Hybrid films of reduced graphene oxide with noble metal nanoparticles generated at a liquid/liquid interface for applications in catalysis

Abstract

Free-standing ultra-thin hybrid films of reduced graphene oxide (rGO) with Au, Ag and Pd nanoparticles are generated at an aqueous/organic interface by in situ chemical reduction and spontaneous assembly.The reduction is initiated at a 'bare' interface or a 'modified' interface in a single step or two-step synthetic strategy. The hybrid materials are characterized by UV-visible, infra-red and Raman spectroscopies, X-ray diffraction, scanning electron (SEM), transmission electron (TEM) and atomic force microscopies (AFM). UVvisible spectra confirm the presence of isolated metal nanoparticles grafted on to rGO layers and Raman spectra signal a charge transfer across the constituent metal nanoparticles and rGO in the hybrid material.SEM and AFM studies show that the morphology of the hybrid films constitutes a homogeneous dispersion of metal nanoparticles and rGO for reduction at the 'bare' interface, and a random grafting of metal nanoparticles on rGO for reduction at the 'modified' interface. A mechanism for the formation of the films is proposed that involves a simultaneous transport and reduction of GO sheets and metal precursor at the interface or a directed reduction of metal precursor on rGO surface, facilitated by external aids. The utility of these hybrid films as catalysts is exemplified in p-nitrophenol reduction. Our method provides a fast, simple and inexpensive route to obtain free-standing hybrid films of rGO with metal nanoparticles for various applications.

Assembly of Nanoscale Objects at the Liquid/Liquid Interface

“…100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 26 the stirring or sonication procedure required to assemble the structure at the liquid/liquid interface or, alternatively, as a two-step process whereby the rGO film is formed at the interface prior to metal reduction. 101,102 The one step process was shown to produce a higher surface coverage. 102 rGO may be formed from GO by the same reducing reagent used to generate the metal nanoparticles in solution.…”

Preparation of low-dimensional carbon material-based metal nanocomposites using a polarizable organic/water interface

“…28 Furthermore, the employment of easily processable, liquid-phase exfoliated, reduced graphene oxide (rGO) materials to support deposition of noble metals at the organic/water interface has been widely investigated, mainly to prepare GR-based catalysts or electrode materials on solid substrates. 3,6,22,24,[29][30][31][32] The use of CVD GR offers a macroscopic material-visible to the naked eye-that has not been deliberately oxidized and consists of a high-quality, well-defined monolayer, as opposed to liquid-phase exfoliated rGO aggregates. 27 Functionalization of a free-standing CVD GR monolayer with noble metal (Au, Pt, Pd) nanoparticles, using a low-cost, two-step, solution chemistrybased process has been reported previously.…”

Controlled preparation of carbon nanotube-conducting polymer composites at the polarisable organic/water interface

“…The interfacial polymerisation of polypyrrole (PPy) and polyaniline (PANI) at the non-polarised, chloroform/water interface using ferric chloride (FeCl 3 ) as oxidant was reported in 2008 [28], and thereafter several papers described preparation of CPs at the liquid/liquid interface [29][30][31][32][33]. Numerous studies have also reported the formation of adsorbed carbon nanomaterial films via self-assembly, such as CNTs, and adsorbed films of few-layer GR or reduced graphene-oxide (rGO) at non-polarised, liquid/liquid interfaces, often with the specific aim of preparing transparent or modified carbon-coated electrode materials [34][35][36][37]. Recently we have extended this approach to the localisation and moreover the functionalisation of CVD GR at the ITIES [38,39].…”