Abstract
Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III) to Au (0). In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III) by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III) to Mb in solution. X-ray photoelectron spectroscopy (XPS), fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR) spectra suggest that Mb molecules catalytically reduce Au (III) to Au (0) with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM) images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.
Highlights
Gold nanoparticles have received considerable attention during the past few decades because of their excellent functions in catalysis, biosensing, drug delivery and photonics [1,2]
We report the biosynthesis of monodispersed gold nanoparticles using Mb as the catalyst and stable agent without the need for any additive for protecting nanoparticles from aggregation
Under the conditions employed in the synthesis, it is clear that hydroquinone is unable to reduce Au (III) ions to gold nanoparticle by itself
Summary
Gold nanoparticles have received considerable attention during the past few decades because of their excellent functions in catalysis, biosensing, drug delivery and photonics [1,2]. Synthesis of gold nanoparticles with homogeneous sizes and shapes has enormous importance in nanotechnology, because of their size-dependent optical, magnetic, electronic and catalytic properties [3,4]. Various physical and chemical methods have been developed for nanoparticle synthesis, the major challenge remains of obtaining monodispersed nanoparticles with a narrow size distribution [5]. The nanoparticles are often observed to have polydispersity and a broad size distribution [6]. The most accepted size-controlled synthesis of nanoparticles is carried out by a two-step process, i.e., nucleation and successive growth of the seed particles.
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