst. [3] Mesoporous silica and zeolite are common supports for metal nanoparticles and organic functional groups since silica displays excellent chemical and thermal stability, extreme accessibility, high surface area, and easy functionalization. [4] As an example of such a recent development, Castro and co-workers functionalized ionic liquids on MCM-41 type mesoporous silica, which exhibited enhanced dodecene conversion efficacy as compared to that of the corresponding pure ionic liquids (i.e., 95% vs. 5%). [5] In addition to silica-based supports, metal oxides such as titania, magnesium oxide, and cerium oxide have also been utilized as effective supports for loading metal nanoparticles. [6] Metal oxides are utilized due to the capability for oxygen vacancies in the oxides to reduce the activation energy of catalytic reactions. [7] Other than silica and metal oxides, catalytic supports of carbon-based materials including activated carbon, mesoporous carbon, and graphite have also been widely used owing to their high stability towards acidic or basic environments. [8] Moreover, another advantage of carbon-based supports is the possible interactions between the catalytically ...

Sputtering onto a liquid: interesting physical preparation method for multi-metallic nanoparticles

“…Introducing reactive gas and sputter systems, which allow manipulation of energies and chemical state of the sputtered atoms/clusters, for doping multiple metal NPs and for synthesizing desired compounds and structures can be also considered for sputtering onto liquids towards advanced nanomaterials. Regarding production of metal, metal alloy and hybrid nanoparticles with wide variety of morphologies, higher ordered structure, doping and functionalization, we have demonstrated that our solution synthesis approaches based on chemical reduction, plasma in liquid process and stabilizing agents are very versatile [120][121][122][123][124][125][126] though in many cases toxic chemicals and by-products are present as they are also expected in other reports. Hence, we encourage and welcome other researchers join investigating this new vacuum sputtering onto liquid method, take all of its great advantages as the green technique for pure nanoparticles and unexpected structures, as well as devote new ideas for achieving more versatile control of the sputtered NPs.…”

Strategies for Improving the Functionality of Zeolitic Imidazolate Frameworks: Tailoring Nanoarchitectures for Functional Applications

“…In the former case, small and naked NPs are typically embedded in the cavities, however, in the case of encapsulation, usually pre‐synthesized NPs are stabilized with surfactants or capping agents and hydrodynamic radius of the NPs is much larger than the cavity size of the ZIFs. Very recently, another approach by directly adding metal ions in the synthetic systems has been reported . After encapsulation of the metal ions inside the ZIFs, a reduction process is carried out so that metal ions would be reduced to metal NPs that stay inside the ZIFs.…”

Gold nanoparticles stabilized by modified halloysite nanotubes for catalytic applications

“…To evaluate the catalytic performance of the HNT@Au hybrid nanomaterial obtained, we chose the reduction of 4‐NP by NaBH 4 , which is the most used reaction to investigate the catalytic activity of metal nanoparticles in aqueous solution . The interest in this reaction is mainly due to the fact that 4‐NP is a common reactant in pharmaceuticals and can be a hazardous by‐product that is inhibitory and toxic in nature; the product of the reaction, 4‐aminophenol (4‐AP), is used for black‐and‐white films and for the production of acetaminophen.…”